Sample records for fs cascaded second-harmonic

  1. Optical Cherenkov radiation in ultrafast cascaded second-harmonic generation

    NASA Astrophysics Data System (ADS)

    Bache, M.; Bang, O.; Zhou, B. B.; Moses, J.; Wise, F. W.


    We show through theory and numerics that when few-cycle femtosecond solitons are generated through cascaded (phase-mismatched) second-harmonic generation, 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 generates 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 generated 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 generation mechanism of long-wavelength radiation that can occur during soliton compression. We discuss the conditions that lead to this alternative dynamics rather than generation of Cherenkov radiation.

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


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


    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. PMID:25089458

  3. Resonant cascaded surface-emitting second-harmonic generation: a strong third-order nonlinear process.


    Khurgin, J B; Ding, Y J


    A novel practical scheme for implementation of the cascaded nonlinearity with surface-emitting second-harmonic generation in the Fabry-Perot cavity is presented. We show that such a scheme can be efficiently used for optical limiting and optical phase conjugation at a pump power of lessthan 100 mW. PMID:19844518

  4. Genetic algorithm applied to the optimization of quantum cascade lasers with second harmonic generation

    SciTech Connect

    Gajić, A.; Radovanović, J. Milanović, V.; Indjin, D.; Ikonić, Z.


    A computational model for the optimization of the second order optical nonlinearities in GaInAs/AlInAs quantum cascade laser structures is presented. The set of structure parameters that lead to improved device performance was obtained through the implementation of the Genetic Algorithm. In the following step, the linear and second harmonic generation power were calculated by self-consistently solving the system of rate equations for carriers and photons. This rate equation system included both stimulated and simultaneous double photon absorption processes that occur between the levels relevant for second harmonic generation, and material-dependent effective mass, as well as band nonparabolicity, were taken into account. The developed method is general, in the sense that it can be applied to any higher order effect, which requires the photon density equation to be included. Specifically, we have addressed the optimization of the active region of a double quantum well In{sub 0.53}Ga{sub 0.47}As/Al{sub 0.48}In{sub 0.52}As structure and presented its output characteristics.

  5. Walk off compensation, multicrystal, cascaded, single pass, second harmonic generation in LBO

    NASA Astrophysics Data System (ADS)

    Ji, B.; Zheng, X. S.; Cai, Z. P.; Xu, H. Y.; Jia, F. Q.


    Walk off compensation and multi crystal (MC) cascaded single pass second harmonic generation (SP-SHG) in LBO was combined to improve the SHG conversion efficiency. We report a simple and compact implementation for (SP-SHG) of radiation, based on a cascaded multicrystal (MC) scheme that can provide high conversion efficiency without other focusing device, the enhancement factor of 2.9 was realized. At an incident pump power of 20 W, the average power of 6.1 W and pulse width of 12 ns green laser was obtained at a repetition rate of 42.4 kHz, corresponding to a peak power of 12 kW and single pulse energy of 144 μJ. The optical to optical conversion efficiency from diode to green and from IR to green laser are about 30.5 and 67.8%, the whole length of this system is about 150 mm, the output fluctuation of this system is less than 5% in 2 h.

  6. Temporal contrast enhancement for optical parametric chirped-pulse amplifiers by adopting cascaded second harmonic generation pump

    NASA Astrophysics Data System (ADS)

    Deng, Qinghua; Zeng, Xiaoming; Jiang, Dongbin; Xie, Na; Zhou, Kainan; Wang, Xuemin; Li, Weihua; Wu, Weidong; Ding, Lei


    We report on a method to enhance the temporal contrast of optical parametric chirped-pulse amplifiers (OPCPAs) by smoothing pump noise. The instantaneous parametric gain in OPCPA couples the temporal modulation on the pump pulses to spectral variations of the intensity of the stretched signal pulses being amplified. In this way, pump noise significantly degrades the temporal contrast of the amplified pulses after recompression. Cascaded second harmonic generation (SHG) is adopted to smooth modulation on the pump pulses in the proposed method. Apparent reduction of modulation on the pump pulses is observed in the experiments. Numerical simulation reproduces the experimental results. Simulation results show that cascaded SHG with stable output 2 ω can enhance the temporal contrast for OPCPAs with four to five orders. It is believed that this new method can be widely adopted to build high-contrast OPCPA systems.

  7. Broadband wavelength converters with flattop responses based on cascaded second-harmonic generation and difference frequency generation in Bessel-chirped gratings.


    Liu, Tao; Djordjevic, Ivan B; Song, Zekun; Chen, Ying; Zhang, Rongxiang; Zhang, Ke; Zhao, Wei; Li, Baogang


    We investigate ultra-broadband wavelength converters based on cascaded second-harmonic generation and difference frequency generation using Bessel-chirped gratings (BCGs) in lithium niobate waveguides, and compare them to the ones using uniform grating and segmented grating, respectively. For the same length and power, the BCGs show broader bandwidth than the other two types of grating. The ripple of the matching response is very small as well. Analysis also shows that almost the same conversion bandwidth and maximum conversion efficiency with tolerant response flatness can be achieved when the manufacturing tolerance of the waveguide length is smaller than 0.1 cm. PMID:27409916

  8. Second harmonic FEL oscillation

    NASA Astrophysics Data System (ADS)

    Neil, George R.; Benson, S. V.; Biallas, G.; Freund, H. P.; Gubeli, J.; Jordan, K.; Myers, S.; Shinn, M. D.


    We have produced and measured for the first time second harmonic oscillation in the infrared region by the high-average-power Jefferson Lab Infrared Free Electron Laser. The finite geometry and beam emittance allows sufficient gain for lasing to occur. We were able to lase at pulse rates up to 74.85 MHz and could produce over 4.5 W average and 40 kW peak of IR power in a 40 nm FWHM bandwidth at 2925 nm. In agreement with predictions, the source preferentially lased in a TEM 01 mode. We present results of initial source performance measurements and comparisons with theory and simulation.

  9. Second Harmonic FEL Oscillation

    NASA Astrophysics Data System (ADS)

    Neil, George R.; Benson, S. V.; Biallas, G.; Gubeli, J.; Jordan, K.; Myers, S.; Shinn, M. D.


    We have produced and measured for the first time second harmonic oscillation in the infrared region by a free electron laser. Although such lasing is ideally forbidden, since the gain of a plane wave is zero on axis for an electron beam perfectly aligned with a wiggler, a transverse mode antisymmetry allows sufficient gain in this experiment for lasing to occur. We lased at pulse rates up to 74.85 MHz and could produce over 4.5 W average and 40 kW peak of IR power in a 40 nm FWHM bandwidth at 2925 nm. In agreement with predictions, the source preferentially lased in a TEM01 mode.


    SciTech Connect

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


    Second harmonic generation at a silver-air interface was enhanced due to surface roughness by a factor of 10{sup 4}. 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.

  11. Resonance Thirring solitons in type II second-harmonic generation

    NASA Astrophysics Data System (ADS)

    Trillo, Stefano


    It is shown that second-harmonic generation in a grating allows one to cancel the group-velocity difference between two polarization components at fundamental by means of nonlinearly induced phase shifts. This occurs when a new type of cascading soliton propagates on resonance.

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

    SciTech Connect

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


    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.

  13. Discrete quadratic solitons with competing second-harmonic components

    SciTech Connect

    Setzpfandt, Frank; Pertsch, Thomas; Sukhorukov, Andrey A.


    We describe families of discrete solitons in quadratic waveguide arrays supported by competing cascaded nonlinear interactions between one fundamental and two second-harmonic modes. We characterize the existence, stability, and excitation dynamics of these solitons and show that their features may resemble those of solitons in saturable media. Our results also demonstrate that a power threshold may appear for soliton formation, leading to a suppression of beam self-focusing which explains recent experimental observations.

  14. Organometallic Salts Generate Optical Second Harmonics

    NASA Technical Reports Server (NTRS)

    Marder, Seth R.; Perry, Joseph W.


    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.

  15. Imaging with Second-Harmonic Generation Nanoparticles

    NASA Astrophysics Data System (ADS)

    Hsieh, Chia-Lung

    Second-harmonic generation nanoparticles show promise as imaging probes due to their coherent and stable signal with a broad flexibility in the choice of excitation wavelength. In this thesis, we developed and demonstrated barium titanate nanoparticles as second-harmonic radiation imaging probes. We studied the absolute second-harmonic generation efficiency of the nanoparticles on single-particle level. The polarization dependent second-harmonic signal of single nanoparticles was studied in detail. From the measured polar response, we were able to find the orientation of the nanoparticle. We developed a biochemical interface for using the second-harmonic nanoprobes as biomarkers, including in vitro cellular imaging and in vivo live animal imaging. The nanoparticles were surface functionalized with primary amine groups for stable colloidal dispersion. We achieved specific labeling of the second-harmonic nanoprobes via immunostaining where the antibodies were covalently conjugated onto the nanoparticles. We observed no toxicity of the functionalized nanoparticles to biological cells. The coherent second-harmonic signal radiated from the nanoparticles offers opportunities for new imaging techniques. Using interferometric detection, namely harmonic holography, both amplitude and phase of the second-harmonic field can be captured. Through digital beam propagation, three-dimensional field distribution, reflecting three-dimensional distribution of the nanoparticles, can be reconstructed. We achieved a scan-free three-dimensional imaging of nanoparticles in biological cells with sub-micron spatial resolution by using the harmonic holographic microscope. We further exploited the coherent second-harmonic signal for imaging through scattering media by performing optical phase conjugation of the second-harmonic signal. We demonstrated an all-digital optical phase conjugation of the second-harmonic signal originated from a nanoparticle by combining harmonic holography and

  16. Second harmonic generation and sum frequency generation

    SciTech Connect

    Pellin, M.J.; Biwer, B.M.; Schauer, M.W.; Frye, J.M.; Gruen, D.M.


    Second harmonic generation and sum frequency generation are increasingly being used as in situ surface probes. These techniques are coherent and inherently surface sensitive by the nature of the mediums response to intense laser light. Here we will review these two techniques using aqueous corrosion as an example problem. Aqueous corrosion of technologically important materials such as Fe, Ni and Cr proceeds from a reduced metal surface with layer by layer growth of oxide films mitigated by compositional changes in the chemical makeup of the growing film. Passivation of the metal surface is achieved after growth of only a few tens of atomic layers of metal oxide. Surface Second Harmonic Generation and a related nonlinear laser technique, Sum Frequency Generation have demonstrated an ability to probe the surface composition of growing films even in the presence of aqueous solutions. 96 refs., 4 figs.

  17. Possible second harmonic gyroemission at Uranus

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Curran, D. B.


    During the inbound trajectory toward Uranus, the Planetary Radio Astronomy Instrument on board the Voyager 2 spacecraft observed narrow-band smooth (n-smooth) emission at frequencies centered near 60 kHz. By assuming models of the plasma density for the dayside magnetosphere of Uranus and by using cold plasma theory together with stringent observational constraints, ray-tracing calculations were performed to determine the source location and mode of the n-smooth emission. Ray-tracing calculations suggest that the n-smooth emission with sources near the magnetic equator may be fundamental X mode for certain conditions or second harmonic gyroemission. If the emission is second harmonic gyroemission, the fundamental emission at 30 kHz is expected but apparently not observed. These findings are discussed in the context of the most recent developments in the theory of the cyclotron maser instability.

  18. Fast interferometric second harmonic generation microscopy

    PubMed Central

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


    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

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

    SciTech Connect

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


    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-handed circular, linear, and right-handed circular polarizations, respectively.

  20. Cascaded second-harmonic generation, summation of the wave vectors of the bulk defect-deformation waves, and generation of multimode micro- and nanostructures by laser irradiation of solids

    SciTech Connect

    Emel'yanov, Vladimir I


    We consider for the first time three-wave interactions of bulk quasi-static defect-deformation (DD) waves (generation of the second DD harmonic and summation of the wave vectors), similar to three-wave interactions in nonlinear optics and acoustics, leading to cascaded broadening of the spectrum of spatial DD harmonics. Based on the theory developed, we interpret the recently observed effect of laser-induced generation of the bulk periodic structure of silver nanoparticles with a discrete spatial spectrum, extending from micro- to nanometres. (nonlinear optical phenomena)

  1. Cascaded second-harmonic generation, summation of the wave vectors of the bulk defect-deformation waves, and generation of multimode micro- and nanostructures by laser irradiation of solids

    NASA Astrophysics Data System (ADS)

    Emel'yanov, Vladimir I.


    We consider for the first time three-wave interactions of bulk quasi-static defect-deformation (DD) waves (generation of the second DD harmonic and summation of the wave vectors), similar to three-wave interactions in nonlinear optics and acoustics, leading to cascaded broadening of the spectrum of spatial DD harmonics. Based on the theory developed, we interpret the recently observed effect of laser-induced generation of the bulk periodic structure of silver nanoparticles with a discrete spatial spectrum, extending from micro- to nanometres.

  2. Generating Second Harmonics In Nonlinear Resonant Cavities

    NASA Technical Reports Server (NTRS)

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


    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.

  3. Promoting Spontaneous Second Harmonic Generation through Organogelation.


    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


    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

  4. The IPNS second harmonic RF upgrade.

    SciTech Connect

    Middendorf, M. E.; Brumwell, F. R.; Dooling, J. C.; Horan, D.; Kustom, R. L.; Lien, M. K.; McMichael, G. E.; Moser, M. R.; Nassiri, A.; Wang, S.; Accelerator Systems Division


    The intense pulsed neutron source (IPNS) rapid cycling synchrotron (RCS) is used to accelerate protons from 50 MeV to 450 MeV, at a repetition rate of 30 Hz. The original ring design included two identical rf systems, each consisting of an accelerating cavity, cavity bias supply, power amplifiers and low-level analog electronics. The original cavities are located 180 degrees apart in the ring and provide a total peak accelerating voltage of {approx}21 kV over the 2.21-MHz to 5.14-MHz revolution frequency sweep. A third rf system has been constructed and installed in the RCS. The third rf system is capable of operating at the fundamental revolution frequency for the entire acceleration cycle, providing an additional peak accelerating voltage of up to {approx}11 kV, or at the second harmonic of the revolution frequency for the first {approx}4 ms of the acceleration cycle, providing an additional peak voltage of up to {approx}11 kV for bunch shape control. We describe here the hardware implementation and operation to date of the third rf cavity in the second harmonic mode.

  5. Transient regime in second harmonic generation

    NASA Astrophysics Data System (ADS)

    Szeftel, Jacob; Sandeau, Laure; Sandeau, Nicolas; Delezoide, Camille; Khater, Antoine


    The time growth of the electromagnetic field at the fundamental and double frequencies is studied from the very onset of the second harmonic generation (SHG) process for a set of dipoles lacking a symmetry centre and exhibiting a nonresonant coupling with a classical electromagnetic field. This approach consists first of solving the Schrödinger equation by applying a generalised Rabi rotation to the Hamiltonian describing the light-dipole interaction. This rotation has been devised for the resulting Hamiltonian to show up time-independent for both components of the electromagnetic field at the fundamental frequency and the second harmonic one. Then an energy conservation argument, derived from the Poynting theorem, is introduced to work out an additional relationship between the electromagnetic field and its associated electric polarisation. Finally this analysis yields the full time behaviour of all physical quantities of interest. The calculated results reproduce accurately both the observed spatial oscillations of the SHG intensity (Maker's fringes) and its power law dependence on the intensity of the incoming light at the fundamental frequency.

  6. Lens-less surface second harmonic imaging.


    Sly, Krystal L; Nguyen, Trang T; Conboy, John C


    Lens-less surface second harmonic generation imaging (SSHGI) is used to image an SHG active molecule, (S)-(+)-1,1'-bi-2-naphthol (SBN), incorporated into a lipid bilayer patterned with the 1951 United States Air Force resolution test target. Data show the coherent plane-wave nature of SHG allows direct imaging without the aid of a lens system. Lens-less SSHGI readily resolves line-widths as small as 223 μm at an object-image distance of 7.6 cm and line-widths of 397 μm at distances as far as 30 cm. Lens-less SSHGI simplifies the detection method, raises photon collection efficiency, and expands the field-of-view. These advantages allow greater throughput and make lens-less SSHGI a potentially valuable detection method for biosensors and medical diagnostics. PMID:23037346

  7. 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

  8. Effects of spatial transverse correlations in second-harmonic generation

    SciTech Connect

    Ether, D. S.; Souto Ribeiro, P. H.; Matos Filho, R. L. de; Monken, C. H.


    Second-harmonic generation is studied for the case where the fundamental field is light produced in a spontaneous parametric down-conversion process. We show that second-harmonic generation is sensitive to the transverse correlations between signal and idler fields. In particular, when the fundamental is prepared in a state exhibitting spatial antibunching, the second-harmonic intensity may be zero, independent of the intensity of the fundamental field.

  9. Second harmonic generation polarization properties of myofilaments

    NASA Astrophysics Data System (ADS)

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


    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.

  10. The polarization of second harmonic plasma emission

    NASA Technical Reports Server (NTRS)

    Melrose, D. B.; Dulk, G. A.; Smerd, S. F.


    It is shown that second-harmonic plasma emission is partially polarized in the sense of the ordinary mode of magnetoionic theory only when the Langmuir waves are confined to a small range of angles (less than 30 deg) to the magnetic-field lines. Consequently, Suzuki and Sheridan's (1977) observations of the polarization of harmonic Type III emission implies that (at least in the cases reported) the Langmuir waves must be nearly one-dimensional. For a nearly one-dimensional distribution, the degree of polarization and the frequency of observation should be related to the magnetic field. For the observed polarization of Type III bursts, the implied magnetic-field strengths are strong enough for induced scattering to cause the Langmuir waves to become nearly one-dimensional, which is consistent with the observed sense of polarization. In other applications of harmonic plasma emission where the Langmuir waves might be isotropic or in a loss-cone distribution, polarization in the sense of the extraordinary mode is predicted.

  11. Digital holography for second harmonic microscopy

    NASA Astrophysics Data System (ADS)

    Shaffer, E.; Depeursinge, C.


    Quantitative phase images make digital holographic microscopy (DHM) an excellent instrument for metrological, but also for biological applications, where it can reveal deformations and morphological details at ultrahigh resolution in the order of a few nanometers only, while also precisely determining the refractive index across a sample (e.g. cell or neuron). On the other hand, non-linear light-matter interactions have also proved very useful in microscopy. For instance, second harmonic generation (SHG) allows marker-free identification of cell structures, tubulin or membranes and, because of its coherent nature, SHG is very sensitive to the local sample structure and to the direction of the laser polarization. In addition, since SHG does not result from light absorption and subsequent re-emission, in opposition to fluorescence, photo-bleaching of the studied material can be avoided by a judicious selection of the laser wavelength. These characteristics make SHG very interesting for biomedical imaging. We have designed and built a microscope that combines the fast and precise DHM imaging with tagging capabilities of non-linear light-matter interactions. Here, we present the technique and look into its possible applications to biological and life sciences. Among promising applications is the 3D tracking of colloidal gold nanoparticles.

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


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


    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. PMID:25995840

  13. Powders Analysis by Second Harmonic Generation Microscopy.


    Chowdhury, Azhad U; Zhang, Shijie; Simpson, Garth J


    A microscopy approach is developed for quantifying second harmonic generation (SHG) activity of powders that largely decouples linear and nonlinear optical interactions. Decoupling the linear and nonlinear optical effects provides a means to independently evaluate and optimize the role of each in crystal engineering efforts and facilitates direct comparisons between experimental and computational predictions of lattice hyperpolarizabilities. In this respect, the microscopy-based approach nicely complements well-established Kurtz-Perry ( J. Appl. Phys. 1968 , 39 , 3798 ) and related methods, in which collimated sources are used for powders analysis. Using a focused fundamental beam places a controllable upper bound on the interaction length, given by the depth of field. Because measurements are performed on a per-particle basis, crystal size-dependent trends can be recovered from a single powdered sample. An analytical model that includes scattering losses of a focused Gaussian beam reliably predicted several experimental observations. Specifically, the measured scattering length for SHG was in excellent agreement with the value predicted based on the particle size distribution. Additionally, histograms of the SHG intensities as functions of particle size and orientation agreed nicely with predictions from the model. PMID:26929984

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

    NASA Astrophysics Data System (ADS)

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


    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. The measured harmonic-generation efficiencies are 2.6·10-9, 8·10-9 and 1.3·10-8 for left-handed circular, linear, and right-handed circular polarizations, respectively. The uncoated nanospirals are stable under average power loading of as much as 300 μWper nanoparticle. The nanospirals also exhibit selective conversion between polarization states. These experiments show that the intrinsic asymmetry of the nanospirals results in a highly efficient, two-dimensional harmonic generator that can be incorporated into metasurface optics.

  15. Second-harmonic generation in substoichiometric silicon nitride layers

    NASA Astrophysics Data System (ADS)

    Pecora, Emanuele; Capretti, Antonio; Miano, Giovanni; Dal Negro, Luca


    Harmonic generation in optical circuits offers the possibility to integrate wavelength converters, light amplifiers, lasers, and multiple optical signal processing devices with electronic components. Bulk silicon has a negligible second-order nonlinear optical susceptibility owing to its crystal centrosymmetry. Silicon nitride has its place in the microelectronic industry as an insulator and chemical barrier. In this work, we propose to take advantage of silicon excess in silicon nitride to increase the Second Harmonic Generation (SHG) efficiency. Thin films have been grown by reactive magnetron sputtering and their nonlinear optical properties have been studied by femtosecond pumping over a wide range of excitation wavelengths, silicon nitride stoichiometry and thermal processes. We demonstrate SHG in the visible range (375 - 450 nm) using a tunable 150 fs Ti:sapphire laser, and we optimize the SH emission at a silicon excess of 46 at.% demonstrating a maximum SHG efficiency of 4x10-6 in optimized films. Polarization properties, generation efficiency, and the second order nonlinear optical susceptibility are measured for all the investigated samples and discussed in terms of an effective theoretical model. Our findings show that the large nonlinear optical response demonstrated in optimized Si-rich silicon nitride materials can be utilized for the engineering of nonlinear optical functions and devices on a Si chip.

  16. Dual aperture dipole magnet with second harmonic component


    Praeg, W.F.


    An improved dual aperture dipole electromagnet includes a second-harmonic frequency magnetic guide field winding which surrounds first harmonic frequency magnetic guide field windings associated with each aperture. The second harmonic winding and the first harmonic windings cooperate to produce resultant magnetic waveforms in the apertures which have extended acceleration and shortened reset portions of electromagnet operation.

  17. Dual aperture dipole magnet with second harmonic component


    Praeg, Walter F.


