Science.gov

Sample records for acoustic harmonic generation

  1. Acoustic harmonic generation from fatigue-generated dislocation substructures in copper single crystals

    NASA Astrophysics Data System (ADS)

    Apple, T. M.; Cantrell, J. H.; Amaro, C. M.; Mayer, C. R.; Yost, W. T.; Agnew, S. R.; Howe, J. M.

    2013-07-01

    Dislocations generated during cyclic loading of metals self-organize into substructures that produce substantial changes in the nonlinear response. The nonlinearity is quantified by the material nonlinearity parameter ? extracted from acoustic harmonic generation measurements. Measurements of ? on copper single crystals oriented for single-slip ([1 2 3] loading axis) and fatigued in plastic strain control are compared to calculations of ? obtained from the Cantrell model for which measured values of model parameters associated with the substructures are required. Transmission electron microscopy measurements of the volume fractions of veins and persistent slip bands, dislocation loop lengths, dipole heights and the densities of primary and secondary dislocations in the fatigue-generated substructures are obtained for input into the model calculations. The model predictions agree with the values observed experimentally. In particular, the experimental data show an increase in ? proportional to ? where ? is the cumulative plastic strain and m is 0.7 and 0.4, respectively, for acoustic wave propagation along the ? and ? crystal axes. Such dependence is consistent with the Cantrell model and at variance with models, based on assumed variations in the third-order elastic constants, which predict an exponential dependence on ? .

  2. Temperature dependence of acoustic harmonics generated by nonlinear ultrasound wave propagation in water at various frequencies.

    PubMed

    Maraghechi, Borna; Hasani, Mojtaba H; Kolios, Michael C; Tavakkoli, Jahan

    2016-05-01

    Ultrasound-based thermometry requires a temperature-sensitive acoustic parameter that can be used to estimate the temperature by tracking changes in that parameter during heating. The objective of this study is to investigate the temperature dependence of acoustic harmonics generated by nonlinear ultrasound wave propagation in water at various pulse transmit frequencies from 1 to 20 MHz. Simulations were conducted using an expanded form of the Khokhlov-Zabolotskaya-Kuznetsov nonlinear acoustic wave propagation model in which temperature dependence of the medium parameters was included. Measurements were performed using single-element transducers at two different transmit frequencies of 3.3 and 13 MHz which are within the range of frequencies simulated. The acoustic pressure signals were measured by a calibrated needle hydrophone along the axes of the transducers. The water temperature was uniformly increased from 26 °C to 46 °C in increments of 5 °C. The results show that the temperature dependence of the harmonic generation is different at various frequencies which is due to the interplay between the mechanisms of absorption, nonlinearity, and focusing gain. At the transmit frequencies of 1 and 3.3 MHz, the harmonic amplitudes decrease with increasing the temperature, while the opposite temperature dependence is observed at 13 and 20 MHz. PMID:27250143

  3. Second Harmonic Generation and Confined Acoustic Phonons in HighlyExcited Semiconductor Nanocrystals

    SciTech Connect

    Son, Dong Hee; Wittenberg, Joshua S.; Banin, Uri; Alivisatos, A.Paul

    2006-03-30

    The photo-induced enhancement of second harmonic generation, and the effect of nanocrystal shape and pump intensity on confined acoustic phonons in semiconductor nanocrystals, has been investigated with time-resolved scattering and absorption measurements. The second harmonic signal showed a sublinear increase of the second order susceptibility with respect to the pump pulse energy, indicating a reduction of the effective one-electron second-order nonlinearity with increasing electron-hole density in the nanocrystals. The coherent acoustic phonons in spherical and rod-shaped semiconductor nanocrystals were detected in a time-resolved absorption measurement. Both nanocrystal morphologies exhibited oscillatory modulation of the absorption cross section, the frequency of which corresponded to their coherent radial breathing modes. The amplitude of the oscillation also increased with the level of photoexcitation, suggesting an increase in the amplitude of the lattice displacement as well.

  4. Materials characterization using acoustic nonlinearity parameters and harmonic generation - Engineering materials

    NASA Technical Reports Server (NTRS)

    Yost, William T.; Cantrell, John H.

    1990-01-01

    The paper reviews nonlinear bulk compressional wave acoustic measurement systems and the applications of measurements from such systems to engineering materials. Preliminary measurements indicate that it is possible to determine percent second phase precipitates in aluminum alloys, while other measurements show promise in the determination of properties related to the fatigue states of metals. It is also shown that harmonic generation can be used for the study of crack opening loads in compact tension specimens, which in turn gives useful information about the fatigue properties of various engineering materials.

  5. Quantitative Assessment of Fatigue Damage Accumulation in Wavy Slip Metals from Acoustic Harmonic Generation

    NASA Technical Reports Server (NTRS)

    Cantrell, John H.

    2006-01-01

    A comprehensive, analytical treatment is presented of the microelastic-plastic nonlinearities resulting from the interaction of a stress perturbation with dislocation substructures (veins and persistent slip bands) and cracks that evolve during high-cycle fatigue of wavy slip metals. The nonlinear interaction is quantified by a material (acoustic) nonlinearity parameter beta extracted from acoustic harmonic generation measurements. The contribution to beta from the substructures is obtained from the analysis of Cantrell [Cantrell, J. H., 2004, Proc. R. Soc. London A, 460, 757]. The contribution to beta from cracks is obtained by applying the Paris law for crack propagation to the Nazarov-Sutin crack nonlinearity equation [Nazarov, V. E., and Sutin, A. M., 1997, J. Acoust. Soc. Am. 102, 3349]. The nonlinearity parameter resulting from the two contributions is predicted to increase monotonically by hundreds of percent during fatigue from the virgin state to fracture. The increase in beta during the first 80-90 percent of fatigue life is dominated by the evolution of dislocation substructures, while the last 10-20 percent is dominated by crack growth. The model is applied to the fatigue of aluminium alloy 2024-T4 in stress-controlled loading at 276MPa for which experimental data are reported. The agreement between theory and experiment is excellent.

  6. Higher harmonic generation microscopy.

    PubMed

    Sun, Chi-Kuang

    2005-01-01

    Higher harmonic-generation, including second harmonic generation and third harmonic generation, leaves no energy deposition to the interacted matters due to its virtual-level transition characteristic, providing a truly non-invasive modality and is ideal for in vivo imaging of live specimens without any preparation. Second harmonic generation microscopy provides images on stacked membranes and arranged proteins with organized nano-structures due to the bio-photonic crystalline effect. Third harmonic generation microscopy provides general cellular or subcellular interface imaging due to optical inhomogeneity. Due to their virtual-transition nature, no saturation or bleaching in the generated signal is expected. With no energy release, continuous viewing without compromising sample viability can thus be achieved. Combined with its nonlinearity, higher harmonic generation microscopy provides sub-micron three-dimensional sectioning capability and millimeter penetration in live samples without using fluorescence and exogenous markers, offering morphological, structural, functional, and cellular information of biomedical specimens without modifying their natural biological and optical environments.

  7. Optical harmonic generator

    DOEpatents

    Summers, Mark A.; Eimerl, David; Boyd, Robert D.

    1985-01-01

    A pair of uniaxial birefringent crystal elements are fixed together to form a serially arranged, integral assembly which, alternatively, provides either a linearly or elliptically polarized second-harmonic output wave or a linearly polarized third-harmonic output wave. The "extraordinary" or "e" directions of the crystal elements are oriented in the integral assembly to be in quadrature (90.degree.). For a second-harmonic generation in the Type-II-Type-II angle tuned case, the input fundamental wave has equal amplitude "o" and "e" components. For a third-harmonic generation, the input fundamental wave has "o" and "e" components whose amplitudes are in a ratio of 2:1 ("o":"e" reference first crystal). In the typical case of a linearly polarized input fundamental wave this can be accomplished by simply rotating the crystal assembly about the input beam direction by 10.degree.. For both second and third harmonic generation input precise phase-matching is achieved by tilting the crystal assembly about its two sensitive axes ("o").

  8. Optical harmonic generator

    DOEpatents

    Summers, M.A.; Eimerl, D.; Boyd, R.D.

    1982-06-10

    A pair of uniaxial birefringent crystal elements are fixed together to form a serially arranged, integral assembly which, alternatively, provides either a linearly or elliptically polarized second-harmonic output wave or a linearly polarized third-harmonic output wave. The extraordinary or e directions of the crystal elements are oriented in the integral assembly to be in quadrature (90/sup 0/). For a second-harmonic generation in the Type-II-Type-II angle tuned case, the input fundamental wave has equal amplitude o and e components. For a third-harmonic generation, the input fundamental wave has o and e components whose amplitudes are in a ratio of 2:1 (o:e reference first crystal). In the typical case of a linearly polarized input fundamental wave this can be accomplished by simply rotating the crystal assembly about the input beam direction by 10/sup 0/. For both second and third harmonic generation input precise phase-matching is achieved by tilting the crystal assembly about its two sensitive axeses (o).

  9. Echo-Enabled Harmonic Generation

    SciTech Connect

    Stupakov, Gennady; /SLAC

    2012-06-28

    A recently proposed concept of the Echo-Enabled Harmonic Generation (EEHG) FEL uses two laser modulators in combination with two dispersion sections to generate a high-harmonic density modulation in a relativistic beam. This seeding technique holds promise of a one-stage soft x-ray FEL that radiates not only transversely but also longitudinally coherent pulses. Currently, an experimental verification of the concept is being conducted at the SLAC National Accelerator Laboratory aimed at the demonstration of the EEHG.

  10. Echo-Enabled Harmonic Generation

    SciTech Connect

    Stupakov, Gennady

    2010-08-25

    A recently proposed concept of the Echo-Enabled Harmonic Generation (EEHG) FEL uses two laser modulators in combination with two dispersion sections to generate a high-harmonic density modulation in a relativistic beam. This seeding technique holds promise of a one-stage soft x-ray FEL that radiates not only transversely but also longitudinally coherent pulses. Currently, an experimental verification of the concept is being conducted at the SLAC National Accelerator Laboratory aimed at the demonstration of the EEHG.

  11. Limitations and improvements for harmonic generation measurements

    SciTech Connect

    Best, Steven; Croxford, Anthony; Neild, Simon

    2014-02-18

    A typical acoustic harmonic generation measurement comes with certain limitations. Firstly, the use of the plane wave-based analysis used to extract the nonlinear parameter, β, ignores the effects of diffraction, attenuation and receiver averaging which are common to most experiments, and may therefore limit the accuracy of a measurement. Secondly, the method usually requires data obtained from a through-transmission type setup, which may not be practical in a field measurement scenario where access to the component is limited. Thirdly, the technique lacks a means of pinpointing areas of damage in a component, as the measured nonlinearity represents an average over the length of signal propagation. Here we describe a three-dimensional model of harmonic generation in a sound beam, which is intended to provide a more realistic representation of a typical experiment. The presence of a reflecting boundary is then incorporated into the model to assess the feasibility of performing single-sided measurements. Experimental validation is provided where possible. Finally, a focusing acoustic source is modelled to provide a theoretical indication of the afforded advantages when the nonlinearity is localized.

  12. Acoustic source for generating an acoustic beam

    DOEpatents

    Vu, Cung Khac; Sinha, Dipen N.; Pantea, Cristian

    2016-05-31

    An acoustic source for generating an acoustic beam includes a housing; a plurality of spaced apart piezo-electric layers disposed within the housing; and a non-linear medium filling between the plurality of layers. Each of the plurality of piezoelectric layers is configured to generate an acoustic wave. The non-linear medium and the plurality of piezo-electric material layers have a matching impedance so as to enhance a transmission of the acoustic wave generated by each of plurality of layers through the remaining plurality of layers.

  13. Dislocation Detection Through Harmonic Generation

    NASA Astrophysics Data System (ADS)

    Reinhardt, B. T.; Kropf, M.; Boudraeu, K.; Guers, M. J.; Tittmann, B. R.

    2010-02-01

    A fundamental goal of ultrasonic nondestructive evaluation is to characterize material defects before failure. During material fatigue, dislocations tend to nucleate, becoming sources of stress concentration. Eventually, cracks start to form and lead to material failure. Recent research has indicated that nonlinear harmonic generation can be used to distinguish between materials of high and low dislocation densities. This research reports nonlinear harmonic generation measurements to distinguish between those areas of high and low dislocation densities in copper bars. The copper bars were subjected to flexural fatigue. Periodic scans were taken in order to track dislocation development during the fatigue life of the material. We show that this technique provides improved early detection for critical components of failure.

  14. Monitoring microstructural evolution in irradiated steel with second harmonic generation

    NASA Astrophysics Data System (ADS)

    Matlack, Kathryn H.; Kim, Jin-Yeon; Wall, James J.; Qu, Jianmin; Jacobs, Laurence J.

    2015-03-01

    Material damage in structural components is driven by microstructural evolution that occurs at low length scales and begins early in component life. In metals, these microstructural features are known to cause measurable changes in the acoustic nonlinearity parameter. Physically, the interaction of a monochromatic ultrasonic wave with microstructural features such as dislocations, precipitates, and vacancies, generates a second harmonic wave that is proportional to the acoustic nonlinearity parameter. These nonlinear ultrasonic techniques thus have the capability to evaluate initial material damage, particularly before crack initiation and propagation occur. This paper discusses how the nonlinear ultrasonic technique of second harmonic generation can be used as a nondestructive evaluation tool to monitor microstructural changes in steel, focusing on characterizing neutron radiation embrittlement in nuclear reactor pressure vessel steels. Current experimental evidence and analytical models linking microstructural evolution with changes in the acoustic nonlinearity parameter are summarized.

  15. Monitoring microstructural evolution in irradiated steel with second harmonic generation

    SciTech Connect

    Matlack, Kathryn H.; Kim, Jin-Yeon; Jacobs, Laurence J.; Wall, James J.; Qu, Jianmin

    2015-03-31

    Material damage in structural components is driven by microstructural evolution that occurs at low length scales and begins early in component life. In metals, these microstructural features are known to cause measurable changes in the acoustic nonlinearity parameter. Physically, the interaction of a monochromatic ultrasonic wave with microstructural features such as dislocations, precipitates, and vacancies, generates a second harmonic wave that is proportional to the acoustic nonlinearity parameter. These nonlinear ultrasonic techniques thus have the capability to evaluate initial material damage, particularly before crack initiation and propagation occur. This paper discusses how the nonlinear ultrasonic technique of second harmonic generation can be used as a nondestructive evaluation tool to monitor microstructural changes in steel, focusing on characterizing neutron radiation embrittlement in nuclear reactor pressure vessel steels. Current experimental evidence and analytical models linking microstructural evolution with changes in the acoustic nonlinearity parameter are summarized.

  16. Quasi-phase-matched backward second-harmonic generation by complementary media in nonlinear metamaterials.

    PubMed

    Quan, Li; Liu, Xiaozhou; Gong, Xiufen

    2012-10-01

    High efficiency of the second-harmonic and sum-frequency generation can be obtained in optical superlattice by using the conventional quasi-phase-matched (QPM) method. Although this trick can be played on the acoustic wave, the media with negative nonlinear parameters are not common in acoustics. Furthermore, the QPM method used in acoustic metamaterials has been less studied. In this work, a protocol is provided to realize the QPM method by using nonlinear complementary media in acoustic metamaterials in order to obtain large backward second-harmonic generation. Compared with the conventional method, the method gains a broader bandwidth and can be used in both acoustic and electromagnetic waves.

  17. Second harmonic acoustic responses induced in matter by quasi continuous radiofrequency fields

    NASA Astrophysics Data System (ADS)

    Kellnberger, Stephan; Omar, Murad; Sergiadis, George; Ntziachristos, Vasilis

    2013-10-01

    We subjected conductive matter and tissue to intermittent continuous-wave radiofrequency fields and investigated whether acoustic responses could be recorded. By placing samples in the near-field of the excitation, we observed frequency-domain acoustic responses from tissues responding to CW radiofrequency excitation. Frequency analysis revealed the generation of 2nd harmonic mechanical waves. This discovery of non-linear responses can lead to alternative measurement concepts of CW radiofrequency deposition in matter and tissues. We offer the theoretical mainframe and discuss sensing applications involving the direct measurement of second harmonic responses representative of CW RF energy deposition in matter.

  18. Organometallic Salts Generate Optical Second Harmonics

    NASA Technical Reports Server (NTRS)

    Marder, Seth R.; Perry, Joseph W.

    1991-01-01

    Series of organometallic salts exhibit large second-order dielectric susceptibilities, as evidenced by generation of second harmonics when illuminated at visible and near-infrared wavelengths. Investigations of these and related compounds continue with view toward development of materials for use as optical second-harmonic generators, electro-optical modulators, optical switches, piezoelectric sensors, and parametric crystals.

  19. Resonantly-enhanced harmonic generation in Argon.

    PubMed

    Ackermann, P; Münch, H; Halfmann, T

    2012-06-18

    We present systematic investigations of harmonic generation in Argon, driven in the vicinity of a five-photon resonance by intense, tunable picosecond radiation pulses. When properly matching the laser frequency with the Stark-shifted multi-photon resonance, we observe a pronounced enhancement not only of the 5th, but also the 7th and 9th harmonic of the driving laser (i.e. at orders higher than the involved multi-photon resonance). We study the harmonic yield at different intensities and wavelengths of the driving laser to determine optimal conditions for resonantly-enhanced harmonic generation.

  20. Harmonic generation in magnetized quantum plasma

    NASA Astrophysics Data System (ADS)

    Kumar, Punit; Singh, Shiv; Singh, Abhisek Kumar

    2016-05-01

    A study of second harmonic generation by propagation of a linearly polarized electromagnetic wave through homogeneous high density quantum plasma in the presence of transverse magnetic field. The nonlinear current density and dispersion relations for the fundamental and second harmonic frequencies have been obtained using the recently developed quantum hydrodynamic (QHD) model. The effect of quantum Bohm potential, Fermi pressure and the electron spin have been taken into account. The second harmonic is found to be less dispersed than the first.

  1. Surface-Enhanced Second-Harmonic Generation

    SciTech Connect

    Chen, C. K.; de Castro, A. R.B.; Shen, Y. R.

    1981-01-12

    Second harmonic generation at a silver-air interface was enhanced due to surface roughness by a factor of 10⁴. The local field enhancement is believed to be responsible for the effect. An unusually broad luminescence background extending far beyond the antiStokes side of the second harmonic was also observed.

  2. High order harmonic generation in rare gases

    SciTech Connect

    Budil, K.S.

    1994-05-01

    The process of high order harmonic generation in atomic gases has shown great promise as a method of generating extremely short wavelength radiation, extending far into the extreme ultraviolet (XUV). The process is conceptually simple. A very intense laser pulse (I {approximately}10{sup 13}-10{sup 14} W/cm{sup 2}) is focused into a dense ({approximately}10{sup l7} particles/cm{sup 3}) atomic medium, causing the atoms to become polarized. These atomic dipoles are then coherently driven by the laser field and begin to radiate at odd harmonics of the laser field. This dissertation is a study of both the physical mechanism of harmonic generation as well as its development as a source of coherent XUV radiation. Recently, a semiclassical theory has been proposed which provides a simple, intuitive description of harmonic generation. In this picture the process is treated in two steps. The atom ionizes via tunneling after which its classical motion in the laser field is studied. Electron trajectories which return to the vicinity of the nucleus may recombine and emit a harmonic photon, while those which do not return will ionize. An experiment was performed to test the validity of this model wherein the trajectory of the electron as it orbits the nucleus or ion core is perturbed by driving the process with elliptically, rather than linearly, polarized laser radiation. The semiclassical theory predicts a rapid turn-off of harmonic production as the ellipticity of the driving field is increased. This decrease in harmonic production is observed experimentally and a simple quantum mechanical theory is used to model the data. The second major focus of this work was on development of the harmonic {open_quotes}source{close_quotes}. A series of experiments were performed examining the spatial profiles of the harmonics. The quality of the spatial profile is crucial if the harmonics are to be used as the source for experiments, particularly if they must be refocused.

  3. High-harmonic generation in cavitated plasmas

    SciTech Connect

    Schroeder, C. B.; Esarey, E.; Comier-Michel, E.; Leemans, W. P.

    2008-05-15

    A method is proposed for producing coherent x-rays via high-harmonic generation using ultraintense lasers interacting with highly stripped ions in cavitated plasmas. This method relies on plasma cavitation by the wake of an intense drive beam (laser or electron beam) to produce an ion cavity. An ultrashort pulse laser propagating in the plasma-electron-free ion cavity generates laser harmonics. The longitudinal electron motion, which inhibits high-harmonic generation at high laser intensities, can be suppressed by the space-charge field in the ion cavity or by using a counterpropagating laser pulse. Periodic suppression of the longitudinal electron motion may also be used to quasi-phase-match. This method enables harmonic generation to be extended to the sub-A regime.

  4. Nonlinear harmonic generation in the STARS FEL

    NASA Astrophysics Data System (ADS)

    Abo-Bakr, M.; Goldammer, K.; Kamps, T.; Knobloch, J.; Kuske, B.; Leitner, T.; Meseck, A.

    2008-08-01

    BESSY proposes to build STARS, an FEL to demonstrate cascaded High Gain Harmonic Generation (HGHG). In two HGHG stages, a laser source of 700-900 nm is converted down to a wavelength of 40-70 nm. The STARS facility consists of a normal-conducting RF photoinjector, three superconducting TESLA-type acceleration modules, a magnetic bunch compressor and two stages of HGHG, each consisting of a modulator, dispersive chicane and a radiator. At the entrance of the undulator section, the beam energy is 325 MeV and the peak current is about 500 A. With these parameters, the STARS FEL reaches saturation with a peak power of 100-350 MW. A superradiant mode is also foreseen which boosts the radiation power to the GW-level. Due to nonlinear harmonic generation (NHG), free electron lasers also radiate coherently at higher harmonics of the FEL resonant frequency. STARS can hence extend its output range to even shorter wavelengths. This paper presents studies of the STARS harmonic content in the wavelength range of 6-20 nm. Seeding with high harmonic generation pulses at 32 nm is also discussed.

  5. Microwave harmonic generation and nonlinearity in microplasmas

    NASA Astrophysics Data System (ADS)

    Gregório, José; Parsons, Stephen; Hopwood, Jeffrey

    2016-06-01

    Nonlinearities in microplasmas excited by microwaves are described both experimentally and through a 2D fluid model. A split-ring resonator generates a microplasma in a 150 μm discharge gap at 1 GHz. Nonlinearity generates both radiated and conducted harmonics which are measured from 0.2–760 Torr (Ar) for power levels between 0.5 and 3 W. Asymmetric electrode configurations produce the highest 3rd harmonic power (>10 mW) at an optimal pressure of the order of 0.3 Torr. The microplasma is also demonstrated as a mixer. The experimental results are explained with the aid of a fluid model of the microplasma. The model shows that the smaller electrode in an asymmetric device is forced to attain a large microwave potential that strongly modulates the sheath thickness and the local electron energy. The voltage-dependent sheath width gives rises to a nonlinear sheath capacitance as well as short pulses of hot electron flux to the electrode. The modeled 3rd harmonic current is converted to an extractable harmonic power by a microwave circuit model. Using this technique the modeled and measured harmonic production of the microplasma are found to compare favorably.

  6. Harmonic generation with multiple wiggler schemes

    SciTech Connect

    Bonifacio, R.; De Salvo, L.; Pierini, P.

    1995-02-01

    In this paper the authors give a simple theoretical description of the basic physics of the single pass high gain free electron laser (FEL), describing in some detail the FEL bunching properties and the harmonic generation technique with a multiple-wiggler scheme or a high gain optical klystron configuration.

  7. The Acoustic Simple Harmonic Oscillator: Experimental Verification and Applications

    NASA Astrophysics Data System (ADS)

    Matteson, Sam

    2009-04-01

    In his famous volume, The Sensations of Tone, published in 1877, Hermann Helmholtz introduced a resonator that was central to his investigations of acoustics. This talk revisits the device that Helmholtz described and examines it as a manifestation of an acoustic simple harmonic oscillator (SHO). The presentation demonstrates that an enclosed volume which communicates with the outside world via a narrow tube exhibits a single strong frequency response in analogy to a mechanical SHO, along with weaker resonances of the air in the short pipe that comprises the ``neck.'' The investigations, furthermore, report results of a straightforward experiment that confirms the SHO model (with damping) and that is very accessible to undergraduate students using inexpensive equipment and internet-obtainable freeware. The current work also extends the analysis to include applications of the Helmholtz Resonator to several folk instruments, namely, the ocarina, whistling, and the ``bottle band.''

  8. Nonlinear harmonic generation in distributed optical klystrons

    SciTech Connect

    H.P. Freund; George R. Neil

    2001-12-01

    A distributed optical klystron has the potential for dramatically shortening the total interaction length in high-gain free-electron lasers (INP 77-59, Novosibirsk, 1977; Nucl. Instr. and Meth A 304 (1991) 463) in comparison to a single-wiggler-segment configuration. This shortening can be even more dramatic if a nonlinear harmonic generation mechanism is used to reach the desired wavelength. An example operating at a 4.5{angstrom} fundamental and a 1.5{angstrom} harmonic is discussed.

  9. Second Harmonic Generation of Nanoscale Phonon Wave Packets

    NASA Astrophysics Data System (ADS)

    Bojahr, A.; Gohlke, M.; Leitenberger, W.; Pudell, J.; Reinhardt, M.; von Reppert, A.; Roessle, M.; Sander, M.; Gaal, P.; Bargheer, M.

    2015-11-01

    Phonons are often regarded as delocalized quasiparticles with certain energy and momentum. The anharmonic interaction of phonons determines macroscopic properties of the solid, such as thermal expansion or thermal conductivity, and a detailed understanding becomes increasingly important for functional nanostructures. Although phonon-phonon scattering processes depicted in simple wave-vector diagrams are the basis of theories describing these macroscopic phenomena, experiments directly accessing these coupling channels are scarce. We synthesize monochromatic acoustic phonon wave packets with only a few cycles to introduce nonlinear phononics as the acoustic counterpart to nonlinear optics. Control of the wave vector, bandwidth, and consequently spatial extent of the phonon wave packets allows us to observe nonlinear phonon interaction, in particular, second harmonic generation, in real time by wave-vector-sensitive Brillouin scattering with x-rays and optical photons.

  10. Inhomogeneous high harmonic generation in krypton clusters.

    PubMed

    Ruf, H; Handschin, C; Cireasa, R; Thiré, N; Ferré, A; Petit, S; Descamps, D; Mével, E; Constant, E; Blanchet, V; Fabre, B; Mairesse, Y

    2013-02-22

    High order harmonic generation from clusters is a controversial topic: conflicting theories exist, with different explanations for similar experimental observations. From an experimental point of view, separating the contributions from monomers and clusters is challenging. By performing a spectrally and spatially resolved study in a controlled mixture of clusters and monomers, we are able to isolate a region of the spectrum where the emission purely originates from clusters. Surprisingly, the emission from clusters is depolarized, which is the signature of statistical inhomogeneous emission from a low-density source. The harmonic response to laser ellipticity shows that this generation is produced by a new recollisional mechanism, which opens the way to future theoretical studies.

  11. Fast interferometric second harmonic generation microscopy

    PubMed Central

    Bancelin, Stéphane; Couture, Charles-André; Légaré, Katherine; Pinsard, Maxime; Rivard, Maxime; Brown, Cameron; Légaré, François

    2016-01-01

    We report the implementation of fast Interferometric Second Harmonic Generation (I-SHG) microscopy to study the polarity of non-centrosymmetric structures in biological tissues. Using a sample quartz plate, we calibrate the spatially varying phase shift introduced by the laser scanning system. Compensating this phase shift allows us to retrieve the correct phase distribution in periodically poled lithium niobate, used as a model sample. Finally, we used fast interferometric second harmonic generation microscopy to acquire phase images in tendon. Our results show that the method exposed here, using a laser scanning system, allows to recover the polarity of collagen fibrils, similarly to standard I-SHG (using a sample scanning system), but with an imaging time about 40 times shorter. PMID:26977349

  12. High-order harmonic generation in alkanes

    SciTech Connect

    Altucci, C.; Velotta, R.; Heesel, E.; Springate, E.; Marangos, J. P.; Vozzi, C.; Benedetti, E.; Calegari, F.; Sansone, G.; Stagira, S.; Nisoli, M.; Tosa, V.

    2006-04-15

    We have investigated the process of high-order harmonic generation in light alkanes by using femtosecond laser pulses. We show the experimental results cannot be matched by a model that assumes a single active electron only in a hydrogenic s orbital. Clear evidences are shown of the important role played by the p-like character originating from the covalent C-H bond. By constructing a suitable mixture of s-type and p-type atomic wave functions, an excellent agreement between measurements in methane and simulations is found, thus confirming the validity of the developed method as a general tool for the analysis of high-order harmonic generation in complex molecules.

  13. Generating Second Harmonics In Nonlinear Resonant Cavities

    NASA Technical Reports Server (NTRS)

    Kozlovsky, William J.; Nabors, C. David; Byer, Robert L.

    1990-01-01

    Single-axial-mode lasers pump very-low-loss doubling crystals. Important advance in making resonant generation of second harmonics possible for diode-laser-pumped solid-state lasers is recent development of monolithic nonplanar ring geometries in neodymium:yttrium aluminum garnet (Nd:YAG) lasers that produce frequency-stable single-mode outputs. Other advance is development of high-quality MgO:LiNbO3 as electro-optically nonlinear material. Series of experiments devised to improve doubling efficiency of low-power lasers, and particularly of diode-laser-pumped continuous-wave Nd:YAG lasers.

  14. High harmonic generation in undulators for FEL

    NASA Astrophysics Data System (ADS)

    Zhukovsky, K.

    2016-02-01

    The analytical study of the undulator radiation (UR), accounting for major sources of the spectral line broadening is presented. Analytical expressions for the UR spectrum and intensity are obtained. They demonstrate possibilities of the compensation of the divergency by the constant magnetic component. Some examples of single and double frequency undulators are considered. Generation of harmonics is studied with account for homogeneous and inhomogeneous broadening in real devices. The obtained results with account for all broadening sources are applied for evaluation of free electron laser (FEL) performance and compared with those, obtained with the ideal undulator.

  15. Promoting Spontaneous Second Harmonic Generation through Organogelation.

    PubMed

    Marco, A Belén; Aparicio, Fátima; Faour, Lara; Iliopoulos, Konstantinos; Morille, Yohann; Allain, Magali; Franco, Santiago; Andreu, Raquel; Sahraoui, Bouchta; Gindre, Denis; Canevet, David; Sallé, Marc

    2016-07-27

    An organogelator based on the Disperse Red nonlinear optical chromophore was synthesized according to a simple and efficient three-step procedure. The supramolecular gel organization leads to xerogels which display a spontaneous second harmonic generation (SHG) response without any need for preprocessing, and this SHG activity appears to be stable over several months. These findings, based on an intrinsic structural approach, are supported by favorable intermolecular supramolecular interactions, which promote a locally non-centrosymmetric NLO-active organization. This is in sharp contrast with most materials designed for SHG purposes, which generally require the use of expensive or heavy-to-handle external techniques for managing the dipoles' alignment. PMID:27415660

  16. Orientation dependence of high-order harmonic generation in molecules

    NASA Astrophysics Data System (ADS)

    Lein, M.; Corso, P. P.; Marangos, J. P.; Knight, P. L.

    2003-02-01

    We present two- and three-dimensional model calculations of high-order harmonic generation in H+2. The harmonic spectra exhibit clear signatures of intramolecular interference. An interference minimum appears at a harmonic order that depends on the molecular orientation. Harmonic generation in three-center molecules is studied on the basis of two-dimensional calculations for a H2+3 model system. From analytical considerations, the orientation dependence of the harmonic intensities in three-center molecules exhibits a double minimum due to intramolecular interference. In the numerical results, the double minimum is broadened into a single wide minimum. The effect of nonzero laser ellipticity on harmonic generation is investigated by means of two-dimensional simulations for H+2. We find that harmonic generation with elliptical polarization is governed by interference effects similar to linear polarization.

  17. Modelling harmonic generation measurements in solids.

    PubMed

    Best, S R; Croxford, A J; Neild, S A

    2014-02-01

    Harmonic generation measurements typically make use of the plane wave result when extracting values for the nonlinearity parameter, β, from experimental measurements. This approach, however, ignores the effects of diffraction, attenuation, and receiver integration which are common features in a typical experiment. Our aim is to determine the importance of these effects when making measurements of β over different sample dimensions, or using different input frequencies. We describe a three-dimensional numerical model designed to accurately predict the results of a typical experiment, based on a quasi-linear assumption. An experiment is designed to measure the axial variation of the fundamental and second harmonic amplitude components in an ultrasonic beam, and the results are compared with those predicted by the model. The absolute β values are then extracted from the experimental data using both the simulation and the standard plane wave result. A difference is observed between the values returned by the two methods, which varies with axial range and input frequency. PMID:23786784

  18. Experimental observation of acoustic sub-harmonic diffraction by a grating

    SciTech Connect

    Liu, Jingfei Declercq, Nico F.

    2014-06-28

    A diffraction grating is a spatial filter causing sound waves or optical waves to reflect in directions determined by the frequency of the waves and the period of the grating. The classical grating equation is the governing principle that has successfully described the diffraction phenomena caused by gratings. However, in this work, we show experimental observation of the so-called sub-harmonic diffraction in acoustics that cannot be explained by the classical grating equation. Experiments indicate two physical phenomena causing the effect: internal scattering effects within the corrugation causing a phase shift and nonlinear acoustic effects generating new frequencies. This discovery expands our current understanding of the diffraction phenomenon, and it also makes it possible to better design spatial diffraction spectra, such as a rainbow effect in optics with a more complicated color spectrum than a traditional rainbow. The discovery reveals also a possibly new technique to study nonlinear acoustics by exploitation of the natural spatial filtering effect inherent to an acoustic diffraction grating.

  19. Experimental observation of acoustic sub-harmonic diffraction by a grating

    NASA Astrophysics Data System (ADS)

    Liu, Jingfei; Declercq, Nico F.

    2014-06-01

    A diffraction grating is a spatial filter causing sound waves or optical waves to reflect in directions determined by the frequency of the waves and the period of the grating. The classical grating equation is the governing principle that has successfully described the diffraction phenomena caused by gratings. However, in this work, we show experimental observation of the so-called sub-harmonic diffraction in acoustics that cannot be explained by the classical grating equation. Experiments indicate two physical phenomena causing the effect: internal scattering effects within the corrugation causing a phase shift and nonlinear acoustic effects generating new frequencies. This discovery expands our current understanding of the diffraction phenomenon, and it also makes it possible to better design spatial diffraction spectra, such as a rainbow effect in optics with a more complicated color spectrum than a traditional rainbow. The discovery reveals also a possibly new technique to study nonlinear acoustics by exploitation of the natural spatial filtering effect inherent to an acoustic diffraction grating.

  20. Harmonic generation by circularly polarized laser beams propagating in plasma

    SciTech Connect

    Agrawal, Ekta; Hemlata,; Jha, Pallavi

    2015-04-15

    An analytical theory is developed for studying the phenomenon of generation of harmonics by the propagation of an obliquely incident, circularly polarized laser beam in homogeneous, underdense plasma. The amplitudes of second and third harmonic radiation as well as detuning distance have been obtained and their variation with the angle of incidence is analyzed. The amplitude of harmonic radiation increases with the angle of incidence while the detuning distance decreases, for a given plasma electron density. It is observed that the generated second and third harmonic radiation is linearly and elliptically polarized, respectively. The harmonic radiation vanishes at normal incidence of the circularly polarized laser beam.

  1. Goos-Hänchen shifts in harmonic generation from metals.

    PubMed

    Yallapragada, V J; Gopal, Achanta Venu; Agarwal, G S

    2013-05-01

    We present the first calculation of the Goos-Hänchen shifts in the context of the nonlinear generation of fields. We specifically concentrate on shifts of second harmonic generated at metallic surfaces. At metallic surfaces the second harmonic primarily arises from discontinuities of the field at surfaces which not only result in large harmonic generation but also in significant Goos-Hänchen shifts of the generated second harmonic. Our results can be extended to other shifts like angular shifts and Fedorov-Imbert shifts.

  2. Acoustic waves in the atmosphere and ground generated by volcanic activity

    SciTech Connect

    Ichihara, Mie; Lyons, John; Oikawa, Jun; Takeo, Minoru

    2012-09-04

    This paper reports an interesting sequence of harmonic tremor observed in the 2011 eruption of Shinmoe-dake volcano, southern Japan. The main eruptive activity started with ashcloud forming explosive eruptions, followed by lava effusion. Harmonic tremor was transmitted into the ground and observed as seismic waves at the last stage of the effusive eruption. The tremor observed at this stage had unclear and fluctuating harmonic modes. In the atmosphere, on the other hand, many impulsive acoustic waves indicating small surface explosions were observed. When the effusion stopped and the erupted lava began explosive degassing, harmonic tremor started to be transmitted also to the atmosphere and observed as acoustic waves. Then the harmonic modes became clearer and more stable. This sequence of harmonic tremor is interpreted as a process in which volcanic degassing generates an open connection between the volcanic conduit and the atmosphere. In order to test this hypothesis, a laboratory experiment was performed and the essential features were successfully reproduced.

  3. Generation mechanism of power line harmonic radiation

    NASA Astrophysics Data System (ADS)

    Kostrov, Alexander; Gushchin, Mikhail; Korobkov, Sergei

    The questions concerning the generation of power line harmonic radiation (PLHR) and magne-tospheric line radiation (MLR) are discussed, including the effective source of high harmonics of 50/60 Hz, and fine dynamic structure of the frequency spectrum of PLHR and MLR. It is shown, that thyristor-based power regulators used by large electrical power consumers produce the periodic sequences of current pulses with duration of about 10 microseconds in a power line. The repetition rate of these pulses is typically 100/120 Hz; the bandwidth is as broad as 100 kHz. For high harmonics of 50/60 Hz, the power line represents an effective traveling-wave (or Beverage) antenna, especially in a frequency range of several kHz corresponding to VLF whistler band in Earth ionosphere and magnetosphere. For the fixed length of the power line, which acts as antenna, radiation directivity diagram in relation to horizon depends of frequency. Hence the spatial separation of whistlers emitted at various frequencies (1-10 kHz in a consid-ered case) is possible, with subsequent propagation of whistlers with different frequencies along different L-shells. Estimations show that the efficiency of power line as travelling-wave antenna can be changed by variations of its load, but not more than twice ("weekend effect"). Since the PLHR can represent the sequence of short electromagnetic bursts, then careful se-lection of frequency-time resolution of the data acquisition equipment is needed. Typically, the time constant of the data recording and processing is too large, and the spectra of PLHR or MLR are characterized by a well-known line structure. At the same time, original bursty structure of PLHR can not be defined. Fine structure of MLR is also discussed. Frequency drift of MLR can be explained by the perturbations of the magnetospheric plasma by intense ULF waves and particle flows affecting the propagation of PLHR. Hence the physical nature of PLHR and MLR is the same, excepting the

  4. Method and apparatus for generating acoustic energy

    DOEpatents

    Guerrero, Hector N.

    2002-01-01

    A method and apparatus for generating and emitting amplified coherent acoustic energy. A cylindrical transducer is mounted within a housing, the transducer having an acoustically open end and an acoustically closed end. The interior of the transducer is filled with an active medium which may include scattering nuclei. Excitation of the transducer produces radially directed acoustic energy in the active medium, which is converted by the dimensions of the transducer, the acoustically closed end thereof, and the scattering nuclei, to amplified coherent acoustic energy directed longitudinally within the transducer. The energy is emitted through the acoustically open end of the transducer. The emitted energy can be used for, among other things, effecting a chemical reaction or removing scale from the interior walls of containment vessels.

  5. Origin of second-harmonic generation from individual silicon nanowires

    NASA Astrophysics Data System (ADS)

    Wiecha, Peter R.; Arbouet, Arnaud; Girard, Christian; Baron, Thierry; Paillard, Vincent

    2016-03-01

    We investigate second harmonic generation from individual silicon nanowires and study the influence of resonant optical modes on the far field nonlinear emission. We find that the polarization of the second harmonic has a size-dependent behavior and explain this phenomenon by considering different surface and bulk nonlinear susceptibility contributions. We show that the second harmonic generation has an entirely different origin, depending on the nanowire diameter and on whether the incident illumination is polarized parallel or perpendicular to the nanowire axis. The results open perspectives for further geometry-based studies on the origin and control of second harmonic generation in nanostructures of high-refractive index centrosymmetric dielectrics.

  6. Miniaturized Blue Laser using Second Harmonic Generation

    NASA Astrophysics Data System (ADS)

    Kitaoka, Yasuo; Yokoyama, Toshifumi; Mizuuchi, Kiminori; Yamamoto, Kazuhisa

    2000-06-01

    We demonstrate a miniaturized blue laser (5× 12× 1.5 mm3) using second harmonic generation (SHG), which consists of a quasi-phase-matched (QPM)-SHG waveguide device on an x-cut Mg-doped LiNbO3 substrate and a tunable distributed-Bragg-reflector (DBR) laser diode. By using the QPM-SHG waveguide device on an x-cut substrate, efficient optical coupling was realized without a half-wave plate, and the maximum coupling efficiency of 75% was achieved. The blue light power of 2 mW was generated for the fundamental coupling power of 20 mW, which agreed with a conversion efficiency of 10%. The mechanical stability of the planar-type butt-coupled SHG blue laser was examined, where the coupling efficiency was maintained constantly under the change of module temperature and the temperature cycle test from 10 to 60°C. We succeeded in downsizing the SHG blue laser to 0.1 cm3, which is sufficiently small for its application to optical disk systems.

  7. Intense harmonics generation with customized photon frequency and optical vortex

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaomei; Shen, Baifei; Shi, Yin; Zhang, Lingang; Ji, Liangliang; Wang, Xiaofeng; Xu, Zhizhan; Tajima, Toshiki

    2016-08-01

    An optical vortex with orbital angular momentum (OAM) enriches the light and matter interaction process, and helps reveal unexpected information in relativistic nonlinear optics. A scheme is proposed for the first time to explore the origin of photons in the generated harmonics, and produce relativistic intense harmonics with expected frequency and an optical vortex. When two counter-propagating Laguerre-Gaussian laser pulses impinge on a solid thin foil and interact with each other, the contribution of each input pulse in producing harmonics can be distinguished with the help of angular momentum conservation of photons, which is almost impossible for harmonic generation without an optical vortex. The generation of tunable, intense vortex harmonics with different photon topological charge is predicted based on the theoretical analysis and three-dimensional particle-in-cell simulations. Inheriting the properties of OAM and harmonics, the obtained intense vortex beam can be applied in a wide range of fields, including atom or molecule control and manipulation.

  8. Intense harmonics generation with customized photon frequency and optical vortex

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaomei; Shen, Baifei; Shi, Yin; Zhang, Lingang; Ji, Liangliang; Wang, Xiaofeng; Xu, Zhizhan; Tajima, Toshiki

    2016-08-01

    An optical vortex with orbital angular momentum (OAM) enriches the light and matter interaction process, and helps reveal unexpected information in relativistic nonlinear optics. A scheme is proposed for the first time to explore the origin of photons in the generated harmonics, and produce relativistic intense harmonics with expected frequency and an optical vortex. When two counter-propagating Laguerre–Gaussian laser pulses impinge on a solid thin foil and interact with each other, the contribution of each input pulse in producing harmonics can be distinguished with the help of angular momentum conservation of photons, which is almost impossible for harmonic generation without an optical vortex. The generation of tunable, intense vortex harmonics with different photon topological charge is predicted based on the theoretical analysis and three-dimensional particle-in-cell simulations. Inheriting the properties of OAM and harmonics, the obtained intense vortex beam can be applied in a wide range of fields, including atom or molecule control and manipulation.

  9. Second harmonic generation in human ovarian neoplasias

    NASA Astrophysics Data System (ADS)

    Lamonier, L.; Bottcher-Luiz, F.; Pietro, L.; Andrade, L. A. L. A.; de Thomaz, A. A.; Machado, C. L.; Cesar, C. L.

    2010-02-01

    Metastasis is the main cause of death in cancer patients; it requires a complex process of tumor cell dissemination, extra cellular matrix (ECM) remodeling, cell invasion and tumor-host interactions. Collagen is the major component of ECM; its fiber polymerization or degradation evolves in parallel with the evolution of the cancerous lesions. This study aimed to identify the collagen content, spatial distribution and fiber organization in biopsies of benign and malignant human ovarian tissues. Biopsies were prepared in slides without dyes and were exposed to 800nm Ti:Sapphire laser (Spectra Physics, 100 fs pulse duration, 800mW average power, 80MHz repetition rate). The obtained images were recorded at triplets, corresponding to clear field, multiphoton and second harmonic generation (SHG) mycroscopy. Data showed considerable anisotropy in malignant tissues, with regions of dense collagen arranged as individual fibers or in combination with immature segmental filaments. Radial fiber alignment or regions with minimal signal were observed in the high clinical grade tumors, suggesting degradation of original fibers or altered polymerization state of them. These findings allow us to assume that the collagen signature will be a reliable and a promising marker for diagnosis and prognosis in human ovarian cancers.

  10. Second harmonic generation from the 'centrosymmetric' crystals.

    PubMed

    Nalla, Venkatram; Medishetty, Raghavender; Wang, Yue; Bai, Zhaozhi; Sun, Handong; Wei, Ji; Vittal, Jagadese J

    2015-05-01

    Second harmonic generation (SHG) is a well known non-linear optical phenomena which can be observed only in non-centrosymmetric crystals due to non-zero hyperpolarizability. In the current work we observed SHG from a Zn(II) complex which was originally thought to have crystallized in the centrosymmetric space group C2/c. This has been attributed to the unequal antiparallel packing of the metal complexes in the non-symmetric space group Cc or residual non-centrosymmetry in C2/c giving rise to polarizability leading to strong SHG. The enhancement of SHG by UV light has been attributed to the increase in non-centrosymmetry and hence polarity of packing due to strain induced in the crystals. The SHG signals measured from these crystals were as large as potassium dihydrogen phosphate crystals, KH2PO4 (KDP), and showed temperature dependence. The highest SHG efficiency was observed at 50 K. The SHG phenomenon was observed at broad wavelengths ranging from visible to below-red in these crystals.

  11. Second harmonic generation polarization properties of myofilaments

    NASA Astrophysics Data System (ADS)

    Samim, Masood; Prent, Nicole; Dicenzo, Daniel; Stewart, Bryan; Barzda, Virginijus

    2014-05-01

    Second harmonic generation (SHG) polarization microscopy was used to investigate the organization of myosin nanomotors in myofilaments of muscle cells. The distribution of the second-order nonlinear susceptibility component ratio χzzz(2)/χzxx(2) along anisotropic bands of sarcomeres revealed differences between the headless and head-containing regions of myofilaments. The polarization-in polarization-out SHG measurements of headless myosin mutants of indirect flight muscle in Drosophila melanogaster confirmed a lower susceptibility component ratio compared to the head-containing myocytes with wild-type myosins. The increase in the ratio is assigned to the change in the deflection angle of the myosin S2 domain and possible contribution of myosin heads. The nonlinear susceptibility component ratio is a sensitive indicator of the myosin structure, and therefore, it can be used for conformational studies of myosin nanomotors. The measured ratio values can also be used as the reference for ab initio calculations of nonlinear optical properties of different parts of myosins.

  12. Higher-Order Harmonic Generation from Fullerene by Means of the Plasma Harmonic Method

    SciTech Connect

    Ganeev, R. A.; Bom, L. B. Elouga; Abdul-Hadi, J.; Ozaki, T.; Wong, M. C. H.; Brichta, J. P.; Bhardwaj, V. R.

    2009-01-09

    We demonstrate, for the first time, high-order harmonic generation from C{sub 60} by an intense femtosecond Ti:sapphire laser. Laser-produced plasmas from C{sub 60}-rich epoxy and C{sub 60} films were used as the nonlinear media. Harmonics up to the 19th order were observed. The harmonic yield from fullerene-rich plasma is about 25 times larger compared with those produced from a bulk carbon target. Structural studies of plasma debris confirm the presence and integrity of fullerenes within the plasma plume, indicating fullerenes as the source of high-order harmonics.

  13. Nonlinear harmonic generation and proposed experimental verification in SASE FELs.

    SciTech Connect

    Biedron, S. G.; Freund, H. P.; Milton, S. V.

    1999-08-24

    Recently, a 3D, polychromatic, nonlinear simulation code was developed to study the growth of nonlinear harmonics in self-amplified spontaneous emission (SASE) free-electron lasers (FELs). The simulation was applied to the parameters for each stage of the Advanced Photon Source (APS) SASE FEL, intended for operation in the visible, UV, and short UV wavelength regimes, respectively, to study the presence of nonlinear harmonic generation. Significant nonlinear harmonic growth is seen. Here, a discussion of the code development, the APS SASE FEL, the simulations and results, and, finally, the proposed experimental procedure for verification of such nonlinear harmonic generation at the APS SASE FEL will be given.

  14. Second-harmonic generation with Bessel beams

    NASA Astrophysics Data System (ADS)

    Shatrovoy, Oleg

    We present the results of a numerical simulation tool for modeling the second-harmonic generation (SHG) interaction experienced by a diffracting beam. This code is used to study the simultaneous frequency and spatial profile conversion of a truncated Bessel beam that closely resembles a higher-order mode (HOM) of an optical fiber. SHG with Bessel beams has been investigated in the past and was determined have limited value because it is less efficient than SHG with a Gaussian beam in the undepleted pump regime. This thesis considers, for the first time to the best of our knowledge, whether most of the power from a Bessel-like beam could be converted into a second-harmonic beam (full depletion), as is the case with a Gaussian beam. We study this problem because using HOMs for fiber lasers and amplifiers allows reduced optical intensities, which mitigates nonlinearities, and is one possible way to increase the available output powers of fiber laser systems. The chief disadvantage of using HOM fiber amplifiers is the spatial profile of the output, but this can be transformed as part of the SHG interaction, most notably to a quasi-Gaussian profile when the phase mismatch meets the noncollinear criteria. We predict, based on numerical simulation, that noncollinear SHG (NC-SHG) can simultaneously perform highly efficient (90%) wavelength conversion from 1064 nm to 532 nm, as well as concurrent mode transformation from a truncated Bessel beam to a Gaussian-like beam (94% overlap with a Gaussian) at modest input powers (250 W, peak power or continuous-wave operation). These simulated results reveal two attractive features -- the feasibility of efficiently converting HOMs of fibers into Gaussian-like beams, and the ability to simultaneously perform frequency conversion. Combining the high powers that are possible with HOM fiber amplifiers with access to non-traditional wavelengths may offer significant advantages over the state of the art for many important applications

  15. Harmonics generated from a DC biased transformer

    SciTech Connect

    Shu Lu; Yilu Liu; Ree, J. De La . The Bradley Dept. of Electrical Engineering)

    1993-04-01

    The paper presents harmonic characteristics of transformer excitation currents under DC bias caused by geomagnetically induced currents (GIC). A newly developed saturation model of a single phase shell form transformer based on 3D finite element analysis is used to calculate the excitation currents. As a consequence, the complete variations of excitation current harmonics with respect to an extended range of GIC bias are revealed. The results of this study are useful in understanding transformers as harmonic sources and the impact on power systems during a solar magnetic disturbance.

  16. Efficient millimeter wave 1140 GHz/ diode for harmonic power generation

    NASA Technical Reports Server (NTRS)

    1967-01-01

    Epitaxial gallium arsenide diode junction formed in a crossed waveguide structure operates as a variable reactance harmonic generator. This varactor diode can generate power efficiently in the low-millimeter wavelength.

  17. SEVENTH HARMONIC 20 GHz CO-GENERATOR

    SciTech Connect

    Hirshfield, Jay L

    2014-04-08

    To satisfy the need for multi-MW rf sources in frequency ranges where commercial sources do not exist, a study was undertaken on a class of devices based on gyro-harmonic frequency multiplication. This mechanism relies upon adding energy in gyrating motion to a linear electron beam that traverses a rotating-mode TE111-mode drive cavity in a dc magnetic field. The beam then drifts along the magnetic field into a second cavity, operating in the TEn11-mode tuned to the nth harmonic of the drive cavity. Studies of this configuration have been carried out for 2 < n < 7. Results are given for multi-MW, efficient operation of a 7th harmonic device operating at 20 GHz, and a 2nd harmonic device operating at 22.4 GHz.

  18. High-order harmonic generation in solids: A unifying approach

    NASA Astrophysics Data System (ADS)

    Luu, Tran Trung; Wörner, Hans Jakob

    2016-09-01

    There have been several experimental reports showing high-order harmonic generation from solids, but there has been no unifying theory presented as of yet for all these experiments. Here we report on the systematic investigation of high-order harmonic generation within the semiconductor Bloch equations, taking into account multiple bands and relaxation processes phenomenologically. In addition to reproducing key experiments, we show the following: (i) Electronic excitations, direct-indirect excitation pathways, and relaxation processes are responsible for high-order harmonic generation and control using midinfrared drivers in zinc oxide. We describe an intuitive picture explaining a two-color experiment involving noninversion symmetric crystals. (ii) High-order harmonic generation can be considered as a general feature of ultrafast strong-field-driven electronic dynamics in solids. We demonstrate this statement by predicting high-order harmonic spectra of solids that have not been studied yet.

  19. Illuminating Molecular Symmetries with Bicircular High-Order-Harmonic Generation

    NASA Astrophysics Data System (ADS)

    Reich, Daniel M.; Madsen, Lars Bojer

    2016-09-01

    We present a general theory of bicircular high-order-harmonic generation from N -fold rotationally symmetric molecules. Using a rotating frame of reference we predict the complete structure of the high-order-harmonic spectra for arbitrary driving frequency ratios and show how molecular symmetries can be directly identified from the harmonic signal. Our findings reveal that a characteristic fingerprint of rotational molecular symmetries can be universally observed in the ultrafast response of molecules to strong bicircular fields.

  20. Harmonics Generation by Surface Plasmon Polaritons on Single Nanowires

    PubMed Central

    2016-01-01

    We present experimental observations of visible wavelength second- and third-harmonic generation on single plasmonic nanowires of variable widths. We identify that near-infrared surface plasmon polaritons, which are guided along the nanowire, act as the source of the harmonics generation. We discuss the underlying mechanism of this nonlinear process, using a combination of spatially resolved measurements and numerical simulations to show that the visible harmonics are generated via a combination of both local and propagating plasmonic modes. Our results provide the first demonstration of nanoscale nonlinear optics with guided, propagating plasmonic modes on a lithographically defined chip, opening up new routes toward integrated optical circuits for information processing. PMID:27563688

  1. Strategies for reliable second harmonic of nonlinear acoustic wave through cement-based materials

    NASA Astrophysics Data System (ADS)

    Xie, Fan; Guo, Zhiwei; Zhang, Jinwei

    2014-07-01

    The strategies for retrieving reliable nonlinear second harmonic in cement-based materials are proposed in this paper using high-performance test system, piezoelectric transducers with central frequency in MHz, monochromatic tone-burst excitation and robust data process method.The Fundamental and second-order harmonics are measured to retrieve reliable acoustic nonlinearity with the input power level increased from ∼50 V to ∼280 V. About 173 times repeatable measurements are conducted to verify the stability of the experimental system. Specimens with three distinct aggregate sizes are used to measure the acoustic nonlinearity under uniaxial load. The results show a decrease in the measured acoustic nonlinearity at early damage stage, then a slight increase when large cracks coalesce. The rapid increase in acoustic nonlinearity at the final stage indicates the imminent failure. Our results also suggest that the nonlinear ultrasonic method is more sensitive than P-wave velocity for damage evaluation.

  2. Spectrum of second-harmonic radiation generated from incoherent light

    SciTech Connect

    Stabinis, A.; Pyragaite, V.; Tamosauskas, G.; Piskarskas, A.

    2011-10-15

    We report on the development of the theory of second-harmonic generation by an incoherent pump with broad angular and frequency spectra. We show that spatial as well as temporal walk-off effects in a nonlinear crystal result in angular dispersion of the second-harmonic radiation. We demonstrate that the acceptance angle in second-harmonic generation by incoherent light is caused by the width of the pump angular spectrum and the resulting angular dispersion of second-harmonic radiation but does not depend on crystal length. In this case the frequency spectrum of second-harmonic radiation is determined by its angular dispersion and the pump angular spectrum. The theory is supported by an experiment in which a LiIO{sub 3} crystal was pumped by a tungsten halogen lamp.

  3. High harmonic generation in a semi-infinite gas cell.

    PubMed

    Sutherland, Julia; Christensen, E; Powers, N; Rhynard, S; Painter, J; Peatross, J

    2004-09-20

    Ten-millijoule 35-femtosecond laser pulses interact with a cell of helium or neon that extends from a focusing lens to an exit foil near the laser focus. High harmonic orders in the range of 50 to 100 are investigated as a function of focal position relative to the exit foil. An aperture placed in front of the focusing lens increases the brightness of observed harmonics by more than an order of magnitude. Counter-propagating light is used to directly probe where the high harmonics are generated within the laser focus. In neon, the harmonics are generated in the last few millimeters before the exit foil, limited by absorption. In helium, the harmonics are produced over a much longer distance. PMID:19483992

  4. Detection of Molecular Monolayers by Optical Second-Harmonic Generation

    SciTech Connect

    Chen, C. K.; Heinz, T. F.; Ricard, D.; Shen, Y. R.

    1980-12-22

    Second harmonic generation is shown to be sensitive enough to detect molecular monolayers adsorbed on a silver surface. Adsorption of AgCl and pyridine on silver during and after an electrolytic cycle can be easily observed,

  5. Frequency-resolved optical grating using third-harmonic generation

    SciTech Connect

    Tsang, T.; Krumbuegel, M.A.; Delong, K.W.

    1995-12-01

    We demonstrate the first frequency-resolved optical gating measurement of an laser oscillator without the time ambiguity using third-harmonic generation. The experiment agrees well with the phase-retrieved spectrograms.

  6. Squeezed light from second-harmonic generation: experiment versus theory.

    PubMed

    Ralph, T C; Taubman, M S; White, A G; McClelland, D E; Bachor, H A

    1995-06-01

    We report excellent quantitative agreement between theoretical predictions and experimental observation of squeezing from a singly resonant second-harmonic-generating crystal. Limitations in the noise suppression imposed by the pump laser are explicitly modeled and confirmed by our measurements.

  7. High order harmonic generation in dual gas multi-jets

    SciTech Connect

    Tosa, Valer E-mail: calin.hojbota@itim-cj.ro; Hojbota, Calin E-mail: calin.hojbota@itim-cj.ro

    2013-11-13

    High order harmonic generation (HHG) in gas media suffers from a low conversion efficiency that has its origins in the interaction of the atom/molecule with the laser field. Phase matching is the main way to enhance the harmonic flux and several solutions have been designed to achieve it. Here we present numerical results modeling HHG in a system of multi-jets in which two gases alternate: the first gas jet (for example Ne) generates harmonics and the second one which ionizes easier, recover the phase matching condition. We obtain configurations which are experimentally feasible with respect to pressures and dimensions of the jets.

  8. Spin-Squeezing Entanglement of Second-Harmonic Generation

    NASA Astrophysics Data System (ADS)

    Shu, Jian

    2016-10-01

    An experimentally feasible scheme for generating spin-squeezing entanglement via second-harmonic generation was presented. Its shown that spin-squeezing entanglement can be generated rapidly in the dynamical process by adjusting coupling constant, detuning, the total number of particles and the evolution time.

  9. Generation of Acoustic Signals from Buried Explosions

    NASA Astrophysics Data System (ADS)

    Bonner, J. L.; Reinke, R.; Waxler, R.; Lenox, E. A.

    2012-12-01

    Buried explosions generate both seismic and acoustic signals. The mechanism for the acoustic generation is generally assumed to be large ground motions above the source region that cause atmospheric pressure disturbances which can propagate locally or regionally depending on source size and weather conditions. In order to better understand the factors that control acoustic generation from buried explosions, we conducted a series of 200 lb explosions detonated in and above the dry alluvium and limestones of Kirtland AFB, New Mexico. In this experiment, nicknamed HUMBLE REDWOOD III, we detonated charges at heights of burst of 2 m (no crater) and depths of burst of 7 m (fully confined). The seismic and acoustic signals were recorded on a network of near-source (< 90 m) co-located accelerometer and overpressure sensors, circular rings of acoustic sensors at 0.3 and 1 km, and multiple seismic and infrasound sensors at local-to-regional distances. Near-source acoustic signals for the 200 lb buried explosion in limestone show an impulsive, short-duration (0.04 s) initial peak, followed by a broad duration (0.3 s) negative pressure trough, and finally a second positive pulse (0.18 s duration). The entire width of the acoustic signal generated by this small buried explosion is 0.5 s and results in a 2 Hz peak in spectral energy. High-velocity wind conditions quickly attenuate the signal with few observations beyond 1 km. We have attempted to model these acoustic waveforms by estimating near-source ground motion using synthetic spall seismograms. Spall seismograms have similar characteristics as the observed acoustics and usually include an initial positive motion P wave, followed by -1 g acceleration due to the ballistic free fall of the near surface rock units, and ends with positive accelerations due to "slapdown" of the material. Spall seismograms were synthesized using emplacement media parameters and high-speed video observations of the surface movements. We present a

  10. Noble gas clusters and nanoplasmas in high harmonic generation

    NASA Astrophysics Data System (ADS)

    Aladi, M.; Bolla, R.; Rácz, P.; Földes, I. B.

    2016-02-01

    We report a study of high harmonic generation from noble gas clusters of xenon atoms in a gas jet. Harmonic spectra were investigated as a function of backing pressure, showing spectral shifts due to the nanoplasma electrons in the clusters. At certain value of laser intensity this process may oppose the effect of the well-known ionization-induced blueshift. In addition, these cluster-induced harmonic redshifts may give the possibility to estimate cluster density and cluster size in the laser-gas jet interaction range.

  11. Control of Laser High-Harmonic Generation with Counterpropagating Light

    NASA Astrophysics Data System (ADS)

    Voronov, S. L.; Kohl, I.; Madsen, J. B.; Simmons, J.; Terry, N.; Titensor, J.; Wang, Q.; Peatross, J.

    2001-09-01

    Relatively weak counterpropagating light is shown to disrupt the emission of laser high-harmonic generation. Harmonic orders ranging from the teens to the low thirties produced by a 30-femtosecond pulse in a narrow argon jet are ``shut down'' with a contrast as high as 2 orders of magnitude by a chirped 1-picosecond counterpropagating laser pulse (60 times less intense). Alternatively, under poor phase-matching conditions, the counterpropagating light boosts harmonic production by similar contrast through quasiphase matching where out-of-phase emission is suppressed.

  12. Quantum theory of third-harmonic generation in graphene

    NASA Astrophysics Data System (ADS)

    Mikhailov, S. A.

    2014-12-01

    A quantum theory of third-harmonic generation in graphene is presented. An analytical formula for the nonlinear conductivity tensor σαβ γ δ (3 )(ω ,ω ,ω ) is derived. Resonant maxima of the third harmonic are shown to exist at low frequencies ω ≪EF/ℏ , as well as around the frequency ω =2 EF/ℏ , where EF is the Fermi energy in graphene. At an input power of a CO2 laser (λ ≈10 μ m ) of about 1 MW /cm2 , the output power of the third harmonic (λ ≈3.3 μ m ) is expected to be ≃50 W /cm2 .

  13. Optical third-harmonic generation using ultrashort laser pulses

    SciTech Connect

    Stoker, D.; Keto, J.W.; Becker, M.F.

    2005-06-15

    To better predict optical third-harmonic generation (THG) in transparent dielectrics, we model a typical ultrashort pulsed Gaussian beam, including both group velocity mismatch and phase mismatch of the fundamental and harmonic fields. We find that competition between the group velocity mismatch and phase mismatch leads to third-harmonic generation that is sensitive only to interfaces. In this case, the spatial resolution is determined by the group velocity walk-off length. THG of modern femtosecond lasers in optical solids is a bulk process, without a surface susceptibility, but bears the signature of a surface enhancement effect in z-scan measurements. We demonstrate the accuracy of the model, by showing the agreement between the predicted spectral intensity and the measured third-harmonic spectrum from a thin sapphire crystal.

  14. Spatiotemporal toroidal waves from the transverse second-harmonic generation.

    PubMed

    Saltiel, Solomon M; Neshev, Dragomir N; Fischer, Robert; Krolikowski, Wieslaw; Arie, Ady; Kivshar, Yuri S

    2008-03-01

    We study the second-harmonic generation via transversely matched interaction of two counterpropagating ultrashort pulses in chi(2) photonic structures. We show that the emitted second-harmonic wave attains the form of spatially expanding toroid with the initial thickness given by the cross correlation of the pulses. We demonstrate the formation of such toroidal waves in crystals with random ferroelectric domains as well as in annularly poled nonlinear photonic structures.

  15. Resonant high-order harmonic generation from plasma ablation: Laser intensity dependence of the harmonic intensity and phase

    SciTech Connect

    Milosevic, D. B.

    2010-02-15

    Experimentally observed strong enhancement of a single high-order harmonic in harmonic generation from low-ionized laser plasma ablation is explained as resonant harmonic generation. The resonant harmonic intensity increases regularly with the increase of the laser intensity, while the phase of the resonant harmonic is almost independent of the laser intensity. This is in sharp contrast with the usual plateau and cutoff harmonics, the intensity of which exhibits wild oscillations while its phase changes rapidly with the laser intensity. The temporal profile of a group of harmonics, which includes the resonant harmonic, has the form of a broad peak in each laser-field half cycle. These characteristics of resonant harmonics can have an important application in attoscience. We illustrate our results using examples of Sn and Sb plasmas.

  16. Generation of higher odd harmonics in a defective photonic crystal

    SciTech Connect

    Ramanujam, N. R.; Wilson, K. S. Joseph

    2015-06-24

    A photonic crystal (AB){sup 2}(DB)(AB){sup 2} with high refractive index medium as silicon and low refractive medium as air is considered. Using the transfer matrix method, the transmission properties as a function of wavelength with photonic band gaps has been obtained. We are able to demonstrate the generation of third, fifth, seventh and ninth harmonics in the present work. We show that if the air medium is removed in the defect, the defect modes are generated but not harmonics. It can be designed to have a frequency conversion, and have a potential for becoming the basis for the next generation of optical devices.

  17. Dynamic investigation of Drosophila myocytes with second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Greenhalgh, Catherine; Stewart, Bryan; Cisek, Richard; Prent, Nicole; Major, Arkady; Barzda, Virginijus

    2006-09-01

    The functional dynamics and structure of both larval and adult Drosophila melanogaster muscle were investigated with a nonlinear multimodal microscope. Imaging was carried out using a home built microscope capable of recording the multiphoton excitation fluorescence, second harmonic generation, and third harmonic generation signals simultaneously at a scanning rate of up to ~12 frames/sec. The sample was excited by a home built femtosecond Ti:Sapphire laser at 840 nm, or by a Yb-ion doped potassium gadolinium tungstate (Yb:KGW) crystal based oscillator at 1042 nm. There was no observable damage detected in the myocyte after prolonged scanning with either of the lasers. Microscopic second harmonic generation (SHG) appears particularly strong in the myocytes. This allows the fast contraction dynamics of the myocytes to be followed. The larger sarcomere size observed in the larvae myocytes is especially well suited for studying the contraction dynamics. Microscopic imaging of muscle contractions showed different relaxation and contraction rates. The SHG intensities were significantly higher in the relaxed state of the myocyte compared to the contracted state. The imaging also revealed disappearance of SHG signal in highly stretched sarcomeres, indicating that SHG diminishes in the disordered structures. The study illustrates that SHG microscopy, combined with other nonlinear contrast mechanisms, can help to elucidate physiological mechanisms of contraction. This study also provides further insight into the mechanisms of harmonic generation in biological tissue and shows that crystalline arrangement of macromolecules has a determining factor for the high efficiency second harmonic generation from the bulk structures.

