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Sample records for fs cascaded second-harmonic

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

    SciTech Connect

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

    2010-12-15

    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 ({beta}-barium borate) is found for pump wavelengths in the range {lambda}=0.95-1.45 {mu}m, and is located in the regime {lambda}=1.5-3.5 {mu}m. 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. 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.

    2014-02-07

    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.

  3. Enhanced coherent control of carrier and spin density in a zinc-blende semiconductor by cascaded second-harmonic generation

    NASA Astrophysics Data System (ADS)

    Stevens, Martin J.; Bhat, R. D. R.; Pan, X. Y.; van Driel, H. M.; Sipe, J. E.; Smirl, Arthur L.

    2005-05-01

    Phase- and polarization-dependent optical processes involving pulses with frequencies ω and 2ω can be used to independently control electron and spin density in zinc-blende semiconductors such as GaAs. One such process is quantum interference control (QUIC) where interference between transition amplitudes associated with one- and two-photon absorption alters the carrier/spin generation rate. A second process, which has been acknowledged but not utilized, is cascaded second-harmonic (CASH) generation in which phase-dependent upconversion/downconversion between the two pulses modulates the 2ω pulse intensity and/or polarization and hence modulates the carrier or spin generation rate by single-photon absorption at 2ω. Here we report the use of (110)-oriented GaAs /AlGaAs quantum wells with a 500-nmAlGaAs buffer layer to enhance CASH and to allow independent control of spin and carrier densities. Experiments conducted with 100-fs pulses at 775 and 1550nm or at 715 and 1430nm, with different polarization states and with different sample orientations, show how QUIC and CASH processes vary with excitation frequency and demonstrate the dominant role played by CASH. We point the way to achieving nearly 100% control through CASH.

  4. Non-degenerate fs pump-probe study on InGaN with multi-wavelength second-harmonic generation.

    PubMed

    Wang, Hsiang-Chen; Lu, Yen-Cheng; Chen, Cheng-Yen; Chi, Chun-Yung; Chin, Shu-Cheng; Yang, C C

    2005-07-11

    Non-degenerate fs pump-probe experiments in the UV-visible range for ultrafast carrier dynamics study of InGaN with adjustable pump and probe photon energies are implemented with simultaneously multiwavelength second-harmonic generation (SHG) of a 10 fs Ti:sapphire laser. The multi-wavelength SHG is realized with two beta-barium borate crystals of different cutting angles. The full-widths at half-maximum of the SHG pulses are around 150 fs, which are obtained from the cross-correlation measurement with a reverse-biased 280-nm light-emitting diode as the twophoton absorption photo-detector. Such pulses are used to perform nondegenerate pump-probe experiments on an InGaN thin film, in which indium-rich nano-clusters and compositional fluctuations have been identified. Relaxation of carriers from the pump level to the probe one through the scattering-induced local thermalization (<1 ps) and then the carrier-transport-dominating global thermalization (in several ps) processes is observed.

  5. Strong Enhancement of Second Harmonic Emission by Plasmonic Resonances at the Second Harmonic Wavelength.

    PubMed

    Metzger, Bernd; Gui, Lili; Fuchs, Jaco; Floess, Dominik; Hentschel, Mario; Giessen, Harald

    2015-06-10

    We perform second harmonic spectroscopy of aluminum nanoantenna arrays that exhibit plasmonic resonances at the second harmonic wavelength between 450 and 570 nm by focusing sub-30 fs laser pulses tunable from 900 to 1140 nm onto the nanoantenna arrays. We find that a plasmonic resonance at the second harmonic wavelength boosts the overall nonlinear process by more than an order of magnitude. In particular, in the measurement the resonant second harmonic polarization component is a factor of about 70 stronger when compared to the perpendicular off-resonant second harmonic polarization. Furthermore, the maximum of the second harmonic conversion efficiency is found to be slightly blue-shifted with respect to the peak of the linear optical far-field spectrum. This fact can be understood from a simple model that accounts for the almost off-resonant absorption at the fundamental wavelength and the resonant emission process at the second harmonic.

  6. In vivo visualization of collagen fiber produced by cultured osteoblasts using sensitive second-harmonic-generation microscopy equipped with a 10-fs mode-locked Ti:sapphire laser

    NASA Astrophysics Data System (ADS)

    Hase, Eiji; Sato, Katsuya; Yasui, Takeshi

    2015-03-01

    Second-harmonic-generation (SHG) microscopy is a new tool for observing the collagen fiber in tissue in vivo. Conventional SHG microscopy equipped with 100-fs pulse laser is insufficient to visualize low-order-structured, immature collagen with high contrast (for example, collagen fiber produced by cultured cell) because of low nonlinear susceptibility χ(2). To enhance the image contrast while avoiding the sample damage, one should increase a peak power of the laser light while maintaining the same average power as the 100-fs laser. In this paper, we constructed sensitive SHG microscopy equipped with a 10-fs Ti:Sapphire laser and succeeded to visualize collagen fibers produced by the cultured osteoblasts in vivo.

  7. Ultrafast adiabatic second harmonic generation

    NASA Astrophysics Data System (ADS)

    Dahan, Asaf; Levanon, Assaf; Katz, Mordechai; Suchowski, Haim

    2017-03-01

    We introduce a generalization of the adiabatic frequency conversion method for an efficient conversion of ultrashort pulses in the full nonlinear regime. Our analysis takes into account dispersion as well as two-photon processes and Kerr effect, allowing complete analysis of any three waves with arbitrary phase mismatched design and any nonlinear optical process. We use this analysis to design an efficient and robust second harmonic generation, the most widely used nonlinear process for both fundamental and applied research. We experimentally show that such design not only allows for very efficient conversion of various of ultrashort pulses, but is also very robust to variations in the parameters of both the nonlinear crystal and the incoming light. These include variation of more than 100 °C in the crystal temperature, a wide bandwidth of up to 75 nm and a chirp variation of 300 fs to 3.5 ps of the incoming pulse. Also, we show the dependency of the adiabatic second harmonic generation design on the pump intensity and the crystal length. Our study shows that two photon absorption plays a critical role in such high influence nonlinear dynamics, and that it must be considered in order to achieve agreement with experimental results.

  8. Ultrafast adiabatic second harmonic generation.

    PubMed

    Dahan, Asaf; Levanon, Assaf; Katz, Mordechai; Suchowski, Haim

    2017-03-01

    We introduce a generalization of the adiabatic frequency conversion method for an efficient conversion of ultrashort pulses in the full nonlinear regime. Our analysis takes into account dispersion as well as two-photon processes and Kerr effect, allowing complete analysis of any three waves with arbitrary phase mismatched design and any nonlinear optical process. We use this analysis to design an efficient and robust second harmonic generation, the most widely used nonlinear process for both fundamental and applied research. We experimentally show that such design not only allows for very efficient conversion of various of ultrashort pulses, but is also very robust to variations in the parameters of both the nonlinear crystal and the incoming light. These include variation of more than 100 °C in the crystal temperature, a wide bandwidth of up to 75 nm and a chirp variation of 300 fs to 3.5 ps of the incoming pulse. Also, we show the dependency of the adiabatic second harmonic generation design on the pump intensity and the crystal length. Our study shows that two photon absorption plays a critical role in such high influence nonlinear dynamics, and that it must be considered in order to achieve agreement with experimental results.

  9. Second Harmonic Breakdown in KSTAR

    SciTech Connect

    Bae, Y. S.; England, A. C.; Kwon, M.; Lee, G. S.

    2007-09-28

    An 84-GHz electron cyclotron heating (ECH) system is being installed on the KSTAR tokamak. KSTAR adopts ECH-assisted start-up for the flexibility and reliability of the KSTAR operation with the plasma breakdown voltage reduced. The available maximum power of the 84 GHz ECH system is presently 500 kW with maximum duration of 2 s. Currently, the second harmonic ECH-assisted start-up is under consideration because a low toroidal field of B{sub T}{approx}1.5 T is desirable for safety and also for the high-beta experiments in the initial operation phase. The studies in this paper are on the effectiveness of the second harmonic breakdown using a 0-D time dependent plasma evolution code and the comparison with the recent DIII-D experimental results on the second harmonic pre-ionization.

  10. Second-harmonic optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Jiang, Yi; Tomov, Ivan; Wang, Yimin; Chen, Zhongping

    2004-05-01

    Second-harmonic optical coherence tomography, which uses coherence gating of second-order nonlinear optical responses of biological tissues for imaging, is described and demonstrated. Femtosecond laser pulses were used to excite second-harmonic waves from collagen harvested from rat tail tendon and a reference nonlinear crystal. Second-harmonic interference fringe signals were detected and used for image construction. Because of the strong dependence of second-harmonic generation on molecular and tissue structures, this technique imparts contrast and resolution enhancement to conventional optical coherence tomography.

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

    SciTech Connect

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

    2002-01-10

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

  12. Imaging collagen orientation using polarization-modulated second harmonic generation

    NASA Astrophysics Data System (ADS)

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

    2002-06-01

    We use polarization-modulated second harmonic generation to image fiber orientation in collagen tissues, with an axial resolution of about 10 micrometers and a transverse resolution of up to 1 micrometers . 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. Second harmonic generation in collagen

    NASA Astrophysics Data System (ADS)

    Reiser, Karen M.; Stoller, Patrick; Celliers, Peter; Rubenchik, Alexander; Bratton, Clay; Yankelevich, Diego

    2003-11-01

    Collagen possesses a strong second order nonlinear susceptibility; when it is irradiated with intense laser light, some of the reflected and transmitted light will have twice the frequency of the incident beam, a phenomenon known as second harmonic generation (SHG). Polarization modulation of an ultra-short pulse laser beam can be used to simultaneously measure collagen fiber orientation, SHG intensity, and a parameter related to the second order non-linear susceptibility. This technique has made it possible to discriminate among patterns of fibrillar orientation in many tissues. In the present study the role that organizational complexity plays in the relationship between nonlinear optical properties and collagen structure is investigated. As a component of tissues and organs, collagen"s structure and function is inextricably intertwined with that of the many other matrix components; to what extent do these noncollagenous components affect its nonlinear properties? To answer this, we investigated SHG in two different collagenous tissues, liver and cartilage; in addition we looked at the effect of progressive pathological changes in these tissues on SHG. At the other end of the spectrum, we studied collagen organized at the minimal level of complexity necessary for SHG detection: fibrils generated from solutions containing only a single type of collagen. Data obtained from these studies suggest that collagen"s strong nonlinear susceptibility, a property no other biologically significant macromolecule shares to the same degree, may serve as more than the basis of a novel imaging device for soft tissue. Collagen"s nonlinear optical properties in conjunction with its vast capacity for self-initiated conformational change--through self-assembly, site recognition, post-translational modification, and the like -make it an attractive candidate molecule for any of several demanding engineering applications, such as nanopatterning.

  14. Second harmonic generation of spectrally broadened femtosecond ytterbium laser radiation in a gas-filled capillary

    SciTech Connect

    Didenko, N V; Konyashchenko, Aleksandr V; Kostryukov, P V; Losev, Leonid L; Tenyakov, S Yu

    2011-09-30

    A 300-fs radiation pulse of an ytterbium laser with a wavelength of 1030 nm and energy of 150 {mu}J were converted to a 15-fs pulse with a wavelength of 515 nm by broadening the emission spectrum in a capillary filled with xenon and by generating the second harmonic in a KDP crystal. The energy efficiency of the conversion was 30 %.