    An improved dual aperture dipole electromagnet includes a second-harmonic frequency magnetic guide field winding which surrounds first harmonic frequency magnetic guide field windings associated with each aperture. The second harmonic winding and the first harmonic windings cooperate to produce resultant magnetic waveforms in the apertures which have extended acceleration and shortened reset portions of electromagnet operation.

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

    SciTech Connect

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


    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.

  19. 34 GHz second-harmonic peniotron oscillator

    NASA Astrophysics Data System (ADS)

    Dressman, Lawrence Jude

    Harmonic operation of gyro-devices has been proposed as a way to lower the magnetic field required to a level feasible with normal (i.e., non-superconducting) magnets. The problem is, however, that gyrotron efficiency drops dramatically at harmonics greater than two, making development of such a device of limited utility. A promising solution to this quandary is the development of a related device, the peniotron, which is believed capable of achieving both high efficiency and harmonic operation resulting in a reduction of the required axial magnetic field. Although the physics of the peniotron interaction, including its high electronic conversion efficiency, has been understood and experimentally verified, demonstration of characteristics consistent with a practical device has been more elusive. This is the goal of this effort---specifically, to demonstrate high device efficiency (defined as the actual power output as a fraction of the electron beam power) with an electron beam generated by a compact cusp electron gun consistent in size and performance with other microwave vacuum electron devices. The cavity design process revealed that the pi/2 mode couples easily to the output circular waveguide. In fact, the transition to circular waveguide produced such a low reflection coefficient that an iris was needed at the cavity output to achieve the desired Q. Integral couplers were also designed to couple directly into the slotted cavity for diagnostic purposes for simplicity in this proof-of-principle physics experiment. This eliminated the need for a high-power circular vacuum window and allowed the diagnostic coupling to be made in standard WR-28 rectangular waveguide. Although mode competition did prevent the second-harmonic peniotron mode from being tuned over its entire range of magnetic field, the peniotron mode was stable over a range sufficient to allow useful experimental data to be obtained. However, another unexpected problem which occurred during execution

  20. Vectorial second-harmonic magneto-optic Kerr effect measurements

    NASA Astrophysics Data System (ADS)

    Kabos, P.; Kos, A. B.; Silva, T. J.


    A significant modification of an existing experimental technique based on the second-harmonic magneto-optical Kerr effect (SH-MOKE) is introduced. With a p-polarized pumping optical wave incident upon a magnetic film, the transverse component of magnetization causes a change in the second-harmonic generation efficiency of the material and the longitudinal component of the magnetization produces a change in the polarization rotation and/or ellipticity of the second-harmonic signal. This permits simultaneous vectorial measurement of the in-plane magnetization components. Examples of measured hysteresis loops from 50 nm thick permalloy films and procedures for SH-MOKE signal calibration are presented.


    SciTech Connect

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


    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,

  2. Hyperbolic metamaterial antenna for second-harmonic generation tomography.


    Segovia, Paulina; Marino, Giuseppe; Krasavin, Alexey V; Olivier, Nicolas; Wurtz, Gregory A; Belov, Pavel A; Ginzburg, Pavel; Zayats, Anatoly V


    The detection and processing of information carried by evanescent field components are key elements for subwavelength optical microscopy as well as single molecule sensing applications. Here, we numerically demonstrate the potential of a hyperbolic medium in the design of an efficient metamaterial antenna enabling detection and tracking of a nonlinear object, with an otherwise hidden second-harmonic signature. The presence of the antenna provides 103-fold intensity enhancement of the second harmonic generation (SHG) from a nanoparticle through a metamaterial-assisted access to evanescent second-harmonic fields. Alternatively, the observation of SHG from the metamaterial itself can be used to detect and track a nanoparticle without a nonlinear response. The antenna allows an optical resolution of several nanometers in tracking the nanoparticle's location via observations of the far-field second-harmonic radiation pattern. PMID:26698705

  3. Nonlinearly coupled localized plasmon resonances: Resonant second-harmonic generation

    NASA Astrophysics Data System (ADS)

    Ginzburg, Pavel; Krasavin, Alexey; Sonnefraud, Yannick; Murphy, Antony; Pollard, Robert J.; Maier, Stefan A.; Zayats, Anatoly V.


    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-harmonic modes is shown to be symmetry selective and proportional to the spatial overlap between polarization dipole density of the second-harmonic 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-harmonic modes, such as quadrupoles. Effective second-harmonic susceptibilities are proportional to the surface-to-volume ratio of a particle, emphasizing the nanoscale enhancement of the effect.

  4. Second harmonic generation double stokes Mueller polarimetric microscopy of myofilaments

    PubMed Central

    Kontenis, Lukas; Samim, Masood; Karunendiran, Abiramy; Krouglov, Serguei; Stewart, Bryan; Barzda, Virginijus


    The experimental implementation of double Stokes Mueller polarimetric microscopy is presented. This technique enables a model-independent and complete polarimetric characterization of second harmonic generating samples using 36 Stokes parameter measurements at different combinations of incoming and outgoing polarizations. The degree of second harmonic polarization and the molecular nonlinear susceptibility ratio are extracted for individual focal volumes of a fruit fly larva wall muscle. PMID:26977362

  5. Second harmonic inversion for ultrasound contrast harmonic imaging

    NASA Astrophysics Data System (ADS)

    Pasovic, Mirza; Danilouchkine, Mike; Faez, Telli; van Neer, Paul L. M. J.; Cachard, Christian; van der Steen, Antonius F. W.; Basset, Olivier; de Jong, Nico


    Ultrasound contrast agents (UCAs) are small micro-bubbles that behave nonlinearly when exposed to an ultrasound wave. This nonlinear behavior can be observed through the generated higher harmonics in a back-scattered echo. In past years several techniques have been proposed to detect or image harmonics produced by UCAs. In these proposed works, the harmonics generated in the medium during the propagation of the ultrasound wave played an important role, since these harmonics compete with the harmonics generated by the micro-bubbles. We present a method for the reduction of the second harmonic generated during nonlinear-propagation-dubbed second harmonic inversion (SHI). A general expression for the suppression signals is also derived. The SHI technique uses two pulses, p' and p'', of the same frequency f0 and the same amplitude P0 to cancel out the second harmonic generated by nonlinearities of the medium. Simulations show that the second harmonic is reduced by 40 dB on a large axial range. Experimental SHI B-mode images, from a tissue-mimicking phantom and UCAs, show an improvement in the agent-to-tissue ratio (ATR) of 20 dB compared to standard second harmonic imaging and 13 dB of improvement in harmonic power Doppler.

  6. Study on heavy matching layer transducer towards producing second harmonics

    NASA Astrophysics Data System (ADS)

    Zaini, Zulfadhli; Osuga, Masamizu; Jimbo, Hayato; Yasuda, Jun; Takagi, Ryo; Yoshizawa, Shin; Umemura, Shin-ichiro


    Cavitation bubbles are microbubbles which can be incepted by highly negative pressure. Producing such highly negative pressure exceeding the cavitation threshold is difficult to accomplish due to nonlinear propagation followed by focal phase shift. By superimposing the second harmonic to fundamental is a way to significantly reduce the problem. However, the conventional design for an air-backed transducer is not suitable to generate both the second harmonic and fundamental at the same time. In order to overcome this problem, we propose a high impedance matching layer approach. Furthermore, we also construct a study to foresee the impact by adjusting the thickness ratio towards fundamental and second harmonic. Numerical simulation and experimental measurement have shown that by using a high impedance matching layer, efficiently generation of both the second harmonic (2 MHz) and fundamental (1 MHz) at the same time is possible. Besides, by adjusting the thickness ratio between piezocomposite and heavy matching layer will influence the amplitude of acoustic power over squared of voltage of the fundamental and second harmonic.

  7. Second-harmonic frequency-resolved optical gating covering two and a half optical octaves using a single spectrometer

    NASA Astrophysics Data System (ADS)

    Marceau, C.; Thomas, S.; Kassimi, Y.; Gingras, G.; Witzel, B.


    We report the measurement of laser pulse shapes covering the range 580-3250 nm using second-harmonic generation frequency-resolved optical gating equipped with a single inexpensive visible-NIR miniature spectrometer and a single pair of homemade broadband beam splitters. Our experimental scheme exploits frequency up-conversion by BBO crystals and appropriate corrections for dispersion, beam splitter filtering and phase-matching efficiency. The signal and idler waves from a commercial optical parametric amplifier pumped by a Ti:Sapphire laser (26 fs, 1 kHz) have been characterized as well as their second harmonic. The pulse shapes out of a commercial difference frequency generation module mixing signal and idler have also been measured up to 3250 nm. The resulting pulses range from 20 to 120 fs, and their chirp characteristics are also exposed. Our approach is demonstrated over most of the doubling crystal transparency range.

  8. Second harmonic generation in graphene-coated nanowires.


    Gao, Yixiao; Shadrivov, Ilya V


    We study second harmonic generation in a pair of graphene-coated nanowires. We show that the phase matching condition for harmonic generation can be engineered in a wide range of frequencies by tuning the spacing between graphene nanowires. We derive coupled mode equations describing the process of second harmonic generation using an unconjugated Lorentz reciprocity theorem. We show that the highest harmonic generation efficiency can be achieved by phase matching the fundamental mode with the two lowest order symmetric modes at the second harmonic frequency. Despite losses in graphene, we predict that the efficiency can be further enhanced by reducing the radius of nanowires due to larger mode overlap and lower propagation loss. PMID:27472634

  9. Solitons and second harmonic radiation in type III bursts

    NASA Technical Reports Server (NTRS)

    Papadopoulos, K.; Freund, H. P.


    The emission at the second harmonic of the plasma frequency from self-consistent Langmuir solitons is calculated. The theory predicts, in a natural way, the observed transition from the region where the intensity is linearly proportional to the electron flux to the region where the radio intensity is proportional to the square of the electron flux. A detailed comparison of the radiation observed at the second harmonic for the burst of 18:10 UT March 31, 1976, with the one expected on the assumption of radiation from solitons, using the correlated in situ measurements of the electric fields at the second harmonic, and their spatial structure, provides strong evidence that, for the first time, Langmuir solitons have been observed in space.

  10. Unified approach to Čerenkov second harmonic generation.


    Roppo, Vito; Kalinowski, Ksawery; Sheng, Yan; Krolikowski, Wieslaw; Cojocaru, Crina; Trull, Jose


    We discuss the effect of second harmonic generation via the Čerenkov-like process in nonlinear bulk media and waveguides. We show that in both schemes the Čerenkov harmonic emission represents in fact a nonlinear Bragg diffraction process. It is therefore possible, for the first time, to describe the bulk and waveguide Čerenkov emission uniformly by considering the spatial modulation of the second-order nonlinear polarization. This is also experimentally illustrated by studying the Čerenkov second harmonic generation at the boundary of a nonlinear quadratic medium via the total internal reflection inside the nonlinear crystal. PMID:24216797

  11. Corrected formula for the polarization of second harmonic plasma emission

    NASA Technical Reports Server (NTRS)

    Melrose, D. B.; Dulk, G. A.; Gary, D. E.


    Corrections for the theory of polarization of second harmonic plasma emission are proposed. The nontransversality of the magnetoionic waves was not taken into account correctly and is here corrected. The corrected and uncorrected results are compared for two simple cases of parallel and isotropic distributions of Langmuir waves. It is found that whereas with the uncorrected formula plausible values of the coronal magnetic fields were obtained from the observed polarization of the second harmonic, the present results imply fields which are stronger by a factor of three to four.

  12. 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.


    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.

  13. Sensing with multipolar second harmonic generation from spherical metallic nanoparticles.


    Butet, Jérémy; Russier-Antoine, Isabelle; Jonin, Christian; Lascoux, Noëlle; Benichou, Emmanuel; Brevet, Pierre-François


    We show that sensing in the nonlinear optical regime using multipolar surface plasmon resonances is more sensitive in comparison to sensing in the linear optical regime. Mie theory, and its extension to the second harmonic generation from a metallic nanosphere, is used to describe multipolar second harmonic generation from silver metallic nanoparticles. The standard figure of merit of a potential plasmonic sensor based on this principle is then calculated. We finally demonstrate that such a sensor is more sensitive to optical refraction index changes occurring in the vicinity of the metallic nanoparticle than its linear counterpart. PMID:22375818

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

    SciTech Connect

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


    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.

  15. Digital Video Disc Recorder Using Second Harmonic Generation Green Laser

    NASA Astrophysics Data System (ADS)

    Seo, Joong Eon; Park, In Sik; Oh, Young Nam; Lee, Seung Hoon; Seong, Pyong Yong; Jang, Yoon Ki; Shin, Dong Ho


    A prototype of a digital video disc recorder (D-VDR) with laser-disc-quality video and compact-disc-quality audio is developed and demonstrated using a second harmonic generation (SHG) green laser, narrow-track magneto-optical disk (MOD), mark edge recording and data compression.

  16. Deep-subwavelength waveguiding via inhomogeneous second-harmonic generation.


    Roppo, Vito; Vincenti, Maria Antonietta; de Ceglia, Domenico; Scalora, Michael


    We theoretically investigate second-harmonic generation in extremely narrow, subwavelength semiconductor and dielectric waveguides. We discuss a guiding mechanism characterized by the inhibition of diffraction and the suppression of cutoff limits in the context of a light trapping phenomenon that sets in under conditions of general phase and group velocity mismatch between the fundamental and the generated harmonic. PMID:22859096

  17. Theory of second harmonic generation in randomly oriented species

    NASA Astrophysics Data System (ADS)

    Andrews, David L.; Allcock, Philip; Demidov, Andrey A.


    It is well known that second harmonic generation (SHG) is a process forbidden within atomic and molecular fluids. Nonetheless recent experimental observations of second harmonic evolution in suspensions of randomly oriented Halobacterium halobium purple membranes have raised new questions about the precise criteria which determine prohibition of the second harmonic. To address the problem a theoretical framework for SHG is developed that specifically deals with molecular systems, and is therefore cast in terms of molecular properties with more regard to the influence of the local structure. This contrasts with the classical approach based on bulk susceptibilities, which has not proved adequate to explain the conflicting experimental results. By properly formulating the detailed procedure for dealing with the necessary orientational averages, the present theory discloses a relationship between the coherent process of second harmonic generation and a directed component of its incoherent counterpart, hyper-Rayleigh scattering. Inter alia, the theory explains the SHG detected in purple membrane suspensions. The polarisation features of the harmonic evolution are also considered more generally, and in particular it is shown that the SHG signal will persist under conditions of circularly polarised pumping. This specific polarisation feature will allow experimental validation of the theory.

  18. Few recent experiments on surface studies by second harmonic generation

    SciTech Connect

    Shen, Y.R.


    Surface second harmonic generation (SHG) is used to monitor adsorption and desorption of molecules on metal and semiconductor surfaces in ultrahigh vacuum. Surface SHG has also been used to study monolayers of molecules at a liquid/air interface. 13 refs., 6 figs. (WRF)

  19. Theory of anomalous backscattering in second harmonic X-mode ECRH experiments

    NASA Astrophysics Data System (ADS)

    Gusakov, E. Z.; Popov, A. Yu.


    A quantitative model explaining generation of the anomalous backscattering signal in the second harmonic X-mode electron cyclotron resonance heating (ECRH) experiments at TEXTOR tokamak as a secondary nonlinear process which accompanies a primary low-threshold parametric decay instability (PDI) leading to excitation of two—upper hybrid (UH)—plasmons trapped in plasma is developed. The primary absolute PDI enhancing the UH wave fluctuations from the thermal noise level is supposed to be saturated due to a cascade of secondary low-threshold decays of the daughter UH wave leading to excitation of the secondary UH waves down-shifted in frequency and the ion Bernstein wave. A set of equations describing the cascade is derived and solved numerically. The results of numerical modelling are shown to be in agreement with the analytical estimations of the growth rate of the initial and secondary parametric decays and the saturation level. The generation of backscattering signal is explained by coupling of the daughter UH waves. The fine details of the frequency spectrum of the anomalously reflected extraordinary wave and the absolute value of the observed backscattering signal in the second harmonic X-mode ECRH experiments at TEXTOR are reproduced.

  20. Second-harmonic generation microscopy of collagen-bearing structures

    NASA Astrophysics Data System (ADS)

    Vanbel, Maarten K.; Callewaert, Tom; Verbiest, Thierry


    Nonlinear optical phenomena cover a broad research area. The emphasis is mostly on the generation of higher harmonics to be used in laser designs or on the characterization capabilities of nonlinear optics. The latter ability of nonlinear optics is important when combined with a microscope to detect simultaneously multiphoton fluorescence and second-harmonic generation. Submicron size features can then be investigated separately and information on their structure can be revealed by second-harmonic generation. For example, the point group symmetry can be determined in situ and in vivo in complex media. Moreover, nonlinear optical microscopy has several additional advantages: the generation and detection of nonlinear signals is intrinsically confocal and degradation, if present, only occurs at a localized places in the structure. In biological structures, multiphoton fluorescence and second-harmonic generation do not necessarily occur in the same type of the structure. This can be exploited to visualize different structures in one sample by simultaneous detection of two-photon fluorescence and second-harmonic generation. Also, the incident beam can be tuned to fit in the biological window of biological structures, which gives second-harmonic generation microscopy a significant advantage over linear microscopy due to absorbance issues in the visible wavelength range. We exploit these advantages to characterize collagen-bearing biological structures. Collagen is the dominant structural protein in connective tissue in mammals. Being the most abundant protein in the mammal clade, it is essential for the very existence of it. Collagen is a protein with a very strict quaternary structure. The most simple Ramachandran model states that an amino-acid sequence of Glycine-prolin-hydroxyprolin leads to a right-handed helical structure. The inherent stability is such that a sole helix cannot exist for a prolonged period of time, it will therefore combine with 2 near identical

  1. Second harmonic generation of chemical oxygen-iodine laser

    NASA Astrophysics Data System (ADS)

    Miura, Noriaki; Mese, Norimichi; Yoshino, Satoru; Uchiyama, Taro


    Intracavity second harmonic generation of chemical oxygen iodine laser utilizing LiB3O5 crystal has been studied. A chemical oxygen iodine laser of which the fundamental maximum output power is 3 W in TEM00 mode with the Cl2 flow rate of 300 mmol/min is used. Obtained total second harmonic power is a maximum of about 6 W. Therefore, we could estimate that the effective extraction efficiency is 200%. It is thought that the latter is above 100% due to the condition that the output coupling for the fundamental beam is not optimum. And applying the result of a fundamental laser power measurement, the internal conversion efficiency is estimated at 0.29%.

  2. 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


    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.

  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.


    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. 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


    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.

  5. Efficient second harmonic generation in internal asymmetric plasmonic slot waveguide.


    Huang, Tianye; Tagne, Patrick Moteng; Fu, Songnian


    We theoretically propose an internal asymmetric plasmonic slot waveguide (IAPSW), containing two different materials in the slot region. The IAPSW is used for second harmonic generation (SHG) at a wavelength of 1.55 μm. The required phase matching condition is satisfied between the 0th-order mode at the fundamental frequency and the 1st-order mode at the second harmonic frequency. By choosing appropriate slot geometry and materials, the mode field distribution is engineered to enhance the nonlinear coupling coefficient for SHG. With an 11 μm long IAPSW, a conversion efficiency of 24% (1.8 × 105 W-1cm-2 normalized conversion efficiency) is predicted. Furthermore, the SHG efficiency is more pronounced in IAPSW with thinner slot. PMID:27137584

  6. Controlling Second Harmonic Efficiency of Laser Beam Interactions

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P. (Inventor); Walsh, Brian M. (Inventor); Reichle, Donald J. (Inventor)


    A method is provided for controlling second harmonic efficiency of laser beam interactions. A laser system generates two laser beams (e.g., a laser beam with two polarizations) for incidence on a nonlinear crystal having a preferred direction of propagation. Prior to incidence on the crystal, the beams are optically processed based on the crystal's beam separation characteristics to thereby control a position in the crystal along the preferred direction of propagation at which the beams interact.

  7. Enhanced second harmonic generation from coupled asymmetric plasmonic metal nanostructures

    NASA Astrophysics Data System (ADS)

    Yildiz, Bilge Can; Emre Tasgin, Mehmet; Kurtulus Abak, Musa; Coskun, Sahin; Emrah Unalan, Husnu; Bek, Alpan


    We experimentally demonstrate that two coupled metal nanostructures (MNSs), a silver nanowire and bipyramid, can produce ∼30 times enhanced second harmonic generation compared to the particles alone. We develop a simple theoretical model, presenting the path interference effects in the nonlinear response of coupled MNSs. We show that the reason for such an enhancement can be the occurrence of a Fano resonance due to the coupling of the converter MNS to the long-lived mode of the attached MNS.

  8. Monolithic AlGaAs second-harmonic nanoantennas.


    Gili, V F; Carletti, L; Locatelli, A; Rocco, D; Finazzi, M; Ghirardini, L; Favero, I; Gomez, C; Lemaître, A; Celebrano, M; De Angelis, C; Leo, G


    We demonstrate monolithic aluminum gallium arsenide (AlGaAs) optical nanoantennas. Using a selective oxidation technique, we fabricated epitaxial semiconductor nanocylinders on an aluminum oxide substrate. Second harmonic generation from AlGaAs nanocylinders of 400 nm height and varying radius pumped with femtosecond pulses delivered at 1554-nm wavelength has been measured, revealing a peak conversion efficiency exceeding 10-5 for nanocylinders with an optimized geometry. PMID:27410864

  9. Second-harmonic generation in KNbO3 crystals

    NASA Astrophysics Data System (ADS)

    Lu, Yutian; Zhao, Quingchun; Li, Yongchun; He, Huijuan; Zou, Qun; Lu, Zheng; Zhaohua, Geng


    Efficient second-harmonic generation from a pulsed parametric laser to 427 to 470 nm has been obtained in a KNbO3 crystal only 1.5 mm in length by angular tuning at room temperature. The energy conversion efficiency is over 40%. Single pulse blue light output reaches 60 kW in peak power. The angular dependence of a phase matching wavelength, the relation between conversion efficiency and fundamental intensity, and acceptable angular phase mismatch are studied and discussed.