  18. Bernstein wave aided laser third harmonic generation in a plasma

    NASA Astrophysics Data System (ADS)

    Tyagi, Yachna; Tripathi, Deepak; Kumar, Ashok

    2016-09-01

    The process of Bernstein wave aided resonant third harmonic generation of laser in a magnetized plasma is investigated. The extra-ordinary mode (X-mode) laser of frequency ω 0 and wave number k → 0 , travelling across the magnetic field in a plasma, exerts a second harmonic ponderomotive force on the electrons imparting them an oscillatory velocity v → 2 ω0 , 2 k → 0 . This velocity beats with the density perturbation due to the Bernstein wave to produce a density perturbation at cyclotron frequency shifted second harmonic. The density perturbation couples with the oscillatory velocity v → ω0 , k → 0 of X-mode of the laser to produce the cyclotron frequency shifted third harmonic current density leading to harmonic radiation. The phase matching condition for the up shifted frequency is satisfied when the Bernstein wave is nearly counter-propagating to the laser. As the transverse wave number of the Bernstein wave is large, it is effective in the phase matched third harmonic generation, when the laser frequency is not too far from the upper hybrid frequency.

  19. Single-shot fluctuations in waveguided high-harmonic generation.

    PubMed

    Goh, S J; Tao, Y; van der Slot, P J M; Bastiaens, H J M; Herek, J; Biedron, S G; Danailov, M B; Milton, S V; Boller, K-J

    2015-09-21

    For exploring the application potential of coherent soft x-ray (SXR) and extreme ultraviolet radiation (XUV) provided by high-harmonic generation, it is important to characterize the central output parameters. Of specific importance are pulse-to-pulse (shot-to-shot) fluctuations of the high-harmonic output energy, fluctuations of the direction of the emission (pointing instabilities), and fluctuations of the beam divergence and shape that reduce the spatial coherence. We present the first single-shot measurements of waveguided high-harmonic generation in a waveguided (capillary-based) geometry. Using a capillary waveguide filled with Argon gas as the nonlinear medium, we provide the first characterization of shot-to-shot fluctuations of the pulse energy, of the divergence and of the beam pointing. We record the strength of these fluctuations vs. two basic input parameters, which are the drive laser pulse energy and the gas pressure in the capillary waveguide. In correlation measurements between single-shot drive laser beam profiles and single-shot high-harmonic beam profiles we prove the absence of drive laser beam-pointing-induced fluctuations in the high-harmonic output. We attribute the main source of high-harmonic fluctuations to ionization-induced nonlinear mode mixing during propagation of the drive laser pulse inside the capillary waveguide. PMID:26406689

  20. Harmonic Generation in Argon by Femtosecond Ti:Sapphire Laser

    NASA Astrophysics Data System (ADS)

    Qindeel, Rabia; Samad, Ricardo Elgul; de Freitas, Anderson Zanardi; de Matos, Paulo Sergio Fabris; Falcão, Edilson Lucena; Vieira Junior, Nilson Dias

    Generation of harmonics using a gas nozzle has remarkable feature in various applications. Pulses from a Ti:Sapphire laser, centered at 785 nm, in a 4 kHz train, with 25 femtoseconds and 800 μJ of maximum energy were employed to generate harmonics in an argon gas nozzle. We present the current results on the focusability of the nozzle, harmonic radiation, measurement of the influence of laser power and laser focus position on the divergence of gas nozzle. We have successfully generated 3rd, 5th and 7th harmonics in Argon at different laser powers. The results show that the harmonic signals are almost same for laser average powers over 1.0 W and variation always appears below 1.0 W. It means that there is saturation in the physical phenomenon happening inside the gas nozzle at high laser powers and the variation is non-linear below 1.0 W. These results are embedded in an effort towards x-ray generation in the water window.

  1. A simulation study of harmonics regeneration in noise reduction for electric and acoustic stimulation.

    PubMed

    Hu, Yi

    2010-05-01

    Recent research results show that combined electric and acoustic stimulation (EAS) significantly improves speech recognition in noise, and it is generally established that access to the improved F0 representation of target speech, along with the glimpse cues, provide the EAS benefits. Under noisy listening conditions, noise signals degrade these important cues by introducing undesired temporal-frequency components and corrupting harmonics structure. In this study, the potential of combining noise reduction and harmonics regeneration techniques was investigated to further improve speech intelligibility in noise by providing improved beneficial cues for EAS. Three hypotheses were tested: (1) noise reduction methods can improve speech intelligibility in noise for EAS; (2) harmonics regeneration after noise reduction can further improve speech intelligibility in noise for EAS; and (3) harmonics sideband constraints in frequency domain (or equivalently, amplitude modulation in temporal domain), even deterministic ones, can provide additional benefits. Test results demonstrate that combining noise reduction and harmonics regeneration can significantly improve speech recognition in noise for EAS, and it is also beneficial to preserve the harmonics sidebands under adverse listening conditions. This finding warrants further work into the development of algorithms that regenerate harmonics and the related sidebands for EAS processing under noisy conditions.

  2. Continuous control of the nonlinearity phase for harmonic generations.

    PubMed

    Li, Guixin; Chen, Shumei; Pholchai, Nitipat; Reineke, Bernhard; Wong, Polis Wing Han; Pun, Edwin Yue Bun; Cheah, Kok Wai; Zentgraf, Thomas; Zhang, Shuang

    2015-06-01

    The capability of locally engineering the nonlinear optical properties of media is crucial in nonlinear optics. Although poling is the most widely employed technique for achieving locally controlled nonlinearity, it leads only to a binary nonlinear state, which is equivalent to a discrete phase change of π in the nonlinear polarizability. Here, inspired by the concept of spin-rotation coupling, we experimentally demonstrate nonlinear metasurfaces with homogeneous linear optical properties but spatially varying effective nonlinear polarizability with continuously controllable phase. The continuous phase control over the local nonlinearity is demonstrated for second and third harmonic generation by using nonlinear metasurfaces consisting of nanoantennas of C3 and C4 rotational symmetries, respectively. The continuous phase engineering of the effective nonlinear polarizability enables complete control over the propagation of harmonic generation signals. Therefore, this method seamlessly combines the generation and manipulation of harmonic waves, paving the way for highly compact nonlinear nanophotonic devices. PMID:25849530

  3. Efficient Forward Second-Harmonic Generation from Planar Archimedean Nanospirals

    DOE PAGES

    Davidson, Roderick B.; Ziegler, Jed I.; Vargas, Guillermo; Avanesyan, Sergey M.; Gong, Yu; Hess, Wayne P.; Haglund, Jr., Richard F.

    2015-05-21

    The enhanced electric field at plasmonic resonances in nanoscale antennas can lead to efficient harmonic generation, especially when the plasmonic geometry is asymmetric on either inter-particle or intra-particle levels. The planar Archimedean nanospiral offers a unique geometrical asymmetry for second-harmonic generation (SHG) because the SHG results neither from arranging centrosymmetric nanoparticles in asymmetric groupings, nor from noncentrosymmetric nanoparticles that retain a local axis of symmetry. Here we report forward SHG from planar arrays of Archimedean nanospirals using 15 fs pulse from a Ti:sapphire oscillator tuned to 800 nm wavelength. The measured harmonic-generation efficiencies are 2.6•10-9, 8•10-9 and 1.3•10-8 for left-handedmore » circular, linear, and right-handed circular polarizations, respectively.« less

  4. Harmonic surface acoustic waves on gallium nitride thin films.

    PubMed

    Justice, Joshua; Lee, Kyoungnae; Korakakis, D

    2012-08-01

    SAW devices operating at the fundamental frequency and the 5th, 7th, 9th, and 11th harmonics have been designed, fabricated, and measured. Devices were fabricated on GaN thin films on sapphire substrates, which were grown via metal organic vapor phase epitaxy (MOVPE). Operating frequencies of 230, 962, 1338, 1720, and 2100 MHz were achieved with devices that had a fundamental wavelength, lambda0 = 20 μm. Gigahertz operation is realized with relatively large interdigital transducers that do not require complicated submicrometer fabrication techniques. SAW devices fabricated on the GaN/sapphire bilayer have an anisotropic propagation when the wavelength is longer than the GaN film thickness. It is shown that for GaN thin films, where kh(GaN) > 10 (k = 2pi/lambda and h(GaN) = GaN film thickness), effects of the substrate on the SAW propagation are eliminated. Bulk mode suppression at harmonic operation is also demonstrated. PMID:22899127

  5. Harmonic surface acoustic waves on gallium nitride thin films.

    PubMed

    Justice, Joshua; Lee, Kyoungnae; Korakakis, D

    2012-08-01

    SAW devices operating at the fundamental frequency and the 5th, 7th, 9th, and 11th harmonics have been designed, fabricated, and measured. Devices were fabricated on GaN thin films on sapphire substrates, which were grown via metal organic vapor phase epitaxy (MOVPE). Operating frequencies of 230, 962, 1338, 1720, and 2100 MHz were achieved with devices that had a fundamental wavelength, lambda0 = 20 μm. Gigahertz operation is realized with relatively large interdigital transducers that do not require complicated submicrometer fabrication techniques. SAW devices fabricated on the GaN/sapphire bilayer have an anisotropic propagation when the wavelength is longer than the GaN film thickness. It is shown that for GaN thin films, where kh(GaN) > 10 (k = 2pi/lambda and h(GaN) = GaN film thickness), effects of the substrate on the SAW propagation are eliminated. Bulk mode suppression at harmonic operation is also demonstrated.

  6. Confocal Imaging of Biological Tissues Using Second Harmonic Generation

    SciTech Connect

    Kim, B-M.; Stoller, P.; Reiser, K.; Eichler, J.; Yan, M.; Rubenchik, A.; Da Silva, L.

    2000-03-06

    A confocal microscopy imaging system was devised to selectively detect Second harmonic signals generated by biological tissues. Several types of biological tissues were examined using this imaging system, including human teeth, bovine blood vessels, and chicken skin. All these tissues generated strong second harmonic signals. There is considerable evidence that the source of these signals in tissue is collagen. Collagen, the predominant component of most tissues, is known to have second order nonlinear susceptibility. This technique may have diagnostic usefulness in pathophysiological conditions characterized by changes in collagen structure including malignant transformation of nevi, progression of diabetic complications, and abnormalities in wound healing.

  7. Optimization study of third harmonic generation in quantum cascade lasers.

    PubMed

    Mojibpour, Ali; Pourfath, Mahdi; Kosina, Hans

    2014-08-25

    A systematic optimization study of quantum cascade lasers with integrated nonlinearity for third-harmonic generation is performed. To model current transport the Pauli master equation is solved using a Monte Carlo approach. A multi-objective particle swarm optimization algorithm is applied to obtain the Pareto front. Our theoretical analysis indicates an optimized structure with five orders of magnitude increase in the generated third-harmonic power with respect to the reference design. This striking performance comes with a low threshold current density of about 1.6 kA/cm2 and is attributed to double resonant phonon scattering assisted extraction and injection scheme of the laser.

  8. Efficient forward second-harmonic generation from planar archimedean nanospirals

    SciTech Connect

    Davidson, II, Roderick B.; Ziegler, Jed I.; Vargas, Guillermo; Avanesyan, Sergey M.; Gong, Yu; Hess, Wayne; Haglund, Jr., Richard F.

    2015-05-01

    Here, the enhanced electric field at plasmonic resonances in nanoscale antennas can lead to efficient harmonic generation, especially when the plasmonic geometry is asymmetric on either inter-particle or intra-particle levels. The planar Archimedean nanospiral offers a unique geometrical asymmetry for second-harmonic generation (SHG) because the SHG results neither from arranging centrosymmetric nanoparticles in asymmetric groupings, nor from non-centrosymmetric nanoparticles that retain a local axis of symmetry. Here, we report forward SHG from planar arrays of Archimedean nanospirals using 15 fs pulses from a Ti:sapphire oscillator tuned to 800 nm wavelength.

  9. Even harmonic generation in isotropic media of dissociating homonuclear molecules

    PubMed Central

    Silva, R. E. F.; Rivière, P.; Morales, F.; Smirnova, O.; Ivanov, M.; Martín, F.

    2016-01-01

    Isotropic gases irradiated by long pulses of intense IR light can generate very high harmonics of the incident field. It is generally accepted that, due to the symmetry of the generating medium, be it an atomic or an isotropic molecular gas, only odd harmonics of the driving field can be produced. Here we show how the interplay of electronic and nuclear dynamics can lead to a marked breakdown of this standard picture: a substantial part of the harmonic spectrum can consist of even rather than odd harmonics. We demonstrate the effect using ab-initio solutions of the time-dependent Schrödinger equation for and its isotopes in full dimensionality. By means of a simple analytical model, we identify its physical origin, which is the appearance of a permanent dipole moment in dissociating homonuclear molecules, caused by light-induced localization of the electric charge during dissociation. The effect arises for sufficiently long laser pulses and the region of the spectrum where even harmonics are produced is controlled by pulse duration. Our results (i) show how the interplay of femtosecond nuclear and attosecond electronic dynamics, which affects the charge flow inside the dissociating molecule, is reflected in the nonlinear response, and (ii) force one to augment standard selection rules found in nonlinear optics textbooks by considering light-induced modifications of the medium during the generation process. PMID:27596609

  10. Even harmonic generation in isotropic media of dissociating homonuclear molecules.

    PubMed

    Silva, R E F; Rivière, P; Morales, F; Smirnova, O; Ivanov, M; Martín, F

    2016-01-01

    Isotropic gases irradiated by long pulses of intense IR light can generate very high harmonics of the incident field. It is generally accepted that, due to the symmetry of the generating medium, be it an atomic or an isotropic molecular gas, only odd harmonics of the driving field can be produced. Here we show how the interplay of electronic and nuclear dynamics can lead to a marked breakdown of this standard picture: a substantial part of the harmonic spectrum can consist of even rather than odd harmonics. We demonstrate the effect using ab-initio solutions of the time-dependent Schrödinger equation for and its isotopes in full dimensionality. By means of a simple analytical model, we identify its physical origin, which is the appearance of a permanent dipole moment in dissociating homonuclear molecules, caused by light-induced localization of the electric charge during dissociation. The effect arises for sufficiently long laser pulses and the region of the spectrum where even harmonics are produced is controlled by pulse duration. Our results (i) show how the interplay of femtosecond nuclear and attosecond electronic dynamics, which affects the charge flow inside the dissociating molecule, is reflected in the nonlinear response, and (ii) force one to augment standard selection rules found in nonlinear optics textbooks by considering light-induced modifications of the medium during the generation process. PMID:27596609

  11. Harmonic Generation from Solid Targets - Optmization of Source Parameters

    NASA Astrophysics Data System (ADS)

    Zepf, Matthew; Watts, I. F.; Dangor, A. E.; Norreys, P. A.; Chambers, D. M.; Machacek, A.; Wark, J. S.; Tsakiris, G. D.

    1998-11-01

    High harmonics from solid targets have received renewed interest over the last few years. Theoretical predictions using 1 1/2 D codes suggest that very high orders (>100 ) can be generated at conversion efficiencies in excess of 10-6 [1,2] at Iλ^2 > 10^19 W/cm^2. Experiments have since been performed with pulses varying from 100 fs to 2.5 ps in duration [3-6]. The steep density gradient necessary to generate the harmonics can be generated by either ponderomotive steepening or by using ultraclean pulses which preserve the initial solid vacuum boundary. The two regimes are compared in terms of their dependence on the laser parameters and the emitted harmonic radiation. Particular emphasis will be given to measurements of the holeboring velocity, the polarisation of the harmonics and the intensity scaling in the two regimes. This comparison enables us to find the ideal parameter range for the optimization of harmonic source. [1] R. Lichters et al., Physics of Plasmas 3, 3425, (1996). [2] P. Gibbon, IEEE J. of Q. Elec. 33, 1915 (1997). [3] S. Kohlweyer, et al., Optics Comm. 177, 431 (1995). [4] P. Norreys et al., Phys. Rev. Lett., 76, 1832 (1995). [5] D. von der Linde et al., Phys. Rev. A, 52, R25 (1995) [6] M. Zepf, et al., submitted for publication in Phys. Rev. Lett.

  12. Feasibility study of generating ultra-high harmonic radiation with a single stage echo-enabled harmonic generation scheme

    NASA Astrophysics Data System (ADS)

    Zhou, Kaishang; Feng, Chao; Wang, Dong

    2016-10-01

    The echo enabled harmonic generation (EEHG) scheme holds the ability for the generation of fully coherent soft x-ray free-electron laser (FEL) pulses directly from external UV seeding sources. In this paper, we study the feasibility of using a single stage EEHG to generate coherent radiation in the "water window" and beyond. Using the high-order operating modes of the EEHG scheme, intensive numerical simulations have been performed considering various three-dimensional effects. The simulation results demonstrated that coherent soft x-ray radiation at 150th harmonic (1.77 nm) of the seed can be produced by a single stage EEHG. The decreasing of the final bunching factor at the desired harmonic caused by intra beam scattering (IBS) effect has also been analyzed.

  13. Observation of Electronic Structure Minima in High-Harmonic Generation

    SciTech Connect

    Woerner, Hans Jakob; Villeneuve, D. M.; Niikura, Hiromichi; Bertrand, Julien B.; Corkum, P. B.

    2009-03-13

    We report detailed measurements of the high-harmonic spectra generated from argon atoms. The spectra exhibit a deep minimum that is shown to be independent of the laser intensity, and is thus a clear measure of the electronic structure of the atom. We show that exact field-free continuum wave functions reproduce the minimum, but plane wave and Coulomb wave functions do not. This remarkable observation suggests that electronic structure can be accurately determined in high-harmonic experiments despite the presence of the strong laser field. Our results clarify the relation between high-harmonic generation and photoelectron spectroscopy. The use of exact continuum functions also resolves the ambiguity associated with the choice of the dispersion relation.

  14. Generation of harmonics and supercontinuum in nematic liquid crystals

    SciTech Connect

    Nyushkov, B N; Trashkeev, S I; Klementyev, Vasilii M; Pivtsov, V S; Kobtsev, Sergey M

    2013-02-28

    Nonlinear optical properties of nematic liquid crystals (NLC) have been investigated. A technique for efficient laser frequency conversion in a microscopic NLC volume deposited on an optical fibre end face is experimentally demonstrated. An efficient design of a compact NLC-based IR frequency converter with a fibre input and achromatic collimator is proposed and implemented. Simultaneous generation of the second and third harmonics is obtained for the first time under pumping NLC by a 1.56-mm femtosecond fibre laser. The second-harmonic generation efficiency is measured to be about 1 %, while the efficiency of third-harmonic generation is several tenths of percent. A strong polarisation dependence of the third-harmonic generation efficiency is revealed. When pumping NLC by a cw laser, generation of spectral supercontinua (covering the visible and near-IR spectral ranges) is observed. The nonlinear effects revealed can be due to the light-induced change in the orientational order in liquid crystals, which breaks the initial symmetry and leads to formation of disclination structures. The NLC optical nonlinearity is believed to be of mixed orientationalelectronic nature as a whole. (laser optics 2012)

  15. A nonlinear acoustic metamaterial: Realization of a backwards-traveling second-harmonic sound wave.

    PubMed

    Quan, Li; Qian, Feng; Liu, Xiaozhou; Gong, Xiufen

    2016-06-01

    An ordinary waveguide with periodic vibration plates and side holes can realize an acoustic metamaterial that simultaneously possesses a negative bulk modulus and a negative mass density. The study is further extended to a nonlinear case and it is predicted that a backwards-traveling second-harmonic sound wave can be obtained through the nonlinear propagation of a sound wave in such a metamaterial.

  16. A nonlinear acoustic metamaterial: Realization of a backwards-traveling second-harmonic sound wave.

    PubMed

    Quan, Li; Qian, Feng; Liu, Xiaozhou; Gong, Xiufen

    2016-06-01

    An ordinary waveguide with periodic vibration plates and side holes can realize an acoustic metamaterial that simultaneously possesses a negative bulk modulus and a negative mass density. The study is further extended to a nonlinear case and it is predicted that a backwards-traveling second-harmonic sound wave can be obtained through the nonlinear propagation of a sound wave in such a metamaterial. PMID:27369164

  17. A microchip laser with intracavity second-harmonic generation

    SciTech Connect

    Derzhavin, S I; Mashkovskii, D A; Timoshkin, V N

    2008-12-31

    A short-pulse 'green' 532-nm Nd{sup 3+}:YVO{sub 4} and KTiOPO{sub 4} microchip laser with intracavity second-harmonic generation, which is pumped by a 809-nm semiconductor laser diode, is developed. (lasers. amplifiers)

  18. Imaging Collagen Orientation Using Polarization-Modulated Second Harmonic Generation

    SciTech Connect

    Stoller, P; Celliers, P M; Reiser, K M; Rubenchik, A M

    2002-01-10

    We use polarization-modulated second harmonic generation to image fiber orientation in collagen tissues, with an axial resolution of about 10 {micro}m and a transverse resolution of up to 1 {micro}m. A linearly polarized ultra-short pulse (200 fs) Ti:Sapphire laser beam is modulated using an electro-optic modulator and quarter-wave plate combination and focused onto a translation stage mounted sample using a microscope objective. The generated second harmonic light is collected using a photomultiplier tube and demodulated using phase sensitive detection to obtain signal intensity and fiber orientation information. In order to obtain second harmonic generation images of different types of collagen organization, we analyze several different tissues, including rat-tail tendon, mouse aorta, mouse fibrotic liver, and porcine skin. We can use our technique to image fibrotic tissue in histological sections of damaged liver and to identify burned tissue in porcine skin to a depth of a few hundred microns. Polarization-modulated second harmonic generation potentially could be a useful clinical technique for diagnosing collagen related disease or damage, especially in the skin.

  19. Modulation compression for short wavelength harmonic generation

    SciTech Connect

    Qiang, J.

    2010-01-11

    Laser modulator is used to seed free electron lasers. In this paper, we propose a scheme to compress the initial laser modulation in the longitudinal phase space by using two opposite sign bunch compressors and two opposite sign energy chirpers. This scheme could potentially reduce the initial modulation wavelength by a factor of C and increase the energy modulation amplitude by a factor of C, where C is the compression factor of the first bunch compressor. Such a compressed energy modulation can be directly used to generate short wavelength current modulation with a large bunching factor.

  20. Classical theory for second-harmonic generation from metallic nanoparticles

    SciTech Connect

    Zeng Yong; Liu Jinjie; Moloney, Jerome V.; Hoyer, Walter; Koch, Stephan W.

    2009-06-15

    In this paper, we develop a classical electrodynamic theory to study the optical nonlinearities of metallic nanoparticles. The quasi free electrons inside the metal are approximated as a classical Coulomb-interacting electron gas, and their motion under the excitation of an external electromagnetic field is described by the plasma equations. This theory is further tailored to study second-harmonic generation. Through detailed experiment-theory comparisons, we validate this classical theory as well as the associated numerical algorithm. It is demonstrated that our theory not only provides qualitative agreement with experiments but it also reproduces the overall strength of the experimentally observed second-harmonic signals.

  1. Effect of Structural Modification on Second Harmonic Generation in Collagen

    SciTech Connect

    Stoller, P C; Reiser, K M; Celliers, P M; Rubenchik, A M

    2003-04-04

    The effects of structural perturbation on second harmonic generation in collagen were investigated. Type I collagen fascicles obtained from rat tails were structurally modified by increasing nonenzymatic cross-linking, by thermal denaturation, by collagenase digestion, or by dehydration. Changes in polarization dependence were observed in the dehydrated samples. Surprisingly, no changes in polarization dependence were observed in highly crosslinked samples, despite significant alterations in packing structure. Complete thermal denaturation and collagenase digestion produced samples with no detectable second harmonic signal. Prior to loss of signal, no change in polarization dependence was observed in partially heated or digested collagen.

  2. Microscopic approach to second harmonic generation in quantum cascade lasers.

    PubMed

    Winge, David O; Lindskog, Martin; Wacker, Andreas

    2014-07-28

    Second harmonic generation is analyzed from a microscopical point of view using a non-equilibrium Green's function formalism. Through this approach the complete on-state of the laser can be modeled and results are compared to experiment with good agreement. In addition, higher order current response is extracted from the calculations and together with waveguide properties, these currents provide the intensity of the second harmonic in the structure considered. This power is compared to experimental results, also with good agreement. Furthermore, our results, which contain all coherences in the system, allow to check the validity of common simplified expressions.

  3. High-order harmonic generation in a capillary discharge

    DOEpatents

    Rocca, Jorge J.; Kapteyn, Henry C.; Mumane, Margaret M.; Gaudiosi, David; Grisham, Michael E.; Popmintchev, Tenio V.; Reagan, Brendan A.

    2010-06-01

    A pre-ionized medium created by a capillary discharge results in more efficient use of laser energy in high-order harmonic generation (HHG) from ions. It extends the cutoff photon energy, and reduces the distortion of the laser pulse as it propagates down the waveguide. The observed enhancements result from a combination of reduced ionization energy loss and reduced ionization-induced defocusing of the driving laser as well as waveguiding of the driving laser pulse. The discharge plasma also provides a means to spectrally tune the harmonics by tailoring the initial level of ionization of the medium.

  4. Tomography of high harmonic generation in a cluster jet.

    PubMed

    Pai, Chih-Hao; Kuo, Cheng-Cheng; Lin, Ming-Wei; Wang, Jyhpyng; Chen, Szu-yuan; Lin, Jiunn-Yuan

    2006-04-01

    Tomographic measurement of high harmonic generation in a cluster jet was demonstrated by programming the cluster density distribution with a laser machining technique. The growth of harmonic energy with the propagation of the pump pulse was resolved by scanning the end of the argon cluster distribution in the path of the pump pulse. A downstream shift of the position of rapid growth and a decrease of the slope with increasing backing pressure as results of changes in the phase-matching condition were observed, which explains the presence of an optimal backing pressure. PMID:16599232

  5. Echo-enabled Harmonic Generation Free Electron Laser

    SciTech Connect

    Xiang, D; Stupakov, G.; /SLAC

    2008-12-18

    In this paper, we systematically study the echo-enabled harmonic generation (EEHG) free electron laser (FEL). The EEHG FEL uses two modulators in combination with two dispersion sections that allow to generate in the beam a high harmonic density modulation starting with a relatively small initial energy modulation of the beam. After presenting analytical theory of the phenomenon, we address several practically important issues, such as the effect of incoherent synchrotron radiation in the dispersion sections, and the beam transverse size effect in the modulator. Using a representative realistic set of beam parameters, we show how the EEHG scheme enhances the FEL performance and allows to generate a fully (both longitudinally and transversely) coherent radiation. As an example, we demonstrate that 5 nm coherent soft x-rays with GW peak power can be generated directly from the 240 nm seeding laser using the proposed EEHG scheme.

  6. Optical excitation of narrowband Rayleigh surface waves for second harmonic generation

    NASA Astrophysics Data System (ADS)

    Swacek, C. B.; Kim, J.-Y.; Jacobs, L. J.

    2013-01-01

    Conventional fluid-coupled contact ultrasonic methods suffer from large variability, which is known to originate from a number of sources such as the coupling variation and the surface roughness at the transducer/specimen interface. The inherently small higherharmonic signals can be significantly influenced by these changes in contact conditions, especially in nonlinear ultrasonic measurements. For this reason, the noncontact generation and detection techniques are very attractive. This research first focuses on the noncontact optical generation of tone-burst surface acoustic wave signals in a metallic specimen. Two methods that use laser light as an optical source are compared for generating surface acoustics waves in 5 MHz range. Both the shadow mask and diffraction grating are used to convert the circular laser beam into a periodic excitation pattern on the specimen. The generated signals are detected by a wedge transducer at a fixed location while the location of the excitation is varied. Then the harmonic contents in the generated signals and the repeatability of the methods are evaluated. Finally, the developed method is used to characterize the acoustic nonlinearity of aluminum (Al 6061) and steel (A36). The results on the aluminum samples show that the measurements based on the shadow mask excitation are repeatable in the ablative regime.

  7. Transmit beamforming for optimal second-harmonic generation.

    PubMed

    Hoilund-Kaupang, Halvard; Masoy, Svein-Erik

    2011-08-01

    A simulation study of transmit ultrasound beams from several transducer configurations is conducted to compare second-harmonic imaging at 3.5 MHz and 11 MHz. Second- harmonic generation and the ability to suppress near field echoes are compared. Each transducer configuration is defined by a chosen f-number and focal depth, and the transmit pressure is estimated to not exceed a mechanical index of 1.2. The medium resembles homogeneous muscle tissue with nonlinear elasticity and power-law attenuation. To improve computational efficiency, the KZK equation is utilized, and all transducers are circular-symmetric. Previous literature shows that second-harmonic generation is proportional to the square of the transmit pressure, and that transducer configurations with different transmit frequencies, but equal aperture and focal depth in terms of wavelengths, generate identical second-harmonic fields in terms of shape. Results verify this for a medium with attenuation f1. For attenuation f1.1, deviations are found, and the high frequency subsequently performs worse than the low frequency. The results suggest that high frequencies are less able to suppress near-field echoes in the presence of a heterogeneous body wall than low frequencies.

  8. Evidence of high harmonics from echo-enabled harmonic generation for seeding x-ray free electron lasers.

    PubMed

    Xiang, D; Colby, E; Dunning, M; Gilevich, S; Hast, C; Jobe, K; McCormick, D; Nelson, J; Raubenheimer, T O; Soong, K; Stupakov, G; Szalata, Z; Walz, D; Weathersby, S; Woodley, M

    2012-01-13

    Echo-enabled harmonic generation free electron lasers hold great promise for the generation of fully coherent radiation in x-ray wavelengths. Here we report the first evidence of high harmonics from the echo-enabled harmonic generation technique in the realistic scenario where the laser energy modulation is comparable to the beam slice energy spread. In this experiment, coherent radiation at the seventh harmonic of the second seed laser is generated when the energy modulation amplitude is about 2-3 times the slice energy spread. The experiment confirms the underlying physics of echo-enabled harmonic generation and may have a strong impact on emerging seeded x-ray free electron lasers that are capable of generating laserlike x rays which will advance many areas of science.

  9. Evidence of High Harmonics from Echo-Enabled Harmonic Generation for Seeding X-ray Free Electron Lasers

    SciTech Connect

    Xiang, D.; Colby, E.; Dunning, M.; Gilevich, S.; Hast, C.; Jobe, K.; McCormick, D.; Nelson, J.; Raubenheimer, T.O.; Soong, K.; Stupakov, G.; Szalata, Z.; Walz, D.; Weathersby, S.; Woodle, M.; /SLAC

    2012-02-15

    Echo-enabled harmonic generation free electron lasers hold great promise for the generation of fully coherent radiation in x-ray wavelengths. Here we report the first evidence of high harmonics from the echo-enabled harmonic generation technique in the realistic scenario where the laser energy modulation is comparable to the beam slice energy spread. In this experiment, coherent radiation at the seventh harmonic of the second seed laser is generated when the energy modulation amplitude is about 2-3 times the slice energy spread. The experiment confirms the underlying physics of echo-enabled harmonic generation and may have a strong impact on emerging seeded x-ray free electron lasers that are capable of generating laserlike x rays which will advance many areas of science.

  10. Self-Excitation and Harmonics in Wind Power Generation

    SciTech Connect

    Muljadi, E.; Butterfield, C. P.; Romanowitz, H.; Yinger, R.

    2005-11-01

    Traditional wind turbines are commonly equipped with induction generators because they are inexpensive, rugged, and require very little maintenance. Unfortunately, induction generators require reactive power from the grid to operate; capacitor compensation is often used. Because the level of required reactive power varies with the output power, the capacitor compensation must be adjusted as the output power varies. The interactions among the wind turbine, the power network, and the capacitor compensation are important aspects of wind generation that may result in self-excitation and higher harmonic content in the output current. This paper examines the factors that control these phenomena and gives some guidelines on how they can be controlled or eliminated.

  11. Enhancement of Focused Ultrasound Treatment by Acoustically Generated Microbubbles

    NASA Astrophysics Data System (ADS)

    Umemura, Shin-ichiro; Yoshizawa, Shin; Takagi, Ryo; Inaba, Yuta; Yasuda, Jun

    2013-07-01

    Microbubbles, whether introduced from outside the body or ultrasonically generated in situ, are known to significantly enhance the biological effects of ultrasound, including the mechanical, thermal, and sonochemical effects. Phase-change nanodroplets, which selectively accumulate in tumor tissue and whose phase changes to microbubbles can be induced by ultrasonic stimulation, have been proposed for high-intensity focused ultrasound (HIFU) tumor treatment with enhanced selectivity and efficiency. In this paper, a purely acoustic approach to generate microbubble clouds in the tissue to be treated is proposed. Short pulses of focused ultrasound with extremely high intensity, named trigger pulses, are used for exposure. They are immediately followed by focused ultrasound for heating with an intensity similar to or less than that of normal HIFU treatment. The localized generation of microbubble clouds by the trigger pulses is observed in a polyarylamide gel by a high-speed camera, and the effectiveness of the generated clouds in accelerating ultrasonically induced thermal coagulation is confirmed in excised chicken breast tissue. The use of second-harmonic superimposed waves as the trigger pulses is also proposed. The highly reproducible initiation of cavitation by waves with the negative peak pressure emphasized and the efficient expansion of the generated microbubble clouds by waves with the positive peak pressure emphasized are also observed by a high-speed camera in partially degassed water.

  12. Second harmonic generation and enhancement in microfibers and loop resonators

    NASA Astrophysics Data System (ADS)

    Gouveia, Marcelo A.; Lee, Timothy; Ismaeel, Rand; Ding, Ming; Broderick, Neil G. R.; Cordeiro, Cristiano M. B.; Brambilla, Gilberto

    2013-05-01

    We model and experimentally investigate second harmonic generation in silica microfibers and loop resonators, in which the second order nonlinearity arises from the glass-air surface dipole and bulk multipole contributions. In the loop resonator, the recirculation of the pump light on resonance is used to increase the conversion. The effect of the loop parameters, such as coupling and loss, is theoretically studied to determine their influence on the resonance enhancement. Experimentally, microfibers were fabricated with diameters around 0.7 μm to generate the intermodally phase matched second harmonic with an efficiency up to 4.2 × 10-8 when pumped with 5 ns 1.55 μm pulses with a peak power of 90 W. After reconfiguring the microfiber into a 1 mm diameter loop, the efficiency was resonantly enhanced by 5.7 times.

  13. Enhanced Harmonic Generation via Breaking of Phase-Matching Symmetry

    NASA Astrophysics Data System (ADS)

    Sergan, Ekaterina; Gibson, George

    2016-05-01

    We discuss experimental results of third harmonic generation (THG) with a focused Gaussian beam in the semi-infinite limit, using two methods. The first method involves placing a metal septum at the waist such that the laser drills a small pinhole, which in turn disrupts the beam after the waist. The second method uses a very thin septum as a separator for two gasses: one with a large third order susceptibility (before the focus), and the other with a small susceptibility (after the focus). Both methods inhibit harmonic generation immediately after the beam waist, leading to increased conversion efficiency and better mode quality. Our work involves studies of conversion efficiency with varying septum thickness and gas pressure, and the results are compared to computer simulations. We would like to acknowledge support from the NSF under Grant No. PHY-1306845.

  14. Continuous third harmonic generation in a terahertz driven modulated nanowire

    NASA Astrophysics Data System (ADS)

    Hamilton, Kathleen E.; Kovalev, Alexey A.; De, Amrit; Pryadko, Leonid P.

    2015-06-01

    We consider the possibility of observing continuous third-harmonic generation using a strongly driven, single-band one-dimensional metal. In the absence of scattering, the quantum efficiency of frequency tripling for such a system can be as high as 93%. Combining the Floquet quasi-energy spectrum with the Keldysh Green's function technique, we derive a semiclassical master equation for a one-dimensional band of strongly and rapidly driven electrons in the presence of weak scattering by phonons. The power absorbed from the driving field is continuously dissipated by phonon modes, leading to a quasi-equilibrium in the electron distribution. We use the Kronig-Penney model with varying effective mass to establish the growth parameters of an InAs/InP nanowire near optimal for third harmonic generation at terahertz frequency range.

  15. Continuous third harmonic generation in a terahertz driven modulated nanowire

    SciTech Connect

    Hamilton, Kathleen E. De, Amrit; Pryadko, Leonid P.; Kovalev, Alexey A.

    2015-06-07

    We consider the possibility of observing continuous third-harmonic generation using a strongly driven, single-band one-dimensional metal. In the absence of scattering, the quantum efficiency of frequency tripling for such a system can be as high as 93%. Combining the Floquet quasi-energy spectrum with the Keldysh Green's function technique, we derive a semiclassical master equation for a one-dimensional band of strongly and rapidly driven electrons in the presence of weak scattering by phonons. The power absorbed from the driving field is continuously dissipated by phonon modes, leading to a quasi-equilibrium in the electron distribution. We use the Kronig-Penney model with varying effective mass to establish the growth parameters of an InAs/InP nanowire near optimal for third harmonic generation at terahertz frequency range.

  16. Corneal imaging by second and third harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Brocas, Arnaud; Jay, Louis; Mottay, Eric; Brunette, Isabelle; Ozaki, Tsuneyuki

    2008-02-01

    Advanced imaging methods are essential tools for improved outcome of refractive surgery. Second harmonic generation (SHG) and third harmonic generation (THG) microscopy are noninvasive high-resolution imaging methods, which can discriminate the different layers of the cornea, thus having strong impact on the outcome of laser surgery. In this work, we use an Ytterbium femtosecond laser as the laser source, the longer wavelength of which reduces scattering, and allows simultaneous SHG and THG imaging. We present SHG and THG images and profiles of pig corneas that clearly show the anterior surface of the cornea, the entry in the stroma and its end, and the posterior surface of the cornea. These observations allow localizing the epithelium, the stroma and the endothelium. Other experiments give information about the structure and cytology of the corneal layers.

  17. Third harmonic generation in exposed-core microstructured optical fibers.

    PubMed

    Warren-Smith, Stephen C; Wie, Jingxuan; Chemnitz, Mario; Kostecki, Roman; Ebendorff-Heidepriem, Heike; Monro, Tanya M; Schmidt, Markus A

    2016-08-01

    Inter-modal phase-matched third harmonic generation has been demonstrated in an exposed-core microstructured optical fiber. Our fiber, with a partially open core having a diameter of just 1.85 µm, shows efficient multi-peak third-harmonic generation between 500 nm and 530 nm, with a maximum visible-wavelength output of 0.96 μW. Mode images and simulations show strong agreement, confirming the phase-matching process and polarization dependence. We anticipate this work will lead to tailorable and tunable visible light sources by exploiting the open access to the optical fiber core, such as depositing thin-film coatings in order to shift the phase matching conditions. PMID:27505753

  18. Vacuum high-harmonic generation in the shock regime

    NASA Astrophysics Data System (ADS)

    Böhl, P.; King, B.; Ruhl, H.

    2015-09-01

    Electrodynamics becomes nonlinear and permits the self-interaction of fields when the quantized nature of vacuum states is taken into account. The effect on a plane probe pulse propagating through a stronger constant crossed background is calculated using numerical simulation and by analytically solving the corresponding wave equation. The electromagnetic shock resulting from vacuum high-harmonic generation is investigated and a nonlinear shock parameter identified.

  19. High gain amplifiers: Power oscillations and harmonic generation

    SciTech Connect

    Dattoli, G.; Ottaviani, P. L.; Pagnutti, S.

    2007-08-01

    We discuss the power oscillations in saturated high gain free electron laser amplifiers and show that the relevant period can be written in terms of the gain length. We use simple arguments following from the solution of the pendulum equation in terms of Jacobi elliptic functions. Nontrivial effects due to nonlinear harmonic generation and inhomogeneous broadening are discussed too, as well as the saturated dynamics of short pulses.

  20. High harmonic generation from impulsively aligned SO2

    NASA Astrophysics Data System (ADS)

    Devin, Julien; Wang, Song; Kaldun, Andreas; Bucksbaum, Phil

    2016-05-01

    Previous work in high harmonics generation (HHG) in aligned molecular gases has mainly focused on rotational dynamics in order to determine the contributions of different orbitals to the ionization step. In our experiment, we focus on the shorter timescale of vibrational dynamics. We generate high harmonics from impulsively aligned SO2 molecules in a gas jet and record the emitted attosecond pulse trains in a home-built high resolution vacuum ultra violet (VUV) spectrometer. Using the high temporal resolution of our setup, we are able to map out the effects of vibrational wavepackets with a sub-femtosecond resolution. The target molecule, SO2 gas, is impulsively aligned by a near-infrared laser pulse and has accessible vibrations on the timescale of the short laser pulse used. We present first experimental results for the response to this excitation in high-harmonics. We observe both fast oscillations in the time domain as well as shifts of the VUV photon energy outside of the pulse overlaps. Research supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), Chemical Sciences, Geosciences, and Biosciences Division and by the National Science Foundation Graduate Research Fellowship.

  1. Higher harmonics generation in relativistic electron beam with virtual cathode

    SciTech Connect

    Kurkin, S. A. Badarin, A. A.; Koronovskii, A. A.; Hramov, A. E.

    2014-09-15

    The study of the microwave generation regimes with intense higher harmonics taking place in a high-power vircator consisting of a relativistic electron beam with a virtual cathode has been made. The characteristics of these regimes, in particular, the typical spectra and their variations with the change of the system parameters (beam current, the induction of external magnetic field) as well as physical processes occurring in the system have been analyzed by means of 3D electromagnetic simulation. It has been shown that the system under study demonstrates the tendency to the sufficient growth of the amplitudes of higher harmonics in the spectrum of current oscillations in the VC region with the increase of beam current. The obtained results allow us to consider virtual cathode oscillators as promising high power mmw-to-THz sources.

  2. Higher harmonics generation in relativistic electron beam with virtual cathode

    NASA Astrophysics Data System (ADS)

    Kurkin, S. A.; Badarin, A. A.; Koronovskii, A. A.; Hramov, A. E.

    2014-09-01

    The study of the microwave generation regimes with intense higher harmonics taking place in a high-power vircator consisting of a relativistic electron beam with a virtual cathode has been made. The characteristics of these regimes, in particular, the typical spectra and their variations with the change of the system parameters (beam current, the induction of external magnetic field) as well as physical processes occurring in the system have been analyzed by means of 3D electromagnetic simulation. It has been shown that the system under study demonstrates the tendency to the sufficient growth of the amplitudes of higher harmonics in the spectrum of current oscillations in the VC region with the increase of beam current. The obtained results allow us to consider virtual cathode oscillators as promising high power mmw-to-THz sources.

  3. Electric field induced second harmonic generation with and without fringes

    NASA Astrophysics Data System (ADS)

    Meshulam, G.; Berkovic, G.; Kotler, Z.; Sa'ar, A.

    2000-09-01

    Electric field induced second harmonic generation (EFISH) is a well-known technique to measure the first hyperpolarizability (β) of organic molecules in solution. The characteristic experimental output is observation of oscillatory fringes of second harmonic radiation as the solution path length is changed and evaluation of β from the fringe amplitude. We present two different cases where even in the absence of these characteristic fringes β may still be evaluated: first, when using absorbing materials, and second, when using broadband laser sources. The ability to determine β by EFISH under these conditions greatly enhances the ability of this technique to measure β values over a wide range of laser frequencies. Measurements of the same molecule's β values at different frequencies are reported, verifying the two-level model for the dispersion of β.

  4. Switching between seismic and seismo-acoustic harmonic tremor simulated in the laboratory: Insights into the role of open degassing channels and magma viscosity

    NASA Astrophysics Data System (ADS)

    Lyons, John J.; Ichihara, Mie; Kurokawa, Aika; Lees, Jonathan M.