  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. Improved Efficiency Type II Second Harmonic Generation

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P.; Walsh, Brian M.; Reichle, Donald J., Jr.

    2009-01-01

    Second harmonic efficiency is limited by lateral and temporal separation of the ordinary and extraordinary components of the fundamental. A mode locked dual beam laser demonstrated these effects and a novel method to minimize them.

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

    DOE PAGES

    Davidson, II, Roderick B.; Ziegler, Jed I.; Vargas, Guillermo; ...

    2015-05-01

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

  18. Second Harmonic Hectometric Radio Emission at Jupiter

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Gurnett, D. A.; Groene, J. B.

    1998-01-01

    Galileo has been in orbit around Jupiter since December 1995. The plasma wave instrument on board the spacecraft has occasionally detected a rotationally modulated attenuation band in the hectometric (HOM) emission that most likely is due to scattering of the radiation from density fluctuations along the Io L-shell, as reported earlier. The occurrence of the attenuation band is likely to be dependent on Io activity and the presence of density scattering centers along the Io-L-shell as well as the location of the source region. Some of the attenuation bands show clear indications of second harmonic emission. Without polarization measurements, it is difficult to place constraints on the local generation conditions based on the cyclotron maser instability, but the results imply that second harmonic emission could be present in the decametric (DAM) radiation as well. A survey of the data has revealed about 30 examples of second harmonic HOM.

  19. Second Harmonic Hectometric Radio Emission at Jupiter

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Gurnett, D. A.; Groene, J. B.

    1998-01-01

    Galileo has been in orbit around Jupiter since December 1995. The plasma wave instrument on board the spacecraft has occasionally detected a rotationally modulated attenuation band in the hectometric (HOM) emission that most likely is due to scattering of the radiation from density fluctuations along the Io L-shell, as reported earlier. The occurrence of the attenuation band is likely to be dependent on Io activity and the presence of density scattering centers along the Io L-shell as well as the location of the source region. Some of the attenuation bands show clear indications of second harmonic emission. Without polarization measurements, it is difficult to place constraints on the local generation conditions based on the cyclotron maser instability, but the results imply that second harmonic emission could be present in the decametric (DAM) radiation as well. A survey of the data has revealed about 30 examples of second harmonic HOM.

  20. Terahertz-field-induced second harmonic generation through Pockels effect in zinc telluride crystal.

    PubMed

    Cornet, Marion; Degert, Jérôme; Abraham, Emmanuel; Freysz, Eric

    2014-10-15

    We report on the second harmonic generation (SHG) of a near-infrared pulse in a zinc telluride crystal through the Pockels effect induced by an intense terahertz pulse. The temporal and angular behaviors of the SHG have been measured and agree well with theoretical predictions. This phenomenon, so far overlooked, makes it possible to generate second harmonic through cascading of two second-order nonlinear phenomena in the near-infrared and terahertz ranges. We also show how this cascading process can be used to sample terahertz pulses.

  1. Second harmonic generation and sum frequency generation

    SciTech Connect

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

    1990-01-01

    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.

  2. Second Harmonic Imaging of Membrane Potential.

    PubMed

    Loew, Leslie M; Lewis, Aaron

    2015-01-01

    The non-linear optical effect known as second harmonic generation (SHG) has been recognized since the earliest days of the laser. But it has only been in the last 20 years that it has begun to emerge as a viable microscope imaging contrast mechanism for visualization of cell and tissue structure and function. This is because only small modifications are required to equip a standard laser scanning 2-photon microscope for second harmonic imaging microscopy (SHIM). SHG signals from certain membrane-bound dyes are highly sensitive to membrane potential, indicating that SHIM may become a valuable probe of cell physiology. However, for the current generation of dyes and microscopes, the small signal size limits the number of photons that can be collected during the course of a fast action potential. Better dyes and optimized microscope optics could ultimately lead to the ability to image neuronal electrical activity with SHIM.

  3. Fast interferometric second harmonic generation microscopy

    PubMed Central

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

    2016-01-01

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

  4. Super/subradiant second harmonic generation

    NASA Astrophysics Data System (ADS)

    Koganov, Gennady A.; Shuker, Reuben

    2017-04-01

    A scheme for active second harmonics generation is suggested. The system comprises N three-level atoms in ladder configuration, situated into a resonant cavity. The system generates the field whose frequency is twice the frequency of the pumping laser, and the field phase is locked to the phase of the pumping field. It is found that the system can lase in either superradiant or subradiant regime, depending on the number of atoms N. When N passes some critical value the transition from the super to subradiance occurs in a phase-transition-like manner. Stability study of the steady state supports this conclusion. For experimental realization of the super/subradiant second harmonics generation we propose semiconductor quantum well structures, superconducting quantum circuits, and evanescently coupled waveguides in which equally spaced levels relevant to this study exist.

  5. Numerical simulation of self-compressed second-harmonic generation in type II potassium dihydrogen phosphate with a time predelay for Yb-doped solid-state lasers.

    PubMed

    Harimoto, Tetsuo; Aoyama, Makoto; Yamakawa, Koichi

    2007-12-24

    We report numerical results of second-harmonic generation in a type II potassium dihydrogen phosphate crystal with a time predelay for picosecond and/or femtosecond Yb-doped solid-state lasers, and clarify the dependence of the self compression in the second-harmonic laser pulse on the initial frequency chirp, fundamental duration and intensity, and phase-mismatching angle. We also show numerically the generation possibility of a self-compressed second-harmonic laser pulse near 20 fs.

  6. Promoting Spontaneous Second Harmonic Generation through Organogelation.

    PubMed

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

    2016-07-27

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

  7. Second harmonic generation from tyrosine containing peptides

    NASA Astrophysics Data System (ADS)

    Nasir, M. N.; Bergmann, E.; Benichou, E.; Russier-Antoine, I.; Lascoux, N.; Jonin, Ch.; Besson, F.; Brevet, P. F.

    2013-10-01

    The Second Harmonic Generation (SHG) response from Tyrosine-containing peptides at the air-water interface is presented. First, the quadratic hyperpolarizability of the aromatic amino acid Tyrosine obtained by Hyper Rayleigh Scattering is reported, demonstrating its potentiality as an endogenous molecular probe for SHG studies. Then, the single Tyrosine antimicrobial peptide Mycosubtilin is monitored at the air-water interface and compared to another peptide, Surfactin, lacking a Tyrosine residue. Adsorption kinetics and polarization analysis of the SHG intensity for the peptide monolayers clearly demonstrate that the SHG response from Mycosubtilin arises from Tyrosine. Besides, it confirms that indeed Tyrosine can be targeted as an endogenous molecular probe.

  8. Generating Second Harmonics In Nonlinear Resonant Cavities

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  9. Wiggler magnetic field assisted second harmonic generation in clusters

    NASA Astrophysics Data System (ADS)

    Aggarwal, Munish; Vij, Shivani; Kant, Niti

    2015-06-01

    Wiggler magnetic field assisted second harmonic generation in clusters has been investigated theoretically. An intense short-pulse laser propagating through a gas embedded with atomic clusters, converts it into hot plasma balls. For clusters with radius less than one tenth of the laser wavelength, the nonlinear restoration force dominates, which leads to second harmonic generation. The magnetic wiggler provides the uncompensated momentum to second harmonic photon, to make the process of harmonic generation resonant. We explore the impact of laser intensity and cluster size on the efficiency of second harmonic generation. Pulse slippage of second harmonic pulse out of the domain of fundamental laser pulse has been observed on account of group velocity mismatch between the fundamental and second harmonic pulse. Enhancement in the efficiency of the second harmonic is seen for the optimum values of wiggler magnetic field.

  10. Optical second harmonic generation from Pt nanowires

    NASA Astrophysics Data System (ADS)

    Hayashi, N.; Aratake, K.; Okushio, R.; Iwai, T.; Sugawara, A.; Sano, H.; Mizutani, G.

    2007-09-01

    We have measured optical second harmonic intensity from arrays of Pt nanowires of 20 nm and 9 nm average widths, as a function of the incident and output light polarizations, the azimuthal angle, and the excitation photon energy. The nanowires were fabricated through shadow deposition on self-organized NaCl(1 1 0) faceted templates. The anisotropy of the SH intensity from the Pt nanowires was found to be stronger than that from the Au nanowires reported previously. The effective nonlinear susceptibility element χ222(2), with the suffix 2 indicating the direction [1 1¯ 0], was observed for Pt nanowires, although it was not observed for Au nanowires. This difference is suggested to be due to the weaker suppression of the incident fundamental fields by the depolarization field in the Pt nanowires and the larger anisotropy in the nonlinearity of Pt nanowires due to the thinner widths.

  11. Lens-less surface second harmonic imaging.

    PubMed

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

    2012-09-24

    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.

  12. Lens-less surface second harmonic imaging

    PubMed Central

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

    2012-01-01

    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

  13. Multibeam second-harmonic generation by spatiotemporal shaping of femtosecond pulses.

    PubMed

    Martínez-Cuenca, Raúl; Mendoza-Yero, Omel; Alonso, Benjamín; Sola, Íñigo Juan; Mínguez-Vega, Gladys; Lancis, Jesús

    2012-03-01

    We present a technique for efficient generation of the second-harmonic signal at several points of a nonlinear crystal simultaneously. Multispot operation is performed by using a diffractive optical element that splits the near-infrared light of a mode-locked Ti:sapphire laser into an arbitrary array of beams that are transformed into an array of foci at the nonlinear crystal. We show that, for pulse temporal durations under 100 fs, spatiotemporal shaping of the pulse is mandatory to overcome chromatic dispersion effects that spread both in space and time the foci showing a reduced peak intensity that prevents nonlinear phenomena. We experimentally demonstrate arbitrary irradiance patterns for the second-harmonic signal consisting of more than 100 spots with a multipass amplifier delivering 28 fs, 0.8 mJ pulses at 1 kHz repetition rate.

  14. Second-harmonic generation with Bessel beams

    NASA Astrophysics Data System (ADS)

    Shatrovoy, Oleg

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

  15. High average power second harmonic generation in air

    SciTech Connect

    Beresna, Martynas; Kazansky, Peter G.; Svirko, Yuri; Barkauskas, Martynas; Danielius, Romas

    2009-09-21

    We demonstrate second harmonic vortex generation in atmospheric pressure air using tightly focused femtosecond laser beam. The circularly polarized ring-shaped beam of the second harmonic is generated in the air by fundamental beam of the same circular polarization, while the linear polarized beam produces two-lobe beam at the second harmonic frequency. The achieved normalized conversion efficiency and average second harmonic power are two orders of magnitude higher compared to those previously reported and can be increased up to 20 times by external gas flow. We demonstrate that the frequency doubling originates from the gradient of photoexcited free electrons created by pondermotive force.

  16. The polarization of second harmonic plasma emission

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    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.