  10. Second-harmonic generation with magnetic-field controllability.


    Ju, Sheng; Cai, Tian-Yi; Wei, Chi-I; Guo, Guang-Yu


    Based on density functional theory with the generalized gradient approximation plus on-site Coulomb repulsion method, we study the magnetic-ordering dependence of second-harmonic generation (SHG) in a polar magnet BiCoO(3). The large second-order optical susceptibility, which can reach 3.7x10(-7) esu, exhibits a strong magnetic-ordering dependence, giving rise to magnetic-field controllable SHG response in polar magnets. PMID:20016638

  11. Dynamics of Flat Bunches with Second Harmonic RF

    SciTech Connect

    Sen, Tanaji; Bhat, Chandra; Kim, Hyung Jin; Ostiguy, Jean-Francois; /Fermilab


    We investigate the dynamics of longitudinally flat bunches created with a second harmonic cavity in a high energy collider. We study Landau damping in a second harmonic cavity with analytical and numerical methods. The latter include particle tracking and evolution of the phase space density. The results are interpreted in the context of possible application to the LHC. A possible path to a luminosity upgrade at the LHC is through the creation of longitudinally flat bunches. They can increase the luminosity roughly by 40% when the beam intensities are at the beam-beam limit. Lower momentum spread which can reduce backgrounds and make collimation easier as well lower peak fields which can mitigate electron cloud effects are other advantages. Use of a second harmonic rf system is a frequently studied method to create such flat bunches. Here we consider some aspects of longitudinal dynamics of these bunches in the LHC at top energy. First we consider intensity limits set by the loss of Landau damping against rigid dipole oscillations. Next we describe numerical simulations using both particle tracking and evolution of the phase space density. These simulations address the consequences of driving a bunch at a frequency that corresponds to the maximum of the synchrotron frequency.

  12. Time-resolved electric-field-induced second harmonic

    NASA Astrophysics Data System (ADS)

    Meshulam, Guilia; Berkovic, Garry; Kotler, Zvi


    One limitation of using electric field induced second harmonic (EFISH) to determine the molecular first hyperpolarizability (beta) of nonlinear optical molecules lies in the fact that part of the second harmonic signal comes from the second hyperpolarizability (gamma) produced by mixing two optical fields with the DC field. In analyzing EFISH results, the second hyperpolarizability contribution of the studied molecules is generally neglected. We present a modified time resolved EFISH technique that allows us, in a single experiment, to determine separately the beta and the gamma contributions. We study para-nitro aniline dissolved in Glycerol, a highly viscous solvent, and apply the DC field via a high voltage pulse with a fast rise time of approximately 40 nsec. As a result, the orientation of the molecules under the applied electric field is slow relative to the build-up of the field, enabling us to directly measure only the DC induced second harmonic (gamma contribution), at the beginning of the HV pulse. The pure beta contribution is determined from the difference between this signal and the conventional EFISH signal at the plateau of the HV pulse. Our result confirm that the gamma contribution is indeed less than 10% of the total.

  13. High power operation of first and second harmonic gyrotwystrons

    SciTech Connect

    Lawson, W.; Latham, P.E.; Calame, J.P.; Cheng, J.; Hogan, B.; Nusinovich, G.S.; Irwin, V.; Granatstein, V.L.; Reiser, M.


    We report the first experimental operation of overmoded first and second harmonic gyrotwystron amplifier configurations. Both devices utilize a single cavity which is driven near 9.87 GHz in the TE{sub 011} mode, heavily attenuated drift tubes, and long tapered output waveguide sections. A magnetron injection gun produces a 460 kV, 245 A beam with a maximum average perpendicular-to-parallel velocity ratio approximately equal to one. The axial magnetic field profile is sharply tapered in the output section. Peak powers above 21 MW are achieved in 1 {mu}s pulses with an efficiency exceeding 22% and a large signal gain near 24 dB in the first harmonic tube. The second harmonic tube achieves nearly 12 MW of the peak power with an efficiency of 11% and a gain above 21 dB. First harmonic amplifier performance is limited principally by competition from a fundamental mode output waveguide interaction; the second harmonic tube is limited by both travelling wave output modes and by a down-taper oscillation. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  14. Second Harmonics of Reversed Shear TAE in Alcator C-Mod Geometry

    NASA Astrophysics Data System (ADS)

    Chen, Eugene; Berk, Herbert; Breizman, Boris; Zheng, Linjin


    Experiments on Alcator C-Mod, operating with reversed magnetic shear, reveal Toroidal Alfven Eigenmodes (TAE) together with signals at twice the mode frequency. The double frequency signals can be viewed as second harmonic sidebands driven by quadratic non-linear terms in the MHD equations, in analogy with a corresponding theory for Alfven Cascades [1]. However, these nonlinear sidebands have not yet been quantified by any of the existing codes. In this work, we extend AEGIS code [2] to capture nonlinear effects iteratively by treating the nonlinear terms as a driving source in the linear MHD solver. We first compute the TAE mode structure for realistic geometry and q-profile and then use it to find the spatial structure of the second harmonic density perturbation, which can be directly compared with PCI measurements at Alcator C-Mod. [1] H. Smith, B. N. Breizman, M. Lisak and D. Anderson, Physics of Plasmas 13 042504 (2006) [2] L. J. Zheng and M. Kotschenreuther, Journal of Computational Physics 211 (2006) 748-766

  15. Detecting and characterizing ferroelectric domain boundaries using nonphase-matched second harmonic generation

    SciTech Connect

    Gehr, R.J.; Alford, W.J.; Smith, A.V.


    We demonstrate that tilted planar ferroelectric domain boundaries create tilted second harmonic beams in nonphase-matched second harmonic generation, and that the tilt of the boundary can be deduced from the harmonic direction.

  16. Second harmonic generation from multilayers of oriented metal bisphosphonates

    SciTech Connect

    Neff, G.A.; Mahon, T.M.; Abshere, T.A.; Page, C.J.


    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 harmonic generation (SHG) intensity from the bulk film is measured to verify NLO activity.

  17. Controlling attosecond angular streaking with second harmonic radiation.


    Hammond, T J; Kim, Kyung Taec; Zhang, Chunmei; Villeneuve, D M; Corkum, P B


    High harmonic generation, which produces a coherent burst of radiation every half cycle of the driving field, has been combined with ultrafast wavefront rotation to create a series of spatially separated attosecond pulses, called the attosecond lighthouse. By adding a coherent second harmonic beam with polarization parallel to the fundamental, we decrease the generating frequency from twice per optical cycle to once. The increased temporal separation increases the pulse contrast. By scanning the carrier envelope phase, we see that the signal is 2π periodic. PMID:25872069

  18. Studies of surface diffusion by second harmonic fluctuation spectroscopy

    SciTech Connect

    Zhao, Xiaolin; Goh, M.C.; Subrahmanyan, S.; Eisenthal, K.B. )


    The authors have shown how the fluctuations in the signal from surface second harmonic generation can be utilized for the study of a heterogeneous surface such as palmitic acid (C{sub 15}H{sub 31}COOH) spread on the air/water interface, under conditions of gas-liquid coexistence. The authors report observations of time-correlated fluctuations in the SH signal, with decay constant of approximately 6 s. This is attributed to motions of the liquidlike clusters of palmitic acid. If the motion is diffusive, a diffusion constant of about 10{sup {minus}8} cm{sup 2}/s is estimated for these clusters.

  19. Stokes vector formalism based second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Qiu, Jianjun; Mazumder, Nirmal; Tsai, Han-Ruei; Hu, Chih-Wei; Kao, Fu-Jen


    In this study, we have developed a four-channel Stokes vector formalism based second harmonic generation (SHG) microscopy to map and analyze SHG signal. A four-channel Stokesmeter setup is calibrated and integrated into a laser scanning microscope to measure and characterize the SH's corresponding Stokes parameters. We are demonstrating the use of SH and its Stokes parameters to visualize the birefringence and crystalline orientation of KDP and collagen. We believe the developed method can reveal unprecedented information for biomedical and biomaterial studies.

  20. Surface lattice resonances in second-harmonic generation from metasurfaces.


    Czaplicki, Robert; Kiviniemi, Antti; Laukkanen, Janne; Lehtolahti, Joonas; Kuittinen, Markku; Kauranen, Martti


    We investigate the role of surface-lattice resonances (SLRs) in second-harmonic generation (SHG) from arrays of metal nanoparticles. The SLRs affect the generated signal when the sample is rotated away from normal incidence. The adjustment of the incident angle tunes the SLRs to the fundamental wavelength for SHG and improves the quality of the resonance for better resonance enhancement of SHG. Compared to normal incidence, an enhancement by a factor of 10 is observed. However, at certain incident angles, the enhancement is interrupted by diffraction anomalies, which redirect light into the substrate, increasing radiation damping and compromising the quality of the resonance. PMID:27304263

  1. Second Harmonic Generation Mediated by Aligned Water in Starch Granules.


    Cisek, Richard; Tokarz, Danielle; Krouglov, Serguei; Steup, Martin; Emes, Michael J; Tetlow, Ian J; Barzda, Virginijus


    The origin of second harmonic generation (SHG) in starch granules was investigated using ab initio quantum mechanical modeling and experimentally examined using polarization-in, polarization-out (PIPO) second harmonic generation microscopy. Ab initio calculations revealed that the largest contribution to the SHG signal from A- and B-type allomorphs of starch originates from the anisotropic organization of hydroxide and hydrogen bonds mediated by aligned water found in the polymers. The hypothesis was experimentally tested by imaging maize starch granules under various hydration and heat treatment conditions that alter the hydrogen bond network. The highest SHG intensity was found in fully hydrated starch granules, and heat treatment diminished the SHG intensity. The PIPO SHG imaging showed that dried starch granules have a much higher nonlinear optical susceptibility component ratio than fully hydrated granules. In contrast, deuterated starch granules showed a smaller susceptibility component ratio demonstrating that SHG is highly sensitive to the organization of the hydroxyl and hydrogen bond network. The polarization SHG imaging results of potato starch granules, representing starch allomorph B, were compared to those of maize starch granules representing allomorph A. The results showed that the amount of aligned water was higher in the maize granules. Nonlinear microscopy of starch granules provides evidence that varying hydration conditions leads to significant changes in the nonlinear susceptibility ratio as well as the SHG intensity, supporting the hypothesis from ab initio calculations that the dominant contribution to SHG is due to the ordered hydroxide and hydrogen bond network. PMID:25427055

  2. Characterization of Second Harmonic Afterburner Radiation at the LCLS

    SciTech Connect

    Nuhn, Heinz-Dieter


    During commissioning of the Linac Coherent Light Source (LCLS) x-ray Free Electron Laser (FEL) at the SLAC National Accelerator Laboratory it was shown that saturation lengths much shorter than the installed length of the undulator line can routinely be achieved. This frees undulator segments that can be used to provide enhanced spectral properties and at the same time, test the concept of FEL Afterburners. In December 2009 a project was initiated to convert undulator segments at the down-beam end of the undulator line into Second Harmonic Afterburners (SHAB) to enhance LCLS radiation levels in the 10-20 keV energy range. This is being accomplished by replacement of gap-shims increasing the fixed gaps from 6.8 mm to 9.9 mm, which reduces their K values from 3.50 to 2.25 and makes the segments resonant at the second harmonic of the upstream unmodified undulators. This paper reports experimental results of the commissioning of the SHAB extension to LCLS.

  3. Polarization-Modulated Second Harmonic Generation Microscopy in Collagen

    SciTech Connect

    Stoller, P C


    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 harmonic generation (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 harmonic signal in two dimensional images varies with position even in structurally homogeneous tissue; this phenomenon is due to interference between second harmonic light generated 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

  4. Measuring Microtubule Polarity in Spindles with Second-Harmonic Generation

    PubMed Central

    Yu, Che-Hang; Langowitz, Noah; Wu, Hai-Yin; Farhadifar, Reza; Brugues, Jan; Yoo, Tae Yeon; Needleman, Daniel


    The spatial organization of microtubule polarity, and the interplay between microtubule polarity and protein localization, is thought to be crucial for spindle assembly, anaphase, and cytokinesis, but these phenomena remain poorly understood, in part due to the difficulty of measuring microtubule polarity in spindles. We develop and implement a method to nonperturbatively and quantitatively measure microtubule polarity throughout spindles using a combination of second-harmonic generation and two-photon fluorescence. We validate this method using computer simulations and by comparison to structural data on spindles obtained from electron tomography and laser ablation. This method should provide a powerful tool for studying spindle organization and function, and may be applicable for investigating microtubule polarity in other systems. PMID:24739157

  5. Second harmonic generation and crystal growth of new chalcone derivatives

    NASA Astrophysics Data System (ADS)

    Patil, P. S.; Dharmaprakash, S. M.; Ramakrishna, K.; Fun, Hoong-Kun; Sai Santosh Kumar, R.; Narayana Rao, D.


    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 harmonic generation 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.

  6. Second harmonic chalcone crystal: Synthesis, growth and characterization

    NASA Astrophysics Data System (ADS)

    D'silva, E. D.; Narayan Rao, D.; Philip, Reji; Butcher, Ray J.; Rajnikant; Dharmaprakash, S. M.


    The novel nonlinear optical chalcone derivative (2 E)-3-[4-(methylsulfanyl)phenyl]-1-(3-bromophenyl)prop-2-en-1-one (3Br4MSP) crystals have been grown by slow evaporation technique at ambient temperature. The crystal was subjected to different types of characterization method in order to study its possible application in nonlinear optics. The structure determination of the grown crystal was done by single crystal X-ray diffraction study. The morphology of the crystal is studied. The crystal was subjected to thermal analysis to find its thermal stability. The grown crystals were characterized for their optical transmission and mechanical hardness. The second harmonic generation (SHG) efficiency of the crystal is obtained by classical powdered technique. The laser damage threshold for 3Br4MSP crystal was determined using Q-switched Nd:YAG laser.

  7. Polarization-modulated second harmonic generation in collagen.


    Stoller, Patrick; Reiser, Karen M; Celliers, Peter M; Rubenchik, Alexander M


    Collagen possesses a strong second-order nonlinear susceptibility, a nonlinear optical property characterized by second harmonic generation in the presence of intense laser beams. We present a new technique involving polarization modulation of an ultra-short pulse laser beam that can simultaneously determine collagen fiber orientation and a parameter related to the second-order nonlinear susceptibility. We demonstrate the ability to discriminate among different patterns of fibrillar orientation, as exemplified by tendon, fascia, cornea, and successive lamellar rings in an intervertebral disc. Fiber orientation can be measured as a function of depth with an axial resolution of approximately 10 microm. The parameter related to the second-order nonlinear susceptibility is sensitive to fiber disorganization, oblique incidence of the beam on the sample, and birefringence of the tissue. This parameter represents an aggregate measure of tissue optical properties that could potentially be used for optical imaging in vivo. PMID:12023255

  8. Thermal optimization of second harmonic generation at high pump powers.


    Sahm, Alexander; Uebernickel, Mirko; Paschke, Katrin; Erbert, Götz; Tränkle, Günther


    We measure the temperature distribution of a 3 cm long periodically poled LiNbO₃ crystal in a single-pass second harmonic generation (SHG) setup at 488 nm. By means of three resistance heaters and directly mounted Pt100 sensors the crystal is subdivided in three sections. 9.4 W infrared pump light and 1.3 W of SHG light cause a de-homogenized temperature distribution of 0.2 K between the middle and back section. A sectional offset heating is used to homogenize the temperature in those two sections and thus increasing the conversion efficiency. A 15% higher SHG output power matching the prediction of our theoretical model is achieved. PMID:22109182

  9. Creation and doubling of vortices in intracavity second harmonic generation

    NASA Astrophysics Data System (ADS)

    Lim, Oo-Kaw; Boland, Brian; Saffman, Mark; Krolikowski, Wieslaw


    Optical vortices are topological objects whose transformation properties under propagation in linear and nonlinear optical media have been the subject of much recent interest. In this work we demonstrate generation and frequency doubling of unit charge vortices in a linear astigmatic resonator. By appropriate alignment of a near confocal cavity we couple a fundamental laser beam at 860nm to a vortical resonator mode. With a nonlinear crystal in the resonator a doubly charged vortex at the second harmonic frequency is generated. Topological instability of the double charge harmonic vortices leads to well separated vortex cores that are shown to rotate and become anisotropic, as the resonator is tuned across resonance. A simple theory that accounts for crystal induced astigmatism agrees well with the experimental measurements.

  10. Automated cardiac sarcomere analysis from second harmonic generation images

    NASA Astrophysics Data System (ADS)

    Garcia-Canadilla, Patricia; Gonzalez-Tendero, Anna; Iruretagoyena, Igor; Crispi, Fatima; Torre, Iratxe; Amat-Roldan, Ivan; Bijnens, Bart H.; Gratacos, Eduard


    Automatic quantification of cardiac muscle properties in tissue sections might provide important information related to different types of diseases. Second harmonic generation (SHG) imaging provides a stain-free microscopy approach to image cardiac fibers that, combined with our methodology of the automated measurement of the ultrastructure of muscle fibers, computes a reliable set of quantitative image features (sarcomere length, A-band length, thick-thin interaction length, and fiber orientation). We evaluated the performance of our methodology in computer-generated muscle fibers modeling some artifacts that are present during the image acquisition. Then, we also evaluated it by comparing it to manual measurements in SHG images from cardiac tissue of fetal and adult rabbits. The results showed a good performance of our methodology at high signal-to-noise ratio of 20 dB. We conclude that our automated measurements enable reliable characterization of cardiac fiber tissues to systematically study cardiac tissue in a wide range of conditions.

  11. Interpreting Second-Harmonic Generation Images of Collagen I Fibrils

    PubMed Central

    Williams, Rebecca M.; Zipfel, Warren R.; Webb, Watt W.


    Fibrillar collagen, being highly noncentrosymmetric, possesses a tremendous nonlinear susceptibility. As a result, second-harmonic generation (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

  12. Magnetic Second-Harmonic Generation from Interfaces and Nanostructures

    NASA Astrophysics Data System (ADS)

    McGilp, J. F.


    Magneto-optic techniques provide non-contact and non-destructive characterization of magnetic materials. This includes embedded magnetic nanostructures, which are accessible due to the large penetration depth of optical radiation. Nonlinear magnetic second-harmonic generation (MSHG) can measure the surface and interlace magnetism of centrosymmetric magnetic films and nanostructures with sub-monolayer sensitivity. MSHG is briefly reviewed and examples from high symmetry interlaces and nanostructures described. Low symmetry systems, such as aligned magnetic nanostructures grown by self-organization on vicinal substrates, are more difficult to characterize, however, because of the large number of tensor components that may contribute to the signal. Normal incidence geometry simplifies the problem and this new approach is shown to allow the determination of hysteresis loops and the temperature dependent magnetic response of Au-capped Fe nanostructures grown on vicinal W(110).

  13. Time-resolved phase-sensitive second harmonic generation spectroscopy

    NASA Astrophysics Data System (ADS)

    Nowakowski, Paweł J.; Woods, David A.; Bain, Colin D.; Verlet, Jan R. R.


    A methodology based on time-resolved, phase-sensitive second harmonic generation (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 generated 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.

  14. Second harmonic plasma emission involving ion sound waves

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.


    The theory for second harmonic plasma emission by the weak turbulence (or random phase) processes L + L + or - S to T, proceeding in two three-wave steps, L + or - S to L prime and L + L prime to T, where L, S and T denote Langmuir, ion sound and electromagnetic waves, respectively, is developed. Kinematic constraints on the characteristics and growth lengths of waves participating in the wave processes, and constraints on the characteristics of the source plasma, are derived. Limits on the brightness temperature of the radiation and the levels of the L prime and S waves are determined. Expressions for the growth rates and path-integrated wave temperatures are derived for simple models of the wave spectra and source plasma.

  15. Second Harmonic Generation in a Graphe Armchair Nanoribbon

    NASA Astrophysics Data System (ADS)

    Gumbs, Godfrey; Abranyos, Yonatan


    The second order nonlinear optical susceptibility χ (2) for second harmonic generation 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.

  16. Second-harmonic diffraction from holographic volume grating.


    Nee, Tsu-Wei


    The full polarization property of holographic volume-grating enhanced second-harmonic diffraction (SHD) is investigated theoretically. The nonlinear coefficient is derived from a simple atomic model of the material. By using a simple volume-grating model, the SHD fields and Mueller matrices are first derived. The SHD phase-mismatching effect for a thick sample is analytically investigated. This theory is justified by fitting with published experimental SHD data of thin-film samples. The SHD of an existing polymethyl methacrylate (PMMA) holographic 2-mm-thick volume-grating sample is investigated. This sample has two strong coupling linear diffraction peaks and five SHD peaks. The splitting of SHD peaks is due to the phase-mismatching effect. The detector sensitivity and laser power needed to measure these peak signals are quantitatively estimated. PMID:16985536

  17. 2D magnetic nanoparticle imaging using magnetization response second harmonic

    NASA Astrophysics Data System (ADS)

    Tanaka, Saburo; Murata, Hayaki; Oishi, Tomoya; Suzuki, Toshifumi; Zhang, Yi


    A detection method and an imaging technique for magnetic nanoparticles (MNPs) have been investigated. In MNP detection and in magnetic particle imaging (MPI), the most commonly employed method is the detection of the odd harmonics of the magnetization response. We examined the advantage of using the second harmonic response when applying an AC magnetic modulation field and a DC bias field. If the magnetization response is detected by a Cu-wound-coil detection system, the output voltage from the coil is proportional to the change in the flux, dϕ/dt. Thus, the dependence of the derivative of the magnetization, M, on an AC magnetic modulation field and a DC bias field were calculated and investigated. The calculations were in good agreement with the experimental results. We demonstrated that the use of the second harmonic response for the detection of MNPs has an advantage compared with the usage of the third harmonic response, when the Cu-wound-coil detection system is employed and the amplitude of the ratio of the AC modulation field and a knee field Hac/Hk is less than 2. We also constructed a 2D MPI scanner using a pair of permanent ring magnets with a bore of ϕ80 mm separated by 90 mm. The magnets generated a gradient of Gz=3.17 T/m transverse to the imaging bore and Gx=1.33 T/m along the longitudinal axis. An original concentrated 10 μl Resovist solution in a ϕ2×3 mm2 vessel was used as a sample, and it was imaged by the scanner. As a result, a 2D contour map image could be successfully generated using the method with a lock-in amplifier.

  18. Electromagnetic study of second harmonic generation by a corrugated waveguide

    NASA Astrophysics Data System (ADS)

    Neviere, Michel; Popov, E.; Reinisch, Raymond


    When an incident plane wave with circular frequency (omega) falls on a grating coated by a layer of nonlinear material, it generates a nonlinear polarization PNL(2(omega) ) which acts as a source term and produces a second harmonic (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 harmonics 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 harmonic generation (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

  19. Phase-shift measurments for second-harmonic generation in glass

    NASA Astrophysics Data System (ADS)

    Dominic, Vincent G.; Feinberg, Jack


    Focusing intense laser light along with some of its second harmonic into a glass sample transforms the glass into a frequency doubler. We present a new method to measure the optical phase shift between the second-harmonic beam used to seed the glass and the second- harmonic beam subsequently produced by the glass sample. Determination of this phase shift is essential for understanding the growth dynamics of the effect, and its value can discriminate between proposed theoretical models.