    2013-01-01

    AbstractSwitching between seismic-only <span class="hlt">harmonic</span> tremor (SHT) and seismo-<span class="hlt">acoustic</span> <span class="hlt">harmonic</span> tremor (SAHT) has been reported at few volcanoes worldwide, but its occurrence may indicate important changes in shallow conduit conditions. Switching was simulated in a laboratory experiment in which <span class="hlt">harmonic</span> signals were produced with a flow-driven valve and compressed air. The <span class="hlt">harmonic</span> signals were passed through a tank of shear-thinning viscoelastic fluid, and the resulting signals were recorded. At high fluid stiffness, a stable, open conduit was produced, and the <span class="hlt">harmonic</span> signals <span class="hlt">generated</span> within the experimental apparatus were efficiently transmitted into the atmosphere. At lower fluid stiffness, bubbling dominated the activity, stable pathways were not <span class="hlt">generated</span> in the fluid, and HT was not recorded in the atmosphere. These results are compared to observations of switching at Fuego volcano, Guatemala. We conclude that at intermediate magma viscosities, the development of stable degassing pathways open to the atmosphere will allow HT <span class="hlt">generated</span> in the conduit to be transmitted into the atmosphere. Further, subtle changes in magma properties and supply rate may control whether SHT or SAHT is recorded, providing information about the state of the shallow conduit and vent at active volcanoes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1014128','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1014128"><span id="translatedtitle">Echo-Enabled <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> for Seeded FELs</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Stupakov, G.; /SLAC</p> <p>2011-05-19</p> <p>In the x-ray wavelengths, the two leading FEL concepts are the self-amplified spontaneous emission (SASE) configuration and the high-gain <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HGHG) scheme. While the radiation from a SASE FEL is coherent transversely, it typically has rather limited temporal coherence. Alternatively, the HGHG scheme allows <span class="hlt">generation</span> of fully coherent radiation by up-converting the frequency of a high-power seed laser. However, due to the relatively low up-frequency conversion efficiency, multiple stages of HGHG FEL are needed in order to <span class="hlt">generate</span> x-rays from a UV laser. The up-frequency conversion efficiency can be greatly improved with the recently proposed echo-enabled <span class="hlt">harmonic</span> <span class="hlt">generation</span> (EEHG) technique. In this work we will present the concept of EEHG, and address some practically important issues that affect the performance of the seeding. We show how the EEHG can be incorporated in the FEL scheme and what is the expected performance of the EEHG seeded FEL. We will then briefly describe the first proof-of-principle EEHG experiment carried out at the Next Linear Collider Test Accelerator (NLCTA) at SLAC. We will also discuss latest advances in the echo-scheme approach, and refer to subsequent modifications of the original concept.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPlPh..82b6502B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPlPh..82b6502B"><span id="translatedtitle">Vacuum high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> and electromagnetic shock</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Böhl, P.; King, B.; Ruhl, H.</p> <p>2016-04-01</p> <p>> When one takes into account the presence of virtual charged states in the quantum vacuum, a nonlinear self-interaction can arise in the propagation of electromagnetic fields. This self-interaction is often referred to as `real photon-photon scattering'. When the centre-of-mass energy of colliding photons is much lower than the rest energy of an electron-positron pair, this quantum effect can be included in the classical field equations of motion as a vacuum current and charge density using the Heisenberg-Euler Lagrangian. Using analytical and numerical methods for subcritical fields, the intrinsic solution to Maxwell's equations has been found for counterpropagating probe and pump plane waves in the presence of vacuum four- and six-wave mixing. In the corresponding all-order solution for the scattered probe, a route to vacuum high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> is identified in which a long phase length can compensate for the weakness of interacting fields. The resulting shocks in the probe carrier wave and envelope are studied for different parameter regimes and polarisation set-ups. In this special issue, we study two additional set-ups: that of a slowly varying single-cycle background to highlight the effect of an oscillating background on the probe <span class="hlt">harmonic</span> spectrum, and that of a few-cycle probe to highlight the smoothing of the <span class="hlt">harmonic</span> peaks produced by a wider spectrum of probe photons. We also correct sign errors in an earlier publication.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016APS..MARX17012L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016APS..MARX17012L&link_type=ABSTRACT"><span id="translatedtitle">High-<span class="hlt">harmonic</span> <span class="hlt">generation</span> from an atomically thin semiconductor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Hanzhe; Li, Yilei; Ghimire, Shambhu; Heinz, Tony; Reis, David</p> <p></p> <p>The process of high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) from ultrashort laser pulses has recently been observed in bulk solids, complementing the well-established process in the gas phase. HHG is of interest both as a source of ultrashort pulses in the attosecond regime that has photon energies extending up to the soft x-ray region and as a method of probing material response outside the regime of perturbative nonlinear optics. In this paper, we present the observation of HHG from a single atomic layer of MoS2 driven by a strong infrared pulse of 100 fs duration and 0.3 eV photon energy. We observe distinct <span class="hlt">harmonics</span> up to the 13th order of the infrared excitation. The non-perturbative nature of the HHG process is demonstrated by the weak power dependence of the <span class="hlt">harmonic</span> intensities. To gain further insight into the process, we have investigated the variation of the HHG signal with sample orientation and the ellipticity of pump excitation. We compare and contrast the process with that from the bulk MoS2 crystal. We find significant differences in the response for the monolayer and bulk crystal, which can be understood in terms of the distinct crystallographic symmetries in the two cases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRF..120.2027T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRF..120.2027T"><span id="translatedtitle"><span class="hlt">Acoustic</span> signals <span class="hlt">generated</span> in inclined granular flows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tan, Danielle S.; Jenkins, James T.; Keast, Stephen C.; Sachse, Wolfgang H.</p> <p>2015-10-01</p> <p>Spontaneous avalanching in specific deserts produces a low-frequency sound known as "booming." This creates a puzzle, because avalanches down the face of a dune result in collisions between sand grains that occur at much higher frequencies. Reproducing this phenomenon in the laboratory permits a better understanding of the underlying mechanisms for the <span class="hlt">generation</span> of such lower frequency <span class="hlt">acoustic</span> emissions, which may also be relevant to other dry granular flows. Here we report measurements of low-frequency <span class="hlt">acoustical</span> signals, produced by dried "sounding" sand (sand capable of booming in the desert) flowing down an inclined chute. The amplitude of the signal diminishes over time but reappears upon drying of the sand. We show that the presence of this sound in the experiments may provide supporting evidence for a previously published "waveguide" explanation for booming. Also, we propose a model based on kinetic theory for a sheared inclined flow in which the flowing layer exhibits "breathing" modes superimposed on steady shearing. The predicted oscillation frequency is of a similar order of magnitude as the measurements, indicating that small perturbations can sustain oscillations of a low frequency. However, the frequency is underestimated, which indicates that the stiffness has been underestimated. Also, the model predicts a discrete spectrum of frequencies, instead of the broadband spectrum measured experimentally.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22492371','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22492371"><span id="translatedtitle">Significance of accurate diffraction corrections for the second <span class="hlt">harmonic</span> wave in determining the <span class="hlt">acoustic</span> nonlinearity parameter</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jeong, Hyunjo; Zhang, Shuzeng; Li, Xiongbing; Barnard, Dan</p> <p>2015-09-15</p> <p>The accurate measurement of <span class="hlt">acoustic</span> nonlinearity parameter β for fluids or solids generally requires making corrections for diffraction effects due to finite size geometry of transmitter and receiver. These effects are well known in linear <span class="hlt">acoustics</span>, while those for second <span class="hlt">harmonic</span> waves have not been well addressed and therefore not properly considered in previous studies. In this work, we explicitly define the attenuation and diffraction corrections using the multi-Gaussian beam (MGB) equations which were developed from the quasilinear solutions of the KZK equation. The effects of making these corrections are examined through the simulation of β determination in water. Diffraction corrections are found to have more significant effects than attenuation corrections, and the β values of water can be estimated experimentally with less than 5% errors when the exact second <span class="hlt">harmonic</span> diffraction corrections are used together with the negligible attenuation correction effects on the basis of linear frequency dependence between attenuation coefficients, α{sub 2} ≃ 2α{sub 1}.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22271003','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22271003"><span id="translatedtitle"><span class="hlt">Acoustic</span> characterization of high intensity focused ultrasound fields <span class="hlt">generated</span> from a transmitter with a large aperture</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chen, Tao; Fan, Tingbo; Zhang, Wei; Qiu, Yuanyuan; Tu, Juan E-mail: dzhang@nju.edu.cn; Guo, Xiasheng; Zhang, Dong E-mail: dzhang@nju.edu.cn</p> <p>2014-03-21</p> <p>Prediction and measurement of the <span class="hlt">acoustic</span> field emitted from a high intensity focused ultrasound (HIFU) is essential for the accurate ultrasonic treatment. In this study, the <span class="hlt">acoustic</span> field <span class="hlt">generated</span> from a strongly focused HIFU transmitter was characterized by a combined experiment and simulation method. The spheroidal beam equation (SBE) was utilized to describe the nonlinear sound propagation. The curve of the source pressure amplitude versus voltage excitation was determined by fitting the measured ratio of the second <span class="hlt">harmonic</span> to the fundamental component of the focal waveform to the simulation result; finally, the <span class="hlt">acoustic</span> pressure field <span class="hlt">generated</span> by the strongly focused HIFU transmitter was predicted by using the SBE model. A commercial fiber optic probe hydrophone was utilized to measure the <span class="hlt">acoustic</span> pressure field <span class="hlt">generated</span> from a 1.1 MHz HIFU transmitter with a large half aperture angle of 30°. The maximum measured peak-to-peak pressure was up to 72 MPa. The validity of this combined approach was confirmed by the comparison between the measured results and the calculated ones. The results indicate that the current approach might be useful to describe the HIFU field. The results also suggest that this method is not valid for low excitations owing to low sensitivity of the second <span class="hlt">harmonic</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1018525','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1018525"><span id="translatedtitle">High <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> from Multiple Orbitals in N2</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>McFarland, B.; Farrell, Joseph P.; Bucksbaum, Philip H.; Guehr, Markus; /SLAC, Pulse /Stanford U., Phys. Dept.</p> <p>2009-03-05</p> <p>Molecular electronic states energetically below the highest occupied molecular orbital (HOMO) should contribute to laser-driven high <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG), but this behavior has not been observed previously. Our measurements of the HHG spectrum of N{sub 2} molecules aligned perpendicular to the laser polarization showed a maximum at the rotational half-revival. This feature indicates the influence of electrons occupying the orbital just below the N{sub 2} HOMO, referred to as the HOMO-1. Such observations of lower-lying orbitals are essential to understanding subfemtosecond/subangstrom electronic motion in laser-excited molecules.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/921645','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/921645"><span id="translatedtitle">STARS A Two Stage High Gain <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> FEL Demonstrator</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>M. Abo-Bakr; W. Anders; J. Bahrdt; P. Budz; K.B. Buerkmann-Gehrlein; O. Dressler; H.A. Duerr; V. Duerr; W. Eberhardt; S. Eisebitt; J. Feikes; R. Follath; A. Gaupp; R. Goergen; K. Goldammer; S.C. Hessler; K. Holldack; E. Jaeschke; Thorsten Kamps; S. Klauke; J. Knobloch; O. Kugeler; B.C. Kuske; P. Kuske; A. Meseck; R. Mitzner; R. Mueller; M. Neeb; A. Neumann; K. Ott; D. Pfluckhahn; T. Quast; M. Scheer; Th. Schroeter; M. Schuster; F. Senf; G. Wuestefeld; D. Kramer; Frank Marhauser</p> <p>2007-08-01</p> <p>BESSY is proposing a demonstration facility, called STARS, for a two-stage high-gain <span class="hlt">harmonic</span> <span class="hlt">generation</span> free electron laser (HGHG FEL). STARS is planned for lasing in the wavelength range 40 to 70 nm, requiring a beam energy of 325 MeV. The facility consists of a normal conducting gun, three superconducting TESLA-type acceleration modules modified for CW operation, a single stage bunch compressor and finally a two-stage HGHG cascaded FEL. This paper describes the faciliy layout and the rationale behind the operation parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/427753','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/427753"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> from multilayers of oriented metal bisphosphonates</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Neff, G.A.; Mahon, T.M.; Abshere, T.A.; Page, C.J.</p> <p>1996-12-31</p> <p>Second order nonlinear optical properties (NLO) require the presence of a polarizable moiety situated in an anharmonic potential. The approach to incorporating such properties into self-assembled multilayers involves use of asymmetric {alpha},{omega} bisphosphonates which meet this requirement by virtue of their chemical structure and binding properties. The authors have developed and optimized protection and deprotection schemes to allow for oriented layering of these molecules. Characterization by optical ellipsometry and grazing angle X-ray diffraction provides insight on average layer thicknesses and bulk film densities. Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) intensity from the bulk film is measured to verify NLO activity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19550522','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19550522"><span id="translatedtitle">Analytic scaling analysis of high <span class="hlt">harmonic</span> <span class="hlt">generation</span> conversion efficiency.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Falcão-Filho, E L; Gkortsas, M; Gordon, Ariel; Kärtner, Franz X</p> <p>2009-06-22</p> <p>Closed form expressions for the high <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) conversion efficiency are obtained for the plateau and cutoff regions. The presented formulas eliminate most of the computational complexity related to HHG simulations, and enable a detailed scaling analysis of HHG efficiency as a function of drive laser parameters and material properties. Moreover, in the total absence of any fitting procedure, the results show excellent agreement with experimental data reported in the literature. Thus, this paper opens new pathways for the global optimization problem of extreme ultraviolet (EUV) sources based on HHG.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991JCrGr.108..688G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991JCrGr.108..688G"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> and crystal growth of substituted thienyl chalcone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goto, Yoshitaka; Hayashi, Akio; Kimura, Yasuhiro; Nakayama, Masaharu</p> <p>1991-02-01</p> <p>The second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) of 29 kinds of thienyl chalcone derivatives with a thiophene ring were examined. A series of 1-{2-(5-bromothienyl)}-3-(4'-halophenyl)propene-3-one showed high SHG activity. Especially 1-(2-thienyl)-3-(4-methylphenyl)propene-1-one had SHG activity 15 times as large as urea and also high blue light region transparency with a cutoff wavelength of 390 nm. A large high quality single crystal of 60x15x10mm of this compound could be obtained from acetone solution. Analysis of the crystal structure identified it as a monoclinical system of space group P2 1.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvB..91f4302V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvB..91f4302V"><span id="translatedtitle">Semiclassical analysis of high <span class="hlt">harmonic</span> <span class="hlt">generation</span> in bulk crystals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vampa, G.; McDonald, C. R.; Orlando, G.; Corkum, P. B.; Brabec, T.</p> <p>2015-02-01</p> <p>High <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) in solids is investigated. We find that interband emission is dominant for the midinfrared laser driver frequencies, whereas intraband emission dominates the far-infrared range. Interband HHG is similar to atomic HHG and therewith opens the possibility to apply atomic attosecond technology to the condensed matter phase. Interband emission is investigated with a quasiclassical method, by which HHG can be modeled based on the classical trajectory analysis of electron-hole pairs. This analysis yields a simple approximate cutoff law for HHG in solids. Differences between HHG in atoms and solids are identified that are important for adapting atomic attosecond technology to make it applicable to condensed matter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DMP.P7008H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DMP.P7008H"><span id="translatedtitle">Correlated Terahertz and High <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> from Aligned Nitrogen Molecules</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, Yindong; Meng, Chao; Wang, Xiaowei; Lv, Zhihui; Zhang, Dongwen; Chen, Wenbo; Zhao, Jing; Yuan, Jianmin; Zhao, Zengxiu</p> <p>2016-05-01</p> <p>When laser beams are focused on atoms and molecules, wide spectral range of photons can be radiated from the source. In the region of high energy, high <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG), covering tens to hundreds electron volts, emit within the attosecond timescale. In the low energy region, terahertz wave <span class="hlt">generation</span> (TWG) can also be <span class="hlt">generated</span>. Synchronizing TWG with HHG is to take snapshot of the electronic dynamics with time-scale spanning over 6 orders of magnitudes. In this abstract, we report the joint measurements on TWG and HHG from pre-aligned molecules. By calibrating the angular ionization rates with the alignment dependent TWG, we reconstruct the photoionization cross section (PICS) of nitrogen in one run of experiment. The measured PICS is found to be consistent with theoretical predications, although some discrepancies exist. This all-optical method provides a new alternative for investigating molecular structures (Yindong Huang et al., Phys. Rev. Lett. 115, 123002, 2015).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhL.108w1102L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhL.108w1102L"><span id="translatedtitle">Polarization gating of high <span class="hlt">harmonic</span> <span class="hlt">generation</span> in the water window</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Jie; Ren, Xiaoming; Yin, Yanchun; Cheng, Yan; Cunningham, Eric; Wu, Yi; Chang, Zenghu</p> <p>2016-06-01</p> <p>We implement the polarization gating (PG) technique with a two-cycle, 1.7 μm driving field to <span class="hlt">generate</span> an attosecond supercontinuum extending to the water window spectral region. The ellipticity dependence of the high <span class="hlt">harmonic</span> yield over a photon energy range much broader than previous work is measured and compared with a semi-classical model. When PG is applied, the carrier-envelope phase (CEP) is swept to study its influence on the continuum <span class="hlt">generation</span>. PG with one-cycle (5.7 fs) and two-cycle (11.3 fs) delay are tested, and both give continuous spectra spanning from 50 to 450 eV under certain CEP values, strongly indicating the <span class="hlt">generation</span> of isolated attosecond pulses in the water window region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JMOp...58.1404P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JMOp...58.1404P"><span id="translatedtitle">Designs and numerical calculations for echo-enabled <span class="hlt">harmonic</span> <span class="hlt">generation</span> at very high <span class="hlt">harmonics</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Penn, G.; Reinsch, M.</p> <p>2011-09-01</p> <p>The echo-enabled <span class="hlt">harmonic</span> <span class="hlt">generation</span> (EEHG) scheme for driving an FEL using two seeded energy modulations at much longer wavelengths than the output wavelength is a promising concept for future seeded FELs. There are many competing requirements in the design of an EEHG beamline which need careful optimization. Furthermore, revised simulation tools and methods are necessary because of both the high <span class="hlt">harmonic</span> numbers simulated and the complicated nature of the phase space manipulations which are intrinsic to the scheme. This paper explores the constraints on performance and the required tolerances for reaching wavelengths well below 1/100th of that of the seed lasers, and describes some of the methodology for designing such a beamline. Numerical tools, developed both for the GENESIS and GINGER FEL codes, are presented and used here for more accurate study of the scheme beyond a time-averaged model. In particular, the impact of the local structure in peak current and bunching, which is an inherent part of the EEHG scheme, is evaluated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/94246','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/94246"><span id="translatedtitle">The effects of <span class="hlt">harmonics</span> <span class="hlt">generated</span> by an over-excited transformer on a multimachine system</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jalali, J.; Mokhtari, S.</p> <p>1995-09-01</p> <p>An electric power system consisting of three <span class="hlt">generators</span> and nine buses is considered. The transformer connected to bus seven is considered as a source of <span class="hlt">harmonics</span>, and it is modeled accordingly. The <span class="hlt">harmonic</span> source <span class="hlt">generates</span> <span class="hlt">harmonics</span> with 6K {+-} 1 orders for K = 1, 2, 3 ..., n. The <span class="hlt">harmonics</span> of order 6K {+-} 1 with significant effects on different buses of the power system network are evaluated during the steady state operation of the system by using SKM System Software for HIWAVE. Frequency scan and distortion calculations are studied to determine how the <span class="hlt">harmonics</span> vary the operation of the power system network. The frequency spectrum of the <span class="hlt">harmonic</span> source indicates that 5th order <span class="hlt">harmonic</span> affects the operation of the power system. The effects of <span class="hlt">harmonics</span> on the system are reduced by modeling a single-tuned shunt filter connected to bus seven parallel to the <span class="hlt">harmonic</span> source to improve the system operation.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21518308','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21518308"><span id="translatedtitle">Pencil lead plasma for <span class="hlt">generating</span> multimicrojoule high-order <span class="hlt">harmonics</span> with a broad spectrum</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pertot, Y.; Elouga Bom, L. B.; Ozaki, T.; Bhardwaj, V. R.</p> <p>2011-03-07</p> <p>Using the plasma <span class="hlt">harmonic</span> method, we show the <span class="hlt">generation</span> of efficient and intense high-order <span class="hlt">harmonics</span> from plasma of pencil lead. We demonstrate multimicrojoule energy in each <span class="hlt">harmonic</span> order for the 11th to the 17th order of a Ti:sapphire laser. By analyzing the target morphology and the plasma composition, we conclude that these intense <span class="hlt">harmonics</span> are <span class="hlt">generated</span> from nanoparticles of graphitic carbon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080005938','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080005938"><span id="translatedtitle">Diode end pumped laser and <span class="hlt">harmonic</span> <span class="hlt">generator</span> using same</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Byer, Robert L. (Inventor); Dixon, George J. (Inventor); Kane, Thomas J. (Inventor)</p> <p>1988-01-01</p> <p>A second <span class="hlt">harmonic</span>, optical <span class="hlt">generator</span> is disclosed in which a laser diode produces an output pumping beam which is focused by means of a graded, refractive index rod lens into a rod of lasant material, such as Nd:YAG, disposed within an optical resonator to pump the lasant material and to excite the optical resonator at a fundamental wavelength. A non-linear electro-optic material such as MgO:LiNbO.sub.3 is coupled to the excited, fundamental mode of the optical resonator to produce a non-linear interaction with the fundamental wavelength producing a <span class="hlt">harmonic</span>. In one embodiment, the gain medium and the non-linear material are disposed within an optical resonator defined by a pair of reflectors, one of which is formed on a face of the gain medium and the second of which is formed on a face of the non-linear medium. In another embodiment, the non-linear, electro-optic material is doped with the lasant ion such that the gain medium and the non-linear doubling material are co-extensive in volume. In another embodiment, a non-linear, doubling material is disposed in an optical resonator external of the laser gai medium for improved stability of the second <span class="hlt">harmonic</span> <span class="hlt">generation</span> process. In another embodiment, the laser gain medium andthe non-linear material are bonded together by means of an optically transparent cement to form a mechanically stable, monolithic structure. In another embodiment, the non-linear material has reflective faces formed thereon to define a ring resonator to decouple reflections from the non-linear medium back to the gain medium for improved stability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DMP.Q1037W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DMP.Q1037W"><span id="translatedtitle">High-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in aligned water molecules</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Song; Devin, Julien; Hoffmann, Matthias; Cryan, James; Kaldun, Andreas; Bucksbaum, Philip</p> <p>2016-05-01</p> <p>In recent years, the use of high <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) in aligned molecular vapors has become a powerful tool to study ultrafast dynamics of electronic and nuclear wave packets. In our new experimental setup, we are able to orient H2 O and D2 O molecules using a single cycle terahertz (THz) pulse. Aligning water is especially interesting as the highest occupied molecular orbital (HOMO) of water contains a node in the xz plane of the molecular frame, allowing us to perform HHG from second highest occupied molecular orbital (HOMO-1) only, by setting the polarization of the fundamental laser along the z-axis of the aligned water molecules. We are particularly interested in the HOMO-1 state, as there is fast motion of the H-O-H angle leading to sub-wavelength dynamics. On this poster we present our all-optical alignment setup where HHG and single-cycle THz <span class="hlt">generation</span> take place in high-vacuum, where measurements with arbitrary polarization angles between the two are possible. In addition, we discuss the effects of the molecular orientation on HHG, including symmetry breaking that could produce even <span class="hlt">harmonics</span> and isotope effects between H2 O and D2 O due to different vibrational energies. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT.......139M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT.......139M"><span id="translatedtitle">Third <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> from Aligned Single-Wall Carbon Nanotubes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morris, Darius T., Jr.</p> <p></p> <p>Optical properties of single-wall carbon nanotubes (SWCNTs) have been extensively studied during the last decade, and much basic knowledge has been accumulated on how light emission, scattering, and absorption occur in the realm of linear optics. However, their nonlinear optical properties remain largely unexplored. Here, we have observed strong third <span class="hlt">harmonic</span> <span class="hlt">generation</span> from highly aligned SWCNTs with intense mid-infrared radiation. Through power dependent experiments, we have determined the absolute value of the third-order nonlinear optical susceptibility, chi(3), of our SWCNT film to be 6.92 x 10--12 esu, which is three orders of magnitude larger than that of the fused silica reference sample we used. Furthermore, through polarization-dependent third <span class="hlt">harmonic</span> <span class="hlt">generation</span> experiments, all the nonzero tensor elements of chi(3) have also been extracted. The contribution of the weaker tensor elements to the overall chi (3) signal has been calculated to be approximately 1/6 of that of the dominant c3z zzz component. These results open up new possibilities for application of carbon nanotubes in optoelectronics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25725724','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25725724"><span id="translatedtitle">Time-resolved phase-sensitive second <span class="hlt">harmonic</span> <span class="hlt">generation</span> spectroscopy.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nowakowski, Paweł J; Woods, David A; Bain, Colin D; Verlet, Jan R R</p> <p>2015-02-28</p> <p>A methodology based on time-resolved, phase-sensitive second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) for probing the excited state dynamics of species at interfaces is presented. It is based on an interference measurement between the SHG from the sample and a local oscillator <span class="hlt">generated</span> at a reference together with a lock-in measurement to remove the large constant offset from the interference. The technique is characterized by measuring the phase and excited state dynamics of the dye malachite green at the water/air interface. The key attributes of the technique are that the observed signal is directly proportional to sample concentration, in contrast to the quadratic dependence from non-phase sensitive SHG, and that the real and imaginary parts of the 2nd order non-linear susceptibility can be determined independently. We show that the method is highly sensitive and can provide high quality excited state dynamics in short data acquisition times. PMID:25725724</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JChPh.142h4201N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JChPh.142h4201N"><span id="translatedtitle">Time-resolved phase-sensitive second <span class="hlt">harmonic</span> <span class="hlt">generation</span> spectroscopy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nowakowski, Paweł J.; Woods, David A.; Bain, Colin D.; Verlet, Jan R. R.</p> <p>2015-02-01</p> <p>A methodology based on time-resolved, phase-sensitive second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) for probing the excited state dynamics of species at interfaces is presented. It is based on an interference measurement between the SHG from the sample and a local oscillator <span class="hlt">generated</span> at a reference together with a lock-in measurement to remove the large constant offset from the interference. The technique is characterized by measuring the phase and excited state dynamics of the dye malachite green at the water/air interface. The key attributes of the technique are that the observed signal is directly proportional to sample concentration, in contrast to the quadratic dependence from non-phase sensitive SHG, and that the real and imaginary parts of the 2nd order non-linear susceptibility can be determined independently. We show that the method is highly sensitive and can provide high quality excited state dynamics in short data acquisition times.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApPhL.106h1105Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApPhL.106h1105Z"><span id="translatedtitle">Resonant second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in a gallium nitride two-dimensional photonic crystal on silicon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zeng, Y.; Roland, I.; Checoury, X.; Han, Z.; El Kurdi, M.; Sauvage, S.; Gayral, B.; Brimont, C.; Guillet, T.; Mexis, M.; Semond, F.; Boucaud, P.</p> <p>2015-02-01</p> <p>We demonstrate second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in a gallium nitride photonic crystal cavity embedded in a two-dimensional free-standing photonic crystal platform on silicon. The photonic crystal nanocavity is optically pumped with a continuous-wave laser at telecom wavelengths in the transparency window of the nitride material. The <span class="hlt">harmonic</span> <span class="hlt">generation</span> is evidenced by the spectral range of the emitted signal, the quadratic power dependence vs. input power, and the spectral dependence of second <span class="hlt">harmonic</span> signal. The <span class="hlt">harmonic</span> emission pattern is correlated to the <span class="hlt">harmonic</span> polarization <span class="hlt">generated</span> by the second-order nonlinear susceptibilities χzxx (2 ), χzyy (2 ) and the electric fields of the fundamental cavity mode.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19838261','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19838261"><span id="translatedtitle">Radially polarized annular beam <span class="hlt">generated</span> through a second-<span class="hlt">harmonic-generation</span> process.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sato, Shunichi; Kozawa, Yuichi</p> <p>2009-10-15</p> <p>A radially polarized beam with an annular intensity pattern was <span class="hlt">generated</span> through a second-<span class="hlt">harmonic-generation</span> process by focusing an azimuthally polarized Ti:sapphire pulsed laser beam to a c-cut beta-barium borate (BBO) crystal. The annular intensity pattern of the second-<span class="hlt">harmonic</span> wave had a nearly sixfold symmetry as a result of the nonlinear susceptibility tensor of the BBO crystal. The width of the annulus was as narrow as less than 1/40th of its radius.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24238804','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24238804"><span id="translatedtitle">A study of <span class="hlt">acoustic</span> source <span class="hlt">generation</span> mechanism of Magnetoacoustic Tomography.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Shigang; Zhang, Shunqi; Ma, Ren; Yin, Tao; Liu, Zhipeng</p> <p>2014-01-01</p> <p>Magnetoacoustic Tomography (MAT) is a non-invasive imaging modality for electrical conductivity with good contrast and high spatial resolution. We have analyzed the <span class="hlt">acoustic</span> source <span class="hlt">generation</span> mechanism of MAT and presented its physical model, including the simulations and experiments in this paper. In MAT, <span class="hlt">acoustic</span> sources are <span class="hlt">generated</span> in a conductive object placed in a static magnetic field. Pulsed current is injected into the object and produces a Lorentz force due to the static magnetic filed. <span class="hlt">Acoustic</span> vibration was excited by the Lorentz force, and hence, ultrasound waves propagate in all directions and are collected with transducers placed around the object. The conductivity image can then be reconstructed with <span class="hlt">acoustic</span> waves using some reconstruction algorithms. Because the <span class="hlt">acoustic</span> source <span class="hlt">generation</span> mechanism of MAT is the key problem of forward and inverse problems, we analyzed the physical process of <span class="hlt">acoustic</span> source <span class="hlt">generation</span> and presented the <span class="hlt">acoustic</span> dipole source model according to the Lorentz force imposed on the object. In addition, computer simulations and experiments were also conducted. The results of simulations applying an <span class="hlt">acoustic</span> dipole source model are consistent with experimental results. This study has cardinal significance for the accurate algorithm of MAT and provides a methodology and reference for <span class="hlt">acoustic</span> source problems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AnPhy.372..182R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AnPhy.372..182R"><span id="translatedtitle"><span class="hlt">Acoustic</span> manipulation of active spherical carriers: <span class="hlt">Generation</span> of negative radiation force</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rajabi, Majid; Mojahed, Alireza</p> <p>2016-09-01</p> <p>This paper examines theoretically a novel mechanism of <span class="hlt">generating</span> negative (pulling) radiation force for <span class="hlt">acoustic</span> manipulation of spherical carriers equipped with piezoelectric actuators in its inner surface. In this mechanism, the spherical particle is handled by common plane progressive monochromatic <span class="hlt">acoustic</span> waves instead of zero-/higher- order Bessel beams or standing waves field. The handling strategy is based on applying a spatially uniform <span class="hlt">harmonic</span> electrical voltage at the piezoelectric actuator with the same frequency of handling <span class="hlt">acoustic</span> waves, in order to change the radiation force effect from repulsive (away from source) to attractive (toward source). This study may be considered as a start point for development of contact-free precise handling and entrapment technology of active carriers which are essential in many engineering and medicine applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19021326','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19021326"><span id="translatedtitle">Intermyofilament dynamics of myocytes revealed by second <span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Prent, Nicole; Green, Chantal; Greenhalgh, Catherine; Cisek, Richard; Major, Arkady; Stewart, Bryan; Barzda, Virginijus</p> <p>2008-01-01</p> <p>Drosophila melanogaster larva myocytes are imaged with second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) microscopy undergoing forced stretching and rhythmic contractions to determine the nature of the SHG signal. During stretching, double peaked SHG profiles of the anisotropic (A-) bands evolve into single peaks with a higher SHG intensity. The dip in the intensity profile at the center of the A-band is attributed to destructive interference from out-of-phase second <span class="hlt">harmonic</span> radiating myosin molecules that, in the central region of myofilaments, are arranged antiparallel. An intensity increase at the center of the A-band appears during forced stretching due to a small, less than 100 nm, intermyofilament separation of the antiparallel myosin molecules leading to constructive interference of the SHG radiation. In addition, the same phenomenon occurs during periodic contractions of the myocyte, where an SHG intensity increase with the lengthening of sarcomeres is observed. The SHG intensity dependence on sarcomere length can be used for imaging myocyte contractions with low resolution microscopy, and can be applied for the development of diagnostic tools where monitoring of muscle contraction dynamics is required.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990PhRvB..41.6913L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990PhRvB..41.6913L"><span id="translatedtitle">Symmetry superposition studied by surface second-<span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lüpke, G.; Marowsky, G.; Steinhoff, R.; Friedrich, A.; Pettinger, B.; Kolb, D. M.</p> <p>1990-04-01</p> <p>The components of a third-rank χ(2) tensor have been split into contributions due to 1-fold, 2-fold, 3-fold, and ∞-fold or isotropic rotation axes for a surface of Cs symmetry. Theoretical analysis of the rotation patterns obtained by the surface second-<span class="hlt">harmonic</span> (SH) <span class="hlt">generation</span> indicates that a complete symmetry analysis cannot be performed without knowledge of the relevant distribution functions. Rotation axes of lower symmetry create via ``overtones'' or ``<span class="hlt">harmonics</span>'' contributions apparent in the analysis of the rotation axes of higher symmetry. An experimental example is the observation of structural changes of Au(111) surfaces in an aqueous electrolytic environment. Potential-dependent buildup and removal of a Au(111)-(1×23) surface could be monitored in situ and in real time. Symmetry analysis of the SH rotation patterns reveals both contributions due to a 3-fold axis due to the regular (1×1) structure and simultaneously a 1-fold and a 2-fold axis due to the (1×23) reconstruction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012APS..MART29002S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012APS..MART29002S"><span id="translatedtitle"><span class="hlt">Harmonic</span> <span class="hlt">Generation</span> in InAs Nanowire Double Quantum Dots</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schroer, M. D.; Jung, M.; Petersson, K. D.; Petta, J. R.</p> <p>2012-02-01</p> <p>InAs nanowires provide a useful platform for investigating the physics of confined electrons subjected to strong spin-orbit coupling. Using tunable, bottom-gated double quantum dots, we demonstrate electrical driving of single spin resonance.ootnotetextS. Nadj-Perge et al., Nature 468, 1084 (2010)^,ootnotetextM.D. Schroer et al., Phys. Rev. Lett. 107, 176811 (2011) We observe a standard spin response when the applied microwave frequency equals the Larmour frequency f0. However, we also observe an anomalous signal at frequencies fn= f0/ n for integer n up to n ˜5. This is equivalent to <span class="hlt">generation</span> of <span class="hlt">harmonics</span> of the spin resonance field. While a f0/2 signal has observed,ootnotetextE.A. Laird et al., Phys. Rev. Lett. 99, 246601 (2007) we believe this is the first observation of higher <span class="hlt">harmonics</span> in spin resonance. Possible mechanisms will be discussed.ootnotetextE.I. Rashba, arXiv:1110.6569 (2011) Acknowledgements: Research supported by the Sloan and Packard Foundations, the NSF, and Army Research Office.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25122370','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25122370"><span id="translatedtitle">Cyclones and attractive streaming <span class="hlt">generated</span> by <span class="hlt">acoustical</span> vortices.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Riaud, Antoine; Baudoin, Michael; Thomas, Jean-Louis; Bou Matar, Olivier</p> <p>2014-07-01</p> <p><span class="hlt">Acoustical</span> and optical vortices have attracted great interest due to their ability to capture and manipulate particles with the use of radiation pressure. Here we show that <span class="hlt">acoustical</span> vortices can also induce axial vortical flow reminiscent of cyclones, whose topology can be controlled by adjusting the properties of the <span class="hlt">acoustical</span> beam. In confined geometry, the phase singularity enables <span class="hlt">generating</span> "attractive streaming" with the flow directed toward the transducer. This opens perspectives for contactless vortical flow control.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21277007','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21277007"><span id="translatedtitle">Resonant second <span class="hlt">harmonic</span> <span class="hlt">generation</span> of a Gaussian electromagnetic beam in a collisional magnetoplasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kaur, Sukhdeep; Sharma, A. K.; Salih, Hyder A.</p> <p>2009-04-15</p> <p>Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> of a right circularly polarized Gaussian electromagnetic beam in a magnetized plasma is investigated. The beam causes Ohmic heating of electrons and subsequent redistribution of the plasma, leading to self-defocusing. The radial density gradient, in conjunction with the oscillatory electron velocity, produces density oscillation at the wave frequency. The density oscillation beats with the oscillatory velocity to produce second <span class="hlt">harmonic</span> current density, giving rise to resonant second <span class="hlt">harmonic</span> radiation when the wave frequency is one-third of electron cyclotron frequency. The second <span class="hlt">harmonic</span> field has azimuthal dependence as exp(i{theta}). The self-defocusing causes a reduction in the efficiency of <span class="hlt">harmonic</span> <span class="hlt">generation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PMB....60.3441M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PMB....60.3441M"><span id="translatedtitle">Design factors of intravascular dual frequency transducers for super-<span class="hlt">harmonic</span> contrast imaging and <span class="hlt">acoustic</span> angiography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, Jianguo; Martin, K. Heath; Li, Yang; Dayton, Paul A.; Shung, K. Kirk; Zhou, Qifa; Jiang, Xiaoning</p> <p>2015-05-01</p> <p>Imaging of coronary vasa vasorum may lead to assessment of the vulnerable plaque development in diagnosis of atherosclerosis diseases. Dual frequency transducers capable of detection of microbubble super-<span class="hlt">harmonics</span> have shown promise as a new contrast-enhanced intravascular ultrasound (CE-IVUS) platform with the capability of vasa vasorum imaging. Contrast-to-tissue ratio (CTR) in CE-IVUS imaging can be closely associated with low frequency transmitter performance. In this paper, transducer designs encompassing different transducer layouts, transmitting frequencies, and transducer materials are compared for optimization of imaging performance. In the layout selection, the stacked configuration showed superior super-<span class="hlt">harmonic</span> imaging compared with the interleaved configuration. In the transmitter frequency selection, a decrease in frequency from 6.5 MHz to 5 MHz resulted in an increase of CTR from 15 dB to 22 dB when receiving frequency was kept constant at 30 MHz. In the material selection, the dual frequency transducer with the lead magnesium niobate-lead titanate (PMN-PT) 1-3 composite transmitter yielded higher axial resolution compared to single crystal transmitters (70 μm compared to 150 μm pulse length). These comparisons provide guidelines for the design of intravascular <span class="hlt">acoustic</span> angiography transducers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4427901','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4427901"><span id="translatedtitle">Design factors of intravascular dual frequency transducers for super-<span class="hlt">harmonic</span> contrast imaging and <span class="hlt">acoustic</span> angiography</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ma, Jianguo; Martin, K. Heath; Li, Yang; Dayton, Paul A.; Shung, K. Kirk; Zhou, Qifa; Jiang, Xiaoning</p> <p>2015-01-01</p> <p>Imaging of coronary vasa vasorum may lead to assessment of the vulnerable plaque development in diagnosis of atherosclerosis diseases. Dual frequency transducers capable of detection of microbubble super-<span class="hlt">harmonics</span> have shown promise as a new contrast-enhanced intravascular ultrasound (CE-IVUS) platform with the capability of vasa vasorum imaging. Contrast-to-tissue ratio (CTR) in CE-IVUS imaging can be closely associated with the low frequency transmitter performance. In this paper, transducer designs encompassing different transducer layouts, transmitting frequencies, and transducer materials are compared for optimization of imaging performance. In the layout selection, the stacked configuration showed superior super-<span class="hlt">harmonic</span> imaging compared with the interleaved configuration. In the transmitter frequency selection, a decrease in frequency from 6.5 MHz to 5 MHz resulted in an increase of CTR from 15 dB to 22 dB when receiving frequency was kept constant at 30 MHz. In the material selection, the dual frequency transducer with the lead magnesium niobate-lead titanate (PMN-PT) 1-3 composite transmitter yielded higher axial resolution compared to single crystal transmitters (70 μm compared to 150 μm pulse length). These comparisons provide guidelines for design of intravascular <span class="hlt">acoustic</span> angiography transducers. PMID:25856384</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25856384','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25856384"><span id="translatedtitle">Design factors of intravascular dual frequency transducers for super-<span class="hlt">harmonic</span> contrast imaging and <span class="hlt">acoustic</span> angiography.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ma, Jianguo; Martin, K Heath; Li, Yang; Dayton, Paul A; Shung, K Kirk; Zhou, Qifa; Jiang, Xiaoning</p> <p>2015-05-01</p> <p>Imaging of coronary vasa vasorum may lead to assessment of the vulnerable plaque development in diagnosis of atherosclerosis diseases. Dual frequency transducers capable of detection of microbubble super-<span class="hlt">harmonics</span> have shown promise as a new contrast-enhanced intravascular ultrasound (CE-IVUS) platform with the capability of vasa vasorum imaging. Contrast-to-tissue ratio (CTR) in CE-IVUS imaging can be closely associated with low frequency transmitter performance. In this paper, transducer designs encompassing different transducer layouts, transmitting frequencies, and transducer materials are compared for optimization of imaging performance. In the layout selection, the stacked configuration showed superior super-<span class="hlt">harmonic</span> imaging compared with the interleaved configuration. In the transmitter frequency selection, a decrease in frequency from 6.5 MHz to 5 MHz resulted in an increase of CTR from 15 dB to 22 dB when receiving frequency was kept constant at 30 MHz. In the material selection, the dual frequency transducer with the lead magnesium niobate-lead titanate (PMN-PT) 1-3 composite transmitter yielded higher axial resolution compared to single crystal transmitters (70 μm compared to 150 μm pulse length). These comparisons provide guidelines for the design of intravascular <span class="hlt">acoustic</span> angiography transducers. PMID:25856384</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/7009556','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/7009556"><span id="translatedtitle">Second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in zinc tris(thiourea) sulfate</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Marcy, H.O.; Warren, L.F. ); Webb, M.S.; Ebbers, C.A.; Velsko, S.P. ); Kennedy, G.C.; Catella, G.C. )</p> <p>1992-08-20</p> <p>The linear and second-order nonlinear optical properties of single-crystal zinc tris(thiourea) sulfate, or ZTS, are determined. The deduced nonlinear coefficients are {vert bar} {ital d}{sub 31} {vert bar}=0.31, {vert bar} {ital d}{sub 32} {vert bar}=0.35, and {vert bar} {ital d}{sub 33} {vert bar}=0.23 pm/V compared with a {vert bar} {ital d}{sub 14} {vert bar} value of 0.39 pm/V for potassium dihydrogen phosphate. Because it exhibits a low angular sensitivity ({delta}{Delta}{ital k}/{delta}{theta}), ZTS may prove useful for type-II second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> from 1.06 to 1.027 {mu}m. We present the phase-matching measurement data for ZTS and compare the calculated frequency conversion efficiency for ZTS with that of several other well-characterized materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015OptCo.353...35Z&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015OptCo.353...35Z&link_type=ABSTRACT"><span id="translatedtitle">High <span class="hlt">harmonic</span> <span class="hlt">generation</span> in the undulators for free electron lasers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhukovsky, K.</p> <p>2015-10-01</p> <p>We present the analysis of the undulator radiation (UR) with account for major sources of the spectral line broadening. For relativistic electrons we obtain the analytical expressions for the UR spectrum, the intensity and the emission line shape with account for the finite size of the beam, the emittance and the energy spread. Partial compensation of the divergency by properly imposed weak constant magnetic component is demonstrated in the analytical form. Considering the examples of radiation from single and double frequency undulators, we study high <span class="hlt">harmonic</span> <span class="hlt">generation</span> with account for all major sources of homogeneous and inhomogeneous broadening with account for the characteristics of the electrons beam. We apply our analysis to free electron laser (FEL) calculations and we compare the obtained results with the radiation of a FEL on the supposition of the ideal undulator.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JMOp...63...71S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JMOp...63...71S"><span id="translatedtitle">On probing conformation of microtubules by second-<span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sharoukhov, Denis; Lim, Hyungsik</p> <p>2016-01-01</p> <p>Microtubule (MT) is a component of cytoskeleton playing an important role in a variety of cellular processes. Altering the structure of MT is a crucial mechanism of modulating the function, but it is difficult to measure the in vivo conformation. We present here the use of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) for acquiring information about the architecture of MTs in living tissue. Axonal MTs were imaged by polarization-resolved SHG and anisotropy in the molecular structure was determined by means of the second-order tensor analysis. The feasibility of the second-order tensor analysis was tested for measuring the conformational changes induced by MT-stabilizing drug. It demonstrates that the new optical contrast may be useful for investigating the dynamics of MT cytoskeleton in vivo.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1305140','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1305140"><span id="translatedtitle">Interpreting Second-<span class="hlt">Harmonic</span> <span class="hlt">Generation</span> Images of Collagen I Fibrils</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Williams, Rebecca M.; Zipfel, Warren R.; Webb, Watt W.</p> <p>2005-01-01</p> <p>Fibrillar collagen, being highly noncentrosymmetric, possesses a tremendous nonlinear susceptibility. As a result, second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) microscopy of collagen produces extremely bright and robust signals, providing an invaluable tool for imaging tissue structure with submicron resolution. Here we discuss fundamental principles governing SHG phase matching with the tightly focusing optics used in microscopy. Their application to collagen imaging yields several biophysical features characteristic of native collagen structure: SHG radiates from the shell of a collagen fibril, rather than from its bulk. This SHG shell may correspond to the supporting element of the fibril. Physiologically relevant changes in solution ionic strength alter the ratio of forward-to-backward propagating SHG, implying a resulting change in the SHG shell thickness. Fibrillogenesis can be resolved in immature tissue by directly imaging backward-propagating SHG. Such findings are crucial to the design and development of forthcoming diagnostic and research tools. PMID:15533922</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013APS..MAR.U5012G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013APS..MAR.U5012G&link_type=ABSTRACT"><span id="translatedtitle">Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> in a Graphe Armchair Nanoribbon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gumbs, Godfrey; Abranyos, Yonatan</p> <p>2013-03-01</p> <p>The second order nonlinear optical susceptibility χ (2) for second <span class="hlt">harmonic</span> <span class="hlt">generation</span> is calculated for the 11H transition of a graded double quantum well (DQW) structure of undoped- GaAs / Alx Ga1 - x As . These results are compared with the single quantum well (QW). Our results show that the values of χ (2) have optimal magnitudes dependent on the width, depth and separation between the QWs in a DQW structure. When the electric field increases, the dipole moment increases due to the increasing separation between the electron and hole wave functions. On the other hand, the oscillator strength of the 11H transition is reduced as a result of the decrease in the overlap of the electron and hole envelope functions. These two competing factors give rise to optimal conditions for the enhancement of the second order nonlinear susceptibility χ (2). It is demonstrated that χ (2) for the DQW structure is more enhanced than for the biased single QW.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1036887','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1036887"><span id="translatedtitle">High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> enhanced by XUV light</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Buth, Christian; Kohler, Markus C.; Ullrich, Joachim; Keitel, Christoph H.</p> <p>2012-03-19</p> <p>The combination of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) with resonant XUV excitation of a core electron into the transient valence vacancy that is created in the course of the HHG process is investigated theoretically. In this setup, the first electron performs a HHG three-step process, whereas the second electron Rabi flops between the core and the valence vacancy. The modified HHG spectrum due to recombination with the valence and the core is determined and analyzed for krypton on the 3d {yields} 4p resonance in the ion. We assume an 800 nm laser with an intensity of about 10{sup 14} Wcm{sup 2} and XUV radiation from the Free Electron Laser in Hamburg (FLASH) with an intensity in the range 10{sup 13}-10{sup 16} Wcm{sup 2}. Our prediction opens perspectives for nonlinear XUV physics, attosecond x rays, and HHG-based spectroscopy involving core orbitals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JCrGr.303..520P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JCrGr.303..520P"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> and crystal growth of new chalcone derivatives</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Patil, P. S.; Dharmaprakash, S. M.; Ramakrishna, K.; Fun, Hoong-Kun; Sai Santosh Kumar, R.; Narayana Rao, D.</p> <p>2007-05-01</p> <p>We report on the synthesis, crystal structure and optical characterization of chalcone derivatives developed for second-order nonlinear optics. The investigation of a series of five chalcone derivatives with the second <span class="hlt">harmonic</span> <span class="hlt">generation</span> powder test according to Kurtz and Perry revealed that these chalcones show efficient second-order nonlinear activity. Among them, high-quality single crystals of 3-Br-4'-methoxychalcone (3BMC) were grown by solvent evaporation solution growth technique. Grown crystals were characterized by X-ray powder diffraction (XRD), laser damage threshold, UV-vis-NIR and refractive index measurement studies. Infrared spectroscopy, thermogravimetric analysis and differential thermal analysis measurements were performed to study the molecular vibration and thermal behavior of 3BMC crystal. Thermal analysis does not show any structural phase transition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995SPIE.2532..340N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995SPIE.2532..340N"><span id="translatedtitle">Electromagnetic study of second <span class="hlt">harmonic</span> <span class="hlt">generation</span> by a corrugated waveguide</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Neviere, Michel; Popov, E.; Reinisch, Raymond</p> <p>1995-09-01</p> <p>When an incident plane wave with circular frequency (omega) falls on a grating coated by a layer of nonlinear material, it <span class="hlt">generates</span> a nonlinear polarization PNL(2(omega) ) which acts as a source term and produces a second <span class="hlt">harmonic</span> (SH) field called signal. The excitation of an electromagnetic resonance like surface plasmon or a guided wave increases the local field and thus the signal. The problem is to be able to compute and optimize the latter. We have developed a new theory which uses a coordinate transformation mapping the grating profile onto a plane. This simplifies the boundary conditions but complicates the propagation equation. Taking advantage of the psuedoperiodicity of the problem, the Fourier <span class="hlt">harmonics</span> of the field are solution of a set of first order differential equations with constant coefficients. The resolution of this system via eigenvalue and eigenvector technique avoid numerical instabilities and lead to accurate results which agree perfectly with those found via the Rayleigh method or by the Differential method, when they work. A phenomenological approach is then developed to explain the unusual shape of the resonance lines at 2(omega) , which is based on the poles and zeros of the scattering operator S at (omega) and 2(omega) . It is shown that S(2(omega) ) presents 3 complex poles with 3 associated complex zeros. Their knowledge, plus the nonlinear reflectivity of the plane device allows predicting all the possible shapes of the 2(omega) signal as a function of angle of incidence. The phenomenological study explains an experimental result, found a few years ago, that if 2(omega) lies inside the absorption band of the guiding material instead of the transparent region, the enhanced second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) is changed into a reduced one. It means that in the case phase matching can lead to a minimum instead of maximum. An algorithm is then proposed to maximize the signal intensity; with polyurethane as a guiding material a conversion</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15002240','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15002240"><span id="translatedtitle">Polarization-Modulated Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> Microscopy in Collagen</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Stoller, P C</p> <p>2002-09-30</p> <p>Collagen is a key structural protein in the body; several pathological conditions lead to changes in collagen. Among imaging modalities that can be used in vivo, second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) microscopy has a key advantage: it provides {approx}1 {micro}m resolution information about collagen structure as a function of depth. A new technique--polarization-modulated SHG--is presented: it permits simultaneous measurement of collagen orientation, of a lower bound on the magnitude of the second order nonlinear susceptibility tensor, and of the ratio of the two independent elements in this tensor. It is applied to characterizing SHG in collagen and to determining effects of biologically relevant changes in collagen structure. The magnitude of the second <span class="hlt">harmonic</span> signal in two dimensional images varies with position even in structurally homogeneous tissue; this phenomenon is due to interference between second <span class="hlt">harmonic</span> light <span class="hlt">generated</span> by neighboring fibrils, which are randomly oriented parallel or anti-parallel to each other. Studies in which focal spot size was varied indicated that regions where fibrils are co-oriented are less than {approx}1.5 {micro}m in diameter. A quartz reference was used to determine the spot size as well as a lower limit (d{sub xxx} > 0.3 pm/V) for the magnitude of the second order nonlinear susceptibility. The ratio of the two independent tensor elements ranged between d{sub XYY}/d{sub XXX} = 0.60 and 0.75. SHG magnitude alone was not useful for identifying structural anomalies in collagenous tissue. Instead, changes in the polarization dependence of SHG were used to analyze biologically relevant perturbations in collagen structure. Changes in polarization dependence were observed in dehydrated samples, but not in highly crosslinked samples, despite significant alterations in packing structure. Complete thermal denaturation and collagenase digestion produced samples with no detectable SHG signal. Collagen orientation was measured in thin</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010PhRvA..82f3806B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010PhRvA..82f3806B&link_type=ABSTRACT"><span id="translatedtitle">Optical Cherenkov radiation in ultrafast cascaded second-<span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bache, M.; Bang, O.; Zhou, B. B.; Moses, J.; Wise, F. W.</p> <p>2010-12-01</p> <p>We show through theory and numerics that when few-cycle femtosecond solitons are <span class="hlt">generated</span> through cascaded (phase-mismatched) second-<span class="hlt">harmonic</span> <span class="hlt">generation</span>, these broadband solitons can emit optical Cherenkov radiation in the form of linear dispersive waves located in the red part of the spectrum. The beating between the dispersive wave and the soliton <span class="hlt">generates</span> trailing temporal oscillations on the compressed soliton. Insertion of a simple short-wave pass filter after the crystal can restore a clean soliton. On the other hand, bandpass filtering around the dispersive wave peak results in near-transform-limited ultrashort mid-IR pulses with pulse durations much shorter than the input near-IR pulse. The Cherenkov radiation for the crystal considered (β-barium borate) is found for pump wavelengths in the range λ=0.95-1.45μm, and is located in the regime λ=1.5-3.5μm. For shorter pump wavelengths, the phase-matching point is located in the absorption region of the crystal, effectively absorbing the <span class="hlt">generated</span> dispersive wave. By calculating the phase-matching curves for typically used frequency conversion crystals, we point out that the mid-IR absorption in the crystal in many cases automatically will filter away the dispersive wave. Finally, an investigation of recent experimental results uncovers a four-wave-mixing phenomenon related to Cherenkov radiation that is an additional <span class="hlt">generation</span> mechanism of long-wavelength radiation that can occur during soliton compression. We discuss the conditions that lead to this alternative dynamics rather than <span class="hlt">generation</span> of Cherenkov radiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Nanot..27P5206M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Nanot..27P5206M"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> from an individual amorphous selenium nanosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, C. R.; Yan, J. H.; Wei, Y. M.; Yang, G. W.</p> <p>2016-10-01</p> <p>Among the numerous nonlinear optics effects, second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) is always a hotspot and it is extensively used for optical frequency conversion, biomedical imaging, etc. However, SHG is forbidden in a medium with inversion symmetry under the electric-dipole approximation. Here, we demonstrated SHG from a single amorphous selenium (a-Se) nanosphere under near-infrared femtosecond pulse excitation. It was found that SH spectra are tunable with the size of a-Se nanospheres and the SHG efficiency of a single a-Se sphere with a diameter over 300 nm is estimated at 10-8. We also established two physical mechanisms of SHG from the amorphous nanospheres. There is an electric-dipole contribution to the second-order nonlinearity in view of the inevitable structural discontinuity at the surface. The discontinuity of the normal component of the electric field strength leads to the quadrupole-type contributions arising from the large electric field gradient. The SHG process can be enhanced by resonance near the fundamental wavelength, giving rise to the detectable second <span class="hlt">harmonic</span> (SH) spectra of a single a-Se nanosphere (d > 300 nm) or two small a-Se nanospheres (d = 200 nm) aggregated into a dimer, while the single nanosphere with smaller size (d > 300 nm) is undetectable. As an essential trace element for animals, a-Se features unique biological compatibility and has specific properties of optical nonlinearity within the optical window in biological tissue. This discovery makes a-Se nanospheres promising both in nonlinear optics and biomedicine.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27632529','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27632529"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> from an individual amorphous selenium nanosphere.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ma, C R; Yan, J H; Wei, Y M; Yang, G W</p> <p>2016-10-21</p> <p>Among the numerous nonlinear optics effects, second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) is always a hotspot and it is extensively used for optical frequency conversion, biomedical imaging, etc. However, SHG is forbidden in a medium with inversion symmetry under the electric-dipole approximation. Here, we demonstrated SHG from a single amorphous selenium (a-Se) nanosphere under near-infrared femtosecond pulse excitation. It was found that SH spectra are tunable with the size of a-Se nanospheres and the SHG efficiency of a single a-Se sphere with a diameter over 300 nm is estimated at 10(-8). We also established two physical mechanisms of SHG from the amorphous nanospheres. There is an electric-dipole contribution to the second-order nonlinearity in view of the inevitable structural discontinuity at the surface. The discontinuity of the normal component of the electric field strength leads to the quadrupole-type contributions arising from the large electric field gradient. The SHG process can be enhanced by resonance near the fundamental wavelength, giving rise to the detectable second <span class="hlt">harmonic</span> (SH) spectra of a single a-Se nanosphere (d > 300 nm) or two small a-Se nanospheres (d = 200 nm) aggregated into a dimer, while the single nanosphere with smaller size (d > 300 nm) is undetectable. As an essential trace element for animals, a-Se features unique biological compatibility and has specific properties of optical nonlinearity within the optical window in biological tissue. This discovery makes a-Se nanospheres promising both in nonlinear optics and biomedicine. PMID:27632529</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27632529','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27632529"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> from an individual amorphous selenium nanosphere.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ma, C R; Yan, J H; Wei, Y M; Yang, G W</p> <p>2016-10-21</p> <p>Among the numerous nonlinear optics effects, second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) is always a hotspot and it is extensively used for optical frequency conversion, biomedical imaging, etc. However, SHG is forbidden in a medium with inversion symmetry under the electric-dipole approximation. Here, we demonstrated SHG from a single amorphous selenium (a-Se) nanosphere under near-infrared femtosecond pulse excitation. It was found that SH spectra are tunable with the size of a-Se nanospheres and the SHG efficiency of a single a-Se sphere with a diameter over 300 nm is estimated at 10(-8). We also established two physical mechanisms of SHG from the amorphous nanospheres. There is an electric-dipole contribution to the second-order nonlinearity in view of the inevitable structural discontinuity at the surface. The discontinuity of the normal component of the electric field strength leads to the quadrupole-type contributions arising from the large electric field gradient. The SHG process can be enhanced by resonance near the fundamental wavelength, giving rise to the detectable second <span class="hlt">harmonic</span> (SH) spectra of a single a-Se nanosphere (d > 300 nm) or two small a-Se nanospheres (d = 200 nm) aggregated into a dimer, while the single nanosphere with smaller size (d > 300 nm) is undetectable. As an essential trace element for animals, a-Se features unique biological compatibility and has specific properties of optical nonlinearity within the optical window in biological tissue. This discovery makes a-Se nanospheres promising both in nonlinear optics and biomedicine.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900018148','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900018148"><span id="translatedtitle">Interaction of <span class="hlt">acoustic</span> waves <span class="hlt">generated</span> by coupled plate</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cuschieri, J. M.</p> <p>1990-01-01</p> <p>When two substructures are coupled, the <span class="hlt">acoustic</span> field <span class="hlt">generated</span> by the motion of each of the substructures will interact with the motion of the other substructure. This would be the case of a structure enclosing an <span class="hlt">acoustic</span> cavity. A technique to model the interaction of the <span class="hlt">generated</span> sound fields from the two components of a coupled structure, and the influence of this interaction on the vibration of the structural components is presented. Using a mobility power flow approach, each element of the substructure is treated independently both when developing the structural response and when determining the <span class="hlt">acoustic</span> field <span class="hlt">generated</span> by this component. The presence of the other substructural components is introduced by assuming these components to be rigid baffles. The excitation of one of the substructures is assumed to be by an incident <span class="hlt">acoustic</span> wave which is dependent of the motion of the substructure. The sound field <span class="hlt">generated</span> by the motion of the substructure is included in the solution of the response.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22072548','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22072548"><span id="translatedtitle">Numerical studies of third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in laser filament in air perturbed by plasma spot</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Feng Liubin; Lu Xin; Liu Xiaolong; Li Yutong; Chen Liming; Ma Jinglong; Dong Quanli; Wang Weimin; Xi Tingting; Sheng Zhengming; Zhang Jie; He Duanwei</p> <p>2012-07-15</p> <p>Third-<span class="hlt">harmonic</span> emission from laser filament intercepted by plasma spot is studied by numerical simulations. Significant enhancement of the third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> is obtained due to the disturbance of the additional plasma. The contribution of the pure plasma effect and the possible plasma-enhanced third-order susceptibility on the third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> enhancement are compared. It is shown that the plasma induced cancellation of destructive interference [Y. Liu et al., Opt. Commun. 284, 4706 (2011)] of two-colored filament is the dominant mechanism of the enhancement of third-<span class="hlt">harmonic</span> <span class="hlt">generation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27137242','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27137242"><span id="translatedtitle">Avalanche of stimulated forward scattering in high <span class="hlt">harmonic</span> <span class="hlt">generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Serrat, Carles; Roca, David; Budesca, Josep M; Seres, Jozsef; Seres, Enikoe; Aurand, Bastian; Hoffmann, Andreas; Namba, Shinichi; Kuehl, Thomas; Spielmann, Christian</p> <p>2016-04-18</p> <p>Optical amplifiers in all ranges of the electromagnetic spectrum exhibit an essential characteristic, namely the input signal during the propagation in the amplifier medium is multiplied by the avalanche effect of the stimulated emission to produce exponential growth. We perform a theoretical study motivated and supported by experimental data on a He gas amplifier driven by intense 30-fs-long laser pulses and seeded with attosecond pulse trains <span class="hlt">generated</span> in a separated Ne gas jet. We demonstrate that the strong-field theory in the frame of high <span class="hlt">harmonic</span> <span class="hlt">generation</span> fully supports the appearance of the avalanche effect in the amplification of extreme ultraviolet attosecond pulse trains. We theoretically separate and identify different physical processes taking part in the interaction and we demonstrate that X-ray parametric amplification dominates over others. In particular, we identify strong-field mediated intrapulse X-ray parametric processes as decisive for amplification at the single-atom level. We confirm that the amplification takes place at photon energies where the amplifier is seeded and when the seed pulses are perfectly synchronized with the driving strong field in the amplifier. Furthermore, propagation effects, phase matching and seed synchronization can be exploited to tune the amplified spectral range within the seed bandwidth. PMID:27137242</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4440497','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4440497"><span id="translatedtitle">Third <span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy of a mouse retina</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lei, Tim C.; Domingue, Scott R.; Kahook, Malik Y.; Bartels, Randy A.; Ammar, David A.</p> <p>2015-01-01</p> <p>Purpose To demonstrate lipid-specific imaging of the retina through the use of third <span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG), a multiphoton microscopic technique in which tissue contrast is <span class="hlt">generated</span> from optical inhomogeneities. Methods A custom fiber laser and multiphoton microscope was constructed and optimized for simultaneous two-photon autofluorescence (TPAF) and THG retinal imaging. Imaging was performed using fixed-frozen sections of mouse eyes without the use of exogenous fluorescent dyes. In parallel experiments, a fluorescent nuclear stain was used to verify the location of the retinal cell nuclei. Results Simultaneous THG and TPAF images revealed all retinal layers with subcellular resolution. In BALB/c strains, the THG signal stems from the lipidic organelles of the cellular and nuclear membranes. In the C57BL/6 strain, the THG signal from the RPE cells originates from the pigmented granules. Conclusions THG microscopy can be used to image structures of the mouse retina using contrast inherent to the tissue and without the use of a fluorescent dye or exogenously expressed recombinant protein. PMID:25999681</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011NJPh...13d3022S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011NJPh...13d3022S"><span id="translatedtitle">High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> directly from a filament</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steingrube, D. S.; Schulz, E.; Binhammer, T.; Gaarde, M. B.; Couairon, A.; Morgner, U.; Kovačev, M.</p> <p>2011-04-01</p> <p>The synthesis of isolated attosecond pulses (IAPs) in the extreme ultraviolet (XUV) spectral region has opened up the shortest time scales for time-resolved studies. It relies on the <span class="hlt">generation</span> of high-order <span class="hlt">harmonics</span> (HHG) from high-power few-cycle infrared (IR) laser pulses. Here we explore experimentally a new and simple route to IAP <span class="hlt">generation</span> directly from 35 fs IR pulses that undergo filamentation in argon. Spectral broadening, self-shortening of the IR pulse and HHG are realized in a single stage, reducing the cost and experimental effort for easier spreading of attosecond sources. We observe continuous XUV spectra supporting IAPs, emerging directly from the filament via a truncating pinhole to vacuum. The extremely short absorption length of the XUV radiation makes it a highly local probe for studying the elusive filamentation dynamics and in particular provides an experimental diagnostic of short-lived spikes in laser intensity. The excellent agreement with numerical simulations suggests the formation of a single-cycle pulse in the filament.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013SPIE.8588E..1RT','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013SPIE.8588E..1RT"><span id="translatedtitle">Imaging leukocytes in vivo with third <span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tsai, Cheng-Kun; Chen, Chien-Kuo; Chen, Yu-Shing; Wu, Pei-Chun; Hsieh, Tsung-Yuan; Liu, Han-Wen; Yeh, Chiou-Yueh; Lin, Win-Li; Chia, Jean-San; Liu, Tzu-Ming</p> <p>2013-02-01</p> <p>Without a labeling, we demonstrated that lipid granules in leukocytes have distinctive third <span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) contrast. Excited by a 1230nm femtosecond laser, THG signals were <span class="hlt">generated</span> at a significantly higher level in neutrophils than other mononuclear cells, whereas signals in agranular lymphocytes were one order smaller. These characteristic THG features can also be observed in vivo to trace the newly recruited leukocytes following lipopolysaccharide (LPS) challenge. Furthermore, using video-rate THG microscopy, we also captured images of blood cells in human capillaries. Quite different from red-blood-cells, every now and then, round and granule rich blood cells with strong THG contrast appeared in circulation. The corresponding volume densities in blood, evaluated from their frequencies of appearance and the velocity of circulation, fall within the physiological range of human white blood cell counts. These results suggested that labeling-free THG imaging may provide timely tracing of leukocyte movement and hematology inspection without disturbing the normal cellular or physiological status.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21686011','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21686011"><span id="translatedtitle">Angularly separated <span class="hlt">harmonic</span> <span class="hlt">generation</span> from intense laser interaction with blazed diffraction gratings.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yeung, M; Zepf, M; Geissler, M; Dromey, B</p> <p>2011-06-15</p> <p>We made numerical simulations of the <span class="hlt">generation</span> of narrowband beams of extreme ultraviolet radiation from intense laser interaction with a blazed grating surface. Strong fifth <span class="hlt">harmonic</span> emission into its blazed diffraction order was observed as well as heavy suppression of the fundamental frequency with comparison to a typical <span class="hlt">harmonic</span> spectrum from a flat target. The results demonstrate a new highly efficient method of <span class="hlt">generating</span> near-monochromatic <span class="hlt">harmonics</span> from the fundamental with minimal effect on the pulse duration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OptSp.120..306G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OptSp.120..306G"><span id="translatedtitle">Application of organic compounds for high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> of ultrashort pulses</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ganeev, R. A.</p> <p>2016-02-01</p> <p>The studies of the high-order nonlinear optical properties of a few organic compounds (polyvinyl alcohol, polyethylene, sugar, coffee, and leaf) are reported. <span class="hlt">Harmonic</span> <span class="hlt">generation</span> in the laser-produced plasmas containing the molecules and large particles of above materials is demonstrated. These studies showed that the <span class="hlt">harmonic</span> distributions and <span class="hlt">harmonic</span> cutoffs from organic compound plasmas were similar to those from the graphite ablation. The characteristic feature of observed <span class="hlt">harmonic</span> spectra was the presence of bluesided lobes near the lower-order <span class="hlt">harmonics</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20974975','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20974975"><span id="translatedtitle"><span class="hlt">Generation</span> mechanism for electron <span class="hlt">acoustic</span> solitary waves</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kakad, A. P.; Singh, S. V.; Reddy, R. V.; Lakhina, G. S.; Tagare, S. G.; Verheest, F.</p> <p>2007-05-15</p> <p>Nonlinear electron <span class="hlt">acoustic</span> solitary waves (EASWs) are studied in a collisionless and unmagnetized plasma consisting of cold background electrons, cold beam electrons, and two different temperature ion species. Using pseudopotential analysis, the properties of arbitrary amplitude EASWs are investigated. The present model supports compressive as well as rarefactive electron <span class="hlt">acoustic</span> solitary structures. Furthermore, there is an interesting possibility of the coexistence of compressive and rarefactive solitary structures in a specific plasma parameter range. The application of our results in interpreting the salient features of the broadband electrostatic noise in the plasma sheet boundary layer is discussed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21316474','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21316474"><span id="translatedtitle">High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> from C{sub 60}-rich plasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ganeev, R. A.; Elouga Bom, L. B.; Ozaki, T.; Wong, M. C. H.; Brichta, J.-P.; Bhardwaj, V. R.; Redkin, P. V.</p> <p>2009-10-15</p> <p>We performed systematic investigation of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> from fullerene-rich laser-produced plasmas. We studied <span class="hlt">harmonic</span> <span class="hlt">generation</span> by varying several experimental parameters, such as the delay between the ablation and driving pulses, and divergence and polarization of the pump laser. Enhancement of <span class="hlt">harmonic</span> yield is observed near 20 eV, which is attributed to the influence of a broadband plasmon resonance of C{sub 60} on the nonlinear optical response of fullerene-rich plasma. This increase in the <span class="hlt">harmonic</span> intensity occurs despite the increased absorption by C{sub 60} at these wavelengths. Using simulations based on time-dependent density-functional theory, we confirm that this effect is due to the influence of collective excitations. We compare <span class="hlt">harmonic</span> <span class="hlt">generation</span> from fullerenes using lasers with 793 nm and 396 nm wavelengths, which show the influence of plasmon resonance on the conversion efficiency of high-order <span class="hlt">harmonics</span> for different laser wavelengths.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990OptCo..74..419M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990OptCo..74..419M"><span id="translatedtitle">Contribution of longitudinal electric field of a gaussian beam to second <span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mishra, S. R.; Rustagi, K. C.</p> <p>1990-01-01</p> <p>A laser beam with a nonuniform transverse intensity profile necessarily has a longitudinal component of the electric field. We show that a detectable second <span class="hlt">harmonic</span> can be <span class="hlt">generated</span> due to coupling of this longitudinal component with the transverse field of a gaussian beam in a configuration in which second <span class="hlt">harmonic</span> <span class="hlt">generation</span> is forbidden for plane wave interaction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6195','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6195"><span id="translatedtitle">Predicting bulk damage in NIF triple <span class="hlt">harmonic</span> <span class="hlt">generators</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>De Yoreo, J; Runkel, M; Williams, W</p> <p>1998-09-18</p> <p>Recently reported experiments have investigated the statistics of laser damage in KDP and KD*P. Automated damage tests have allowed cumulative failure and damage probability distributions to be constructed. Large area tests have investigated the feasibility of on-line laser conditioning and damage evolution for tripler <span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) crystals on the National Ignition Facility (NIF). These tests have shown that there is a nonzero probability of damage at NIF redline fluence (14.3 J/cm2, 351 nm, 3 ns) and that the damage pinpoint density evolves exponentially with fluence. In this paper, the results of these tests are used in conjunction with model spatial profiles of the NIP beam to predict the level of damage created in the THG crystal. A probabilistic calculation based on the overlap of the beam fluence and damage probabiity distribution shows that the overall damage probability is less than 3% for well-conditioned, high quality KDP/KD*P crystals of conventional or rapid growth. The number density of <span class="hlt">generated</span> pinpoints has been calculated by mapping the damage evolution curves onto the NlF model profile. This shows that the number of damage pinpoints <span class="hlt">generated</span> in high fluence portions of the NIF beam will be low for well-conditioned THG crystals. In contrast, unconditioned triplers of the same material will exhibit an increase in pinpoint density of greater than 20x. To test the validity of these calculations a 37 cm, conventionally grown KD*P tripler from the Beamlet laser was scatter mapped for bulk damage. The tripler had been exposed to NE-like fluences during its operational lifetime on Beamlet and exhibited very low levels of bulk pinpoint damage, essentially supporting the predictions based on tests and modeling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23927191','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23927191"><span id="translatedtitle">High-speed observation of bubble cloud <span class="hlt">generation</span> near a rigid wall by second-<span class="hlt">harmonic</span> superimposed ultrasound.