  17. Second Harmonic Light Scattering from Macromolecules: Collagen.

    NASA Astrophysics Data System (ADS)

    Roth, Shmuel

    In this work we present the theory and practice of optical second harmonic generation (SHG) as applied to rat-tail tendon collagen. Our work is the first quantitative application of SHG to biological systems. The angular dependence of SHG is found to display a sharp, intense, forward peak superimposed on a broad background. The sharp peak is shown to imply long-range polar order, while the broad background corresponds to that predicted for the random "up"/"down" array of collagen fibrils seen with the electron microscope. The dependence of fibril diameter distribution on age and state of hydration is measured. Our experiments also reveal information concerning the structure of the fibrils and their arrangement in the tendon. The degree of polar order, the coherence length of tendon for harmonic generation and the absolute magnitude of the nonlinear susceptibility of the collagen fibril are also determined. The biological significance of these findings and the many advantages of SHG for the structural study of biological macromolecules and tissues are discussed.

  18. Second harmonic generation polarization properties of myofilaments

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  19. Second harmonic studies of liquid interfaces

    SciTech Connect

    Ong, S.

    1992-12-31

    This thesis reports on experimental studies of kinetics and equilibria at liquid interfaces using the technique of Second Harmonic Generation (SHG). In the first part, SHG was used to study the kinetics of adsorption of p-nitrophenol at the air/water interface of a flowing liquid jet. Measurements of the SH signal strength and the polarization of the SH light at various distances (times) along the jet axis yield information about the development of the density and orientation of p-nitrophenol at the air/water interface. The kinetics of adsorption was interpreted in terms of the Langmuir theory and was found to be consistent with this model. The free energy of adsorption obtained from the jet experiments was found to be the same as that obtained from static (equilibrium) experiments. The orientation of p-nitrophenol at the jet air/solution interface was the same as for the static (equilibrium) interface,which indicates that orientational equilibrium was rapidly achieved. It was also found that adsorption of nitrophenol to the air/water interface is not diffusion controlled, but rather is kinetically controlled by a barrier. SHG was then used to probe the silica/water interface.

  20. Polarization-dependent optical second-harmonic imaging of a rat-tail tendon.

    PubMed

    Stoller, Patrick; Kim, Beop-Min; Rubenchik, Alexander M; Reiser, Karen M; Da Silva, Luiz B

    2002-04-01

    Using scanning confocal microscopy, we measure the backscattered second harmonic signal generated by a 100 fs laser in rat-tail tendon collagen. Damage to the sample is avoided by using a continuous scanning technique, rather than measuring the signal at discrete points. The second harmonic signal varies by about a factor of 2 across a single cross section of the rat-tail tendon fascicle. The signal intensity depends both on the collagen organization and the backscattering efficiency. This implies that we cannot use intensity measurements alone to characterize collagen structure. However, we can infer structural information from the polarization dependence of the second harmonic signal. Axial and transverse scans for different linear polarization angles of the input beam show that second harmonic generation (SHG) in the rat-tail tendon depends strongly on the polarization of the input laser beam. We develop an analytical model for the SHG as a function of the polarization angle in the rat-tail tendon. We apply this model in determining the orientation of collagen fibrils in the fascicle and the ratio gamma between the two independent elements of the second-order nonlinear susceptibility tensor. There is a good fit between our model and the measured data.

  1. Dual aperture dipole magnet with second harmonic component

    DOEpatents

    Praeg, W.F.

    1983-08-31

    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.

  2. Dual aperture dipole magnet with second harmonic component

    DOEpatents

    Praeg, Walter F.

    1985-01-01

    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.

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

    SciTech Connect

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

    2011-10-15

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

  4. High-resolution second harmonic optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Jiang, Yi; Tomov, Ivan V.; Wang, Yimin; Chen, Zhongping

    2005-04-01

    A high-resolution Second Harmonic Optical Coherence Tomography (SH-OCT) system is demonstrated using a spectrum broadened femtosecond Ti:sapphire laser. An axial resolution of 4.2 μm at the second harmonic wave center wavelength of 400 nm has been achieved. Because the SH-OCT system uses the second harmonic generation signals that strongly depend on the orientation, polarization and local symmetry properties of chiral molecules, this technique provides unique contrast enhancement to conventional optical coherence tomography. The system is applied to image biological tissues like the rat-tail tendon. Images of highly organized collagen fibrils in the rat-tail tendon have been demonstrated.

  5. Optical fiber tip for field-enhanced second harmonic generation.

    PubMed

    Pal, Sudipta Sarkar; Mondal, Samir K; Bajpai, Phun Phun; Kapur, Pawan

    2012-10-01

    We propose a simple optical fiber tip for field-enhanced second harmonic generation (SHG). The tip shows nonlinear phenomena of SHG over a wide range of sources, at least from 630 to 830 nm. The optical field corresponding to the second harmonic appears as a nondiffracting bottle beam with voids due to the surface curvature of the tip. The field-enhanced second harmonic can also induce surface plasmons, converting the tip to a plasmonic probe with reduced background signal. The tip can be useful in nanophotonics characterization. As an example, we demonstrate the tip's response as a surface-enhanced Raman spectroscopy probe.

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

    PubMed

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

    2015-11-30

    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.

  7. The second-harmonic generation in a dissipative and dispersion layered structure

    NASA Astrophysics Data System (ADS)

    Soltanmohammadi, Jamshid; Jamshidi-Ghaleh, Kazem; Arghand-Hesar, Afshin; Lotfi, Erik S.; Masalehdan, Hossein

    2015-10-01

    Conversion efficiency of second-harmonic generation (SHG) in a multicrystal structure arrangement, under linearly absorption of interacting waves was analytically investigated. Different linear absorption and nonlinear interaction coefficients were considered for both of the fundamental and the second harmonic waves in cascade layers. The intensity-constant approximation on fundamental wave radiation was applied in calculations. Behavior of conversion efficiency with interaction coherence length of fundamental wave, phase miss-matching and ratio of linear absorption coefficients were graphically illustrated. The results are shown that in multicrystal structure scheme, the conversion efficiency can be tuned by the interaction coherent length and it is possible to compensate the phase differences induced in the previous layers. The phase compensation between the layers is the physical reason of efficiency improvement. Contribution to the topical issue "Advanced Electromagnetics Symposium (AES 2014) - Elected submissions", edited by Adel Razek

  8. Motionless polarization-resolved second harmonic generation imaging of corneal collagen

    NASA Astrophysics Data System (ADS)

    Breunig, Hans G.; Batista, Ana; Uchugonova, Aisada; König, Karsten

    2015-03-01

    Polarization-resolved second harmonic generation microscopy was used to investigate the collagenous structures of cornea samples in vitro in forward and backward direction. Although structural features appear different in both directions, following an approach by Latour et al. the collagen domain orientation is determined in forward as well as in backward direction, the latter being the only accessible direction for in vivo imaging. The experimental setup enables fast and completely motionless rotation of the polarization direction of 100 fs pulses by a polarization rotation based on a liquid crystal retarder.

  9. Second harmonic inversion for ultrasound contrast harmonic imaging.

    PubMed

    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

    2011-06-07

    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 f(0) and the same amplitude P(0) 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.

  10. Second harmonic generation in graphene-coated nanowires.

    PubMed

    Gao, Yixiao; Shadrivov, Ilya V

    2016-08-01

    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.

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

    SciTech Connect

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

    2003-04-04

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

  12. Second-harmonic radiating imaging probes and harmonic holography

    NASA Astrophysics Data System (ADS)

    Pu, Ye; Psaltis, Demetri

    2016-10-01

    Compared with other imaging probes such as fluorescent dyes and quantum dots, second-harmonic radiating imaging probes (SHRIMPs) provide a unique ultrafast, coherent optical contrast that is free of photobleaching and emission intermittency. Using the second-harmonic signal emitted from SHRIMPs, harmonic holography achieves threedimensional holographic imaging with a color contrast similar to fluorescence microscopy where the uninterested background scattering is efficiently suppressed by an optical filter. The coherent contrast provided by SHRIMPs also enables imaging through turbid media via digital phase conjugation. Here we review the developments and applications of SHRIMPs and harmonic holography.

  13. Effect of structural modification on second harmonic generation in collagen

    NASA Astrophysics Data System (ADS)

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

    2003-07-01

    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.

  14. Confocal Imaging of Biological Tissues Using Second Harmonic Generation

    SciTech Connect

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

    2000-03-06

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

  15. Theory of second harmonic generation in randomly oriented species

    NASA Astrophysics Data System (ADS)

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

    1995-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    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.

  17. Monolithically integrated multi-wavelength filter and second harmonic generator in aperiodically poled lithium niobate.

    PubMed

    Chang, C L; Chen, Y H; Lin, C H; Chang, J Y

    2008-10-27

    We report on the design and experimental characterization of aperiodically poled lithium niobate (APLN) crystals for use in monolithically integrated dual nonlinear-optical devices. A cascade and a single aperiodic-domain-structure designs based on simulated annealing method were constructed in LiNbO(3) to simultaneously perform as 4-channel electro-optically active (EOA) filters and 4-channel frequency doublers in the telecom band. We found that we could obtain a 2.44-fold enhancement in second-harmonic-generation conversion efficiency and a 2.4-time reduction in filter transmission bandwidth with the single APLN device over the cascade one when the same device length of 2 cm and the EOA field of 1027 V/mm were used.

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

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

    SciTech Connect

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

    2015-03-31

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

  20. Imaging with second-harmonic radiation probes in living tissue

    PubMed Central

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

    2011-01-01

    We demonstrate that second-harmonic radiation imaging probes are efficient biomarkers for imaging in living tissue. We show that 100 nm and 300 nm BaTiO3 nanoparticles used as contrast markers could be detected through 50 μm and 120 μm of mouse tail tissue in vitro or in vivo. Experimental results and Monte-Carlo simulations are in good agreement. PMID:21991545

  1. 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)

    2011-01-01

    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.

  2. Second-Harmonic Generation in Optical Fibers and Glass.

    DTIC Science & Technology

    1992-09-30

    fully born out, and that it is possible to use its polarization properties to map out the spatial profile of the induced electric field. In all of...fibers themselves. 2) The induced second-order nonlinearity arises from a DC electric field which is induced inside the glass by light beams containing...a ____ • fundamental frequency (W) and its second harmonic (2wo). 3) The light beams induce the S_ DC electric field through a multiple-photon

  3. Dynamics of Flat Bunches with Second Harmonic RF

    SciTech Connect

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

    2010-05-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2006-09-01

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

  5. Quantitative second-harmonic generation microscopy in collagen

    NASA Astrophysics Data System (ADS)

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

    2003-09-01

    The second-harmonic signal in collagen, even in highly organized samples such as rat tail tendon fascicles, varies significantly with position. Previous studies suggest that this variability may be due to the parallel and antiparallel orientation of neighboring collagen fibrils. We applied high-resolution second-harmonic generation microscopy to confirm this hypothesis. Studies in which the focal spot diameter was varied from ~1 to ~6 μm strongly suggest that regions in which collagen fibrils have the same orientation in rat tail tendon are likely to be less than ~1 μm in diameter. These measurements required accurate determination of the focal spot size achieved by use of different microscope objectives; we developed a technique that uses second-harmonic generation in a quartz reference to measure the focal spot diameter directly. We also used the quartz reference to determine a lower limit (dXXX > 0.4 pm/V) for the magnitude of the second-order nonlinear susceptibility in collagen.