  20. Defects and strain enhancements of second-harmonic generation in Si/Ge superlattices

    NASA Astrophysics Data System (ADS)

    Bertocchi, Matteo; Luppi, Eleonora; Degoli, Elena; Véniard, Valérie; Ossicini, Stefano


    Starting from experimental findings and interface growth problems in Si/Ge superlattices, we have investigated through ab initio methods the concurrent and competitive behavior of strain and defects in the second-harmonic generation process. Interpreting the second-harmonic intensities as a function of the different nature and percentage of defects together with the strain induced at the interface between Si and Ge, we found a way to tune and enhance the second-harmonic generation response of these systems.

  1. Second harmonic generation imaging in tissue engineering and cartilage pathologies

    NASA Astrophysics Data System (ADS)

    Lilledahl, Magnus; Olderøy, Magnus; Finnøy, Andreas; Olstad, Kristin; Brinchman, Jan E.


    The second harmonic generation from collagen is highly sensitive to what extent collagen molecules are ordered into fibrils as the SHG signal is approximately proportional to the square of the fibril thickness. This can be problematic when interpreting SHG images as thick fibers are much brighter than thinner fibers such that quantification of the amount of collagen present is difficult. On the other hand SHG is therefore also a very sensitive probe to determine whether collagen have assembled into fibrils or are still dissolved as individual collagen molecules. This information is not available from standard histology or immunohistochemical techniques. The degree for fibrillation is an essential component for proper tissue function. We will present the usefulness of SHG imaging in tissue engineering of cartilage as well as cartilage related pathologies. When engineering cartilage it is essential to have the appropriate culturing conditions which cause the collagen molecules to assemble into fibrils. By employing SHG imaging we have studied how cell seeding densities affect the fibrillation of collagen molecules. Furthermore we have used SHG to study pathologies in developing cartilage in a porcine model. In both cases SHG reveals information which is not visible in conventional histology or immunohistochemistry

  2. Research of second harmonic generation images based on texture analysis

    NASA Astrophysics Data System (ADS)

    Liu, Yao; Li, Yan; Gong, Haiming; Zhu, Xiaoqin; Huang, Zufang; Chen, Guannan


    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 harmonic generation (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.

  3. Second harmonic generation reveals matrix alterations during breast tumor progression

    NASA Astrophysics Data System (ADS)

    Burke, Kathleen; Tang, Ping; Brown, Edward


    Alteration of the extracellular matrix in tumor stroma influences efficiency of cell locomotion away from the primary tumor into surrounding tissues and vasculature, thereby affecting metastatic potential. We study matrix changes in breast cancer through the use of second harmonic generation (SHG) of collagen in order to improve the current understanding of breast tumor stromal development. Specifically, we utilize a quantitative analysis of the ratio of forward to backward propagating SHG signal (F/B ratio) to monitor collagen throughout ductal and lobular carcinoma development. After detection of a significant decrease in the F/B ratio of invasive but not in situ ductal carcinoma compared with healthy tissue, the collagen F/B ratio is investigated to determine the evolution of fibrillar collagen changes throughout tumor progression. Results are compared with the progression of lobular carcinoma, whose F/B signature also underwent significant evolution during progression, albeit in a different manner, which offers insight into varying methods of tissue penetration and collagen manipulation between the carcinomas. This research provides insights into trends of stromal reorganization throughout breast tumor development.

  4. Two-photon resonant second harmonic generation in atomic xeon

    SciTech Connect

    Shi, Y. J.; Al-Basheer, W.; Thompson, R. I.


    Vacuum ultraviolet (VUV) radiation at 124.8 nm (9.93 eV) was produced from two-photon resonant second harmonic generation (SHG) in a xeon gaseous medium and used to probe molecular samples of acetone, furan, thiophene, ammonia, and methane. The mass spectra recorded from the species with ionization energies below 9.93 eV were dominated by the parent ions. The parent ions were only observed when the incident UV radiation was tuned to resonate with the two-photon transition 5p{sup 5}({sup 2}P{sub 3/2}{sup 0})6p[1/2]{sub 0}(leftarrow)5p{sup 6} {sup 1}S{sub 0} of Xe at 80 119.474 cm{sup -1}. The pressure dependence and the resonant nature of the parent ions observed support the mechanism for SHG as the ionization-initiated electric field induced SHG via the third-order nonlinear susceptibility {chi}{sup (3)}, which is enhanced by the coupling between the 5p{sup 5}({sup 2}P{sub 3/2}{sup 0})6p[1/2]{sub 0} and the nearby 5p{sup 5}({sup 2}P{sub 3/2}{sup 0})5d[1/2]{sub 1} states of Xe atoms.

  5. Second harmonic generation of chiral-modified silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Tao, Yue; Aldea-Nunzi, Gabriela; Rao Bobbara, Sanyasi; Nunzi, Jean-Michel


    Various approaches for the optical detection of chiral compounds have been developed due to their natural optical activity. Since the advantages of second harmonic generation (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.

  6. Second harmonic generation using nonlinear Rayleigh surface waves in stone

    NASA Astrophysics Data System (ADS)

    Smith, Margaret; Kim, Gun; Kim, Jin-Yeon; Kurtis, Kimberly; Jacobs, Laurence


    This research tests the potential application of the Second Harmonic Generation (SHG) method using nonlinear Rayleigh surface waves to nondestructively quantify surface microstructural changes in thin stone. The acoustic nonlinearity parameter (β) has been assessed as a meaningful indicator for characterizing the nonlinearity of civil engineering materials; additionally, Rayleigh waves offer the opportunity to isolate a material's near surface microstructural status. Sandstone was selected for testing due to its relative uniformity and small grain size compared to other stone types; the sample thickness was 2 inches to reflect the minimum panel thickness recommended by the Indiana Limestone Institute. For this research, initially fully non-contact generation and detection techniques are evaluated before a 100kHz wedge transmitter and a 200kHz air-coupled receiver are employed for generation and detection of nonlinear Rayleigh waves. Non-contact transmitters and receivers have advantages such as removing the irregularities associated with coupling as well as not leaving residues, which in stone applications can be considered aesthetically damaging. The experimental results show that the nonlinear parameter, β, can be effectively isolated using the wedge transmitter and non-contact set up and that too much of the signal strength is lost in the fully non-contact method to extract meaningful results for this stone and stones with slow wave speeds. This indicates that the proposed SHG technique is effective for evaluating the nonlinearity parameter, β, and can next be applied to characterize near surface microstructural changes in thin applications of dimensioned stone.

  7. Second harmonic generation in GF(m, 1) ferroelectric superlattices

    NASA Astrophysics Data System (ADS)

    Chen, Ying; Yang, Xiangbo; Guo, Qi; Lan, Sheng


    In this paper we study under the small-signal approximation the properties of the output electric field of second harmonic generation (SHG) for vertical transmission in Family A of the generalized Fibonacci (GF(m, 1)) quasiperiodic ferroelectric domain system. It is found that under perfect quasi-phase-matched (PQPM) conditions there exists self-similarity for the intense peaks of SHG (IPSHG) in real space and the two integers q and p indexing IPSHG make an interesting zero-odd set when m is large enough. On the other hand, self-similarity for IPSHG is broken under imperfect quasi-phase-matched (IQPM) conditions and the SHG spectra comprise a group of intense peaks and another group of satellite weak lines when m is very large. The corresponding integers q and p make an interesting odd-odd set and a successive integer set, respectively. Two kinds of effects of vacancies on SHG have also been found. The analytical results are confirmed by numerical simulations.

  8. New Molecular Ferroelectrics Accompanied by Ultrahigh Second-Harmonic Generation.


    Liu, Chuang; Gao, Kaige; Cui, Zepeng; Gao, Linsong; Fu, Da-Wei; Cai, Hong-Ling; Wu, X S


    Second-harmonic generation (SHG) is one of the outstanding properties for practical applications. However, the great majority of molecular ferroelectric materials have very low nonlinear optical coefficients, attenuating their attractive performance. Here we synthesized (4-amino-2-bromopyridinium)(4-amino-2-bromopyridine)tetrafluoroborate (1), whose second-order nonlinear optical coefficient reaches up to 2.56 pm V(-1), 2.67 times of that of KDP, and (4-amino-2-bromopyridinium)tetrafluoroborate (2), possessing a more incredible large second-order nonlinear optical coefficient as high as 10.24 pm V(-1), 10.67 times that of KDP. The compound 1 undergoes two reversible phase transitions at around T1 = 244.1 K and T2 = 154.6 K, caused by dramatic changes of the protonated cations and order-disorder of anions, which was disclosed by differential scanning calorimetry, heat capacity, dielectric anomalies, SHG, and single-crystal X-ray diffraction analysis. The pyroelectric measurements reveal that compound 1 is a Rochelle salt type ferroelectric, which has a large spontaneous polarization of about 3 μC/cm(2). PMID:27111056

  9. Imaging articular cartilage using second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Mansfield, Jessica C.; Winlove, C. Peter; Knapp, Karen; Matcher, Stephen J.


    Sub cellular resolution images of equine articular cartilage have been obtained using both second harmonic generation 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.

  10. Titanosilicates with Strong Phase-Matched Second Harmonic Generation Responses.


    Chao, Tzu-Ling; Chang, Wen-Jung; Wen, Shu-Han; Lin, Yu-Qing; Chang, Bor-Chen; Lii, Kwang-Hwa


    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 harmonic generation 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

  11. Operation of a Second Harmonic, Ku-Band Gyroklystron

    NASA Astrophysics Data System (ADS)

    Lawson, Wes; Gouviea, Steve; Hogan, Bart; Huebschman, Ben; Spassovsky, Ivan; Granatstein, Victor


    At the University of Maryland, we have designed a 4-cavity Ku-Band second harmonic gyroklystron tube which is expected to produce peak powers in excess of 80 MW with gains above 50 dB. The first cavity is driven at about 8.57 GHz in the TE011 mode and the remainder of the cavities operate at twice the drive frequency in the TE021 mode. In this paper we describe the details of the design, cold-testing, and hot-testing of the microwave tube. We also present results for a new output waveguide system which is designed to transform the output signal of the gyroklystron into a configuration which can be used to drive a compact linear accelerator structure at 17.136 GHz. The transformation occurs in stages, with the TE02 mode converted to a TE01 mode via a rippled-wall converter, followed by a conversion to the TE20 mode in rectangular waveguide, and completed with a bifurcation and linear taper to (2) standard WR62 rectangular waveguides. Details of the theoretical and cold-test results for each subsection will be presented.

  12. Effect of the domain shape on noncollinear second-harmonic emission in disordered quadratic media.


    Ayoub, Mousa; Passlick, Markus; Koynov, Kaloian; Imbrock, Jörg; Denz, Cornelia


    We study the role of the individual ferroelectric domain shape on the second-harmonic emission in strontium barium niobate featuring a random quadratic nonlinearity. The noncollinearly emitted second-harmonic signal is scanned in the far-field at different incident angles for different domain size distributions. This offers the possibility to retrieve the Fourier spectrum, corresponding to the spatial domain distribution and domain shape. Based on images of the domain structures retrieved by Čerenkov-type second-harmonic microscopy, domain patterns are simulated, the second-harmonic intensities are calculated, and finally compared with the measurements. PMID:24514720

  13. Resonant second harmonic generation of a Gaussian electromagnetic beam in a collisional magnetoplasma

    SciTech Connect

    Kaur, Sukhdeep; Sharma, A. K.; Salih, Hyder A.


    Second harmonic generation 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 harmonic current density, giving rise to resonant second harmonic radiation when the wave frequency is one-third of electron cyclotron frequency. The second harmonic field has azimuthal dependence as exp(i{theta}). The self-defocusing causes a reduction in the efficiency of harmonic generation.

  14. Second harmonic detection in the electrochemical strain microscopy of Ag-ion conducting glass

    SciTech Connect

    Yang, Sangmo; Okatan, Mahmut Baris; Paranthaman, Mariappan Parans; Jesse, Stephen; Noh, Tae Won; Kalinin, Sergei V.


    The first and second harmonic electromechanical responses and their cross-correlation in Ag-ion conducting glass were investigated using band-excitation electrochemical strain microscopy (ESM). Consecutive ESM images with increasing magnitudes of the applied AC voltage allowed observation of not only reversible surface displacement but also irreversible silver nanoparticle formation above a certain threshold voltage. The second harmonic ESM response was anticorrelated with the first harmonic response in many local regions. Furthermore, the nucleation sites of silver nanoparticles were closely related to the anti-correlated regions, specifically, with low second harmonic and high first harmonic ESM responses. The possible origins of the second harmonic ESM response are discussed.

  15. Transmission second harmonic generation in CdTe at 1.064 μm

    NASA Astrophysics Data System (ADS)

    Petrovic, M. S.; Suchocki, A.; Powell, R. C.; Cantwell, G.


    Transmission geometry measurements of the efficiency of second harmonic generation in various thicknesses of CdTe samples were made to determine the conversion efficiency dependence on material thickness. Neglecting pump depletion, it is found that for samples of well-defined symmetry, the second harmonic conversion efficiency scales with film thickness, with no observed enhancement owing to coherence length effects. The angular dependence of the observed second harmonic light in films of well-defined symmetry is consistent with second harmonic generation originating in the bulk.

  16. Studies of surfaces using optical second-harmonic generation

    SciTech Connect

    Tom, H.W.K.


    The experiments reported in this thesis demonstrate the use of second-harmonic generation (SHG) and sum-frequency generation (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.

  17. Studies of interfaces and vapors with Optical Second Harmonic Generation

    SciTech Connect

    Mullin, C. S.


    Optical Second Harmonic Generation (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.

  18. Second harmonic generation imaging microscopy of cellular structure and function

    NASA Astrophysics Data System (ADS)

    Millard, Andrew C.; Jin, Lei; Loew, Leslie M.


    Second harmonic generation (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.

  19. Second harmonic generation study of liquid surface and amphilphile monolayer

    SciTech Connect

    Zhao, X.


    This thesis contains the following topics. In Chapter 2, we use temperature dependent SHC to study the surface structure of some neat liquids. It was found all the hydrogen bonding liquids have a stronger SHG dependence of temperature while for the non-hydrogen bonding liquids SH response is insensitive to temperature change. In Chapter 3, we discussed the general feature of the electric field induced second harmonic generation (EFISHG). We experimentally established the importance of the {chi}{sup (3)} mechanism at the air/water charged interface. In Chapter 4, we used SHG to study the p-nitrophenol (PNP) penetration into the insoluble monolayer of hexadecyl and pentadecyl acid. It was found that PNP preferentially adsorbs at the fatty acid monolayer. The population and orientation of PNP is strongly dependent on the fatty acid monolayer packing. In Chapter 5, SH signal fluctuation spectroscopy was used to study the surface self-diffusion within the monolayer gas-liquid co-existence region. Assuming the uniform distribution of the liquid phase cluster size, a diffusion model was developed to fit the experimental measured autocorrelation function. In Chapter 6, SH fluctuation spectroscopy was used to study the monolayer orientation spontaneous fluctuation. It was found that only the electron rich aromatic head groups exhibit the orientational fluctuation while the electron poor aromatic molecules do not have a fluctuation anomalies. Fluctuation time scale is strongly influenced by the hydrophobic chain length. A quantitative theory was presented based on Landau-Ginzburg theory to fit the time dependent orientation fluctuation. In Chapter 7, we focused on the acid-base equilibrium constant measurement at the air/water interface using both {chi}{sup (2)} and {chi}{sup (2)} method. We have measured pKa of aniline, phenol, amine, and acid at the interface. It turned out that for all these species, the neutral form is more stable at the interface.

  20. Second-harmonic scanning microscopy of domains in Al wire bonds in IGBT modules.


    Simesen, Paw; Pedersen, Kristian Bonderup; Pedersen, Kjeld


    Scanning second harmonic generation microscopy has been used to investigate crystallographic orientation of the grain structure in Al wire bonds in insulated gate bipolar transistor modules. It was shown that the recorded second harmonic microscopy images revealed the grain structure of the Al sample. Additional information of the individual grain orientation was achieved by using simple interpretations of the recorded rotational anisotropy. PMID:26832011

  1. Self-Action of Second Harmonic Generation and Longitudinal Temperature Gradient in Nonlinear-Optical Crystals

    NASA Astrophysics Data System (ADS)

    Baranov, A. I.; Konyashkin, A. V.; Ryabushkin, O. A.


    Model of second harmonic generation with thermal self-action was developed. Second harmonic generation temperature phase matching curves were measured and calculated for periodically polled lithium niobate crystal. Both experimental and calculated data show asymmetrical shift of temperature tuning curves with pump power.

  2. NIR-triggered drug delivery by collagen-mediated second harmonic generation.


    Barhoumi, Aoune; Salvador-Culla, Borja; Kohane, Daniel S


    Second harmonic generation is a process through which nonlinear materials such as collagen can absorb two photons and scatter one with twice the energy. Collagen upconverts 730 nm (near-IR) to 365 nm (UV) through second harmonic generation, which cleaves a molecule bound to collagen via a UV-sensitive linker. PMID:25728310

  3. Vector treatment of second-harmonic generation produced by tightly focused vignetted Gaussian beams

    NASA Astrophysics Data System (ADS)

    Asatryan, Ara A.; Sheppard, Colin J. R.; de Sterke, C. Martijn


    We present a fast and accurate method to calculate the vector-field distribution of a focused Gaussian beam. This method is applied to calculate the second harmonic that is generated by such a beam from a sample in the undepleted pump approximation. These calculations can be used to model second-harmonic imaging in an optical microscope with a wide aperture.

  4. Observation of the second-harmonic generation from relativistically quivering electrons in exciting laser wakefield.


    Takahashi, Eiji; Mori, Michiaki; Yugami, Noboru; Nishida, Yasushi; Kondo, Kiminori


    The second-harmonic emission generated by the spatially asymmetric quivering electrons caused by the ponderomotive force was studied. The intensity of the second harmonic was proportional to the focused intensity of the pump pulse with the power of 1.8. This intensity dependence can be explained by the relativistic effect of the quivering electrons. PMID:11800785

  5. Second harmonic generation and two-photon luminescence from colloidal gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Yashunin, D. A.; Korytin, A. I.; Smirnov, A. I.; Stepanov, A. N.


    Second harmonic generation and two-photon luminescence from colloidal gold nanoparticles in the 980-1300 nm wavelength range of exciting femtosecond radiation were investigated experimentally. The measured polarization and spectral characteristics of the second harmonic and two-photon luminescence demonstrate that the observed nonlinear optical signal is determined by the dimers constituting several percent of the total nanoparticle number.

  6. Phase matching in second-harmonic generation using artificial periodic structures.

    NASA Technical Reports Server (NTRS)

    Tang, C. L.; Bey, P. P.


    The use of artificial periodic structures, consisting of spatial modulations of the linear and nonlinear susceptibilities of a nonlinear optical medium, to achieve phase matching in second-harmonic generation is analyzed. Dispersion relations and approximate formulas for the second-harmonic fields generated under various conditions are obtained and used to evaluate the experimental situation.

  7. Second harmonic generation in nanoscale films of transition metal chalcogenides: Taking into account multibeam interference

    NASA Astrophysics Data System (ADS)

    Lavrov, S. D.; Kudryavtsev, A. V.; Shestakova, A. P.; Kulyuk, L.; Mishina, E. D.


    Second harmonic generation 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 harmonic generation 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 harmonic waves generated by this polarization. Calculated second harmonic intensities are presented as functions of dichalcogenide and silicon oxide layer thicknesses. The dependence of the second harmonic 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.

  8. A novel method for detecting second harmonic ultrasonic components generated from fastened bolts

    NASA Astrophysics Data System (ADS)

    Fukuda, Makoto; Imano, Kazuhiko


    This study examines the use of ultrasonic second harmonic components in the quality control of bolt-fastened structures. An improved method for detecting the second harmonic components, from a bolt fastened with a nut, using the transmission method is constructed. A hexagon head iron bolt (12-mm diameter and 25-mm long) was used in the experiments. The bolt was fastened using a digital torque wrench. The second harmonic component increased by approximately 20 dB before and after the bolt was fastened. The sources of second harmonic components were contact acoustic nonlinearity in the screw thread interfaces of the bolt-nut and were the plastic deformation in the bolt with fastening bolt. This result was improved by approximately 10 dB compared with previous our method. Consequently, usefulness of the novel method for detecting second harmonic ultrasonic components generated from fastened bolt was confirmed.

  9. Relativistic second harmonic generation from an S-polarized laser in over-dense plasma

    SciTech Connect

    Adusumilli, K.; Goyal, D.; Tripathi, V. K.


    A relativistic S-polarized short pulse laser impinged obliquely on an overdense plasma thin foil is shown to produce very significant second harmonic in the direction of specular reflection. The second harmonic is P-polarized and is driven by the second harmonic ponderomotive force on electrons in the skin layer. The treatment incorporates the electron density modification by the static ponderomotive force and mass modification due to relativistic effects. The second harmonic reflected amplitude is greatest for an optimum value of the angle of incidence. The conversion efficiency of the second harmonic is greater for higher values of incident laser amplitude and lower values of electron density in the foil. The equivalence between the total ponderomotive force and the radiation pressure force is also demonstrated.

  10. Characterization of muscle contraction with second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Prent, Nicole

    Muscle cells have the ability to change length and generate 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 harmonic generation (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 generate 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

  11. Revealing the second harmonic generation in a femtosecond laser-driven cluster-based plasma by analyzing shapes of Ar XVII spectral lines.