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yoshizawa, Shin; Yasuda, Jun; Umemura, Shin-ichiro</p> <p>2013-08-01</p> <p>Cavitation bubbles are known to accelerate therapeutic effects of ultrasound. Although negative <span class="hlt">acoustic</span> pressure is the principle factor of cavitation, positive <span class="hlt">acoustic</span> pressure has a role for bubble cloud formation at a high intensity of focused ultrasound when cavitation bubbles provide pressure release surfaces converting the pressure from highly positive to negative. In this study, the second-<span class="hlt">harmonic</span> was superimposed onto the fundamental <span class="hlt">acoustic</span> pressure to emphasize either peak positive or negative pressure. The peak negative and positive pressure emphasized waves were focused on a surface of an aluminum block. Cavitation bubbles induced near the block were observed with a high-speed camera by backlight and the size of the cavitation <span class="hlt">generation</span> region was measured from the high-speed images. The negative pressure emphasized waves showed an advantage in cavitation inception over the positive pressure emphasized waves. In the sequence of the negative pressure emphasized waves immediately followed by the positive pressure emphasized waves, cavitation bubbles were <span class="hlt">generated</span> on the block by the former waves and the cavitation region were expanded toward the transducer in the latter waves with high reproducibility. The sequence demonstrated its potential usefulness in enhancing the effects of therapeutic ultrasound at a high <span class="hlt">acoustic</span> intensity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NaPho...9..743H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NaPho...9..743H"><span id="translatedtitle">Non-collinear <span class="hlt">generation</span> of angularly isolated circularly polarized high <span class="hlt">harmonics</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hickstein, Daniel D.; Dollar, Franklin J.; Grychtol, Patrik; Ellis, Jennifer L.; Knut, Ronny; Hernández-García, Carlos; Zusin, Dmitriy; Gentry, Christian; Shaw, Justin M.; Fan, Tingting; Dorney, Kevin M.; Becker, Andreas; Jaroń-Becker, Agnieszka; Kapteyn, Henry C.; Murnane, Margaret M.; Durfee, Charles G.</p> <p>2015-11-01</p> <p>We <span class="hlt">generate</span> angularly isolated beams of circularly polarized extreme ultraviolet light through the first implementation of non-collinear high <span class="hlt">harmonic</span> <span class="hlt">generation</span> with circularly polarized driving lasers. This non-collinear technique offers numerous advantages over previous methods, including the <span class="hlt">generation</span> of higher photon energies, the separation of the <span class="hlt">harmonics</span> from the pump beam, the production of both left and right circularly polarized <span class="hlt">harmonics</span> at the same wavelength and the capability of separating the <span class="hlt">harmonics</span> without using a spectrometer. To confirm the circular polarization of the beams and to demonstrate the practicality of this new light source, we measure the magnetic circular dichroism of a 20 nm iron film. Furthermore, we explain the mechanisms of non-collinear high <span class="hlt">harmonic</span> <span class="hlt">generation</span> using analytical descriptions in both the photon and wave models. Advanced numerical simulations indicate that this non-collinear mixing enables the <span class="hlt">generation</span> of isolated attosecond pulses with circular polarization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4078302','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4078302"><span id="translatedtitle">Extraordinary Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> in Tungsten Disulfide Monolayers</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Janisch, Corey; Wang, Yuanxi; Ma, Ding; Mehta, Nikhil; Elías, Ana Laura; Perea-López, Néstor; Terrones, Mauricio; Crespi, Vincent; Liu, Zhiwen</p> <p>2014-01-01</p> <p>We investigate Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> (SHG) in monolayer WS2 both deposited on a SiO2/Si substrate or suspended using transmission electron microscopy grids. We find unusually large second order nonlinear susceptibility, with an estimated value of deff ~ 4.5 nm/V nearly three orders of magnitude larger than other common nonlinear crystals. In order to quantitatively characterize the nonlinear susceptibility of two-dimensional (2D) materials, we have developed a formalism to model SHG based on the Green's function with a 2D nonlinear sheet source. In addition, polarized SHG is demonstrated as a useful method to probe the structural symmetry and crystal orientation of 2D materials. To understand the large second order nonlinear susceptibility of monolayer WS2, density functional theory based calculation is performed. Our analysis suggests the origin of the large nonlinear susceptibility in resonance enhancement and a large joint density of states, and yields an estimate of the nonlinear susceptibility value deff = 0.77 nm/V for monolayer WS2, which shows good order-of-magnitude agreement with the experimental result. PMID:24984953</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JBO....20i5013C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JBO....20i5013C"><span id="translatedtitle">Third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> susceptibility spectroscopy in free fatty acids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Yu-Cheng; Hsu, Hsun-Chia; Lee, Chien-Ming; Sun, Chi-Kuang</p> <p>2015-09-01</p> <p>Lipid-correlated disease such as atherosclerosis has been an important medical research topic for decades. Many new microscopic imaging techniques such as coherent anti-Stokes Raman scattering and third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) microscopy were verified to have the capability to target lipids in vivo. In the case of THG microscopy, biological cell membranes and lipid bodies in cells and tissues have been shown as good sources of contrast with a laser excitation wavelength around 1200 nm. We report the THG excitation spectroscopy study of two pure free fatty acids including oleic acid and linoleic acid from 1090 to 1330 nm. Different pure fatty acids presented slightly-different THG χ(3) spectra. The measured peak values of THG third-order susceptibility χ(3) in both fatty acids were surprisingly found not to match completely with the resonant absorption wavelengths around 1190 to 1210 nm, suggesting possible wavelengths selection for enhanced THG imaging of lipids while avoiding laser light absorption. Along with the recent advancement in THG imaging, this new window between 1240 to 1290 nm may offer tremendous new opportunities for sensitive label-free lipid imaging in biological tissues.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006SPIE.6089..283M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006SPIE.6089..283M"><span id="translatedtitle">Imaging articular cartilage using second <span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mansfield, Jessica C.; Winlove, C. Peter; Knapp, Karen; Matcher, Stephen J.</p> <p>2006-02-01</p> <p>Sub cellular resolution images of equine articular cartilage have been obtained using both second <span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy (SHGM) and two-photon fluorescence microscopy (TPFM). The SHGM images clearly map the distribution of the collagen II fibers within the extracellular matrix while the TPFM images show the distribution of endogenous two-photon fluorophores in both the cells and the extracellular matrix, highlighting especially the pericellular matrix and bright 2-3μm diameter features within the cells. To investigate the source of TPF in the extracellular matrix experiments have been carried out to see if it may originate from the proteoglycans. Pure solutions of the following proteoglycans hyaluronan, chondroitin sulfate and aggrecan have been imaged, only the aggrecan produced any TPF and here the intensity was not great enough to account for the TPF in the extracellular matrix. Also cartilage samples were subjected to a process to remove proteoglycans and cellular components. After this process the TPF from the samples had decreased by a factor of two, with respect to the SHG intensity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4420541','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4420541"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> from the ‘centrosymmetric’ crystals</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Nalla, Venkatram; Medishetty, Raghavender; Wang, Yue; Bai, Zhaozhi; Sun, Handong; Wei, Ji.; Vittal, Jagadese J.</p> <p>2015-01-01</p> <p>Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) is a well known non-linear optical phenomena which can be observed only in non-centrosymmetric crystals due to non-zero hyperpolarizability. In the current work we observed SHG from a Zn(II) complex which was originally thought to have crystallized in the centrosymmetric space group C2/c. This has been attributed to the unequal antiparallel packing of the metal complexes in the non-symmetric space group Cc or residual non-centrosymmetry in C2/c giving rise to polarizability leading to strong SHG. The enhancement of SHG by UV light has been attributed to the increase in non-centrosymmetry and hence polarity of packing due to strain induced in the crystals. The SHG signals measured from these crystals were as large as potassium dihydrogen phosphate crystals, KH2PO4 (KDP), and showed temperature dependence. The highest SHG efficiency was observed at 50 K. The SHG phenomenon was observed at broad wavelengths ranging from visible to below-red in these crystals. PMID:25995840</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SPIE.9230E..1JL','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SPIE.9230E..1JL"><span id="translatedtitle">Research of second <span class="hlt">harmonic</span> <span class="hlt">generation</span> images based on texture analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Yao; Li, Yan; Gong, Haiming; Zhu, Xiaoqin; Huang, Zufang; Chen, Guannan</p> <p>2014-09-01</p> <p>Texture analysis plays a crucial role in identifying objects or regions of interest in an image. It has been applied to a variety of medical image processing, ranging from the detection of disease and the segmentation of specific anatomical structures, to differentiation between healthy and pathological tissues. Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) microscopy as a potential noninvasive tool for imaging biological tissues has been widely used in medicine, with reduced phototoxicity and photobleaching. In this paper, we clarified the principles of texture analysis including statistical, transform, structural and model-based methods and gave examples of its applications, reviewing studies of the technique. Moreover, we tried to apply texture analysis to the SHG images for the differentiation of human skin scar tissues. Texture analysis method based on local binary pattern (LBP) and wavelet transform was used to extract texture features of SHG images from collagen in normal and abnormal scars, and then the scar SHG images were classified into normal or abnormal ones. Compared with other texture analysis methods with respect to the receiver operating characteristic analysis, LBP combined with wavelet transform was demonstrated to achieve higher accuracy. It can provide a new way for clinical diagnosis of scar types. At last, future development of texture analysis in SHG images were discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27416357','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27416357"><span id="translatedtitle">Titanosilicates with Strong Phase-Matched Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> Responses.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chao, Tzu-Ling; Chang, Wen-Jung; Wen, Shu-Han; Lin, Yu-Qing; Chang, Bor-Chen; Lii, Kwang-Hwa</p> <p>2016-07-27</p> <p>The search for new and efficient nonlinear optical (NLO) materials has been an active research because of their technological importance in laser applications. Although a large number of frequency-doubling oxides, phosphates, borates, and fluoride-containing borates were found, no transition-metal silicate with useful NLO properties has been reported. We have now synthesized and grown crystals of two new titanosilicates, Li2K4[(TiO)Si4O12] and Li2Rb4[(TiO)Si4O12], by using a flux and supercritical hydrothermal method. Their unique 3D framework structures contain highly compressed TiO5 square pyramids which are arranged one over the other to form infinite ···Ti-O···Ti-O straight chains with alternating short and long Ti-O distances. These two materials meet the requirements for efficient second <span class="hlt">harmonic</span> <span class="hlt">generation</span> including lack of center of inversion symmetry, large susceptibility, phase matching, transmitting at wavelengths of interest, resistant to laser damage, and thermally stable. These attributes make them very attractive for frequency-doubling materials. PMID:27416357</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013SPIE.8915E..13T&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013SPIE.8915E..13T&link_type=ABSTRACT"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> of chiral-modified silver nanoparticles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tao, Yue; Aldea-Nunzi, Gabriela; Rao Bobbara, Sanyasi; Nunzi, Jean-Michel</p> <p>2013-10-01</p> <p>Various approaches for the optical detection of chiral compounds have been developed due to their natural optical activity. Since the advantages of second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) on noble-metal nanoparticles (NPs) have been observed, it would be interesting to study the nonlinear phenomena from chiral compounds attached Ag NPs. In the present work, we fabricated chiral-modified Ag NPs based on the self-assembly process of cysteine and Ag, and carried out the investigation on SHG on modified and unmodified Ag NPs. For modified Ag NPs, either L-Cysteine (L-C) or D-Cysteine (D-C), as a pair of enantiomers, was applied on top of the Ag NPs. The resulting chiral-modified monolayers of L-C/Ag NPs and D-C/Ag NPs exhibit a reversed optical rotation difference (ORD) at linearly +/-45° polarization of SH, where no such difference exists for Ag NPs alone. SHG efficiently probes and discriminates L-C from D-C monolayers on the modified Ag NPs, which constitutes a simple and sensitive optical diagnostic of chiral molecules.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6779249','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6779249"><span id="translatedtitle">Studies of surfaces using optical second-<span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tom, H.W.K.</p> <p>1984-04-01</p> <p>The experiments reported in this thesis demonstrate the use of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) and sum-frequency <span class="hlt">generation</span> (SFG) in reflection from surfaces to study various surface properties. The experiments firmly establish SHG as a viable new surface probe that complements existing surface probes in ultrahigh vacuum environments and is in many ways unique for studying interfaces between dense media. Surface structural symmetry can be revealed through the anisotropy in the SH signal from the surface as the sample is rotated about its normal. The form of this anisotropy is derived in theory and verified with an experiment on the Si(100) and (111) surfaces. The SHG and SFG signals from molecules adsorbed on noninteracting substrates have a direct relationship to the number, average orientation, and spectroscopic properties of the molecules. The SH intensity was used to measure the isotherm for adsorption of p-nitrobenzoic acid from ethanolic solution to fused silica. Experiments performed on a strongly-interacting well-characterized Rh(111) surface in ultrahigh vacuum establish the sensitivity of the SH probe in corroboration with other surface probes. For the first time, the SH coverage-dependence was fit by theory in a quantitative way for the case of O-atom adsorption. The sensitivity of SH to adsorption at different sites was established for CO on top- and bridge-sites. SHG was shown to be surface specific in that the SHG from alkali metal surfaces originates from the first two monolayers. SH sensitivity to the adsorption of catalytically-important hydrocarbons and to chemical processes such as benzene dehydrogenation was also demonstrated. 122 references, 27 figures, 2 tables.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IJT....36.2285M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IJT....36.2285M"><span id="translatedtitle"><span class="hlt">Acoustic</span> Aspects of Photoacoustic Signal <span class="hlt">Generation</span> and Detection in Gases</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miklós, A.</p> <p>2015-09-01</p> <p>In this paper photoacoustic signal <span class="hlt">generation</span> and detection in gases is investigated and discussed from the standpoint of <span class="hlt">acoustics</span>. Four topics are considered: the effect of the absorption-desorption process of modulated and pulsed light on the heat power density released in the gas; the <span class="hlt">generation</span> of the primary sound by the released heat in an unbounded medium; the excitation of an <span class="hlt">acoustic</span> resonator by the primary sound; and finally, the <span class="hlt">generation</span> of the measurable PA signal by a microphone. When light is absorbed by a molecule and the excess energy is relaxed by collisions with the surrounding molecules, the average kinetic energy, thus also the temperature of an ensemble of molecules (called "particle" in <span class="hlt">acoustics</span>) will increase. In other words heat energy is added to the energy of the particle. The rate of the energy transfer is characterized by the heat power density. A simple two-level model of absorption-desorption is applied for describing the heat power <span class="hlt">generation</span> process for modulated and pulsed illumination. Sound <span class="hlt">generation</span> by a laser beam in an unbounded medium is discussed by means of the Green's function technique. It is shown that the duration of the <span class="hlt">generated</span> sound pulse depends mostly on beam geometry. A photoacoustic signal is mostly detected in a photoacoustic cell composed of <span class="hlt">acoustic</span> resonators, buffers, filters, etc. It is not easy to interpret the measured PA signal in such a complicated <span class="hlt">acoustic</span> system. The <span class="hlt">acoustic</span> response of a PA detector to different kinds of excitations (modulated cw, pulsed, periodic pulse train) is discussed. It is shown that <span class="hlt">acoustic</span> resonators respond very differently to modulated cw excitation and to excitation by a pulse train. The microphone for detecting the PA signal is also a part of the <span class="hlt">acoustic</span> system; its properties have to be taken into account by the design of a PA detector. The moving membrane of the microphone absorbs <span class="hlt">acoustic</span> energy; thus, it may influence the resonance frequency and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012PhRvB..86h5422G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012PhRvB..86h5422G&link_type=ABSTRACT"><span id="translatedtitle">Nonlinearly coupled localized plasmon resonances: Resonant second-<span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ginzburg, Pavel; Krasavin, Alexey; Sonnefraud, Yannick; Murphy, Antony; Pollard, Robert J.; Maier, Stefan A.; Zayats, Anatoly V.</p> <p>2012-08-01</p> <p>The efficient resonant nonlinear coupling between localized surface plasmon modes is demonstrated in a simple and intuitive way using boundary integral formulation and utilizing second-order optical nonlinearity. The nonlinearity is derived from the hydrodynamic description of electron plasma and originates from the presence of material interfaces in the case of small metal particles. The coupling between fundamental and second-<span class="hlt">harmonic</span> modes is shown to be symmetry selective and proportional to the spatial overlap between polarization dipole density of the second-<span class="hlt">harmonic</span> mode and the square of the polarization charge density of the fundamental mode. Particles with high geometrical symmetry will convert a far-field illumination into dark nonradiating second-<span class="hlt">harmonic</span> modes, such as quadrupoles. Effective second-<span class="hlt">harmonic</span> susceptibilities are proportional to the surface-to-volume ratio of a particle, emphasizing the nanoscale enhancement of the effect.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22410454','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22410454"><span id="translatedtitle">Efficient second- and third-<span class="hlt">harmonic</span> radiation <span class="hlt">generation</span> from relativistic laser-plasma interactions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Singh, Mamta; Gupta, D. N.; Suk, H.</p> <p>2015-06-15</p> <p>We propose an idea to enhance the efficiency of second- and third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> by considering the amplitude-modulation of the fundamental laser pulse. A short-pulse laser of finite spot size is modeled as amplitude modulated in time. Amplitude-modulation of fundamental laser contributes in quiver velocity of the plasma electrons and produces the strong plasma-density perturbations, thereby increase in current density at second- and third-<span class="hlt">harmonic</span> frequency. In a result, the conversion efficiency of <span class="hlt">harmonic</span> <span class="hlt">generation</span> increases significantly. Power conversion efficiency of <span class="hlt">harmonic</span> <span class="hlt">generation</span> process is the increasing function of the amplitude-modulation parameter of the fundamental laser beam. <span class="hlt">Harmonic</span> power <span class="hlt">generated</span> by an amplitude modulated laser is many folds higher than the power obtained in an ordinary case.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27661915','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27661915"><span id="translatedtitle">All-fiber fourth and fifth <span class="hlt">harmonic</span> <span class="hlt">generation</span> from a single source.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Khudus, Muhammad I M Abdul; Lee, Timothy; De Lucia, Francesco; Corbari, Costantino; Sazio, Pier; Horak, Peter; Brambilla, Gilberto</p> <p>2016-09-19</p> <p>All-fiber fourth and fifth <span class="hlt">harmonic</span> <span class="hlt">generation</span> from a single source is demonstrated experimentally and analyzed theoretically. Light from a fully fiberized high power master oscillator power amplifier is launched into a periodically poled silica fiber <span class="hlt">generating</span> the second <span class="hlt">harmonic</span>. The output is then sent through two optical microfibers that <span class="hlt">generate</span> the third and fourth <span class="hlt">harmonic</span>, respectively, via four wave mixing (FWM). For a large range of pump wavelengths in the silica optical transmission window, phase matched FWM can be achieved in the microfibers at two different diameters with relatively wide fabrication tolerances of up to +/-5 nm. Our simulations indicate that by optimizing the second <span class="hlt">harmonic</span> <span class="hlt">generation</span> efficiency and the diameters and lengths of the two microfibers, conversion efficiencies to the fourth <span class="hlt">harmonic</span> in excess of 25% are theoretically achievable. PMID:27661915</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22093552','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22093552"><span id="translatedtitle">Tracing the structure of asymmetric molecules from high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chen Yanjun; Zhang, Bing</p> <p>2011-11-15</p> <p>We investigate high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) from asymmetric molecules exposed to intense laser fields. We show that the emissions of odd and even <span class="hlt">harmonics</span> depend differently on the orientation angle, the internuclear distance, as well as the effective charge. This difference mainly comes from different roles of intramolecular interference in the HHG of odd and even <span class="hlt">harmonics</span>. These roles map the structure of the asymmetric molecule to the odd vs even HHG spectra.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23145619','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23145619"><span id="translatedtitle">Improved perception of speech in noise and Mandarin tones with <span class="hlt">acoustic</span> simulations of <span class="hlt">harmonic</span> coding for cochlear implants.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Xing; Nie, Kaibao; Imennov, Nikita S; Won, Jong Ho; Drennan, Ward R; Rubinstein, Jay T; Atlas, Les E</p> <p>2012-11-01</p> <p><span class="hlt">Harmonic</span> and temporal fine structure (TFS) information are important cues for speech perception in noise and music perception. However, due to the inherently coarse spectral and temporal resolution in electric hearing, the question of how to deliver <span class="hlt">harmonic</span> and TFS information to cochlear implant (CI) users remains unresolved. A <span class="hlt">harmonic</span>-single-sideband-encoder [(HSSE); Nie et al. (2008). Proceedings of IEEE International Conference on <span class="hlt">Acoustics</span>, Speech, and Signal Processing; Lie et al., (2010). Proceedings of IEEE International Conference on <span class="hlt">Acoustics</span>, Speech, and Signal Processing] strategy has been proposed that explicitly tracks the <span class="hlt">harmonics</span> in speech and transforms them into modulators conveying both amplitude modulation and fundamental frequency information. For unvoiced speech, HSSE transforms the TFS into a slowly varying yet still noise-like signal. To investigate its potential, four- and eight-channel vocoder simulations of HSSE and the continuous-interleaved-sampling (CIS) strategy were implemented, respectively. Using these vocoders, five normal-hearing subjects' speech recognition performance was evaluated under different masking conditions; another five normal-hearing subjects' Mandarin tone identification performance was also evaluated. Additionally, the neural discharge patterns evoked by HSSE- and CIS-encoded Mandarin tone stimuli were simulated using an auditory nerve model. All subjects scored significantly higher with HSSE than with CIS vocoders. The modeling analysis demonstrated that HSSE can convey temporal pitch cues better than CIS. Overall, the results suggest that HSSE is a promising strategy to enhance speech perception with CIs. PMID:23145619</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT.......264P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT.......264P"><span id="translatedtitle">Characterization of muscle contraction with second <span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prent, Nicole</p> <p></p> <p>Muscle cells have the ability to change length and <span class="hlt">generate</span> force due to orchestrated action of myosin nanomotors that cause sliding of actin filaments along myosin filaments in the sarcomeres, the fundamental contractile units, of myocytes. The correlated action of hundreds of sarcomeres is needed to produce the myocyte contractions. This study probes the molecular structure of the myofilaments and investigates the movement correlations between sarcomeres during contraction. In this study, second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) microscopy is employed for imaging striated myocytes. Myosin filaments in striated myocytes inherently have a nonzero second-order susceptibility, [special characters omitted] and therefore <span class="hlt">generate</span> efficient SHG. Employing polarization-in polarization-out (PIPO) SHG microscopy allows for the accurate determination of the characteristic ratio, [special characters omitted] in birefringent myocytes, which describes the structure of the myosin filament. Analysis shows that the b value at the centre of the myosin filament, where the nonlinear dipoles are better aligned, is slightly lower than the value at the edges of the filament, where there is more disorder in orientation of the nonlinear dipoles from the myosin heads. Forced stretching of myocytes resulted in an SHG intensity increase with the elongation of the sarcomere. SHG microscopy captured individual sarcomeres during contraction, allowing for the measurement of sarcomere length (SL) and SHG intensity (SI) fluctuations. The fluctuations also revealed higher SHG intensity in elongated sarcomeres. The sarcomere synchronization model (SSM) for contracting and quiescent myocytes was developed, and experimentally verified for three cases (isolated cardiomyocyte, embryonic chicken cardiomyocyte, and larva myocyte). During contraction, the action of SLs and SIs between neighbouring sarcomeres partially correlated, whereas in quiescent myocytes the SLs show an anti-correlation and the SIs have no</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10120741','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10120741"><span id="translatedtitle">Studies of interfaces and vapors with Optical Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mullin, C. S.</p> <p>1993-12-01</p> <p>Optical Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> (SHG) has been applied to the study of soap-like molecules adsorbed to the water-air interface. By calibrating the signal from a soluble monolayer with that of an insoluble homolog, absolute measurements of the surface density could be obtained and related to the bulk concentration and surface tension. We could then demonstrate that the soluble surfactant forms a single monolayer at the interface. Furthermore, it deviates significantly from the ideal case in that its activity coefficients are far from 1, yet those coefficients remain constant over a broad range of surface pressures. We present evidence of a first-order phase transition taking place during the adsorption of this soluble monolayer. We consider the effects of the non-ideal behavior and the phase transition on the microscopic model of adsorption, and formulate an alternative to the Langmuir picture of adsorption which is just as simple, yet it can more easily allow for non-ideal behavior. The second half of this thesis considers the problem of SHG in bulk metal vapors. The symmetry of the vapor forbids SHG, yet it has been observed. We consider several models whereby the symmetry of the vapor is broken by the presence of the laser and compare their predictions to new observations we have made using a few-picosecond laser pulse. The two-lobed output beam profile shows that it is the vapor-plus-beam combination whose symmetry is important. The dependence on vapor pressure demonstrates the coherent nature of the radiation, while the dependence on buffer gas pressure hints at a change of the symmetry in time. The time-dependence is measured directly with a preliminary pump-probe measurement. The magnitude and intensity dependence of the signal are also measured. All but one of the models are eliminated by this comparison.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005SPIE.5700..205M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005SPIE.5700..205M"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> imaging microscopy of cellular structure and function</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Millard, Andrew C.; Jin, Lei; Loew, Leslie M.</p> <p>2005-03-01</p> <p>Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) imaging microscopy is an important emerging technique for biological research, with many advantages over existing one- or two-photon fluorescence techniques. A non-linear phenomenon employing mode-locked Ti:sapphire or fiber-based lasers, SHG results in intrinsic optical sectioning without the need for a confocal aperture. Furthermore, as a second-order process SHG is confined to loci lacking a center of symmetry. Many important structural proteins such as collagen and cellulose show intrinsic SHG, thus providing access to sub-resolution information on symmetry. However, we are particularly interested here in "resonance-enhanced" SHG from styryl dyes. In general SHG is a combination of a true second-order process and a third-order process dependent on a static electric field, such that SHG from membrane-bound dyes depends on a cell's trans-membrane potential. With simultaneous patch-clamping and non-linear imaging of cells, we have found that SHG is a sensitive probe of trans-membrane potential with sensitivities that are up to four times better than those obtained under optimal conditions using one-photon fluorescence imaging. With the sensitivity of SHG to local electric fields from other sources such as the membrane dipole potential as well as the quadratic dependence of SHG on concentration, we have found that SHG imaging of styryl dyes is also a powerful technique for the investigation of lipid phases and rafts and for the visualization of the dynamics of membrane-vesicle fusion following fertilization of an ovum.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996PhDT.........2N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996PhDT.........2N"><span id="translatedtitle">Optical Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> Studies of Electrochemical Interfaces</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nagy, Gabor</p> <p></p> <p>Optical second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) is an intrinsically surface sensitive tool that can be used to probe a wide variety of surface processes. In this work, SHG is employed to study the surface behavior of three polycrystalline electrodes, Cu, Ni, and brass, in an electrochemical environment. For the Cu electrode, SHG is used to examine the surface during oxidation and reduction in halide and non -halide electrolytes. The optical data indicate the probable formation of previously undetected small, resonant Cu clusters which are stabilized by Cu-halide crystallites on the electrode surface. The surface charge dependence of SHG is explored at a polycrystalline Ni electrode in the absence of faradaic reactions. The resulting correlation between surface charge and SHG indicates that in an electrochemical environment, the DC field activated contribution to the second order susceptibility plays the dominant role in SHG from Ni. Also with the polycrystalline Ni electrode, the behavior of the SH signal during the electrodeposition of Ag on the Ni surface is examined. The analysis of the optical data in conjunction with a diffusion limited Ag island growth model indicates that the SH signal experiences an electromagnetic enhancement on the Ni surface as a result of the Ag islands. The charge dependence of the SH signal is examined on a polycrystalline alpha-brass electrode in the absence of faradaic reactions, with two incident wavelengths. The experiments show that, as is the case with Cu, SHG from brass may (depending on the incident wavelength) also involve an interband transition and can be affected by a charge dependent Stark shift of the interband transition threshold. The brass electrode is also examined with SHG in a potential region where the selective dissolution of the surface Zn sites is known to occur. By using a layer-by-layer reordering model of the dissolving surface, the electrochemical data is correlated with simultaneously obtained optical SHG data to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23005628','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23005628"><span id="translatedtitle">Oriented rotational wave-packet dynamics studies via high <span class="hlt">harmonic</span> <span class="hlt">generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Frumker, E; Hebeisen, C T; Kajumba, N; Bertrand, J B; Wörner, H J; Spanner, M; Villeneuve, D M; Naumov, A; Corkum, P B</p> <p>2012-09-14</p> <p>We produce oriented rotational wave packets in CO and measure their characteristics via high <span class="hlt">harmonic</span> <span class="hlt">generation</span>. The wave packet is created using an intense, femtosecond laser pulse and its second <span class="hlt">harmonic</span>. A delayed 800 nm pulse probes the wave packet, <span class="hlt">generating</span> even-order high <span class="hlt">harmonics</span> that arise from the broken symmetry induced by the orientation dynamics. The even-order <span class="hlt">harmonic</span> radiation that we measure appears on a zero background, enabling us to accurately follow the temporal evolution of the wave packet. Our measurements reveal that, for the conditions optimum for <span class="hlt">harmonic</span> <span class="hlt">generation</span>, the orientation is produced by preferential ionization which depletes the sample of molecules of one orientation. PMID:23005628</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OptSp.120..808L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OptSp.120..808L"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in nanoscale films of transition metal chalcogenides: Taking into account multibeam interference</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lavrov, S. D.; Kudryavtsev, A. V.; Shestakova, A. P.; Kulyuk, L.; Mishina, E. D.</p> <p>2016-05-01</p> <p>Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> is studied in structures containing nanoscale layers of transition metal chalcogenides that are two-dimensional semiconductors and deposited on a SiO2/Si substrate. The second <span class="hlt">harmonic</span> <span class="hlt">generation</span> intensity is calculated with allowance for multibeam interference in layers of dichalcogenide and silicon oxide. The coefficient of reflection from the SiO2-layer-based Fabry-Perot cavity is subsequently calculated for pump wave fields initiating nonlinear polarization at every point of dichalcogenide, which is followed by integration of all second <span class="hlt">harmonic</span> waves <span class="hlt">generated</span> by this polarization. Calculated second <span class="hlt">harmonic</span> intensities are presented as functions of dichalcogenide and silicon oxide layer thicknesses. The dependence of the second <span class="hlt">harmonic</span> intensity on the MoS2 layer thickness is studied experimentally in the layer of 2-140 nm. A good coincidence of the experimental data and numerical simulation results has been obtained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27137258','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27137258"><span id="translatedtitle">Effect of nuclear motion on spectral broadening of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yuan, Xiaolong; Wei, Pengfei; Liu, Candong; Ge, Xiaochun; Zheng, Yinghui; Zeng, Zhinan; Li, Ruxin</p> <p>2016-04-18</p> <p>High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) in molecular targets is experimentally investigated in order to reveal the role of the nuclear motion played in the <span class="hlt">harmonic</span> <span class="hlt">generation</span> process. An obvious broadening in the <span class="hlt">harmonic</span> spectrum from the H<sub>2</sub> molecule is observed in comparison with the <span class="hlt">harmonic</span> spectrum <span class="hlt">generated</span> from other molecules with relatively heavy nuclei. We also find that the <span class="hlt">harmonic</span> yield from the H<sub>2</sub> molecule is much weaker than the yield from those gas targets with the similar ionization potentials, such as Ar atom and N<sub>2</sub> molecule. The yield suppression and the spectrum broadening of HHG can be attributed to the vibrational motion of nuclear induced by the driving laser pulse. Moreover, the one-dimensional (1D) time-dependent Schrödinger equation (TDSE) with the non-Born-Oppenheimer (NBO) treatment is numerically solved to provide a theoretical support to our explanation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhB.122..248N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhB.122..248N"><span id="translatedtitle">Enhanced third <span class="hlt">harmonic</span> <span class="hlt">generation</span> in air by two-colour ultrashort laser pulses</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nath, Arpita; Dharmadhikari, J. A.; Mathur, D.; Dharmadhikari, A. K.</p> <p>2016-09-01</p> <p>We report on third <span class="hlt">harmonic</span> <span class="hlt">generation</span> in air in a non-filamentation regime using tightly focused, ultrashort laser pulses (1-2 µm wavelength). Enhancement in the third <span class="hlt">harmonic</span> efficiency is observed from co-propagating laser pulses of two different wavelengths which emanate from the same source—an optical parametric amplifier—and are spatially and temporally overlapped. The third <span class="hlt">harmonic</span> efficiency for signal wavelength (1.35 µm) is measured to be 4 × 10-3 %; in the presence of idler wavelength (2.09 µm), the corresponding value becomes 1.6 × 10-2 %—a fourfold enhancement in efficiency. The pulse duration of the <span class="hlt">generated</span> third <span class="hlt">harmonic</span> is measured to be 37 fs. We examine the possible role of plasma to account for the observed enhancement in third <span class="hlt">harmonic</span> <span class="hlt">generation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27137258','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27137258"><span id="translatedtitle">Effect of nuclear motion on spectral broadening of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yuan, Xiaolong; Wei, Pengfei; Liu, Candong; Ge, Xiaochun; Zheng, Yinghui; Zeng, Zhinan; Li, Ruxin</p> <p>2016-04-18</p> <p>High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) in molecular targets is experimentally investigated in order to reveal the role of the nuclear motion played in the <span class="hlt">harmonic</span> <span class="hlt">generation</span> process. An obvious broadening in the <span class="hlt">harmonic</span> spectrum from the H<sub>2</sub> molecule is observed in comparison with the <span class="hlt">harmonic</span> spectrum <span class="hlt">generated</span> from other molecules with relatively heavy nuclei. We also find that the <span class="hlt">harmonic</span> yield from the H<sub>2</sub> molecule is much weaker than the yield from those gas targets with the similar ionization potentials, such as Ar atom and N<sub>2</sub> molecule. The yield suppression and the spectrum broadening of HHG can be attributed to the vibrational motion of nuclear induced by the driving laser pulse. Moreover, the one-dimensional (1D) time-dependent Schrödinger equation (TDSE) with the non-Born-Oppenheimer (NBO) treatment is numerically solved to provide a theoretical support to our explanation. PMID:27137258</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22489962','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22489962"><span id="translatedtitle">Third <span class="hlt">harmonic</span> <span class="hlt">generation</span> in air ambient and laser ablated carbon plasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Singh, Ravi Pratap Gupta, Shyam L.; Thareja, Raj K.</p> <p>2015-12-15</p> <p>We report the third <span class="hlt">harmonic</span> <span class="hlt">generation</span> of a nanosecond laser pulse (1.06 μm) in air ambient and in the presence of nanoparticles from laser ablated carbon plasma. Significant decrease in the threshold of third <span class="hlt">harmonic</span> <span class="hlt">generation</span> and multi-fold increment in the intensity of <span class="hlt">generated</span> third <span class="hlt">harmonic</span> is observed in presence of carbon plasma. The third <span class="hlt">harmonic</span> in air is due to the quasi-resonant four photon process involving vibrationally excited states of molecular ion of nitrogen due to electron impact ionization and laser pulse. Following optical emission spectroscopic observations we conclude that the presence of C{sub 2} and CN in the ablated plume play a vital role in the observed third <span class="hlt">harmonic</span> signals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22412675','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22412675"><span id="translatedtitle">Resonant second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in a gallium nitride two-dimensional photonic crystal on silicon</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zeng, Y.; Roland, I.; Checoury, X.; Han, Z.; El Kurdi, M.; Sauvage, S.; Boucaud, P.; Gayral, B.; Brimont, C.; Guillet, T.; Mexis, M.; Semond, F.</p> <p>2015-02-23</p> <p>We demonstrate second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in a gallium nitride photonic crystal cavity embedded in a two-dimensional free-standing photonic crystal platform on silicon. The photonic crystal nanocavity is optically pumped with a continuous-wave laser at telecom wavelengths in the transparency window of the nitride material. The <span class="hlt">harmonic</span> <span class="hlt">generation</span> is evidenced by the spectral range of the emitted signal, the quadratic power dependence vs. input power, and the spectral dependence of second <span class="hlt">harmonic</span> signal. The <span class="hlt">harmonic</span> emission pattern is correlated to the <span class="hlt">harmonic</span> polarization <span class="hlt">generated</span> by the second-order nonlinear susceptibilities χ{sub zxx}{sup (2)}, χ{sub zyy}{sup (2)} and the electric fields of the fundamental cavity mode.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27610851','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27610851"><span id="translatedtitle">Enhancing High-Order <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> in Light Molecules by Using Chirped Pulses.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lara-Astiaso, M; Silva, R E F; Gubaydullin, A; Rivière, P; Meier, C; Martín, F</p> <p>2016-08-26</p> <p>One of the current challenges in high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> is to extend the <span class="hlt">harmonic</span> cutoff to increasingly high energies while maintaining or even increasing the efficiency of the high-<span class="hlt">harmonic</span> emission. Here we show that the combined effect of down-chirped pulses and nuclear dynamics in light molecules allows one to achieve this goal, provided that long enough IR pulses are used to allow the nuclei to move well outside the Franck-Condon region. We also show that, by varying the duration of the chirped pulse or by performing isotopic substitution while keeping the pulse duration constant, one can control the extension of the <span class="hlt">harmonic</span> plateau. PMID:27610851</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvL.117i3003L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvL.117i3003L"><span id="translatedtitle">Enhancing High-Order <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> in Light Molecules by Using Chirped Pulses</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lara-Astiaso, M.; Silva, R. E. F.; Gubaydullin, A.; Rivière, P.; Meier, C.; Martín, F.</p> <p>2016-08-01</p> <p>One of the current challenges in high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> is to extend the <span class="hlt">harmonic</span> cutoff to increasingly high energies while maintaining or even increasing the efficiency of the high-<span class="hlt">harmonic</span> emission. Here we show that the combined effect of down-chirped pulses and nuclear dynamics in light molecules allows one to achieve this goal, provided that long enough IR pulses are used to allow the nuclei to move well outside the Franck-Condon region. We also show that, by varying the duration of the chirped pulse or by performing isotopic substitution while keeping the pulse duration constant, one can control the extension of the <span class="hlt">harmonic</span> plateau.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24726796','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24726796"><span id="translatedtitle">Experimental observation of cumulative second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> of lamb waves propagating in long bones.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Zhenggang; Liu, Dan; Deng, Mingxi; Ta, Dean; Wang, Weiqi</p> <p>2014-07-01</p> <p>The experimental observation of cumulative second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> of fundamental Lamb waves in long bones is reported. Based on the modal expansion approach to waveguide excitation and the dispersion characteristics of Lamb waves in long bones, the mechanism underlying the <span class="hlt">generation</span> and accumulation of second <span class="hlt">harmonics</span> by propagation of the fundamental Lamb waves was investigated. An experimental setup was established to detect the second-<span class="hlt">harmonic</span> signals of Lamb wave propagation in long bones in vitro. Through analysis of the group velocities of the received signals, the appropriate fundamental Lamb wave modes and the duration of the second-<span class="hlt">harmonic</span> signals could be identified. The integrated amplitude of the time-domain second-<span class="hlt">harmonic</span> signal was introduced and used to characterize the efficiency of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> by fundamental Lamb wave propagation. The results indicate that the second-<span class="hlt">harmonic</span> signal <span class="hlt">generated</span> by fundamental Lamb waves propagating in long bones can be observed clearly, and the effect was cumulative with propagation distance when the fundamental Lamb wave mode and the double-frequency Lamb wave mode had the same phase velocities. The present results may be important in the development of a new method to evaluate the status of long bones using the cumulative second <span class="hlt">harmonic</span> of ultrasonic Lamb waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11863678','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11863678"><span id="translatedtitle">Second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> with pulses in a coupled-resonator optical waveguide.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mookherjea, Shayan; Yariv, Amnon</p> <p>2002-02-01</p> <p>We describe the <span class="hlt">generation</span> and propagation of pulses in a coupled-resonator optical waveguide driven by a nonlinear polarization using a method closely related to the coupled-mode theory. The specific example we consider is that of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span>. This formalism explicitly accounts for temporal dependencies in the waveguide field distributions and in their representations in terms of slowly modulated Bloch wave functions, in contrast with the equations obtained previously for cw second-<span class="hlt">harmonic</span> <span class="hlt">generation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4293601','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4293601"><span id="translatedtitle">Spatial properties of odd and even low order <span class="hlt">harmonics</span> <span class="hlt">generated</span> in gas</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lambert, G.; Andreev, A.; Gautier, J.; Giannessi, L.; Malka, V.; Petralia, A.; Sebban, S.; Stremoukhov, S.; Tissandier, F.; Vodungbo, B.; Zeitoun, Ph.</p> <p>2015-01-01</p> <p>High <span class="hlt">harmonic</span> <span class="hlt">generation</span> in gases is developing rapidly as a soft X-ray femtosecond light-source for applications. This requires control over all the <span class="hlt">harmonics</span> characteristics and in particular, spatial properties have to be kept very good. In previous literature, measurements have always included several <span class="hlt">harmonics</span> contrary to applications, especially spectroscopic applications, which usually require a single <span class="hlt">harmonic</span>. To fill this gap, we present here for the first time a detailed study of completely isolated <span class="hlt">harmonics</span>. The contribution of the surrounding <span class="hlt">harmonics</span> has been totally suppressed using interferential filtering which is available for low <span class="hlt">harmonic</span> orders. In addition, this allows to clearly identify behaviors of standard odd orders from even orders obtained by frequency-mixing of a fundamental laser and of its second <span class="hlt">harmonic</span>. Comparisons of the spatial intensity profiles, of the spatial coherence and of the wavefront aberration level of 5ω at 160 nm and 6ω at 135 nm have then been performed. We have established that the fundamental laser beam aberrations can cause the appearance of a non-homogenous donut-shape in the 6ω spatial intensity distribution. This undesirable effect can be easily controlled. We finally conclude that the spatial quality of an even <span class="hlt">harmonic</span> can be as excellent as in standard <span class="hlt">generation</span>. PMID:25585715</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008SPIE.7279E..0SL','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008SPIE.7279E..0SL"><span id="translatedtitle">Preparation and second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in Pb-doped oxide glasses</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Qiming; Wang, Mingliang; Zhao, Xiujian</p> <p>2008-12-01</p> <p>PbO-B2O3 glasses were prepared by traditional melting method. XRD and optical spectra measurements were done to check properties. Second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> was observed in the glasses induced by thermal treatment and thermally poling process, respectively. But second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> intensity was normally larger for the later, and it increased with increasing PbO content, poling voltage, temperature and time. The mechanism of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in the PbO-B2O3 glasses was also discussed. A promising material for all-optical switching devices is expected.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004OptCo.237...65L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004OptCo.237...65L"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in ZnO thin films fabricated by metalorganic chemical vapor deposition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, C. Y.; Zhang, B. P.; Binh, N. T.; Segawa, Y.</p> <p>2004-07-01</p> <p>Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) from ZnO thin films fabricated by metalorganic chemical vapor deposition (MOCVD) technique was carried out. By comparing the second <span class="hlt">harmonic</span> signal <span class="hlt">generated</span> in a series of ZnO films with different deposition temperatures, we conclude that a significant part of second <span class="hlt">harmonic</span> signal is <span class="hlt">generated</span> at the film deposited with appropriate temperature. The second-order susceptibility tensor χ(2)zzz=9.2 pm/V was deduced for a film deposited at 250 °C.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JEMat..41.1686S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JEMat..41.1686S"><span id="translatedtitle"><span class="hlt">Acoustic</span> Optimization of Automotive Exhaust Heat Thermoelectric <span class="hlt">Generator</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Su, C. Q.; Ye, B. Q.; Guo, X.; Hui, P.</p> <p>2012-06-01</p> <p>The potential for thermoelectric exhaust heat recovery in vehicles has been increasing with recent advances in the efficiency of thermoelectric <span class="hlt">generators</span> (TEGs). This study analyzes the <span class="hlt">acoustic</span> attenuation performance of exhaust-based TEGs. The <span class="hlt">acoustic</span> characteristics of two different thermal designs of exhaust gas heat exchanger in TEGs are discussed in terms of transmission loss and <span class="hlt">acoustic</span> insertion loss. GT-Power simulations and bench tests on a dynamometer with a high-performance production engine are carried out. Results indicate that the <span class="hlt">acoustic</span> attenuation of TEGs could be determined and optimized. In addition, the feasibility of integration of exhaust-based TEGs and engine mufflers into the exhaust line is tested, which can help to reduce space and improve vehicle integration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ApPhL.100j2404M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ApPhL.100j2404M"><span id="translatedtitle">Nonlinearly <span class="hlt">generated</span> <span class="hlt">harmonic</span> signals in ultra-small waveguides with magnetic films: Tunable enhancements of 2nd and 4th <span class="hlt">harmonics</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marsh, J.; Zagorodnii, V.; Celinski, Z.; Camley, R. E.</p> <p>2012-03-01</p> <p>The nonlinear <span class="hlt">generation</span> of high <span class="hlt">harmonic</span> signals (up to 5th <span class="hlt">harmonic</span>) is explored in an ultra-small waveguide which contains a thin ferromagnetic film. The strength of the different <span class="hlt">harmonics</span> is highly tunable. In particular, the power in the 2nd and 4th <span class="hlt">harmonic</span> signals may be enhanced by over two orders of magnitude by varying the direction of a static magnetic field with respect to the long axis of the waveguide. In contrast, the 3rd and 5th <span class="hlt">harmonics</span> are relatively insensitive to the direction of the magnetic field. The experimental results are explained by analytical and numerical calculations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21407878','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21407878"><span id="translatedtitle">Signatures of symmetry and electronic structure in high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> in polyatomic molecules</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wong, M. C. H.; Brichta, J.-P.; Bhardwaj, V. R.</p> <p>2010-06-15</p> <p>We report detailed measurements of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> in chloromethane molecules (CCl{sub 4}, CHCl{sub 3}, and CH{sub 2}Cl{sub 2}) to show that fingerprints of symmetry and electronic structure can be decoded from high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> even in complex randomly oriented molecules. In our measurements, orbital symmetries of these molecules are manifested as both extended <span class="hlt">harmonic</span> cutoffs and a local minimum in the ellipticity dependence of the cut-off <span class="hlt">harmonics</span>, suggesting the occurrence of quantum interferences during ionization. The <span class="hlt">harmonic</span> spectra exhibit distinct interference minima at {approx}42 and {approx}60 eV. We attribute the former to the Cooper minimum in the photoionization cross section and the latter to intramolecular interference during the recombination process.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27576922','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27576922"><span id="translatedtitle">Fully integrated reflection-mode photoacoustic, two-photon, and second <span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy in vivo.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Song, Wei; Xu, Qiang; Zhang, Yang; Zhan, Yang; Zheng, Wei; Song, Liang</p> <p>2016-01-01</p> <p>The ability to obtain comprehensive structural and functional information from intact biological tissue in vivo is highly desirable for many important biomedical applications, including cancer and brain studies. Here, we developed a fully integrated multimodal microscopy that can provide photoacoustic (optical absorption), two-photon (fluorescence), and second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) information from tissue in vivo, with intrinsically co-registered images. Moreover, using a delicately designed optical-<span class="hlt">acoustic</span> coupling configuration, a high-frequency miniature ultrasonic transducer was integrated into a water-immersion optical objective, thus allowing all three imaging modalities to provide a high lateral resolution of ~290 nm with reflection-mode imaging capability, which is essential for studying intricate anatomy, such as that of the brain. Taking advantage of the complementary and comprehensive contrasts of the system, we demonstrated high-resolution imaging of various tissues in living mice, including microvasculature (by photoacoustics), epidermis cells, cortical neurons (by two-photon fluorescence), and extracellular collagen fibers (by SHG). The intrinsic image co-registration of the three modalities conveniently provided improved visualization and understanding of the tissue microarchitecture. The reported results suggest that, by revealing complementary tissue microstructures in vivo, this multimodal microscopy can potentially facilitate a broad range of biomedical studies, such as imaging of the tumor microenvironment and neurovascular coupling. PMID:27576922</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5006040','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5006040"><span id="translatedtitle">Fully integrated reflection-mode photoacoustic, two-photon, and second <span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy in vivo</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Song, Wei; Xu, Qiang; Zhang, Yang; Zhan, Yang; Zheng, Wei; Song, Liang</p> <p>2016-01-01</p> <p>The ability to obtain comprehensive structural and functional information from intact biological tissue in vivo is highly desirable for many important biomedical applications, including cancer and brain studies. Here, we developed a fully integrated multimodal microscopy that can provide photoacoustic (optical absorption), two-photon (fluorescence), and second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) information from tissue in vivo, with intrinsically co-registered images. Moreover, using a delicately designed optical-<span class="hlt">acoustic</span> coupling configuration, a high-frequency miniature ultrasonic transducer was integrated into a water-immersion optical objective, thus allowing all three imaging modalities to provide a high lateral resolution of ~290 nm with reflection-mode imaging capability, which is essential for studying intricate anatomy, such as that of the brain. Taking advantage of the complementary and comprehensive contrasts of the system, we demonstrated high-resolution imaging of various tissues in living mice, including microvasculature (by photoacoustics), epidermis cells, cortical neurons (by two-photon fluorescence), and extracellular collagen fibers (by SHG). The intrinsic image co-registration of the three modalities conveniently provided improved visualization and understanding of the tissue microarchitecture. The reported results suggest that, by revealing complementary tissue microstructures in vivo, this multimodal microscopy can potentially facilitate a broad range of biomedical studies, such as imaging of the tumor microenvironment and neurovascular coupling. PMID:27576922</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...632240S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...632240S"><span id="translatedtitle">Fully integrated reflection-mode photoacoustic, two-photon, and second <span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy in vivo</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Song, Wei; Xu, Qiang; Zhang, Yang; Zhan, Yang; Zheng, Wei; Song, Liang</p> <p>2016-08-01</p> <p>The ability to obtain comprehensive structural and functional information from intact biological tissue in vivo is highly desirable for many important biomedical applications, including cancer and brain studies. Here, we developed a fully integrated multimodal microscopy that can provide photoacoustic (optical absorption), two-photon (fluorescence), and second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) information from tissue in vivo, with intrinsically co-registered images. Moreover, using a delicately designed optical-<span class="hlt">acoustic</span> coupling configuration, a high-frequency miniature ultrasonic transducer was integrated into a water-immersion optical objective, thus allowing all three imaging modalities to provide a high lateral resolution of ~290 nm with reflection-mode imaging capability, which is essential for studying intricate anatomy, such as that of the brain. Taking advantage of the complementary and comprehensive contrasts of the system, we demonstrated high-resolution imaging of various tissues in living mice, including microvasculature (by photoacoustics), epidermis cells, cortical neurons (by two-photon fluorescence), and extracellular collagen fibers (by SHG). The intrinsic image co-registration of the three modalities conveniently provided improved visualization and understanding of the tissue microarchitecture. The reported results suggest that, by revealing complementary tissue microstructures in vivo, this multimodal microscopy can potentially facilitate a broad range of biomedical studies, such as imaging of the tumor microenvironment and neurovascular coupling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27410560','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27410560"><span id="translatedtitle">Two-color high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in plasmas: efficiency dependence on the <span class="hlt">generating</span> particle properties.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Emelina, Anna S; Emelin, Mikhail Yu; Ganeev, Rashid A; Suzuki, Masayuki; Kuroda, Hiroto; Strelkov, Vasily V</p> <p>2016-06-27</p> <p>The high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) in silver, gold, and zinc plasma plumes irradiated by orthogonally polarized two-color field is studied theoretically and experimentally. We find an increase of the HHG efficiency in comparison with the single-color case, which essentially depends on the plasma species and <span class="hlt">harmonic</span> order. An increase of more than an order of magnitude is observed for silver plasma, whereas for gold and zinc it is lower; these results are reproduced in our calculations that include both propagation and microscopic response studies. We show that the widely used theoretical approach assuming the 1s ground state of the <span class="hlt">generating</span> particle fails to reproduce the experimental results; the agreement is achieved in our theory using the actual quantum numbers of the outer electron of the <span class="hlt">generating</span> particles. Moreover, our theoretical studies highlight the redistribution of the electronic density in the continuum wave packet as an important aspect of the HHG enhancement in the two-color orthogonally polarized fields with comparable intensities: in the single-color field the electronic trajectories with almost zero return energy are the most populated ones; in the two-color case the total field maximum can be shifted in time so that the trajectories with high return energies (in particular, the cut-off trajectory) become the most populated ones. PMID:27410560</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvP...4c4004R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvP...4c4004R"><span id="translatedtitle">Anisotropic Swirling Surface <span class="hlt">Acoustic</span> Waves from Inverse Filtering for On-Chip <span class="hlt">Generation</span> of <span class="hlt">Acoustic</span> Vortices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Riaud, Antoine; Thomas, Jean-Louis; Charron, Eric; Bussonnière, Adrien; Bou Matar, Olivier; Baudoin, Michael</p> <p>2015-09-01</p> <p>From radio-electronics signal analysis to biological sample actuation, surface <span class="hlt">acoustic</span> waves (SAWs) are involved in a multitude of modern devices. However, only the most simple standing or progressive waves such as plane and focused waves have been explored so far. In this paper, we expand the SAW toolbox with a wave family named "swirling surface <span class="hlt">acoustic</span> waves" which are the 2D anisotropic analogue of bulk <span class="hlt">acoustic</span> vortices. Similarly to their 3D counterpart, they appear as concentric structures of bright rings with a phase singularity in their center resulting in a central dark spot. After the rigorous mathematical definition of these waves, we synthesize them experimentally through the inverse filtering technique revisited for surface waves. For this purpose, we design a setup combining arrays of interdigitated transducers and a multichannel electronic that enables one to synthesize any prescribed wave field compatible with the anisotropy of the substrate in a region called the "<span class="hlt">acoustic</span> scene." This work opens prospects for the design of integrated <span class="hlt">acoustic</span> vortex <span class="hlt">generators</span> for on-chip selective <span class="hlt">acoustic</span> tweezing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1045058','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1045058"><span id="translatedtitle">Systematic Review and <span class="hlt">Harmonization</span> of Life Cycle GHG Emission Estimates for Electricity <span class="hlt">Generation</span> Technologies (Presentation)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Heath, G.</p> <p>2012-06-01</p> <p>This powerpoint presentation to be presented at the World Renewable Energy Forum on May 14, 2012, in Denver, CO, discusses systematic review and <span class="hlt">harmonization</span> of life cycle GHG emission estimates for electricity <span class="hlt">generation</span> technologies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/225031','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/225031"><span id="translatedtitle">Frequency-resolved optical grating using surface third-<span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tsang, T.; Krumbuegel, M.A.; Delong, K.W.; Fittinghoff, D.N.; Trebino, R.</p> <p>1995-11-01</p> <p>We demonstrate the frequency-resolved optical grating technique using third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> on the surface of a cover glass with ultra-short optical pulses and compare that with the phase-retrieved spectrogram.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22036811','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22036811"><span id="translatedtitle">Low-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> in metal ablation plasmas in nanosecond and picosecond laser regimes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lopez-Arias, M.; Oujja, M.; Sanz, M.; Castillejo, M.; Ganeev, R. A.; Boltaev, G. S.; Satlikov, N. Kh.; Tugushev, R. I.; Usmanov, T.</p> <p>2012-02-15</p> <p>Low-order <span class="hlt">harmonics</span>, third and fifth, of IR (1064 nm) laser emission have been produced in laser ablation plasmas of the metals manganese, copper and silver. The <span class="hlt">harmonics</span> were <span class="hlt">generated</span> in a process triggered by laser ablation followed by frequency up-conversion of a fundamental laser beam that propagates parallel to the target surface. These studies were carried out in two temporal regimes by creating the ablation plasma using either nanosecond or picosecond pulses and then probing the plasma plume with pulses of the same duration. The spatiotemporal behavior of the <span class="hlt">generated</span> <span class="hlt">harmonics</span> was characterized and reveals the distinct composition and dynamics of the plasma species that act as nonlinear media, allowing the comparison of different processes that control the <span class="hlt">generation</span> efficiency. These results serve to guide the choice of laser ablation plasmas to be used for efficient high <span class="hlt">harmonic</span> <span class="hlt">generation</span> of laser radiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhA...49C5501G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhA...49C5501G"><span id="translatedtitle">On <span class="hlt">acoustic</span> wave <span class="hlt">generation</span> in uniform shear flow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gogoberidze, G.</p> <p>2016-07-01</p> <p>The linear dynamics of <span class="hlt">acoustic</span> waves and vortices in uniform shear flow is studied. For flows with very low shear rates, the dynamics of perturbations is adiabatic and can be described by the WKB approximation. However, for flows with moderate and high shear rates the WKB approximation is not appropriate, and alternative analysis shows that two important phenomena occur: <span class="hlt">acoustic</span> wave over-reflection and wave <span class="hlt">generation</span> by vortices. The later phenomenon is a known linear mechanisms for sound <span class="hlt">generation</span> in shear flows, a mechanism that is related to the continuous spectrum that arises in linear shear flow dynamics. A detailed analytical study of these phenomena is performed and the main quantitative and qualitative characteristics of the radiated <span class="hlt">acoustic</span> field are obtained and analyzed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhPl...23h3120L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhPl...23h3120L"><span id="translatedtitle"><span class="hlt">Generation</span> of ultra-intense gamma-ray train by QED <span class="hlt">harmonics</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Chen; Shen, Baifei; Zhang, Xiaomei; Ji, Liangliang; Wang, Wenpeng; Xu, Jiancai; Zhao, Xueyan; Yi, Longqing; Shi, Yin; Zhang, Lingang; Xu, Tongjun; Pei, Zhikun; Xu, Zhizhan</p> <p>2016-08-01</p> <p>In nonlinear media, photons may combine into a photon of energy and momentum of all those photons. This process, called <span class="hlt">harmonic</span> <span class="hlt">generation</span>, happens in nonlinear crystal, gas, and relativistic plasma. When the laser intensity reaches 1022 W/cm2, QED effects appear and play a significant role in the <span class="hlt">harmonic</span> <span class="hlt">generation</span>. In contrast to the gas and relativistic high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> processes, <span class="hlt">harmonics</span> influenced by QED effects are usually not coherent because of the characteristic of random radiation, while the property of high intensity and ultra-short duration is conserved. In this work, the <span class="hlt">generation</span> of high-order <span class="hlt">harmonics</span> with QED effects is investigated by one- and two-dimensional particle-in-cell simulations. Studies have shown that interacting with a laser pulse with the intensity of I =5.35 ×1023W /cm 2 , such <span class="hlt">harmonics</span> can produce ultra-short gamma-ray train with periodic structures. The period of gamma-ray train is half of the laser period, and the peak intensity is 1.4 ×1022W /cm 2 from one-dimensional simulation when ions are considered immobile. This new <span class="hlt">harmonic</span> production with QED effects are crucial to light-matter interaction in strong field and can be verified in experiments by 10 PW laser facilities in the near future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5043238','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5043238"><span id="translatedtitle">Phase-matched second <span class="hlt">harmonic</span> <span class="hlt">generation</span> with on-chip GaN-on-Si microdisks</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Roland, I.; Gromovyi, M.; Zeng, Y.; El Kurdi, M.; Sauvage, S.; Brimont, C.; Guillet, T.; Gayral, B.; Semond, F.; Duboz, J. Y.; de Micheli, M.; Checoury, X.; Boucaud, P.</p> <p>2016-01-01</p> <p>We demonstrate phase-matched second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in gallium nitride on silicon microdisks. The microdisks are integrated with side-coupling bus waveguides in a two-dimensional photonic circuit. The second <span class="hlt">harmonic</span> <span class="hlt">generation</span> is excited with a continuous wave laser in the telecom band. By fabricating a series of microdisks with diameters varying by steps of 8 nm, we obtain a tuning of the whispering gallery mode resonances for the fundamental and <span class="hlt">harmonic</span> waves. Phase matching is obtained when both resonances are matched with modes satisfying the conservation of orbital momentum, which leads to a pronounced enhancement of frequency conversion. PMID:27687007</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22066633','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22066633"><span id="translatedtitle">High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> of picosecond radiation of moderate intensity in laser plasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Boltaev, G S; Ganeev, Rashid A; Kulagin, I A; Satlikov, N Kh; Usmanov, T</p> <p>2012-10-31</p> <p>The results of investigations into the <span class="hlt">generation</span> of highorder <span class="hlt">harmonics</span> (up to the 21st order) of picosecond ({tau} = 38 ps) Nd : YAG laser radiation in the plasma produced by laser ablation of metal and carbon-containing material surfaces are presented. We demonstrate the feasibility of <span class="hlt">generating</span> high-order <span class="hlt">harmonics</span> in the vacuum ultraviolet spectral range (with radiation wavelengths shorter than 120 nm) in plasmas with an efficiency of {approx}0.7 Multiplication-Sign 10{sup -4}. In carbon-containing plasma, the 7th <span class="hlt">harmonic</span> intensity exceeded that of the 5th one by a factor of seven. (nonlinear optical phenomena)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012QuEle..42A...6B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012QuEle..42A...6B"><span id="translatedtitle">High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> of picosecond radiation of moderate intensity in laser plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boltaev, G. S.; Ganeev, Rashid A.; Kulagin, I. A.; Satlikov, N. Kh; Usmanov, T.</p> <p>2012-10-01</p> <p>The results of investigations into the <span class="hlt">generation</span> of highorder <span class="hlt">harmonics</span> (up to the 21st order) of picosecond (τ = 38 ps) Nd : YAG laser radiation in the plasma produced by laser ablation of metal and carbon-containing material surfaces are presented. We demonstrate the feasibility of <span class="hlt">generating</span> high-order <span class="hlt">harmonics</span> in the vacuum ultraviolet spectral range (with radiation wavelengths shorter than 120 nm) in plasmas with an efficiency of ~0.7 × 10-4. In carbon-containing plasma, the 7th <span class="hlt">harmonic</span> intensity exceeded that of the 5th one by a factor of seven.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ChPhC..40i8102Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ChPhC..40i8102Z"><span id="translatedtitle">Self-seeded FEL wavelength extension with high-gain <span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zeng, Ling; Qin, Weilun; Zhao, Gang; Huang, Senlin; Ding, Yuantao; Huang, Zhirong; Marcus, Gabriel; Liu, Kexin</p> <p>2016-09-01</p> <p>We study a self-seeded high-gain <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HGHG) free-electron laser (FEL) scheme to extend the wavelength of a soft X-ray FEL. This scheme uses a regular self-seeding monochromator to <span class="hlt">generate</span> a seed laser at the wavelength of 1.52 nm, followed by a HGHG configuration to produce coherent, narrow-bandwidth <span class="hlt">harmonic</span> radiations at the GW level. The 2nd and 3rd <span class="hlt">harmonic</span> radiation is investigated with start-to-end simulations. Detailed studies of the FEL performance and shot-to-shot fluctuations are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001PhLA..286..282W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001PhLA..286..282W"><span id="translatedtitle"><span class="hlt">Harmonic</span> <span class="hlt">generation</span> during ultrashort-pulse ultraintense /p-polarized laser interaction with solid target</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, Shuai; Zhan, Ru-Juan; Chen, Ji</p> <p>2001-07-01</p> <p>In this Letter, we developed the “relativistic surface currents” model to investigate the <span class="hlt">harmonic</span> <span class="hlt">generation</span> under the conditions of p-polarized obliquely incident ultrashort-pulse ultraintense laser. As a result of this Letter, up to 70 <span class="hlt">harmonics</span> are <span class="hlt">generated</span> with conversion efficiencies exceeding 10 -6, which is very close to the result from Norreys' experiment and Gibbon's PIC simulations. For highly relativistic regime and nonrelativistic regime of laser power, the <span class="hlt">harmonic</span> conversion efficiencies as a function of laser strength parameter q are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22278045','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22278045"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> from direct band gap quantum dots pumped by femtosecond laser pulses</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Liu, Liwei Wang, Yue; Hu, Siyi; Ren, Yu; Huang, Chen</p> <p>2014-02-21</p> <p>We report on nonlinear optical experiments performed on Cu{sub 2}S quantum dots (QDs) pumped by femtosecond laser pulses. We conduct a theoretical simulation and experiments to determine their second <span class="hlt">harmonic</span> <span class="hlt">generation</span> characteristics. Furthermore, we demonstrate that the QDs have a second <span class="hlt">harmonic</span> <span class="hlt">generation</span> conversion efficiency of up to 76%. Our studies suggest that these Cu{sub 2}S QDs can be used for solar cells, bioimaging, biosensing, and electric detection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22494756','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22494756"><span id="translatedtitle">Raman parametric excitation effect upon the third <span class="hlt">harmonic</span> <span class="hlt">generation</span> by a metallic nanoparticle lattice</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sepehri Javan, N.</p> <p>2015-08-21</p> <p>This work is a theoretical study on third <span class="hlt">harmonic</span> <span class="hlt">generation</span> in the nonlinear propagation of an intense laser pulse through a periodic three-dimensional lattice of nanoparticles. Using a perturbative method, the nonlinear equations that describe the laser–nanoparticle interaction in the weakly relativistic regime are derived. Additionally, the nonlinear dispersion relation and the amplitude of the third <span class="hlt">harmonic</span> are obtained. Finally, the effects of the nanoparticle radius and separation length, the distribution of the nanoparticle electron density, and the laser frequency upon the third <span class="hlt">harmonic</span> efficiency are investigated. In addition to the expected resonance that occurs when the third <span class="hlt">harmonic</span> resonates with the plasmon wave, another resonance appears when the nonlinear interaction of the fundamental mode with the third <span class="hlt">harmonic</span> excites a longitudinal collective plasmon wave via the parametric Raman mechanism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE.9805E..0XG','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE.9805E..0XG"><span id="translatedtitle">Higher and sub-<span class="hlt">harmonic</span> Lamb wave mode <span class="hlt">generation</span> due to debond-induced contact nonlinearity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guha, Anurup; Bijudas, C. R.</p> <p>2016-04-01</p> <p>Non-cumulative higher and sub-<span class="hlt">harmonic</span> Lamb wave mode <span class="hlt">generation</span> as a result of partial-debond of piezoelectric wafer transducers (PWT) bonded onto an Aluminium plate, is numerically investigated and experimentally validated. The influence of excitation frequency on the extent of nonlinearity due to clapping mechanism of the partially-debonded PWTs is discussed. A set of specific frequency range is arrived at based on the Eigen-value and <span class="hlt">Harmonic</span> analyses of PWTs used in the model. It is found that, at these frequencies, which are integral multiple of the first width-direction mode of a PWT, significantly higher amplitudes of higher-<span class="hlt">harmonics</span> are observed. It is also seen that at specific debond-positions and lengths, sharp sub-<span class="hlt">harmonics</span> in addition to higher-<span class="hlt">harmonics</span> are present. Signal processing is carried out using Fast Fourier transform, which is normalized for comparisons.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20718576','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20718576"><span id="translatedtitle">High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> in the presence of a static electric field</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Odzak, S.; Milosevic, D.B.</p> <p>2005-09-15</p> <p>We consider high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> by a linearly polarized laser field and a parallel static electric field. We first develop a modified saddle-point method which enables a quantitative analysis of the <span class="hlt">harmonic</span> spectra even in the presence of Coulomb singularities. We introduce a classification of the saddle-point solutions and show that, in the presence of a static electric field which breaks the inversion symmetry, an additional classification number has to be introduced and that the usual saddle-point approximation and the uniform approximation in the case of the coalescing saddle points have to be modified. The theory developed offers a simple and accurate explanation of the static-field-induced multiplateau structure of the <span class="hlt">harmonic</span> spectra. The longer quantum orbits are responsible for a long extension of the <span class="hlt">harmonic</span> plateau, while the larger initial electron velocities are the reason of lower <span class="hlt">harmonic</span> emission rates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21480234','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21480234"><span id="translatedtitle"><span class="hlt">Generation</span> of inhomogeneous bulk plane <span class="hlt">acoustic</span> modes by laser-induced thermoelastic grating near mechanically free surface</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gusev, Vitalyi</p> <p>2010-06-15</p> <p>The detailed theoretical description of how picosecond plane shear <span class="hlt">acoustic</span> transients can be excited by ultrafast lasers in isotropic media is presented. The processes leading to excitation of inhomogeneous plane bulk compression/dilatation (c/d) and shear <span class="hlt">acoustic</span> modes by transient laser interference pattern at a mechanically free surface of an elastically isotropic medium are analyzed. Both pure modes are dispersive. The modes can be evanescent or propagating. The mechanical displacement vector in both propagating modes is oriented obliquely to the mode propagation direction. Consequently the c/d mode is not purely longitudinal and shear mode is not purely transversal. Each of the propagating modes has a plane wave front parallel to the surface and the amplitude <span class="hlt">harmonically</span> modulated along the surface. Inhomogeneous shear <span class="hlt">acoustic</span> mode cannot be <span class="hlt">generated</span> in isotropic medium by thermal expansion and is excited by mode conversion of laser-<span class="hlt">generated</span> inhomogeneous c/d <span class="hlt">acoustic</span> mode incident on the surface. The spectral transformation function of the laser radiation conversion into shear modes has one of its maxima at a frequency corresponding to transmission from laser-induced <span class="hlt">generation</span> of propagating to laser-induced <span class="hlt">generation</span> of evanescent c/d modes. At this particular frequency the shear waves are due to their Cherenkov emission by bulk longitudinal <span class="hlt">acoustic</span> waves skimming along the laser-irradiated surface, which are <span class="hlt">generated</span> by laser-induced gratings synchronously. There exists an interval of frequencies where only shear <span class="hlt">acoustic</span> modes are launched in the material by laser-induced grating, while c/d modes <span class="hlt">generated</span> by thermoelastic optoacoustic conversion are evanescent. Propagating picosecond plane shear <span class="hlt">acoustic</span> fronts excited by interference pattern of fs-ps laser pulses can be applied for the determination of the shear rigidity by optoacoustic echoes diagnostics of thin films and coatings. Theoretical predictions are correlated with available results</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001SPIE.4325..535H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001SPIE.4325..535H"><span id="translatedtitle">Standing wave pressure fields <span class="hlt">generated</span> in an <span class="hlt">acoustic</span> levitation chamber</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hancock, Andrew; Allen, John S.; Kruse, Dustin E.; Dayton, Paul A.; Kargel, Christian M.; Insana, Michael F.</p> <p>2001-05-01</p> <p>We are developing an <span class="hlt">acoustic</span> levitation chamber for measuring adhesion force strengths among biological cells. Our research has four phases. Phase I, presented here, is concerned with the design and construction of a chamber for trapping cell-sized microbubbles with known properties in <span class="hlt">acoustic</span> standing waves, and examines the theory that describes the standing wave field. A cylindrical chamber has been developed to <span class="hlt">generate</span> a stable <span class="hlt">acoustic</span> standing wave field. The pressure field was mapped using a 0.4-mm needle hydrophone, and experiments were performed using 100 micron diameter unencapsulated air bubbles, 9 micron diameter isobutane-filled microbubbles, and 3 micron diameter decafluorobutane (C4F10)-filled microbubbles, confirming that the net radiation force from the standing wave pressure field tends to band the microbubbles at pressure antinodes, in accordance with theory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/238862','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/238862"><span id="translatedtitle">Ultrahigh <span class="hlt">harmonics</span> <span class="hlt">generation</span> in a FEL with a seed laser</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Goloviznin, V.V.; Amersfoort, P.W. van</p> <p>1995-12-31</p> <p>One of the most challenging problems in modern FEL technology is to operate in the X-ray region, especially in the {open_quotes}water window{close_quotes}. Because of the absence of optical resonators in this range of wavelengths, only a single-pass device may be suitable for this task. The Self-Amplified Spontaneous Emission (SASE) mechanism is now under active discussion as a realistic way to provide high-power coherent emission in the X-ray range. Both the undulator parameters and the electron beam parameters required for the lasing are achieveable at today`s technological level. On the other hand, the SASE approach implies a very long and expensive periodic magnetic structure, typically several tens of meters long. This is mainly because of the rather long build-up time necessary to establish a coherent mode from incoherent noise. A mechanism of shortening this time would be therefore highly desirable. In the present paper we consider a scheme using two undulators and a seed-laser to produce coherent X-ray emission. The first undulator and the seed-laser provide a pre-modulation of the beam while the second undulator serves as a source of coherent spontaneous radiation at a very high <span class="hlt">harmonic</span> of the seed-laser frequency; the whole scheme may then be considered to be an FEL-based frequency upconvertor. The total length of the periodic magnetic structure is shown to be of the order of several meters, nearly an order of magnitude shorter than in the SASE case. For the same beam quality as in the SASE scheme and with realistic seed-laser parameters, the efficiency of the beam pre-modulation at the 50-th (!) <span class="hlt">harmonic</span> is shown to be as high as 15%. The output radiation is tunable between discrete <span class="hlt">harmonics</span> of the seed-frequency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SPIE.9549E..18M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SPIE.9549E..18M"><span id="translatedtitle">Coherent and incoherent second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in liquids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maurice, A.; Benichou, E.; Brevet, P. F.