  6. Second-harmonic generation of femtosecond high-intensity Ti:sapphire laser pulses

    NASA Astrophysics Data System (ADS)

    Mori, Kurumi; Tamaki, Yusuke; Obara, Minoru; Midorikawa, Katsumi

    1998-03-01

    The second-harmonic generation (SHG) of ultrashort Ti:sapphire laser pulses in potassium dihydrogen phosphate crystal in type-I phase-matching geometry has been investigated theoretically, including the effects of cubic nonlinearity. It is found that the phase mismatch due to the broad bandwidth associated with the short pulse width limits the maximum conversion efficiency to less than 60%, and the temporal shape of the converted pulse has an intensity modulation at an incident intensity of 100 GW/cm2 for a 100 fs pulse. In order to increase the energy conversion efficiency and improve the temporal pulse shape, a new SHG geometry using two antiparallel tilted crystals is discussed.

  7. Increasing efficiency of two-photon excited fluorescence and second harmonic generation using ultrashort pulses

    NASA Astrophysics Data System (ADS)

    Tang, Shuo; Krasieva, Tatiana B.; Chen, Zhongping; Tempea, Gabriel; Tromberg, Bruce J.

    2006-02-01

    Multiphoton microscopy (MPM) has become an important tool for high-resolution and non-invasive imaging in biological tissues. However, the efficiencies of two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) are relatively low because of their nonlinear nature. Therefore, it is critical to optimize laser parameters for most efficient excitation of MPM. Reducing the pulse duration can increase the peak intensity of excitation and thus potentially increase the excitation efficiency. In this paper, a multiphoton microscopy system using a 12 fs Ti:Sapphire laser is reported. With adjustable dispersion pre-compensation, the pulse duration at the sample location can be varied from 400 fs to sub-20 fs. The efficiencies of TPEF and SHG are studied for the various pulse durations, respectively. Both TPEF and SHG are found to increase proportionally to the inverse of the pulse duration for the entire tested range. To transmit most of the SHG and TPEF signals, the spectral transmission widow of the detection optics needs to be carefully considered. Limitation from phase-matching in SHG generation is not significant because the effective interaction length for SHG is less than 10 μm at the focal depth of the objectives. These results are important in improving MPM excitation efficiency using ultrashort pulses. MPM images from human artery wall are also demonstrated.

  8. Birefringent-multicrystal, single-pass, continuous-wave second-harmonic-generation in deep-ultraviolet

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    We report implementation of compact cascaded multicrystal scheme for single-pass second-harmonic-generation (SHG), using birefringent crystal, for continuous-wave (cw) deep ultraviolet (UV) generation. The system comprises of 4 cascaded stages, is based on critical phase-matched interaction in β-BaB2O4 (BBO), and pumped by a cw singlefrequency 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 in Gaussian spatial beam quality with a circularity of >70%.

  9. Controlling attosecond angular streaking with second harmonic radiation.

    PubMed

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

    2015-04-15

    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.

  10. Efficient second harmonic generation of picosecond laser pulses.

    NASA Technical Reports Server (NTRS)

    Rabson, T. A.; Ruiz, H. J.; Shah, P. L.; Tittel, F. K.

    1972-01-01

    Efficient conversion to the second harmonic (SH) using KD2PO4 and CsH2AsO4 crystals inside a folded cavity of a high-power-dye mode-locked neodymium-glass laser is reported. For the first time, frequency-doubled picosecond light pulses have been obtained in CsH2AsO4 with peak powers of the order of 1 GW/sq cm at 0.531 micron for an effective pump power density of 4 GW/sq cm.

  11. 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

    2012-02-01

    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.

  12. Second harmonic generation of chiral-modified silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Tao, Yue

    Chiral molecules, which exist under enantiomers with non-mirror-symmetrical structures, have been the subject of intense research for their linear and nonlinear optical activities. Cysteine is such a chiral amino acid found as a building block of proteins throughout human bodies. Second harmonic generation (SHG) has been considered to investigate chiral molecules. SHG from metallic nanoparticles is promising for nanoplasmonics and photonic nanodevice applications. Therefore, it's desirable to combine and study nonlinear properties due to both chirality and metallic nanoparticles, and help developing an alternatively optical diagnostic of chiral molecules. Our experiments are carried out with the FemtoFiber Scientific FFS laser system. SHG of silver nanoparticles (Ag NPs) modified by either L-Cysteine (L-C) or D-Cysteine (D-C) is observed, where L-Cysteine and D-Cysteine are a pair of enantiomers. Ag NPs are deposited through Vacuum Thermal Evaporation, controlled under different deposition thicknesses. UV-Vis/IR spectra and AFM are used to characterize Ag NPs under different conditions. Transmitted SHG measurements dependent on incidence are recorded with standard lock-in techniques. Deposition thickness of vacuum thermal evaporation plays an important role in forming diverse Ag NPs, which strongly imparts the intensity of SHG. Second harmonic intensity as a function of the incident angle presents similar results for Ag NPs with or without L-Cysteine or D-Cysteine modification, in the output of p- and s-polarization. However, we monitor reversed rotation difference in second harmonic intensities at linearly +45° and -45° polarization for L-C/Ag NPs and D-C/Ag NPs, while there's no difference at linearly +45° and -45° polarization for Ag NPs alone. This optical rotation difference in SHG is termed as SHG-ORD. Also, for second harmonic light fixed at p-polarization, L-C/Ag NPs and D-C/Ag NPs exhibit a reversely net difference for SHG excited by right and left

  13. High-resolution frequency domain second harmonic optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Su, Jianping; Tomov, I. V.; Jiang, Yi; Chen, Zhongping

    2007-02-01

    We used continuum generated in an 8.5 cm long fiber by a femtosecond Yb fiber laser to improve threefold the axial resolution of frequency domain SH-OCT to 12μm. The acquisition time was shortened by more than two orders of magnitude compared to time domain SH-OCT. The system was applied to image biological tissue of fish scales, pig leg tendon and rabbit eye sclera. Highly organized collagen fibrils can be visualized in the recorded images. Polarization dependence on second harmonic has been used to obtain polarization resolved images.

  14. Reconstruction of complementary images in second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Gao, Liang; Jin, Lei; Xue, Ping; Xu, Jun; Wang, Yi; Ma, Hui; Chen, Dieyan

    2006-05-01

    Second harmonic generation microscopy(SHGM) has become widely used to image biological samples. Due to the complexity of biological samples, more and more effort has been put on polarization imaging in SHGM technology to uncover their structures. In this work, we put forward a novel stitching method based on careful mathematical calculation, and accomplish it by rotating laser polarization. We first show its validity in imaging a perfectly synthesized bio-origin polymer poly (3-hyroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx). Then, we test its power by getting a true image of fibrillar collagen structure of rat-tail tendon.

  15. Second-harmonic generation in a polymer Langmuir - Blodgett film

    SciTech Connect

    Ivanova, V N; Kudryavtsev, V V; Lebedeva, G K; Maslyanitsyn, I A; Shigorin, V D; Chudinova, G K

    1998-09-30

    Second-harmonic generation was used to investigate nonlinear optical properties and the structure of multilayer Langmuir - Blodgett films of a copolymer of fluoroalkylmethacrylate with methacrylates containing an azo dye and a cinnamoyl group inside a chain. Quantum-chemical calculations were made of the components of the molecular hyperpolarisability tensor in which the intermolecular interactions were taken into account. The orientation of nonlinear optical fragments of a polymer chain relative to the substrate and components of the quadratic optical susceptibility tensor of the film were determined. (nonlinear optical phenomena)

  16. Characteristics of pulse width for an enhanced second harmonic generation

    NASA Astrophysics Data System (ADS)

    Zhang, Yun; Hyodo, Masaharu; Okada-Shudo, Yoshiko; Zhu, Yun; Wang, Xiaoyang; Zhu, Yong; Wang, Guiling; Chen, Chuangtian; Watanabe, Shuntaro; Watanabe, Masayoshi

    2017-03-01

    Temporal characteristics of a cavity enhancement second harmonic (SH) generation for picosecond laser pulse are investigated. We experimentally measured pulse width changes that were indued by group velocity mismatching (GVM), SH process, and enhancement cavity. It indicates that the generated pulse width is a combined effect of the GVM and SH process. Meanwhile, the effect of the enhancement cavity can be avoided by controlling its free spectrum range. A interferometric autocorrelator with a KBBF-PCD as nonlinear crystal is also composed and this extends the measurement light wavelength below 410 nm.

  17. Second harmonic imaging and scoring of collagen in fibrotic tissues

    NASA Astrophysics Data System (ADS)

    Strupler, M.; Pena, A.-M.; Hernest, M.; Tharaux, P.-L.; Martin, J.-L.; Beaurepaire, E.; Schanne-Klein, M.-C.

    2007-04-01

    We compare second harmonic generation (SHG) to histological and immunohistochemical techniques for the visualization and scoring of collagen in biological tissues. We show that SHG microscopy is highly specific for fibrillar collagens and that combined SHG and two-photon excited fluorescence (2PEF) imaging can provide simultaneous three-dimensional visualization of collagen synthesis and assembly sites in transgenic animal models expressing GFP constructs. Finally, we propose several scores for characterizing collagen accumulation based on SHG images and appropriate for different types of collagen distributions. We illustrate the sensitivity of these scores in a murine model of renal fibrosis using a morphological segmentation of the tissue based on endogenous 2PEF signals.

  18. Singly resonant second-harmonic-generation frequency combs

    NASA Astrophysics Data System (ADS)

    Hansson, T.; Leo, F.; Erkintalo, M.; Coen, S.; Ricciardi, I.; De Rosa, M.; Wabnitz, S.

    2017-01-01

    We consider frequency comb generation in dispersive singly resonant second-harmonic-generation cavity systems. Using a single temporal mean-field equation for the fundamental field that features a noninstantaneous nonlinear response function, we model the temporal and spectral dynamics and analyze comb generation, continuous wave bistability, and modulational instability. It is found that, owing to the significant temporal walk-off between the fundamental and second-harmonic fields, modulational instability can occur even in the complete absence of group-velocity dispersion. We further consider the relation of our model to a previously proposed modal expansion approach, and present a derivation of a general system of coupled mode equations. We show that the two models provide very similar predictions and become exactly equivalent in the limit that absorption losses and group-velocity dispersion at the fundamental frequency are neglected. Finally, we perform numerical simulations that show examples of the variety of comb states that are possible in phase-matched quadratic resonators, and discuss the dynamics of the comb formation process.

  19. Characterization of Second Harmonic Afterburner Radiation at the LCLS

    SciTech Connect

    Nuhn, Heinz-Dieter

    2010-09-14

    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.