    Oks, Eugene; Dalimier, Elisabeth; Faenov, Anatoly; Pikuz, Tatiana; Fukuda, Yuji; Andreev, Alexander; Koga, James; Sakaki, Hironao; Kotaki, Hideyuki; Pirozhkov, Alexander; Hayashi, Yukio; Skobelev, Igor; Pikuz, Sergei; Kawachi, Tetsuya; Kando, Masaki; Kondo, Kiminori; Zhidkov, Alexei; Kodama, Ryosuke


    We present experiments dealing with a femtosecond laser-driven cluster-based plasma, where by analyzing the nonlinear phenomenon of satellites of spectral lines of Ar XVII, we revealed the nonlinear phenomenon of the generation of the second harmonic of the laser frequency. For performing this analysis we developed new results in the theory of satellites of spectral lines. From such lineshape analysis we found, in particular, that the efficiency of converting the short (40 fs) intense (3x10¹⁸ W/cm²) incident laser light into the second harmonic was 2%. This result is in the excellent agreement with the 2-Dimensional Particle-In-Cell (2D PIC) simulation that we also performed. There is also an order of magnitude agreement between the thresholds for the SHG found from the line shape analysis and from the 2D PIC simulations. PMID:26698990

  12. Adiabatic femtosecond pulse compression and control by using quadratic cascading nonlinearity

    NASA Astrophysics Data System (ADS)

    Zeng, Xianglong; Ashihara, Satoshi; Shimura, Tsutomu; Kuroda, Kazuo


    We experimentally demonstrate that adiabatic compression of femtosecond pulse can be achieved by employing the management of quadratic cascading nonlinearity in quasi-phase-matching gratings. Cascading nonlinearity is not a simple analogy with third-order optical nonlinearity in term of the engineering properties of the magnitude and focusing (or defocusing) nonlinearity. Femtosecond pulse compression is investigated based on type-I (e: o + o) collinear QPM geometry of aperiodically poled MgO-doped LiNbO 3 (MgO: LN). Group-velocity-matching condition is chosen to generate quadratic femtosecond soliton consisting of fundamental (FF) and second harmonic (SH) pulses. Adiabatic-like compression process is observed in the length of 50 mm linearly chirped QPM. Cascading nonlinearity is local managed, instead of dispersion management used in fiber adiabatic soliton compression. Quadratic soliton including FF and SH pulses are obtained from the compression of 95 fs FF pulse in the initial experiments. Dependence on the phase mismatch and group velocity mismatch, cascading nonlinearity has a flexible property and presents a new challenge for exploring femtosecond pulse shaping and control. The demonstrated pulse compression and control based on cascading nonlinearity is useful for generation of shorter pulses with clean temporal profiles, efficient femtosecond second harmonic generation and group-velocity control.

  13. Second harmonic generation in ZnO thin films fabricated by metalorganic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Liu, C. Y.; Zhang, B. P.; Binh, N. T.; Segawa, Y.


    Second harmonic generation (SHG) from ZnO thin films fabricated by metalorganic chemical vapor deposition (MOCVD) technique was carried out. By comparing the second harmonic signal generated in a series of ZnO films with different deposition temperatures, we conclude that a significant part of second harmonic signal is generated 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.

  14. Conversion of the 'Iskra-5' iodine laser to second-harmonic operating mode

    SciTech Connect

    Annenkov, V I; Vinogradskiy, L M; Gaidash, V A; Galakhov, I V; Garanin, Sergey G; Zhidkov, N V; Zubkov, A V; Kalipanov, S V; Kargin, V A; Kirillov, G A; Kovalenko, V P; Kochemasov, G G; Kravchenko, A G; Krotov, V A; Lazarchuk, V P; Lapin, S G; Bespalov, V I; Bredikhin, V I; Ershov, V P; Zil'berberg, V V


    The conversion of the 'Iskra-5' iodine laser to the regime of fusion target irradiation by second harmonic radiation at 657.5 nm is reported. The laser upgrading enabled obtaining from 12 channels a total second-harmonic energy yield of 2.5 kJ, which corresponds to an output power of 5 TW. The conversion efficiency was equal to {approx}50% in experiments with DKDP crystals with an aperture of 35 cm. A series of 12-channel experiments was conducted involving second-harmonic irradiation of microtargets. (lasers)

  15. Calculation of second-harmonic wave pattern generated by focused cylindrical vector beams

    NASA Astrophysics Data System (ADS)

    Ohtsu, A.; Kozawa, Y.; Sato, S.


    We calculated the second-harmonic wave pattern induced by focused cylindrically symmetric, polarized vector beams. The second-order nonlinear polarization was expressed for fundamental electric field components passed through a dielectric interface based on vector diffraction theory. Furthermore, the second-harmonic wave pattern was represented on the basis of the far-field approximate expression derived from the formulation of higher-order harmonic generation including a Green's function. For a (110) zinc selenide crystal, the calculated forward emission patterns of the second-harmonic wave were eight-figure shaped as observed in experiment.

  16. Role of surface plasmon in second harmonic generation from gold nanorods

    SciTech Connect

    Hubert, C.; Billot, L.; Adam, P.-M.; Bachelot, R.; Royer, P.; Grand, J.; Gindre, D.; Dorkenoo, K. D.; Fort, A.


    The role of surface plasmon in second harmonic generation 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 harmonic 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 harmonic. This behavior can be explained by resonant excitation of localized surface plasmon resonances.

  17. Effect of loss on slow-light-enhanced second-harmonic generation in periodic nanostructures.


    Saravi, Sina; Quintero-Bermudez, Rafael; Setzpfandt, Frank; Asger Mortensen, N; Pertsch, Thomas


    We theoretically analyze the dependence of second-harmonic generation efficiency on the group index in periodic optical waveguides with loss. We investigate different possible scenarios of using slow light to enhance the efficiency of this process and show that in some cases there exists a maximally achievable efficiency reached for finite values of the group index at the point of phase-matching. Furthermore, we identify situations for which slow light, surprisingly, does not enhance the second-harmonic generation efficiency. Our results are corroborated by rigorous nonlinear simulations of second-harmonic generation in periodic nanobeam waveguides with loss. PMID:27367114

  18. Phase-matched second harmonic generation and nonlinear phase shift in a Langmuir-Blodgett film waveguide

    NASA Astrophysics Data System (ADS)

    Schrader, Sigurd K.; Flueraru, Costel; Motschmann, Hubert; Brehmer, Ludwig


    Wave-guides have been prepared as y-type Langmuir-Blodgett multilayers from 2-docosylamino-5-nitropyridine (DCANP) on quartz glass substrates. The tensor elements of the LB-films as determined by polarization dependent second harmonic generation (SHG) are (Formula available in paper) The wave-guides were fabricated in a way that the second-order susceptibility changes sign at the nodal plane of the first-order wave-guide mode for s-polarization. In such wave-guides efficient second harmonic generation (SHG) was reached via mode conversion at a fundamental wavelength near 1064 nm. The conversion efficiency reached the extraordinary high value of 8%/W which corresponds to a normalized conversion efficiency of 3600 %/(W cm2). In addition, interferometric measurements have been carried out to study the non-linear phase-shift which the fundamental beam experiences due to non-linear interaction in the wave-guide. From these experiments an apparent intensity-dependent refractive index n2SHG of 2,6 10-13 cm2/W was calculated. This as about 400 times the intensity-dependent refractive as expected from third-order susceptibility of the isotropic material. From that it can be concluded that the main contribution of the intensity-dependent refractive index is connected to cascading of second-order processes.

  19. Second-Harmonic Generation of Electrically Poled Borophosphate Glasses: Effects of Introducing Niobium or Sodium Oxides

    NASA Astrophysics Data System (ADS)

    Nazabal, V.; Fargin, E.; Videau, J. J.; Le Flem, G.; Le Calvez, A.; Montant, S.; Freysz, E.; Ducasse, A.; Couzi, M.


    Second-harmonic generation in poled glasses opens new frontiers in optical material research. Within this context new borophosphate glasses of the Ca(PO3)2-CaB4O7-Na2B4O7-Nb2O5system were synthesized and their second-harmonic generation was evaluated after poling treatment. The enhancement of the second-harmonic signal with niobium oxide content is related to the presence of distorted NbO6octahedra in the former of the glasses and to the increase in third-order susceptibility. The intensity of the measured second-harmonic signal is not dependent on the amount of sodium (100-1000 ppm) introduced into the glass.

  20. Second-harmonic illumination to enhance multispectral digital lensless holographic microscopy.


    Mendoza-Yero, Omel; Carbonell-Leal, Miguel; Lancis, Jesús; Garcia-Sucerquia, Jorge


    Multispectral digital lensless holographic microscopy (MDLHM) operating with second-harmonic illumination is shown. Added to the improvement of the spatial resolution of the previously reported MDLHM operating with near-infrared illumination, this second-harmonic MDLHM shows promise as a tool to study the behavior of biological samples under a broad spectral illumination. This illumination is generated by focusing a highly spatially coherent ultrashort pulsed radiation into an uncoated Type 1 β-BaB2O4 (BBO) nonlinear crystal. The second-harmonic MDLHM allows achieving multispectral images of biological samples with enhanced micrometer spatial resolution. The illumination wavelength of the second-harmonic MDLHM can be tuned by displacing a focusing optics with respect to a pinhole; spatially resolved information at different wavelengths of the sample can then be retrieved. PMID:26974116

  1. Growth and characterization of crystals for IR detectors and second harmonic gereration devices

    NASA Technical Reports Server (NTRS)

    Lal, Ravi B.; Batra, Ashok K.; Rao, Sistla M.; Bhatia, S. S.; Chunduru, Kunar P.; Paulson, Ron; Moorkherji, Tripty K.


    Two types of materials, L-arginine phosphate (LAP) and doped triglycine sulfate (TGS), are examined for their growth characteristics and relevant properties for second harmonic generation and IR detector applications, respectively.

  2. Relativistic second-harmonic generation of a laser from underdense plasmas

    SciTech Connect

    Singh, K.P.; Gupta, D.N.; Yadav, Sushila; Tripathi, V.K.


    A high intensity laser obliquely incident on a vacuum-plasma interface produces second-harmonic radiation in the reflected component. The efficiency of second-harmonic generation 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-harmonic generation increases sharply with laser intensity in the nonrelativistic regime and saturates at higher intensities. The intensity of the second harmonic 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.

  3. Second harmonic generation in carbon nanotubes induced by transversal electrostatic field.


    Trolle, Mads Lund; Pedersen, Thomas Garm


    Carbon nanotubes (CNTs) of armchair and zigzag type contain an inversion centre, and are thus intrinsically unable to generate dipole even-order nonlinearities, such as second harmonic generation (SHG). Breaking the inversion symmetry by application of an external voltage transversal to the CNT axis will, however, induce a second harmonic response. Similarly, additional non-vanishing second harmonic tensor elements will be induced in chiral tubes already displaying an intrinsic response. Many geometries realizing such a setup can be envisaged, e.g., an experimental gate setup or deposition of CNTs on, or integration in, strongly polarized host media, perhaps facilitating a tunable second harmonic response. In this work, we calculate the SHG signal from CNTs under transversally applied electric fields based on a tight-binding model. PMID:23838573

  4. Vector model for polarized second-harmonic generation microscopy under high numerical aperture

    NASA Astrophysics Data System (ADS)

    Wang, Xiang-Hui; Chang, Sheng-Jiang; Lin, Lie; Wang, Lin-Rui; Huo, Bing-Zhong; Hao, Shu-Jian


    Based on the vector diffraction theory and the generalized Jones matrix formalism, a vector model for polarized second-harmonic generation (SHG) microscopy is developed, which includes the roles of the axial component Pz, the weight factor and the cross-effect between the lateral components. The numerical results show that as the relative magnitude of Pz increases, the polarization response of the second-harmonic signal will vary from linear polarization to elliptical polarization and the polarization orientation of the second-harmonic signal is different from that under the paraxial approximation. In addition, it is interesting that the polarization response of the detected second-harmonic signal can change with the value of the collimator lens NA. Therefore, it is more advantageous to adopt the vector model to investigate the property of polarized SHG microscopy for a variety of cases.

  5. Second-Harmonic Generation of Electron-Bernstein Waves in an Inhomogeneous Plasma

    SciTech Connect

    Xiang Nong; Cary, John R.


    In the injection of electron-Bernstein waves (EBW) into a plasma, proposed for plasma heating and current drive in over-dense plasma, conversion of the fundamental to its second harmonic is predicted analytically and observed in computations. The mechanism is traced to the existence of locations where one can have both wave number and frequency matching between the fundamental and its harmonic. Further, at such locations, the second harmonic commonly has minimal group velocity, and this allows the amplitude of the second harmonic to build to values exceeding that of the fundamental at power levels less than anticipated in experiments. The second-harmonic power can then be deposited at half-harmonic resonances of the original wave, often far from the desired location of energy deposition. Estimates for the power at which this is significant are given.

  6. Attachment of second harmonic-active moiety to molecules for detection of molecules at interfaces


    Salafsky, Joshua S.; Eisenthal, Kenneth B.


    This invention provides methods of detecting molecules at an interface, which comprise labeling the molecules with a second harmonic-active moiety and detecting the labeled molecules at the interface using a surface selective technique. The invention also provides methods for detecting a molecule in a medium and for determining the orientation of a molecular species within a planar surface using a second harmonic-active moiety and a surface selective technique.

  7. Using the self-filtering property of a femtosecond filament to improve second harmonic generation.


    Shwa, David; Eisenmann, Shmuel; Marcus, Gilad; Zigler, Arie


    In this paper we demonstrate the use of NIR femtosecond filament for improving the generation of second harmonic using a type I BBO crystal. Using this method the beam propagation factor (M(2)) of the second harmonic 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. PMID:19365469

  8. Intracavity second harmonic generation of chemical oxygen iodine laser with a Brewster cut LBO crystal

    NASA Astrophysics Data System (ADS)

    Shimizu, Tomohiro; Tezuka, Takeo; Chen, Kuntetsu; Hashimoto, Katsuki; Uchiyama, Taro


    Second harmonic generation of chemical oxygen iodine laser was investigated with a Brewster cut LBO crystal. By utilizing a Brewster cut LBO crystal the loss in the resonator can be suppressed. Further, by reducing crystal absorption, the crystal can't be heated and go off phase match or even crack due to thermal stress. We could obtain 16.4 W of second harmonic power and keep out the crystal from being destroyed by the damage of thermal stress.

  9. Optical second harmonic generation of single metallic nanoparticles embedded in a homogeneous medium.


    Butet, Jérémy; Duboisset, Julien; Bachelier, Guillaume; Russier-Antoine, Isabelle; Benichou, Emmanuel; Jonin, Christian; Brevet, Pierre-François


    We report the optical second harmonic generation from individual 150 nm diameter gold nanoparticles dispersed in gelatin. The quadratic hyperpolarizability of the particles is determined and the input polarization dependence of the second harmonic intensity obtained. These results are found in excellent agreement with ensemble measurements and finite element simulations. These results open up new perspectives for the investigation of the nonlinear optical properties of noble metal nanoparticles. PMID:20420409

  10. Enhanced Second Harmonic Generation in AU/AI2O3/AU absorber

    NASA Astrophysics Data System (ADS)

    Huang, Fenglun; Bai, Songang; Li, Qiang; Qu, Yurui; Min, Qiu


    A kind of metal-insulator-metal (MIM) metamaterial absorber for generating second harmonic signal is investigated. The absorbers exhibit high absorption efficiency at the dip and notably enhance the generated second harmonic signal by a factor of over 30, in contrast to an Au/alumina double-layer without Au disk on the top. This study demonstrates the potential of metamaterial absorber for nonlinear photonics.

  11. NONLINEAR OPTICS PHENOMENA: Second harmonic generation from DF laser radiation in ZnGeP2

    NASA Astrophysics Data System (ADS)

    Andreev, Yu M.; Velikanov, S. D.; Yerutin, A. S.; Zapol'skiĭ, A. F.; Konkin, D. V.; Mishkin, S. N.; Smirnov, S. V.; Frolov, Yu N.; Shchurov, V. V.


    We have succeeded in generating the second harmonic of the radiation from a DF laser for the first time, using single crystals of ZnGeP2. For crystals with lengths of 10.1 and 13.6 mm, the overall external efficiencies of the entire oscillator system were 4 and 6.2%. The internal efficiencies of second-harmonic generation in the crystals were 7.6 and 11.8%, respectively.

  12. Synchronous pumping of picosecond dye laser using high efficiency second harmonic generation from optical fibres

    NASA Technical Reports Server (NTRS)

    Lawandy, N. M.; Bernardin, J. P.; Macdonald, R. L.; Demouchy, G.


    The stable operation of a mode-locked dye laser synchronously pumped by the second harmonic of an Nd:YAG laser produced in an Nd codoped germanosilicate optical fiber is reported. The optical fiber preparation technique, which results in a second harmonic conversion efficiency of 2 percent, is described. This optical fiber SHG conversion efficiency is the highest reported to date using a continuous-wave mode-locked laser.

  13. Numerical simulation of polarization-resolved second-harmonic microscopy in birefringent media

    NASA Astrophysics Data System (ADS)

    Gusachenko, Ivan; Schanne-Klein, Marie-Claire


    Polarization-resolved second-harmonic microscopy has recently emerged as a valuable technique for in situ imaging of collagen structure in tissues. Nevertheless, collagen-rich tissues such as tendon, ligament, skin dermis, bone, cornea, or artery exhibit a heterogeneous and anisotropic architecture that results in complex optical properties. While experimental evidence of polarization distortions has been reported in various tissues, the physics of second-harmonic imaging within such tissues is not fully understood yet. In this work, we performed numerical simulations of polarization-resolved second-harmonic generation in a strongly focused regime within a birefringent tissue. We show that vectorial components due to strong focusing have a rather small effect on the measurement of the second-harmonic tensorial response, while birefringence and optical dispersion may affect these measurements dramatically. We show indeed that a difference in the focal field distribution for ordinary and extraordinary waves results in different phase-matching conditions, which strongly affects the relative efficacy of second-harmonic generation for different polarizations. These results are of great interest for extracting reliable quantitative parameters from second-harmonic images.

  14. Two-photon spectral fluorescence lifetime and second-harmonic generation imaging of the porcine cornea with a 12-femtosecond laser microscope

    NASA Astrophysics Data System (ADS)

    Batista, Ana; Breunig, Hans Georg; Uchugonova, Aisada; Morgado, António Miguel; König, Karsten


    Five dimensional microscopy with a 12-fs laser scanning microscope based on spectrally resolved two-photon autofluorescence lifetime and second-harmonic generation (SHG) imaging was used to characterize all layers of the porcine cornea. This setup allowed the simultaneous excitation of both metabolic cofactors, NAD(P)H and flavins, and their discrimination based on their spectral emission properties and fluorescence decay characteristics. Furthermore, the architecture of the stromal collagen fibrils was assessed by SHG imaging in both forward and backward directions. Information on the metabolic state and the tissue architecture of the porcine cornea were obtained with subcellular resolution, and high temporal and spectral resolutions.

  15. Generation of 12 fs deep-ultraviolet pulses by four-wave mixing through filamentation in neon gas.


    Fuji, Takao; Horio, Takuya; Suzuki, Toshinori


    Generation of deep-ultraviolet femtosecond pulses by four-wave mixing through filamentation in neon gas was demonstrated. Fundamental (omega) and second-harmonic (2omega) pulses of 25 fs Ti:sapphire amplifier output were focused into neon gas, and 20 microJ pulses with the center wavelength of 260 nm were produced by a four-wave mixing process, 2omega+2omega-omega?3omega through an ~15 cm filament. Additionally, pulses with an energy of 2 microJ at 200 nm were generated, probably by a cascaded process, 3omega+2omega-omega?4omega. The 260 nm pulses were compressed by a grating-based compressor and characterized by a dispersion-free transient grating frequency-resolved optical gating. The estimated pulse width was 12 fs. PMID:17767278

  16. Kolakoski sequence as an element to radiate giant forward and backward second harmonic signals

    NASA Astrophysics Data System (ADS)

    Parvini, T. S.; Tehranchi, M. M.; Hamidi, S. M.; Sarkarati, S.


    We propose a novel type of aperiodic one-dimensional photonic crystal structures which can be used for generating giant forward and backward second harmonic signals. The studied structure is formed by stacking together the air and nonlinear layers according to the Kolakoski self-generation scheme in which each nonlinear layer contains a pair of antiparallel 180° poled LiNbO3 crystal layers. For different generation stages of the structure, conversion efficiencies of forward and backward second harmonic waves have been calculated by nonlinear transfer matrix method. Numerical simulations show that conversion efficiencies in the Kolakoski-based multilayer are larger than the perfect ones for at least one order of magnitude. Especially for 33rd and 39th generation stages, forward second harmonic wave are 42 and 19 times larger, respectively. In this paper, we validate the strong fundamental field enhancement and localization within Kolakoski-based multilayer due to periodicity breaking which consequently leads to very strong radiation of backward and forward second harmonic signals. Following the applications of analogous aperiodic structures, we expect that Kolakosi-based multilayer can play a role in optical parametric devices such as multicolor second harmonic generators with high efficiency.

  17. Kolakoski sequence as an element to radiate giant forward and backward second harmonic signals

    SciTech Connect

    Parvini, T. S.; Tehranchi, M. M. E-mail:; Hamidi, S. M. E-mail:; Sarkarati, S.


    We propose a novel type of aperiodic one-dimensional photonic crystal structures which can be used for generating giant forward and backward second harmonic signals. The studied structure is formed by stacking together the air and nonlinear layers according to the Kolakoski self-generation scheme in which each nonlinear layer contains a pair of antiparallel 180° poled LiNbO{sub 3} crystal layers. For different generation stages of the structure, conversion efficiencies of forward and backward second harmonic waves have been calculated by nonlinear transfer matrix method. Numerical simulations show that conversion efficiencies in the Kolakoski-based multilayer are larger than the perfect ones for at least one order of magnitude. Especially for 33rd and 39th generation stages, forward second harmonic wave are 42 and 19 times larger, respectively. In this paper, we validate the strong fundamental field enhancement and localization within Kolakoski-based multilayer due to periodicity breaking which consequently leads to very strong radiation of backward and forward second harmonic signals. Following the applications of analogous aperiodic structures, we expect that Kolakosi-based multilayer can play a role in optical parametric devices such as multicolor second harmonic generators with high efficiency.

  18. Monitoring photoaging by use of multiphoton fluorescence and second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Lin, Sung-Jan; Jee, Shiou-Hwa; Chan, Jung-Yi; Wu, Ruei-Jr; Lo, Wen; Tan, Hsin-Yuan; Lin, Wei-Chou; Chen, Jau-Shiuh; Young, Tai-Horng; Hsu, Chih-Jung; Dong, Chen-Yuan


    It is a field of great interest to develop therapies to rejuvenate photoaged skin. However, the treatment response can not be ideally determined due to lack of a reliable non-invasive method to quantify photoaging. In this study, the photoaging process of skin is investigated by use of a multiphoton fluorescence and second harmonic generation microscopy. We obtain the autofluorescence and second harmonic generation images of superficial dermis from facial skin of individuals of different ages. The results show that autofluorescence signals increase with age while second harmonic generation signals decrease with age. The results are consistent with the histological findings in which collagen is progressively replaced by elastic fibers. In the case of severe photoaging, solar elastosis can be clearly demonstrated by the presence of thick curvy autofluorescent materials in the superficial dermis. We propose a second harmonic generation to autofluorescence aging index of dermis to quantify the photoaging changes. This index is shown to be a good indicator of photoaging. Our results suggest that multiphoton fluorescence and second harmonic generation microscopy can be developed into a non-invasive imaging modelity for the clinical evaluation of photoaging.

  19. Efficient broadband 400  nm noncollinear second-harmonic generation of chirped femtosecond laser pulses in BBO and LBO.