</p> <p>2015-08-01</p> <p>In this paper, the Second <span class="hlt">Harmonic</span> light intensity scattered off a liquid solution upon illumination by an incident fundamental frequency beam is written within a general framework in order to describe its coherent and incoherent contributions. It is shown that this formulation requires the introduction of a correlation function in time, position and orientation. We discuss this framework in light of recent experiments where the interface and the bulk of liquid solutions can be investigated simultaneously. We apply here this analysis to a neat water solution to compare the bulk volume and the interface correlation functions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070022262','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070022262"><span id="translatedtitle">Aero-<span class="hlt">acoustics</span> of Drag <span class="hlt">Generating</span> Swirling Exhaust Flows</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Shah, P. N.; Mobed, D.; Spakovszky, Z. S.; Brooks, T. F.; Humphreys, W. M. Jr.</p> <p>2007-01-01</p> <p>Aircraft on approach in high-drag and high-lift configuration create unsteady flow structures which inherently <span class="hlt">generate</span> noise. For devices such as flaps, spoilers and the undercarriage there is a strong correlation between overall noise and drag such that, in the quest for quieter aircraft, one challenge is to <span class="hlt">generate</span> drag at low noise levels. This paper presents a rigorous aero-<span class="hlt">acoustic</span> assessment of a novel drag concept. The idea is that a swirling exhaust flow can yield a steady, and thus relatively quiet, streamwise vortex which is supported by a radial pressure gradient responsible for pressure drag. Flows with swirl are naturally limited by instabilities such as vortex breakdown. The paper presents a first aero-<span class="hlt">acoustic</span> assessment of ram pressure driven swirling exhaust flows and their associated instabilities. The technical approach combines an in-depth aerodynamic analysis, plausibility arguments to qualitatively describe the nature of <span class="hlt">acoustic</span> sources, and detailed, quantitative <span class="hlt">acoustic</span> measurements using a medium aperture directional microphone array in combination with a previously established Deconvolution Approach for Mapping of <span class="hlt">Acoustic</span> Sources (DAMAS). A model scale engine nacelle with stationary swirl vanes was designed and tested in the NASA Langley Quiet Flow Facility at a full-scale approach Mach number of 0.17. The analysis shows that the <span class="hlt">acoustic</span> signature is comprised of quadrupole-type turbulent mixing noise of the swirling core flow and scattering noise from vane boundary layers and turbulent eddies of the burst vortex structure near sharp edges. The exposed edges are the nacelle and pylon trailing edge and the centerbody supporting the vanes. For the highest stable swirl angle setting a nacelle area based drag coefficient of 0.8 was achieved with a full-scale Overall Sound Pressure Level (OASPL) of about 40dBA at the ICAO approach certification point.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014APS..DMP.K1128Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014APS..DMP.K1128Z"><span id="translatedtitle">Two-color probe of high <span class="hlt">harmonic</span> <span class="hlt">generation</span> from argon atoms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, Zengxiu; Yuan, Jianmin; Meng, Chao; Chen, Wenbo</p> <p>2014-05-01</p> <p>Two-color control of high <span class="hlt">harmonic</span> <span class="hlt">generation</span> has been proven a powerful in situ tool to characterize the intrinsic chirp of attosecond bursts. The weak second <span class="hlt">harmonic</span> pulse introduces a phase modulation of the strong field quantum processes, leading to the <span class="hlt">generation</span> of even-order <span class="hlt">harmonic</span>. We measure the yields of even-order <span class="hlt">harmonics</span> from argon gases as a function of the phase delay between the fundamental and its second <span class="hlt">harmonic</span> pulse. We found that the modulation of even-order <span class="hlt">harmonics</span> exhibits a phase jump around the 28th <span class="hlt">harmonic</span> (48eV), closely resembling the result from. However, we show by varying laser intensity that the phase jump is unlikely to be attributed to the switching from short to long trajectories of HHG near the cut-off. In addition, we demonstrate that the phase of jump depends on the driving laser wavelength. Single-active-electron simulation fails to reproduce the experimental observation. We therefore suspect that multielectron response comes into play for the two-color control of HHG from Argon. Preliminary analysis suggests that there exists competing pathways of HHG from inner orbitals, even for argon atoms whose interaction with strong laser fields is usually assumed well described by SAE approximation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20768719','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20768719"><span id="translatedtitle">Theoretical analysis of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> from a coherent superposition of states</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Milosevic, Dejan B.</p> <p>2006-02-15</p> <p>A quantum theory of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> by a strong laser field in the presence of more bound states is formulated. The obtained numerical and analytical results for a two-state hydrogenlike atom model show that the <span class="hlt">harmonic</span> spectrum consists of two parts: a usual single-state <span class="hlt">harmonic</span> spectrum of odd <span class="hlt">harmonics</span> having the energies (2k+1){omega} and a resonant part with the peaks around the excitation energy {delta}{omega}. The energy of the <span class="hlt">harmonics</span> in the resonant part of the spectrum is equal to {delta}{omega}{+-}{omega}, {delta}{omega}{+-}3{omega}, .... For energies higher than the excitation energy, the resonant part forms a plateau, followed by a cutoff. The emission rate of the <span class="hlt">harmonics</span> in this resonant plateau is many orders of magnitude higher than that of the <span class="hlt">harmonics</span> <span class="hlt">generated</span> in the presence of the ground state alone. The influence of the depletion of the initial states, as well as of the pulse shape and intensity, is analyzed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998APS..DPP.F3F15T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998APS..DPP.F3F15T"><span id="translatedtitle"><span class="hlt">Generation</span> of higher-order <span class="hlt">harmonics</span> from solid targets irradiated with fs-laser pulses</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tsakiris, G. D.</p> <p>1998-11-01</p> <p>The prospect of laser intensities exceeding the 10^19 W/cm^2 level becoming available from table-top, 10 Hz lasers, has given new impetus to the subject of solid <span class="hlt">harmonics</span> [1]. After the initial experiments demonstrating the feasibility of <span class="hlt">harmonic</span> <span class="hlt">generation</span> with fs-laser pulses [2], the current effort is directed towards finding out the link between relevant plasma parameters and <span class="hlt">harmonic</span> <span class="hlt">generation</span>. The questions that arise are what are the limitations inherent to the <span class="hlt">generation</span> mechanism and how one can optimize the <span class="hlt">harmonic</span> yield. For example, in experiments using the Ti:sapphire laser ATLAS at Max-Planck Institut für Quantenoptik [3], it was found that the lower the contrast of the laser pulse the weaker the Iλ^2 scaling of the <span class="hlt">harmonic</span> conversion efficiency. Some of these results are presented and their implications to solid <span class="hlt">harmonic</span> <span class="hlt">generation</span> at higher intensities will be discussed. [1] P. Gibbon, IEEE J. of Q. Elec. 33, 1915 (1997). [2] S. Kohlweyer, et al., Optics Comm. 177, 431 (1995). [3] M. Zepf, et al., submitted for publication in Phys. Rev. Lett.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22408023','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22408023"><span id="translatedtitle">Surface plasma wave assisted second <span class="hlt">harmonic</span> <span class="hlt">generation</span> of laser over a metal film</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chauhan, Santosh; Parashar, J.</p> <p>2015-01-15</p> <p>Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> of laser mode converted surface plasma wave (SPW) over a corrugated metal film is studied. The laser, impinged on the metal film, under attenuated total reflection configuration, excites SPW over the metal–vacuum interface. The excited SPW extends over a much wider surface area than the laser spot cross-section. It exerts a second <span class="hlt">harmonic</span> ponderomotive force on metal electrons, imparting them velocity that beats with the surface ripple to produce a nonlinear current, driving resonant second <span class="hlt">harmonic</span> surface plasma wave.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhPl...20a3303G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhPl...20a3303G"><span id="translatedtitle"><span class="hlt">Generation</span> of high-power tunable terahertz-radiation by nonrelativistic beam-echo <span class="hlt">harmonic</span> effect</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gong, Huarong; Travish, Gil; Xu, Jin; Wei, Yanyu; Feng, Jinjun; Gong, Yubin</p> <p>2013-01-01</p> <p>A new type of terahertz radiation source based on the nonrelativistic electron beam-wave interaction is proposed. Here, the beam echo <span class="hlt">harmonic</span> effect is applied to a traveling wave tube like device. The scheme is configured as a combination of a frequency multiplier and amplifier with, for instance, W-band (millimeter wave) input signals and terahertz output power. A one-dimensional model of this device shows that a 10th order <span class="hlt">harmonic</span>-wave can be <span class="hlt">generated</span> while other <span class="hlt">harmonic</span> waves are suppressed. The device only requires a readily available input source (W-band), and the output frequency can be tuned continuously over a wide band.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23939111','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23939111"><span id="translatedtitle">Seventh-<span class="hlt">harmonic</span> <span class="hlt">generation</span> from tightly focused 2 μm ultrashort pulses in air.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nath, Arpita; Dharmadhikari, Jayashree A; Dharmadhikari, Aditya K; Mathur, Deepak</p> <p>2013-07-15</p> <p>We report <span class="hlt">generation</span> of third, fifth and seventh <span class="hlt">harmonics</span> from air by using tightly focused, ultrashort pulses of short-wave infrared (2 μm) radiation. We have measured the third- and fifth-<span class="hlt">harmonic</span> efficiencies to be 5×10(-5) and ~1.4×10(-5), respectively, with the ratio of fifth-to-third-<span class="hlt">harmonic</span> efficiency being close to 0.28. Our experimental results provide confirmation of expectations of the higher-order Kerr effect model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22113383','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22113383"><span id="translatedtitle"><span class="hlt">Generation</span> of high-power tunable terahertz-radiation by nonrelativistic beam-echo <span class="hlt">harmonic</span> effect</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gong Huarong; Xu Jin; Wei Yanyu; Gong Yubin; Travish, Gil; Feng Jinjun</p> <p>2013-01-15</p> <p>A new type of terahertz radiation source based on the nonrelativistic electron beam-wave interaction is proposed. Here, the beam echo <span class="hlt">harmonic</span> effect is applied to a traveling wave tube like device. The scheme is configured as a combination of a frequency multiplier and amplifier with, for instance, W-band (millimeter wave) input signals and terahertz output power. A one-dimensional model of this device shows that a 10th order <span class="hlt">harmonic</span>-wave can be <span class="hlt">generated</span> while other <span class="hlt">harmonic</span> waves are suppressed. The device only requires a readily available input source (W-band), and the output frequency can be tuned continuously over a wide band.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20971890','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20971890"><span id="translatedtitle">Role of surface plasmon in second <span class="hlt">harmonic</span> <span class="hlt">generation</span> from gold nanorods</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hubert, C.; Billot, L.; Adam, P.-M.; Bachelot, R.; Royer, P.; Grand, J.; Gindre, D.; Dorkenoo, K. D.; Fort, A.</p> <p>2007-04-30</p> <p>The role of surface plasmon in second <span class="hlt">harmonic</span> <span class="hlt">generation</span> from arrays of gold nanorod particles excited by femtosecond laser pulses is investigated as a function of incident light polarization and irradiation wavelength. In addition to photoluminescence, a peak of second <span class="hlt">harmonic</span> is observed and is found to depend on the polarization and wavelength of the fundamental frequency laser beam. In particular, the authors found similarities between extinction spectra of the nanoparticles and spectra of emmitted second <span class="hlt">harmonic</span>. This behavior can be explained by resonant excitation of localized surface plasmon resonances.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996SPIE.2624...42P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996SPIE.2624...42P"><span id="translatedtitle">Laser-<span class="hlt">generated</span> <span class="hlt">acoustic</span> wave studies on tattoo pigment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Paterson, Lorna M.; Dickinson, Mark R.; King, Terence A.</p> <p>1996-01-01</p> <p>A Q-switched alexandrite laser (180 ns at 755 nm) was used to irradiate samples of agar embedded with red, black and green tattoo dyes. The <span class="hlt">acoustic</span> waves <span class="hlt">generated</span> in the samples were detected using a PVDF membrane hydrophone and compared to theoretical expectations. The laser pulses were found to <span class="hlt">generate</span> <span class="hlt">acoustic</span> waves in the black and green samples but not in the red pigment. Pressures of up to 1.4 MPa were produced with irradiances of up to 96 MWcm-2 which is comparable to the irradiances used to clear pigment embedded in skin. The pressure gradient <span class="hlt">generated</span> across pigment particles was approximately 1.09 X 1010 Pam-1 giving a pressure difference of 1.09 +/- 0.17 MPa over a particle with mean diameter 100 micrometers . This is not sufficient to permanently damage skin which has a tensile strength of 7.4 MPa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20657985','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20657985"><span id="translatedtitle">Relativistic second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> of a laser from underdense plasmas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Singh, K.P.; Gupta, D.N.; Yadav, Sushila; Tripathi, V.K.</p> <p>2005-01-01</p> <p>A high intensity laser obliquely incident on a vacuum-plasma interface produces second-<span class="hlt">harmonic</span> radiation in the reflected component. The efficiency of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> increases with the angle of incidence, up to critical angle of incidence (our model is not valid beyond critical angle of incidence). The efficiency also depends on electron density, showing a maximum at {omega}{sub p}{sup 2}/{omega}{sup 2} congruent with 0.7, where {omega}{sub p} and {omega} are relativistic plasma frequency and laser frequency, respectively. The efficiency of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> increases sharply with laser intensity in the nonrelativistic regime and saturates at higher intensities. The intensity of the second <span class="hlt">harmonic</span> is proportional to square of the laser intensity at low pump laser intensities and tends to proportional to laser intensity in the strong relativistic regime.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22392260','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22392260"><span id="translatedtitle">High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> using a high-repetition-rate turnkey laser</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lorek, E. Larsen, E. W.; Heyl, C. M.; Carlström, S.; Mauritsson, J.; Paleček, D.; Zigmantas, D.</p> <p>2014-12-15</p> <p>We <span class="hlt">generate</span> high-order <span class="hlt">harmonics</span> at high pulse repetition rates using a turnkey laser. High-order <span class="hlt">harmonics</span> at 400 kHz are observed when argon is used as target gas. In neon, we achieve <span class="hlt">generation</span> of photons with energies exceeding 90 eV (∼13 nm) at 20 kHz. We measure a photon flux of up to 4.4 × 10{sup 10} photons per second per <span class="hlt">harmonic</span> in argon at 100 kHz. Many experiments employing high-order <span class="hlt">harmonics</span> would benefit from higher repetition rates, and the user-friendly operation opens up for applications of coherent extreme ultra-violet pulses in new research areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25554271','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25554271"><span id="translatedtitle">High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> using a high-repetition-rate turnkey laser.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lorek, E; Larsen, E W; Heyl, C M; Carlström, S; Paleček, D; Zigmantas, D; Mauritsson, J</p> <p>2014-12-01</p> <p>We <span class="hlt">generate</span> high-order <span class="hlt">harmonics</span> at high pulse repetition rates using a turnkey laser. High-order <span class="hlt">harmonics</span> at 400 kHz are observed when argon is used as target gas. In neon, we achieve <span class="hlt">generation</span> of photons with energies exceeding 90 eV (∼13 nm) at 20 kHz. We measure a photon flux of up to 4.4 × 10(10) photons per second per <span class="hlt">harmonic</span> in argon at 100 kHz. Many experiments employing high-order <span class="hlt">harmonics</span> would benefit from higher repetition rates, and the user-friendly operation opens up for applications of coherent extreme ultra-violet pulses in new research areas. PMID:25554271</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21643072','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21643072"><span id="translatedtitle">Coupled 2D Ag nano-resonator chains for enhanced and spatially tailored second <span class="hlt">harmonic</span> <span class="hlt">generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Centini, Marco; Benedetti, Alessio; Sibilia, Concita; Bertolotti, Mario</p> <p>2011-04-25</p> <p>We report results of second <span class="hlt">harmonic</span> <span class="hlt">generation</span> calculations performed on Silver coupled 2D-nanoresonators. Coupling is responsible for the creation of resonant modes that can be localized on small portions of the structure or distributed over the whole structure. Different field profiles can be obtained by varying the parameters of the input field (i.e. the wavelength). The second <span class="hlt">harmonic</span> <span class="hlt">generation</span> nonlinear process is enhanced by the excitation of coupled surface plasmon polaritons. The emitted field is strongly affected by the linear properties of the structure behaving as a nano antenna. We note that different configurations of the pump field lead to different second <span class="hlt">harmonic</span> far-field emission patterns. Also, we show that the angular emission of the second <span class="hlt">harmonic</span> field contains information about the spatial location of the pump field hot spots at different frequencies. Applications to a new class of nano sources for single molecule fluorescence and sensors are proposed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22489950','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22489950"><span id="translatedtitle">High <span class="hlt">harmonic</span> <span class="hlt">generation</span> in underdense plasmas by intense laser pulses with orbital angular momentum</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mendonça, J. T.; Vieira, J.</p> <p>2015-12-15</p> <p>We study high <span class="hlt">harmonic</span> <span class="hlt">generation</span> produced by twisted laser pulses, with orbital angular momentum in the relativistic regime, for pulse propagation in underdense plasma. We consider fast time scale processes associated with an ultra-short pulse, where the ion motion can be neglected. We use both analytical models and numerical simulations using a relativistic particle-in-cell code. The present description is valid for relativistic laser intensities, when the normalized field amplitude is much larger than one, a ≫ 1. We also discuss two distinct processes associated with linear and circular polarization. Using both analytical solutions and particle-in-cell simulations, we are able to show that, for laser pulses in a well defined Laguerre-Gauss mode, angular momentum conservation is observed during the process of <span class="hlt">harmonic</span> <span class="hlt">generation</span>. Intensity modulation of the <span class="hlt">harmonic</span> spectrum is also verified, as imposed by the nonlinear time-scale for energy transfer between different <span class="hlt">harmonics</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25725651','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25725651"><span id="translatedtitle">Subharmonic <span class="hlt">generation</span>, chaos, and subharmonic resurrection in an <span class="hlt">acoustically</span> driven fluid-filled cavity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cantrell, John H; Adler, Laszlo; Yost, William T</p> <p>2015-02-01</p> <p>Traveling wave solutions of the nonlinear <span class="hlt">acoustic</span> wave equation are obtained for the fundamental and second <span class="hlt">harmonic</span> resonances of a fluid-filled cavity. The solutions lead to the development of a non-autonomous toy model for cavity oscillations. Application of the Melnikov method to the model equation predicts homoclinic bifurcation of the Smale horseshoe type leading to a cascade of period doublings with increasing drive displacement amplitude culminating in chaos. The threshold value of the drive displacement amplitude at tangency is obtained in terms of the <span class="hlt">acoustic</span> drive frequency and fluid attenuation coefficient. The model prediction of subharmonic <span class="hlt">generation</span> leading to chaos is validated from acousto-optic diffraction measurements in a water-filled cavity using a 5 MHz <span class="hlt">acoustic</span> drive frequency and from the measured frequency spectrum in the bifurcation cascade regime. The calculated resonant threshold amplitude of 0.2 nm for tangency is consistent with values estimated for the experimental set-up. Experimental evidence for the appearance of a stable subharmonic beyond chaos is reported. PMID:25725651</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22405044','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22405044"><span id="translatedtitle">Subharmonic <span class="hlt">generation</span>, chaos, and subharmonic resurrection in an <span class="hlt">acoustically</span> driven fluid-filled cavity</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cantrell, John H. Yost, William T.; Adler, Laszlo</p> <p>2015-02-15</p> <p>Traveling wave solutions of the nonlinear <span class="hlt">acoustic</span> wave equation are obtained for the fundamental and second <span class="hlt">harmonic</span> resonances of a fluid-filled cavity. The solutions lead to the development of a non-autonomous toy model for cavity oscillations. Application of the Melnikov method to the model equation predicts homoclinic bifurcation of the Smale horseshoe type leading to a cascade of period doublings with increasing drive displacement amplitude culminating in chaos. The threshold value of the drive displacement amplitude at tangency is obtained in terms of the <span class="hlt">acoustic</span> drive frequency and fluid attenuation coefficient. The model prediction of subharmonic <span class="hlt">generation</span> leading to chaos is validated from acousto-optic diffraction measurements in a water-filled cavity using a 5 MHz <span class="hlt">acoustic</span> drive frequency and from the measured frequency spectrum in the bifurcation cascade regime. The calculated resonant threshold amplitude of 0.2 nm for tangency is consistent with values estimated for the experimental set-up. Experimental evidence for the appearance of a stable subharmonic beyond chaos is reported.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20711699','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20711699"><span id="translatedtitle">Nonlinear <span class="hlt">harmonic</span> <span class="hlt">generation</span> in high-gain free-electron lasers</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dattoli, G.; Ottaviani, P.L.; Pagnutti, S.</p> <p>2005-06-01</p> <p>We reconsider the derivation of semianalytical expressions providing the most significant aspects of the high-gain free-electron laser dynamics. We obtain new expressions for the growth of the laser power, of the e-beam-induced energy spread, and of the higher-order nonlinearly <span class="hlt">generated</span> <span class="hlt">harmonics</span>. The procedure we employ, based on theoretical ansatz and fitting methods, allows the determination of crucial quantities like the expected <span class="hlt">harmonic</span> output power and its dependences on the e-beam parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19365469','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19365469"><span id="translatedtitle">Using the self-filtering property of a femtosecond filament to improve second <span class="hlt">harmonic</span> <span class="hlt">generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shwa, David; Eisenmann, Shmuel; Marcus, Gilad; Zigler, Arie</p> <p>2009-04-13</p> <p>In this paper we demonstrate the use of NIR femtosecond filament for improving the <span class="hlt">generation</span> of second <span class="hlt">harmonic</span> using a type I BBO crystal. Using this method the beam propagation factor (M(2)) of the second <span class="hlt">harmonic</span> was improved significantly; which led to enhancement of the attainable SH intensity by up to two orders of magnitude. This method can be beneficial for applications demanding high intensities, small spot size or long interaction lengths.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986JAP....60R..83S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986JAP....60R..83S"><span id="translatedtitle">Laser <span class="hlt">generation</span> of <span class="hlt">acoustic</span> waves in liquids and gases</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sigrist, Markus W.</p> <p>1986-10-01</p> <p>The laser <span class="hlt">generation</span> of sound in liquids and gases is reviewed. The sound-<span class="hlt">generating</span> mechanisms of laser interaction with matter are discussed with emphasis on the thermoelastic process. The studies on strongly absorbing liquids include detailed theoretical considerations of the thermoelastic sound <span class="hlt">generation</span> with pulsed lasers. <span class="hlt">Acoustic</span> waveforms for H2O and D2O are calculated analytically on the basis of a model laser-pulse shape. Both free and rigid boundaries on the surface of the liquid are considered. Good agreement between theory and experiments with respect to waveforms and amplitudes is obtained. The experiments are performed with a hybrid CO2 laser and piezoelectric or optical detection of the <span class="hlt">acoustic</span> transients. In view of a present controversy, special emphasis is put on the temperature dependence of the <span class="hlt">acoustic</span> amplitudes in H2O, D2O, and in aqueous MgSO4 solutions. Good agreement is found between experimental data and a new, pure thermal model which takes heat conduction into account. The distortion of the <span class="hlt">acoustic</span> waveform during the propagation through the liquid is treated in terms of sound absorption, diffraction, and nonlinear <span class="hlt">acoustics</span>. A simple experimental method for the determination of Beyer's nonlinearity parameter B/A is presented. In the last section some characteristics of photoacoustic spectroscopy (PAS) in gaseous media are reviewed. This method has been demonstrated to be highly sensitive. The measurement of absorption coefficients as low as 10-8 cm-1 is possible. PA studies on H2O vapor are discussed with new results on line and continuum absorption in the 9-11-μm wavelength range. Finally, the impact of PAS on trace gas analysis is demonstrated. With PAS the detection of gas concentrations in the ppb range is feasible. The operational characteristics of a stationary CO laser and a mobile CO2 laser-PAS system are presented, including first results on continuous in situ air pollution monitoring.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ApSS..278...33L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ApSS..278...33L"><span id="translatedtitle">Low-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> in nanosecond laser ablation plasmas of carbon containing materials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lopez-Quintas, I.; Oujja, M.; Sanz, M.; Martín, M.; Ganeev, R. A.; Castillejo, M.</p> <p>2013-08-01</p> <p>In this work we report on a systematic study of the spatiotemporal behaviour of low-order <span class="hlt">harmonics</span> <span class="hlt">generated</span> in nanosecond laser ablation plasmas of carbon containing materials. Plasmas were <span class="hlt">generated</span> from targets of graphite and boron carbide ablated with a nanosecond Q-switched Nd:YAG laser at 1064 nm. Low-order <span class="hlt">harmonics</span> (3rd and 5th) of the fundamental wavelength of a ns Nd:YAG driving laser, propagating perpendicularly to the ablation laser at variable time delays, were observed. The temporal study of the low-order <span class="hlt">harmonics</span> <span class="hlt">generated</span> under vacuum and atmospheres of Kr and Xe, revealed the presence of two populations that contribute to the <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HG) at different times. It was found that under vacuum only small species contribute to the HG process, whereas under buffer gas, heavier species, such as clusters and nanoparticles, contribute to the HG at longer times. Optical emission spectroscopy, time of flight mass spectrometry and characterization of deposits collected on-line on a nearby substrate provided additional information that complemented the results of the spatiotemporal study of the <span class="hlt">generated</span> <span class="hlt">harmonics</span>. This approach to ablation plume analysis allows elucidating the identity of the nonlinear emitters in laser ablation plasmas and facilitates the investigation of efficient, nanoparticle-enhanced, coherent short wavelength <span class="hlt">generation</span> processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15011697','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15011697"><span id="translatedtitle">Self Excitation and <span class="hlt">Harmonics</span> in Wind Power <span class="hlt">Generation</span>: Preprint</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Muljadi, E.; Butterfield, C. P.; Romanowitz, H.; Yinger, R.</p> <p>2004-11-01</p> <p>Traditional wind turbines are equipped with induction <span class="hlt">generators</span>. Induction <span class="hlt">generators</span> are preferred because they are inexpensive, rugged, and require very little maintenance. Unfortunately, induction <span class="hlt">generators</span> require reactive power from the grid to operate. Because reactive power varies with the output power, the terminal voltage at the <span class="hlt">generator</span> may become too low to compensate the induction <span class="hlt">generator</span>. The interactions among the wind turbine, the power network, and the capacitor compensation, are important aspects of wind <span class="hlt">generation</span>. In this paper, we will show the interactions among the induction <span class="hlt">generator</span>, capacitor compensation, power system network, and magnetic saturations and examine the cause of resonance conditions and self-excitation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ChPhB..25h4209L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ChPhB..25h4209L"><span id="translatedtitle">Spectral modulation of third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> by molecular alignment and preformed plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Min; Li, An-Yuan; He, Bo-Qu; Yuan, Shuai; Zeng, He-Ping</p> <p>2016-08-01</p> <p>We demonstrate spectral modulation of third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> from molecular alignment effects. The third <span class="hlt">harmonic</span> spectrum is broadened or narrowed under different influences of cross-phase modulations originating from various molecular alignment revivals. Furthermore, the spectrum and spatial distribution of the <span class="hlt">generated</span> third <span class="hlt">harmonic</span> pulse change dramatically in the presence of a preformed plasma. Under the influence of a preformed plasma, a narrower third <span class="hlt">harmonic</span> spectrum is observed, and the conical third-<span class="hlt">harmonic</span> pulse increases while the axial part decreases. The investigation provides an effective method to modulate the spectral characteristic and spatial distribution of third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> from intense femtosecond filament. Project supported by the National Key Scientific Instrument Project, China (Grant No. 2012YQ150092), the National Basic Research Program of China (Grant No. 2011CB808105), the National Natural Science Foundation of China (Grant No. 11434005), China Postdoctoral Science Foundation (Grant No. 2014M560348), the National Natural Science Foundation of China (Grant No. 11504237), and the Shanghai Municipal Science and Technology Commission, China (Grant No. 14JC1401600).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006OptCo.267..498K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006OptCo.267..498K"><span id="translatedtitle">Effects of electron relaxation on multiple <span class="hlt">harmonic</span> <span class="hlt">generation</span> from metal surfaces with femtosecond laser pulses</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karatzas, N. E.; Georges, A. T.</p> <p>2006-11-01</p> <p>Calculations are presented for the first four (odd and even) <span class="hlt">harmonics</span> of an 800 nm laser from a gold surface, with pulse widths ranging from 100 down to 14 fs. For peak laser intensities above 1 GW/cm 2 the <span class="hlt">harmonics</span> are enhanced because of a partial depletion of the initial electron states. At 10 11 W/cm 2 of peak laser intensity the calculated conversion efficiency for 2nd-<span class="hlt">harmonic</span> <span class="hlt">generation</span> is 3 × 10 -9, while for the 5th-<span class="hlt">harmonic</span> it is 10 -10. The <span class="hlt">generated</span> <span class="hlt">harmonic</span> pulses are broadened and delayed relative to the laser pulse because of the finite relaxation times of the excited electronic states. The finite electron relaxation times cause also the broadening of the autocorrelations of the laser pulses obtained from surface <span class="hlt">harmonic</span> <span class="hlt">generation</span> by two time-delayed identical pulses. Comparison with recent experimental results shows that the response time of an autocorrelator using nonlinear optical processes in a gold surface is shorter than the electron relaxation times. This seems to indicate that for laser pulses shorter than ˜30 fs, the fast nonresonant channel for multiphoton excitation via continuum-continuum transitions in metals becomes important as the resonant channel becomes slow (relative to the laser pulse) and less efficient.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27498825','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27498825"><span id="translatedtitle">Surface area-dependent second <span class="hlt">harmonic</span> <span class="hlt">generation</span> from silver nanorods.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ngo, Hoang Minh; Luong, Thanh Tuyen; Ledoux-Rak, Isabelle</p> <p>2016-08-17</p> <p>The nonlinear optical (NLO) properties of metallic nanoparticles strongly depend on their size and shape. Metallic gold nanorods have already been widely investigated, but other noble metals could also be used for nanorod fabrication towards applications in photonics. Here we report on the synthesis and NLO characterization of silver nanorods (AgNRs) with controllable localized surface plasmon resonance. We have implemented an original, one-step and seedless synthesis method, based on a spontaneous particle growth technique in the presence of polyvinylpyrrolidone (PVP) as a capping agent. Colloidal solutions of AgNRs with various aspect ratios (5.0; 6.3; 7.5; 8.2 and 9.7) have been obtained and characterized using <span class="hlt">Harmonic</span> light scattering (HLS) at 1064 nm, in order to investigate their quadratic NLO properties. From HLS experiments, we demonstrate that hyperpolarizability (β) values of AgNRs display a strong dependence on their surface area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27498825','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27498825"><span id="translatedtitle">Surface area-dependent second <span class="hlt">harmonic</span> <span class="hlt">generation</span> from silver nanorods.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ngo, Hoang Minh; Luong, Thanh Tuyen; Ledoux-Rak, Isabelle</p> <p>2016-08-17</p> <p>The nonlinear optical (NLO) properties of metallic nanoparticles strongly depend on their size and shape. Metallic gold nanorods have already been widely investigated, but other noble metals could also be used for nanorod fabrication towards applications in photonics. Here we report on the synthesis and NLO characterization of silver nanorods (AgNRs) with controllable localized surface plasmon resonance. We have implemented an original, one-step and seedless synthesis method, based on a spontaneous particle growth technique in the presence of polyvinylpyrrolidone (PVP) as a capping agent. Colloidal solutions of AgNRs with various aspect ratios (5.0; 6.3; 7.5; 8.2 and 9.7) have been obtained and characterized using <span class="hlt">Harmonic</span> light scattering (HLS) at 1064 nm, in order to investigate their quadratic NLO properties. From HLS experiments, we demonstrate that hyperpolarizability (β) values of AgNRs display a strong dependence on their surface area. PMID:27498825</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhyE...78...31C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhyE...78...31C"><span id="translatedtitle">Laser induced third <span class="hlt">harmonic</span> <span class="hlt">generation</span> in δ-Bi1-xNdxB3O6 nanocomposites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chrunik, By M.; Ebothé, J.; Aloufy, A. K.; Majchrowski, A.; Jaroszewicz, L. R.; Kityk, I. V.</p> <p>2016-04-01</p> <p>A possibility of optically operated third <span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) in polymer nanocomposites based on orthorhombic δ-Bi1-xNdxB3O6 powders (where x=0.025÷0.100) is presented. The nanoparticles were fabricated using polymeric precursor method. The particles were <span class="hlt">acoustically</span> milled and then they were embedded into polyvinyl alcohol (PVA) photopolymer matrix. After solidification the additional photoinducing treatment was performed by two coherent 1064 nm Nd:YAG laser beams. The angle between the photoinducing beams and their polarization was varied in order to achieve the maximum of THG. THG efficiency was monitored immediately after Nd:YAG laser treatment at different temperatures. The photoinduced THG was explored versus the Nd3+ content and temperature. Origin of the effect is discussed within a framework of phenomenological description.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016aams.book..185Z&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016aams.book..185Z&link_type=ABSTRACT"><span id="translatedtitle">High-order <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> Driven by Sub-Cycle Shaped Laser Field</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zheng, Yinghui; Zeng, Zhinan; Wei, Pengfei; Miao, Jing; Li, Ruxin; Xu, Zhizhan</p> <p></p> <p>High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> can be described by the semiclassical three-step model, in which an electron is freed, accelerated away from an atom or molecule by a strong oscillating laser field, and then, upon reversal of the field, careened back into its parent ion. The shaped laser field has been proved to be an effective tool to control the three-step process and consequently to achieve the high intensity <span class="hlt">harmonic</span> <span class="hlt">generation</span> or an isolated attosecond pulse <span class="hlt">generation</span> by changing the relative phase, intensity ratio, polarization, etc, between the pulses of shaped laser field. High-order <span class="hlt">harmonic</span> and attosecond pulse <span class="hlt">generation</span> driven by a shaped laser field synthesized with two or three laser pulses of controlled related phase are reviewed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3799667','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3799667"><span id="translatedtitle">Imaging the bipolarity of myosin filaments with Interferometric Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> microscopy</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Rivard, Maxime; Couture, Charles-André; Miri, Amir K.; Laliberté, Mathieu; Bertrand-Grenier, Antony; Mongeau, Luc; Légaré, François</p> <p>2013-01-01</p> <p>We report that combining interferometry with Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> (SHG) microscopy provides valuable information about the relative orientation of noncentrosymmetric structures composing tissues. This is confirmed through the imaging of rat medial gastrocnemius muscle. The inteferometric Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> (ISHG) images reveal that each side of the myosin filaments composing the A band of the sarcomere <span class="hlt">generates</span> π phase shifted SHG signal which implies that the myosin proteins at each end of the filaments are oriented in opposite directions. This highlights the bipolar structural organization of the myosin filaments and shows that muscles can be considered as a periodically poled biological structure. PMID:24156065</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPhCS.584a2002Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPhCS.584a2002Z"><span id="translatedtitle">Structural light focusing phenomenon and enhanced second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in NaNO2-infiltrated opal photonic crystal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zaytsev, Kirill I.; Katyba, Gleb M.; Yakovlev, Egor V.; Aliev, Ismail N.; Khorokhorov, Alexey M.; Yurchenko, Stanislav O.</p> <p>2015-01-01</p> <p>We report new experimental results on enhanced second <span class="hlt">harmonic</span> <span class="hlt">generation</span> using a structural light focusing phenomenon in photonic crystals (PCs). We use opal-based PC, infiltrated with NaNO2 and pumped with femtosecond laser pulses at various incidence angles, in order to examine the dependence of second <span class="hlt">harmonic</span> <span class="hlt">generation</span> efficiency on the pumping wavelength location toward the PC band-gap. We demonstrate one order enhancement of second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in case of PC band-gap pumping in comparison to non-band- gap pumping. Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> is performed in reflection mode with the maximum of <span class="hlt">generation</span> in the direction of mirror reflection. We demonstrate that the spectrum of second <span class="hlt">harmonic</span> does not narrow with the quasi-phase matching condition in case of band-gap <span class="hlt">generation</span>, and second <span class="hlt">harmonic</span> spectrum corresponding to non-band-gap <span class="hlt">generation</span> undergoes 1.5 times narrowing due to the quasi-phase matching.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/125509','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/125509"><span id="translatedtitle">Parallel <span class="hlt">acoustic</span> wave propagation and <span class="hlt">generation</span> of a seismic dataset</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Oldfield, R.; Dyke, J.V.; Semeraro, B.D.</p> <p>1995-12-01</p> <p>The ultimate goal of this work is to construct a large seismic dataset that will be used to calibrate industrial seismic analysis codes. Seismic analysis is used in oil and gas exploration to deduce subterranean geological formations based on the reflection of <span class="hlt">acoustic</span> waves from a source to an array of receivers placed on or near the surface. This work deals with the <span class="hlt">generation</span> of a test set of <span class="hlt">acoustic</span> data based on a known representative geological formation. Industrial users of the data will calibrate their codes by comparing their predicted geology to the know geology used to <span class="hlt">generate</span> the test data. This is a cooperative effort involving Los Alamos, Sandia, Oak Ridge and Lawrence Livermore national labs as well as Institut Francais du Petrole and the Society of Exploration Geophysicists.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1107570','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1107570"><span id="translatedtitle">Device and method for <span class="hlt">generating</span> a beam of <span class="hlt">acoustic</span> energy from a borehole, and applications thereof</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Vu, Cung Khac; Sinha, Dipen N; Pantea, Cristian; Nihei, Kurt T; Schmitt, Denis P; Skelt, Christopher</p> <p>2013-10-01</p> <p>In some aspects of the invention, a method of <span class="hlt">generating</span> a beam of <span class="hlt">acoustic</span> energy in a borehole is disclosed. The method includes <span class="hlt">generating</span> a first <span class="hlt">acoustic</span> wave at a first frequency; <span class="hlt">generating</span> a second <span class="hlt">acoustic</span> wave at a second frequency different than the first frequency, wherein the first <span class="hlt">acoustic</span> wave and second <span class="hlt">acoustic</span> wave are <span class="hlt">generated</span> by at least one transducer carried by a tool located within the borehole; transmitting the first and the second <span class="hlt">acoustic</span> waves into an <span class="hlt">acoustically</span> non-linear medium, wherein the composition of the non-linear medium produces a collimated beam by a non-linear mixing of the first and second <span class="hlt">acoustic</span> waves, wherein the collimated beam has a frequency based upon a difference between the first frequency and the second frequency; and transmitting the collimated beam through a diverging <span class="hlt">acoustic</span> lens to compensate for a refractive effect caused by the curvature of the borehole.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110012036','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110012036"><span id="translatedtitle">Prediction of <span class="hlt">Acoustic</span> Loads <span class="hlt">Generated</span> by Propulsion Systems</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Perez, Linamaria; Allgood, Daniel C.</p> <p>2011-01-01</p> <p>NASA Stennis Space Center is one of the nation's premier facilities for conducting large-scale rocket engine testing. As liquid rocket engines vary in size, so do the <span class="hlt">acoustic</span> loads that they produce. When these <span class="hlt">acoustic</span> loads reach very high levels they may cause damages both to humans and to actual structures surrounding the testing area. To prevent these damages, prediction tools are used to estimate the spectral content and levels of the <span class="hlt">acoustics</span> being <span class="hlt">generated</span> by the rocket engine plumes and model their propagation through the surrounding atmosphere. Prior to the current work, two different <span class="hlt">acoustic</span> prediction tools were being implemented at Stennis Space Center, each having their own advantages and disadvantages depending on the application. Therefore, a new prediction tool was created, using NASA SP-8072 handbook as a guide, which would replicate the same prediction methods as the previous codes, but eliminate any of the drawbacks the individual codes had. Aside from replicating the previous modeling capability in a single framework, additional modeling functions were added thereby expanding the current modeling capability. To verify that the new code could reproduce the same predictions as the previous codes, two verification test cases were defined. These verification test cases also served as validation cases as the predicted results were compared to actual test data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26455302','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26455302"><span id="translatedtitle">Perceptual learning of <span class="hlt">acoustic</span> noise <span class="hlt">generates</span> memory-evoked potentials.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Andrillon, Thomas; Kouider, Sid; Agus, Trevor; Pressnitzer, Daniel</p> <p>2015-11-01</p> <p>Experience continuously imprints on the brain at all stages of life. The traces it leaves behind can produce perceptual learning [1], which drives adaptive behavior to previously encountered stimuli. Recently, it has been shown that even random noise, a type of sound devoid of <span class="hlt">acoustic</span> structure, can trigger fast and robust perceptual learning after repeated exposure [2]. Here, by combining psychophysics, electroencephalography (EEG), and modeling, we show that the perceptual learning of noise is associated with evoked potentials, without any salient physical discontinuity or obvious <span class="hlt">acoustic</span> landmark in the sound. Rather, the potentials appeared whenever a memory trace was observed behaviorally. Such memory-evoked potentials were characterized by early latencies and auditory topographies, consistent with a sensory origin. Furthermore, they were <span class="hlt">generated</span> even on conditions of diverted attention. The EEG waveforms could be modeled as standard evoked responses to auditory events (N1-P2) [3], triggered by idiosyncratic perceptual features acquired through learning. Thus, we argue that the learning of noise is accompanied by the rapid formation of sharp neural selectivity to arbitrary and complex <span class="hlt">acoustic</span> patterns, within sensory regions. Such a mechanism bridges the gap between the short-term and longer-term plasticity observed in the learning of noise [2, 4-6]. It could also be key to the processing of natural sounds within auditory cortices [7], suggesting that the neural code for sound source identification will be shaped by experience as well as by <span class="hlt">acoustics</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvA..94a3846Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvA..94a3846Y"><span id="translatedtitle">Dependence of high-order-<span class="hlt">harmonic</span> <span class="hlt">generation</span> on dipole moment in Si O2 crystals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Chao; Zhang, Xirui; Jiang, Shicheng; Cao, Xu; Yuan, Guanglu; Wu, Tong; Bai, Lihua; Lu, Ruifeng</p> <p>2016-07-01</p> <p>High-order-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in α-quartz Si O2 is theoretically investigated under a strong laser field by solving the extended semiconductor Bloch equations. The accurate band structures as well as dipole moments between different bands are obtained from state-of-the-art first-principles calculations. We find that the shapes of k -space-dependent dipole moments play an important role in <span class="hlt">harmonic</span> <span class="hlt">generation</span>. The calculated results show that <span class="hlt">harmonic</span> conversion efficiency is significantly enhanced and the cutoff energy is distinctly increased when the dipole moments change greatly along a valley in the k direction in the solid. Based on that dependence on the dipole moment, we also show that symmetry groups greatly affect the <span class="hlt">harmonic</span> spectra from the solid materials. Moreover, a two-color synthesized field is used to achieve a supercontinuum <span class="hlt">harmonic</span> spectrum near the cutoff region, and isolated attosecond pulses can be obtained directly by filtering out the <span class="hlt">harmonic</span> radiation. We hope the contribution presented in this work provides a useful reference for future studies on laser-crystal interactions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4354235','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4354235"><span id="translatedtitle">Multi-channel electronic and vibrational dynamics in polyatomic resonant high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ferré, A.; Boguslavskiy, A. E.; Dagan, M.; Blanchet, V.; Bruner, B. D.; Burgy, F.; Camper, A.; Descamps, D.; Fabre, B.; Fedorov, N.; Gaudin, J.; Geoffroy, G.; Mikosch, J.; Patchkovskii, S.; Petit, S.; Ruchon, T.; Soifer, H.; Staedter, D.; Wilkinson, I.; Stolow, A.; Dudovich, N.; Mairesse, Y.</p> <p>2015-01-01</p> <p>High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> in polyatomic molecules generally involves multiple channels of ionization. Their relative contribution can be strongly influenced by the presence of resonances, whose assignment remains a major challenge for high-<span class="hlt">harmonic</span> spectroscopy. Here we present a multi-modal approach for the investigation of unaligned polyatomic molecules, using SF6 as an example. We combine methods from extreme-ultraviolet spectroscopy, above-threshold ionization and attosecond metrology. Fragment-resolved above-threshold ionization measurements reveal that strong-field ionization opens at least three channels. A shape resonance in one of them is found to dominate the signal in the 20–26 eV range. This resonance induces a phase jump in the <span class="hlt">harmonic</span> emission, a switch in the polarization state and different dynamical responses to molecular vibrations. This study demonstrates a method for extending high-<span class="hlt">harmonic</span> spectroscopy to polyatomic molecules, where complex attosecond dynamics are expected. PMID:25608712</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ChPhB..25i4213J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ChPhB..25i4213J"><span id="translatedtitle">Optimization of multi-color laser waveform for high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jin, Cheng; Lin, C. D.</p> <p>2016-09-01</p> <p>With the development of laser technologies, multi-color light-field synthesis with complete amplitude and phase control would make it possible to <span class="hlt">generate</span> arbitrary optical waveforms. A practical optimization algorithm is needed to <span class="hlt">generate</span> such a waveform in order to control strong-field processes. We review some recent theoretical works of the optimization of amplitudes and phases of multi-color lasers to modify the single-atom high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> based on genetic algorithm. By choosing different fitness criteria, we demonstrate that: (i) <span class="hlt">harmonic</span> yields can be enhanced by 10 to 100 times, (ii) <span class="hlt">harmonic</span> cutoff energy can be substantially extended, (iii) specific <span class="hlt">harmonic</span> orders can be selectively enhanced, and (iv) single attosecond pulses can be efficiently <span class="hlt">generated</span>. The possibility of optimizing macroscopic conditions for the improved phase matching and low divergence of high <span class="hlt">harmonics</span> is also discussed. The waveform control and optimization are expected to be new drivers for the next wave of breakthrough in the strong-field physics in the coming years. Project supported by the Fundamental Research Funds for the Central Universities of China (Grant No. 30916011207), Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U. S. Department of Energy (Grant No. DE-FG02-86ER13491), and Air Force Office of Scientific Research, USA (Grant No. FA9550-14-1-0255).</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21408649','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21408649"><span id="translatedtitle">High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> from polyatomic molecules including nuclear motion and a nuclear modes analysis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Madsen, C. B.; Abu-samha, M.; Madsen, L. B.</p> <p>2010-04-15</p> <p>We present a generic approach for treating the effect of nuclear motion in high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> from polyatomic molecules. Our procedure relies on a separation of nuclear and electron dynamics where we account for the electronic part using the Lewenstein model and nuclear motion enters as a nuclear correlation function. We express the nuclear correlation function in terms of Franck-Condon factors, which allows us to decompose nuclear motion into modes and identify the modes that are dominant in the high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> process. We show results for the isotopes CH{sub 4} and CD{sub 4} and thereby provide direct theoretical support for a recent experiment [S. Baker et al., Science 312, 424 (2006)] that uses high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> to probe the ultrafast structural nuclear rearrangement of ionized methane.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17572747','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17572747"><span id="translatedtitle"><span class="hlt">Harmonic</span> signal <span class="hlt">generation</span> and frequency upconversion using selective sideband Brillouin amplification in single-mode fiber.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lee, Kwang-Hyun; Choi, Woo-Young</p> <p>2007-06-15</p> <p><span class="hlt">Harmonic</span> signal <span class="hlt">generation</span> and frequency upconversion at millimeter-wave bands are experimentally demonstrated by using selective sideband Brillouin amplification induced by stimulated Brillouin scattering in a single-mode fiber. The <span class="hlt">harmonic</span> signals and frequency upconverted signals are simultaneously <span class="hlt">generated</span> by the beating of optical sidebands, one of which is Brillouin amplified. By using this method, we successfully demonstrate <span class="hlt">generation</span> of third-<span class="hlt">harmonic</span> millimeter waves at 32.55 GHz with f(LO) of 10.85 GHz and upconversion of 10 Mbps quadrature-shift keyed data at f(IF) of 1.55 GHz into a 30 GHz band with more than 17 dB RF power gain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19800010331','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19800010331"><span id="translatedtitle">Spherical <span class="hlt">harmonic</span> analysis of a synoptic climatology <span class="hlt">generated</span> with a global general circulation model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Christidis, Z. D.; Spar, J.</p> <p>1980-01-01</p> <p>Spherical <span class="hlt">harmonic</span> analysis was used to analyze the observed climatological (C) fields of temperature at 850 mb, geopotential height at 500 mb, and sea level pressure. The spherical <span class="hlt">harmonic</span> method was also applied to the corresponding "model climatological" fields (M) <span class="hlt">generated</span> by a general circulation model, the "GISS climate model." The climate model was initialized with observed data for the first of December 1976 at 00. GMT and allowed to <span class="hlt">generate</span> five years of meteorological history. Monthly means of the above fields for the five years were computed and subjected to spherical <span class="hlt">harmonic</span> analysis. It was found from the comparison of the spectral components of both sets, M and C, that the climate model <span class="hlt">generated</span> reasonable 500 mb geopotential heights. The model temperature field at 850 mb exhibited a generally correct structure. However, the meridional temperature gradient was overestimated and overheating of the continents was observed in summer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE.9717E..0NT','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE.9717E..0NT"><span id="translatedtitle">Enhanced second-<span class="hlt">harmonic-generation</span> detection of collagen by means of optical wavefront shaping</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thompson, Jonathan V.; Throckmorton, Graham A.; Hokr, Brett H.; Yakovlev, Vladislav V.</p> <p>2016-03-01</p> <p>Second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) has proven to be an effective method to both image and detect structural variations in fibrillar collagen. The ability to detect these differences is especially useful in studying diseases like cancer and fibrosis.1 SHG techniques have historically been limited by their ability to penetrate and image through strongly scattering tissues. Recently, optical wavefront shaping has enabled light to be focused through highly scattering media such as biological tissue.2-4 This technology also enables us to examine the dependence of second <span class="hlt">harmonic</span> <span class="hlt">generation</span> on the spatial phase of the pump laser. Here, we demonstrate that wavefront shaping can be used to enhance the <span class="hlt">generation</span> of second <span class="hlt">harmonic</span> light from collagen fibrils even when scattering is low or non-existent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25554882','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25554882"><span id="translatedtitle">Macroscopic manipulation of high-order-<span class="hlt">harmonic</span> <span class="hlt">generation</span> through bound-state coherent control.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hadas, Itai; Bahabad, Alon</p> <p>2014-12-19</p> <p>We propose a paradigm for macroscopic control of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> by modulating the bound-state population of the medium atoms. A unique result of this scheme is that apart from regular spatial quasi-phase-matching (QPM), also purely temporal QPM of the emitted radiation can be established. Our simulations demonstrate temporal QPM by inducing homogenous Rabi oscillations in the medium and also spatial QPM by creating a grating of population inversion using the process of rapid adiabatic passage. In the simulations a scaled version of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> is used: a far off-resonance 2.6  μm source <span class="hlt">generates</span> UV-visible high-order <span class="hlt">harmonics</span> from alkali-metal-atom vapor, while a resonant near IR source is used to coherently control the medium.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25401622','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25401622"><span id="translatedtitle">High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> from Rydberg atoms in inhomogeneous fields.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Zhe; He, Lixin; Luo, Jianghua; Lan, Pengfei; Lu, Peixiang</p> <p>2014-10-20</p> <p>We theoretically investigate the high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) from Rydberg atoms considering the spatial inhomogeneity of the driving field. It is found that in the inhomogeneous field, the effect of the cutoff extension in the <span class="hlt">harmonic</span> spectrum from Rydberg atoms can be extended to multi-cycle regime, while in the homogeneous field case, the extension of the <span class="hlt">harmonic</span> cutoff is limited to the few-cycle regime (less than two optical cycles). The underlying physics of the cutoff extension from Rydberg atoms in the inhomogeneous field is analyzed based on the classical and quantum-mechanical models. Furthermore, by optimizing the field inhomogeneity, the electron dynamics can be well controlled to <span class="hlt">generate</span> a smooth supercontinuum in the extended spectral region. This can support the efficient <span class="hlt">generation</span> of isolated attosecond pulses in Rydberg atoms from multi-cycle laser fields.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/3590362','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/3590362"><span id="translatedtitle"><span class="hlt">Acoustic</span> cavitation <span class="hlt">generated</span> by an extracorporeal shockwave lithotripter.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Coleman, A J; Saunders, J E; Crum, L A; Dyson, M</p> <p>1987-02-01</p> <p>Evidence is presented of <span class="hlt">acoustic</span> cavitation <span class="hlt">generated</span> by a Dornier extracorporeal shockwave lithotripter. Using x-ray film, thin aluminum sheets, and relatively thick metal plates as targets, evidence of liquid jet impacts associated with cavitation bubble collapse was observed. The jet impact was violent enough to puncture thin foils and deform metal plates. Furthermore, numerous jet impacts were <span class="hlt">generated</span> over a volume of greater than 200 cm3. It is likely that such violent cavitation will also occur in tissue, and observed biological effects (e.g. renal calculus disintegration and tissue trauma) may be related to cavitation damage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22043857','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22043857"><span id="translatedtitle">Three-dimensional nanostructures as highly efficient <span class="hlt">generators</span> of second <span class="hlt">harmonic</span> light.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Yu; Grady, Nathaniel K; Ayala-Orozco, Ciceron; Halas, Naomi J</p> <p>2011-12-14</p> <p>Plasmonic nanostructures enable the <span class="hlt">generation</span> of large electromagnetic fields confined to small volumes, potentially providing a route for the development of nanoengineered nonlinear optical media. A metal-capped hemispherical nanoparticle, also known as a nanocup, <span class="hlt">generates</span> second <span class="hlt">harmonic</span> light with increasing intensity as the angle between the incident fundamental beam and the nanocup symmetry axis is increased. Nanoparticle orientation also modifies the emission direction of the second <span class="hlt">harmonic</span> light. With conversion efficiencies similar to those of inorganic SHG crystals, these structures provide a promising approach for the design and fabrication of stable, synthetic second-order nonlinear optical materials tailored for specific wavelengths.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20639965','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20639965"><span id="translatedtitle">High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> at a repetition rate of 100 kHz</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lindner, F.; Stremme, W.; Schaetzel, M. G.; Grasbon, F.; Paulus, G. G.; Walther, H.; Hartmann, R.; Strueder, L.</p> <p>2003-07-01</p> <p>We report high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) in rare gases using a femtosecond laser system with a very high repetition rate (100 kHz) and low pulse energy (7 {mu}J). To our knowledge, this is the highest repetition rate reported to date for HHG. The tight focusing geometry required to reach sufficiently high intensities implies low efficiency of the process. <span class="hlt">Harmonics</span> up to the 45th order are nevertheless <span class="hlt">generated</span> and detected. We show evidence of clear separation and selection of quantum trajectories by moving the gas jet with respect to the focus, in agreement with the theoretical predictions of the semiclassical model of HHG.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21322827','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21322827"><span id="translatedtitle">Multielectron Correlation in High-<span class="hlt">Harmonic</span> <span class="hlt">Generation</span>: A 2D Model Analysis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sukiasyan, Suren; McDonald, Chris; Destefani, Carlos; Brabec, Thomas; Ivanov, Misha Yu.</p> <p>2009-06-05</p> <p>We analyze the role of multielectron dynamics in high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> spectroscopy, using an example of a two-electron system. We identify and systematically quantify the importance of correlation and exchange effects. One of the main sources for correlation is identified to be the polarization of the ion by the recombining continuum electron. This effect, which plays an important qualitative and quantitative role, seriously undermines the validity of the standard approaches to high-<span class="hlt">harmonic</span> <span class="hlt">generation</span>, which ignore the contribution of excited ionic states to the radiative recombination of the continuum electron.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhRvL.112j3902P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhRvL.112j3902P"><span id="translatedtitle">Cavity-Enhanced High-<span class="hlt">Harmonic</span> <span class="hlt">Generation</span> with Spatially Tailored Driving Fields</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pupeza, I.; Högner, M.; Weitenberg, J.; Holzberger, S.; Esser, D.; Eidam, T.; Limpert, J.; Tünnermann, A.; Fill, E.; Yakovlev, V. S.</p> <p>2014-03-01</p> <p>We theoretically and experimentally investigate high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in a 78-MHz enhancement cavity with a transverse mode having on-axis intensity maxima at the focus and minima at an opening in the following mirror. We find that the conversion efficiency is comparable to that achievable with a Gaussian mode, whereas the output coupling efficiency can be significantly improved over any other demonstrated technique. This approach offers additional power scaling advantages and additional degrees of freedom in shaping the <span class="hlt">harmonic</span> emission, paving the way to high-power extreme-ultraviolet frequency combs and the <span class="hlt">generation</span> of multi-MHz repetition-rate-isolated attosecond pulses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1056750','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1056750"><span id="translatedtitle">Life Cycle GHG Emissions from Conventional Natural Gas Power <span class="hlt">Generation</span>: Systematic Review and <span class="hlt">Harmonization</span> (Presentation)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Heath, G.; O'Donoughue, P.; Whitaker, M.</p> <p>2012-12-01</p> <p>This research provides a systematic review and <span class="hlt">harmonization</span> of the life cycle assessment (LCA) literature of electricity <span class="hlt">generated</span> from conventionally produced natural gas. We focus on estimates of greenhouse gases (GHGs) emitted in the life cycle of electricity <span class="hlt">generation</span> from conventionally produced natural gas in combustion turbines (NGCT) and combined-cycle (NGCC) systems. A process we term "<span class="hlt">harmonization</span>" was employed to align several common system performance parameters and assumptions to better allow for cross-study comparisons, with the goal of clarifying central tendency and reducing variability in estimates of life cycle GHG emissions. This presentation summarizes preliminary results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21408320','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21408320"><span id="translatedtitle">Huge enhancement of backward second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> with slow light in photonic crystals</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Iliew, Rumen; Etrich, Christoph; Pertsch, Thomas; Kivshar, Yuri S.</p> <p>2010-02-15</p> <p>We study theoretically forward and backward second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in a two-dimensional photonic crystal structure made of lithium niobate. The aim of this article is twofold: First, we propose a reliable modal algorithm for describing the light propagation taking into account the vectorial character of the interacting fields as well as the tensorial character of the nonlinearity and verify it by means of the nonlinear finite-difference time-domain method. Second, we propose a photonic crystal where we obtain a giant efficiency increase for backward second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> with slow light.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22253993','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22253993"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in photonic crystal cavities in (111)-oriented GaAs</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Buckley, Sonia Radulaski, Marina; Vučković, Jelena; Biermann, Klaus</p> <p>2013-11-18</p> <p>We demonstrate second <span class="hlt">harmonic</span> <span class="hlt">generation</span> at telecommunications wavelengths in photonic crystal cavities in (111)-oriented GaAs. We fabricate 30 photonic crystal structures in both (111)- and (100)-oriented GaAs and observe an increase in <span class="hlt">generated</span> second <span class="hlt">harmonic</span> power in the (111) orientation, with the mean power increased by a factor of 3, although there is a large scatter in the measured values. We discuss possible reasons for this increase, in particular, the reduced two photon absorption for transverse electric modes in (111) orientation, as well as a potential increase due to improved mode overlap.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22488531','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22488531"><span id="translatedtitle">Quadrupole second <span class="hlt">harmonic</span> <span class="hlt">generation</span> and sum-frequency <span class="hlt">generation</span> in ZnO quantum dots</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Maikhuri, Deepti; Purohit, S. P. Mathur, K. C.</p> <p>2015-04-15</p> <p>The second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) and the sum frequency <span class="hlt">generation</span> (SFG) processes are investigated in the conduction band states of the singly charged ZnO quantum dot (QD) embedded in the HfO{sub 2}, and the AlN matrices. With two optical fields of frequency ω{sub p} and ω{sub q} incident on the dot, we study the variation with frequency of the second order nonlinear polarization resulting in SHG and SFG, through the electric dipole and the electric quadrupole interactions of the pump fields with the electron in the dot. We obtain enhanced value of the second order nonlinear susceptibility in the dot compared to the bulk. The effective mass approximation with the finite confining barrier is used for obtaining the energy and wavefunctions of the quantized confined states of the electron in the conduction band of the dot. Our results show that both the SHG and SFG processes depend on the dot size, the surrounding matrix and the polarization states of the pump beams.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17376468','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17376468"><span id="translatedtitle"><span class="hlt">Generation</span> and characterization of surface layers on <span class="hlt">acoustically</span> levitated drops.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tuckermann, Rudolf; Bauerecker, Sigurd; Cammenga, Heiko K</p> <p>2007-06-15</p> <p>Surface layers of natural and technical amphiphiles, e.g., octadecanol, stearic acid and related compounds as well as perfluorinated fatty alcohols (PFA), have been investigated on the surface of <span class="hlt">acoustically</span> levitated drops. In contrast to Langmuir troughs, traditionally used in the research of surface layers at the air-water interface, <span class="hlt">acoustic</span> levitation offers the advantages of a minimized and contact-less technique. Although the film pressure cannot be directly adjusted on <span class="hlt">acoustically</span> levitated drops, it runs through a wide pressure range due to the shrinking surface of an evaporating drop. During this process, different states of the <span class="hlt">generated</span> surface layer have been identified, in particular the phase transition from the gaseous or liquid-expanded to the liquid-condensed state of surface layers of octadecanol and other related amphiphiles. Characteristic parameters, such as the relative permeation resistance and the area per molecule in a condensed surface layer, have been quantified and were found comparable to results obtained from surface layers <span class="hlt">generated</span> on Langmuir troughs. PMID:17376468</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/912251','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/912251"><span id="translatedtitle">Laser-<span class="hlt">Generated</span> Thermoelastic <span class="hlt">Acoustic</span> Sources in Anisotropic Materials</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>David H. Hurley</p> <p>2004-05-01</p> <p>An analytical model appropriate for thermoelastic <span class="hlt">generation</span> of <span class="hlt">acoustic</span> waves in anisotropic materials is presented for both plane and line sources. The interaction of <span class="hlt">acoustic</span> waves produced by subsurface sources with the bounding surface is accounted for using a method of images. For the plane source case, analytical solutions are found that form an appropriate basis for an angular spectrum of plane waves. For the line source case and for specific crystal symmetries and source orientations, it is shown in the limit of strong optical absorption, a buried line source is equivalent to applying a shear stress dipole at the bounding surface. However, contrary to the isotropic case, the character and strength of the equivalent surface stress is a function of propagation direction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvB..93v0301H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvB..93v0301H"><span id="translatedtitle"><span class="hlt">Generation</span> mechanism of terahertz coherent <span class="hlt">acoustic</span> phonons in Fe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Henighan, T.; Trigo, M.; Bonetti, S.; Granitzka, P.; Higley, D.; Chen, Z.; Jiang, M. P.; Kukreja, R.; Gray, A.; Reid, A. H.; Jal, E.; Hoffmann, M. C.; Kozina, M.; Song, S.; Chollet, M.; Zhu, D.; Xu, P. F.; Jeong, J.; Carva, K.; Maldonado, P.; Oppeneer, P. M.; Samant, M. G.; Parkin, S. S. P.; Reis, D. A.; Dürr, H. A.</p> <p>2016-06-01</p> <p>We use femtosecond time-resolved hard x-ray scattering to detect coherent <span class="hlt">acoustic</span> phonons <span class="hlt">generated</span> during ultrafast laser excitation of ferromagnetic bcc Fe films grown on MgO(001). We observe the coherent longitudinal-<span class="hlt">acoustic</span> phonons as a function of wave vector through analysis of the temporal oscillations in the x-ray scattering signal. The width of the extracted strain wave front associated with this coherent motion is ˜100 fs. An effective electronic Grüneisen parameter is extracted within a two-temperature model. However, ab initio calculations show that the phonons are nonthermal on the time scale of the experiment, which calls into question the validity of extracting physical constants by fitting such a two-temperature model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/833034','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/833034"><span id="translatedtitle"><span class="hlt">Generation</span> of GW-Level, Sub-Angstrom Radiation in the LCLS Using a Second-<span class="hlt">Harmonic</span> Radiator</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Huang, Z</p> <p>2004-09-14</p> <p>Electron beams are strongly microbunched near the high-gain free-electron laser (FEL) saturation with a rich <span class="hlt">harmonic</span> content in the beam current. While the coherent <span class="hlt">harmonic</span> emission is possible in a planar undulator, the third-<span class="hlt">harmonic</span> radiation typically dominates with about 1% of the fundamental power at saturation. In this paper, we discuss the second-<span class="hlt">harmonic</span> radiation in the Linac Coherent Light Source. We show that by a suitable design of an second-stage undulator with its fundamental frequency tuned to the second <span class="hlt">harmonic</span> of the first undulator, coherent second-<span class="hlt">harmonic</span> radiation much more intense than the third-<span class="hlt">harmonic</span> is emitted. Numerical simulations predict that GW-level, sub-Angstrom x-ray pulses can be <span class="hlt">generated</span> in a relatively short second-<span class="hlt">harmonic</span> radiator.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21347142','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21347142"><span id="translatedtitle">Free-electron laser <span class="hlt">harmonic</span> <span class="hlt">generation</span> in an electromagnetic-wave wiggler and ion channel guiding</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mehdian, H.; Hasanbeigi, A.; Jafari, S.</p> <p>2010-02-15</p> <p>A theoretical study of electron trajectories, <span class="hlt">harmonic</span> <span class="hlt">generation</span>, and gain in a free-electron laser (FEL) with a linearly polarized electromagnetic-wave wiggler is presented for axial injection of electron beam. The relativistic equation of motion for a single electron has been derived and solved numerically. It is found that the trajectories consist of two regimes. The stability of these regimes has been investigated. The results show that the trajectories are stable except for some parts of the regime one. The effects of interaction on the transverse velocity of the electron are a superposition of two oscillation terms, one at the wiggler frequency and the other at the betatron ion-channel frequency. A detailed analysis of the gain equation in the low-gain-per-pass limit has been employed to investigate FEL operation in higher <span class="hlt">harmonics</span> <span class="hlt">generation</span>. The possibility of wave amplification at both wiggler frequency and betatron ion-channel frequency for their odd <span class="hlt">harmonics</span> has been illustrated.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1650.1592C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1650.1592C"><span id="translatedtitle">Effect of localized microstructural evolution on higher <span class="hlt">harmonic</span> <span class="hlt">generation</span> of guided wave modes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Choi, Gloria; Liu, Yang; Yao, Xiaochu; Lissenden, Cliff J.</p> <p>2015-03-01</p> <p>Higher <span class="hlt">harmonic</span> <span class="hlt">generation</span> of ultrasonic waves has the potential to be used to detect precursors to macroscale damage of phenomenon like fatigue due to microstructural evolution contributing to nonlinear material behavior. Aluminum plates having various plastic zone sizes were plastically deformed to different levels. The fundamental shear horizontal mode was then <span class="hlt">generated</span> in the plate samples via a magnetostrictive transducer. After propagating through the plastic zone the primary wave mode (SH0) and its third <span class="hlt">harmonic</span> (sh0) were received by a second transducer. Results of a parallel numerical study using the S1-s2 Lamb mode pair, where sensitivity to changes in third order elastic constants were investigated, are described within the context of the experimental results. Specimens used within both studies are geometrically similar and have double edge notches for dog bone samples that introduce localized plastic deformation. Through both studies, the size of the plastic zone with respect to the propagation distance and damage intensity influence the higher <span class="hlt">harmonics</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22565675','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22565675"><span id="translatedtitle">Silencing and enhancement of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in optical gap antennas.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Berthelot, Johann; Bachelier, Guillaume; Song, Mingxia; Rai, Padmnabh; Colas des Francs, Gérard; Dereux, Alain; Bouhelier, Alexandre</p> <p>2012-05-01</p> <p>Amplifying local electromagnetic fields by engineering optical interactions between individual constituents of an optical antenna is considered fundamental for efficient nonlinear wavelength conversion in nanometer-scale devices. In contrast to this general statement we show that high field enhancement does not necessarily lead to an optimized nonlinear activity. In particular, we demonstrate that second-<span class="hlt">harmonic</span> responses <span class="hlt">generated</span> at strongly interacting optical gap antennas can be significantly suppressed. Numerical simulations are confirming silencing of second-<span class="hlt">harmonic</span> in these coupled systems despite the existence of local field amplification. We then propose a simple approach to restore and amplify the second-<span class="hlt">harmonic</span> signal by changing the manner in which electrically-connected optical antennas are interacting in the charge-transfer plasmon regime. Our observations provide critical design rules for realizing optimal structures that are essential for a broad variety of nonlinear surface-enhanced characterizations and for realizing the next <span class="hlt">generation</span> of electrically-driven optical antennas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26469591','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26469591"><span id="translatedtitle">High-speed measurement of rotational anisotropy nonlinear optical <span class="hlt">harmonic</span> <span class="hlt">generation</span> using position-sensitive detection.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Harter, J W; Niu, L; Woss, A J; Hsieh, D</p> <p>2015-10-15</p> <p>We present a method of performing high-speed rotational anisotropy nonlinear optical <span class="hlt">harmonic</span> <span class="hlt">generation</span> experiments at rotational frequencies of several hertz by projecting the <span class="hlt">harmonic</span> light reflected at different angles from a sample onto a stationary position-sensitive detector. The high rotational speed of the technique, 10(3) to 10(4) times larger than existing methods, permits precise measurements of the crystallographic and electronic symmetries of samples by averaging over low frequency laser-power, beam-pointing, and pulse-width fluctuations. We demonstrate the sensitivity of our technique by resolving the bulk fourfold rotational symmetry of GaAs about its [001] axis using second-<span class="hlt">harmonic</span> <span class="hlt">generation</span>. PMID:26469591</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21448529','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21448529"><span id="translatedtitle">Role of ellipticity in high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> by homonuclear diatomic molecules</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Odzak, S.; Milosevic, D. B.</p> <p>2010-08-15</p> <p>We present a theory of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> by diatomic molecules exposed to an elliptically polarized laser field. This theory is based on the molecular strong-field approximation with the laser-field-dressed initial bound state and the undressed final state. The interference minima, observed for linear polarization, are blurred with the increase of the laser-field ellipticity. The nth <span class="hlt">harmonic</span> emission rate has contributions of the components of the T-matrix element in the direction of the laser-field polarization and in the direction perpendicular to it. We analyze the destructive interference condition for this perpendicular component. Taking into account that the aligned molecules are an anisotropic medium for high-<span class="hlt">harmonic</span> <span class="hlt">generation</span>, we introduce elliptic dichroism as a measure of this anisotropy and discuss possibilities of its use for determining the molecular structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004ChOpL...2..534W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004ChOpL...2..534W"><span id="translatedtitle"><span class="hlt">Generation</span> of the numerator = 2 rational <span class="hlt">harmonic</span> mode-locked pulses in fiber ring lasers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Pinghe; Zhan, Li; Ye, Qinghao; Xia, Yuxing</p> <p>2004-09-01</p> <p>In conventional rational <span class="hlt">harmonic</span> mode-locking, optical pulse trains with the repetition rate of (pn+1)f_(c) are <span class="hlt">generated</span> when the modulation frequency of the in-cavity modulator is set at f_(m)=(n+1/p)f_(c), where n and p are both integers, f_(c) is the fundamental cavity frequency. In this paper, we report that rational <span class="hlt">harmonic</span> mode locking phenomenon takes place in the fiber lasers when the modulation frequency is set at f_(m)=(n+2/p)f_(c). The pulse <span class="hlt">generations</span> are experimentally demonstrated when the numerator of the rational corresponds to 2 in 5th and 7th order rational <span class="hlt">harmonic</span> mode-locking.