  20. Second-harmonic generation investigation of collagen thermal denaturation

    NASA Astrophysics Data System (ADS)

    Chen, Wei-Liang; Sun, Yen; Lin, Sung-Jan; Jee, Shiou-Hwa; Chen, Yang-Fang; Lin, Ling-Chih; So, Peter T. C.; Dong, Chen-Yuan

    2007-02-01

    Using the technique of second-harmonic generation (SHG) microscopy we obtained large area image of type I collagen from rat tail tendon as it is heated from 40°C to 70°C for 0 to 180 minutes. The high resolution images allowed us to investigate the collagen structural change. We observed that heating the tendon below the temperature of 54°C does not produce any change in the averaged SHG intensity. At the heating temperature of 54°C and above, we find that increasing the heating temperature and time leads to decreasing SHG intensity. As the tendon is heated above 54°C, a decrease in the SHG signal occurs uniformly throughout the tendon, but the regions where the SHG signal vanishes form a tiger-tail like pattern. By comparing the relative SHG intensities in small and large areas, we found that the denaturation process responsible for forming the tiger-tail like pattern occurs at a higher rate than the global denaturation process occurring throughout the tendon. Our results show that second-harmonic generation microscopy is effective in monitoring the thermal damage to collagen and has potential applications in biomedicine.

  1. Polarization-Modulated Second Harmonic Generation Microscopy in Collagen

    SciTech Connect

    Stoller, P C

    2002-09-30

    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

  2. Polarization-modulated second harmonic generation in collagen.

    PubMed Central

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

    2002-01-01

    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

  3. Second harmonic generation in microcrystallite films of ultrasmall Si nanoparticles

    SciTech Connect

    Nayfeh, M. H.; Akcakir, O.; Belomoin, G.; Barry, N.; Therrien, J.; Gratton, E.

    2000-12-18

    We dispersed crystalline Si into a colloid of ultrasmall nano particles ({approx}1 nm), and reconstituted it into microcrystallites films on device-quality Si. The film is excited by near-infrared femtosecond two-photon process in the range 765--835 nm, with incident average power in the range 15--70 mW, focused to {approx}1 {mu}m. We have observed strong radiation at half the wavelength of the incident beam. The results are analyzed in terms of second-harmonic generation, a process that is not allowed in silicon due to the centrosymmetry. Ionic vibration of or/and excitonic self-trapping on novel radiative Si--Si dimer phase, found only in ultrasmall nanoparticles, are suggested as a basic mechanism for inducing anharmonicity that breaks the centrosymmetry.

  4. Second Harmonic Generation of Nanoscale Phonon Wave Packets.

    PubMed

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

    2015-11-06

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

  5. Exciton-Polariton Fano Resonance Driven by Second Harmonic Generation

    NASA Astrophysics Data System (ADS)

    Wang, Yafeng; Liao, Liming; Hu, Tao; Luo, Song; Wu, Lin; Wang, Jun; Zhang, Zhe; Xie, Wei; Sun, Liaoxin; Kavokin, A. V.; Shen, Xuechu; Chen, Zhanghai

    2017-02-01

    Angle-resolved second harmonic generation (SHG) spectra of ZnO microwires show characteristic Fano resonances in the spectral vicinity of exciton-polariton modes. We observe a resonant peak followed by a strong dip in SHG originating from the constructive and destructive interference of the nonresonant SHG and the resonant contribution of the polariton mode. It is demonstrated that the Fano line shape, and thus the Fano asymmetry parameter q , can be tuned by the phase shift of the two channels. We develop a model to calculate the phase-dependent q as a function of the radial angle in the microwire and achieve a good agreement with the experimental results. The deduced phase-to-q relation unveils the crucial information about the dynamics of the system and offers a tool for control on the line shape of the SHG spectra in the vicinity of exciton-polariton modes.

  6. 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

    2014-05-01

    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.

  7. 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.

    2015-02-01

    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.

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

    PubMed

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

    2011-11-07

    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.

  9. Second harmonic plasma emission involving ion sound waves

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.

    1987-01-01

    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.

  10. Exciton-Polariton Fano Resonance Driven by Second Harmonic Generation.

    PubMed

    Wang, Yafeng; Liao, Liming; Hu, Tao; Luo, Song; Wu, Lin; Wang, Jun; Zhang, Zhe; Xie, Wei; Sun, Liaoxin; Kavokin, A V; Shen, Xuechu; Chen, Zhanghai

    2017-02-10

    Angle-resolved second harmonic generation (SHG) spectra of ZnO microwires show characteristic Fano resonances in the spectral vicinity of exciton-polariton modes. We observe a resonant peak followed by a strong dip in SHG originating from the constructive and destructive interference of the nonresonant SHG and the resonant contribution of the polariton mode. It is demonstrated that the Fano line shape, and thus the Fano asymmetry parameter q, can be tuned by the phase shift of the two channels. We develop a model to calculate the phase-dependent q as a function of the radial angle in the microwire and achieve a good agreement with the experimental results. The deduced phase-to-q relation unveils the crucial information about the dynamics of the system and offers a tool for control on the line shape of the SHG spectra in the vicinity of exciton-polariton modes.

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

    NASA Astrophysics Data System (ADS)

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

    1995-09-01

    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

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

    PubMed

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

    2014-06-07

    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.

  13. Probing the Near-Field of Second-Harmonic Light around Plasmonic Nanoantennas.

    PubMed

    Metzger, Bernd; Hentschel, Mario; Giessen, Harald

    2017-03-08

    We introduce a new concept that enables subwavelength polarization-resolved probing of the second-harmonic near-field distribution of plasmonic nanostructures. As a local sensor, this method utilizes aluminum nanoantennas, which are resonant to the second-harmonic wavelength and which allow to efficiently scatter the local second-harmonic light to the far-field. We place these sensors into the second-harmonic near-field generated by plasmonic nanostructures and carefully vary their position and orientation. Observing the second-harmonic light resonantly scattered by the aluminum nanoantennas provides polarization-resolved information about the local second-harmonic near-field distribution. We then investigate the polarization-resolved second-harmonic near-field of inversion symmetric gold dipole nanoantennas. Interestingly, we find strong evidence that the second-harmonic dipole is predominantly oriented perpendicular to the gold nanoantenna long axis, although the excitation laser is polarized parallel to the nanoantennas. We believe that our investigations will help to disentangle the highly debated origin of the second-harmonic response of inversion symmetric plasmonic structures. Furthermore, we believe that our new method, which enables the measurement of local nonlinear electric fields, will find widespread implementation and applications in nonlinear near-field optical microscopy.

  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.

    2014-11-14

    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. Second harmonic generation from the ‘centrosymmetric’ crystals

    PubMed Central

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

    2015-01-01

    Second harmonic generation (SHG) is a well known non-linear optical phenomena which can be observed only in non-centrosymmetric crystals due to non-zero hyperpolarizability. In the current work we observed SHG from a Zn(II) complex which was originally thought to have crystallized in the centrosymmetric space group C2/c. This has been attributed to the unequal antiparallel packing of the metal complexes in the non-symmetric space group Cc or residual non-centrosymmetry in C2/c giving rise to polarizability leading to strong SHG. The enhancement of SHG by UV light has been attributed to the increase in non-centrosymmetry and hence polarity of packing due to strain induced in the crystals. The SHG signals measured from these crystals were as large as potassium dihydrogen phosphate crystals, KH2PO4 (KDP), and showed temperature dependence. The highest SHG efficiency was observed at 50 K. The SHG phenomenon was observed at broad wavelengths ranging from visible to below-red in these crystals. PMID:25995840

  16. Imaging articular cartilage using second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

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

    2006-02-01

    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.

  17. Extraordinary Second Harmonic Generation in tungsten disulfide monolayers.

    PubMed

    Janisch, Corey; Wang, Yuanxi; Ma, Ding; Mehta, Nikhil; Elías, Ana Laura; Perea-López, Néstor; Terrones, Mauricio; Crespi, Vincent; Liu, Zhiwen

    2014-07-02

    We investigate Second Harmonic Generation (SHG) in monolayer WS₂ both deposited on a SiO₂/Si substrate or suspended using transmission electron microscopy grids. We find unusually large second order nonlinear susceptibility, with an estimated value of d(eff) ~ 4.5 nm/V nearly three orders of magnitude larger than other common nonlinear crystals. In order to quantitatively characterize the nonlinear susceptibility of two-dimensional (2D) materials, we have developed a formalism to model SHG based on the Green's function with a 2D nonlinear sheet source. In addition, polarized SHG is demonstrated as a useful method to probe the structural symmetry and crystal orientation of 2D materials. To understand the large second order nonlinear susceptibility of monolayer WS₂, density functional theory based calculation is performed. Our analysis suggests the origin of the large nonlinear susceptibility in resonance enhancement and a large joint density of states, and yields an estimate of the nonlinear susceptibility value d(eff) = 0.77 nm/V for monolayer WS₂, which shows good order-of-magnitude agreement with the experimental result.

  18. 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

    2014-09-01

    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.

  19. 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.

    2015-03-01

    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

  20. Suppression of Radiative Damping and Enhancement of Second Harmonic Generation in Bull's Eye Nanoresonators.

    PubMed

    Yi, Jue-Min; Smirnov, Vladimir; Piao, Xianji; Hong, Jiho; Kollmann, Heiko; Silies, Martin; Wang, Wei; Groß, Petra; Vogelgesang, Ralf; Park, Namkyoo; Lienau, Christoph

    2016-01-26

    We report a drastic increase of the damping time of plasmonic eigenmodes in resonant bull's eye (BE) nanoresonators to more than 35 fs. This is achieved by tailoring the groove depth of the resonator and by coupling the confined plasmonic field in the aperture to an extended resonator mode such that spatial coherence is preserved over distances of more than 10 μm. Experimentally, this is demonstrated by probing the plasmon dynamics at the field level using broadband spectral interferometry. The nanoresonator allows us to efficiently concentrate the incident field inside the central aperture of the BE and to tailor its local optical nonlinearity by varying the aperture geometry. By replacing the central circular hole with an annular ring structure, we obtain 50-times higher second harmonic generation efficiency, allowing us to demonstrate the efficient concentration of long-lived plasmonic modes inside nanoapertures by interferometric frequency-resolved autocorrelation. Such a light concentration in a nanoresonator with high quality factor has high potential for sensing and coherent control of light-matter interactions on the nanoscale.

  1. Three-dimensional structural imaging of starch granules by second-harmonic generation circular dichroism.

    PubMed

    Zhuo, G-Y; Lee, H; Hsu, K-J; Huttunen, M J; Kauranen, M; Lin, Y-Y; Chu, S-W

    2014-03-01

    Chirality is one of the most fundamental and essential structural properties of biological molecules. Many important biological molecules including amino acids and polysaccharides are intrinsically chiral. Conventionally, chiral species can be distinguished by interaction with circularly polarized light, and circular dichroism is one of the best-known approaches for chirality detection. As a linear optical process, circular dichroism suffers from very low signal contrast and lack of spatial resolution in the axial direction. It has been demonstrated that by incorporating nonlinear interaction with circularly polarized excitation, second-harmonic generation circular dichroism can provide much higher signal contrast. However, previous circular dichroism and second-harmonic generation circular dichroism studies are mostly limited to probe chiralities at surfaces and interfaces. It is known that second-harmonic generation, as a second-order nonlinear optical effect, provides excellent optical sectioning capability when combined with a laser-scanning microscope. In this work, we combine the axial resolving power of second-harmonic generation and chiral sensitivity of second-harmonic generation circular dichroism to realize three-dimensional chiral detection in biological tissues. Within the point spread function of a tight focus, second-harmonic generation circular dichroism could arise from the macroscopic supramolecular packing as well as the microscopic intramolecular chirality, so our aim is to clarify the origins of second-harmonic generation circular dichroism response in complicated three-dimensional biological systems. The sample we use is starch granules whose second-harmonic generation-active molecules are amylopectin with both microscopic chirality due to its helical structure and macroscopic chirality due to its crystallized packing. We found that in a starch granule, the second-harmonic generation for right-handed circularly polarized excitation is

  2. Studies of surfaces using optical second-harmonic generation

    SciTech Connect

    Tom, H.W.K.