    Gobert, O; Mennerat, G; Maksimenka, R; Fedorov, N; Perdrix, M; Guillaumet, D; Ramond, C; Habib, J; Prigent, C; Vernhet, D; Oksenhendler, T; Comte, M


    We report on 400 nm broadband type I frequency doubling in a noncollinear geometry with pulse-front-tilted and chirped femtosecond pulses (λ =800  nm; Fourier transform limited pulse duration, 45 fs). With moderate power densities (2 to 10  GW/cm2) thus avoiding higher-order nonlinear phenomena, the energy conversion efficiency was up to 65%. Second-harmonic pulses of Fourier transform limited pulse duration shorter than the fundamental wave were generated, exhibiting good beam quality and no pulse-front tilt. High energy (20 mJ/pulse) was produced in a 40 mm diameter and 6 mm thick LBO crystal. To the best of our knowledge, this is the first demonstration of this optical configuration with sub-100-fs pulses. Good agreement between experimental results and simulations is obtained. PMID:24787591

  20. Second harmonic detection in the electrochemical strain microscopy of Ag-ion conducting glass


    Yang, Sangmo; Okatan, Mahmut Baris; Paranthaman, Mariappan Parans; Jesse, Stephen; Noh, Tae Won; Kalinin, Sergei V.


    The first and second harmonic electromechanical responses and their cross-correlation in Ag-ion conducting glass were investigated using band-excitation electrochemical strain microscopy (ESM). Consecutive ESM images with increasing magnitudes of the applied AC voltage allowed observation of not only reversible surface displacement but also irreversible silver nanoparticle formation above a certain threshold voltage. The second harmonic ESM response was anticorrelated with the first harmonic response in many local regions. Furthermore, the nucleation sites of silver nanoparticles were closely related to the anti-correlated regions, specifically, with low second harmonic and high first harmonic ESM responses. The possible origins of the second harmonicmore » ESM response are discussed.« less

  1. Is the second harmonic method applicable for thin films mechanical properties characterization by nanoindentation?

    NASA Astrophysics Data System (ADS)

    Guillonneau, G.; Kermouche, G.; Teisseire, J.; Barthel, E.; Bec, S.; Loubet, J.-L.


    The second harmonic method is a dynamic indentation technique independent of the direct indentation depth measurement. It can be used to determine near-surface mechanical properties of bulk materials more precisely than classical dynamic nanoindentation. In this paper, the second harmonic method is extended to the measurement of the mechanical properties of thin poly(methyl methacrylate) (PMMA) layers deposited onto silicon wafers. It is shown that this new technique gives precise results at small depths (less than 100 nm), even for films with a thickness lower than 500 nm, which was not possible to achieve with the classical continuous stiffness measurement method. However, experimental and numerical results obtained both with classical nanoindentation and second harmonic methods differ at high indentation depth. Using finite element (FE) simulations and AFM measurements, it is shown that the contact depth calculation with classical models can explain this difference.

  2. Second-harmonic generation of electrically poled borophosphate glasses: Effects of introducing niobium or sodium oxides

    SciTech Connect

    Nazabal, V.; Fargin, E.; Videau, J.J.


    Second-harmonic generation in poled glasses opens new frontiers in optical material research. Within this context new boro-phosphate glasses of the Ca(PO{sub 3})2-CaB{sub 4}O{sub 7}-Na{sub 2}B{sub 4}O{sub 7}-Nb{sub 2}O{sub 5} system were synthesized and their second-barmonic generation was evaluated after poling treatment. The enhancement of the second-harmonic signal with niobium oxide content is related to the presence of distorted NbO{sub 6} octahedra in the former of the glasses and to the increase in third-order susceptibility. The intensity of the measured second-harmonic signal is not dependent on the amount of sodium (100-1000 ppm) introduced into the glass.

  3. Enhanced second-harmonic-generation detection of collagen by means of optical wavefront shaping

    NASA Astrophysics Data System (ADS)

    Thompson, Jonathan V.; Throckmorton, Graham A.; Hokr, Brett H.; Yakovlev, Vladislav V.


    Second-harmonic generation (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 harmonic generation on the spatial phase of the pump laser. Here, we demonstrate that wavefront shaping can be used to enhance the generation of second harmonic light from collagen fibrils even when scattering is low or non-existent.

  4. Second-harmonic generation in mixed stilbazium salt/arachidic acid Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Liu, Liying; Zheng, Jiabiao; Wang, Wencheng; Zhang, Zhiming; Tao, Fenggang; Xu, Linxiao; Hu, Jiacong


    A stilbazium salt was synthesized and its second-order molecular polarizability was deduced to be 1.2×10 -27 esu. Measurements of second-harmonic generation and small-angle X-ray diffraction on Langmuir-Blodgett films of the stilbazium salt/arachide acid mixtures showed that the mixed compounds with molar ratios of 1:2 and 1:5 could form multilayers with large second- order optical nonlinearity. Second harmonic generation study on the alternate multilayers of stilbazium salt/arachide acid and arachidic acid showed that the second-harmonic signals were increasing monotonously up to 80 bilayers, but the increment was lower than the value predicted theoretically by the quadratic law. Possible reasons are discussed.

  5. Efficient second-harmonic generation in micrometer-thick slabs with indefinite permittivity

    NASA Astrophysics Data System (ADS)

    Ciattoni, A.; Spinozzi, E.


    We theoretically predict efficient optical second-harmonic generation (SHG) from a micrometer-thick slab consisting of a quadratic nonlinear anisotropic medium whose linear principal permittivities have, at the fundamental wavelength, real parts of different signs (indefinite permittivity) and magnitude smaller than 1. We show that, by illuminating the slab with a p-polarized fundamental wave (with intensity of a few MW/cm2), highly efficient scattering of the second-harmonic field occurs in conditions at which the slab is linearly fully transparent for the fundamental wave. The high efficiency of the SHG process stems from the enhancement of the longitudinal field, perpendicular to the slab surface, produced by the very small value of the slab dielectric permittivities. We investigate the role played by medium losses, showing that, even in the strong-absorption regime, the described process yields a second-harmonic field which is much stronger than that produced by a standard (not indefinite) nonlinear slab.

  6. Vector electron paramagnetic resonance spectroscopy with first and second harmonic displays of ferrihemoglobin.


    Watari, H; Murakami, M; Seo, Y; Shimoyama, Y


    Superimposed plots of electron paramagnetic resonance spectra with the first and second harmonic displays of ferrihemoglobin at pH 9.1 and 90 K were measured at 20 degree intervals of phase angle using a phase-sensitive detector. The high spin signal in the g = 6 region was observed in both displays, and a small splitting of the signal was found in the calculated amplitude spectrum of the second harmonic display, with g values of 5.95 and 6.05. Low spin signals were observed at g = 2.55, 2.25 and 1.82 in both harmonic displays. A signal in the g = 2.05 region was observed only in the second harmonic display. The signal is probably associated with the low spin spectrum; however, its origin is obscure. PMID:2547369

  7. In-phase synchronization of array laser using intra-Talbot-cavity second harmonic generation

    NASA Astrophysics Data System (ADS)

    Hirosawa, Kenichi; Shohda, Fumio; Yanagisawa, Takayuki; Kannari, Fumihiko


    Talbot cavity is passive method to synchronize the phase of array lasers. Because the Talbot cavity does not need any electrical feedback systems, we believe that Talbot cavity is the most suitable technique to combine a considerable number of laser array into a compact system. A well-known drawback of the Talbot cavity is that it can produce out-phased array and their far-field image has 2-peak profile. To solve this drawback, we developed a frequency doubled laser array based on intra-Talbot-cavity second harmonic generation. Basic concept is second harmonic generation of the out-phased array generated from the Talbot cavity. Because the second harmonic wave is generated proportionally to the square of the fundamental wave, out-phase flips to in-phase. Our Talbot cavity is composed of a pumping 808-nm laser diode array with 15 emitters, an Nd:YVO4 planar waveguide, a PPLN planar waveguide, an f =10 cylindrical lens, and an output coupler (high reflection for 1064 nm and high transition to 532 nm). The pump laser beams are directly launched into the Nd:YVO4. The fundamental wave (1064 nm) oscillates between the Nd:YVO4 and the output coupler and generates second harmonic wave (532 nm) at the PPLN placed next to the Nd:YVO4. The round-trip optical path of the cavity length is set to 1/2 Talbot length so that Talbot cavity forms for the fundamental wave. As a result, we obtained 1-peak far-field image of second harmonic wave from the intra-Talbot-cavity second harmonic generation.

  8. Second harmonic generation in photonic crystal cavities in (111)-oriented GaAs

    SciTech Connect

    Buckley, Sonia Radulaski, Marina; Vučković, Jelena; Biermann, Klaus


    We demonstrate second harmonic generation 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 generated second harmonic 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.

  9. Second-harmonic generation of light at 245 nm in a lithium tetraborate whispering gallery resonator.


    Fürst, Josef U; Buse, Karsten; Breunig, Ingo; Becker, Petra; Liebertz, Josef; Bohatý, Ladislav


    A millimeter-sized, monolithic whispering gallery resonator made of a lithium tetraborate, Li2B4O7, crystal was employed for doubly resonant second-harmonic generation with a continuous-wave laser source at 490 nm. An intrinsic quality factor of 2×10(8) was observed at the pump wavelength. A conversion efficiency of 2.2% was attained with 5.9 mW of mode-matched pump power. In the lithium tetraborate resonator, it is feasible to achieve phase-matching of second-harmonic generation for pump wavelengths between 486 and 506 nm. PMID:25927751

  10. Radially polarized annular beam generated through a second-harmonic-generation process.


    Sato, Shunichi; Kozawa, Yuichi


    A radially polarized beam with an annular intensity pattern was generated through a second-harmonic-generation 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-harmonic 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. PMID:19838261

  11. Resonant second harmonic generation in a gallium nitride two-dimensional photonic crystal on silicon

    NASA Astrophysics Data System (ADS)

    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.


    We demonstrate second harmonic generation 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 harmonic generation is evidenced by the spectral range of the emitted signal, the quadratic power dependence vs. input power, and the spectral dependence of second harmonic signal. The harmonic emission pattern is correlated to the harmonic polarization generated by the second-order nonlinear susceptibilities χzxx (2 ), χzyy (2 ) and the electric fields of the fundamental cavity mode.

  12. Imaging the bipolarity of myosin filaments with Interferometric Second Harmonic Generation microscopy

    PubMed Central

    Rivard, Maxime; Couture, Charles-André; Miri, Amir K.; Laliberté, Mathieu; Bertrand-Grenier, Antony; Mongeau, Luc; Légaré, François


    We report that combining interferometry with Second Harmonic Generation (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 Harmonic Generation (ISHG) images reveal that each side of the myosin filaments composing the A band of the sarcomere generates 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

  13. Second-harmonic generation in resonant waveguide gratings incorporating ionic self-assembled monolayer polymer films.


    Purvinis, Georgeanne; Priambodo, Purnomo S; Pomerantz, Martin; Zhou, Ming; Maldonado, Theresa A; Magnusson, Robert


    Experimental results on resonantly excited second-harmonic generation (SHG) in a periodic ionically self-assembled monolayer (ISAM) film are reported. A double-layer guided-mode resonance filter (GMRF) structure is coated with 40 bilayers of pyrlium-based chi(2) ISAM thin film and excited with the fundamental of a Nd:YAG laser. Enhanced second-harmonic conversion in the ISAM film is achieved because of the local field enhancement associated with the fundamental resonating leaky mode. This method of SHG is particularly promising, as the ISAM films under investigation exhibit anomalous dispersion that may be applied for phase matching to improve nonlinear conversion efficiency. PMID:15182001

  14. Second-harmonic generation in resonant waveguide gratings incorporating ionic self-assembled monolayer polymer films

    NASA Astrophysics Data System (ADS)

    Purvinis, Georgeanne; Priambodo, Purnomo S.; Pomerantz, Martin; Zhou, Ming; Maldonado, Theresa A.; Magnusson, Robert


    Experimental results on resonantly excited second-harmonic generation (SHG) in a periodic ionically self-assembled monolayer (ISAM) film are reported. A double-layer guided-mode resonance filter (GMRF) structure is coated with 40 bilayers of pyrlium-based chi^(2) ISAM thin film and excited with the fundamental of a Nd:YAG laser. Enhanced second-harmonic conversion in the ISAM film is achieved because of the local field enhancement associated with the fundamental resonating leaky mode. This method of SHG is particularly promising, as the ISAM films under investigation exhibit anomalous dispersion that may be applied for phase matching to improve nonlinear conversion efficiency.

  15. Angle-Resolved Second-Harmonic Light Scattering from Colloidal Particles

    SciTech Connect

    Yang, N.; Angerer, W. E.; Yodh, A. G.


    We report angle-resolved second-harmonic generation (SHG) measurements from suspensions of centrosymmetric micron-size polystyrene spheres with surface-adsorbed dye (malachite green). The second-harmonic scattering profiles differ qualitatively from linear light scattering profiles of the same particles. We investigated these radiation patterns using several polarization configurations and particle diameters. We introduce a simple Rayleigh-Gans-Debye model to account for the SHG scattering anisotropy. The model compares favorably with our experimental data. Our measurements suggest scattering anisotropy may be used to isolate particle nonlinear optics from other bulk nonlinear optical effects in suspension.

  16. Microstrip Hairpin Bandpass Filter Using Modified Minkowski Fractal-Shape for Suppression of Second Harmonic

    NASA Astrophysics Data System (ADS)

    Lalbakhsh, Ali; Lotfi Neyestanak, Abbas Ali; Naser-Moghaddasi, Mohammad

    In this paper, a novel microstrip hairpin-line bandpass filter which employs a modified Minkowski fractal shape is proposed. Although conventional hairpin-line filters are popular for RF front ends, they suffer from undesired spurious responses located at the second harmonic, which causes asymmetry in the upper skirt band. By proper design, the second harmonic of fractal filters can be significantly suppressed through the use of fractal shape. To validate this novel geometry, the proposed filters are fabricated and measured. Simulated results are in good agreement with measured results.

  17. Second-harmonic generation imaging of metal nano-objects with cylindrical vector beams.


    Bautista, Godofredo; Huttunen, Mikko J; Mäkitalo, Jouni; Kontio, Juha M; Simonen, Janne; Kauranen, Martti


    We introduce an imaging technique based on second-harmonic generation with cylindrical vector beams that is extremely sensitive to three-dimensional orientation and nanoscale morphology of metal nano-objects. Our experiments and second-harmonic field calculations based on frequency-domain boundary element method are in very good agreement. The technique provides contrast for structural features that cannot be resolved by linear techniques or conventional states of polarization and shows great potential for simple and cost-effective far-field optical imaging in plasmonics. PMID:22587307

  18. Local field enhanced second-harmonic response of organic nanofibers deposited on encapsulated plasmonic substrates

    NASA Astrophysics Data System (ADS)

    Kostiučenko, Oksana; Leißner, Till; Brewer, Jonathan R.; Tamulevičius, Tomas; Tamulevičius, Sigitas; Fiutowski, Jacek; Rubahn, Horst-Günter


    In this work, enhancement of the second harmonic response of organic nanofibers deposited on encapsulated and robust plasmonic active substrate is experimentally demonstrated. Organic nanofibers grown from functionalized paraquaterphenylene (CNHP4) molecules have been transferred on lithographically defined regular arrays of gold nanostructures, which subsequently have been coated with thin films of diamond-like carbon with 25, 55 and 100 nm thickness. Femtosecond laser scanning microscopy enables us to identify enhancement of the second harmonic response of the fibers. This is facilitated by a preservation of the field enhancement effects, which appear on the nanostructures and remain significant on top of the coating layer.

  19. Ultrashort pulse chirp measurement via transverse second-harmonic generation in strontium barium niobate crystal

    SciTech Connect

    Trull, J.; Wang, B.; Parra, A.; Vilaseca, R.; Cojocaru, C.; Sola, I.; Sheng, Y.


    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 harmonic generation. The dependence of the transverse width of the second harmonic 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.

  20. Mode matching in multiresonant plasmonic nanoantennas for enhanced second harmonic generation

    NASA Astrophysics Data System (ADS)

    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


    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 harmonic generation. Here, we describe doubly-resonant single-crystalline gold nanostructures with no axial symmetry displaying spatial mode overlap at both the excitation and second harmonic wavelengths. The combination of these features allows the attainment of a nonlinear coefficient for second harmonic generation of ˜5 × 10-10 W-1, enabling a second harmonic 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.

  1. Second harmonic generation from metamaterials strongly coupled to intersubband transitions in quantum wells

    SciTech Connect

    Campione, Salvatore; Benz, Alexander; Brener, Igal; Sinclair, Michael B.; Capolino, Filippo


    We theoretically analyze the second harmonic generation 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 harmonic 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 harmonic signals in both the forward and backward directions, with the forward efficiency being larger. We calculate the overall second harmonic 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.

  2. Two-pass-internal second-harmonic generation using a prism coupler.

    NASA Technical Reports Server (NTRS)

    Gonzalez, D. G.; Nieh, S. T. K.; Steier, W. H.


    A dispersive quartz prism is used to couple the total second harmonic generated 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.

  3. Mode matching in multiresonant plasmonic nanoantennas for enhanced second harmonic generation.


    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


    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 harmonic generation. Here, we describe doubly-resonant single-crystalline gold nanostructures with no axial symmetry displaying spatial mode overlap at both the excitation and second harmonic wavelengths. The combination of these features allows the attainment of a nonlinear coefficient for second harmonic generation of ∼5 × 10(-10) W(-1), enabling a second harmonic 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

  4. Continuous-variable Einstein-Podolsky-Rosen paradox with traveling-wave second-harmonic generation

    SciTech Connect

    Olsen, M.K.


    The Einstein-Podolsky-Rosen paradox and quantum entanglement are at the heart of quantum mechanics. Here we show that single-pass traveling-wave second-harmonic generation 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.

  5. Evidence of multipolar response of Bacteriorhodopsin by noncollinear second harmonic generation.


    Bovino, F A; Larciprete, M C; Sibilia, C; Váró, G; Gergely, C


    Noncollinear second harmonic generation from a Bacteriorhodopsin (BR) oriented multilayer film was systematically investigated by varying the polarization state of both fundamental beams. Both experimental results and theoretical simulations, show that the resulting polarization mapping is an useful tool to put in evidence the optical chirality of the investigated film as well as the corresponding multipolar contributions to the nonlinear. PMID:22714524

  6. Soliton polarization rotation and switching in type II second-harmonic generation

    NASA Astrophysics Data System (ADS)

    Mollame, Riccardo; Trillo, Stefano; Assanto, Gaetano


    We predict that solitary waves of dispersive type II second-harmonic generation may experience large uniform nonlinear polarization rotations. The nonlinear medium followed by a polarization analyzer permits undistorted all-optical switching of pulses controlled by the input polarization.

  7. Second-harmonic generation excited by a rotating Laguerre-Gaussian beam

    SciTech Connect

    Petrov, Dmitri


    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-harmonic generation nonlinear process.

  8. Optical bistability and second-harmonic generation in thin film coupled cavity photonic crystal structures

    NASA Astrophysics Data System (ADS)

    Diao, Liyong

    This thesis deals with design, fabrication and modeling of bistable and multi-stable switching dynamics and second-harmonic generation in two groups of thin film coupled cavity photonic crystal structures. The first component studies optical bistability and multistability in such structures. Optical bistability and multistability are modelled by a nonlinear transfer matrix method. The second component is focused on the modelling and experimental measurement of second-harmonic generation in such structures. It is found that coupled cavity structures can reduce the threshold and index change for bistable operation, but single cavity structures can do the same. However, there is a clear advantage in using coupled cavity structures for multistability in that the threshold for multistability can be reduced. Second-harmonic generation is enhanced by field localization due to the resonant effect at the fundamental wavelength in single and coupled cavity structures by simulated and measured results. The work in this thesis makes three significant contributions. First, in the successful fabrication of thin film coupled cavity structures, the simulated linear transmissions of such structures match those of the fabricated structures almost exactly. Second, the newly defined figure of merit at the maximum transmission point on the bistable curve can be used to compare the material damage tolerance to any other Kerr effect nonlinear gate. Third, the simulated second-harmonic generation agrees excellently with experimental results. More generally optical thin film fabrication has commercial applications in many industry sections, such as electronics, opto-electronics, optical coating, solar cell and MEMS.

  9. Second harmonic generation by self-focusing of intense hollow Gaussian laser beam in collisionless plasma

    NASA Astrophysics Data System (ADS)

    Purohit, Gunjan; Rawat, Priyanka; Gauniyal, Rakhi


    The effect of self focused hollow Gaussian laser beam (HGLB) (carrying null intensity in center) on the excitation of electron plasma wave (EPW) and second harmonic generation (SHG) has been investigated in collisionless plasma, where relativistic-ponderomotive and only relativistic nonlinearities are operative. The relativistic change of electron mass and the modification of the background electron density due to ponderomotive nonlinearity lead to self-focusing of HGLB in plasma. Paraxial ray theory has been used to derive coupled equations for the self focusing of HGLB in plasma, generation of EPW, and second harmonic. These coupled equations are solved analytically and numerically to study the laser intensity in the plasma, electric field associated with the excited EPW, and the power of SHG. Second harmonic emission is generated due to nonlinear coupling between incident HGLB and EPW satisfying the proper phase matching conditions. The results show that the effect of including the ponderomotive nonlinearity is significant on the generation of EPW and second harmonic. The electric field associated with EPW and the power of SHG are found to be highly sensitive to the order of the hollow Gaussian beam.

  10. Measurement of the vector character of electric fields by optical second-harmonic generation.


    Dadap, J I; Shan, J; Weling, A S; Misewich, J A; Nahata, A; Heinz, T F


    We present a scheme for the determination of the vector nature of an electric field by optical second-harmonic generation. We demonstrate the technique by mapping the two-dimensional electric-field vector of a biased transmission line structure on silicon with a spatial resolution of ~10mum . PMID:18073940

  11. High conversion efficiency pumped-cavity second harmonic generation of a diode laser

    SciTech Connect

    Keicher, D.M.


    To investigate the feasibility of producing a compact, efficient blue laser source, pumped-cavity second harmonic generation 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 harmonic 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 harmonic output power is anticipated by reducing the input mirror reflectivity to better impedance-match the cavity. With this relatively low second harmonic conversion, the power to light conversion is 7.8%.