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1303909','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1303909"><span id="translatedtitle">Sensitivity of Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> from Styryl Dyes to Transmembrane Potential</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Millard, Andrew C.; Jin, Lei; Wei, Mei-de; Wuskell, Joseph P.; Lewis, Aaron; Loew, Leslie M.</p> <p>2004-01-01</p> <p>In this article we present results from the simultaneous nonlinear (second <span class="hlt">harmonic</span> <span class="hlt">generation</span> and two-photon excitation fluorescence) imaging and voltage clamping of living cells. Specifically, we determine the sensitivity to transmembrane potential of second <span class="hlt">harmonic</span> <span class="hlt">generation</span> by ANEP-chromophore styryl dyes as a function of excitation wavelength and dye structure. We have measured second <span class="hlt">harmonic</span> sensitivities of up to 43% per 100 mV, more than a factor of four better than the nominal voltage sensitivity of the dyes under “one-photon” fluorescence. We find a dependence of voltage sensitivity on excitation wavelength that is consistent with a two-photon resonance, and there is a significant dependence of voltage sensitivity on the structure of the nonchromophore portion of the dyes. PMID:14747351</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22113472','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22113472"><span id="translatedtitle">Nonlinear absorption and <span class="hlt">harmonic</span> <span class="hlt">generation</span> of laser in a gas with anharmonic clusters</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kumar, Manoj; Tripathi, V. K.</p> <p>2013-02-15</p> <p>The nonlinear absorption and <span class="hlt">harmonic</span> <span class="hlt">generation</span> of intense short pulse laser in a gas embedded with anharmonic clusters are investigated theoretically. When the laser induced excursion of cluster electrons becomes comparable to cluster radius, the restoration force on electrons no longer remains linearly proportional to the excursion. As a consequence, the plasmon resonance is broadened, leading to broadband laser absorption. It also leads to second and third <span class="hlt">harmonic</span> <span class="hlt">generations</span>, at much higher level than the one due to ponderomotive nonlinearity. The <span class="hlt">harmonic</span> yield is resonantly enhanced at the plasmon resonance {omega}={omega}{sub pe}/{radical}(3), where {omega} is the frequency of the laser and {omega}{sub pe} is the plasma frequency of cluster electrons.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1176527','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1176527"><span id="translatedtitle">Device and method for <span class="hlt">generating</span> a beam of <span class="hlt">acoustic</span> energy from a borehole, and applications thereof</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Vu, Cung Khac; Sinha, Dipen N.; Pantea, Cristian; Nihei, Kurt T.; Schmitt, Denis P.; Skelt, Chirstopher</p> <p>2013-10-15</p> <p>In some aspects of the invention, a method of <span class="hlt">generating</span> a beam of <span class="hlt">acoustic</span> energy in a borehole is disclosed. The method includes <span class="hlt">generating</span> a first <span class="hlt">acoustic</span> wave at a first frequency; <span class="hlt">generating</span> a second <span class="hlt">acoustic</span> wave at a second frequency different than the first frequency, wherein the first <span class="hlt">acoustic</span> wave and second <span class="hlt">acoustic</span> wave are <span class="hlt">generated</span> by at least one transducer carried by a tool located within the borehole; transmitting the first and the second <span class="hlt">acoustic</span> waves into an <span class="hlt">acoustically</span> non-linear medium, wherein the composition of the non-linear medium produces a collimated beam by a non-linear mixing of the first and second <span class="hlt">acoustic</span> waves, wherein the collimated beam has a frequency based upon a difference between the first frequency range and the second frequency, and wherein the non-linear medium has a velocity of sound between 100 m/s and 800 m/s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17910969','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17910969"><span id="translatedtitle">Modeling photothermal and <span class="hlt">acoustical</span> induced microbubble <span class="hlt">generation</span> and growth.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Krasovitski, Boris; Kislev, Hanoch; Kimmel, Eitan</p> <p>2007-12-01</p> <p>Previous experimental studies showed that powerful heating of nanoparticles by a laser pulse using energy density greater than 100 mJ/cm(2), could induce vaporization and <span class="hlt">generate</span> microbubbles. When ultrasound is introduced at the same time as the laser pulse, much less laser power is required. For therapeutic applications, <span class="hlt">generation</span> of microbubbles on demand at target locations, e.g. cells or bacteria can be used to induce hyperthermia or to facilitate drug delivery. The objective of this work is to develop a method capable of predicting photothermal and <span class="hlt">acoustic</span> parameters in terms of laser power and <span class="hlt">acoustic</span> pressure amplitude that are needed to produce stable microbubbles; and investigate the influence of bubble coalescence on the thresholds when the microbubbles are <span class="hlt">generated</span> around nanoparticles that appear in clusters. We develop and solve here a combined problem of momentum, heat and mass transfer which is associated with <span class="hlt">generation</span> and growth of a microbubble, filled with a mixture of non-vaporized gas (air) and water vapor. The microbubble's size and gas content vary as a result of three mechanisms: gas expansion or compression, evaporation or condensation on the bubble boundary, and diffusion of dissolved air in the surrounding water. The simulations predict that when ultrasound is applied relatively low threshold values of laser and ultrasound power are required to obtain a stable microbubble from a single nanoparticle. Even lower power is required when microbubbles are formed by coalescence around a cluster of 10 nanoparticles. Laser pulse energy density of 21 mJ/cm(2) is predicted for instance together with <span class="hlt">acoustic</span> pressure of 0.1 MPa for a cluster of 10 or 62 mJ/cm(2) for a single nanoparticle. Those values are well within the safety limits, and as such are most appealing for targeted therapeutic purposes. PMID:17910969</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20369995','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20369995"><span id="translatedtitle">Characteristics of second <span class="hlt">harmonic</span> <span class="hlt">generation</span> of Lamb waves in nonlinear elastic plates.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Müller, Martin F; Kim, Jin-Yeon; Qu, Jianmin; Jacobs, Laurence J</p> <p>2010-04-01</p> <p>This paper investigates the characteristics of the second <span class="hlt">harmonic</span> <span class="hlt">generation</span> of Lamb waves in a plate with quadratic nonlinearity. Analytical asymptotic solutions to Lamb waves are first obtained through the use of a perturbation method. Then, based on a careful analysis of these asymptotic solutions, it is shown that the cross-modal <span class="hlt">generation</span> of a symmetric second <span class="hlt">harmonic</span> mode by an antisymmetric primary mode is possible. These solutions also demonstrate that modes showing internal resonance-nonzero power flux to the second <span class="hlt">harmonic</span> mode, plus phase velocity matching-are most useful for measurements. In addition, when using finite wave packets, which is the case in most experimental measurements, group velocity matching is required for a cumulative increase in the second <span class="hlt">harmonic</span> amplitude with propagation distance. Finally, five mode types (which are independent of material properties) that satisfy all three requirements for this cumulative increase in second <span class="hlt">harmonic</span> amplitude-nonzero power flux, plus phase and group velocity matching-are identified. These results are important for the development of an experimental procedure to measure material nonlinearity with Lamb waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19750047423&hterms=signal+saturation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsignal%2Bsaturation','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19750047423&hterms=signal+saturation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsignal%2Bsaturation"><span id="translatedtitle"><span class="hlt">Harmonic</span> <span class="hlt">generation</span> at high field strengths - Frequency shifts and saturation phenomena. [optical mixing technique</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stappaerts, E. A.</p> <p>1975-01-01</p> <p>Optical <span class="hlt">harmonic</span> <span class="hlt">generation</span> and mixing in the gas phase has been proposed as a technique for the <span class="hlt">generation</span> of coherent radiation in the vacuum ultraviolet and soft X-ray spectral region. At the high field strengths required by these processes the interaction between atoms and the electromagnetic field shows intensity-dependent resonances. In this paper we modify <span class="hlt">harmonic</span> <span class="hlt">generation</span> theory to include the effect of these frequency shifts. Closed-form expressions for <span class="hlt">generated</span> dipole moment, absorption probability, and coherence length are presented. The most important consequences of frequency shifts on resonantly enhanced processes are that the pump laser must be tuned away from the small-field resonance frequency, that the conversion efficiency may saturate, and that the dispersion of the medium may change sign. As an example, the <span class="hlt">generation</span> of 198-A radiation by a five-photon mixing process in Li(+) is considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014NJPh...16k3045H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014NJPh...16k3045H"><span id="translatedtitle">Using the third state of matter: high <span class="hlt">harmonic</span> <span class="hlt">generation</span> from liquid targets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heissler, P.; Lugovoy, E.; Hörlein, R.; Waldecker, L.; Wenz, J.; Heigoldt, M.; Khrennikov, K.; Karsch, S.; Krausz, F.; Abel, B.; Tsakiris, G. D.</p> <p>2014-11-01</p> <p>High <span class="hlt">harmonic</span> <span class="hlt">generation</span> on solid and gaseous targets has been proven to be a powerful platform for the <span class="hlt">generation</span> of attosecond pulses. Here we demonstrate a novel technique for the XUV <span class="hlt">generation</span> on a smooth liquid surface target in vacuum, which circumvents the problem of low repetition rate and limited shot numbers associated with solid targets, while it maintains some of its merits. We employed atomically smooth, continuous liquid jets of water, aqueous salt solutions and ethanol that allow uninterrupted high <span class="hlt">harmonic</span> <span class="hlt">generation</span> due to the coherent wake emission mechanism for over 8 h. It has been found that the mechanism of plasma <span class="hlt">generation</span> is very similar to that for smooth solid target surfaces. The vapor pressure around the liquid target in our setup has been found to be very low such that the presence of the gas phase around the liquid jet could be neglected.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21682400','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21682400"><span id="translatedtitle">Extraction of small boat <span class="hlt">harmonic</span> signatures from passive sonar.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ogden, George L; Zurk, Lisa M; Jones, Mark E; Peterson, Mary E</p> <p>2011-06-01</p> <p>This paper investigates the extraction of <span class="hlt">acoustic</span> signatures from small boats using a passive sonar system. Noise radiated from a small boats consists of broadband noise and <span class="hlt">harmonically</span> related tones that correspond to engine and propeller specifications. A signal processing method to automatically extract the <span class="hlt">harmonic</span> structure of noise radiated from small boats is developed. The <span class="hlt">Harmonic</span> Extraction and Analysis Tool (HEAT) estimates the instantaneous fundamental frequency of the <span class="hlt">harmonic</span> tones, refines the fundamental frequency estimate using a Kalman filter, and automatically extracts the amplitudes of the <span class="hlt">harmonic</span> tonals to <span class="hlt">generate</span> a <span class="hlt">harmonic</span> signature for the boat. Results are presented that show the HEAT algorithms ability to extract these signatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.741a2112V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.741a2112V"><span id="translatedtitle">Laser-Induced Periodical Structures Fabrication for Third <span class="hlt">Harmonic</span> <span class="hlt">Generation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Voytova, T. A.; Makarov, S. V.; Tsypkin, A. N.; Milichko, V. A.; Mukhin, I. S.; Yulin, A. V.; Putilin, S. E.; Baranov, M. A.; Krasnok, A. E.; Belov, P. A.</p> <p>2016-08-01</p> <p>We propose a novel strategy for self-adjusted fabrication of large-scale array of resonant silicon nanoparticles (metasurface) on a thin silicon film. The self-adjusting mechanism is based on the effect of resonant nanogratings formation under intense multishot femtosecond irradiation of a thin silicon film. The resulting metasurfaces allow for <span class="hlt">generation</span> of ultraviolet laser pulses at a wavelength of 270 nm with conversion efficiency up to 10-6 and high peak (≈100 kW/sm2) and average power (≈1.5 μW). Such high peak power from ultrathin metasurface makes the <span class="hlt">generated</span> UV pulses applicable in a wide range of applications: precise nanolithography, ultrafast photoexcitation etc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21476632','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21476632"><span id="translatedtitle">Variations in recorded <span class="hlt">acoustic</span> gunshot waveforms <span class="hlt">generated</span> by small firearms.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Beck, Steven D; Nakasone, Hirotaka; Marr, Kenneth W</p> <p>2011-04-01</p> <p>Analysis of recorded <span class="hlt">acoustic</span> gunshot signals to determine firearm waveform characteristics requires an understanding of the impulsive signal events, how the waveforms vary among different sources, and how the waveforms are affected by the environment and the recording system. This paper presents empirical results from waveforms produced by different small firearms and an analysis of their variations under different and controlled conditions. <span class="hlt">Acoustic</span> signals were <span class="hlt">generated</span> using multiple firearm makes and models firing different ammunition types. Simultaneous recordings from the microphones located at different distances from the source and at different azimuth angles (from the line-of-fire) were used to study source characteristics and sound propagation effects. The results indicate that recorded gunshot waveforms generally consist of multiple <span class="hlt">acoustic</span> events, and these are observable depending on the received distance and azimuth angle. The source blast size, microphone distance, and microphone azimuth angle are the primary factors affecting the recorded muzzle blast characteristics. Ground or object reflections and ballistic shockwaves and their reflections can interfere with the muzzle blast waveform and its measurements. This experiment confirmed and quantified the wide range of correlation results between waveforms recorded from different source, microphone distance, and microphone angle configurations. PMID:21476632</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26175000','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26175000"><span id="translatedtitle">Probing Ferroelectric Domain Engineering in BiFeO3 Thin Films by Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Trassin, Morgan; Luca, Gabriele De; Manz, Sebastian; Fiebig, Manfred</p> <p>2015-09-01</p> <p>An optical probe of the ferroelectric domain distribution and manipulation in BiFeO3 thin films is reported using optical second <span class="hlt">harmonic</span> <span class="hlt">generation</span>. A unique relation between the domain distribution and its integral symmetry is established. The ferroelectric signature is even resolved when the film is covered by a top electrode. The effect of voltage-induced ferroelectric switching is imaged.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20646138','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20646138"><span id="translatedtitle">Continuous-variable Einstein-Podolsky-Rosen paradox with traveling-wave second-<span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Olsen, M.K.</p> <p>2004-09-01</p> <p>The Einstein-Podolsky-Rosen paradox and quantum entanglement are at the heart of quantum mechanics. Here we show that single-pass traveling-wave second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> can be used to demonstrate both entanglement and the paradox with continuous variables that are analogous to the position and momentum of the original proposal.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26223624','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26223624"><span id="translatedtitle">Real-time observation of interfering crystal electrons in high-<span class="hlt">harmonic</span> <span class="hlt">generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hohenleutner, M; Langer, F; Schubert, O; Knorr, M; Huttner, U; Koch, S W; Kira, M; Huber, R</p> <p>2015-07-30</p> <p>Acceleration and collision of particles has been a key strategy for exploring the texture of matter. Strong light waves can control and recollide electronic wavepackets, <span class="hlt">generating</span> high-<span class="hlt">harmonic</span> radiation that encodes the structure and dynamics of atoms and molecules and lays the foundations of attosecond science. The recent discovery of high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in bulk solids combines the idea of ultrafast acceleration with complex condensed matter systems, and provides hope for compact solid-state attosecond sources and electronics at optical frequencies. Yet the underlying quantum motion has not so far been observable in real time. Here we study high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in a bulk solid directly in the time domain, and reveal a new kind of strong-field excitation in the crystal. Unlike established atomic sources, our solid emits high-<span class="hlt">harmonic</span> radiation as a sequence of subcycle bursts that coincide temporally with the field crests of one polarity of the driving terahertz waveform. We show that these features are characteristic of a non-perturbative quantum interference process that involves electrons from multiple valence bands. These results identify key mechanisms for future solid-state attosecond sources and next-<span class="hlt">generation</span> light-wave electronics. The new quantum interference process justifies the hope for all-optical band-structure reconstruction and lays the foundation for possible quantum logic operations at optical clock rates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23800228','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23800228"><span id="translatedtitle">Enhanced second <span class="hlt">harmonic</span> <span class="hlt">generation</span> by photonic-plasmonic Fano-type coupling in nanoplasmonic arrays.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Walsh, Gary F; Dal Negro, Luca</p> <p>2013-07-10</p> <p>In this communication, we systematically investigate the effects of Fano-type coupling between long-range photonic resonances and localized surface plasmons on the second <span class="hlt">harmonic</span> <span class="hlt">generation</span> from periodic arrays of Au nanoparticles arranged in monomer and dimer geometries. Specifically, by scanning the wavelength of an ultrafast tunable pump laser over a large range, we measure the second <span class="hlt">harmonic</span> excitation spectra of these arrays and demonstrate their tunability with particle size and separation. Moreover, through a comparison with linear optical transmission spectra, which feature asymmetric Fano-type lineshapes, we demonstrate that the second <span class="hlt">harmonic</span> <span class="hlt">generation</span> is enhanced when coupled photonic-plasmonic resonances of the arrays are excited at the fundamental pump wavelength, thus boosting the intensity of the electromagnetic near-fields. Our experimental results, which are supported by numerical simulations of linear optical transmission and near-field enhancement spectra based on the Finite Difference Time Domain method, demonstrate a direct correlation between the onset of Fano-type coupling and the enhancement of second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in arrays of Au nanoparticles. Our findings enable the engineering of the nonlinear optical response of Fano-type coupled nanoparticle arrays that are relevant to a number of device applications in nonlinear nano-optics and plasmonics, such as on-chip frequency <span class="hlt">generators</span>, modulators, switchers, and sensors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SuMi...76....1Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SuMi...76....1Z"><span id="translatedtitle">Effect of hydrogenic impurity on the third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in a quantum well</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Zhongmin; Guo, Kangxian; Mou, Sen; Xiao, Bo; Liao, Lei</p> <p>2014-12-01</p> <p>The third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) coefficients in a quantum well with hydrogenic impurity are theoretically investigated with the compact-density-matrix approach and iterative method. The wave functions and the energy levels can be obtained by using variational method and numerical method. Numerical results show that the THG coefficients are strongly affected by the hydrogenic impurity.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21454801','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21454801"><span id="translatedtitle">Second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> excited by a rotating Laguerre-Gaussian beam</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Petrov, Dmitri</p> <p>2010-09-15</p> <p>Experimental data demonstrate that unlike linear optical processes, an optical Laguerre-Gaussian beam of frequency {omega}, with topological charge m, rotating with angular frequency {Omega}<<{omega}, may not be considered as a monochromatic beam with the shifted frequency {omega}+m{Omega} (Doppler angular shift) for the second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> nonlinear process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19730034737&hterms=Prisms&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DPrisms','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19730034737&hterms=Prisms&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DPrisms"><span id="translatedtitle">Two-pass-internal second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> using a prism coupler.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gonzalez, D. G.; Nieh, S. T. K.; Steier, W. H.</p> <p>1973-01-01</p> <p>A dispersive quartz prism is used to couple the total second <span class="hlt">harmonic</span> <span class="hlt">generated</span> in both directions by an internal cavity frequency doubler. The study shows that the dispersion of air and mirror reflection phase shifts can be compensated for by a slight nonphase match condition in the doubler.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26223624','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26223624"><span id="translatedtitle">Real-time observation of interfering crystal electrons in high-<span class="hlt">harmonic</span> <span class="hlt">generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hohenleutner, M; Langer, F; Schubert, O; Knorr, M; Huttner, U; Koch, S W; Kira, M; Huber, R</p> <p>2015-07-30</p> <p>Acceleration and collision of particles has been a key strategy for exploring the texture of matter. Strong light waves can control and recollide electronic wavepackets, <span class="hlt">generating</span> high-<span class="hlt">harmonic</span> radiation that encodes the structure and dynamics of atoms and molecules and lays the foundations of attosecond science. The recent discovery of high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in bulk solids combines the idea of ultrafast acceleration with complex condensed matter systems, and provides hope for compact solid-state attosecond sources and electronics at optical frequencies. Yet the underlying quantum motion has not so far been observable in real time. Here we study high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in a bulk solid directly in the time domain, and reveal a new kind of strong-field excitation in the crystal. Unlike established atomic sources, our solid emits high-<span class="hlt">harmonic</span> radiation as a sequence of subcycle bursts that coincide temporally with the field crests of one polarity of the driving terahertz waveform. We show that these features are characteristic of a non-perturbative quantum interference process that involves electrons from multiple valence bands. These results identify key mechanisms for future solid-state attosecond sources and next-<span class="hlt">generation</span> light-wave electronics. The new quantum interference process justifies the hope for all-optical band-structure reconstruction and lays the foundation for possible quantum logic operations at optical clock rates. PMID:26223624</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21140517','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21140517"><span id="translatedtitle">Rydberg-Rydberg interaction in the second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> from rubidium atoms</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Melo, Natalia R. de; Vianna, Sandra S.</p> <p>2008-02-15</p> <p>We report on the observation of long range interaction in the second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> from rubidium Rydberg atoms. The asymmetric spectral broadening of the resonant lines provides evidence of the van der Waals interaction between pairs of Rydberg atoms. This effect is investigated when the two-photon transition is resonant with nd levels for n{approx_equal}13.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/485931','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/485931"><span id="translatedtitle">Homoclinic orbits and chaos in a second-<span class="hlt">harmonic</span> <span class="hlt">generating</span> optical cavity</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Holm, D.; Kovacic, G., Timofeyev, I.</p> <p>1997-04-01</p> <p>We present two large families of Silnikov-type homoclinic orbits in a two mode-model that describes second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in a passive optical cavity. These families of homoclinic orbits give rise to chaotic dynamics in the model. 4 refs., 1 fig.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22043674','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22043674"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> of spectrally broadened femtosecond ytterbium laser radiation in a gas-filled capillary</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Didenko, N V; Konyashchenko, Aleksandr V; Kostryukov, P V; Losev, Leonid L; Tenyakov, S Yu</p> <p>2011-09-30</p> <p>A 300-fs radiation pulse of an ytterbium laser with a wavelength of 1030 nm and energy of 150 {mu}J were converted to a 15-fs pulse with a wavelength of 515 nm by broadening the emission spectrum in a capillary filled with xenon and by <span class="hlt">generating</span> the second <span class="hlt">harmonic</span> in a KDP crystal. The energy efficiency of the conversion was 30 %.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990ApPhL..57..221Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990ApPhL..57..221Z"><span id="translatedtitle">Second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> of a new chalcone-type crystal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, G. J.; Kinoshita, T.; Sasaki, K.; Goto, Y.; Nakayama, M.</p> <p>1990-07-01</p> <p>A new type of chalcone crystal was prepared. Anisotropic indices with wavelength dispersion were measured by the Brewster angle method. The two largest second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) tensor components were determined by the wedge method and compared with d11 of 2-methyl-4-nitroaniline. Calculated collinear and noncollinear phase-matched SHG patterns reasonably fit the observed photographs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19880028096&hterms=transLATION&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DtransLATION','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19880028096&hterms=transLATION&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DtransLATION"><span id="translatedtitle">Optical <span class="hlt">generation</span> of a circular <span class="hlt">harmonic</span> filter for rotation and translation invariant optical pattern recognition</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cheng, Yeou-Yen</p> <p>1987-01-01</p> <p>A new method to <span class="hlt">generate</span> a circular <span class="hlt">harmonic</span> filter with both rotation and translation invariance is described, which is based on a phase-shifted double-exposure (PSDE) technique. An expression for the peak correlation intensity at the origin for the correlation plane as a function of target orientation for the PSDE filter is derived. Experimental results confirming the theoretical predictions are provided.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JAP...111i3112O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JAP...111i3112O"><span id="translatedtitle">First-principle description for the high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in a diamond by intense short laser pulse</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Otobe, T.</p> <p>2012-05-01</p> <p>We present a first-principles description for the electron excitation and the high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) in a diamond by intense laser pulse irradiation and their laser parameter dependence. Above band gap <span class="hlt">harmonics</span> are <span class="hlt">generated</span> after the peak of the incident laser pulse and have duration much shorter than the laser pulse. The intensity of individual <span class="hlt">harmonic</span> peaks increases as laser intensity increases nonlinearly, and we find the blue shift of the HHG spectrum when the optical breakdown occurs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001ASAJ..115Q2552C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001ASAJ..115Q2552C"><span id="translatedtitle">Alternative <span class="hlt">acoustic</span> environments for the <span class="hlt">generation</span> of reverberation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Case, Alexander U.</p> <p>2001-05-01</p> <p>The musicians and engineers who create popular recorded music view reverberation as a signal processing effect to be added to any and all elements of a multitrack production. Devices such as digital reverbs, spring reverbs, and plate reverbs are tools of the recording trade, synthesizing reverblike sounds for performance through loudspeakers. <span class="hlt">Acoustic</span> reverberation makes its way into recorded music through the use of a reverb chamber. A small room is used to <span class="hlt">generate</span> reverb. With cubic volume well below that of a performance hall, it works the ``other side'' of the Sabine equation, being built of highly sound reflective materials. A purpose-built room for the <span class="hlt">generation</span> of reverb is a luxury not many studios can afford. Clever use of stairwells, bathrooms, and basements is easier on the recording studios balance sheet. This work evaluates the repurposing of these alternative spaces for the <span class="hlt">generation</span> of reverb in popular recorded music.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27300994','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27300994"><span id="translatedtitle">Model of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> from laser interaction with a plasma grating.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, S J; Zhuo, H B; Zou, D B; Gan, L F; Zhou, H Y; Li, X Z; Yu, M Y; Yu, W</p> <p>2016-05-01</p> <p><span class="hlt">Harmonic</span> <span class="hlt">generation</span> from linearly polarized high-intensity short-pulse laser normally impacting a solid plasma grating is investigated using analytical modeling and particle-in-cell simulation. It is found that when the radiation excited by the relativistic electron quiver motion in the laser fields suitably matches a <span class="hlt">harmonic</span> of the grating periodicity, it will be significantly enhanced and peak with narrow angular spread in specific directions. The corresponding theory shows that the phenomenon can be attributed to an interference effect of the periodic grating on the excitation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22412534','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22412534"><span id="translatedtitle">Ultrashort pulse chirp measurement via transverse second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in strontium barium niobate crystal</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Trull, J.; Wang, B.; Parra, A.; Vilaseca, R.; Cojocaru, C.; Sola, I.; Sheng, Y.</p> <p>2015-06-01</p> <p>Pulse compression in dispersive strontium barium niobate crystal with a random size and distribution of the anti-parallel orientated nonlinear domains is observed via transverse second <span class="hlt">harmonic</span> <span class="hlt">generation</span>. The dependence of the transverse width of the second <span class="hlt">harmonic</span> trace along the propagation direction allows for the determination of the initial chirp and duration of pulses in the femtosecond regime. This technique permits a real-time analysis of the pulse evolution and facilitates fast in-situ correction of pulse chirp acquired in the propagation through an optical system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvE..93e3206Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvE..93e3206Z"><span id="translatedtitle">Model of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> from laser interaction with a plasma grating</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, S. J.; Zhuo, H. B.; Zou, D. B.; Gan, L. F.; Zhou, H. Y.; Li, X. Z.; Yu, M. Y.; Yu, W.</p> <p>2016-05-01</p> <p><span class="hlt">Harmonic</span> <span class="hlt">generation</span> from linearly polarized high-intensity short-pulse laser normally impacting a solid plasma grating is investigated using analytical modeling and particle-in-cell simulation. It is found that when the radiation excited by the relativistic electron quiver motion in the laser fields suitably matches a <span class="hlt">harmonic</span> of the grating periodicity, it will be significantly enhanced and peak with narrow angular spread in specific directions. The corresponding theory shows that the phenomenon can be attributed to an interference effect of the periodic grating on the excitation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/147760','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/147760"><span id="translatedtitle">Anomalous-dispersion phase-matched second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in a polymer waveguide</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kowalczyk, T.C.; Singer, K.D.; Cahill, P.A.</p> <p>1995-11-15</p> <p>We demonstrate phase-matched second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in a poled polymer waveguide, using anomalous-dispersion phase matching. Phase matching was achieved between lowest-order fundamental and <span class="hlt">harmonic</span> modes, TM{sub 0}{sup {omega}} to TM{sub 0}{sup 2{omega}}, at a fundamental wavelength of 815 nm over a propagation length of 32 {mu}m. The maximum conversion efficiency was {eta}{sub exp}=39%/Wcm{sup 2}, in good agreement with theory. {copyright} {ital 1995} {ital Optical} {ital Society} {ital of} {ital America}.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27300994','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27300994"><span id="translatedtitle">Model of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> from laser interaction with a plasma grating.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, S J; Zhuo, H B; Zou, D B; Gan, L F; Zhou, H Y; Li, X Z; Yu, M Y; Yu, W</p> <p>2016-05-01</p> <p><span class="hlt">Harmonic</span> <span class="hlt">generation</span> from linearly polarized high-intensity short-pulse laser normally impacting a solid plasma grating is investigated using analytical modeling and particle-in-cell simulation. It is found that when the radiation excited by the relativistic electron quiver motion in the laser fields suitably matches a <span class="hlt">harmonic</span> of the grating periodicity, it will be significantly enhanced and peak with narrow angular spread in specific directions. The corresponding theory shows that the phenomenon can be attributed to an interference effect of the periodic grating on the excitation. PMID:27300994</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25911148','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25911148"><span id="translatedtitle">Analysis of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> by primary ultrasonic guided wave propagation in a piezoelectric plate.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Deng, Mingxi; Xiang, Yanxun</p> <p>2015-08-01</p> <p>The effect of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) by primary ultrasonic guided wave propagation is analyzed, where the nonlinear elastic, piezoelectric, and dielectric properties of the piezoelectric plate material are considered simultaneously. The formal solution of the corresponding second-<span class="hlt">harmonic</span> displacement field is presented. Theoretical and numerical investigations clearly show that the SHG effect of primary guided wave propagation is highly sensitive to the electrical boundary conditions of the piezoelectric plate. The results obtained may provide a means through which the SHG efficiency of ultrasonic guided wave propagation can effectively be regulated by changing the electrical boundary conditions of the piezoelectric plate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22051338','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22051338"><span id="translatedtitle">Interplay of mulitphoton and tunneling ionization in short-wavelength-driven high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gkortsas, Vasileios-Marios; Bhardwaj, Siddharth; Lai, Chien-Jen; Hong, Kyung-Han; Falcao-Filho, Edilson L.; Kaertner, Franz X.</p> <p>2011-07-15</p> <p>High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> efficiency is theoretically modeled and compared with experiments using 400 and 800 nm driver pulses. It is shown that, for a short drive wavelength and a Keldysh parameter larger than 1, the Ammosov-Delone-Krainov (ADK) ionization model does not give a good agreement between theory and experiment. Since the ADK ionization model only accounts for tunnel ionization, it underestimates the yield of low-order <span class="hlt">harmonics</span> from the wings of the driver pulse. In contrast, the Yudin-Ivanov ionization model [Phys. Rev. A 64, 013409 (2001)], which accounts for both tunnel and multiphoton ionization, gives much better agreement with the experimental results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25911148','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25911148"><span id="translatedtitle">Analysis of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> by primary ultrasonic guided wave propagation in a piezoelectric plate.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Deng, Mingxi; Xiang, Yanxun</p> <p>2015-08-01</p> <p>The effect of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) by primary ultrasonic guided wave propagation is analyzed, where the nonlinear elastic, piezoelectric, and dielectric properties of the piezoelectric plate material are considered simultaneously. The formal solution of the corresponding second-<span class="hlt">harmonic</span> displacement field is presented. Theoretical and numerical investigations clearly show that the SHG effect of primary guided wave propagation is highly sensitive to the electrical boundary conditions of the piezoelectric plate. The results obtained may provide a means through which the SHG efficiency of ultrasonic guided wave propagation can effectively be regulated by changing the electrical boundary conditions of the piezoelectric plate. PMID:25911148</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18773029','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18773029"><span id="translatedtitle">Planar second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> with noncollinear pumps in disordered media.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Roppo, Vito; Dumay, David; Trull, Jose; Cojocaru, Crina; Saltiel, Solomon M; Staliunas, Kestutis; Vilaseca, Ramon; Neshev, Dragomir N; Krolikowski, Wieslaw; Kivshar, Yuri S</p> <p>2008-09-01</p> <p>We study experimentally the process of the second <span class="hlt">harmonic</span> <span class="hlt">generation</span> by two noncollinear beams in quadratic nonlinear crystals with a disordered structure of ferroelectric domains. We show that the second-<span class="hlt">harmonic</span> radiation is emitted in the form of two cones as well as in a plane representing the cross-correlation of the two fundamental pulses. We demonstrate the implementation of this parametric process for characterisation of femtosecond pulses, enabling the estimation of pulse width, chirp, and front tilt. This is achieved through monitoring the evolution of the autocorrelation trace inside the nonlinear crystal.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21448153','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21448153"><span id="translatedtitle">Whispering gallery microresonators for second <span class="hlt">harmonic</span> light <span class="hlt">generation</span> from a low number of small molecules.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dominguez-Juarez, J L; Kozyreff, G; Martorell, Jordi</p> <p>2011-01-01</p> <p>Unmarked sensitive detection of molecules is needed in environmental pollution monitoring, disease diagnosis, security screening systems and in many other situations in which a substance must be identified. When molecules are attached or adsorbed onto an interface, detecting their presence is possible using second <span class="hlt">harmonic</span> light <span class="hlt">generation</span>, because at interfaces the inversion symmetry is broken. However, such light <span class="hlt">generation</span> usually requires either dense matter or a large number of molecules combined with high-power laser sources. Here we show that using high-Q spherical microresonators and low average power, between 50 and 100 small non-fluorescent molecules deposited on the outer surface of the microresonator can <span class="hlt">generate</span> a detectable change in the second <span class="hlt">harmonic</span> light. This <span class="hlt">generation</span> requires phase matching in the whispering gallery modes, which we achieved using a new procedure to periodically pattern, with nanometric precision, a molecular surface monolayer. PMID:21448153</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27610855','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27610855"><span id="translatedtitle">Probe of Multielectron Dynamics in Xenon by Caustics in High-Order <span class="hlt">Harmonic</span> <span class="hlt">Generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Faccialà, D; Pabst, S; Bruner, B D; Ciriolo, A G; De Silvestri, S; Devetta, M; Negro, M; Soifer, H; Stagira, S; Dudovich, N; Vozzi, C</p> <p>2016-08-26</p> <p>We investigated the giant resonance in xenon by high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> spectroscopy driven by a two-color field. The addition of a nonperturbative second <span class="hlt">harmonic</span> component parallel to the driving field breaks the symmetry between neighboring subcycles resulting in the appearance of spectral caustics at two distinct cutoff energies. By controlling the phase delay between the two color components it is possible to tailor the <span class="hlt">harmonic</span> emission in order to amplify and isolate the spectral feature of interest. In this Letter we demonstrate how this control scheme can be used to investigate the role of electron correlations that give birth to the giant resonance in xenon. The collective excitations of the giant dipole resonance in xenon combined with the spectral manipulation associated with the two-color driving field allow us to see features that are normally not accessible and to obtain a good agreement between the experimental results and the theoretical predictions. PMID:27610855</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14611405','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14611405"><span id="translatedtitle">High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> yielding tunable extreme-ultraviolet radiation of high spectral purity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Brandi, F; Neshev, D; Ubachs, W</p> <p>2003-10-17</p> <p>Production of extreme-ultraviolet radiation by high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> is demonstrated to yield unprecedented spectral purity of lambda/Delta lambda=2.5 x 10(5) at wavelengths covering the entire range 40-100 nm. Tunability and sub-cm(-1) bandwidth of the <span class="hlt">harmonics</span> are demonstrated in recordings of the He (1s4p) and Ar (3p(5)3d') resonance lines at 52.2 and 86.6 nm. Frequency shift of the <span class="hlt">harmonics</span> due to chirp-induced phenomena are investigated and found to be small, resulting in a frequency accuracy of about 5 x 10(-7) in the domain of extreme-ultraviolet radiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23187480','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23187480"><span id="translatedtitle">Enhancement of high <span class="hlt">harmonic</span> <span class="hlt">generation</span> by confining electron motion in plasmonic nanostrutures.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ciappina, M F; Aćimović, Srdjan S; Shaaran, T; Biegert, J; Quidant, R; Lewenstein, M</p> <p>2012-11-19</p> <p>We study high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) resulting from the illumination of plasmonic nanostructures with a short laser pulse of long wavelength. We demonstrate that both the confinement of the electron motion and the inhomogeneous character of the laser electric field play an important role in the HHG process and lead to a significant increase of the <span class="hlt">harmonic</span> cutoff. In particular, in bow-tie nanostructures with small gaps, electron trajectories with large excursion amplitudes experience significant confinement and their contribution is essentially suppressed. In order to understand and characterize this feature, we combine the numerical solution of the time-dependent Schrödinger equation (TDSE) with the electric fields obtained from 3D finite element simulations. We employ time-frequency analysis to extract more detailed information from the TDSE results and classical tools to explain the extended <span class="hlt">harmonic</span> spectra. The spatial inhomogeneity of the laser electric field modifies substantially the electron trajectories and contributes also to cutoff increase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26894708','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26894708"><span id="translatedtitle">Two-Dimensional Frequency Resolved Optomolecular Gating of High-Order <span class="hlt">Harmonic</span> <span class="hlt">Generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ferré, A; Soifer, H; Pedatzur, O; Bourassin-Bouchet, C; Bruner, B D; Canonge, R; Catoire, F; Descamps, D; Fabre, B; Mével, E; Petit, S; Dudovich, N; Mairesse, Y</p> <p>2016-02-01</p> <p>Probing electronic wave functions of polyatomic molecules is one of the major challenges in high-<span class="hlt">harmonic</span> spectroscopy. The extremely nonlinear nature of the laser-molecule interaction couples the multiple degrees of freedom of the probed system. We combine two-dimensional control of the electron trajectories and vibrational control of the molecules to disentangle the two main steps in high-<span class="hlt">harmonic</span> <span class="hlt">generation</span>-ionization and recombination. We introduce a new measurement scheme, frequency-resolved optomolecular gating, which resolves the temporal amplitude and phase of the <span class="hlt">harmonic</span> emission from excited molecules. Focusing on the study of vibrational motion in N_{2}O_{4}, we show that such advanced schemes provide a unique insight into the structural and dynamical properties of the underlying mechanism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25910125','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25910125"><span id="translatedtitle">Carrier-wave Rabi-flopping signatures in high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> for alkali atoms.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ciappina, M F; Pérez-Hernández, J A; Landsman, A S; Zimmermann, T; Lewenstein, M; Roso, L; Krausz, F</p> <p>2015-04-10</p> <p>We present a theoretical investigation of carrier-wave Rabi flopping in real atoms by employing numerical simulations of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) in alkali species. Given the short HHG cutoff, related to the low saturation intensity, we concentrate on the features of the third <span class="hlt">harmonic</span> of sodium (Na) and potassium (K) atoms. For pulse areas of 2π and Na atoms, a characteristic unique peak appears, which, after analyzing the ground state population, we correlate with the conventional Rabi flopping. On the other hand, for larger pulse areas, carrier-wave Rabi flopping occurs, and is associated with a more complex structure in the third <span class="hlt">harmonic</span>. These characteristics observed in K atoms indicate the breakdown of the area theorem, as was already demonstrated under similar circumstances in narrow band gap semiconductors. PMID:25910125</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27610855','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27610855"><span id="translatedtitle">Probe of Multielectron Dynamics in Xenon by Caustics in High-Order <span class="hlt">Harmonic</span> <span class="hlt">Generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Faccialà, D; Pabst, S; Bruner, B D; Ciriolo, A G; De Silvestri, S; Devetta, M; Negro, M; Soifer, H; Stagira, S; Dudovich, N; Vozzi, C</p> <p>2016-08-26</p> <p>We investigated the giant resonance in xenon by high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> spectroscopy driven by a two-color field. The addition of a nonperturbative second <span class="hlt">harmonic</span> component parallel to the driving field breaks the symmetry between neighboring subcycles resulting in the appearance of spectral caustics at two distinct cutoff energies. By controlling the phase delay between the two color components it is possible to tailor the <span class="hlt">harmonic</span> emission in order to amplify and isolate the spectral feature of interest. In this Letter we demonstrate how this control scheme can be used to investigate the role of electron correlations that give birth to the giant resonance in xenon. The collective excitations of the giant dipole resonance in xenon combined with the spectral manipulation associated with the two-color driving field allow us to see features that are normally not accessible and to obtain a good agreement between the experimental results and the theoretical predictions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26894708','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26894708"><span id="translatedtitle">Two-Dimensional Frequency Resolved Optomolecular Gating of High-Order <span class="hlt">Harmonic</span> <span class="hlt">Generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ferré, A; Soifer, H; Pedatzur, O; Bourassin-Bouchet, C; Bruner, B D; Canonge, R; Catoire, F; Descamps, D; Fabre, B; Mével, E; Petit, S; Dudovich, N; Mairesse, Y</p> <p>2016-02-01</p> <p>Probing electronic wave functions of polyatomic molecules is one of the major challenges in high-<span class="hlt">harmonic</span> spectroscopy. The extremely nonlinear nature of the laser-molecule interaction couples the multiple degrees of freedom of the probed system. We combine two-dimensional control of the electron trajectories and vibrational control of the molecules to disentangle the two main steps in high-<span class="hlt">harmonic</span> <span class="hlt">generation</span>-ionization and recombination. We introduce a new measurement scheme, frequency-resolved optomolecular gating, which resolves the temporal amplitude and phase of the <span class="hlt">harmonic</span> emission from excited molecules. Focusing on the study of vibrational motion in N_{2}O_{4}, we show that such advanced schemes provide a unique insight into the structural and dynamical properties of the underlying mechanism. PMID:26894708</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvA..94c3419O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvA..94c3419O"><span id="translatedtitle">High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> in polyatomic molecules induced by a bicircular laser field</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Odžak, S.; Hasović, E.; Milošević, D. B.</p> <p>2016-09-01</p> <p>High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> by a bicircular field, which consists of two coplanar counter-rotating circularly polarized fields of frequency r ω and s ω (r and s are integers), is investigated for a polyatomic molecule. This field possesses dynamical symmetry, which can be adjusted to the symmetry of the molecular Hamiltonian and used to investigate the molecular symmetry. For polyatomic molecules having the Cr +s symmetry, only the <span class="hlt">harmonics</span> n =q (r +s )±r ,q =1 ,2 ,..., are emitted having the ellipticity ɛn=±1 . We illustrate this using the example of the planar molecules BH3 and BF3, which obey the C3 symmetry. We show that for the BF3 molecule, similarly to atoms with a p ground state, there is a strong asymmetry in the emission of high <span class="hlt">harmonics</span> with opposite helicities. This asymmetry depends on the molecular orientation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25910125','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25910125"><span id="translatedtitle">Carrier-wave Rabi-flopping signatures in high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> for alkali atoms.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ciappina, M F; Pérez-Hernández, J A; Landsman, A S; Zimmermann, T; Lewenstein, M; Roso, L; Krausz, F</p> <p>2015-04-10</p> <p>We present a theoretical investigation of carrier-wave Rabi flopping in real atoms by employing numerical simulations of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) in alkali species. Given the short HHG cutoff, related to the low saturation intensity, we concentrate on the features of the third <span class="hlt">harmonic</span> of sodium (Na) and potassium (K) atoms. For pulse areas of 2π and Na atoms, a characteristic unique peak appears, which, after analyzing the ground state population, we correlate with the conventional Rabi flopping. On the other hand, for larger pulse areas, carrier-wave Rabi flopping occurs, and is associated with a more complex structure in the third <span class="hlt">harmonic</span>. These characteristics observed in K atoms indicate the breakdown of the area theorem, as was already demonstrated under similar circumstances in narrow band gap semiconductors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvL.117i3902F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvL.117i3902F"><span id="translatedtitle">Probe of Multielectron Dynamics in Xenon by Caustics in High-Order <span class="hlt">Harmonic</span> <span class="hlt">Generation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Faccialà, D.; Pabst, S.; Bruner, B. D.; Ciriolo, A. G.; De Silvestri, S.; Devetta, M.; Negro, M.; Soifer, H.; Stagira, S.; Dudovich, N.; Vozzi, C.</p> <p>2016-08-01</p> <p>We investigated the giant resonance in xenon by high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> spectroscopy driven by a two-color field. The addition of a nonperturbative second <span class="hlt">harmonic</span> component parallel to the driving field breaks the symmetry between neighboring subcycles resulting in the appearance of spectral caustics at two distinct cutoff energies. By controlling the phase delay between the two color components it is possible to tailor the <span class="hlt">harmonic</span> emission in order to amplify and isolate the spectral feature of interest. In this Letter we demonstrate how this control scheme can be used to investigate the role of electron correlations that give birth to the giant resonance in xenon. The collective excitations of the giant dipole resonance in xenon combined with the spectral manipulation associated with the two-color driving field allow us to see features that are normally not accessible and to obtain a good agreement between the experimental results and the theoretical predictions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005ApPhB..80..203K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005ApPhB..80..203K"><span id="translatedtitle"><span class="hlt">Harmonic</span> <span class="hlt">generation</span> in the discrete spectral region of xenon using broadband femtosecond laser pulses</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kutzner, J.; Tsilimis, G.; Zacharias, H.</p> <p>2005-02-01</p> <p>The conversion of 34-fs Ti:sapphire laser pulses into the wavelength region 105 210 nm has been studied in xenon for laser intensities up to 5×1013 W/cm2. A strongly structured, pressure-dependent emission spectrum is observed. Radiation is detected in regions expected for the 5th and 7th <span class="hlt">harmonics</span> but also in regions in between. In the resonance region (λ<147 nm), self-phase-modulation processes in the conversion medium together with phase-matched, efficient <span class="hlt">harmonic</span> <span class="hlt">generation</span> in negative-dispersive spectral regions explain the observations. Broadband emission is detected in the resonance-free, positive-dispersive spectral region 155 210 nm. Emission from the xenon dimer is superimposed on a ‘direct’ 5th-<span class="hlt">harmonic</span> signal.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/889324','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/889324"><span id="translatedtitle">Analytic model of bunched beams for <span class="hlt">harmonic</span> <span class="hlt">generation</span> in thelow-gain free electron laser regime</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Penn, G.; Reinsch, M.; Wurtele, J.S.</p> <p>2006-02-20</p> <p>One scheme for <span class="hlt">harmonic</span> <span class="hlt">generation</span> employs free electron lasers (FELs) with two undulators: the first uses a seed laser to modulate the energy of the electron beam; following a dispersive element which acts to bunch the beam, the second undulator radiates at a higher <span class="hlt">harmonic</span>. These processes are currently evaluated using extensive calculations or simulation codes which can be slow to evaluate and difficult to set up. We describe a simple algorithm to predict the output of a <span class="hlt">harmonic</span> <span class="hlt">generation</span> beamline in the low-gain FEL regime, based on trial functions for the output radiation. Full three-dimensional effects are included. This method has been implemented as a Mathematica package, named CAMPANILE, which runs rapidly and can be generalized to include effects such as asymmetric beams and misalignments. This method is compared with simulation results using the FEL code GENESIS, both for single stages of <span class="hlt">harmonic</span> <span class="hlt">generation</span> and for the LUX project, a design concept for an ultrafast X-ray facility, where multiple stages upshift the input laser frequency by factors of up to 200.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/238685','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/238685"><span id="translatedtitle">X-ray FEL based on <span class="hlt">harmonics</span> <span class="hlt">generation</span> and electron beam outcoupling</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Litvinenko, V.N.; Burnham, B.</p> <p>1995-12-31</p> <p>Electron beam outcoupling was suggested by N. A. Vinokurov as a method of optics independent outcoupling for high power FELs. The bunching of the electron beam is provided in a master oscillator. The prebunched electron beam then radiates coherently into an additional wiggler called the radiator. The electron beam is turned by an achromatic bend into this wiggler and its radiation propagates with a small angle with respect to the OK-4 optical axis. Thus, the radiation will pass around the mirror of the master oscillator optical cavity and can then be utilized. This scheme is perfectly suited for <span class="hlt">harmonic</span> <span class="hlt">generation</span> if the radiator wiggler is tuned on one of the master oscillator wavelength <span class="hlt">harmonics</span>. This system is reminiscent of a klystron operating on a <span class="hlt">harmonic</span> of the reference frequency. In this paper we present the theory of this device, its spectral and spatial characteristics of radiation, the optimization of the master oscillator, the achromatic bend and bunching for <span class="hlt">harmonic</span> <span class="hlt">generation</span>, and influence of beam parameters (energy spread, emittance, etc.) on <span class="hlt">generated</span> power. Examples of possible storage ring and linac driven systems are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/201792','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/201792"><span id="translatedtitle">Two-dimensional phase transformation probed by second <span class="hlt">harmonic</span> <span class="hlt">generation</span>: Oscillatory transformation of the K/Al(111) system</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ying, Z.C.; Plummer, E.W. |</p> <p>1995-12-31</p> <p>The technique of optical second <span class="hlt">harmonic</span> <span class="hlt">generation</span> is used to study phase transformations at two-dimensional surfaces and interfaces. Examples are given to illustrate that changes in surface symmetry, adsorption configuration, and electronic structure can be detected by this nonlinear optical technique. An oscillatory phase transformation of potassium adsorbed atoms on Al(111) probed by second <span class="hlt">harmonic</span> <span class="hlt">generation</span> is analyzed in detail.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950065179&hterms=laser+diode&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dlaser%2Bdiode','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950065179&hterms=laser+diode&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dlaser%2Bdiode"><span id="translatedtitle"><span class="hlt">Generation</span> Of 369.4-Nanometers Second <span class="hlt">Harmonic</span> From A Diode Laser</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Williams, Angelyn P.; Maleki, Lutfollah</p> <p>1995-01-01</p> <p>Experimental laser system features polarization feedback scheme maintaining frequency lock. <span class="hlt">Generates</span> light at wavelength of 369.4 nanometers by second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> from 738.8-nanometers laser diode. System prototype of source of 369.4-nanometers radiation used to optically pump 2S1/2 ' 2P1/2 transition in 171Yb+ ions in lightweight, low-power trapped-ion frequency-standard apparatus.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19044703','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19044703"><span id="translatedtitle">Extreme-ultraviolet polarimeter utilizing laser-<span class="hlt">generated</span> high-order <span class="hlt">harmonics</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Brimhall, Nicole; Turner, Matthew; Herrick, Nicholas; Allred, David D; Turley, R Steven; Ware, Michael; Peatross, Justin</p> <p>2008-10-01</p> <p>We describe an extreme-ultraviolet (EUV) polarimeter that employs laser-<span class="hlt">generated</span> high-order <span class="hlt">harmonics</span> as the light source. The polarimeter is designed to characterize materials and thin films for use with EUV light. Laser high <span class="hlt">harmonics</span> are highly directional with easily rotatable linear polarization, not typically available with other EUV sources. The <span class="hlt">harmonics</span> have good wavelength coverage, potentially spanning the entire EUV from a few to a hundred nanometers. Our instrument is configured to measure reflectances from 14 to 30 nm and has approximately 180 spectral resolution (lambda/Delta lambda). The reflection from a sample surface can be measured over a continuous range of incident angles (5 degrees-75 degrees). A secondary 14 cm gas cell attenuates the <span class="hlt">harmonics</span> in a controlled way to keep signals within the linear dynamic range of the detector, comprised of a microchannel plate coupled to a phosphorous screen and charge coupled device camera. The <span class="hlt">harmonics</span> are produced using approximately 10 mJ, approximately 35 fs, and approximately 800 nm laser pulses with a repetition rate of 10 Hz. Per-shot energy monitoring of the laser discriminates against fluctuations. The polarimeter reflectance data agree well with data obtained at the Advanced Light Source Synchrotron (Beamline 6.3.2).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006SPIE.6317E..0YB','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006SPIE.6317E..0YB"><span id="translatedtitle">Construction of an extreme ultraviolet polarimeter based on high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brimhall, N.; Painter, J. C.; Turner, M.; Voronov, S. V.; Turley, R. S.; Ware, M.; Peatross, J.</p> <p>2006-08-01</p> <p>We report on the development of a polarimeter for characterizing reflective surfaces throughout the extreme ultraviolet (EUV). The instrument relies on laser high-order <span class="hlt">harmonics</span> <span class="hlt">generated</span> in helium, neon, or argon gas. The 800 nm laser <span class="hlt">generates</span> a discrete comb of odd <span class="hlt">harmonics</span> up to order 100 (wavelengths from 8-62 nm). The flux of EUV light is a couple orders of magnitude less than a synchrotron source but 30,000 times greater than a plasma source currently in operation at BYU. The polarimeter determines the reflectance from surfaces as a function of incident angle, linear light polarization orientation, and wavelength. The instrument uses a wave plate in the laser beam to control the orientation of the <span class="hlt">harmonic</span> polarization (linear, same as laser). After reflecting from the sample, the <span class="hlt">harmonic</span> beams are dispersed by a grating and focused onto a micro-channel plate coupled to a phosphor screen. We have demonstrated the feasibility of this project with a simple prototype instrument, which measured the reflectance of samples from 30 nm to 62 nm. The prototype demonstrated that sensitivity is sufficient for measuring reflectances as low as 0.5% for both s- and p-polarized light. The full instrument employs extensive scanning mobility as opposed to the fixed angle and fixed wavelength range of our earlier prototype. An advantage of employing <span class="hlt">harmonics</span> as a source for EUV polarimetry is that a wide range of wavelengths can be measured simultaneously. This project represents an authentic 'work-horse' application for high-order <span class="hlt">harmonics</span>, as opposed to merely demonstrating proof of concept.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22399149','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22399149"><span id="translatedtitle">Low- and high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> in the extended plasmas produced by laser ablation of zinc and manganese targets</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ganeev, R. A.; Baba, M.; Suzuki, M.; Yoneya, S.; Kuroda, H.</p> <p>2014-12-28</p> <p>The systematic studies of the <span class="hlt">harmonic</span> <span class="hlt">generation</span> of ultrashort laser pulses in the 5-mm-long Zn and Mn plasmas (i.e., application of nanosecond, picosecond, and femtosecond pulses for ablation, comparison of <span class="hlt">harmonic</span> <span class="hlt">generation</span> from atomic, ionic, and cluster-contained species of plasma, variation of plasma length, two-color pump of plasmas, etc.) are presented. The conversion efficiency of the 11th–19th <span class="hlt">harmonics</span> <span class="hlt">generated</span> in the Zn plasma was ∼5 × 10{sup −5}. The role of the ionic resonances of Zn near the 9th and 10th <span class="hlt">harmonics</span> on the enhancement of <span class="hlt">harmonics</span> is discussed. The enhancement of <span class="hlt">harmonics</span> was also analyzed using the two-color pump of extended plasmas, which showed similar intensities of the odd and even <span class="hlt">harmonics</span> along the whole range of <span class="hlt">generation</span>. The <span class="hlt">harmonics</span> up to the 107th order were demonstrated in the case of manganese plasma. The comparison of <span class="hlt">harmonic</span> <span class="hlt">generation</span> in the 5-mm-long and commonly used short (≤0.5 mm) plasma plumes showed the advanced properties of extended media.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22492652','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22492652"><span id="translatedtitle">Second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in shear wave beams with different polarizations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Spratt, Kyle S. Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hamilton, Mark F.</p> <p>2015-10-28</p> <p>A coupled pair of nonlinear parabolic equations was derived by Zabolotskaya [1] that model the transverse components of the particle motion in a collimated shear wave beam propagating in an isotropic elastic solid. Like the KZK equation, the parabolic equation for shear wave beams accounts consistently for the leading order effects of diffraction, viscosity and nonlinearity. The nonlinearity includes a cubic nonlinear term that is equivalent to that present in plane shear waves, as well as a quadratic nonlinear term that is unique to diffracting beams. The work by Wochner et al. [2] considered shear wave beams with translational polarizations (linear, circular and elliptical), wherein second-order nonlinear effects vanish and the leading order nonlinear effect is third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> by the cubic nonlinearity. The purpose of the current work is to investigate the quadratic nonlinear term present in the parabolic equation for shear wave beams by considering second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in Gaussian beams as a second-order nonlinear effect using standard perturbation theory. In order for second-order nonlinear effects to be present, a broader class of source polarizations must be considered that includes not only the familiar translational polarizations, but also polarizations accounting for stretching, shearing and rotation of the source plane. It is found that the polarization of the second <span class="hlt">harmonic</span> <span class="hlt">generated</span> by the quadratic nonlinearity is not necessarily the same as the polarization of the source-frequency beam, and we are able to derive a general analytic solution for second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> from a Gaussian source condition that gives explicitly the relationship between the polarization of the source-frequency beam and the polarization of the second <span class="hlt">harmonic</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OptCo.371..100W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OptCo.371..100W"><span id="translatedtitle">Experimental observation of fundamental and <span class="hlt">harmonic</span> self pulse <span class="hlt">generation</span> of single high-order Stokes in Brillouin Erbium fiber laser</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Xiaorui; Yang, Yanfu; Liu, Meng; Yao, Yong</p> <p>2016-07-01</p> <p>Fundamental and <span class="hlt">harmonic</span> self-pulse <span class="hlt">generation</span> was experimentally observed on both first order and higher order Stokes components. The <span class="hlt">generated</span> pulses with the same order <span class="hlt">harmonic</span> repetition rate are obtained on multiple Stokes components simultaneously. The pulse <span class="hlt">generation</span> on first order Stokes component can be attributed to periodic pump depletion in Brillouin gain medium. The pulse <span class="hlt">generation</span> of high order Stokes component can be considered as pulse oscillation pumped by the former order Stokes. With high Erbium pump power, by setting the proper attenuation between Brillouin medium and Faraday rotation mirror, the <span class="hlt">harmonic</span> pulse <span class="hlt">generations</span> up to fifth order have been achieved.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27531047','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27531047"><span id="translatedtitle">Bright high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> with controllable polarization from a relativistic plasma mirror.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Zi-Yu; Pukhov, Alexander</p> <p>2016-01-01</p> <p>Ultrafast extreme ultraviolet (XUV) sources with a controllable polarization state are powerful tools for investigating the structural and electronic as well as the magnetic properties of materials. However, such light sources are still limited to only a few free-electron laser facilities and, very recently, to high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> from noble gases. Here we propose and numerically demonstrate a laser-plasma scheme to <span class="hlt">generate</span> bright XUV pulses with fully controlled polarization. In this scheme, an elliptically polarized laser pulse is obliquely incident on a plasma surface, and the reflected radiation contains pulse trains and isolated circularly or highly elliptically polarized attosecond XUV pulses. The <span class="hlt">harmonic</span> polarization state is fully controlled by the laser-plasma parameters. The mechanism can be explained within the relativistically oscillating mirror model. This scheme opens a practical and promising route to <span class="hlt">generate</span> bright attosecond XUV pulses with desirable ellipticities in a straightforward and efficient way for a number of applications. PMID:27531047</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4992059','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4992059"><span id="translatedtitle">Bright high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> with controllable polarization from a relativistic plasma mirror</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Chen, Zi-Yu; Pukhov, Alexander</p> <p>2016-01-01</p> <p>Ultrafast extreme ultraviolet (XUV) sources with a controllable polarization state are powerful tools for investigating the structural and electronic as well as the magnetic properties of materials. However, such light sources are still limited to only a few free-electron laser facilities and, very recently, to high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> from noble gases. Here we propose and numerically demonstrate a laser–plasma scheme to <span class="hlt">generate</span> bright XUV pulses with fully controlled polarization. In this scheme, an elliptically polarized laser pulse is obliquely incident on a plasma surface, and the reflected radiation contains pulse trains and isolated circularly or highly elliptically polarized attosecond XUV pulses. The <span class="hlt">harmonic</span> polarization state is fully controlled by the laser–plasma parameters. The mechanism can be explained within the relativistically oscillating mirror model. This scheme opens a practical and promising route to <span class="hlt">generate</span> bright attosecond XUV pulses with desirable ellipticities in a straightforward and efficient way for a number of applications. PMID:27531047</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20632467','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20632467"><span id="translatedtitle">Role of long quantum orbits in high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Milosevic, D.B.; Becker, W.</p> <p>2002-12-01</p> <p>Single-atom high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> is considered in the strong-field approximation, as formulated in the Lewenstein model, and analyzed in terms of quantum orbits. Orbits are classified according to the solutions of the saddle-point equations. The results of a numerical integration are compared with the saddle-point approximation and the uniform approximation. Approximate analytical solutions for long orbits are presented. The formalism developed is used to analyze the enhancement of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> near channel closings. The enhancements exactly at the channel closings are extremely narrow and built up by the constructive interference of a very large number of quantum orbits. Additional broader enhancements occur slightly below channel closings. They are <span class="hlt">generated</span> by the interplay of a medium number of orbits.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001JAP....90.2612C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001JAP....90.2612C"><span id="translatedtitle">Dot patterns from second-<span class="hlt">harmonic</span> and sum-frequency <span class="hlt">generation</span> in polycrystalline ZnSe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chinh, Tran Duc; Seibt, Wolfgang; Siegbahn, Kai</p> <p>2001-09-01</p> <p>During a comparative study of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) and sum-frequency <span class="hlt">generation</span> (SFG) in single-crystal and polycrystalline ZnSe, the polycrystalline material showed a dot pattern in the SHG as well as in the SFG output. No such pattern was found in the output from the single-crystal ZnSe sample. The second-<span class="hlt">harmonic</span> and also the sum-frequency dot pattern, resembling a diffraction pattern, could be observed over a wide tuning range of the fundamental beam, between 1.1 and 1.6 μm, <span class="hlt">generated</span> by a femtosecond optical parametric amplifier. The size of the observed pattern is dependent on wavelength and the dots show a characteristic polarization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013SPIE.8599E..26Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013SPIE.8599E..26Y"><span id="translatedtitle">High energy diode pumped 5th <span class="hlt">harmonic</span> <span class="hlt">generation</span> of Nd: YAG laser</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Yang; Cheng, Chee Yuen; Chia, Yong Poo; Wong, Wee Hoong; Yong, Saw Soon; Qu, Weijuan; Peng, Xiaoyuan</p> <p>2013-03-01</p> <p>This paper reports a high power diode pump 5th <span class="hlt">harmonic</span> <span class="hlt">generation</span> of Nd: YAG laser system, which could <span class="hlt">generate</span> up to 300 mW TEM00 mode output with 100 Hz repetition rate at 213 nm. A diode pump module was specially designed for a high efficiency and good beam quality at the fundamental wavelength 1064 nm. An amplifier was set up out of the cavity to boost up the energy level of fundamental wavelength. In order to get high efficiency of the 5th <span class="hlt">harmonic</span> <span class="hlt">generation</span>, the cavity of the fundamental wavelength is EOM Q-switched which could <span class="hlt">generate</span> very high peak power of the fundamental wavelength laser for extra cavity <span class="hlt">harmonic</span> <span class="hlt">generations</span>. Finally, 14% conversion efficiency from IR to UV was achieved, which is the highest efficiency in the market to the best of our knowledge right now. 213 nm is a very good substitute wavelength of 193 nm for different UV applications, the system of which is more compact, higher energy, less maintenance and better beam quality than the system of 193 nm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25895003','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25895003"><span id="translatedtitle">Mode matching in multiresonant plasmonic nanoantennas for enhanced second <span class="hlt">harmonic</span> <span class="hlt">generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Celebrano, Michele; Wu, Xiaofei; Baselli, Milena; Großmann, Swen; Biagioni, Paolo; Locatelli, Andrea; De Angelis, Costantino; Cerullo, Giulio; Osellame, Roberto; Hecht, Bert; Duò, Lamberto; Ciccacci, Franco; Finazzi, Marco</p> <p>2015-05-01</p> <p>Boosting nonlinear frequency conversion in extremely confined volumes remains a challenge in nano-optics research, but can enable applications in nanomedicine, photocatalysis and background-free biosensing. To obtain brighter nonlinear nanoscale sources, approaches that enhance the electromagnetic field intensity and counter the lack of phase matching in nanoplasmonic systems are often employed. However, the high degree of symmetry in the crystalline structure of plasmonic materials (metals in particular) and in nanoantenna designs strongly quenches second <span class="hlt">harmonic</span> <span class="hlt">generation</span>. Here, we describe doubly-resonant single-crystalline gold nanostructures with no axial symmetry displaying spatial mode overlap at both the excitation and second <span class="hlt">harmonic</span> wavelengths. The combination of these features allows the attainment of a nonlinear coefficient for second <span class="hlt">harmonic</span> <span class="hlt">generation</span> of ∼5 × 10(-10) W(-1), enabling a second <span class="hlt">harmonic</span> photon yield higher than 3 × 10(6) photons per second. Theoretical estimations point toward the use of our nonlinear plasmonic nanoantennas as efficient platforms for label-free molecular sensing. PMID:25895003</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatNa..10..412C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatNa..10..412C"><span id="translatedtitle">Mode matching in multiresonant plasmonic nanoantennas for enhanced second <span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Celebrano, Michele; Wu, Xiaofei; Baselli, Milena; Großmann, Swen; Biagioni, Paolo; Locatelli, Andrea; de Angelis, Costantino; Cerullo, Giulio; Osellame, Roberto; Hecht, Bert; Duò, Lamberto; Ciccacci, Franco; Finazzi, Marco</p> <p>2015-05-01</p> <p>Boosting nonlinear frequency conversion in extremely confined volumes remains a challenge in nano-optics research, but can enable applications in nanomedicine, photocatalysis and background-free biosensing. To obtain brighter nonlinear nanoscale sources, approaches that enhance the electromagnetic field intensity and counter the lack of phase matching in nanoplasmonic systems are often employed. However, the high degree of symmetry in the crystalline structure of plasmonic materials (metals in particular) and in nanoantenna designs strongly quenches second <span class="hlt">harmonic</span> <span class="hlt">generation</span>. Here, we describe doubly-resonant single-crystalline gold nanostructures with no axial symmetry displaying spatial mode overlap at both the excitation and second <span class="hlt">harmonic</span> wavelengths. The combination of these features allows the attainment of a nonlinear coefficient for second <span class="hlt">harmonic</span> <span class="hlt">generation</span> of ˜5 × 10-10 W-1, enabling a second <span class="hlt">harmonic</span> photon yield higher than 3 × 106 photons per second. Theoretical estimations point toward the use of our nonlinear plasmonic nanoantennas as efficient platforms for label-free molecular sensing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25049378','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25049378"><span id="translatedtitle"><span class="hlt">Harmonization</span> of initial estimates of shale gas life cycle greenhouse gas emissions for electric power <span class="hlt">generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Heath, Garvin A; O'Donoughue, Patrick; Arent, Douglas J; Bazilian, Morgan</p> <p>2014-08-01</p> <p>Recent technological advances in the recovery of unconventional natural gas, particularly shale gas, have served to dramatically increase domestic production and reserve estimates for the United States and internationally. This trend has led to lowered prices and increased scrutiny on production practices. Questions have been raised as to how greenhouse gas (GHG) emissions from the life cycle of shale gas production and use compares with that of conventionally produced natural gas or other fuel sources such as coal. Recent literature has come to different conclusions on this point, largely due to differing assumptions, comparison baselines, and system boundaries. Through a meta-analytical procedure we call <span class="hlt">harmonization</span>, we develop robust, analytically consistent, and updated comparisons of estimates of life cycle GHG emissions for electricity produced from shale gas, conventionally produced natural gas, and coal. On a per-unit electrical output basis, <span class="hlt">harmonization</span> reveals that median estimates of GHG emissions from shale gas-<span class="hlt">generated</span> electricity are similar to those for conventional natural gas, with both approximately half that of the central tendency of coal. Sensitivity analysis on the <span class="hlt">harmonized</span> estimates indicates that assumptions regarding liquids unloading and estimated ultimate recovery (EUR) of wells have the greatest influence on life cycle GHG emissions, whereby shale gas life cycle GHG emissions could approach the range of best-performing coal-fired <span class="hlt">generation</span> under certain scenarios. Despite clarification of published estimates through <span class="hlt">harmonization</span>, these initial assessments should be confirmed through methane emissions measurements at components and in the atmosphere and through better characterization of EUR and practices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvA..93d3411R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvA..93d3411R"><span id="translatedtitle">Rotating-frame perspective on high-order-<span class="hlt">harmonic</span> <span class="hlt">generation</span> of circularly polarized light</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reich, Daniel M.; Madsen, Lars Bojer</p> <p>2016-04-01</p> <p>We employ a rotating frame of reference to elucidate high-order-<span class="hlt">harmonic</span> <span class="hlt">generation</span> of circularly polarized light by bicircular driving fields. In particular, we show how the experimentally observed circular components of the high-order-<span class="hlt">harmonic</span> spectrum can be directly related to the corresponding quantities in the rotating frame. Supported by numerical simulations of the time-dependent Schrödinger equation, we deduce an optimal strategy for maximizing the cutoff in the high-order-<span class="hlt">harmonic</span> plateau while keeping the two circular components of the emitted light spectrally distinct. Moreover, we show how the rotating-frame picture can be more generally employed for elliptical drivers. Finally, we point out how circular and elliptical driving fields show a near-duality to static electric and magnetic fields in a rotating-frame description. This demonstrates how high-order-<span class="hlt">harmonic</span> <span class="hlt">generation</span> of circularly polarized light under static electromagnetic fields can be emulated in practice even at static field strengths beyond current experimental capabilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27415357','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27415357"><span id="translatedtitle">Underwater <span class="hlt">acoustic</span> wave <span class="hlt">generation</span> by filamentation of terawatt ultrashort laser pulses.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jukna, Vytautas; Jarnac, Amélie; Milián, Carles; Brelet, Yohann; Carbonnel, Jérôme; André, Yves-Bernard; Guillermin, Régine; Sessarego, Jean-Pierre; Fattaccioli, Dominique; Mysyrowicz, André; Couairon, Arnaud; Houard, Aurélien</p> <p>2016-06-01</p> <p><span class="hlt">Acoustic</span> signals <span class="hlt">generated</span> by filamentation of ultrashort terawatt laser pulses in water are characterized experimentally. Measurements reveal a strong influence of input pulse duration on the shape and intensity of the <span class="hlt">acoustic</span> wave. Numerical simulations of the laser pulse nonlinear propagation and the subsequent water hydrodynamics and <span class="hlt">acoustic</span> wave <span class="hlt">generation</span> show that the strong <span class="hlt">acoustic</span> emission is related to the mechanism of superfilamention in water. The elongated shape of the plasma volume where energy is deposited drives the far-field profile of the <span class="hlt">acoustic</span> signal, which takes the form of a radially directed pressure wave with a single oscillation and a very broad spectrum.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27415357','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27415357"><span id="translatedtitle">Underwater <span class="hlt">acoustic</span> wave <span class="hlt">generation</span> by filamentation of terawatt ultrashort laser pulses.