    1984-04-01

    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.

  3. Asymmetric Gaussian harmonic steering in second-harmonic generation

    NASA Astrophysics Data System (ADS)

    Olsen, M. K.

    2013-11-01

    Intracavity second-harmonic generation is one of the simplest of the quantum optical processes and is well within the expertise of most optical laboratories. It is well understood and characterized, both theoretically and experimentally. We show that it can be a source of continuous-variable asymmetric Gaussian harmonic steering with fields which have a coherent excitation, hence combining the important effects of harmonic entanglement and asymmetric steering in one easily controllable device, adjustable by the simple means of tuning the cavity loss rates at the fundamental and harmonic frequencies. We find that whether quantum steering is available via the standard measurements of the Einstein-Podolsky-Rosen correlations can depend on which quadrature measurements are inferred from output spectral measurements of the fundamental and the harmonic. Altering the ratios of the cavity loss rates can be used to tune the regions where symmetric steering is available, with the results becoming asymmetric over all frequencies as the cavity damping at the fundamental frequency becomes significantly greater than at the harmonic. This asymmetry and its functional dependence on frequency is a potential new tool for experimental quantum information science, with possible utility for quantum key distribution. Although we show the effect here for Gaussian measurements of the quadratures, and cannot rule out a return of the steering symmetry for some class of non-Gaussian measurements, we note here that the system obeys Gaussian statistics in the operating regime investigated and Gaussian inference is at least as accurate as any other method for calculating the necessary correlations. Perhaps most importantly, this system is simpler than any other methods we are aware of which have been used or proposed to create asymmetric steering.

  4. Multiphoton fluorescence and second harmonic generation microscopy for imaging keratoconus

    NASA Astrophysics Data System (ADS)

    Sun, Yen; Lo, Wen; Lin, Sung-Jan; Lin, Wei-Chou; Jee, Shiou-Hwa; Tan, Hsin-Yuan; Dong, Chen-Yuan

    2006-02-01

    The purpose of this study is to assess the possible application of multiphoton fluorescence and second harmonic generation (SHG) microscopy for imaging the structural features of keratoconus cornea and to evaluate its potential as being a clinical in vivo monitoring technique. Using the near-infrared excitation source from a titanium-sapphire laser pumped by a diode-pumped, solid state (DPSS) laser system, we can induce and simultaneously acquire multiphoton autofluorescence and SHG signals from the cornea specimens with keratoconus. A home-modified commercial microscope system with specified optical components is used for optimal signal detection. Keratoconus cornea button from patient with typical clinical presentation of keratoconus was obtained at the time of penetrating keratoplasty. The specimen was also sent for the histological examination as comparison. In all samples of keratoconus, destruction of lamellar structure with altered collagen fiber orientation was observed within whole layer of the diseased stromal area. In addition, the orientation of the altered collagen fibers within the cone area shows a trend directing toward the apex of the cone, which might implicate the biomechanical response of the keratoconus stroma to the intraocular pressure. Moreover, increased autofluorescent cells were also found in the cone area, with increased density as one approaches the apical area. In conclusion, multiphoton autofluorescence and SHG microscopy non-invasively demonstrated the morphological features of keratoconus cornea, especially the structural alternations of the stromal lamellae. We believe that in the future the multiphoton microscopy can be applied in vivo as an effective, non-invasive diagnostic and monitoring technique for keratoconus.

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

    SciTech Connect

    Mullin, Christopher Shane

    1993-12-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2005-03-01

    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.

  7. Crystallographic Mapping of Guided Nanowires by Second Harmonic Generation Polarimetry

    PubMed Central

    2017-01-01

    The growth of horizontal nanowires (NWs) guided by epitaxial and graphoepitaxial relations with the substrate is becoming increasingly attractive owing to the possibility of controlling their position, direction, and crystallographic orientation. In guided NWs, as opposed to the extensively characterized vertically grown NWs, there is an increasing need for understanding the relation between structure and properties, specifically the role of the epitaxial relation with the substrate. Furthermore, the uniformity of crystallographic orientation along guided NWs and over the substrate has yet to be checked. Here we perform highly sensitive second harmonic generation (SHG) polarimetry of polar and nonpolar guided ZnO NWs grown on R-plane and M-plane sapphire. We optically map large areas on the substrate in a nondestructive way and find that the crystallographic orientations of the guided NWs are highly selective and specific for each growth direction with respect to the substrate lattice. In addition, we perform SHG polarimetry along individual NWs and find that the crystallographic orientation is preserved along the NW in both polar and nonpolar NWs. While polar NWs show highly uniform SHG along their axis, nonpolar NWs show a significant change in the local nonlinear susceptibility along a few micrometers, reflected in a reduction of 40% in the ratio of the SHG along different crystal axes. We suggest that these differences may be related to strain accumulation along the nonpolar wires. We find SHG polarimetry to be a powerful tool to study both selectivity and uniformity of crystallographic orientations of guided NWs with different epitaxial relations. PMID:28094977

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

    SciTech Connect

    Zhao, X.

    1992-12-31

    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.

  9. Experimental observation of cumulative second-harmonic generation of lamb waves propagating in long bones.

    PubMed

    Zhang, Zhenggang; Liu, Dan; Deng, Mingxi; Ta, Dean; Wang, Weiqi

    2014-07-01

    The experimental observation of cumulative second-harmonic generation of fundamental Lamb waves in long bones is reported. Based on the modal expansion approach to waveguide excitation and the dispersion characteristics of Lamb waves in long bones, the mechanism underlying the generation and accumulation of second harmonics by propagation of the fundamental Lamb waves was investigated. An experimental setup was established to detect the second-harmonic signals of Lamb wave propagation in long bones in vitro. Through analysis of the group velocities of the received signals, the appropriate fundamental Lamb wave modes and the duration of the second-harmonic signals could be identified. The integrated amplitude of the time-domain second-harmonic signal was introduced and used to characterize the efficiency of second-harmonic generation by fundamental Lamb wave propagation. The results indicate that the second-harmonic signal generated by fundamental Lamb waves propagating in long bones can be observed clearly, and the effect was cumulative with propagation distance when the fundamental Lamb wave mode and the double-frequency Lamb wave mode had the same phase velocities. The present results may be important in the development of a new method to evaluate the status of long bones using the cumulative second harmonic of ultrasonic Lamb waves.

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

    PubMed

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

    2015-12-28

    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.

  11. 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.

    2015-09-01

    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.

  12. Nonlinear Raman-Nath second harmonic generation of hybrid structured fundamental wave.

    PubMed

    Zhou, Huaqing; Liu, Haigang; Sang, Minghuang; Li, Jun; Chen, Xianfeng

    2017-02-20

    We numerically and experimentally investigated the nonlinear Raman-Nath second harmonic generation of hybrid structured fundamental wave whose phase modulation combined periodic and random structure. The second harmonic generation of both one- and two-dimensional hybrid structured fundamental wave were investigated in this paper. The results show that more diffraction spots can be obtained in these hybrid structures than the pure periodic modulation cases. Besides, the total intensity of the second harmonic not only can be dramatically enhanced without altering the diffraction angles, but also is increasing with the degree of randomness of the structure. This study enriches the family of second harmonic generation of structured fundamental wave and has potential application in dynamically controlling second harmonic wave in arbitrary directions.

  13. Filamentation effects and second-harmonic spectra in laser-produced plasmas

    SciTech Connect

    Khalfaoui, A.H.; Abdelli, S.; Kerdja, T.; Ghobrini, D. )

    1993-08-01

    Sideway scattered second-harmonic spectra emitted from a 1064-nm-laser-produced plasma have been observed to originate from nonlinear coupling near the critical surface. The time evolution of the second-harmonic optical density confirmed the possibility that a plasmon issued from the resonant absorption of the incident beam can recombine with a photon ([omega][sub 0]) to give a transverse wave of frequency 2[omega][sub 0]. A plasmon issued from a parametric decay instability may also, by coalescence with an incident photon, give a transverse wave at a shifted second-harmonic frequency. The threshold of such a combination is determined. Moreover, irregular plasma-parameter variations and the perturbed spatial uniformity of the incident beam appear to alter the second-harmonic spectra. An oscillatory structure of the optical density of the observed second harmonic is interpreted as a result of the coupling physics involved and of laser-beam filamentation.

  14. 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.

    2016-05-01

    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.

  15. Anisotropic Second Harmonic Generation at Single Crystal Metal Surfaces.

    NASA Astrophysics Data System (ADS)

    Kexiang, He.

    The work in this thesis comprises a set of experiments designed to study the anisotropic spatial dependence of second harmonic generation (SHG) from the surface of single crystal metals. The anisotropic dependence of reflected SHG from Al_2O_3 Al(111) interface was studied. The isotropic dependence of the SHG signal is used to probe the structural symmetry of the Al_2O_3Al(111) interface. For P- and S-polarized laser light incident at a fixed angle of 45^circ, the intensities of S- and P-polarized components of SHG signal were measured as a function of rotation angle during rotation of the surface about its normal. Anisotropic SHG studies were also performed on high Miller index surface of Al(331) and on a Al surface cut at 22.5^ circ with respect to the Al(111) surface. For the Al(331) surface, the anisotropic dependence of the SHG signal was measured for both the S- and P-polarized signals under both S- and P-polarized laser excitation. The anisotropy of the SHG from Al(331) were fit with theory using the assumption that symmetry is retained for this surface at the metal oxide-metal interface. Existing theory is used to derive the theoretical expressions predicting the anisotropic dependence of SHG from Al(331). The SHG probe was also used to follow pulsed laser annealing (PLA) of the Al_2O_3/Al(111) interface from on a chemically polished Al(111) surface. Using P-polarized pump laser light, the P-polarized SHG signal exhibits three equally spaced, equal intensity maxima during a single complete rotation of Al_2O _3/Al(111) interface about the interface normal. Annealing of the interface is found to occur when the P-polarized 1064nm pump laser light has an incident peak power of 11 times 10 ^6W/cm^2 per pulse. The intensity of the P-polarized 532nm SHG signal generated in reflection from this annealed interface exhibits a reduced anisotropic component in the SHG signal. Measurements of the anisotropic SHG signal from ionized beam deposited Al thin-films on Si(111

  16. 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

  17. On second harmonic generation and multiphoton-absorption induced luminescence from laser-reshaped silver nanoparticles embedded in glass.