  12. Wearable Second Harmonic Generation Imaging: The Sarcomeric Bridge to the Clinic.


    Williams, Justin C; Campagnola, Paul J


    Imaging of sarcomere dynamics in vivo in patients has significant clinical importance, as the structure and function is altered in numerous pathologies. In this issue of Neuron, Schnitzer and coworkers (Sanchez et al., 2015) demonstrate this capability through a miniature, wearable Second Harmonic Generation microscope. PMID:26687213

  13. Second Harmonic Generation in CdTe Plate by Free Electron Laser

    NASA Astrophysics Data System (ADS)

    Yamauchi, Toshihiko; Kikuzawa, Nobuhiro; Minehara, Eisuke; Nagai, Ryoji; Nishimori, Nobuyuki; Sawamura, Masaru; Hajima, Ryoichi; Shizuma, Toshiyuki; Hayakawa, Takehito


    The second harmonic generation (SHG) signal converted from the 22 μm input wavelength of free electron laser (FEL) is observed using a non-birefringent CdTe crystal. The conversion efficiency of SHG is experimentally obtained to be ˜3× 10-5%/(MWcm-2).

  14. Study of the emission spectra of a 1320-nm semiconductor disk laser and its second harmonic

    NASA Astrophysics Data System (ADS)

    Gochelashvili, K. S.; Derzhavin, S. I.; Evdokimova, O. N.; Zolotovskii, I. O.; Podmazov, S. V.


    The spectral characteristics of an optically pumped external-cavity semiconductor disk laser near λ = 1320 nm are studied experimentally. Intracavity second harmonic generation is obtained using an LBO nonlinear crystal. The output power at a wavelength of 660 nm in the cw regime was 620 mW, and the peak power in the pulsed regime was 795 mW.

  15. Second harmonic generation by propagation of a p-polarized obliquely incident laser beam in underdense plasma

    SciTech Connect

    Jha, Pallavi; Agrawal, Ekta


    An analytical study of second harmonic generation 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 harmonic 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 harmonic efficiency increases with the angle of incidence while the detuning length decreases. The second harmonic amplitude vanishes at normal incidence of the laser beam.

  16. Optical parametric oscillators synchronously pumped by fundamental and second harmonic radiation of femtosecond Yb:KGW laser

    NASA Astrophysics Data System (ADS)

    StankevičiÅ«tÄ--, K.; PipinytÄ--, I.; Vengelis, J.; MarcinkevičiÅ«tÄ--, A.; Å uminas, R.; Grigonis, R.; Eckardt, R. C.; Sirutkaitis, V.


    We present experimental data obtained during investigation of synchronously pumped optical parametric oscillators (SPOPO's) pumped by fundamental (1030 nm) and second harmonic (515 nm) radiation of mode-locked Yb:KGW laser, providing 105 fs pulses at 76 MHz repetition rate with an average power of 4 W. Different nonlinear crystals such as beta barium borate (BBO), and periodically poled lithium niobate (PPLN) and MgO doped PPLN (MgO:PPLN) were tested to estimate wavelength tuning capabilities and SPOPO's efficiency. Rotation of BBO nonlinear crystal and SPOPO's cavity length variation and, in the case of SPOPO based on PPLN, change of grating period and cavity length allowed signal wavelength tuning in 630 - 1030 nm and 1350 - 1700 nm spectral ranges, respectively. Parametric light conversion from pump power to signal power efficiency was as high as 25 %. Including the idler pulses the tuning ranges were from 630 to 2400 nm and from 1350 to 4000 nm in case of BBO and PPLN crystals, respectively. SPOPO based on BBO wsithout intracavity group velocity dispersion (GVD) compensation generates longer than transform limited pulses, so SPOPO based on BBO with dispersive prisms were investigated.

  17. Optical second-harmonic imaging of Pb{sub x}Cd{sub 1-x}Te ternary alloys

    SciTech Connect

    Scheidt, T.; Rohwer, E.G.; Bergmann, H.M. von; Saucedo, E.; Dieguez, E.; Fornaro, L.; Stafast, H.


    We employ femtosecond laser pulses (80 fs, 1.59 eV, and 80 MHz) to study the optical second-harmonic (SH) response of Pb{sub x}Cd{sub 1-x}Te ternary alloys (x about 0.2) grown by the vertical Bridgman method. The alloy segregates into a Pb-rich and a Cd-rich phase, the latter dominating the SH response of the ternary alloy by at least two orders of magnitude. Several sample regions show a regular layer-by-layer accommodation of the Pb-rich and Cd-rich phases as seen by a periodic alternation of the alloy's SH response on a {approx}10-{mu}m length scale. Furthermore, we employ polarization-resolved SH imaging as well as SH imaging at different azimuthal angles to obtain spatially resolved mappings of the sample, which are sensitive to the composition as well as the growth orientation of the Pb{sub x}Cd{sub 1-x}Te material system. We observe an azimuthal phase shift of approximately 30 deg. between coherent macroscopic regions (several mm{sup 2}) in the Cd-rich phase of the ternary alloy. We interpret these regions as large area crystalline grains of (111) and (411) crystal orientations and approximately equal composition. Hence, SH imaging is shown to spatially resolve regions of different growth directions within the Pb{sub x}Cd{sub 1-x}Te sample.

  18. Femtosecond laser corneal surgery with in situ determination of the laser attenuation and ablation threshold by second harmonic generation

    NASA Astrophysics Data System (ADS)

    Plamann, Karsten; Nuzzo, Valeria; Albert, Olivier; Mourou, Gérard A.; Savoldelli, Michèle; Dagonet, Françoise; Donate, David; Legeais, Jean-Marc


    Femtosecond lasers start to be routinely used in refractive eye surgery. Current research focuses on their application to glaucoma and cataract surgery as well as cornea transplant procedures. To avoid unwanted tissue damage during the surgical intervention it is of utmost importance to maintain a working energy just above the ablation threshold and maintain the laser energy at this working point independently of the local and global tissue properties. To quantify the attenuation of the laser power density in the tissue by absorption, scattering and modification of the point spread function we monitor the second harmonic radiation generated in the collagen matrix of the cornea when exposed to ultrashort laser pulses. We use a CPA system with a regenerative amplifier delivering pulses at a wavelength of 1.06 μm, pulse durations of 400 fs and a maximum energy of 60 μJ. The repetition rate is adjustable from single shot up to 10 kHz. The experiments are performed on human corneas provided by the French Eye bank. To capture the SHG radiation we use a photomultiplier tube connected to a lockin amplifier tuned to the laser repetition rate. The measured data indicates an exponential decay of the laser beam intensity in the volume of the sample and allows for the quantification of the attenuation coefficient and its correlation with the optical properties of the cornea. Complementary analyses were performed on the samples by ultrastructural histology.

  19. Cascaded four-wave mixing for broadband tunable laser sideband generation.


    Liu, Weimin; Zhu, Liangdong; Wang, Liang; Fang, Chong


    We demonstrate the versatile broadband wavelength tunability of frequency upconverted multicolor cascaded four-wave-mixing (CFWM) signals spanning the continuous wavelength range from UV to near IR in a thin type-I BBO crystal using 35 fs, 800 nm fundamental and chirped IR supercontinuum white light pulses. Two sets of spatially dispersed CFWM laser sidebands are concomitantly generated from two incident pulses as well as their second-harmonic-generation and sum-frequency-generation pulses in a crossing geometry. The tunable cascaded signals with ultrabroad bandwidth can be readily achieved via spatially rotating the BBO crystal to different phase-matching conditions and temporally varying the time delay between the two incident near-IR pulses. PMID:23722739

  20. Two-dimensional phase transformation probed by second harmonic generation: Oscillatory transformation of the K/Al(111) system

    SciTech Connect

    Ying, Z.C.; Plummer, E.W. |


    The technique of optical second harmonic generation 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 harmonic generation is analyzed in detail.

  1. Spectral behavior of second harmonic signals from organic and non-organic materials in multiphoton microscopy

    PubMed Central

    Ehmke, Tobias; Knebl, Andreas; Reiss, Stephan; Fischinger, Isaak R.; Seiler, Theo G.; Stachs, Oliver; Heisterkamp, Alexander


    Multimodal nonlinear microscopy allows imaging of highly ordered biological tissue due to spectral separation of nonlinear signals. This requires certain knowledge about the spectral distribution of the different nonlinear signals. In contrast to several publications we demonstrate a factor of 122 relating the full width at half maximum of a gaussian laser pulse spectrum to the corresponding second harmonic pulse spectrum in the spatial domain by using a simple theoretical model. Experiments on monopotassium phosphate crystals (KDP-crystals) and on porcine corneal tissue support our theoretical predictions. Furthermore, no differences in spectral width were found for epi- and trans-detection of the second harmonic signal. Overall, these results may help to build an optimized multiphoton setup for spectral separation of nonlinear signals. PMID:26339527

  2. Second harmonic generation microscopy reveals hidden polar organization in fluoride doped MIL-53(Fe).


    Markey, Karen; Putzeys, Tristan; Horcajada, Patricia; Devic, Thomas; Guillou, Nathalie; Wübbenhorst, Michael; Cleuvenbergen, Stijn Van; Verbiest, Thierry; De Vos, Dirk E; van der Veen, Monique A


    Polar metal-organic frameworks have potential applications as functional non-linear optical, piezoelectric, pyroelectric and ferroelectric materials. Using second harmonic generation microscopy we found that fluoride doping of the microporous iron(iii) terephthalate MOF MIL-53(Fe) induces a polar organization in its structure, which was not previously detected with XRD. The polar order is only observed when both fluoride and guest molecules are present, and may be related to a complex interplay between the adsorbates and the framework, leading to a modification of the positioning of fluoride in the inorganic Fe-chains. Combined polarized second harmonic generation microscopy and scanning pyroelectric microscopy show that the polar axis is unidirectional and of the same sense over the whole crystal, extending up to 100 micrometers. This finding shows how MOF materials can be endowed with useful properties by doping MOFs with fluoride. PMID:26812223

  3. Generation of energetic electrons at second harmonic cyclotron resonance in ionospheric HF heating experiments

    NASA Astrophysics Data System (ADS)

    Kuo, S. P.; Rubinraut, M.


    The theory of electron acceleration by upper hybrid waves at second harmonic cyclotron resonance is presented. The results show that the meter-scale upper hybrid waves can incorporate the finite Larmour radius effect to make a second harmonic cyclotron resonance interaction effective. The finite Larmour radius effect provides a positive feedback to the interaction, thus the energies of the accelerated electrons increase in time exponentially, rather than linearly as in the case of fundamental cyclotron resonance. Consequently, energetic electrons (having energies larger than 10.7 eV) can be generated even at very low upper hybrid wave intensities. The threshold field for parametric excitation of meter-scale upper hybrid waves by O-mode HF heating wave is shown to be very low. The theory can be a reasonable basis for explaining the enhancement of airglow at 777.4 nm observed in recent low-heating-power experiment at HAARP.

  4. Probing protein adsorption on a nanoparticle surface using second harmonic light scattering.


    Das, A; Chakrabarti, A; Das, P K


    A new application of second harmonic light scattering to probe protein physisorption on a gold nanoparticle surface in aqueous buffer is reported. The free energies of adsorption, the number of protein molecules adsorbed on the surface and the binding affinity of a moderate size protein, alcohol dehydrogenase (ADH), and a small protein, insulin, have been determined using the change in the second harmonic scattered light signal as a function of binding. Four different size gold nanoparticles from 15 to 60 nm were used to determine the effect of size on the free energy change, the affinity constant and the number of protein molecules adsorbed on the surface. All were shown to increase with an increase in size. The binding can be reversed by centrifugation, and the protein molecules can be desorbed quantitatively. The application of this method for studying thermodynamic parameters of weakly interacting biomolecules with nanoparticles for nanoparticle based diagnostic and therapeutic formulations is important. PMID:27530608

  5. Multiple layer optical memory system using second-harmonic-generation readout


    Boyd, Gary T.; Shen, Yuen-Ron


    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 generating a pattern of radiation of the second harmonic 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 harmonic frequency generated.

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

    SciTech Connect

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


    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.

  7. Resonant second harmonic generation in a gallium nitride two-dimensional photonic crystal on silicon

    SciTech Connect

    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.


    We demonstrate second harmonic generation 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 harmonic generation is evidenced by the spectral range of the emitted signal, the quadratic power dependence vs. input power, and the spectral dependence of second harmonic signal. The harmonic emission pattern is correlated to the harmonic polarization generated 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.

  8. Nanostructure induced changes in lifetime and enhanced second-harmonic response of organic-plasmonic hybrids

    SciTech Connect

    Leißner, Till; Kostiučenko, Oksana; Rubahn, Horst-Günter; Fiutowski, Jacek; Brewer, Jonathan R.


    In this letter we show that the optical response of organic nanofibers, grown from functionalized para-quaterphenylene molecules, can be controlled by forming organic-plasmonic hybrid systems. The interaction between nanofibers and supporting regular arrays of nanostructures leads to a strongly enhanced second harmonic response. At the same time, the fluorescence lifetime of the nanofibers is reduced from 0.32 ns for unstructured gold films to 0.22 ns for gold nanosquare arrays, demonstrating efficient organic–plasmonic interaction. To study the origin of these effects, we applied two-photon laser scanning microscopy and fluorescence lifetime imaging microscopy. These findings provide an effective approach for plasmon-enhanced second-harmonic generation at the nanoscale, which is attractive for nanophotonic circuitry.

  9. Second Harmonic Suppression in S-Band Traveling Wave Tube Tapers

    NASA Astrophysics Data System (ADS)

    Gehrmann, Elke; Birtel, Philip; Dürr, Wolfgang; André, Frédéric; Jacob, Arne F.


    Traveling wave tubes (TWTs) operating at S-band are to be improved by suppressing the second harmonic frequency. Among the different possibilities, two techniques, namely harmonic injection and a filter helix for frequency selective signal suppression, are studied in more detail and applied to S-band tubes in both simulation and measurement. In addition, their suitability to improve tube performance by reducing the second harmonic is discussed. Moreover, filter helix implementation in TWTs with an arbitrary pitch profile along the interaction area is considered. In this context, the dependence of the pitch discontinuity reflection coefficient on several filter helix parameters is investigated. The influence of those parameters on the filter performance is shown by filter helix optimization. Measurement results of the optimized filter helix TWT are presented.

  10. Whispering gallery microresonators for second harmonic light generation from a low number of small molecules

    PubMed Central

    Dominguez-Juarez, J.L.; Kozyreff, G.; Martorell, Jordi


    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 harmonic light generation, because at interfaces the inversion symmetry is broken. However, such light generation 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 generate a detectable change in the second harmonic light. This generation 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

  11. Thermal Transitions of Fibrillar Collagen Unveiled by Second-Harmonic Generation Microscopy of Corneal Stroma

    PubMed Central

    Matteini, Paolo; Cicchi, Riccardo; Ratto, Fulvio; Kapsokalyvas, Dimitrios; Rossi, Francesca; de Angelis, Marella; Pavone, Francesco S.; Pini, Roberto


    The thermal transitions of fibrillar collagen are investigated with second-harmonic generation polarization anisotropy microscopy. Second-harmonic generation images and polarization anisotropy profiles of corneal stroma heated in the 35–80°C range are analyzed by means of a theoretical model that is suitable to probe principal intramolecular and interfibrillar parameters of immediate physiological interest. Our results depict the tissue modification with temperature as the interplay of three destructuration stages at different hierarchical levels of collagen assembly including its tertiary structure and interfibrillar alignment, thus supporting and extending previous findings. This method holds the promise of a quantitative inspection of fundamental biophysical and biochemical processes and may find future applications in real-time and postsurgical functional imaging of collagen-rich tissues subjected to thermal treatments. PMID:22995490

  12. A TE{sub 21} second-harmonic gyrotron backward-wave oscillator with slotted structure

    SciTech Connect

    Chen, N. C.; Yu, C. F.; Chang, T. H.


    Second-harmonic gyrotron backward-wave oscillator (gyro-BWO) with a reduced magnetic field strength is a tunable source in the millimeter wave regime, but it has long been impeded by the severe mode competition as a result of low efficiency and narrow bandwidth. This study employs a slotted structure functioning as a mode selective circuit to suppress the lower order transverse modes. In addition, a two-step tapered waveguide is adopted to stabilize the higher-order transverse modes and axial modes. Some important characteristics of the slotted gyro-BWO will be analyzed and discussed. As a calculated result, the interaction efficiency is improved and the stable tuning range is broadened. A stable, Ka-band, slotted second-harmonic gyro-BWO is capable of producing an efficiency of 23% with a 3 dB tuning bandwidth of 9% at 5 A and 100 kV.

  13. Development of a novel high power sub-THz second harmonic gyrotron.


    Notake, T; Saito, T; Tatematsu, Y; Fujii, A; Ogasawara, S; Agusu, La; Ogawa, I; Idehara, T; Manuilov, V N


    Record-breaking high power coherent radiation at a subterahertz frequency region from a gyrotron utilizing second harmonic resonance modes was attained with a simple cavity. In order to aim at high power and high frequency simultaneously, the oscillation mode was selected carefully enough to realize stable radiation free from mode competition. The cavity radius was determined from the viewpoints of the oscillation frequency, the coupling coefficient between the electron beam, and the rf-electric field. The cavity length was also optimized for the highest perpendicular efficiency. In addition, a new electron gun which is capable of generating a thin laminar beam for a large current was introduced. Consequently, single mode second harmonic radiation with powers of 52 and 37 kW at frequencies of about 349 and 390 GHz, respectively, was achieved. PMID:20366101

  14. Development of a Novel High Power Sub-THz Second Harmonic Gyrotron

    SciTech Connect

    Notake, T.; Saito, T.; Tatematsu, Y.; Fujii, A.; Ogasawara, S.; Agusu, La; Ogawa, I.; Idehara, T.; Manuilov, V. N.


    Record-breaking high power coherent radiation at a subterahertz frequency region from a gyrotron utilizing second harmonic resonance modes was attained with a simple cavity. In order to aim at high power and high frequency simultaneously, the oscillation mode was selected carefully enough to realize stable radiation free from mode competition. The cavity radius was determined from the viewpoints of the oscillation frequency, the coupling coefficient between the electron beam, and the rf-electric field. The cavity length was also optimized for the highest perpendicular efficiency. In addition, a new electron gun which is capable of generating a thin laminar beam for a large current was introduced. Consequently, single mode second harmonic radiation with powers of 52 and 37 kW at frequencies of about 349 and 390 GHz, respectively, was achieved.

  15. Detection of collagen by second harmonic microscopy as a diagnostic tool for liver fibrosis

    NASA Astrophysics Data System (ADS)

    Banavar, Maruth; Kable, Eleanor P. W.; Braet, Filip; Wang, X. M.; Gorrell, M. D.; Cox, Guy


    Liver fibrosis has many causes, including hepatitis C, alcohol abuse, and non-alcoholic steatohepatitis. It is characterized by abnormal deposition of extracellular matrix proteins, mainly collagen. The deposition of these proteins results in impaired liver function caused by distortion of the hepatic architecture by fibrous scar tissue. The unique triple helix structure of collagen and high level of crystallinity make it very efficient for generating second harmonic signals. In this study we have set out to see if second harmonic imaging of collagen can be used as a non-biased quantitative tool for classification of fibrosis levels in liver biopsies and if it can detect early fibrosis formation not detected by current methods.

  16. Stokes vector based polarization resolved second harmonic microscopy of starch granules.


    Mazumder, Nirmal; Qiu, Jianjun; Foreman, Matthew R; Romero, Carlos Macías; Török, Peter; Kao, Fu-Jen


    We report on the measurement and analysis of the polarization state of second harmonic signals generated by starch granules, using a four-channel photon counting based Stokes-polarimeter. Various polarization parameters, such as the degree of polarization (DOP), the degree of linear polarization (DOLP), the degree of circular polarization (DOCP), and anisotropy are extracted from the 2D second harmonic Stokes images of starch granules. The concentric shell structure of a starch granule forms a natural photonic crystal structure. By integration over all the solid angle, it will allow very similar SHG quantum efficiency regardless of the angle or the states of incident polarization. Given type I phase matching and the concentric shell structure of a starch granule, one can easily infer the polarization states of the input beam from the resulting SH micrograph. PMID:23577289

  17. Vectorial approach to studying second harmonic generation in collagen using linearly and radially polarized beams

    NASA Astrophysics Data System (ADS)

    Yew, Elijah Y. S.; Sheppard, Colin J. R.


    The study of second harmonic generation (SHG) has been examined using a vectorial approach for both linearly and radially polarized beams. This approach is necessary for situations when the beam is tightly focused such as in a microscope. Using the vectorial approach, the result of including the y and z components of the electric field is that previously ignored 'cross-component' terms are now found to have an influence on the SHG polarization and the radiation patterns obtained. Since SHG is dependent on the susceptibility tensor, the inclusion of these 'cross-component' terms can help to identify structural changes in biological materials simply by studying the changes in the tensor via the SHG polarization. In particular, we calculate the second harmonic polarization induced in collagen for both linearly and radially polarized beams.

  18. Stokes vector based polarization resolved second harmonic microscopy of starch granules

    PubMed Central

    Mazumder, Nirmal; Qiu, Jianjun; Foreman, Matthew R.; Romero, Carlos Macías; Török, Peter; Kao, Fu-Jen


    We report on the measurement and analysis of the polarization state of second harmonic signals generated by starch granules, using a four-channel photon counting based Stokes-polarimeter. Various polarization parameters, such as the degree of polarization (DOP), the degree of linear polarization (DOLP), the degree of circular polarization (DOCP), and anisotropy are extracted from the 2D second harmonic Stokes images of starch granules. The concentric shell structure of a starch granule forms a natural photonic crystal structure. By integration over all the solid angle, it will allow very similar SHG quantum efficiency regardless of the angle or the states of incident polarization. Given type I phase matching and the concentric shell structure of a starch granule, one can easily infer the polarization states of the input beam from the resulting SH micrograph. PMID:23577289

  19. Numerical study on a 0.4 THz second harmonic gyrotron with high power

    SciTech Connect

    Chaojun, Lei; Sheng, Yu; Hongfu, Li; Yinghui, Liu; Xinjian, Niu; Qixiang, Zhao


    Terahertz and sub-terahertz science and technology are promising topics today. However, it is difficult to obtain high power source of terahertz wave. In this paper, the mode competition and beam-wave interaction in a gradually tapered cavity are studied to achieve high efficiency of a 0.4THz second harmonic gyrotron in practice. In order to attain high power and stable radiation, the TE{sub 32,5} mode is selected as the operating mode of the desired gyrotron to realize single mode oscillation. The issues of studying on the high-order mode gyrotrons are solved effectively by transforming the generalized telegraphist's equations. The efficiency and output power of the gyrotron under different conditions have been calculated by the code, which is based on the transformed equations. Consequently, the results show that single mode second harmonic radiation with power of over 150 kW at frequency of 0.4 THz could be achieved.