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jukna, Vytautas; Jarnac, Amélie; Milián, Carles; Brelet, Yohann; Carbonnel, Jérôme; André, Yves-Bernard; Guillermin, Régine; Sessarego, Jean-Pierre; Fattaccioli, Dominique; Mysyrowicz, André; Couairon, Arnaud; Houard, Aurélien</p> <p>2016-06-01</p> <p><span class="hlt">Acoustic</span> signals <span class="hlt">generated</span> by filamentation of ultrashort terawatt laser pulses in water are characterized experimentally. Measurements reveal a strong influence of input pulse duration on the shape and intensity of the <span class="hlt">acoustic</span> wave. Numerical simulations of the laser pulse nonlinear propagation and the subsequent water hydrodynamics and <span class="hlt">acoustic</span> wave <span class="hlt">generation</span> show that the strong <span class="hlt">acoustic</span> emission is related to the mechanism of superfilamention in water. The elongated shape of the plasma volume where energy is deposited drives the far-field profile of the <span class="hlt">acoustic</span> signal, which takes the form of a radially directed pressure wave with a single oscillation and a very broad spectrum. PMID:27415357</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MPLB...3050226L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MPLB...3050226L"><span id="translatedtitle">Theoretical exploration of <span class="hlt">harmonic</span> emission and attosecond pulse <span class="hlt">generation</span> from H2+ in the presence of terahertz pulse</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Hang; Feng, Liqiang</p> <p>2016-06-01</p> <p><span class="hlt">Harmonic</span> <span class="hlt">generation</span> spectra from H2+ molecule ion driven by the chirped pulse combined with a terahertz (THz) pulse have been theoretically investigated by numerically solving the non-Born-Oppenheimer time-dependent Schrödinger equation (NBO-TDSE). The results show that with the introduction of the chirp, the <span class="hlt">harmonic</span> cutoff is extended, resulting in a smooth supercontinuum. Further, when the initial vibrational state is prepared as v = 3, and by properly adding a THz controlling pulse, the <span class="hlt">harmonic</span> yield is enhanced by almost six orders of magnitude compared with the single chirped pulse case. Quantum analyses are shown to explain the <span class="hlt">harmonic</span> extension and enhancement. Furthermore, through the investigation of the isotopic effect, we find that more intense <span class="hlt">harmonics</span> are <span class="hlt">generated</span> in the lighter nucleus. Finally, by properly superposing the <span class="hlt">harmonics</span>, a series of intense 35 as XUV pulses can be obtained, which are almost six orders of magnitude improvement in comparison with the single chirped pulse case.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1855208','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1855208"><span id="translatedtitle">Noninvasive corneal stromal collagen imaging using two-photon-<span class="hlt">generated</span> second-<span class="hlt">harmonic</span> signals</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Morishige, Naoyuki; Petroll, W. Matthew; Nishida, Teruo; Kenney, M. Cristina; Jester, James V.</p> <p>2007-01-01</p> <p>PURPOSE To investigate the feasibility of using femtosecond-pulse lasers to produce second-<span class="hlt">harmonic</span> <span class="hlt">generated</span> (SHG) signals to noninvasively assess corneal stromal collagen organization. SETTING The Eye Institute, University of California, Irvine, California, USA. METHODS Mouse, rabbit, and human corneas were examined by two-photon confocal microscopy using a variable-wavelength femtosecond lasers to produce SHG signals. Two types were detected: forward scattered and backward scattered. Wavelength dependence of the SHG signal was confirmed by spectral separation using the 510 Meta (Zeiss). To verify the spatial relation between SHG signals and corneal cells, staining of cytoskeletons and nuclei was performed. RESULTS Second-<span class="hlt">harmonic-generated</span> signal intensity was strongest with an excitation wavelength of 800 nm for all 3 species. Second-<span class="hlt">harmonic-generated</span> forward signals showed a distinct fibrillar pattern organized into bands suggesting lamellae, while backscattered SHG signals appeared more diffuse and indistinct. Reconstruction of SHG signals showed two patterns of lamellar organization: highly interwoven in the anterior stroma and orthogonally arranged in the posterior stroma. Unique to the human cornea was the presence of transverse, sutural lamellae that inserted into Bowman’s layer, suggesting an anchoring function. CONCLUSIONS Using two-photon confocal microscopy to <span class="hlt">generate</span> SHG signals from the corneal collagen provides a powerful new approach to noninvasively study corneal structure. Human corneas had a unique organizational pattern with sutural lamellae to provide important biomechanical support that was not present in mouse or rabbit corneas. PMID:17081858</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SPIE.9038E..0WH','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SPIE.9038E..0WH"><span id="translatedtitle">Investigation of pulmonary <span class="hlt">acoustic</span> simulation: comparing airway model <span class="hlt">generation</span> techniques</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Henry, Brian; Dai, Zoujun; Peng, Ying; Mansy, Hansen A.; Sandler, Richard H.; Royston, Thomas</p> <p>2014-03-01</p> <p>Alterations in the structure and function of the pulmonary system that occur in disease or injury often give rise to measurable spectral, spatial and/or temporal changes in lung sound production and transmission. These changes, if properly quantified, might provide additional information about the etiology, severity and location of trauma, injury, or pathology. With this in mind, the authors are developing a comprehensive computer simulation model of pulmonary <span class="hlt">acoustics</span>, known as The Audible Human Project™. Its purpose is to improve our understanding of pulmonary <span class="hlt">acoustics</span> and to aid in interpreting measurements of sound and vibration in the lungs <span class="hlt">generated</span> by airway insonification, natural breath sounds, and external stimuli on the chest surface, such as that used in elastography. As a part of this development process, finite element (FE) models were constructed of an excised pig lung that also underwent experimental studies. Within these models, the complex airway structure was created via two methods: x-ray CT image segmentation and through an algorithmic means called Constrained Constructive Optimization (CCO). CCO was implemented to expedite the segmentation process, as airway segments can be grown digitally. These two approaches were used in FE simulations of the surface motion on the lung as a result of sound input into the trachea. Simulation results were compared to experimental measurements. By testing how close these models are to experimental measurements, we are evaluating whether CCO can be used as a means to efficiently construct physiologically relevant airway trees.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995JOSAB..12.1581T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995JOSAB..12.1581T"><span id="translatedtitle">Phase-matched second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in poled polymers by the use of birefringence</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tao, X. T.; Watanabe, T.; Zou, D. C.; Ukuda, H.; Miyata, S.</p> <p>1995-09-01</p> <p>Green light has been observed for the first time to the authors' knowledge by bulk phase-matched second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> from a stretched main chain polyurea. The polyurea was synthesized from 4,4'-diphenylmethane diisocyanate and 4,4'-methylene bis(cyclohexylamine). The spin-coated film has an initial positive birefringence. Drawing further increased the birefringence, and the film can be used for phase matching just as in biaxial single crystals. The drawn and poled polymer films belong to the 2mm point group. Three independent nonlinear-optic coefficients were determined. The type I phase-matching characteristics were calculated and confirmed by experiments. We demonstrate that a highly effective second-<span class="hlt">harmonic-generation</span> device with a long optical path length can be obtained by use of bulk phase-matchable poled polymer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21117728','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21117728"><span id="translatedtitle">Higher <span class="hlt">harmonic</span> <span class="hlt">generation</span> in nonlinear waveguides of arbitrary cross-section.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Srivastava, Ankit; Bartoli, Ivan; Salamone, Salvatore; Lanza di Scalea, Francesco</p> <p>2010-05-01</p> <p>This article concerns the <span class="hlt">generation</span> and properties of double <span class="hlt">harmonics</span> in nonlinear isotropic waveguides of complex cross-section. Analytical solutions of nonlinear Rayleigh-Lamb waves and rod waves have been known for some time. These solutions explain the phenomenon of cumulative double <span class="hlt">harmonic</span> <span class="hlt">generation</span> of guided waves. These solutions, however, are only applicable to simple geometries. This paper combines the general approach of the analytical solutions with semi-analytical finite element models to generalize the method to more complex geometries, specifically waveguides with arbitrary cross-sections. Supporting comparisons with analytical solutions are presented for simple cases. This is followed by the study of the case of a rail track. One reason for studying nonlinear guided waves in rails is the potential measurement of thermal stresses in welded rail.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JSV...381..206B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JSV...381..206B"><span id="translatedtitle"><span class="hlt">Generation</span> of higher <span class="hlt">harmonics</span> in longitudinal vibration of beams with breathing cracks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Broda, D.; Pieczonka, L.; Hiwarkar, V.; Staszewski, W. J.; Silberschmidt, V. V.</p> <p>2016-10-01</p> <p>Classical nonlinear vibration methods used for structural damage detection are often based on higher- and sub-<span class="hlt">harmonic</span> <span class="hlt">generation</span>. However, nonlinearities arising from sources other than damage - e.g. boundary conditions or a measurement chain - are a primary concern in these methods. This paper focuses on localisation of damage-related nonlinearities based on higher <span class="hlt">harmonic</span> <span class="hlt">generation</span>. Numerical and experimental investigations in longitudinal vibration of beams with breathing cracks are presented. Numerical modelling is performed using a two-dimensional finite element approach. Different crack depths, locations and boundary conditions are investigated. The results demonstrate that nonlinearities in cracked beams are particularly strong in the vicinity of damage, allowing not only for damage localisation but also for separation of crack induced nonlinearity from other sources of nonlinearities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OptMa..60..552G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OptMa..60..552G"><span id="translatedtitle">Active control of highly efficient third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in ultrathin nonlinear metasurfaces</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gong, Zibo; Li, Chong; Hu, Xiaoyong; Yang, Hong; Gong, Qihuang</p> <p>2016-10-01</p> <p>Active electric control of highly efficient third <span class="hlt">harmonic</span> <span class="hlt">generation</span> was realized in an ultrathin nonlinear metasurface by using a nanocomposite consisting of gold nanoparticles dispersed in polycrystalline strontium titanate as the electro-optic material. Owing to the nonlinearity enhancement associated with the slow light effect, quantum confinement effect, and field-reinforcement, a high conversion efficiency of 3 × 10-5 was obtained, which is two orders of magnitude larger than previously reported efficiencies at comparable pump intensities. A modulation of 12% in the intensity of the third <span class="hlt">harmonic</span> <span class="hlt">generation</span> and a 30-nm shift in the transparency window center were achieved by varying the applied voltage from -30 V to zero. Our results pave the way toward the realization of multi-functional integrated photonic devices and chips based on metasurfaces.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/866960','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/866960"><span id="translatedtitle">Multiple layer optical memory system using second-<span class="hlt">harmonic-generation</span> readout</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Boyd, Gary T.; Shen, Yuen-Ron</p> <p>1989-01-01</p> <p>A novel optical read and write information storage system is described which comprises a radiation source such as a laser for writing and illumination, the radiation source being capable of radiating a preselected first frequency; a storage medium including at least one layer of material for receiving radiation from the radiation source and capable of being surface modified in response to said radiation source when operated in a writing mode and capable of <span class="hlt">generating</span> a pattern of radiation of the second <span class="hlt">harmonic</span> of the preselected frequency when illuminated by the radiation source at the preselected frequency corresponding to the surface modifications on the storage medium; and a detector to receive the pattern of second <span class="hlt">harmonic</span> frequency <span class="hlt">generated</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/389377','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/389377"><span id="translatedtitle">Efficient Co-<span class="hlt">Generation</span> of Seventh-<span class="hlt">Harmonic</span> Radiation in Cyclotron Autoresonance Acceleration</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wang, C.; Hirshfield, J.L.; Ganguly, A.K. |</p> <p>1996-10-01</p> <p>It is shown that the lowest TE{sub {ital s},{ital l}} mode in a cylindrical waveguide at frequency {ital s}{omega}, with group velocity nearly identical to group velocity for the TE{sub 11} mode at frequency {omega}, is that with {ital s}=7, {ital l}=2. This allows coherent radiation to be <span class="hlt">generated</span> at the seventh <span class="hlt">harmonic</span> during electron autoresonance acceleration. Conditions are found where such co-<span class="hlt">generation</span> of 7th <span class="hlt">harmonic</span> power at 20GHz is possible with overall efficiency greater than 80{percent}. This mechanism could make possible high efficiency cm-wavelength high power rf sources suitable for driving a future multi-TeV electron-position collider. {copyright} {ital 1996 The American Physical Society.}</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JMOp...63..643M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JMOp...63..643M"><span id="translatedtitle">Electron path control of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> by a spatially inhomogeneous field</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mohebbi, Masoud; Nazarpoor Malaei, Sakineh</p> <p>2016-04-01</p> <p>We theoretically investigate the control of high-order <span class="hlt">harmonics</span> cut-off and as-pulse <span class="hlt">generation</span> by a chirped laser field using a metallic bow tie-shaped nanostructure. The numerical results show that the trajectories of the electron wave packet are strongly modified, the short quantum path is enhanced, the long quantum path is suppressed and the low modulated spectrum of the <span class="hlt">harmonics</span> can be remarkably extended. Our calculated results also show that, by confining electron motion, a broadband supercontinuum with the width of 1670 eV can be produced which directly <span class="hlt">generates</span> an isolated 34 as-pulse without phase compensation. To explore the underlying mechanism responsible for the cut-off extension and the quantum path selection, we perform time-frequency analysis and a classical simulation based on the three-step model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002ApPhL..81..718B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002ApPhL..81..718B"><span id="translatedtitle">Microwave frequency tuning and <span class="hlt">harmonic</span> <span class="hlt">generation</span> in ferroelectric thin film transmission lines</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Booth, James C.; Ono, R. H.; Takeuchi, Ichiro; Chang, Kao-Shuo</p> <p>2002-07-01</p> <p>We evaluate dielectric tuning on nanosecond time scales in ferroelectric Ba0.3Sr0.7TiO3 thin films by measuring nonlinear <span class="hlt">harmonic</span> <span class="hlt">generation</span> at a fundamental frequency of 3 GHz. We compare the form of the distributed nonlinear capacitance per unit length C(Vrf) extracted from a simple model of <span class="hlt">harmonic</span> <span class="hlt">generation</span> in coplanar waveguide transmission line structures with the nonlinear capacitance C(Vdc) measured using a dc bias voltage, and obtain excellent agreement for temperatures in the range 235-295 K. This demonstrated agreement implies that full dielectric tuning can be expected in these ferroelectric thin films on nanosecond time scales, and also demonstrates that detrimental high-frequency nonlinear effects in device structures can be accurately predicted based on dc biased measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990IJQE...26.1384L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990IJQE...26.1384L"><span id="translatedtitle">Cerenkov configuration second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in proton-exchanged lithium niobate guides</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, M. J.; de Micheli, M.; He, Q.; Ostrowsky, D. B.</p> <p>1990-08-01</p> <p>A theoretical and experimental study of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> using the Cerenkov configuration with proton-exchanged lithium niobate guides is presented. The analytic solution of the problem for the case of planar step-index guides makes it possible to identify the essential role played by the discontinuity of the nonlinear polarization at the guide-substrate interface. This leads to the prediction of an increasing conversion efficiency for decreasing values of guide nonlinearity. It is shown that the experimental results are consistent with a reduction of 50 to 70 percent of the value of the nonlinear coefficient in unannealed waveguides fabricated in slightly diluted or pure benzoic acid. The results presented permit the optimization of guide design for efficient second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in the Cerenkov configuration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvB..94k5303G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvB..94k5303G"><span id="translatedtitle">Dynamical calculation of third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in a semiconductor quantum well</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guazzotti, Stefano; Pusch, Andreas; Reiter, Doris E.; Hess, Ortwin</p> <p>2016-09-01</p> <p>Nonlinear phenomena in optically excited semiconductor structures are of high interest. Here we develop a model capable of studying the dynamics of the photoexcited carriers, including Coulomb interaction on a Hartree-Fock level, on the same footing as the dynamics of the light field impinging on an arbitrary photonic structure. Applying this method to calculate the third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in a semiconductor quantum well embedded in a Bragg mirror structure, we find that the power-law exponent of the intensity dependence of the third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> depends on the frequency of the exciting pulse. Off-resonant pulses follow the expected cubic dependence, while the exponent is smaller for resonant pulses due to saturation effects in the induced carrier density. Our study provides a detailed understanding of the carrier and light field dynamics during nonlinear processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20640935','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20640935"><span id="translatedtitle">Optimal control of attosecond pulse synthesis from high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ben Haj Yedder, A.; Le Bris, C.; Atabek, O.; Chelkowski, S.; Bandrauk, A. D.</p> <p>2004-04-01</p> <p>Numerical solutions of the time-dependent Schroedinger equation for a three-dimensional H atom and an efficient genetic algorithm are used to optimize short intense excitation laser pulses in order to <span class="hlt">generate</span> high-order <span class="hlt">harmonics</span> from which we synthesize single attosecond pulses. It is shown that chirping of excitation pulses at intensities {approx}10{sup 14} W/cm{sup 2} and duration of up to {approx}16 fs can lead to synthesis of single attosecond pulses. The optimal excitation pulses and the phases of the <span class="hlt">generated</span> <span class="hlt">harmonics</span> are compared with the nonoptimized ones, showing thus the usefulness of genetic algorithm schemes in the search of optimal conditions for synthesizing single attosecond pulses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3539190','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3539190"><span id="translatedtitle">Determination of chronological aging parameters in epidermal keratinocytes by in vivo <span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Liao, Yi-Hua; Chen, Szu-Yu; Chou, Sin-Yo; Wang, Pei-Hsun; Tsai, Ming-Rung; Sun, Chi-Kuang</p> <p>2012-01-01</p> <p>Skin aging is an important issue in geriatric and cosmetic dermatology. To quantitatively analyze changes in keratinocytes related to intrinsic aging, we exploited a 1230 nm-based in vivo <span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy, combining second- and third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> modalities. 52 individuals (21 men and 31 women, age range 19–79) were examined on the sun-protected volar forearm. Through quantitative analysis by the standard algorithm provided, we found that the cellular and nuclear size of basal keratinocytes, but not that of granular cells, was significantly increased with advancing age. The cellular and nuclear areas, which have an increase of 0.51 μm2 and 0.15 μm2 per year, respectively, can serve as scoring indices for intrinsic skin aging. PMID:23304649</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22261623','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22261623"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> from metamaterials strongly coupled to intersubband transitions in quantum wells</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Campione, Salvatore; Benz, Alexander; Brener, Igal; Sinclair, Michael B.; Capolino, Filippo</p> <p>2014-03-31</p> <p>We theoretically analyze the second <span class="hlt">harmonic</span> <span class="hlt">generation</span> capacity of two-dimensional periodic metamaterials comprising sub-wavelength resonators strongly coupled to intersubband transitions in quantum wells (QWs) at mid-infrared frequencies. The metamaterial is designed to support a fundamental resonance at ∼30 THz and an orthogonally polarized resonance at the second <span class="hlt">harmonic</span> frequency (∼60 THz), while the asymmetric quantum well structure is designed to provide a large second order susceptibility. Upon continuous wave illumination at the fundamental frequency we observe second <span class="hlt">harmonic</span> signals in both the forward and backward directions, with the forward efficiency being larger. We calculate the overall second <span class="hlt">harmonic</span> conversion efficiency of the forward wave to be ∼1.3 × 10{sup −2} W/W{sup 2}—a remarkably large value, given the deep sub-wavelength dimensions of the QW structure (about 1/15th of the free space wavelength of 10 μm). The results shown in this Letter provide a strategy for designing easily fabricated sources across the entire infrared spectrum through proper choice of QW and resonator designs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10123997','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10123997"><span id="translatedtitle">High conversion efficiency pumped-cavity second <span class="hlt">harmonic</span> <span class="hlt">generation</span> of a diode laser</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Keicher, D.M.</p> <p>1994-01-01</p> <p>To investigate the feasibility of producing a compact, efficient blue laser source, pumped-cavity second <span class="hlt">harmonic</span> <span class="hlt">generation</span> of diode lasers was explored. It is desirable to have such lasers to increase optical disk storage density, for color displays and for under-the-sea green-blue optical signal transmission. Based on assumed cavity losses, a cavity was designed and numerical analysis predicted an overall conversion efficiency to the second <span class="hlt">harmonic</span> wavelength of 76% from a 75 mW diode laser. The diode laser used in these experiments had a single longitudinal and a single transverse mode output at 860 nm. The best conversion efficiency obtained (26%) was less than optimum due to the 2.5% single-pass linear losses associated with the cavity. However, calculations based on these higher losses are in good agreement with the experimentally determined values. In additions, a factor of 1.65 increase in the second <span class="hlt">harmonic</span> output power is anticipated by reducing the input mirror reflectivity to better impedance-match the cavity. With this relatively low second <span class="hlt">harmonic</span> conversion, the power to light conversion is 7.8%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SPIE.9523E..0GK','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SPIE.9523E..0GK"><span id="translatedtitle">High-contrast imaging of mycobacterium tuberculosis using third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Bo Ram; Lee, Eungjang; Park, Seung-Han</p> <p>2015-07-01</p> <p>Nonlinear optical microcopy has become an important tool in investigating biomaterials due to its various advantages such as label-free imaging capabilities. In particular, it has been shown that third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) signals can be produced at interfaces between an aqueous medium (e.g. cytoplasm, interstitial fluid) and a mineralized lipidic surface. In this work, we have demonstrated that label-free high-contrast THG images of the mycobacterium tuberculosis can be obtained using THG microscopy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009LaPhy..19.1475F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009LaPhy..19.1475F"><span id="translatedtitle">In vivo polarization dependant Second and Third <span class="hlt">harmonic</span> <span class="hlt">generation</span> imaging of Caenorhabditis elegans pharyngeal muscles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Filippidis, G.; Troulinaki, K.; Fotakis, C.; Tavernarakis, N.</p> <p>2009-07-01</p> <p>In this study Second and Third <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG-THG) imaging measurements were performed to the pharyngeal muscles of the nematode Caenorhabditis elegans, in vivo with linearly polarized laser beam. Complementary information about the anatomy of the pharynx and the morphology of the anterior part of the worm were extracted. THG signals proved to have no dependence on incident light polarization, while SHG images are highly sensitive to the changes of the incident linearly polarized light.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008SPIE.7135E..19Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008SPIE.7135E..19Z"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in periodically poled lithium niobate waveguide using femtosecond laser pulses</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Shuanggen; Yao, Jianghong; Fan, Yaxian; Liu, Weiwei; Liu, Yange; Shi, Qing; Huang, Zhangchao; Lu, Fuyun</p> <p>2008-11-01</p> <p>We present in this paper the fabrication and characterization of thermally stable double line waveguides in Z-cut periodically poled Lithium Niobate crystals. The waveguides were fabricated by using a femto-second laser, and utilized for second-<span class="hlt">harmonic</span> <span class="hlt">generation</span>. Our experiments have shown that a quasi-phase matching wavelength of 1548.2 nm, a tuning bandwidth of 2 nm, and a tuning temperature range of 150.4+/-1.6°C can be achieved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011JPhCS.277a2046Y&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011JPhCS.277a2046Y&link_type=ABSTRACT"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> imaging of dermal collagen component in human keloid tissue</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, H. B.; Chen, S.; Zhu, X. Q.; Yang, H. Q.; Chen, J. X.</p> <p>2011-01-01</p> <p>In this paper, we report second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) imaging of human keloid tissue. High resolution SHG images of collagen component were obtained in the superficial, medial and deep dermis of human keloid tissue, respectively. Our results show that this method has a capability to observe the structure of collagen component in human keloid tissue, which will help to better understand the formation process of human keloid scar at the molecular level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PhRvA..80e3404Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PhRvA..80e3404Y"><span id="translatedtitle">Recollision dynamics of electron wave packets in high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yuan, Kai-Jun; Bandrauk, André D.</p> <p>2009-11-01</p> <p>We numerically investigate the dynamics of recollision of an electron in high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) for an H atom and a molecular ion H2+ using a short (ten optical cycles), and intense (I0≥1014W/cm2) , z -polarized linear laser pulse with wavelength 800 nm by accurately solving the three-dimensional time-dependent Schrödinger equation. A time-frequency analysis obtained via Gabor transforms is employed to identify electron recollision and recombination times responsible for the <span class="hlt">generation</span> of <span class="hlt">harmonics</span>. We find that the HHG spectra are mainly attributed to the recollision of an inner electron wave packet with the parent ion in agreement with the classical recollision model. A time delay of the electron recollision occurs between wave packets in inner and outer regions, near to and far from the parent ion, due to different phase of the acceleration (as well as dipole velocity) of the electron. Inner wave packets at recollision contain mainly short and long trajectories whereas outer wave packets contain only single trajectories. Lower-order <span class="hlt">harmonics</span> are <span class="hlt">generated</span> mainly by single recollisions near field extrema, i.e., in strong electric fields whereas higher-order <span class="hlt">harmonics</span> are <span class="hlt">generated</span> by double trajectories with different intensities. In the case of H2+ at a critical nuclear distance for charge resonance enhanced ionization, we also find that HHG mainly comes from contributions of the inner electron wave packet, but with more complex recollision trajectories due to the presence of more than one Coulomb center. Triple recollision trajectories are shown to occur generally for the latter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14524944','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14524944"><span id="translatedtitle">Optical second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> enhanced by a twist defect in ferroelectric liquid crystals.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hoshi, Hajime; Ishikawa, Ken; Takezoe, Hideo</p> <p>2003-08-01</p> <p>Second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) spectra were numerically calculated in ferroelectric liquid crystals with a twist defect. It is shown that SHG is enhanced when the SHG wavelength is close to the defect mode. The spectral width of the enhanced peak becomes sharper with increasing the sample thickness at the same rate for the width of the defect mode peak. The SHG peak intensity increases with about seventh power of the sample thickness.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE.9891E..0SC','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE.9891E..0SC"><span id="translatedtitle">Periodically poled LiNbO3 ridge waveguides on silicon for second-<span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chauvet, Mathieu; Henrot, Fabien; Gauthier-Manuel, Ludovic; Devaux, Fabrice; Pêcheur, Vincent; Maillotte, Hervé; Bassignot, Florent; Dahmani, Brahim</p> <p>2016-05-01</p> <p>Nonlinear periodically poled ridge LiNbO3 waveguides have been fabricated on silicon substrates. Components are micromachined with a precision dicing machine and/or by grinding or polishing steps. They show efficient second <span class="hlt">harmonic</span> <span class="hlt">generation</span> at telecommunication wavelengths with normalized conversion reaching 600%/W in a 20mm long device. Influence of geometrical non uniformities of waveguides due to fabrication process is asserted. Components characteristics are studied notably their robustness and tunability versus temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23938493','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23938493"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in a low-loss orientation-patterned GaAs waveguide.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fedorova, K A; McRobbie, A D; Sokolovskii, G S; Schunemann, P G; Rafailov, E U</p> <p>2013-07-15</p> <p>The technology of low-loss orientation-patterned gallium arsenide (OP-GaAs) waveguided crystals was developed and realized by reduction of diffraction scattering on the waveguide pattern. The propagation losses in the OP-GaAs waveguide were estimated to be as low as 2.1 dB/cm, thus demonstrating the efficient second <span class="hlt">harmonic</span> <span class="hlt">generation</span> at 1621 nm under an external pumping.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6113956','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6113956"><span id="translatedtitle">Theory of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> of molecular systems: The steady-state case</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lin, S.H.; Alden, R.G. ); Villaeys, A.A.; Pflumio, V. )</p> <p>1993-10-01</p> <p>In this paper, a general formalism for treating both steady-state and time-resolved second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> for molecular systems is presented. Here, only the steady-state case will be reported. The adiabatic approximation is introduced. Four important cases, resonance-resonance, resonance--off-resonance, off-resonance--resonance, and off-resonance--off-resonance transitions, have been considered. Finally, numerical calculations of rhodamine 6G are performed to demonstrate the applications of theoretical results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5287723','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5287723"><span id="translatedtitle">Multiphoton ionization and third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in atoms and molecules</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Compton, R.N.</p> <p>1982-01-01</p> <p>Resonantly enhanced multiphoton ionization (REMPI) provides a powerful new method for investigating atomic and molecular energy levels. The method is particularly useful in discovering and characterizing certain optically forbidden transitions. The method is particularly well suited for studying Rydberg transitions in molecules and is experimentally easier than the traditional use of far ultraviolet radiation in conventional spectroscopy. Research on multiphoton ionization and third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> is reviewed. (WHK)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JAP...106b3110D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JAP...106b3110D"><span id="translatedtitle">Diffractive imaging using a polychromatic high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> soft-x-ray source</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dilanian, Ruben A.; Chen, Bo; Williams, Garth J.; Quiney, Harry M.; Nugent, Keith A.; Teichmann, Sven; Hannaford, Peter; Dao, Lap V.; Peele, Andrew G.</p> <p>2009-07-01</p> <p>A new approach to diffractive imaging using polychromatic diffraction data is described. The method is tested using simulated and experimental data and is shown to yield high-quality reconstructions. Diffraction data produced using a high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> source are considered explicitly here. The formalism can be readily adapted, however, to any short-wavelength source producing a discrete spectrum and possessing sufficient spatial coherence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE.9884E..2BC','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE.9884E..2BC"><span id="translatedtitle">Enhanced second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> driven from magnetic dipole resonance in AlGaAs nanoantennas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carletti, Luca; Rocco, Davide; Locatelli, Andrea; Gili, Valerio; Leo, Giuseppe; De Angelis, Costantino</p> <p>2016-04-01</p> <p>We model the linear and nonlinear optical response of disk-shaped AlGaAs nanoantennas. We design nanoantennas with a magnetic dipole resonant mode in the near-infrared wavelength range, and we analyze volume second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> driven by a magnetic dipole resonance by predicting a conversion efficiency exceeding 10-3 with 1 GW/cm2 of pump intensity.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1014921','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1014921"><span id="translatedtitle">Quasi-phase matching and quantum control of high <span class="hlt">harmonic</span> <span class="hlt">generation</span> in waveguides using counterpropagating beams</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Zhang, Xiaoshi; Lytle, Amy L.; Cohen, Oren; Kapteyn, Henry C.; Murnane, Margaret M.</p> <p>2010-11-09</p> <p>All-optical quasi-phase matching (QPM) uses a train of counterpropagating pulses to enhance high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) in a hollow waveguide. A pump pulse enters one end of the waveguide, and causes HHG in the waveguide. The counterpropagation pulses enter the other end of the waveguide and interact with the pump pulses to cause QPM within the waveguide, enhancing the HHG.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/385665','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/385665"><span id="translatedtitle">Frequency-resolved optical-gating measurements of ultrashort pulses using surface third-<span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tsang, T.; Krumbuegel, M.A.; DeLong, K.W.; Fittinghoff, D.N.; Trebino, R.</p> <p>1996-09-01</p> <p>We demonstrate what is to our knowledge the first frequency-resolved optical gating (FROG) technique to measure ultrashort pulses from an unamplified Ti:sapphire laser oscillator without direction-of-time ambiguity. This technique utilizes surface third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> as the nonlinear-optical effect and, surprisingly, is the most sensitive third-order FROG geometry yet. {copyright} {ital 1996 Optical Society of America.}</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3983109','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3983109"><span id="translatedtitle"><span class="hlt">Harmonic</span> Hopping, and Both Punctuated and Gradual Evolution of <span class="hlt">Acoustic</span> Characters in Selasphorus Hummingbird Tail-Feathers</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Clark, Christopher James</p> <p>2014-01-01</p> <p>Models of character evolution often assume a single mode of evolutionary change, such as continuous, or discrete. Here I provide an example in which a character exhibits both types of change. Hummingbirds in the genus Selasphorus produce sound with fluttering tail-feathers during courtship. The ancestral character state within Selasphorus is production of sound with an inner tail-feather, R2, in which the sound usually evolves gradually. Calliope and Allen's Hummingbirds have evolved autapomorphic <span class="hlt">acoustic</span> mechanisms that involve feather-feather interactions. I develop a source-filter model of these interactions. The ‘source’ comprises feather(s) that are both necessary and sufficient for sound production, and are aerodynamically coupled to neighboring feathers, which act as filters. Filters are unnecessary or insufficient for sound production, but may evolve to become sources. Allen's Hummingbird has evolved to produce sound with two sources, one with feather R3, another frequency-modulated sound with R4, and their interaction frequencies. Allen's R2 retains the ancestral character state, a ∼1 kHz “ghost” fundamental frequency masked by R3, which is revealed when R3 is experimentally removed. In the ancestor to Allen's Hummingbird, the dominant frequency has ‘hopped’ to the second <span class="hlt">harmonic</span> without passing through intermediate frequencies. This demonstrates that although the fundamental frequency of a communication sound may usually evolve gradually, occasional jumps from one character state to another can occur in a discrete fashion. Accordingly, mapping <span class="hlt">acoustic</span> characters on a phylogeny may produce misleading results if the physical mechanism of production is not known. PMID:24722049</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20717969','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20717969"><span id="translatedtitle">High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> by chirped and self-guided femtosecond laser pulses. II. Time-frequency analysis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tosa, V.; Kim, H.T.; Kim, I.J.; Nam, C.H.</p> <p>2005-06-15</p> <p>We present a time-dependent analysis of high-order <span class="hlt">harmonics</span> <span class="hlt">generated</span> by a self-guided femtosecond laser pulse propagating through a long gas jet. A three-dimensional model is used to calculate the <span class="hlt">harmonic</span> fields <span class="hlt">generated</span> by laser pulses, which only differ by the sign of their initial chirp. The time-frequency distributions of the single-atom dipole and <span class="hlt">harmonic</span> field reveal the dynamics of <span class="hlt">harmonic</span> <span class="hlt">generation</span> in the cutoff. A time-dependent phase-matching calculation was performed, taking into account the self-phase modulation of the laser field. Good phase matching holds for only few optical cycles, being dependent on the electron trajectory. When the cutoff trajectory is phase matched, emitted <span class="hlt">harmonics</span> are locked in phase and the emission intensity is maximized.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20640076','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20640076"><span id="translatedtitle">Impact of electron ionization on the <span class="hlt">generation</span> of high-order <span class="hlt">harmonics</span> from molecules</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Brener, S.; Moiseyev, N.; Ivanov, M. V.</p> <p>2003-08-01</p> <p>When the laser frequency is tuned to be equal to the molecular electronic excitation, high-order <span class="hlt">harmonics</span> are <span class="hlt">generated</span> due to the electronic dipole transitions between the corresponding two potential-energy surfaces (PES). A natural, often taken, choice is the PES of the field-free molecular system. In this special choice the ionization phenomenon is not considered. Only the effect of the dissociation is considered. The method we developed enables one to remain within the framework of the 2-PES approximation and yet to include also the ionization effect in the calculations of molecular high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> spectra. In this approach the coupling between the electronic and nuclear motions is taken into consideration by using coupled complex adiabatic PES. As an illustrative numerical example, we calculated the high <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) spectra of H{sub 2}{sup +} in a 730-nm laser with the intensity of 8.77x10{sup 13} W/cm{sup 2}. The inclusion of the ionization in our approach not only enables the electrons to tunnel through the effective static potential barrier, but also apply an asymmetric force which accelerates the electron before ionization takes place. Therefore, indirectly the inclusion of the ionization by the laser field may lead eventually to an enhanced HHG spectra in comparison with the calculated one when the ''natural'' choice of the field-free 2PES is taken.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015OptCo.353...96M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015OptCo.353...96M"><span id="translatedtitle"><span class="hlt">Generation</span> of tunable ultrafast ultraviolet third <span class="hlt">harmonic</span> by collinear compensation of group-velocity mismatch</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meng, Xianghao; Liu, Huagang; Huang, Jianhong; Wu, Hongchun; Deng, Jing; Dai, Shutao; Weng, Wen; Lin, Wenxiong</p> <p>2015-10-01</p> <p>We demonstrate a high efficient frequency tripling configuration of Ti: sapphire amplifier system for wavelength-tunable ultrafast ultraviolet laser <span class="hlt">generation</span>. A new nonlinear crystal Ba1-xB2-y-zO4SixAlyGaz and a type-II phase-matched β-BaB2O4 crystal are employed for the second and the third <span class="hlt">harmonic</span> <span class="hlt">generation</span>, respectively. Significant improvement in conversion efficiency of frequency tripling is achieved by using a 65°-cut, 3-mm-long β-BaB2O4 crystal as the collinear group velocity compensation plate. Tunable ultraviolet pulse within the wavelength range from 256.7 to 276.7 nm have been produced, with a maximum average power of 212 mW, corresponding to a conversion efficiency of 8.48% for the third <span class="hlt">harmonic</span> <span class="hlt">generation</span> with 2.5 W fundamental power. The maximum pulse energy of the third <span class="hlt">harmonic</span> is up to 0.21 mJ and it is estimated that the peak power is above 1 GW at 266.7 nm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1234578','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1234578"><span id="translatedtitle">The Ultraviolet Surprise. Efficient Soft X-Ray High <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> in Multiply-Ionized Plasmas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Popmintchev, Dimitar; Hernandez-Garcia, Carlos; Dollar, Franklin; Mancuso, Christopher; Perez-Hernandez, Jose A.; Chen, Ming-Chang; Hankla, Amelia; Gao, Xiaohui; Shim, Bonggu; Gaeta, Alexander L.; Tarazkar, Maryam; Romanov, Dmitri A.; Levis, Robert J.; Gaffney, Jim A.; Foord, Mark; Libby, Stephen B.; Jaron-Becker, Agnieskzka; Becker, Andreas; Plaja, Luis; Muranane, Margaret M.; Kapteyn, Henry C.; Popmintchev, Tenio</p> <p>2015-12-04</p> <p>High-<span class="hlt">harmonic</span> <span class="hlt">generation</span> is a universal response of matter to strong femtosecond laser fields, coherently upconverting light to much shorter wavelengths. Optimizing the conversion of laser light into soft x-rays typically demands a trade-off between two competing factors. Reduced quantum diffusion of the radiating electron wave function results in emission from each species which is highest when a short-wavelength ultraviolet driving laser is used. But, phase matching—the constructive addition of x-ray waves from a large number of atoms—favors longer-wavelength mid-infrared lasers. We identified a regime of high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> driven by 40-cycle ultraviolet lasers in waveguides that can <span class="hlt">generate</span> bright beams in the soft x-ray region of the spectrum, up to photon energies of 280 electron volts. Surprisingly, the high ultraviolet refractive indices of both neutral atoms and ions enabled effective phase matching, even in a multiply ionized plasma. We observed <span class="hlt">harmonics</span> with very narrow linewidths, while calculations show that the x-rays emerge as nearly time-bandwidth–limited pulse trains of ~100 attoseconds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1234578-ultraviolet-surprise-efficient-soft-ray-high-harmonic-generation-multiply-ionized-plasmas','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1234578-ultraviolet-surprise-efficient-soft-ray-high-harmonic-generation-multiply-ionized-plasmas"><span id="translatedtitle">The Ultraviolet Surprise. Efficient Soft X-Ray High <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> in Multiply-Ionized Plasmas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Popmintchev, Dimitar; Hernandez-Garcia, Carlos; Dollar, Franklin; Mancuso, Christopher; Perez-Hernandez, Jose A.; Chen, Ming-Chang; Hankla, Amelia; Gao, Xiaohui; Shim, Bonggu; Gaeta, Alexander L.; et al</p> <p>2015-12-04</p> <p>High-<span class="hlt">harmonic</span> <span class="hlt">generation</span> is a universal response of matter to strong femtosecond laser fields, coherently upconverting light to much shorter wavelengths. Optimizing the conversion of laser light into soft x-rays typically demands a trade-off between two competing factors. Reduced quantum diffusion of the radiating electron wave function results in emission from each species which is highest when a short-wavelength ultraviolet driving laser is used. But, phase matching—the constructive addition of x-ray waves from a large number of atoms—favors longer-wavelength mid-infrared lasers. We identified a regime of high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> driven by 40-cycle ultraviolet lasers in waveguides that can <span class="hlt">generate</span> bright beams inmore » the soft x-ray region of the spectrum, up to photon energies of 280 electron volts. Surprisingly, the high ultraviolet refractive indices of both neutral atoms and ions enabled effective phase matching, even in a multiply ionized plasma. We observed <span class="hlt">harmonics</span> with very narrow linewidths, while calculations show that the x-rays emerge as nearly time-bandwidth–limited pulse trains of ~100 attoseconds.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvA..94a3417X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvA..94a3417X"><span id="translatedtitle">Correspondence of below-threshold high-order-<span class="hlt">harmonic</span> <span class="hlt">generation</span> and frustrated tunneling ionization</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiong, Wei-Hao; Xiao, Xiang-Ru; Peng, Liang-You; Gong, Qihuang</p> <p>2016-07-01</p> <p>Among many of the nonlinear phenomena induced by strong laser pulses, two of the important processes are the <span class="hlt">harmonic</span> <span class="hlt">generation</span> and the creation of neutral atoms in the Rydberg states. We carry out a joint study of the below-threshold high-order-<span class="hlt">harmonic</span> (BTH) <span class="hlt">generation</span> and the production of low-lying Rydberg atoms driven by an intense few-cycle midinfrared laser pulse. Our results are based on the numerical solution to the three-dimensional time-dependent Schrödinger equation within the single active electron approximation and a semiclassical simulation. The yields of BTH and low-lying Rydberg atoms are found to have a similar carrier envelope phase dependence. We find that both processes can be faithfully described semiclassically in the deep tunneling regime. The trajectory analysis shows that these two processes share the same series of trajectories and can be simultaneously manipulated by the driving pulse shape. Our finding bridges the below-threshold high-order-<span class="hlt">harmonic</span> <span class="hlt">generation</span> and the frustrated tunneling ionization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27304282','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27304282"><span id="translatedtitle">Background-free electric field-induced second <span class="hlt">harmonic</span> <span class="hlt">generation</span> with interdigitated combs of electrodes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jašinskas, Vidmantas; Gedvilas, Mindaugas; Račiukaitis, Gediminas; Gulbinas, Vidmantas</p> <p>2016-06-15</p> <p>The electric field-induced second <span class="hlt">harmonic</span> (EFISH) <span class="hlt">generation</span> is a powerful tool for the investigation of optical nonlinearities, material polarization, internal electric fields, and other properties of photonic materials and devices. A conventional <span class="hlt">generation</span> of the second <span class="hlt">harmonics</span> (SH) in materials with the disturbed centrosymmetry causes a field-independent background to EFISH and limits its applications. Here we suggest and analyze the application of the interdigitated combs of electrodes for EFISH <span class="hlt">generation</span> in thin films. Interdigitated electrodes form an optical transmission amplitude diffraction grating. Phase matching of the EFISH radiation creates unusual diffraction fringes with the zero intensity along the zeroth order direction and with the diffraction angles different from diffraction angles of incident fundamental laser radiation and its second <span class="hlt">harmonics</span>. It enables a simple geometrical separation of the EFISH signal from a conventional SH background, simplifies the sample preparation, and provides additional experimental possibilities. We demonstrate applicability of the suggested technique for characterization of submicrometer thickness organic films of transparent and resonantly interacting polymers and of their mixtures. PMID:27304282</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22300162','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22300162"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> by propagation of a p-polarized obliquely incident laser beam in underdense plasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jha, Pallavi; Agrawal, Ekta</p> <p>2014-05-15</p> <p>An analytical study of second <span class="hlt">harmonic</span> <span class="hlt">generation</span> due to interaction an intense, p-polarized laser beam propagating obliquely in homogeneous underdense plasma, in the mildly relativistic regime, has been presented. The efficiency of the second <span class="hlt">harmonic</span> radiation as well as its detuning length has been obtained and their variation with the angle of incidence is analyzed. It is shown that, for a given plasma electron density, the second <span class="hlt">harmonic</span> efficiency increases with the angle of incidence while the detuning length decreases. The second <span class="hlt">harmonic</span> amplitude vanishes at normal incidence of the laser beam.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/992921','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/992921"><span id="translatedtitle">First Demonstration of the Echo-Enabled <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> Technique for Short-Wavelength Seeded Free Electron Lasers</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Xiang, D.; Colby, E.; Dunning, M.; Gilevich, S.; Hast, C.; Jobe, K.; McCormick, D.; Nelson, J.; Raubenheimer, T.O.; Soong, K.; Stupakov, G.; Szalata, Z.; Walz, D.; Weathersby, S.; Woodley, M.; Pernet, P.-L.; /Ecole Polytechnique, Lausanne</p> <p>2010-08-25</p> <p>We report the first experimental demonstration of the echo-enabled <span class="hlt">harmonic</span> <span class="hlt">generation</span> (EEHG) technique which holds great promise for <span class="hlt">generation</span> of high power, fully coherent short-wavelength radiation. In this experiment, coherent radiation at the 3rd and 4th <span class="hlt">harmonic</span> of the second seed laser is <span class="hlt">generated</span> from the so-called beam echo effect. The experiment confirms the physics behind this technique and paves the way for applying the EEHG technique for seeded x-ray free electron lasers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016QuEle..46..338F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016QuEle..46..338F"><span id="translatedtitle">X-ray spectral diagnostics of laser <span class="hlt">harmonic</span> <span class="hlt">generation</span> in the interaction of relativistic femtosecond laser pulses with clusters</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Faenov, A. Ya; Oks, E.; Dalimier, E.; Skobelev, I. Yu; Pikuz, S. A.; Pikuz, T. A.; Zhvaniya, I. A.; Fukuda, Y.; Andreev, A.; Koga, J.; Sakaki, H.; Kotaki, H.; Pirozhkov, A. S.; Hayashi, Y.; Kawachi, T.; Kando, M.; Kondo, K.; Zhidkov, A. G.; Kodama, R.</p> <p>2016-04-01</p> <p>It is shown that the production of X-ray emission spectra in the interaction of high-intensity laser radiation with cluster targets may be affected by the bichromatic oscillating electric field arising from the <span class="hlt">generation</span> of the second <span class="hlt">harmonic</span> of laser radiation. A technique is proposed for diagnosing <span class="hlt">harmonic</span> <span class="hlt">generation</span> in laser - cluster interactions using the spectral line profiles of multiply charged helium ions. The efficiency of second <span class="hlt">harmonic</span> <span class="hlt">generation</span> at a laser intensity of 3 × 1018 W cm-2 is shown to amount to about 2%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvA..94a3856A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvA..94a3856A"><span id="translatedtitle">Enhanced high-order-<span class="hlt">harmonic</span> <span class="hlt">generation</span> and wave mixing via two-color multiphoton excitation of atoms and molecules</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Avetissian, H. K.; Avchyan, B. R.; Mkrtchian, G. F.</p> <p>2016-07-01</p> <p>We consider <span class="hlt">harmonics</span> <span class="hlt">generation</span> and wave mixing by two-color multiphoton resonant excitation of three-level atoms and molecules in strong laser fields. The coherent part of the spectra corresponding to multicolor <span class="hlt">harmonics</span> <span class="hlt">generation</span> is investigated. The obtained analytical results on the basis of a generalized rotating wave approximation are in a good agreement with numerical calculations. The results applied to the hydrogen atoms and homonuclear diatomic molecular ions show that one can achieve efficient <span class="hlt">generation</span> of moderately high multicolor <span class="hlt">harmonics</span> via multiphoton resonant excitation by appropriate laser pulses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1041347','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1041347"><span id="translatedtitle">Life Cycle Greenhouse Gas Emissions of Coal-Fired Electricity <span class="hlt">Generation</span>: Systematic Review and <span class="hlt">Harmonization</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Whitaker, M.; Heath, G. A.; O'Donoughue, P.; Vorum, M.</p> <p>2012-04-01</p> <p>This systematic review and <span class="hlt">harmonization</span> of life cycle assessments (LCAs) of utility-scale coal-fired electricity <span class="hlt">generation</span> systems focuses on reducing variability and clarifying central tendencies in estimates of life cycle greenhouse gas (GHG) emissions. Screening 270 references for quality LCA methods, transparency, and completeness yielded 53 that reported 164 estimates of life cycle GHG emissions. These estimates for subcritical pulverized, integrated gasification combined cycle, fluidized bed, and supercritical pulverized coal combustion technologies vary from 675 to 1,689 grams CO{sub 2}-equivalent per kilowatt-hour (g CO{sub 2}-eq/kWh) (interquartile range [IQR]= 890-1,130 g CO{sub 2}-eq/kWh; median = 1,001) leading to confusion over reasonable estimates of life cycle GHG emissions from coal-fired electricity <span class="hlt">generation</span>. By adjusting published estimates to common gross system boundaries and consistent values for key operational input parameters (most importantly, combustion carbon dioxide emission factor [CEF]), the meta-analytical process called <span class="hlt">harmonization</span> clarifies the existing literature in ways useful for decision makers and analysts by significantly reducing the variability of estimates ({approx}53% in IQR magnitude) while maintaining a nearly constant central tendency ({approx}2.2% in median). Life cycle GHG emissions of a specific power plant depend on many factors and can differ from the generic estimates <span class="hlt">generated</span> by the <span class="hlt">harmonization</span> approach, but the tightness of distribution of <span class="hlt">harmonized</span> estimates across several key coal combustion technologies implies, for some purposes, first-order estimates of life cycle GHG emissions could be based on knowledge of the technology type, coal mine emissions, thermal efficiency, and CEF alone without requiring full LCAs. Areas where new research is necessary to ensure accuracy are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004IJTIA.124.1173S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004IJTIA.124.1173S"><span id="translatedtitle">Compensation for <span class="hlt">Harmonic</span> Currents and Reactive Power in Wind Power <span class="hlt">Generation</span> System using PWM Inverter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shinohara, Katsuji; Shinhatsubo, Kurato; Iimori, Kenichi; Yamamoto, Kichiro; Saruban, Takamichi; Yamaemori, Takahiro</p> <p></p> <p>In recent year, consciousness of environmental problems is enhancing, and the price of the electric power purchased by an electric power company is established expensive for the power plant utilizing the natural energy. So, the introduction of the wind power <span class="hlt">generation</span> is promoted in Japan. Generally, squirrel-cage induction machines are widely used as a <span class="hlt">generator</span> in wind power <span class="hlt">generation</span> system because of its small size, lightweight and low-cost. However, the induction machines do not have a source of excitation. Thus, it causes the inrush currents and the instantaneous voltage drop when the <span class="hlt">generator</span> is directly connected to a power grid. To reduce the inrush currents, an AC power regulator is used. Wind power <span class="hlt">generations</span> are frequently connected to and disconnected from the power grid. However, when the inrush currents are reduced, <span class="hlt">harmonic</span> currents are caused by phase control of the AC power regulator. And the phase control of AC power regulator cannot control the power factor. Therefore, we propose the use of the AC power regulator to compensate for the <span class="hlt">harmonic</span> currents and reactive power in the wind power <span class="hlt">generation</span> system, and demonstrate the validity of its system by simulated and experimental results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OptCo.370....6G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OptCo.370....6G"><span id="translatedtitle">Ablation of boron carbide for high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> of ultrafast pulses in laser-produced plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ganeev, R. A.; Suzuki, M.; Kuroda, H.</p> <p>2016-07-01</p> <p>We demonstrate the <span class="hlt">generation</span> of <span class="hlt">harmonics</span> up to the 27th order (λ=29.9 nm) of 806 nm radiation in the boron carbide plasma. We analyze the advantages and disadvantages of this target compared with the ingredients comprising B4C (solid boron and graphite) by studying the plasma emission and <span class="hlt">harmonic</span> spectra from three species. We compare different schemes of the two-color pump of B4C plasma, particularly using the second <span class="hlt">harmonics</span> of 806 nm laser and optical parametric amplifier (1310 nm) as the assistant fields, as well as demonstrate the sum and difference frequency <span class="hlt">generation</span> using the mixture of the wavelengths of two laser sources. These studies showed the advantages of the two-color pump of B4C plasma leading to the stable <span class="hlt">harmonic</span> <span class="hlt">generation</span> and the growth of <span class="hlt">harmonic</span> conversion efficiency. We also show that the coincidence of <span class="hlt">harmonic</span> and plasma emission wavelengths in most cases does not cause the enhancement or decrease of the conversion efficiency of this <span class="hlt">harmonic</span>. Our spatial characterization of <span class="hlt">harmonics</span> shows their on-axis modification depending on the conditions of frequency conversion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OptLT..83..177P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OptLT..83..177P"><span id="translatedtitle">[INVITED] Laser <span class="hlt">generation</span> and detection of ultrafast shear <span class="hlt">acoustic</span> waves in solids and liquids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pezeril, Thomas</p> <p>2016-09-01</p> <p>The aim of this article is to provide an overview of the up-to-date findings related to ultrafast shear <span class="hlt">acoustic</span> waves. Recent progress obtained for the laser <span class="hlt">generation</span> and detection of picosecond shear <span class="hlt">acoustic</span> waves in solids and liquids is reviewed. Examples in which the transverse isotropic symmetry of the sample structure is broken in order to permit shear <span class="hlt">acoustic</span> wave <span class="hlt">generation</span> through sudden laser heating are described in detail. Alternative photo-induced mechanisms for ultrafast shear <span class="hlt">acoustic</span> <span class="hlt">generation</span> in metals, semiconductors, insulators, magnetostrictive, piezoelectric and electrostrictive materials are reviewed as well. With reference to key experiments, an all-optical technique employed to probe longitudinal and shear structural dynamics in the GHz frequency range in ultra-thin liquid films is described. This technique, based on specific ultrafast shear <span class="hlt">acoustic</span> transducers, has opened new perspectives that will be discussed for ultrafast shear <span class="hlt">acoustic</span> probing of viscoelastic liquids at the nanometer scale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27331867','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27331867"><span id="translatedtitle">Enhanced Third <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> in Single Germanium Nanodisks Excited at the Anapole Mode.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Grinblat, Gustavo; Li, Yi; Nielsen, Michael P; Oulton, Rupert F; Maier, Stefan A</p> <p>2016-07-13</p> <p>We present an all-dielectric germanium nanosystem exhibiting a strong third order nonlinear response and efficient third <span class="hlt">harmonic</span> <span class="hlt">generation</span> in the optical regime. A thin germanium nanodisk shows a pronounced valley in its scattering cross section at the dark anapole mode, while the electric field energy inside the disk is maximized due to high confinement within the dielectric. We investigate the dependence of the third <span class="hlt">harmonic</span> signal on disk size and pump wavelength to reveal the nature of the anapole mode. Each germanium nanodisk <span class="hlt">generates</span> a high effective third order susceptibility of χ((3)) = 4.3 × 10(-9) esu, corresponding to an associated third <span class="hlt">harmonic</span> conversion efficiency of 0.0001% at an excitation wavelength of 1650 nm, which is 4 orders of magnitude greater than the case of an unstructured germanium reference film. Furthermore, the nonlinear conversion via the anapole mode outperforms that via the radiative dipolar resonances by about 1 order of magnitude, which is consistent with our numerical simulations. These findings open new possibilities for the optimization of upconversion processes on the nanoscale through the appropriate engineering of suitable dielectric materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27433989','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27433989"><span id="translatedtitle">The Interplay of Symmetry and Scattering Phase in Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> from Gold Nanoantennas.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gennaro, Sylvain D; Rahmani, Mohsen; Giannini, Vincenzo; Aouani, Heykel; Sidiropoulos, Themistoklis P H; Navarro-Cía, Miguel; Maier, Stefan A; Oulton, Rupert F</p> <p>2016-08-10</p> <p>Nonlinear phenomena are central to modern photonics but, being inherently weak, typically require gradual accumulation over several millimeters. For example, second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) is typically achieved in thick transparent nonlinear crystals by phase-matching energy exchange between light at initial, ω, and final, 2ω, frequencies. Recently, metamaterials imbued with artificial nonlinearity from their constituent nanoantennas have <span class="hlt">generated</span> excitement by opening the possibility of wavelength-scale nonlinear optics. However, the selection rules of SHG typically prevent dipole emission from simple nanoantennas, which has led to much discussion concerning the best geometries, for example, those breaking centro-symmetry or incorporating resonances at multiple <span class="hlt">harmonics</span>. In this work, we explore the use of both nanoantenna symmetry and multiple <span class="hlt">harmonics</span> to control the strength, polarization and radiation pattern of SHG from a variety of antenna configurations incorporating simple resonant elements tuned to light at both ω and 2ω. We use a microscopic description of the scattering strength and phases of these constituent particles, determined by their relative positions, to accurately predict the SHG radiation observed in our experiments. We find that the 2ω particles radiate dipolar SHG by near-field coupling to the ω particle, which radiates SHG as a quadrupole. Consequently, strong linearly polarized dipolar SHG is only possible for noncentro-symmetric antennas that also minimize interference between their dipolar and quadrupolar responses. Metamaterials with such intra-antenna phase and polarization control could enable compact nonlinear photonic nanotechnologies.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27433989','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27433989"><span id="translatedtitle">The Interplay of Symmetry and Scattering Phase in Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> from Gold Nanoantennas.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gennaro, Sylvain D; Rahmani, Mohsen; Giannini, Vincenzo; Aouani, Heykel; Sidiropoulos, Themistoklis P H; Navarro-Cía, Miguel; Maier, Stefan A; Oulton, Rupert F</p> <p>2016-08-10</p> <p>Nonlinear phenomena are central to modern photonics but, being inherently weak, typically require gradual accumulation over several millimeters. For example, second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) is typically achieved in thick transparent nonlinear crystals by phase-matching energy exchange between light at initial, ω, and final, 2ω, frequencies. Recently, metamaterials imbued with artificial nonlinearity from their constituent nanoantennas have <span class="hlt">generated</span> excitement by opening the possibility of wavelength-scale nonlinear optics. However, the selection rules of SHG typically prevent dipole emission from simple nanoantennas, which has led to much discussion concerning the best geometries, for example, those breaking centro-symmetry or incorporating resonances at multiple <span class="hlt">harmonics</span>. In this work, we explore the use of both nanoantenna symmetry and multiple <span class="hlt">harmonics</span> to control the strength, polarization and radiation pattern of SHG from a variety of antenna configurations incorporating simple resonant elements tuned to light at both ω and 2ω. We use a microscopic description of the scattering strength and phases of these constituent particles, determined by their relative positions, to accurately predict the SHG radiation observed in our experiments. We find that the 2ω particles radiate dipolar SHG by near-field coupling to the ω particle, which radiates SHG as a quadrupole. Consequently, strong linearly polarized dipolar SHG is only possible for noncentro-symmetric antennas that also minimize interference between their dipolar and quadrupolar responses. Metamaterials with such intra-antenna phase and polarization control could enable compact nonlinear photonic nanotechnologies. PMID:27433989</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27331867','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27331867"><span id="translatedtitle">Enhanced Third <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> in Single Germanium Nanodisks Excited at the Anapole Mode.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Grinblat, Gustavo; Li, Yi; Nielsen, Michael P; Oulton, Rupert F; Maier, Stefan A</p> <p>2016-07-13</p> <p>We present an all-dielectric germanium nanosystem exhibiting a strong third order nonlinear response and efficient third <span class="hlt">harmonic</span> <span class="hlt">generation</span> in the optical regime. A thin germanium nanodisk shows a pronounced valley in its scattering cross section at the dark anapole mode, while the electric field energy inside the disk is maximized due to high confinement within the dielectric. We investigate the dependence of the third <span class="hlt">harmonic</span> signal on disk size and pump wavelength to reveal the nature of the anapole mode. Each germanium nanodisk <span class="hlt">generates</span> a high effective third order susceptibility of χ((3)) = 4.3 × 10(-9) esu, corresponding to an associated third <span class="hlt">harmonic</span> conversion efficiency of 0.0001% at an excitation wavelength of 1650 nm, which is 4 orders of magnitude greater than the case of an unstructured germanium reference film. Furthermore, the nonlinear conversion via the anapole mode outperforms that via the radiative dipolar resonances by about 1 order of magnitude, which is consistent with our numerical simulations. These findings open new possibilities for the optimization of upconversion processes on the nanoscale through the appropriate engineering of suitable dielectric materials. PMID:27331867</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22909407','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22909407"><span id="translatedtitle">An azo-bridged ferroelectric liquid crystal with highly enhanced second and third <span class="hlt">harmonic</span> <span class="hlt">generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Yongqiang; Ortega, Josu; Baumeister, Ute; Folcia, César L; Sanz-Enguita, Gerardo; Walker, Christopher; Rodriguez-Conde, Sofía; Etxebarria, Jesus; O'Callaghan, Michael J; More, Kundalika</p> <p>2012-10-01</p> <p>A laterally azo-bridged trimer ferroelectric liquid crystal (FLC) incorporating a strong chromophore along its polar axis was synthesized and characterized by polarized-light optical microscopy, differential scanning calorimetry, two-dimensional X-ray diffraction analysis, electro-optical measurements, and nonlinear optical (NLO) investigations. This mesogen exhibits a thermodynamically stable enantiotropic SmC* phase and a bistable ferroelectric switching in a surface stabilized cell with bookshelf geometry. It gives the resonance-enhanced d(22) coefficient of 28 pm V(-1) (λ = 1.369 μm) for second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG), the largest NLO susceptibility reported to date for all FLCs. At the same wavelength, a new type of helicoidal phase matching assisted by the helical SmC* structure was identified. When the second <span class="hlt">harmonic</span> wavelength of 780 nm is far away from the resonance wavelength (λ(max) = 572 nm), the d(22) coefficient is reduced to 6.8 pm V(-1) (λ = 1.56 μm). In addition to a strong SHG activity, the trimer also shows a strong third <span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) with an estimated third-order nonlinear susceptibility of χ((3)) = ~3 × 10(-11) esu (λ = 1.56 μm), among the largest χ((3)) value reported from THG measurements for liquid crystals. This work enables viable applications of FLCs in nonlinear optics and offers an innovative approach to develop new FLCs with larger NLO strength. PMID:22909407</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014SPIE.9162E..23W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014SPIE.9162E..23W&link_type=ABSTRACT"><span id="translatedtitle">Third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> enhancement in polymer-dispersed liquid crystal grating</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wicharn, S.; Buranasiri, P.</p> <p>2014-09-01</p> <p>In this paper, the enhancement of third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in one-dimensional periodic grating structure with lowindex contrast, which is produced by holographic illuminated liquid crystal droplets and called polymer-dispersed liquid crystal grating, with near-infrared pumping has been demonstrated. The observed enhancement process is theoretically explained and modeled with a multi-scale perturbation analysis and split-step Fourier transform technique, respectively. We show that the third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> has been enhanced by setting the fundamental frequency wavelength to the long-wavelength band-edge of the first photonic band-gap of this periodic structure and satisfying band-edge phasematched condition. The numerical results show that a dramatic enhancement of the third-<span class="hlt">harmonic</span> field is observed near the long-wavelength band-edge of the second photonic band-gap. Furthermore, the conversion efficiency of thirdharmonic field of forward-propagating direction is more than of backward-propagating direction by a factor of 600.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22252891','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22252891"><span id="translatedtitle">Advanced properties of extended plasmas for efficient high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ganeev, R. A.; Suzuki, M.; Kuroda, H.</p> <p>2014-05-15</p> <p>We demonstrate the advanced properties of extended plasma plumes (5 mm) for efficient <span class="hlt">harmonic</span> <span class="hlt">generation</span> of laser radiation compared with the short lengths of plasmas (∼0.3–0.5 mm) used in previous studies. The <span class="hlt">harmonic</span> conversion efficiency quadratically increased with the growth of plasma length. The studies of this process along the whole extreme ultraviolet range using the long plasma jets produced on various metal surfaces, particularly including the resonance-enhanced laser frequency conversion and two-color pump, are presented. Such plasmas could be used for the quasi-phase matching experiments by proper modulation of the spatial characteristics of extended ablating area and formation of separated plasma jets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25415907','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25415907"><span id="translatedtitle">Probing nuclear motion by frequency modulation of molecular high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bian, Xue-Bin; Bandrauk, André D</p> <p>2014-11-01</p> <p>Molecular high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> (MHOHG) in a non-Born-Oppenheimer treatment of H(2)(+), D(2)(+), is investigated by numerical simulations of the corresponding time-dependent Schrödinger equations in full dimensions. As opposed to previous studies on amplitude modulation of intracycle dynamics in MHOHG, we demonstrate redshifts as frequency modulation (FM) of intercycle dynamics in MHOHG. The FM is induced by nuclear motion using intense laser pulses. Compared to fixed-nuclei approximations, the intensity of MHOHG is much higher due to the dependence of enhanced ionization on the internuclear distance. The width and symmetry of the spectrum of each <span class="hlt">harmonic</span> in MHOHG encode rich information on the dissociation process of molecules at the rising and falling parts of the laser pulses, which can be used to retrieve the nuclear dynamics. Isotope effects are studied to confirm the FM mechanism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApPhB.116..121H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApPhB.116..121H"><span id="translatedtitle">Temporal coherence of high-order <span class="hlt">harmonics</span> <span class="hlt">generated</span> at solid surfaces</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hemmers, D.; Behmke, M.; Karsch, S.; Keyling, J.; Major, Z.; Stelzmann, C.; Pretzler, G.</p> <p>2014-07-01</p> <p>We present interferometric measurements of the temporal coherence of high-order <span class="hlt">harmonics</span> <span class="hlt">generated</span> by reflection of a titanium sapphire laser off a solid surface. It is found that the coherence length of the <span class="hlt">harmonic</span> emission is significantly reduced compared with the bandwidth limited case. To identify the responsible mechanism, the acquired data were analyzed by means of particle-in-cell simulations, whose results show good agreement between the calculated spectra and the measured coherence times. We show that the observed broadening can be understood consistently by the occurrence of a Doppler shift induced by the moving plasma surface, which is dented by the radiation pressure of the laser pulse. In this case, this Doppler effect would also lead to positive chirp of the emitted radiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20798251','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20798251"><span id="translatedtitle"><span class="hlt">Generation</span> and Detection of Higher <span class="hlt">Harmonics</span> in Rayleigh Waves Using Laser Ultrasound</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Herrmann, Jan; Jacobs, Laurence J.; Qu Jianmin; Kim, Jin-Yeon</p> <p>2006-03-06</p> <p>This research studies higher <span class="hlt">harmonics</span> of Rayleigh surface waves propagating in nickel base superalloys. Rayleigh waves are used because they carry most of the energy and travel along the surface of a specimen where fatigue damage is typically initiated. The energy concentration near the free surface leads to stronger nonlinear effects compared to bulk waves. An ultrasonic piezoelectric transducer together with a plastic wedge is used for the experimental <span class="hlt">generation</span> of the Rayleigh wave. The detection system consists of a laser heterodyne interferometer. Measurements are performed to detect the fundamental wave as well as the second <span class="hlt">harmonic</span>. The amplitude ratio is related to the nonlinearity parameter {beta} which is typically used to describe changes in microstructure and investigate fatigue damage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17930952','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17930952"><span id="translatedtitle">Bright multi-keV <span class="hlt">harmonic</span> <span class="hlt">generation</span> from relativistically oscillating plasma surfaces.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dromey, B; Kar, S; Bellei, C; Carroll, D C; Clarke, R J; Green, J S; Kneip, S; Markey, K; Nagel, S R; Simpson, P T; Willingale, L; McKenna, P; Neely, D; Najmudin, Z; Krushelnick, K; Norreys, P A; Zepf, M</p> <p>2007-08-24</p> <p>The first evidence of x-ray <span class="hlt">harmonic</span> radiation extending to 3.3 A, 3.8 keV (order n>3200) from petawatt class laser-solid interactions is presented, exhibiting relativistic limit efficiency scaling (eta approximately n{-2.5}-n{-3}) at multi-keV energies. This scaling holds up to a maximum order, n{RO} approximately 8{1/2}gamma;{3}, where gamma is the relativistic Lorentz factor, above which the first evidence of an intensity dependent efficiency rollover is observed. The coherent nature of the <span class="hlt">generated</span> <span class="hlt">harmonics</span> is demonstrated by the highly directional beamed emission, which for photon energy hnu>1 keV is found to be into a cone angle approximately 4 degrees , significantly less than that of the incident laser cone (20 degrees ).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25837108','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25837108"><span id="translatedtitle">In-phased second <span class="hlt">harmonic</span> wave array <span class="hlt">generation</span> with intra-Talbot-cavity frequency-doubling.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hirosawa, Kenichi; Shohda, Fumio; Yanagisawa, Takayuki; Kannari, Fumihiko</p> <p>2015-03-23</p> <p>The Talbot cavity is one promising method to synchronize the phase of a laser array. However, it does not achieve the lowest array mode with the same phase but the highest array mode with the anti-phase between every two adjacent lasers, which is called out-phase locking. Consequently, their far-field images exhibit 2-peak profiles. We propose intra-Talbot-cavity frequency-doubling. By placing a nonlinear crystal in a Talbot cavity, the Talbot cavity <span class="hlt">generates</span> an out-phased fundamental wave array, which is converted into an in-phase-locked second <span class="hlt">harmonic</span> wave array at the nonlinear crystal. We demonstrate numerical calculations and experiments on intra-Talbot-cavity frequency-doubling and obtain an in-phase-locked second <span class="hlt">harmonic</span> wave array for a Nd:YVO₄ array laser.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22113700','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22113700"><span id="translatedtitle">Second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> efficiency for multifrequency ytterbium-doped fibre laser radiation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Politko, M O; Kablukov, S I; Nemov, I N; Babin, Sergei A</p> <p>2013-02-28</p> <p>The second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) efficiency for cw Yb-doped fibre laser radiation, which is characterised by many longitudinal modes with random phases, is compared with the SHG efficiency for amplified single-frequency Nd : YAG laser radiation in ppLN and KTP crystals, characterised by the type-I and type-IIphase matching, respectively. It is shown that the conversion efficiency into the second <span class="hlt">harmonic</span> in the multifrequency regime for both crystals is higher by a factor of about 1.6, a value close to the calculated enhancement (2 for the Gaussian mode statistics). This difference is explained by possible deviation of the statistics of the Yb-doped fibre laser radiation from Gaussian, which is confirmed by measurements of the laser temporal dynamics. (laser optics 2012)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014SPIE.8948E..0VL&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014SPIE.8948E..0VL&link_type=ABSTRACT"><span id="translatedtitle">Simultaneous stimulated Raman scattering and higher <span class="hlt">harmonic</span> <span class="hlt">generation</span> imaging for liver disease diagnosis without labeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, Jian; Wang, Zi; Zheng, Wei; Huang, Zhiwei</p> <p>2014-02-01</p> <p>Nonlinear optical microscopy (e.g., higher <span class="hlt">harmonic</span> (second-/third- <span class="hlt">harmonic</span>) <span class="hlt">generation</span> (HHG), simulated Raman scattering (SRS)) has high diagnostic sensitivity and chemical specificity, making it a promising tool for label-free tissue and cell imaging. In this work, we report a development of a simultaneous SRS and HHG imaging technique for characterization of liver disease in a bile-duct-ligation rat-modal. HHG visualizes collagens formation and reveals the cell morphologic changes associated with liver fibrosis; whereas SRS identifies the distributions of hepatic fat cells formed in steatosis liver tissue. This work shows that the co-registration of SRS and HHG images can be an effective means for label-free diagnosis and characterization of liver steatosis/fibrosis at the cellular and molecular levels.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4128108','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4128108"><span id="translatedtitle"><span class="hlt">Harmonization</span> of initial estimates of shale gas life cycle greenhouse gas emissions for electric power <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Heath, Garvin A.; O’Donoughue, Patrick; Arent, Douglas J.; Bazilian, Morgan</p> <p>2014-01-01</p> <p>Recent technological advances in the recovery of unconventional natural gas, particularly shale gas, have served to dramatically increase domestic production and reserve estimates for the United States and internationally. This trend has led to lowered prices and increased scrutiny on production practices. Questions have been raised as to how greenhouse gas (GHG) emissions from the life cycle of shale gas production and use compares with that of conventionally produced natural gas or other fuel sources such as coal. Recent literature has come to different conclusions on this point, largely due to differing assumptions, comparison baselines, and system boundaries. Through a meta-analytical procedure we call <span class="hlt">harmonization</span>, we develop robust, analytically consistent, and updated comparisons of estimates of life cycle GHG emissions for electricity produced from shale gas, conventionally produced natural gas, and coal. On a per-unit electrical output basis, <span class="hlt">harmonization</span> reveals that median estimates of GHG emissions from shale gas-<span class="hlt">generated</span> electricity are similar to those for conventional natural gas, with both approximately half that of the central tendency of coal. Sensitivity analysis on the <span class="hlt">harmonized</span> estimates indicates that assumptions regarding liquids unloading and estimated ultimate recovery (EUR) of wells have the greatest influence on life cycle GHG emissions, whereby shale gas life cycle GHG emissions could approach the range of best-performing coal-fired <span class="hlt">generation</span> under certain scenarios. Despite clarification of published estimates through <span class="hlt">harmonization</span>, these initial assessments should be confirmed through methane emissions measurements at components and in the atmosphere and through better characterization of EUR and practices. PMID:25049378</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25049378','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25049378"><span id="translatedtitle"><span class="hlt">Harmonization</span> of initial estimates of shale gas life cycle greenhouse gas emissions for electric power <span class="hlt">generation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Heath, Garvin A; O'Donoughue, Patrick; Arent, Douglas J; Bazilian, Morgan</p> <p>2014-08-01</p> <p>Recent technological advances in the recovery of unconventional natural gas, particularly shale gas, have served to dramatically increase domestic production and reserve estimates for the United States and internationally. This trend has led to lowered prices and increased scrutiny on production practices. Questions have been raised as to how greenhouse gas (GHG) emissions from the life cycle of shale gas production and use compares with that of conventionally produced natural gas or other fuel sources such as coal. Recent literature has come to different conclusions on this point, largely due to differing assumptions, comparison baselines, and system boundaries. Through a meta-analytical procedure we call <span class="hlt">harmonization</span>, we develop robust, analytically consistent, and updated comparisons of estimates of life cycle GHG emissions for electricity produced from shale gas, conventionally produced natural gas, and coal. On a per-unit electrical output basis, <span class="hlt">harmonization</span> reveals that median estimates of GHG emissions from shale gas-<span class="hlt">generated</span> electricity are similar to those for conventional natural gas, with both approximately half that of the central tendency of coal. Sensitivity analysis on the <span class="hlt">harmonized</span> estimates indicates that assumptions regarding liquids unloading and estimated ultimate recovery (EUR) of wells have the greatest influence on life cycle GHG emissions, whereby shale gas life cycle GHG emissions could approach the range of best-performing coal-fired <span class="hlt">generation</span> under certain scenarios. Despite clarification of published estimates through <span class="hlt">harmonization</span>, these initial assessments should be confirmed through methane emissions measurements at components and in the atmosphere and through better characterization of EUR and practices. PMID:25049378</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24789577','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24789577"><span id="translatedtitle">Switchable dielectric, piezoelectric, and second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> bistability in a new improper ferroelectric above room temperature.