    PubMed

    Zolotovskaya, S A; Tyrk, M A; Stalmashonak, A; Gillespie, W A; Abdolvand, A

    2016-10-28

    Spherical silver nanoparticles (NPs) of 30 nm diameter embedded in soda-lime glass were uniformly reshaped (elongated) after irradiation by a linearly polarised 250 fs pulsed laser operating within the NPs' surface plasmon resonance band. We observed second harmonic generation (SHG) and multiphoton-absorption-induced luminescence (MAIL) in the embedded laser-reshaped NPs upon picosecond (10 ps) pulsed laser excitation at 1064 nm. A complementary study of SHG and MAIL was conducted in soda-lime glass containing embedded, mechanically-reshaped silver NPs of a similar elongation ratio (aspect ratio) to the laser-reshaped NPs. This supports the notion that the observed difference in SHG and MAIL in the studied nanocomposite systems is due to the shape modification mechanism. The discrete dipole approximation method was used to assess the absorption and scattering cross-sections of the reshaped NPs with different elongation ratios.

  18. On second harmonic generation and multiphoton-absorption induced luminescence from laser-reshaped silver nanoparticles embedded in glass

    NASA Astrophysics Data System (ADS)

    Zolotovskaya, S. A.; Tyrk, M. A.; Stalmashonak, A.; Gillespie, W. A.; Abdolvand, A.

    2016-10-01

    Spherical silver nanoparticles (NPs) of 30 nm diameter embedded in soda-lime glass were uniformly reshaped (elongated) after irradiation by a linearly polarised 250 fs pulsed laser operating within the NPs’ surface plasmon resonance band. We observed second harmonic generation (SHG) and multiphoton-absorption-induced luminescence (MAIL) in the embedded laser-reshaped NPs upon picosecond (10 ps) pulsed laser excitation at 1064 nm. A complementary study of SHG and MAIL was conducted in soda-lime glass containing embedded, mechanically-reshaped silver NPs of a similar elongation ratio (aspect ratio) to the laser-reshaped NPs. This supports the notion that the observed difference in SHG and MAIL in the studied nanocomposite systems is due to the shape modification mechanism. The discrete dipole approximation method was used to assess the absorption and scattering cross-sections of the reshaped NPs with different elongation ratios.

  19. Demonstration of second-harmonic IVUS feasibility with focused broadband miniature transducers.

    PubMed

    Chandrana, Chaitanya; Kharin, Nikolay; Vince, Geoffrey; Roy, Shuvo; Fleischman, Aaron

    2010-05-01

    Focused broadband miniature polyvinylidene fluoride-trifluoroethylene (PVDF TrFE) ultrasonic transducers were investigated for intravascular (IVUS) second-harmonic imaging. Modeling and experimental studies demonstrated that focused transducers, unlike conventional flat transducers, build up second harmonic peak pressures faster and stronger, leading to an increased SNR of second harmonic content within the coronary geometry. Experimental results demonstrated that focused second harmonic pressures could be controlled to occur at specific depths by controlling the f-number of the transducer. The experimental results were in good agreement with the modeled results. Experiments were conducted using three imaging modalities: fundamental 20 MHz (F20), second harmonic 40 MHz (H40), and fundamental 40 MHz (F40). The lateral resolutions for a 1-mm transducer (f-number 3.2) at F20, F40, and H40 were experimentally measured to be 162, 123, and 124 microm, respectively, which agreed well with the theoretical calculations with <8% error. Lateral resolution was further characterized in the three modes, using a micromachined phantom consisting of fixed bars and spaces with widths ranging from 20 to 160 microm. H40 exhibited better lateral resolution, clearly displaying 40- and 60-microm bars with about 4 dB and 7 dB greater signal strength compared with F20. Ex vivo human aorta images were obtained in the second-harmonic imaging mode to show the feasibility of high resolution second-harmonic IVUS using focused transducers.

  20. Surface second-harmonic generation from coupled spherical plasmonic nanoparticles: Eigenmode analysis and symmetry properties

    NASA Astrophysics Data System (ADS)

    Butet, Jérémy; Dutta-Gupta, Shourya; Martin, Olivier J. F.

    2014-06-01

    The surface second-harmonic generation from interacting spherical plasmonic nanoparticles building different clusters (symmetric and asymmetric dimers, trimers) is theoretically investigated. The plasmonic eigenmodes of the nanoparticle clusters are first determined using an ab initio approach based on the Green's functions method. This method provides the properties, such as the resonant wavelengths, of the modes sustained by a given cluster. The fundamental and second-harmonic responses of the corresponding clusters are then calculated using a surface integral method. The symmetry of both the linear and nonlinear responses is investigated, as well as their relationship. It is shown that the second-harmonic generation can be significantly enhanced when the fundamental field is such that its second harmonic matches modes with suitable symmetry. The role played by the nanogaps in second-harmonic generation is also underlined. The results presented in this article demonstrate that the properties of the second-harmonic generation from coupled metallic nanoparticles cannot be fully predicted from their linear response only, while, on the other hand, a detailed knowledge of the underlying modal structure can be used to optimize the generation of the second harmonic.

  1. Surface plasma wave assisted second harmonic generation of laser over a metal film

    SciTech Connect

    Chauhan, Santosh; Parashar, J.

    2015-01-15

    Second harmonic generation of laser mode converted surface plasma wave (SPW) over a corrugated metal film is studied. The laser, impinged on the metal film, under attenuated total reflection configuration, excites SPW over the metal–vacuum interface. The excited SPW extends over a much wider surface area than the laser spot cross-section. It exerts a second harmonic ponderomotive force on metal electrons, imparting them velocity that beats with the surface ripple to produce a nonlinear current, driving resonant second harmonic surface plasma wave.

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

    PubMed

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

    2016-07-01

    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.

  3. Negative electron energy loss and second-harmonic emission of nonlinear nanoparticles.

    PubMed

    Xu, Jinying; Zhang, Xiangdong

    2011-11-07

    A fast and general technique to investigation the interaction between a fast electron and nonlinear materials consisting of centrosymmetric spheres is presented by means of multiple scattering of electromagnetic multipole fields. Two kinds of new effect, the negative electron energy loss caused by the second-harmonic field and the second-harmonic Smith-Purcell radiation using finite chain of nonlinear spheres, are predicted for the first time. It is shown that these new effects can be probed by the electron energy loss spectrum, suggesting their possible applications in tunable light sources for the second-harmonic generation.

  4. 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.

    2007-04-30

    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.

  5. Analysis of second harmonic instability for the Chateauguay HVDC/SVC scheme

    SciTech Connect

    Hammad, A.E. )

    1992-01-01

    The Chateauguay HVDC back-to-back scheme with interconnections to the 765 kV transmission to U.S.A. and to Beauharnois generators can exhibit, under certain operating conditions, second harmonic resonance problems. This paper presents a thorough analysis of the problem using an eigenvalue and frequency domain approach. The analysis explains the mechanism of exciting the second harmonic instability by the presence of HVDC converters. The influence of changing the control parameters of the static VAR compensatory at the Chateauguay terminal is also studied. Finally, an assessment is made for the effectiveness of present countermeasure schemes, namely; the auxiliary dc stabilizing controls and the installation of second harmonic filters.

  6. Theoretical study on second-harmonic generation in two-dimensional nonlinear photonic crystals.

    PubMed

    Wang, Xiangnan; Zhao, Xiaohui; Zheng, Yuanlin; Chen, Xianfeng

    2017-01-20

    We theoretically study second-harmonic generation in two-dimensional nonlinear photonic crystals and obtain a unified expression that combines nonlinear Raman-Nath diffraction, Čerenkov-type second-harmonic generation, and nonlinear Bragg diffraction. The analytical solution is deduced, and the theoretical result coincides well with the nonlinear Raman-Nath, nonlinear Čerenkov, and nonlinear Bragg diffraction phase-matching conditions. This method has potential applications in second-harmonic generation of more complicated two-dimensional and even three-dimensional nonlinear photonic crystals.

  7. Nonlinear Raman-Nath second harmonic generation with structured fundamental wave.

    PubMed

    Liu, Haigang; Li, Jun; Zhao, Xiaohui; Zheng, Yuanlin; Chen, Xianfeng

    2016-07-11

    We proposed and experimentally demonstrated that nonlinear Raman-Nath second harmonic can be achieved in real time when a fundamental wave with the phase periodically modulated, termed as structured fundamental wave, incident in a homogeneous nonlinear medium. The diffraction of second harmonic originates from the structured fundamental wave, rather than the grating of a nonlinear photonic crystal. Nonlinear second harmonic generation, in forms of both one- and two-dimensional, was investigated in our experiment. This method circumvents the limitation of nonlinear photonic crystals in some extend and has potential applications in nonlinear frequency conversion, optical signal processing and beam shaping, etc.

  8. Role of antenna modes and field enhancement in second harmonic generation from dipole nanoantennas.

    PubMed

    de Ceglia, Domenico; Vincenti, Maria Antonietta; De Angelis, Costantino; Locatelli, Andrea; Haus, Joseph W; Scalora, Michael

    2015-01-26

    We study optical second harmonic generation from metallic dipole antennas with narrow gaps. Enhancement of the fundamental-frequency field in the gap region plays a marginal role on conversion efficiency. In the symmetric configuration, i.e., with the gap located at the center of the antenna axis, reducing gap size induces a significant red-shift of the maximum conversion efficiency peak. Either enhancement or inhibition of second-harmonic emission may be observed as gap size is decreased, depending on the antenna mode excited at the harmonic frequency. The second-harmonic signal is extremely sensitive to the asymmetry introduced by gap's displacements with respect to the antenna center. In this situation, second-harmonic light can couple to all the available antenna modes. We perform a multipolar analysis that allows engineering the far-field SH emission and find that the interaction with quasi-odd-symmetry modes generates radiation patterns with a strong dipolar component.

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

    SciTech Connect

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

    2005-01-01

    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.

  10. 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.

    1989-01-01

    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.

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

    PubMed

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

    2016-03-01

    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.

  12. Determination of collagen fibril size via absolute measurements of second-harmonic generation signals.

    PubMed

    Bancelin, Stéphane; Aimé, Carole; Gusachenko, Ivan; Kowalczuk, Laura; Latour, Gaël; Coradin, Thibaud; Schanne-Klein, Marie-Claire

    2014-09-16

    The quantification of collagen fibril size is a major issue for the investigation of pathological disorders associated with structural defects of the extracellular matrix. Second-harmonic generation microscopy is a powerful technique to characterize the macromolecular organization of collagen in unstained biological tissues. Nevertheless, due to the complex coherent building of this nonlinear optical signal, it has never been used to measure fibril diameter so far. Here we report absolute measurements of second-harmonic signals from isolated fibrils down to 30 nm diameter, via implementation of correlative second-harmonic-electron microscopy. Moreover, using analytical and numerical calculations, we demonstrate that the high sensitivity of this technique originates from the parallel alignment of collagen triple helices within fibrils and the subsequent constructive interferences of second-harmonic radiations. Finally, we use these absolute measurements as a calibration for ex vivo quantification of fibril diameter in the Descemet's membrane of a diabetic rat cornea.

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

    PubMed

    Trolle, Mads Lund; Pedersen, Thomas Garm

    2013-08-14

    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.