  20. Second-harmonic generation efficiency for multifrequency ytterbium-doped fibre laser radiation

    SciTech Connect

    Politko, M O; Kablukov, S I; Nemov, I N; Babin, Sergei A


    The second-harmonic generation (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 harmonic 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)

  1. Second-harmonic generation in shear wave beams with different polarizations

    SciTech Connect

    Spratt, Kyle S. Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hamilton, Mark F.


    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-harmonic generation 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-harmonic generation 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 harmonic generated 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-harmonic generation from a Gaussian source condition that gives explicitly the relationship between the polarization of the source-frequency beam and the polarization of the second harmonic.

  2. Note: auto-relock system for a bow-tie cavity for second harmonic generation.


    Haze, Shinsuke; Hata, Sousuke; Fujinaga, Munekazu; Mukaiyama, Takashi


    This Note reports on the implementation of an automatic relocking system for a bow-tie cavity for second harmonic generation to produce an ultra-violet laser source. The system is based on a sample-and-hold technique for controlling the cavity length using simple servo electronics. Long-term stabilization of the cavity output power is successfully achieved, which makes this system suitable for designing stable atomic physics experiments. PMID:23464273

  3. Note: Auto-relock system for a bow-tie cavity for second harmonic generation

    NASA Astrophysics Data System (ADS)

    Haze, Shinsuke; Hata, Sousuke; Fujinaga, Munekazu; Mukaiyama, Takashi


    This Note reports on the implementation of an automatic relocking system for a bow-tie cavity for second harmonic generation to produce an ultra-violet laser source. The system is based on a sample-and-hold technique for controlling the cavity length using simple servo electronics. Long-term stabilization of the cavity output power is successfully achieved, which makes this system suitable for designing stable atomic physics experiments.

  4. Probing Ferroelectric Domain Engineering in BiFeO3 Thin Films by Second Harmonic Generation.


    Trassin, Morgan; Luca, Gabriele De; Manz, Sebastian; Fiebig, Manfred


    An optical probe of the ferroelectric domain distribution and manipulation in BiFeO3 thin films is reported using optical second harmonic generation. 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. PMID:26175000

  5. Second harmonic generation imaging of dermal collagen component in human keloid tissue

    NASA Astrophysics Data System (ADS)

    Yu, H. B.; Chen, S.; Zhu, X. Q.; Yang, H. Q.; Chen, J. X.


    In this paper, we report second harmonic generation (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.

  6. Second Harmonic Detection of Spin-Dependent Transport in Magnetic Nanostructures

    NASA Astrophysics Data System (ADS)

    Yu, Hai-Ming; Granville, S.; Yu, Da-Peng; J-ph., Ansermet


    Detection of the second harmonic response of magnetic nanostructures to an ac current is shown to be a very sensitive probe of the magnetization reversal process. A temperature oscillation is obtained by Joule heating instead of using a laser as the heat source, as in thermo-galvanic voltage measurements (TGV). Joule heating is used to produce a large local temperature gradient in asymmetric Co/Cu/Co spin valves. Evidence is found for an effect of a heat current on magnetization.

  7. Optical chirality of bacteriorhodopsin films via second harmonic Maker's fringes measurements

    NASA Astrophysics Data System (ADS)

    Larciprete, M. C.; Belardini, A.; Sibilia, C.; Saab, M.-b.; Váró, G.; Gergely, C.


    We experimentally investigated second harmonic generation from an oriented multilayer film of bacteriorhodopsin protein, deposited onto a charged surface. The generated signal is obtained as a function of incidence angle, at different polarization state of both fundamental and generated beams. We show that the measurements, together with the analytical curves, allow to retrieve the nonvanishing elements of the nonlinear optical tensor, including the ones introduced by optical chirality.

  8. Theory of second-harmonic generation of molecular systems: The steady-state case

    SciTech Connect

    Lin, S.H.; Alden, R.G. ); Villaeys, A.A.; Pflumio, V. )


    In this paper, a general formalism for treating both steady-state and time-resolved second-harmonic generation 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.

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


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


    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

  10. Generation of high power sub-terahertz radiation from a gyrotron with second harmonic oscillation

    SciTech Connect

    Saito, Teruo; Yamada, Naoki; Ikeuti, Shinji; Tatematsu, Yoshinori; Ikeda, Ryosuke; Ogawa, Isamu; Idehara, Toshitaka; Ogasawara, Shinya; Manuilov, Vladimir N.; Shimozuma, Takashi; Kubo, Shin; Nishiura, Masaki; Tanaka, Kenji; Kawahata, Kazuo


    New power records of second harmonic gyrotron oscillation have been demonstrated in the sub-THz band. The first step gyrotron of demountable type had succeeded in oscillation with power more than 50 kW at 350 GHz and nearly 40 kW at 390 GHz [T. Notake et al., Phys. Rev. Lett. 103, 225002 (2009)]. Then, the second step gyrotron of sealed-off type was manufactured. A cavity mode was carefully selected to avoid mode competition with a neighboring fundamental harmonic mode. Matching of the selected mode with the electron gun was also circumspectly considered. The second step gyrotron has attained higher power radiation than the first gyrotron. The maximum single mode power was 62 kW at 388 GHz. Then, the electron gun was modified for use of a different cavity mode with a higher coupling coefficient than that for the 62 kW mode. The new mode proved single mode oscillation power of 83 kW at about 389 GHz. These results are new second-harmonic-oscillation power records for sub-THz gyrotrons. The present study constitutes foundations of development of high power second harmonic sub-THz gyrotron for application to collective Thomson scattering measurement on fusion plasmas, especially on high-density plasmas such as those produced in LHD [N. Ohyabu et al., Phys. Rev. Lett. 97, 055002 (2006)]. This paper reports the design consideration to realize high power single mode gyrotron oscillation at second harmonic and the examination of oscillation characteristics of the gyrotron.

  11. Whispering-gallery-mode analysis of phase-matched doubly resonant second-harmonic generation

    NASA Astrophysics Data System (ADS)

    Dumeige, Yannick; Féron, Patrice


    We propose a coupled modes analysis of second-harmonic generation in microdisk resonators. We demonstrate that whispering gallery modes can be used to obtain a combination of modal and geometrical quasi-phase-matching (without domain inversion) to obtain efficient conversion in isotropic and nonferroelectric materials such as III-V semiconductor compounds. Finally we use an analytical model to describe the coupling between a bus waveguide and the nonlinear microdisk to achieve an optimization scheme for practical configuration.

  12. Bistable sensors based on broken symmetry phenomena: The residence time difference vs. the second harmonic method

    NASA Astrophysics Data System (ADS)

    Nikitin, A.; Stocks, N. G.; Bulsara, A. R.


    A periodically driven noisy bistable system can be used as a sensor of a dc target signal. In the presence of the dc signal the symmetry of the potential energy function that underpins the sensor dynamics can be broken, leading to even harmonics of the driving frequency in the power spectrum. Both the power of the second harmonic and the mean residence time difference can be used for an estimation of the dc signal. In this paper we introduce a method for the power spectrum estimation from the experimental time series. This method can be considered to be an alternative to methods based on the Fourier transform. The presented method is faster for computation than the Fast Fourier Transform, and it allow us to estimate the power contained in peaks (or features) without their mixture with the power spectrum background. Using this method we compute the power of the second harmonic in the response power spectrum and compare the accuracy of the second harmonic method and the mean residence time difference (RTD) via the Shannon mutual information. We find that the RTD, generally, yields better performance in bistable noisy sensors.

  13. Optical recording of action potentials with second-harmonic generation microscopy.


    Dombeck, Daniel A; Blanchard-Desce, Mireille; Webb, Watt W


    Nonlinear microscopy has proven to be essential for neuroscience investigations of thick tissue preparations. However, the optical recording of fast (approximately 1 msec) cellular electrical activity has never until now been successfully combined with this imaging modality. Through the use of second-harmonic generation microscopy of primary Aplysia neurons in culture labeled with 4-[4-(dihexylamino)phenyl][ethynyl]-1-(4-sulfobutyl)pyridinium (inner salt), we optically recorded action potentials with 0.833 msec temporal and 0.6 microm spatial resolution on soma and neurite membranes. Second-harmonic generation response as a function of change in membrane potential was found to be linear with a signal change of approximately 6%/100 mV. The signal-to-noise ratio was approximately 1 for single-trace action potential recordings but was readily increased to approximately 6-7 with temporal averaging of approximately 50 scans. Photodamage was determined to be negligible by observing action potential characteristics, cellular resting potential, and gross cellular morphology during and after laser illumination. High-resolution (micrometer scale) optical recording of membrane potential activity by previous techniques has been limited to imaging depths an order of magnitude less than nonlinear methods. Because second-harmonic generation is capable of imaging up to approximately 400 microm deep into intact tissue with submicron resolution and little out-of-focus photodamage or bleaching, its ability to record fast electrical activity should prove valuable to future electrophysiology studies. PMID:14749445

  14. Background-free electric field-induced second harmonic generation with interdigitated combs of electrodes.


    Jašinskas, Vidmantas; Gedvilas, Mindaugas; Račiukaitis, Gediminas; Gulbinas, Vidmantas


    The electric field-induced second harmonic (EFISH) generation 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 generation of the second harmonics (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 generation 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 harmonics. 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

  15. Characterization of the cytotoxicity and imaging properties of second-harmonic nanoparticles

    NASA Astrophysics Data System (ADS)

    Hsieh, Chia-Lung; Grange, Rachel; Pu, Ye; Psaltis, Demetri


    We develop second-harmonic nanoparticles as the contrast agents for cell imaging. Second-harmonic nanoparticles show promise as cell imaging probes due to their non-bleaching, non-blinking, and coherent signal. Nanoparticles of noncentrosymmetric crystal structures have high second-harmonic generation (SHG) efficiency and provide high contrast in a generally non-structured cell environment. Here, we use barium titanate (BaTiO3) nanoparticles with tetragonal crystal structure as imaging probes. Cytotoxicity tests performed on BaTiO3 nanoparticles with mammalian cells did not result in toxic effects. Specifically, we observed no change in the cell metabolism after 24 hours incubation of the cells with high concentration of BaTiO3 nanoparticles. We demonstrate two methods of cell labeling with BaTiO3 nanoparticles for imaging. One is non-specific labeling via endocytosis of the cells, which results in a great number of the nanoparticles randomly distributed inside the cells. The other is specific labeling via surface functionalization of the nanoparticles with antibodies, which enables us to label specific cell membrane proteins with the nanoparticles. SHG imaging is compatible to two-photon microscopy and the SHG signal from nanoparticles can be easily detected with a standard two-photon confocal microscope. Our work provides the opportunity for long-term, three-dimensional cell tracking with secondharmonic nanoparticles.

  16. Size dependence of second-harmonic generation at the surface of microspheres

    SciTech Connect

    Viarbitskaya, Sviatlana; Meulen, Peter van der; Hansson, Tony; Kapshai, Valery


    The resonance-enhanced surface second-harmonic generation (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-harmonic-enhancing dyes--malachite green and pyridine 1. The two dyes gave the same strongly modulated pattern of the forward second-harmonic 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.

  17. Second-harmonic generation in periodically poled bulk Rb-doped KTiOPO₄ below 400 nm at high peak-intensities.


    Zukauskas, Andrius; Pasiskevicius, Valdas; Canalias, Carlota


    We demonstrate that bulk Rb-doped KTiOPO₄ (RKTP) shows improved susceptibility to gray-tracking compared to flux-grown KTiOPO₄ . We show high-fidelity periodic poling of 1 mm thick RKTP with a period of 3.18 µm for second harmonic generation at 398 nm with a normalized conversion efficiency of 1.79%/Wcm. The crystal is used to frequency-double 138 fs-long pulses with an efficiency of 20% and a peak intensity of 560 MW/cm² without visible gray-tracking signs. We demonstrate that two-photon absorption is the predominant mechanism limiting the SHG efficiency in this spectral range at high peak powers and high repetition rates. PMID:23389121

  18. Applications of parametric processes to high-quality multicolour ultrashort pulses, pulse cleaning and CEP stable sub-3fs pulse

    NASA Astrophysics Data System (ADS)

    Kobayashi, Takayoshi; Liu, Jun; Okamura, Kotaro


    Our recent experimental results of three methods related to and useful for the generation of attosecond pulses are summarized. The pulses obtained by all of them have high qualities in terms of phase, temporal, spectral and spatial properties which are based on the physical principles associated with the parametric processes. First, carrier-envelope phase (CEP) stable sub-5 fs and sub-3 fs pulses by non-collinear optical parametric amplification (NOPA) in the near-infrared and visible spectral range will be described. The mechanism of the passive CEP stabilization is described. Passively stabilized idler and its second harmonic (SH) pulses from NOPAs are compressed to sub-5fs and sub-3fs, respectively. Compression of the idler output from a NOPA and its SH is attained with a specially designed characterization method during the compression. Second, generation of multicolour pulses by the cascaded four-wave mixing process in bulk media is discussed. As short as 15-fs multicoloured femtosecond pulses are obtained with two ˜40 fs pulses incident to a fused-silica glass plate by this method. These broadband multicolour sidebands are expected to provide single-cycle or sub-fs pulses after the Fourier synthesis. Third, a new technique based on self-diffraction in the Kerr medium is used to clean and shorten the femtosecond laser pulse. The cleaned pulse with high temporal contrast is expected to be used as a seed for a background-free petawatt laser system and then used as the laser source for high-energy attosecond pulse generation in a solid target. The mechanisms of CEP stabilization, pulse spectral smoothening and pulse contrast enhancement are comparatively discussed.

  19. Lossless backward second-harmonic generation of extremely narrow subdiffractive beams in two-dimensional photonic crystals

    SciTech Connect

    Nistor, C.; Cojocaru, C.; Trull, J.; Karle, T. J.; Raj, R.; Raineri, F.; Staliunas, K.


    We report efficient second harmonic generation using extremely narrow beams (with diameter of the order of the wavelength) that propagate in the self-collimation (or nondiffractive) regime in a two-dimensional photonic crystal. We design and numerically test an AlGaAs photonic crystal membrane, where both fundamental and generated second harmonic beams propagate without diffraction and without out-of-plane losses. The characteristics of the generated second harmonic that is mainly propagating in the backward direction and the conversion efficiency of the proposed scheme are obtained by nonlinear finite-difference time-domain numerical simulations.

  20. Relation between efficiency of second harmonic generation and spectral properties of a one-dimensional photonic crystal

    NASA Astrophysics Data System (ADS)

    Zaporozhchenko, R. G.


    Numerical calculation of second harmonic generation in a photonic crystal consisting of alternating quarter-wave layers of ZnS and SeF2 pumped by a femtosecond tunable laser is carried out. The results are compared with the spectral characteristics of the photonic crystal obtained with the use of a matrix method for calculating transmission coefficients. It is shown that the maximum efficiency of conversion to the second harmonic takes place at a minimum group velocity mismatch of the pump and second harmonic waves, corresponding to pump frequencies in the range below the band gap edge of the photonic crystal.

  1. Three-dimensional electric field visualization utilizing electric-field-induced second-harmonic generation in nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Chen, I.-Hsiu; Chu, Shi-Wei; Bresson, Francois; Tien, Ming-Chun; Shi, Jin-Wei; Sun, Chi-Kuang


    An electric-field-induced second-harmonic-generation signal in a nematic liquid crystal is used to map the electric field in an integrated-circuit-like sample. Since the electric-field-induced second-harmonic-generation signal intensity exhibits a strong dependence on the polarization of the incident laser beam, both the amplitude and the orientation of the electric field vectors can be measured. Combined with scanning second-harmonic-generation microscopy, three-dimensional electric field distribution can be easily visualized with high spatial resolution of the order of 1 μm.

  2. Growth direction of oblique angle electron beam deposited silicon monoxide thin films identified by optical second-harmonic generation

    SciTech Connect

    Vejling Andersen, Søren; Lund Trolle, Mads; Pedersen, Kjeld


    Oblique angle deposited (OAD) silicon monoxide (SiO) thin films forming tilted columnar structures have been characterized by second-harmonic generation. It was found that OAD SiO leads to a rotationally anisotropic second-harmonic response, depending on the optical angle of incidence. A model for the observed dependence of the second-harmonic signal on optical angle of incidence allows extraction of the growth direction of OAD films. The optically determined growth directions show convincing agreement with cross-sectional scanning electron microscopy images. In addition to a powerful characterization tool, these results demonstrate the possibilities for designing nonlinear optical devices through SiO OAD.

  3. Continuous-wave, single-pass, single-frequency second-harmonic-generation at 266 nm based on birefringent-multicrystal scheme.


    Devi, Kavita; Parsa, S; Ebrahim-Zadeh, M


    We report the implementation of a compact cascaded multicrystal scheme based on birefringent crystals in critical phase-matching, for the generation of continuous-wave (cw) radiation in the deep ultraviolet (UV). The approach comprises a cascade of 4 single-pass second-harmonic-generation (SHG) stages in β-BaB2O4 (BBO) pumped by a single-frequency cw green source at 532 nm. A deep-UV cw output power of 37.7 mW at 266 nm has been obtained with a high passive power stability of 0.12% rms over more than 4 hours. Characterization and optimization of the system in each stage has been systematically performed. Angular phase-matching acceptance bandwidth under tight focusing in BBO, and spectral properties of the deep-UV radiation, have been studied. Theoretical calculations for SHG in the cascaded scheme based on birefringent phase-matching have been performed, and enhancement in UV power compared to single-stage single-pass scheme are studied. Theoretical comparison of BBO with other potential crystals for deep-UV generation in cascaded multicrystal scheme is also presented. PMID:27137310

  4. Multi-line transmission in medical imaging using the second-harmonic signal.


    Prieur, Fabrice; Dénarié, Bastien; Austeng, Andreas; Torp, Hans


    The emergence of three-dimensional imaging in the field of medical ultrasound imaging has greatly increased the number of transmissions needed to insonify a whole volume. With a large number of transmissions comes a low image frame rate. When using classical transmission techniques, as in two-dimensional imaging, the frame rate becomes unacceptably low, prompting the use of alternative transmission patterns that require less time. One alternative is to use a multi-line transmission (MLT) technique which consists of transmitting several pulses simultaneously in different directions. Perturbations appear when acquiring and beamforming the signal in the direction of one pulse because of the pulses sent in other directions. The edge waves from the pulses transmitted in a different direction add to the signal transmitted in the direction of interest, resulting in artifacts in the final image. Taking advantage of the nonlinear propagation of sound in tissue, the second-harmonic signal can be used with the MLT technique. The image obtained using the second-harmonic signal, compared with an image obtained using the fundamental signal, should have reduced artifacts coming from other pulses transmitted simultaneously. Simulations, backed up by experiments imaging a wire target and an in vivo left ventricle, confirm that the hypothesis is valid. In the studied case, the perturbations appear as an increase in the signal level around the main echo of a point scatterer. When using the fundamental signal, the measured amplitude level of the perturbations was approximately -40 dB compared with the maximum signal amplitude (-27 dB in vivo), whereas it was around -60 dB (-45 dB in vivo) for the second-harmonic signal. The MLT technique encounters limitations in the very near field where the pulses overlap and the perturbation level also increases for images with strong speckle and low contrast. PMID:24297034

  5. Design of a 50 MW, 34 GHz second harmonic coaxial gyroklystron for advanced accelerators

    SciTech Connect

    Arjona, M.R.; Lawson, W.


    At the University of Maryland, the authors have been investigating the feasibility of using gyroklystrons and gyroklystrons as drivers for linear colliders and advanced accelerators for a number of years. The most recent experimental tube achieved a peak power of about 80 MW at 8.57 GHz with 32% efficiency and over 30 dB gain with a three-cavity first harmonic circuit. The current experimental effort is devoted to producing about 100 MW of peak power at 17.14 GHz with a second-harmonic three-cavity tube. Some schemes for advanced linear colliders with center-of-mass energies of 5 TeV or more expect to require higher frequency sources, perhaps near 35 GHz or 91 GHz. A design study at 95 GHz indicated that peak powers near 7 MW were possible. In this design study, they present the simulated operating characteristics of a four cavity 34 GHz second-harmonic gyroklystron tube which is capable of producing about 60 MW of peak power with an efficiency of about 40% and a gain above 50 dB. The electron gun is a single-anode magnetron injection gun. The input cavity is a TE{sub 011} cavity which is driven at 17 GHz. The remainder of the cavities are TE{sub 021} cavities which interact near the second harmonic of the cyclotron frequency. The gain cavity and the output cavities are at twice the drive frequency, but the penultimate cavity is detuned to enhance efficiency. All cavities are abrupt-transition cavities. Both systems are derived from scaled versions of the 17 GHz tube. In this paper, they present detailed designs and performance predictions for both the electron gun and the microwave circuit.

  6. Calculation of optical second-harmonic susceptibilities and optical activity for crystals

    SciTech Connect

    Levine, Z.H.


    A new generation of nearly first-principles calculations predicts both the linear and second-harmonic susceptibilities for a variety of insulating crystals, including GaAs, GaP, AlAs, AlP, Se, {alpha}-quartz, and c-urea. The results are typically in agreement with experimental measurements. The calculations have been extended to optical activity, with somewhat less success to date. The theory, based on a simple self-energy correction to the local density approximation, and results are reviewed herein.

  7. Simultaneous stimulated Raman scattering and second harmonic generation in periodically poled lithium niobate

    NASA Astrophysics Data System (ADS)

    McConnell, Gail; Ferguson, Allister I.


    Simultaneous stimulated Raman scattering (SRS) and second harmonic generation (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.

  8. Enhancing second harmonic generation in gold nanoring resonators filled with lithium niobate.


    Lehr, Dennis; Reinhold, Jörg; Thiele, Illia; Hartung, Holger; Dietrich, Kay; Menzel, Christoph; Pertsch, Thomas; Kley, Ernst-B; Tünnermann, Andreas


    Plasmonic nanorings provide the unique advantage of a pronounced plasmonic field enhancement inside their core. If filled with a polarizable medium, it may significantly enhance its optical effects. Here, we demonstrate this proposition by filling gold nanorings with lithium niobate. The generated second harmonic signal is compared to the signal originating from an unpatterned lithium niobate surface. Measurements and simulation confirm an enhancement of about 20. Applications requiring nanoscopic localized light sources like fluorescence spectroscopy or quantum communication will benefit from our findings. PMID:25584636

  9. Impact of longitudinal fields on second harmonic generation in lithium niobate nanopillars

    NASA Astrophysics Data System (ADS)

    Baghban, Mohammad Amin; Gallo, Katia


    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 harmonic generation 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.

  10. Study of the second harmonic generation and optical rectification in a cBN crystal

    SciTech Connect

    Dou Qingping; Ma Haitao; Jia Gang; Chen Zhanguo; Cao Kun; Zhang Tiechen


    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 harmonic generation (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)