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Yi; Ye, Heng-Yun; Cai, Hong-Ling; Fu, Da-Wei; Ye, Qiong; Zhang, Wen; Zhou, Qionghua; Wang, Jinlan; Yuan, Guo-Liang; Xiong, Ren-Gen</p> <p>2014-07-01</p> <p>Imidazolium periodate (IPI) is found to be an improper ferroelectric. It shows bistable properties simultaneously in three channels of dielectricity, piezoelectricity, and second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> within the temperature window 300-310 K. PMID:24789577</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21361915','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21361915"><span id="translatedtitle">Influence of C{sub 60} morphology on high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> enhancement in fullerene-containing plasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ganeev, R. A.; Singhal, H.; Naik, P. A.; Chakera, J. A.; Srivastava, A. K.; Dhami, T. S.; Joshi, M. P.; Gupta, P. D.</p> <p>2009-11-15</p> <p>The morphologies of the fullerene targets and the ablated fullerenes to determine the optimal conditions of excitation of the C{sub 60}-containing targets have been analyzed. The optimization of fullerene-containing plasma conditions allowed the enhanced <span class="hlt">harmonic</span> <span class="hlt">generation</span> in these plasmas using laser radiation of different wavelengths, pulse durations, and phase modulation. A comparison between the <span class="hlt">harmonic</span> <span class="hlt">generation</span> in single-atom/ion-containing plasmas (using bulk carbon, silver, and indium targets) and fullerene-rich plasma plumes showed better conversion efficiency for the latter medium. The influence of phase modulation of the fundamental radiation in fullerene plasmas on the spectral properties of <span class="hlt">harmonics</span> has been studied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22418507','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22418507"><span id="translatedtitle">Quasi-phase-matching high <span class="hlt">harmonic</span> <span class="hlt">generation</span> using trains of pulses produced using an array of birefringent plates.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>O'Keeffe, Kevin; Robinson, Tom; Hooker, Simon M</p> <p>2012-03-12</p> <p>Quasi-phase-matched high <span class="hlt">harmonic</span> <span class="hlt">generation</span> using trains of up to 8 counter-propagating pulses is explored. For trains of up to 4 pulses the measured enhancement of the <span class="hlt">harmonic</span> signal scales with the number of pulses N as (N + 1)², as expected. However, for trains with N > 4, no further enhancement of the <span class="hlt">harmonic</span> signal is observed. This effect is ascribed to changes of the coherence length Lc within the <span class="hlt">generating</span> medium. Techniques for overcoming the variation of Lc are discussed. The pressure dependence of quasi-phase-matching is investigated and the switch from true-phase-matching to quasi-phase-matching is observed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1014113','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1014113"><span id="translatedtitle">A Proof-Of-Principle Echo-Enabled <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> Experiment at SLAC</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dunning, Michael; Colby, Eric; Ding, Yuantao; Frederico, Joel; Gilevich, Sasha; Hast, Carsten; Jobe, R.; McCormick, Douglas; Nelson, Janice; Raubenheimer, Tor; Soong, Ken; Stupakov, Gennady; Szalata, Zenon; Walz, Dieter; Weathersby, Stephen; Woodley, Mark; Xiang, Dao; Corlett, John; Penn, Gregory; Prestemon, Soren; Qiang, Ji; /LBL, Berkeley /LBL, Berkeley /LBL, Berkeley /LBL, Berkeley /LPHE, Lausanne</p> <p>2011-05-20</p> <p>In this paper we describe the technical design of an ongoing proof-of-principle echo-enabled <span class="hlt">harmonic</span> <span class="hlt">generation</span> (EEHG) experiment at the Next Linear Collider Test Accelerator (NLCTA) at SLAC.We present the design considerations and the technical details of the experiment. Recently a new method, entitled echo-enabled <span class="hlt">harmonic</span> <span class="hlt">generation</span>, was proposed for <span class="hlt">generation</span> of high <span class="hlt">harmonics</span> using the beam echo effect. In an EEHG free electron laser (FEL), an electron beam is energy modulated in a modulator and then sent through a dispersive section with a high dispersion strength. After this first stage, the modulation obtained in the modulator is macroscopically washed out, while simultaneously introducing complicated fine structure (separated energy bands) into the phase space of the beam. A second laser is used to further modulate the beam energy in a second modulator. After passing through a second dispersive section, the separated energy bands will be converted into current modulation and the echo signal then occurs as a recoherence effect caused by the mixing of the correlations between the modulation in the second modulator and the fine structures in the beam. The EEHG scheme has a remarkable up-frequency conversion efficiency; it has been shown that the EEHG FEL scheme may allow <span class="hlt">generation</span> of soft x-rays directly from a UV seed laser in a single stage. In order to confirm the physics behind the EEHG technique and benchmark the theory, a proof-of-principleEEHG experimentwas planned at SLAC. The experiment is now in a commissioning stage and the preliminary results are reported in a separate paper of these proceedings. In this paper we present the design considerations and the details of the experiment setup.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22068548','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22068548"><span id="translatedtitle">Single attosecond pulse from terahertz-assisted high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Balogh, Emeric; Kovacs, Katalin; Dombi, Peter; Farkas, Gyozo; Fulop, Jozsef A.; Hebling, Janos; Tosa, Valer; Varju, Katalin</p> <p>2011-08-15</p> <p>High-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to <span class="hlt">generate</span> single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse <span class="hlt">generation</span> from 23 to 93 eV. We demonstrate that phase-matching effects are responsible for the <span class="hlt">generation</span> of isolated attosecond pulses, even in conditions when single-atom response yields an attosecond pulse train.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/434974','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/434974"><span id="translatedtitle">High-gain <span class="hlt">harmonic</span> <span class="hlt">generation</span> of soft X-rays with the `fresh bunch` technique</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yu, Li-Hua; Ben-Zvi, I.</p> <p>1996-10-01</p> <p>We report numerical simulations (using the TDA code) and analytic verification of the <span class="hlt">generation</span> of 64 {Angstrom} high power soft X- rays from an exponential regime single pass seeded FEL. The seed is <span class="hlt">generated</span> in the FEL using the High Gain <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> (HGHG) technique combined with the `Fresh bunch` technique. A seed pulse at 2944 {Angstrom} is <span class="hlt">generated</span> by conventional laser techniques. The seed pulse produces an intense energy modulation of the rear part of a I GeV, 1245 {Angstrom} electron beam in a `modulator` wiggler. In the `radiator` wiggler, (resonant to 64 {Angstrom}), the energy modulation creates beam density modulation followed by radiation of the 46{sup th} <span class="hlt">harmonic</span> of the seed. We use a magnetic delay to position the 64 A{Angstrom} radiation at the undisturbed front of the bunch to serve as a seed for a single pass, exponential growth FEL. After a 9 m long exponential section followed by a 7 m long tapered section the radiation power reaches 3.3 GW.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1171169','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1171169"><span id="translatedtitle">Oscillator Seeding of a High Gain <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> FEL in a Radiator-First Configuration</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gandhi, P.; Wurtele, J.; Penn, G.; Reinsch, M.</p> <p>2012-05-20</p> <p>A longitudinally coherent X-ray pulse from a high repetition rate free electron laser (FEL) is desired for a wide variety of experimental applications. However, <span class="hlt">generating</span> such a pulse with a repetition rate greater than 1 MHz is a significant challenge. The desired high repetition rate sources, primarily high <span class="hlt">harmonic</span> <span class="hlt">generation</span> with intense lasers in gases or plasmas, do not exist now, and, for the multi-MHz bunch trains that superconducting accelerators can potentially produce, are likely not feasible with current technology. In this paper, we propose to place an oscillator downstream of a radiator. The oscillator <span class="hlt">generates</span> radiation that is used as a seed for a high gain <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HGHG) FEL which is upstream of the oscillator. For the first few pulses the oscillator builds up power and, until power is built up, the radiator has no HGHG seed. As power in the oscillator saturates, the HGHG is seeded and power is produced. The dynamics and stability of this radiator-first scheme is explored analytically and numerically. A single-pass map is derived using a semi-analytic model for FEL gain and saturation. Iteration of the map is shown to be in good agreement with simulations. A numerical example is presented for a soft X-ray FEL.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhB.122..242G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhB.122..242G"><span id="translatedtitle">Simulations of high <span class="hlt">harmonic</span> <span class="hlt">generation</span> from plasmonic nanoparticles in the terahertz region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grynko, Yevgen; Zentgraf, Thomas; Meier, Torsten; Förstner, Jens</p> <p>2016-09-01</p> <p>Metallic nanostructures are known for enhancing weak nonlinear processes when a resonant and coherent excitation takes place. With proper structural design, an additional boost of particular nonlinear processes is expected to be possible. Here, we present a numerical technique that is capable of simulating high <span class="hlt">harmonic</span> <span class="hlt">generation</span> from resonantly excited metallic nanoparticles in the terahertz frequency range. We demonstrate our method by investigating the nonlinear emission of arrays of plasmonic split-ring resonators at the range of ten terahertzs. Our multiscale, non-perturbative, and microscopic approach is based on a self-consistent combination of a hydrodynamic model for the nonlinear electronic material response and the discontinuous Garlerkin time-domain technique for the evaluation of the propagation of the electromagnetic field. It is predicted that the electronic nonlinearities of plasmonic nanoparticles give rise to several <span class="hlt">harmonics</span> in the light emission when excited by intense terahertz radiation. Furthermore, our analysis predicts a non-perturbative scaling of higher <span class="hlt">harmonics</span> at high excitation intensities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5062548','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5062548"><span id="translatedtitle">High-<span class="hlt">harmonic</span> <span class="hlt">generation</span> by field enhanced femtosecond pulses in metal-sapphire nanostructure</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Han, Seunghwoi; Kim, Hyunwoong; Kim, Yong Woo; Kim, Young-Jin; Kim, Seungchul; Park, In-Yong; Kim, Seung-Woo</p> <p>2016-01-01</p> <p>Plasmonic high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) drew attention as a means of producing coherent extreme ultraviolet (EUV) radiation by taking advantage of field enhancement occurring in metallic nanostructures. Here a metal-sapphire nanostructure is devised to provide a solid tip as the HHG emitter, replacing commonly used gaseous atoms. The fabricated solid tip is made of monocrystalline sapphire surrounded by a gold thin-film layer, and intended to produce EUV <span class="hlt">harmonics</span> by the inter- and intra-band oscillations of electrons driven by the incident laser. The metal-sapphire nanostructure enhances the incident laser field by means of surface plasmon polaritons, triggering HHG directly from moderate femtosecond pulses of ∼0.1 TW cm−2 intensities. The measured EUV spectra exhibit odd-order <span class="hlt">harmonics</span> up to ∼60 nm wavelengths without the plasma atomic lines typically seen when using gaseous atoms as the HHG emitter. This experimental outcome confirms that the plasmonic HHG approach is a promising way to realize coherent EUV sources for nano-scale near-field applications in spectroscopy, microscopy, lithography and atto-second physics. PMID:27721374</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPhB...48w4005S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPhB...48w4005S"><span id="translatedtitle">Opportunities for chiral discrimination using high <span class="hlt">harmonic</span> <span class="hlt">generation</span> in tailored laser fields</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smirnova, Olga; Mairesse, Yann; Patchkovskii, Serguei</p> <p>2015-12-01</p> <p>Chiral discrimination with high <span class="hlt">harmonic</span> <span class="hlt">generation</span> (cHHG method) has been introduced in the recent work by R Cireasa et al (2015 Nat. Phys. 11 654-8). In its original implementation, the cHHG method works by detecting high <span class="hlt">harmonic</span> emission from randomly oriented ensemble of chiral molecules driven by elliptically polarized field, as a function of ellipticity. Here we discuss future perspectives in the development of this novel method, the ways of increasing chiral dichroism using tailored laser pulses, new detection schemes involving high <span class="hlt">harmonic</span> phase measurements, and concentration-independent approaches. Using the example of the epoxypropane molecule CH3CHCH2O (also known as 1,2-propylene oxide), we show theoretically that application of two-color counter-rotating elliptically polarized laser fields yields an order of magnitude enhancement of chiral dichroism compared to single color elliptical fields. We also describe how one can introduce a new functionality to cHHG: concentration-independent measurement of the enatiomeric excess in a mixture of randomly oriented left-handed and right-handed molecules. Finally, for arbitrary configurations of laser fields, we connect the observables of the cHHG method to the amplitude and phase of chiral response, providing a basis for reconstructing wide range of chiral dynamics from cHHG measurements, with femtosecond to sub-femtosecond temporal resolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4412819','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4412819"><span id="translatedtitle">Characterization of Tissue-Engineered Posterior Corneas Using Second- and Third-<span class="hlt">Harmonic</span> <span class="hlt">Generation</span> Microscopy</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Jay, Louis; Bourget, Jean-Michel; Goyer, Benjamin; Singh, Kanwarpal; Brunette, Isabelle; Ozaki, Tsuneyuki; Proulx, Stéphanie</p> <p>2015-01-01</p> <p>Three-dimensional tissues, such as the cornea, are now being engineered as substitutes for the rehabilitation of vision in patients with blinding corneal diseases. Engineering of tissues for translational purposes requires a non-invasive monitoring to control the quality of the resulting biomaterial. Unfortunately, most current methods still imply invasive steps, such as fixation and staining, to clearly observe the tissue-engineered cornea, a transparent tissue with weak natural contrast. Second- and third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> imaging are well known to provide high-contrast, high spatial resolution images of such tissues, by taking advantage of the endogenous contrast agents of the tissue itself. In this article, we imaged tissue-engineered corneal substitutes using both <span class="hlt">harmonic</span> microscopy and classic histopathology techniques. We demonstrate that second- and third-<span class="hlt">harmonic</span> imaging can non-invasively provide important information regarding the quality and the integrity of these partial-thickness posterior corneal substitutes (observation of collagen network, fibroblasts and endothelial cells). These two nonlinear imaging modalities offer the new opportunity of monitoring the engineered corneas during the entire process of production. PMID:25918849</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005OExpr..13.8263B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005OExpr..13.8263B"><span id="translatedtitle">Visualization of mitochondria in cardiomyocytes by simultaneous <span class="hlt">harmonic</span> <span class="hlt">generation</span> and fluorescence microscopy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barzda, Virginijus; Greenhalgh, Catherine; Aus der Au, Jürg; Elmore, Steven; Hgm van Beek, Johannes; Squier, Jeff</p> <p>2005-10-01</p> <p>The simultaneous detection of third <span class="hlt">harmonic</span> (THG), and multiphoton excitation fluorescence (MPF) or second <span class="hlt">harmonic</span> (SHG) from the same focal volume has led us to the development of a nonlinear multimodal microscopic biological imaging tool. The multimodal microscope has been applied for imaging of isolated live cardiomyocytes, and investigation of structural origin of the THG and SHG signals has been performed. By employing the different image contrast mechanisms, differentiation of structures inside a single live adult rat cardiomyocyte has been achieved. Based on structural crosscorrelation image analysis between NAD(P)H fluorescence and THG, and morphology of cardiomyocytes we were able to assign large part of the structure revealed by THG to the mitochondria. The crosscorrelation of THG with fluorescence of tetramethylrhodamine methyl ester (TMRM) labeled cardiomyocytes confirmed the mitochondrial origin of THG. The SHG <span class="hlt">generated</span> structures were anticorrelated with THG and possessed the characteristic pattern of the myofibrils in the myocyte in accordance with the literature. Possible visualization of mitochondria with THG microscopy appeared due to enhancement of the third <span class="hlt">harmonic</span> by multilayer arrangement of cristae.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatCo...713105H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatCo...713105H"><span id="translatedtitle">High-<span class="hlt">harmonic</span> <span class="hlt">generation</span> by field enhanced femtosecond pulses in metal-sapphire nanostructure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Han, Seunghwoi; Kim, Hyunwoong; Kim, Yong Woo; Kim, Young-Jin; Kim, Seungchul; Park, In-Yong; Kim, Seung-Woo</p> <p>2016-10-01</p> <p>Plasmonic high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) drew attention as a means of producing coherent extreme ultraviolet (EUV) radiation by taking advantage of field enhancement occurring in metallic nanostructures. Here a metal-sapphire nanostructure is devised to provide a solid tip as the HHG emitter, replacing commonly used gaseous atoms. The fabricated solid tip is made of monocrystalline sapphire surrounded by a gold thin-film layer, and intended to produce EUV <span class="hlt">harmonics</span> by the inter- and intra-band oscillations of electrons driven by the incident laser. The metal-sapphire nanostructure enhances the incident laser field by means of surface plasmon polaritons, triggering HHG directly from moderate femtosecond pulses of ~0.1 TW cm-2 intensities. The measured EUV spectra exhibit odd-order <span class="hlt">harmonics</span> up to ~60 nm wavelengths without the plasma atomic lines typically seen when using gaseous atoms as the HHG emitter. This experimental outcome confirms that the plasmonic HHG approach is a promising way to realize coherent EUV sources for nano-scale near-field applications in spectroscopy, microscopy, lithography and atto-second physics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PhRvA..81e3850V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhRvA..81e3850V"><span id="translatedtitle">Size dependence of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> at the surface of microspheres</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Viarbitskaya, Sviatlana; Kapshai, Valery; van der Meulen, Peter; Hansson, Tony</p> <p>2010-05-01</p> <p>The resonance-enhanced surface second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) from a suspension of polystyrene microspheres was investigated as a function of particle size in a range of the order of the fundamental wavelength for two different second-<span class="hlt">harmonic</span>-enhancing dyes—malachite green and pyridine 1. The two dyes gave the same strongly modulated pattern of the forward second-<span class="hlt">harmonic</span> scattering efficiency. Direct comparison to the nonlinear Rayleigh-Gans-Debye (NLRGD) and nonlinear Wentzel-Kramers-Brillouin (NLWKB) model predictions showed that the NLWKB model reproduces the overall trend in the size dependence but fails with respect to the strong modulations. The standard NLRGD model was found to fail altogether in the present particle size range, which was well beyond the observed upper particle size for which the NLRGD and NLWKB models give comparable results. A generalization of the NLRGD model to allow for dispersion and to use the particle refractive indices instead of those of the surrounding medium extended its applicability range by almost an order of magnitude in particle size. There is a pronounced maximal SHG efficiency for particles with a radius that is close to the fundamental wavelength inside the particle. The optically soft particle approximation is inadequate to describe the SHG in this particle size range, as refraction and reflection of the waves at the particle surface have a decisive influence. Dispersion of the media plays a negligible role for particle sizes up to about twice the optimal one for SHG.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21408928','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21408928"><span id="translatedtitle">Size dependence of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> at the surface of microspheres</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Viarbitskaya, Sviatlana; Meulen, Peter van der; Hansson, Tony; Kapshai, Valery</p> <p>2010-05-15</p> <p>The resonance-enhanced surface second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) from a suspension of polystyrene microspheres was investigated as a function of particle size in a range of the order of the fundamental wavelength for two different second-<span class="hlt">harmonic</span>-enhancing dyes--malachite green and pyridine 1. The two dyes gave the same strongly modulated pattern of the forward second-<span class="hlt">harmonic</span> scattering efficiency. Direct comparison to the nonlinear Rayleigh-Gans-Debye (NLRGD) and nonlinear Wentzel-Kramers-Brillouin (NLWKB) model predictions showed that the NLWKB model reproduces the overall trend in the size dependence but fails with respect to the strong modulations. The standard NLRGD model was found to fail altogether in the present particle size range, which was well beyond the observed upper particle size for which the NLRGD and NLWKB models give comparable results. A generalization of the NLRGD model to allow for dispersion and to use the particle refractive indices instead of those of the surrounding medium extended its applicability range by almost an order of magnitude in particle size. There is a pronounced maximal SHG efficiency for particles with a radius that is close to the fundamental wavelength inside the particle. The optically soft particle approximation is inadequate to describe the SHG in this particle size range, as refraction and reflection of the waves at the particle surface have a decisive influence. Dispersion of the media plays a negligible role for particle sizes up to about twice the optimal one for SHG.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016APS..DMP.D1061L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016APS..DMP.D1061L&link_type=ABSTRACT"><span id="translatedtitle">Role of quantum trajectory in high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> in the Keldysh multiphoton regime</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Peng-Cheng; Chu, Shih-I.</p> <p>2016-05-01</p> <p>We present a systematic study of quantum-trajectory analysis of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) by solving accurately the time-dependent Schrödinger equation for a hydrogen atom in the multiphoton regime where the Keldysh parameter is greater unity. We perform the time-frequency transform to explore the spectral characteristics of the HHG. We find that the time-frequency spectra exhibit a broken distribution at above-threshold HHG due to the competition associated with the short- and long-trajectories when the ionization process is pushed from the multiphoton regime into the tunneling regime, it implies that the <span class="hlt">harmonic</span> emission in the broken regions of time-frequency spectra are suppressed. In addition, we present a time-dependent density-functional theory approach for an ab initio study of the effect of correlated multielectron responses on the <span class="hlt">harmonic</span> emission of Ar atom associated with the quantum trajectories in the multiphoton regime. This work is partially supported by DOE.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......485A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......485A"><span id="translatedtitle"><span class="hlt">Acoustic</span> bubble: Controlled and selective micropropulsion and chemical waveform <span class="hlt">generator</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ahmed, Daniel</p> <p></p> <p>The physics governing swimming at the microscale---where viscous forces dominate over inertial---is distinctly different than that at the macroscale. Devices capable of finely controlled swimming at the microscale could enable bold ideas such as targeted drug delivery, non-invasive microsurgery, and precise materials assembly. Progress has already been made towards such artificial microswimmers using several means of actuation: chemical reactions and applied magnetic, electric or <span class="hlt">acoustic</span> fields. However, the prevailing goal of selective actuation of a single microswimmer from within a group, the first step towards collaborative, guided action by a group of swimmers, has so far not been achieved. Here I present a new class of microswimmer that accomplishes for the first time selective actuation (Chapter 1). The swimmer design eschews the commonly-held design paradigm that microswimmers must use non-reciprocal motion to achieve propulsion; instead, the swimmer is propelled by oscillatory motion of an air bubble trapped within the swimmer's polymer body. This oscillatory motion is driven by a low-power biocompatible <span class="hlt">acoustic</span> field to the ambient liquid, with meaningful swimmer propulsion occurring only at resonance frequencies of the bubble. This <span class="hlt">acoustically</span>-powered microswimmer performs controllable rapid translational and rotational motion even in highly viscous liquid. By using a group of swimmers each with a different bubble size (and thus different resonance frequencies) selective actuation of a single swimmer from among the group can be readily achieved. Cellular response to chemical microenvironments depends on the spatiotemporal characteristics of the stimulus, which is central to many biological processes including gene expression, cell migration, differentiation, apoptosis, and intercellular signaling. To date, studies have been limited to digital (or step) chemical stimulation with little control over the temporal counterparts. Microfluidic approaches</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/11308955','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/11308955"><span id="translatedtitle">Effect of nonadiabaticity of dust charge variation on dust <span class="hlt">acoustic</span> waves: <span class="hlt">generation</span> of dust <span class="hlt">acoustic</span> shock waves.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gupta, M R; Sarkar, S; Ghosh, S; Debnath, M; Khan, M</p> <p>2001-04-01</p> <p>The effect of nonadiabaticity of dust charge variation arising due to small nonzero values of tau(ch)/tau(d) has been studied where tau(ch) and tau(d) are the dust charging and dust hydrodynamical time scales on the nonlinear propagation of dust <span class="hlt">acoustic</span> waves. Analytical investigation shows that the propagation of a small amplitude wave is governed by a Korteweg-de Vries (KdV) Burger equation. Notwithstanding the soliton decay, the "soliton mass" is conserved, but the dissipative term leads to the development of a noise tail. Nonadiabaticity <span class="hlt">generated</span> dissipative effect causes the <span class="hlt">generation</span> of a dust <span class="hlt">acoustic</span> shock wave having oscillatory behavior on the downstream side. Numerical investigations reveal that the propagation of a large amplitude dust <span class="hlt">acoustic</span> shock wave with dust density enhancement may occur only for Mach numbers lying between a minimum and a maximum value whose dependence on the dusty plasma parameters is presented. PMID:11308955</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1223349','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1223349"><span id="translatedtitle">Long-term operation of surface high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> from relativistic oscillating mirrors using a spooling tape</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bierbach, Jana; Yeung, Mark; Eckner, Erich; Roedel, Christian; Kuschel, Stephan; Zepf, Matt; Paulus, Gerhard G.</p> <p>2015-05-01</p> <p>Surface high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in the relativistic regime is demonstrated as a source of extreme ultra-violet (XUV) pulses with extended operation time. Relativistic high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> is driven by a frequency-doubled high-power Ti:Sapphire laser focused to a peak intensity of 3·1019 W/cm2 onto spooling tapes. We demonstrate continuous operation over up to one hour runtime at a repetition rate of 1 Hz. <span class="hlt">Harmonic</span> spectra ranging from 20 eV to 70 eV (62 nm to 18 nm) were consecutively recorded by an XUV spectrometer. An average XUV pulse energy in the µJ range is measured. With the presented setup, relativistic surface high-<span class="hlt">harmonic</span> <span class="hlt">generation</span> becomes a powerful source of coherent XUV pulses that might enable applications in, e.g. attosecond laser physics and the seeding of free-electron lasers, when the laser issues causing 80-% pulse energy fluctuations are overcome.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AIPC.1403..231M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AIPC.1403..231M"><span id="translatedtitle">The <span class="hlt">Generation</span> of <span class="hlt">Harmonic</span> Distortion and Distortion Products in a Computational Model of the Cochlea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meaud, Julien; Li, Yizeng; Grosh, Karl</p> <p>2011-11-01</p> <p>It is generally agreed that the nonlinear response of the cochlea is due to the forward transduction of the outer hair cell (OHC) hair bundle (HB) and subsequent alteration of the active force applied to the cochlear structures, including the basilar membrane (BM). A mechanical-<span class="hlt">acoustical</span>-electrical model of the cochlea with three-dimensional fluid representation, and feedback from OHC somatic motility coupled to nonlinear HB mechanotransduction is used to predict nonlinear distortion of the BM response to <span class="hlt">acoustic</span> stimulus. An efficient alternating frequency time scheme is implemented to solve for the nonlinear stationary dynamics of the cochlea. The model is used to predict the location of maximum <span class="hlt">generation</span> of nonlinear distortion during pure tone and two-tone stimulation as well as the propagation of the distortion components on the BM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhB...49q2002H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhB...49q2002H"><span id="translatedtitle">Single-pass high <span class="hlt">harmonic</span> <span class="hlt">generation</span> at high repetition rate and photon flux</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hädrich, Steffen; Rothhardt, Jan; Krebs, Manuel; Demmler, Stefan; Klenke, Arno; Tünnermann, Andreas; Limpert, Jens</p> <p>2016-09-01</p> <p>Sources of short wavelength radiation with femtosecond to attosecond pulse durations, such as synchrotrons or free electron lasers, have already made possible numerous, and will facilitate more, seminal studies aimed at understanding atomic and molecular processes on fundamental length and time scales. Table-top sources of coherent extreme ultraviolet to soft x-ray radiation enabled by high <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) of ultrashort pulse lasers have also gained significant attention in the last few years due to their enormous potential for addressing a plethora of applications, therefore constituting a complementary source to large-scale facilities (synchrotrons and free electron lasers). Ti:sapphire based laser systems have been the workhorses for HHG for decades, but are limited in repetition rate and average power. On the other hand, it has been widely recognized that fostering applications in fields such as photoelectron spectroscopy and microscopy, coincidence detection, coherent diffractive imaging and frequency metrology requires a high repetition rate and high photon flux HHG sources. In this article we will review recent developments in realizing the demanding requirement of producing a high photon flux and repetition rate at the same time. Particular emphasis will be put on suitable ultrashort pulse and high average power lasers, which directly drive <span class="hlt">harmonic</span> <span class="hlt">generation</span> without the need for external enhancement cavities. To this end we describe two complementary schemes that have been successfully employed for high power fiber lasers, i.e. optical parametric chirped pulse amplifiers and nonlinear pulse compression. Moreover, the issue of phase-matching in tight focusing geometries will be discussed and connected to recent experiments. We will highlight the latest results in fiber laser driven high <span class="hlt">harmonic</span> <span class="hlt">generation</span> that currently produce the highest photon flux of all existing sources. In addition, we demonstrate the first promising applications and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21192544','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21192544"><span id="translatedtitle">Laser absorption and third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in free-electron nanofilms</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fomichev, Sergey V.; Zaretsky, David F.; Becker, Wilhelm</p> <p>2009-02-15</p> <p>The collective collisionless dynamics of the electron gas in free-electron nanofilms irradiated by an obliquely incident p-polarized laser wave are considered in the classical hydrodynamic and jellium-model approximations. The two cases of cold metallic nanofilms and hot free-electron nanofilms laser ionized and laser heated by a pump-laser prepulse are investigated with proper electron statistics. Both linear and nonlinear properties of the plasma resonance excitation in the nanofilms are studied in detail for different film parameters (film thickness, thickness of the diffuse film boundary, outer-ionization degree for hot laser-ionized/heated films, etc.). The significant role of the diffuse film boundaries for both linear absorption of the laser field and third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> is demonstrated. For this goal, we do not use the standard dielectric-permittivity approach with boundary conditions between two different media but solve continuously over all space the full set of hydrodynamic and electrodynamic equations in nonrelativistic one-dimensional approximation. It is shown that collisionless edge absorption may be dominant in thin nanofilms, while in cold metal nanofilms it results in the appearance of several linear-absorption resonances below the bulk-plasma resonance frequency. For hot nanofilms, drastic broadening of the linear-plasma-resonance profile is obtained in calculations when the film thickness is reduced. In our model, the third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> is determined by the density gradient in the diffuse film edges. Additional resonances in third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> as a function of laser frequency are obtained for cold metal nanofilms. They differ from the standard third-order nonlinear resonance, which is located at one third of the plasma resonance frequency. The important role of the outer-ionization degree in forming the third-order nonlinear response of the hot laser-ionized film is also analyzed and discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25831331','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25831331"><span id="translatedtitle">Third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy reveals dental anatomy in ancient fossils.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Yu-Cheng; Lee, Szu-Yu; Wu, Yana; Brink, Kirstin; Shieh, Dar-Bin; Huang, Timothy D; Reisz, Robert R; Sun, Chi-Kuang</p> <p>2015-04-01</p> <p>Fossil teeth are primary tools in the study of vertebrate evolution, but standard imaging modalities have not been capable of providing high-quality images in dentin, the main component of teeth, owing to small refractive index differences in the fossilized dentin. Our first attempt to use third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) microscopy in fossil teeth has yielded significant submicrometer level anatomy, with an unexpectedly strong signal contrasting fossilized tubules from the surrounding dentin. Comparison between fossilized and extant teeth of crocodilians reveals a consistent evolutionary signature through time, indicating the great significance of THG microscopy in the evolutionary studies of dental anatomy in fossil teeth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JBO....16d6019T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JBO....16d6019T"><span id="translatedtitle">Cell tracking in live Caenorhabditis elegans embryos via third <span class="hlt">harmonic</span> <span class="hlt">generation</span> imaging microscopy measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tserevelakis, George J.; Filippidis, George; Megalou, Evgenia V.; Fotakis, Costas; Tavernarakis, Nektarios</p> <p>2011-04-01</p> <p>In this study, we demonstrate the potential of employing third <span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) imaging microscopy measurements for cell tracking studies in live Caenorhabditis elegans (C. elegans) embryos. A 1028-nm femtosecond laser was used for the excitation of unstained C. elegans samples. Different C. elegans embryonic stages (from two-cell to threefold) were imaged. Live biological specimens were irradiated for prolonged periods of time (up to 7 h), testifying to the nondestructive nature of this nonlinear imaging technique. Thus, THG image contrast modality is a powerful diagnostic tool for probing in vivo cell division during early embryogenesis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004OptL...29.2881D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004OptL...29.2881D"><span id="translatedtitle">Velocimetric third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy: micrometer-scale quantification of morphogenetic movements in unstained embryos</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Débarre, Delphine; Supatto, Willy; Farge, Emmanuel; Moulia, Bruno; Schanne-Klein, Marie-Claire; Beaurepaire, Emmanuel</p> <p>2004-12-01</p> <p>We demonstrate the association of third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) microscopy and particle image velocimetry (PIV) analysis as a novel functional imaging technique for automated micrometer-scale characterization of morphogenetic movements in developing embryos. Using a combined two-photon-excited fluorescence and THG microscope, we characterize the optical properties of Drosophila embryos and show that sustained THG imaging does not perturb sensitive developmental dynamics. Velocimetric THG imaging provides a quantitative description of the dynamics of internal structures in unstained wild-type and mutant embryos.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4574672','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4574672"><span id="translatedtitle">Ultrastructural features of collagen in thyroid carcinoma tissue observed by polarization second <span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Tokarz, Danielle; Cisek, Richard; Golaraei, Ahmad; Asa, Sylvia L.; Barzda, Virginijus; Wilson, Brian C.</p> <p>2015-01-01</p> <p>Changes in collagen ultrastructure between malignant and normal human thyroid tissue were investigated ex vivo using polarization second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) microscopy. The second-order nonlinear optical susceptibility tensor component ratio and the degree of linear polarization (DOLP) of the SHG signal were measured. The ratio values are related to the collagen ultrastructure, while DOLP indicates the relative amount of coherent signal and incoherent scattering of SHG. Increase in ratio values and decrease in DOLP were observed for tumor tissue compared to normal thyroid, indicating higher ultrastructural disorder in tumor collagen. PMID:26417516</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhLA..380..304M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhLA..380..304M"><span id="translatedtitle">Frequency dependence of optical third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> from doped graphene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Margulis, Vl. A.; Muryumin, E. E.; Gaiduk, E. A.</p> <p>2016-01-01</p> <p>In connection with the controversial question about the frequency dependence of the optical third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) from doped graphene, which has recently been discussed in the literature, we develop an analytical theory for the THG susceptibility of doped graphene by using the original Genkin-Mednis nonlinear-conductivity-theory formalism including mixed intra- and interband terms. The theory is free of any nonphysical divergences at zero frequency, and it predicts the main resonant peak in the THG spectrum to be located at the photon energy ħω equal to two thirds of the Fermi energy EF of charge carriers in doped graphene.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22398884','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22398884"><span id="translatedtitle">Enhanced third <span class="hlt">harmonic</span> <span class="hlt">generation</span> from the epsilon-near-zero modes of ultrathin films</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Luk, Ting S. Liu, Sheng; Campione, Salvatore; Ceglia, Domenico de; Vincenti, Maria A.; Keeler, Gordon A.; Sinclair, Michael B.; Prasankumar, Rohit P.; Scalora, Michael</p> <p>2015-04-13</p> <p>We experimentally demonstrate efficient third <span class="hlt">harmonic</span> <span class="hlt">generation</span> from an indium tin oxide nanofilm (λ/42 thick) on a glass substrate for a pump wavelength of 1.4 μm. A conversion efficiency of 3.3 × 10{sup −6} is achieved by exploiting the field enhancement properties of the epsilon-near-zero mode with an enhancement factor of 200. This nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1235265','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1235265"><span id="translatedtitle">Enhanced third <span class="hlt">harmonic</span> <span class="hlt">generation</span> from the epsilon-near-zero modes of ultrathin films</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Luk, Ting S.; De Ceglia, Domenico; Liu, Sheng; Keeler, Gordon Arthur; Prasankumar, Rohit; Los Alamos National Lab. , Los Alamos, NM ; Vincenti, Maria A; Scalora, Michael; Sinclair, Michael B.; campione, salvatore</p> <p>2015-04-13</p> <p>We demonstrate, through our experimentation, efficient third <span class="hlt">harmonic</span> <span class="hlt">generation</span> from an indium tin oxide nanofilm (λ/42 thick) on a glass substrate for a pump wavelength of 1.4 μm. A conversion efficiency of 3.3 × 10<sup>-6</sup> is achieved by exploiting the field enhancement properties of the epsilon-near-zero mode with an enhancement factor of 200. Furthermore, this nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JMOp...63.1719R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JMOp...63.1719R"><span id="translatedtitle">Broadband second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in an imperfect nonlinear photonic crystal with random defects</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ren, Kun; Liu, Yali; Ren, Xiaobin; Fan, Jingyang</p> <p>2016-09-01</p> <p>In this paper, we study broadband second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) in an imperfect nonlinear photonic crystal in which defects are introduced with random lengths. We show that the efficient SHG output is obtained when the length of each defect varies near certain specialized values. The bandwidth of the SHG output broadens with the increasing randomness of defect length. Moreover, the SHG bandwidth is nearly unaffected only when the total length of the whole structure is long enough. The disordered structure also exhibits good tolerance to the fabrication error, which provides a way to control SHG intensity and bandwidth separately.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvA..94a3811G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvA..94a3811G"><span id="translatedtitle">Perturbation theory for graphene-integrated waveguides: Cubic nonlinearity and third-<span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gorbach, Andrey V.; Ivanov, Edouard</p> <p>2016-07-01</p> <p>We present perturbation theory for analysis of generic third-order nonlinear processes in graphene-integrated photonic structures. The optical response of graphene is treated as the nonlinear boundary condition in Maxwell's equations. The derived models are applied for analysis of third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> in a graphene-coated dielectric microfiber. An efficiency of up to a few percent is predicted when using subpicosecond pump pulses with energies of the order of 0.1 nJ in a submillimeter-long fiber when operating near the resonance of the graphene nonlinear conductivity ℏ ω =(2 /3 ) EF .</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21466612','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21466612"><span id="translatedtitle">Study of the second <span class="hlt">harmonic</span> <span class="hlt">generation</span> and optical rectification in a cBN crystal</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dou Qingping; Ma Haitao; Jia Gang; Chen Zhanguo; Cao Kun; Zhang Tiechen</p> <p>2007-02-28</p> <p>Cubic boron nitride (cBN) - a kind of an artificial (synthetic) crystal with the band gap of {approx}6.3 eV, which has the zinc blende structure and the 4-bar 3m symmetry, is studied. The optical rectification is obtained and the second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) is observed in the cBN crystal for the first time by using a 1064-nm Q-switched Nd:YAG laser. The green light at 532 nm from the cBN sample can be seen with a naked eye. (nonlinear optical phenomena)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010SPIE.7569E..2AS&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010SPIE.7569E..2AS&link_type=ABSTRACT"><span id="translatedtitle">Discrimination of collagen in normal and pathological dermis through polarization second <span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Su, Ping-Jung; Chen, Wei-Liang; Hong, Jin-Bon; Li, Tsung-Hsien; Wu, Ruei-Jr; Chou, Chen-Kuan; Lin, Sung-Jan; Dong, Chen-Yuan</p> <p>2010-02-01</p> <p>We used polarization-resolved, second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (P-SHG) microscopy at single pixel resolution for medical diagnosis of pathological skin dermis, and found that P-SHG can be used to distinguish normal and dermal pathological conditions of keloid, morphea, and dermal elastolysis. We find that the histograms of the d33/d31 ratio for the pathological skins to contain two peak values and to be wider than that of the normal case, suggesting that the pathological dermal collagen fibers tend to be more structurally heterogeneous. Our work demonstrates that pixel-resolved, second-order susceptibility microscopy is effective for detecting heterogeneity in spatial distribution of collagen fibers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23161560','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23161560"><span id="translatedtitle">Quantitative biomarkers of human skin photoaging based on intrinsic second <span class="hlt">harmonic</span> <span class="hlt">generation</span> signal.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhuo, Shuangmu; Zhu, Xiaoqin; Chen, Jianxin; Xie, Shusen</p> <p>2013-01-01</p> <p>Collagen change is a major feature in the photoaged human skin. Here, we present the use of intrinsic second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) signal as a novel means to quantify collagen change with photoaging. We obtain the SHG images of the superficial dermis from ex vivo the cheek skin and the abdomen skin of eight patients aged 55-60 years. The results show that SHG signal can quantitatively reveal collagen change between normal and photoaged human skin in three dimensions. By comparing normal with photoaged dermis, there are significant differences in the collagen content and fine structure, providing substantial potential to be applied in vivo for the clinical diagnosis of human skin photoaging.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22191906','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22191906"><span id="translatedtitle">Quantitative biomarkers of colonic dysplasia based on intrinsic second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> signal.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhuo, Shuangmu; Zhu, Xiaoqin; Wu, Guizhu; Chen, Jianxin; Xie, Shusen</p> <p>2011-12-01</p> <p>Most colorectal cancers arise from dysplastic lesions, such as adenomatous polyps, and these lesions are difficult to be detected by the current endoscopic screening approaches. Here, we present the use of an intrinsic second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) signal as a novel means to differentiate between normal and dysplastic human colonic tissues. We find that the SHG signal can quantitatively identify collagen change associated with colonic dysplasia that is indiscernible by conventional pathologic techniques. By comparing normal with dysplastic mucosa, there were significant differences in collagen density and collagen fiber direction, providing substantial potential to become quantitative intrinsic biomarkers for in vivo clinical diagnosis of colonic dysplasia.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APLP....1f1302B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APLP....1f1302B"><span id="translatedtitle">Impact of longitudinal fields on second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in lithium niobate nanopillars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Baghban, Mohammad Amin; Gallo, Katia</p> <p>2016-09-01</p> <p>An optimized focused ion beam process is used to fabricate micrometer-long LiNbO3 nanopillars with diameters varying between 150 and 325 nm. Polarimetric mappings of second <span class="hlt">harmonic</span> <span class="hlt">generation</span> from a wavelength of 850 nm demonstrate the ability to modify the polarization features of the nonlinear response through a fine adjustment of the pillar size. The effect is ascribed to the non-negligible contribution of the longitudinal fields associated with sub-wavelength light confinement in the LiNbO3 nanopillars. The results also highlight the importance of a fine control over the nanopillar size in order to effectively engineer their nonlinear response.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002JAP....91.9481O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002JAP....91.9481O"><span id="translatedtitle">Electric field-induced second <span class="hlt">harmonic</span> <span class="hlt">generation</span> studies of chromophore orientational dynamics in photorefractive polymers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ostroverkhova, Oksana; Stickrath, Andrew; Singer, Kenneth D.</p> <p>2002-06-01</p> <p>Photorefractive (PR) polymers are promising for use in various applications that require fast response times. The main factors that determine the PR speed in polymers are photoconductivity and chromophore reorientation in an electric field. In this article, we investigate the chromophore reorientational dynamics in various PR composites using the electric field second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (EFISHG) technique, and then relate it to the PR dynamics observed in a four-wave mixing holographic experiment. We also report on the enhancement of the EFISHG signal in the presence of HeNe light, which we attribute to a photoinduced internal electric field that formed in the PR polymer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23736450','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23736450"><span id="translatedtitle">Nanoscale optical properties of metal nanoparticles probed by Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> microscopy.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shen, Hong; Nguyen, Ngoc; Gachet, David; Maillard, Vincent; Toury, Timothée; Brasselet, Sophie</p> <p>2013-05-20</p> <p>We report spatial and vectorial imaging of local fields' confinement properties in metal nanoparticles with branched shapes, using Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> (SHG) microscopy. Taking advantage of the coherent nature of this nonlinear process, the technique provides a direct evidence of the coupling between the excitation polarization and both localization and polarization specificities of local fields at the sub-diffraction scale. These combined features, which are governed by the nanoparticles' symmetry, are not accessible using other contrasts such as linear optical techniques or two-photon luminescence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25083641','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25083641"><span id="translatedtitle">Universality of returning electron wave packet in high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> with midinfrared laser pulses.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Le, Anh-Thu; Wei, Hui; Jin, Cheng; Tuoc, Vu Ngoc; Morishita, Toru; Lin, C D</p> <p>2014-07-18</p> <p>We show that a returning electron wave packet in high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HHG) with midinfrared laser pulses converges to a universal limit for a laser wavelength above about 3 μm. The results are consistent among the different methods: a numerical solution of the time-dependent Schrödinger equation, the strong-field approximation, and the quantum orbits theory. We further analyze how the contribution from different electron "trajectories" survives the macroscopic propagation in the medium. Our result thus provides a new framework for investigating the wavelength scaling law for the HHG yields.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000SPIE.4086..777H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000SPIE.4086..777H"><span id="translatedtitle">Improved and enhanced thermal stable second <span class="hlt">harmonic</span> <span class="hlt">generation</span> of poled polymer films</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hou, Zhanjia; Liu, Liying; Liu, Haibo; Xu, Lei; Wang, Wencheng; Li, Fuming; Ye, Mingxin</p> <p>2000-11-01</p> <p>Melamine formaldehyde resin films with good optical quality could be fabricated easily by controlling the initial molecular weight. It was used as a matrix of nonlinear molecules. The optical properties of nonlinear molecules guest-host and covalent-bonded type of poled polymer systems were investigated. The optical propagation losses are around 1 dB/cm at 1072 nm for two kinds of films studied. The in situ corona poling second <span class="hlt">harmonic</span> <span class="hlt">generation</span> method and UV- visible absorption measurement were used. The experiment results showed that the materials we fabricated have improved second-order susceptibilities and higher thermal stability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApPhL.105j3705L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApPhL.105j3705L"><span id="translatedtitle">Label-free three-dimensional imaging of cell nucleus using third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, Jian; Zheng, Wei; Wang, Zi; Huang, Zhiwei</p> <p>2014-09-01</p> <p>We report the implementation of the combined third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) and two-photon excited fluorescence (TPEF) microscopy for label-free three-dimensional (3-D) imaging of cell nucleus morphological changes in liver tissue. THG imaging shows regular spherical shapes of normal hepatocytes nuclei with inner chromatin structures while revealing the condensation of chromatins and nuclear fragmentations in hepatocytes of diseased liver tissue. Colocalized THG and TPEF imaging provides complementary information of cell nuclei and cytoplasm in tissue. This work suggests that 3-D THG microscopy has the potential for quantitative analysis of nuclear morphology in cells at a submicron-resolution without the need for DNA staining.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22310855','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22310855"><span id="translatedtitle">Label-free three-dimensional imaging of cell nucleus using third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lin, Jian; Zheng, Wei; Wang, Zi; Huang, Zhiwei</p> <p>2014-09-08</p> <p>We report the implementation of the combined third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) and two-photon excited fluorescence (TPEF) microscopy for label-free three-dimensional (3-D) imaging of cell nucleus morphological changes in liver tissue. THG imaging shows regular spherical shapes of normal hepatocytes nuclei with inner chromatin structures while revealing the condensation of chromatins and nuclear fragmentations in hepatocytes of diseased liver tissue. Colocalized THG and TPEF imaging provides complementary information of cell nuclei and cytoplasm in tissue. This work suggests that 3-D THG microscopy has the potential for quantitative analysis of nuclear morphology in cells at a submicron-resolution without the need for DNA staining.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/900068','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/900068"><span id="translatedtitle">Fringe-free, Background-free, Collinear Third <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> FROG Measurements for Multiphoton Microscopy</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chadwick, R; Spahr, E; Squier, J A; Durfee, C G; Walker, B C; Fittinghoff, D N</p> <p>2006-07-21</p> <p>Collinear pulse measurement tools useful at the full numerical aperture (NA) of multiphoton microscope objectives are a necessity for a quantitative characterization of the femtosecond pulses focused by these systems. In this letter, we demonstrate a simple new technique, for characterizing the pulse at the focus in a multiphoton microscope. This technique, a background-free, fringe-free, form of frequency-resolved optical gating, uses the third <span class="hlt">harmonic</span> signal <span class="hlt">generated</span> from a glass coverslip. Here it is used to characterize 100 fs pulses (typical values for a multiphoton microscope) at the focus of a 0.65 NA objective.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5030023','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5030023"><span id="translatedtitle">Multiphoton excited hemoglobin fluorescence and third <span class="hlt">harmonic</span> <span class="hlt">generation</span> for non-invasive microscopy of stored blood</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Saytashev, Ilyas; Glenn, Rachel; Murashova, Gabrielle A.; Osseiran, Sam; Spence, Dana; Evans, Conor L.; Dantus, Marcos</p> <p>2016-01-01</p> <p>Red blood cells (RBC) in two-photon excited fluorescence (TPEF) microscopy usually appear as dark disks because of their low fluorescent signal. Here we use 15fs 800nm pulses for TPEF, 45fs 1060nm pulses for three-photon excited fluorescence, and third <span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) imaging. We find sufficient fluorescent signal that we attribute to hemoglobin fluorescence after comparing time and wavelength resolved spectra of other expected RBC endogenous fluorophores: NADH, FAD, biliverdin, and bilirubin. We find that both TPEF and THG microscopy can be used to examine erythrocyte morphology non-invasively without breaching a blood storage bag. PMID:27699111</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10175701','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10175701"><span id="translatedtitle">Magnetic field measurements of a superconducting undulator for a <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> FEL experiment at the NSLS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Solomon, L.; Ingold, G.; Ben-Zvi, I.; Krinsky, S.; Yu, L.H.; Sampson, W.; Robins, K.</p> <p>1993-07-01</p> <p>An 18mm period, 0.54 Tesla, 8mm gap superconducting undulator with both horizontal and vertical focusing has been built and tested. This magnet, which is fabricated in 25 cm length sections, is being tested for use in the radiator section (total magnet length of 1.5 m) of the <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> Free Electron Laser experiment at the National Synchrotron Light Source - Accelerator Test Facility at Brookhaven National Lab., in collaboration with Grumman Corp. The measurement system is outlined, sources and estimates of errors are described, and some magnetic field data are presented and discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006APS..MARH11007J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006APS..MARH11007J"><span id="translatedtitle">Molecular Adsorption on Nano Colloidal Particles Probed by Second <span class="hlt">Harmonic</span> <span class="hlt">Generation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jen, Shih-Hui; Dai, Hai-Lung</p> <p>2006-03-01</p> <p>It is shown that second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG), detected at 90 degree angle from the fundamental beam propagation direction, can be used to probe molecular adsorption on spherical nano colloidal particles with diameter as small as 50 nm. Measurements done with the malachite green dye adsorbed on polystyrene particles with diameters ranging from 50 to 250 nm show that the SHG signal from these surface adsorbed molecules tilts toward larger scattering angles when the particle size becomes smaller. This phenomenon can be rigorously described by the nonlinear Rayleigh-Gans-Debye theory and used for measuring the density and adsorption free energy of molecules adsorbed on nanometer size colloidal particles.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27557244','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27557244"><span id="translatedtitle">Enhanced third <span class="hlt">harmonic</span> <span class="hlt">generation</span> in a silicon metasurface using trapped mode.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tong, Wenyuan; Gong, Cheng; Liu, Xiaojun; Yuan, Shuai; Huang, Qingzhong; Xia, Jinsong; Wang, Yi</p> <p>2016-08-22</p> <p>We experimentally demonstrate enhanced third <span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) using a silicon metasurface, which is consist of symmetric spindle-shape nanoparticle array. Relying on the trapped mode supported by the high quality factor all-dielectric metasurface, the conversion efficiency of THG is about 300 times larger than that of bulk silicon slab. The maximum extinction ratio of the intensity of THG reaches about 25 dB by tuning the polarization of incident light. The simulation results agree with the experimental performances. PMID:27557244</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4568467','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4568467"><span id="translatedtitle">Resolution and contrast enhancement of subtractive second <span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy with a circularly polarized vortex beam</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Tian, Nian; Fu, Ling; Gu, Min</p> <p>2015-01-01</p> <p>We extend the subtractive imaging method to label-free second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) microscopy to enhance the spatial resolution and contrast. This method is based on the intensity difference between two images obtained with circularly polarized Gaussian and doughnut-shaped beams, respectively. By characterizing the intensity and polarization distributions of the two focused beams, we verify the feasibility of the subtractive imaging method in polarization dependent SHG microscopy. The resolution and contrast enhancement in different biological samples is demonstrated. This work will open a new avenue for the applications of SHG microscopy in biomedical research. PMID:26364733</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5030023','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5030023"><span id="translatedtitle">Multiphoton excited hemoglobin fluorescence and third <span class="hlt">harmonic</span> <span class="hlt">generation</span> for non-invasive microscopy of stored blood</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Saytashev, Ilyas; Glenn, Rachel; Murashova, Gabrielle A.; Osseiran, Sam; Spence, Dana; Evans, Conor L.; Dantus, Marcos</p> <p>2016-01-01</p> <p>Red blood cells (RBC) in two-photon excited fluorescence (TPEF) microscopy usually appear as dark disks because of their low fluorescent signal. Here we use 15fs 800nm pulses for TPEF, 45fs 1060nm pulses for three-photon excited fluorescence, and third <span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) imaging. We find sufficient fluorescent signal that we attribute to hemoglobin fluorescence after comparing time and wavelength resolved spectra of other expected RBC endogenous fluorophores: NADH, FAD, biliverdin, and bilirubin. We find that both TPEF and THG microscopy can be used to examine erythrocyte morphology non-invasively without breaching a blood storage bag.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005OExpr..13.2099M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005OExpr..13.2099M&link_type=ABSTRACT"><span id="translatedtitle">Simultaneous stimulated Raman scattering and second <span class="hlt">harmonic</span> <span class="hlt">generation</span> in periodically poled lithium niobate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McConnell, Gail; Ferguson, Allister I.</p> <p>2005-03-01</p> <p>Simultaneous stimulated Raman scattering (SRS) and second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) are demonstrated in periodically poled lithium niobate (PPLN). Using a simple single-pass geometry, conversion efficiencies of up to 12% and 19% were observed for the SRS and SHG processes respectively. By changing the PPLN period interacting with the photonic crystal fibre based pump source and varying the PPLN temperature, the SHG signal was measured to be tunable from λ =584 nm to λ =679 nm. The SRS output spectrum was measured at λ=1583 nm, with a spectral full-width at half-maximum of λ =85 nm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005OExpr..13.5791H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005OExpr..13.5791H"><span id="translatedtitle">Second <span class="hlt">harmonic</span> <span class="hlt">generation</span> imaging of collagen fibrils in cornea and sclera</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Han, Meng; Giese, Günter; Bille, Josef F.</p> <p>2005-07-01</p> <p>Collagen, as the most abundant protein in the human body, determines the unique physiological and optical properties of the connective tissues including cornea and sclera. The ultrastructure of collagen, which conventionally can only be resolved by electron microscopy, now can be probed by optical second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) imaging. SHG imaging revealed that corneal collagen fibrils are regularly packed as a polycrystalline lattice, accounting for the transparency of cornea. In contrast, scleral fibrils possess inhomogeneous, tubelike structures with thin hard shells, maintaining the high stiffness and elasticity of the sclera.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvB..94l5301T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvB..94l5301T"><span id="translatedtitle">Ab initio description of second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> from crystal surfaces</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tancogne-Dejean, Nicolas; Giorgetti, Christine; Véniard, Valérie</p> <p>2016-09-01</p> <p>We propose an ab initio framework to derive the dielectric and the second-order susceptibility tensors for crystal surfaces. The single-surface response is extracted from a supercell scheme. We evaluate macroscopic quantities, taking into account the local fields. The first- and second-order susceptibilities are evaluated within time-dependent density functional theory, in the long-wavelength limit. We apply our formalism to the calculation of the second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> for clean and hydrogenated silicon surfaces. The agreement with measured second-order susceptibility components is significantly better, illustrating the importance of local-field effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27231629','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27231629"><span id="translatedtitle">Third <span class="hlt">harmonic</span> <span class="hlt">generation</span> imaging for fast, label-free pathology of human brain tumors.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kuzmin, N V; Wesseling, P; Hamer, P C de Witt; Noske, D P; Galgano, G D; Mansvelder, H D; Baayen, J C; Groot, M L</p> <p>2016-05-01</p> <p>In brain tumor surgery, recognition of tumor boundaries is key. However, intraoperative assessment of tumor boundaries by the neurosurgeon is difficult. Therefore, there is an urgent need for tools that provide the neurosurgeon with pathological information during the operation. We show that third <span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) microscopy provides label-free, real-time images of histopathological quality; increased cellularity, nuclear pleomorphism, and rarefaction of neuropil in fresh, unstained human brain tissue could be clearly recognized. We further demonstrate THG images taken with a GRIN objective, as a step toward in situ THG microendoscopy of tumor boundaries. THG imaging is thus a promising tool for optical biopsies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25831331','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25831331"><span id="translatedtitle">Third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy reveals dental anatomy in ancient fossils.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Yu-Cheng; Lee, Szu-Yu; Wu, Yana; Brink, Kirstin; Shieh, Dar-Bin; Huang, Timothy D; Reisz, Robert R; Sun, Chi-Kuang</p> <p>2015-04-01</p> <p>Fossil teeth are primary tools in the study of vertebrate evolution, but standard imaging modalities have not been capable of providing high-quality images in dentin, the main component of teeth, owing to small refractive index differences in the fossilized dentin. Our first attempt to use third-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) microscopy in fossil teeth has yielded significant submicrometer level anatomy, with an unexpectedly strong signal contrasting fossilized tubules from the surrounding dentin. Comparison between fossilized and extant teeth of crocodilians reveals a consistent evolutionary signature through time, indicating the great significance of THG microscopy in the evolutionary studies of dental anatomy in fossil teeth. PMID:25831331</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996ApOpt..35.4169P&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996ApOpt..35.4169P&link_type=ABSTRACT"><span id="translatedtitle">Atmospheric thermometry for metallic surfaces by laser-induced second-<span class="hlt">harmonic</span> <span class="hlt">generation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pedanekar, Niranjan R.; Yin, Huiqi; Laurendeau, Normand M.</p> <p>1996-07-01</p> <p>To the best of our knowledge we report the first demonstration of surface thermometry using laser-induced second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) on a realistic metallic surface at atmospheric pressure. The surface is probed with a pulsed infrared laser beam and the SHG signal is monitored in reflection. For metallic silver, the SHG signal is found to be temperature dependent in the 25-120 degrees C range. The current accuracy of the method is +/-5 degrees C. Future work with platinum should permit the application of SHG thermometry to much higher surface temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3675869','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3675869"><span id="translatedtitle">Chiral imaging of collagen by second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> circular dichroism</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lee, H.; Huttunen, M. J.; Hsu, K.-J.; Partanen, M.; Zhuo, G.-Y.; Kauranen, M.; Chu, S.-W.</p> <p>2013-01-01</p> <p>We provide evidence that the chirality of collagen can give rise to strong second-<span class="hlt">harmonic</span> <span class="hlt">generation</span> circular dichroism (SHG-CD) responses in nonlinear microscopy. Although chirality is an intrinsic structural property of collagen, most of the previous studies ignore that property. We demonstrate chiral imaging of individual collagen fibers by using a laser scanning microscope and type-I collagen from pig ligaments. 100% contrast level of SHG-CD is achieved with sub-micrometer spatial resolution. As a new contrast mechanism for imaging chiral structures in bio-tissues, this technique provides information about collagen morphology and three-dimensional orientation of collagen molecules. PMID:23761852</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10171934','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10171934"><span id="translatedtitle">A superconducting short period undulator for a <span class="hlt">harmonic</span> <span class="hlt">generation</span> FEL experiment</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ingold, G.; Solomon, L.; Ben-Zvi, I.; Krinsky, S.; Li, D.; Lynch, D.; Sheehan, J.; Woodle, M.; Qiu, X.Z.; Yu, L.H.; Zhang, X.; Sampson, W.; Gardner, M.; Robins, K.; Lehrman, I.; Heuer, R.; Sheehan, J.; Weissenburger, D.</p> <p>1993-07-01</p> <p>A three stage superconducting (SC) undulator for a high gain <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HGE) FEL experiment in the infrared is under construction at the NSLS in collaboration with Grumman Corporation. A novel undulator technology suitable for short period (6--40mm) undulators will be employed for all three stages, the modulator, the dispersive section and the radiator. The undulator triples the frequency of a 10.4{mu}m CO{sub 2} seed laser. So far a 27 period (one third of the final radiator) prototype radiator has been designed, built and tested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6121901','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6121901"><span id="translatedtitle">A superconducting short period undulator for a <span class="hlt">harmonic</span> <span class="hlt">generation</span> FEL experiment</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ingold, G.; Solomon, L.; Ben-Zvi, I.; Krinsky, S.; Li, D.; Lynch, D.; Sheehan, J.; Woodle, M.; Qiu, X.Z.; Yu, L.H.; Zhang, X.; Sampson, W.; Gardner, M.; Robins, K. ); Lehrman, I.; Heuer, R.; Sheehan, J.; Weissenburger, D. )</p> <p>1993-01-01</p> <p>A three stage superconducting (SC) undulator for a high gain <span class="hlt">harmonic</span> <span class="hlt">generation</span> (HGE) FEL experiment in the infrared is under construction at the NSLS in collaboration with Grumman Corporation. A novel undulator technology suitable for short period (6--40mm) undulators will be employed for all three stages, the modulator, the dispersive section and the radiator. The undulator triples the frequency of a 10.4[mu]m CO[sub 2] seed laser. So far a 27 period (one third of the final radiator) prototype radiator has been designed, built and tested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15009558','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15009558"><span id="translatedtitle">EXPERIMENTAL DEMONSTRATION OF WAVELENGTH TUNING IN HIGH-GAIN <span class="hlt">HARMONIC</span> <span class="hlt">GENERATION</span> FREE ELECTRON LASER.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>SHAFTAN,T.; JOHNSON,E.; KRINSKY,S.; LOOS,H.; MURPHY,J.B.; RAKOWSKY,G.; ROSE,J.; SHEEHY,B.; SKARITKA,J.; WANG,X.J.; WU,Z.; YU,L.H.</p> <p>2004-08-29</p> <p>Tunability is one of the key aspects of any laser system. In High-Gain <span class="hlt">Harmonic</span> <span class="hlt">Generation</span> Free Electron Laser (HGHG FEL) the seed laser determines the output wavelength. Conventional scheme of tunable HGHG FEL requires tunable seed laser. The alternative scheme [1] is based on compression of the electron bunch with energy-time correlation (chirped bunch) in the FEL dispersive section. The chirped energy modulation, induced by the seed laser with constant wavelength, compressed as the whole bunch undergoes compression. In this paper we discuss experimental verification of the proposed approach at the DUV FEL [2,3] and compare experimental results with analytical estimates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3493243','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3493243"><span id="translatedtitle">Imaging morphodynamics of human blood cells in vivo with video-rate third <span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Chen, Chien-Kuo; Liu, Tzu-Ming</p> <p>2012-01-01</p> <p>With a video-rate third <span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) microscopy system, we imaged the micro-circulation beneath the human skin without labeling. Not only the speed of circulation but also the morpho-hydrodynamics of blood cells can be analyzed. Lacking of nuclei, red blood cells (RBCs) shows typical parachute-like and hollow-core morphology under THG microscopy. Quite different from RBCs, every now and then, round and granule rich blood cells with strong THG contrast appear in circulation. The corresponding volume densities in blood, evaluated from their frequencies of appearance and the velocity of circulation, fall within the physiological range of human white blood cell counts. PMID:23162724</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23162724','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23162724"><span id="translatedtitle">Imaging morphodynamics of human blood cells in vivo with video-rate third <span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Chien-Kuo; Liu, Tzu-Ming</p> <p>2012-11-01</p> <p>With a video-rate third <span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) microscopy system, we imaged the micro-circulation beneath the human skin without labeling. Not only the speed of circulation but also the morpho-hydrodynamics of blood cells can be analyzed. Lacking of nuclei, red blood cells (RBCs) shows typical parachute-like and hollow-core morphology under THG microscopy. Quite different from RBCs, every now and then, round and granule rich blood cells with strong THG contrast appear in circulation. The corresponding volume densities in blood, evaluated from their frequencies of appearance and the velocity of circulation, fall within the physiological range of human white blood cell counts. PMID:23162724</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4871089','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4871089"><span id="translatedtitle">Third <span class="hlt">harmonic</span> <span class="hlt">generation</span> imaging for fast, label-free pathology of human brain tumors</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kuzmin, N. V.; Wesseling, P.; Hamer, P. C. de Witt; Noske, D. P.; Galgano, G. D.; Mansvelder, H. D.; Baayen, J. C.; Groot, M. L.</p> <p>2016-01-01</p> <p>In brain tumor surgery, recognition of tumor boundaries is key. However, intraoperative assessment of tumor boundaries by the neurosurgeon is difficult. Therefore, there is an urgent need for tools that provide the neurosurgeon with pathological information during the operation. We show that third <span class="hlt">harmonic</span> <span class="hlt">generation</span> (THG) microscopy provides label-free, real-time images of histopathological quality; increased cellularity, nuclear pleomorphism, and rarefaction of neuropil in fresh, unstained human brain tissue could be clearly recognized. We further demonstrate THG images taken with a GRIN objective, as a step toward in situ THG microendoscopy of tumor boundaries. THG imaging is thus a promising tool for optical biopsies. PMID:27231629</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20640355','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20640355"><span id="translatedtitle">Ionization and high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> in aligned benzene by a short intense circularly polarized laser pulse</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Baer, Roi; Neuhauser, Daniel; Zdanska, Petra R.; Moiseyev, Nimrod</p> <p>2003-10-01</p> <p>We present a first-principles study of ionization and high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> by benzene aligned in the polarization plane of a short circularly polarized laser pulse. Time-dependent density-functional theory within the adiabatic local-density approximation is employed to describe the 30 valence-electron dynamics in three dimensions. The multielectron approach enables us to study the effect of very strong laser fields, 10{sup 14}-10{sup 15} W cm{sup -2}, where multiple ionization and high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> interplay. Large ionization currents are formed, causing ionization of 1-4 electron charges, while strong high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> is observed. The well-known recollision mechanism of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> plays a part for moderate laser intensities but is fully suppressed for strong laser fields. The <span class="hlt">harmonic</span> <span class="hlt">generation</span> spectra are characterized by two distinguishable plateaus, where the structure of the first plateau is dominated by the 6k{+-}1 (k=0,1,...) selection rule. The number of <span class="hlt">harmonics</span> in the second plateau is insensitive to the duration of the pulse. The peaks appear in pairs or in threesomes, depending on the pulse duration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4455065','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4455065"><span id="translatedtitle">Dynamical origin of near- and below-threshold <span class="hlt">harmonic</span> <span class="hlt">generation</span> of Cs in an intense mid-infrared laser field</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Li, Peng-Cheng; Sheu, Yae-Lin; Laughlin, Cecil; Chu, Shih-I</p> <p>2015-01-01</p> <p>Near- and below-threshold <span class="hlt">harmonic</span> <span class="hlt">generation</span> provides a potential approach to <span class="hlt">generate</span> vacuum-ultraviolet frequency comb. However, the dynamical origin of in these lower <span class="hlt">harmonics</span> is less understood and largely unexplored. Here we perform an ab initio quantum study of the near- and below-threshold <span class="hlt">harmonic</span> <span class="hlt">generation</span> of caesium (Cs) atoms in an intense 3,600-nm mid-infrared laser field. Combining with a synchrosqueezing transform of the quantum time-frequency spectrum and an extended semiclassical analysis, the roles of multiphoton and multiple rescattering trajectories on the near- and below-threshold <span class="hlt">harmonic</span> <span class="hlt">generation</span> processes are clarified. We find that the multiphoton-dominated trajectories only involve the electrons scattered off the higher part of the combined atom-field potential followed by the absorption of many photons in near- and below-threshold regime. Furthermore, only the near-resonant below-threshold <span class="hlt">harmonic</span> is exclusive to exhibit phase locked features. Our results shed light on the dynamic origin of the near- and below-threshold <span class="hlt">harmonic</span> <span class="hlt">generation</span>. PMID:25990452</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20640232','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20640232"><span id="translatedtitle">Phase-matching analysis of high-order <span class="hlt">harmonics</span> <span class="hlt">generated</span> by truncated Bessel beams in the sub-10-fs regime</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Altucci, C.; Bruzzese, R.; De Lisio, C.; Nisoli, M.; Priori, E.; Stagira, S.; Pascolini, M.; Poletto, L.; Villoresi, P.; Tosa, V.; Midorikawa, K.</p> <p>2003-09-01</p> <p>We describe a very simple physical model that allows the analysis of high-order <span class="hlt">harmonic</span> <span class="hlt">generation</span> in gases when the pumping laser beam has an intensity profile that is not Gaussian but truncated Bessel. This is the typical experimental condition when sub-10-fs pump-laser pulses, <span class="hlt">generated</span> by the hollow fiber compression technique, are used. This model is based on the analysis of the phase-matching conditions for the <span class="hlt">harmonic</span> <span class="hlt">generation</span> process revisited in view of the new spatial mode of the fundamental beam. In particular, the role of the atomic dipole phase and the geometric phase terms are evidenced both for <span class="hlt">harmonics</span> <span class="hlt">generated</span> in the plateau and in the cutoff spectral regions. The influence of dispersion introduced by free electrons produced by laser ionization has also been discussed in some detail. Spatial patterns of far-field <span class="hlt">harmonics</span> are then obtained by means of a simplified algorithm which allows one to avoid the numerical integration of the <span class="hlt">harmonic</span> beam propagation equation. Experimental spatial distributions and divergence angles of high-order <span class="hlt">harmonics</span> <span class="hlt">generated</span> in Ne with 7-fs titanium-sapphire pulses are compared with numerical simulations in various experimental conditions. The agreement between measurements and calculated results is found to be very satisfactory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25363416','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25363416"><span id="translatedtitle">Polarization second <span class="hlt">harmonic</span> <span class="hlt">generation</span> microscopy provides quantitative enhanced molecular specificity for tissue diagnostics.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kumar, Rajesh; Grønhaug, Kirsten M; Romijn, Elisabeth I; Finnøy, Andreas; Davies, Catharina L; Drogset, Jon O; Lilledahl, Magnus B</p> <p>2015-09-01</p> <p>Due to specific structural organization at the molecular level, several biomolecules (e.g., collagen, myosin etc.) which are strong <span class="hlt">generators</span> of second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (SHG) signals, exhibit unique responses depending on the polarization of the excitation light. By using the polarization second <span class="hlt">harmonic</span> <span class="hlt">generation</span> (p-SHG) technique, the values of the second order susceptibility components can be used to differentiate the types of molecule, which cannot be done by the use of a standard SHG intensity image. In this report we discuss how to implement p-SHG on a commercial multiphoton microscope and overcome potential artifacts in susceptibility (χ) image. Furthermore we explore the potential of p-SHG microscopy by applying the technique to different types of tissue in order to determine corresponding reference values of the ratio of second-order χ tensor elements. These values may be used as a bio-marker to detect any structural alterations in pathological tissue for diagnostic purposes. The SHG intensity image (red) in (a) shows the distribution of collagen fibers in ovary tissue but cannot determine the type of collagen fiber. However, the histogram distribution (b) for the values of the χ tensor element ratio can be used to quantitatively identify the types of collagen fibers.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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