  14. Determination of collagen fibril size via absolute measurements of second-harmonic generation signals

    NASA Astrophysics Data System (ADS)

    Bancelin, Stéphane; Aimé, Carole; Gusachenko, Ivan; Kowalczuk, Laura; Latour, Gaël; Coradin, Thibaud; Schanne-Klein, Marie-Claire

    2014-09-01

    The quantification of collagen fibril size is a major issue for the investigation of pathological disorders associated with structural defects of the extracellular matrix. Second-harmonic generation microscopy is a powerful technique to characterize the macromolecular organization of collagen in unstained biological tissues. Nevertheless, due to the complex coherent building of this nonlinear optical signal, it has never been used to measure fibril diameter so far. Here we report absolute measurements of second-harmonic signals from isolated fibrils down to 30 nm diameter, via implementation of correlative second-harmonic-electron microscopy. Moreover, using analytical and numerical calculations, we demonstrate that the high sensitivity of this technique originates from the parallel alignment of collagen triple helices within fibrils and the subsequent constructive interferences of second-harmonic radiations. Finally, we use these absolute measurements as a calibration for ex vivo quantification of fibril diameter in the Descemet’s membrane of a diabetic rat cornea.

  15. 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.

    1991-01-01

    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.

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

    DOEpatents

    Salafsky, Joshua S.; Eisenthal, Kenneth B.

    2005-10-11

    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.

  17. Second-harmonic generation in single-mode integrated waveguides based on mode-shape modulation

    NASA Astrophysics Data System (ADS)

    Rao, Ashutosh; Chiles, Jeff; Khan, Saeed; Toroghi, Seyfollah; Malinowski, Marcin; Camacho-González, Guillermo Fernando; Fathpour, Sasan

    2017-03-01

    Second-harmonic generation is demonstrated using grating-assisted quasi-phase matching, based on waveguide-width modulation or mode-shape modulation. Applicable to any thin-film integrated second-order nonlinear waveguide, the technique is demonstrated in compact lithium niobate ridge waveguides. Fabricated devices are characterized with pulsed-pumping in the near-infrared, showing second-harmonic generation at a signal wavelength of 784 nm and propagation loss of 1 dB/cm.

  18. Impedance matching in photonic crystal microcavities for second-harmonic generation.

    PubMed

    Di Falco, Andrea; Conti, Claudio; Assanto, Gaetano

    2006-01-15

    By numerically integrating the three-dimensional Maxwell equations in the time domain with reference to a dispersive quadratically nonlinear material, we study second-harmonic generation in planar photonic crystal microresonators. The proposed scheme allows efficient coupling of the pump radiation to the defect resonant mode. The outcoupled generated second harmonic is maximized by impedance matching the photonic crystal cavity to the output waveguide.

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

    PubMed

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

    2010-05-12

    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.

  20. Extracavity and external cavity second-harmonic generation in a periodically poled silica fibre

    NASA Astrophysics Data System (ADS)

    Dontsova, E. I.; Kablukov, S. I.; Lobach, I. A.; Dostovalov, A. V.; Babin, S. A.; Gladyshev, A. V.; Dianov, E. M.; Corbary, C.; Ibsen, M.; Kazansky, P. G.

    2016-11-01

    We have studied second-harmonic generation (SHG) of a cw single-frequency ytterbium-doped fibre laser, using a periodically poled silica fibre as a nonlinear medium for frequency conversion. All-fibre external cavity SHG has been investigated for the first time. A twofold increase in second-harmonic power in a fibre ring cavity has been demonstrated and possibilities of further optimising the fibre scheme have been analysed.

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

    NASA Astrophysics Data System (ADS)

    Gusachenko, Ivan; Schanne-Klein, Marie-Claire

    2013-11-01

    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.

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

    PubMed

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

    2016-03-01

    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.

  3. 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

    2016-03-01

    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.

  4. Type-I cascaded quadratic soliton compression in lithium niobate: Compressing femtosecond pulses from high-power fiber lasers

    SciTech Connect

    Bache, Morten; Wise, Frank W.

    2010-05-15

    The output pulses of a commercial high-power femtosecond fiber laser or amplifier are typically around 300-500 fs with wavelengths of approximately 1030 nm and tens of microjoules of pulse energy. Here, we present a numerical study of cascaded quadratic soliton compression of such pulses in LiNbO{sub 3} using second-harmonic generation in a type-I phase-matching configuration. We find that because of competing cubic material nonlinearities, compression can only occur in the nonstationary regime, where group-velocity-mismatch-induced Raman-like nonlocal effects prevent compression to less than 100 fs. However, the strong group-velocity dispersion implies that the pulses can achieve moderate compression to durations of less than 130 fs in available crystal lengths. Most of the pulse energy is conserved because the compression is moderate. The effects of diffraction and spatial walk-off are addressed, and in particular the latter could become an issue when compressing such long crystals (around 10 cm long). We finally show that the second harmonic contains a short pulse locked to the pump and a long multi-picosecond red-shifted detrimental component. The latter is caused by the nonlocal effects in the nonstationary regime, but because it is strongly red-shifted to a position that can be predicted, we show that it can be removed using a bandpass filter, leaving a visible component of less than 100 fs at {lambda}=515 nm with excellent pulse quality.

  5. Doubly resonant metallic nanostructure for high conversion efficiency of second harmonic generation.

    PubMed

    Park, Sinjeung; Hahn, Jae W; Lee, Jae Yong

    2012-02-27

    The recent discovery of strong nonlinear emission in metallic nanostructures has offered possibilities for realization of functional nano photonic devices. Here, we demonstrate a novel design of a plasmonic nano device for high conversion efficiency of second harmonic generation. A 4 × 4 bowtie aperture array is fabricated to have both plasmonic resonance for local field enhancement of the fundamental wave and Fabry-Pérot resonance for high transmission of second harmonic wave. Combining nano structures for exciting surface plasmon polariton and suppressing higher order diffraction and anti-reflection layer, we achieve a second harmonic conversion efficiency of 1.4 × 10(-8) that is nearly an order of magnitude larger than the results published in recent literatures. We also theoretically analyze evidences of the role of double resonances tuned to the fundamental wave and the second harmonic wave, resulting in the augmentation of second harmonic response approximately an order of magnitude greater than that without the help of the resonance.

  6. Effect of skew angle on second harmonic guided wave measurement in composite plates

    NASA Astrophysics Data System (ADS)

    Cho, Hwanjeong; Choi, Sungho; Lissenden, Cliff J.

    2017-02-01

    Waves propagating in anisotropic media are subject to skewing effects due to the media having directional wave speed dependence, which is characterized by slowness curves. Likewise, the generation of second harmonics is sensitive to micro-scale damage that is generally not detectable from linear features of ultrasonic waves. Here, the effect of skew angle on second harmonic guided wave measurement in a transversely isotropic lamina and a quasi-isotropic laminate are numerically studied. The strain energy density function for a nonlinear transversely isotropic material is formulated in terms of the Green-Lagrange strain invariants. The guided wave mode pairs for cumulative second harmonic generation in the plate are selected in accordance with the internal resonance criteria - i.e., phase matching and non-zero power flux. Moreover, the skew angle dispersion curves for the mode pairs are obtained from the semi-analytical finite element method using the derivative of the slowness curve. The skew angles of the primary and secondary wave modes are calculated and wave propagation simulations are carried out using COMSOL. Numerical simulations revealed that the effect of skew angle mismatch can be significant for second harmonic generation in anisotropic media. The importance of skew angle matching on cumulative second harmonic generation is emphasized and the accompanying issue of the selection of internally resonant mode pairs for both a unidirectional transversely isotropic lamina and a quasi-isotropic laminate is demonstrated.

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

    SciTech Connect

    Parvini, T. S.; Tehranchi, M. M. E-mail: teranchi@sbu.ac.ir; Hamidi, S. M. E-mail: teranchi@sbu.ac.ir; Sarkarati, S.

    2015-11-14

    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.

  8. Characteristics of second harmonic generation of Lamb waves in nonlinear elastic plates.

    PubMed

    Müller, Martin F; Kim, Jin-Yeon; Qu, Jianmin; Jacobs, Laurence J

    2010-04-01

    This paper investigates the characteristics of the second harmonic generation of Lamb waves in a plate with quadratic nonlinearity. Analytical asymptotic solutions to Lamb waves are first obtained through the use of a perturbation method. Then, based on a careful analysis of these asymptotic solutions, it is shown that the cross-modal generation of a symmetric second harmonic mode by an antisymmetric primary mode is possible. These solutions also demonstrate that modes showing internal resonance-nonzero power flux to the second harmonic mode, plus phase velocity matching-are most useful for measurements. In addition, when using finite wave packets, which is the case in most experimental measurements, group velocity matching is required for a cumulative increase in the second harmonic amplitude with propagation distance. Finally, five mode types (which are independent of material properties) that satisfy all three requirements for this cumulative increase in second harmonic amplitude-nonzero power flux, plus phase and group velocity matching-are identified. These results are important for the development of an experimental procedure to measure material nonlinearity with Lamb waves.

  9. Silencing and enhancement of second-harmonic generation in optical gap antennas.

    PubMed

    Berthelot, Johann; Bachelier, Guillaume; Song, Mingxia; Rai, Padmnabh; Colas des Francs, Gérard; Dereux, Alain; Bouhelier, Alexandre

    2012-05-07

    Amplifying local electromagnetic fields by engineering optical interactions between individual constituents of an optical antenna is considered fundamental for efficient nonlinear wavelength conversion in nanometer-scale devices. In contrast to this general statement we show that high field enhancement does not necessarily lead to an optimized nonlinear activity. In particular, we demonstrate that second-harmonic responses generated at strongly interacting optical gap antennas can be significantly suppressed. Numerical simulations are confirming silencing of second-harmonic in these coupled systems despite the existence of local field amplification. We then propose a simple approach to restore and amplify the second-harmonic signal by changing the manner in which electrically-connected optical antennas are interacting in the charge-transfer plasmon regime. Our observations provide critical design rules for realizing optimal structures that are essential for a broad variety of nonlinear surface-enhanced characterizations and for realizing the next generation of electrically-driven optical antennas.

  10. Second harmonic generation of Cosh-Gaussian laser beam in collisional plasma with nonlinear absorption

    NASA Astrophysics Data System (ADS)

    Singh, Navpreet; Gupta, Naveen; Singh, Arvinder

    2016-12-01

    This paper investigates second harmonic generation (SHG) of an intense Cosh-Gaussian (ChG) laser beam propagating through a preformed underdense collisional plasma with nonlinear absorption. Nonuniform heating of plasma electrons takes place due to the nonuniform irradiance of intensity along the wavefront of laser beam. This nonuniform heating of plasma leads to the self-focusing of the laser beam and thus produces strong density gradients in the transverse direction. The density gradients so generated excite an electron plasma wave (EPW) at pump frequency that interacts with the pump beam to produce its second harmonics. To envision the propagation dynamics of the ChG laser beam, moment theory in Wentzel-Kramers-Brillouin (W.K.B) approximation has been invoked. The effects of nonlinear absorption on self-focusing of the laser beam as well as on the conversion efficiency of its second harmonics have been theoretically investigated.

  11. Performance optimization of an external enhancement resonator for optical second-harmonic generation

    NASA Astrophysics Data System (ADS)

    Jurdik, E.; Hohlfeld, J.; van Etteger, A. F.; Toonen, A. J.; Meerts, W. L.; van Kempen, H.; Rasing, Th.

    2002-07-01

    We study the factors that ultimately limit the performance of an external enhancement resonator for optical second-harmonic generation (SHG). To describe the resonant SHG process we introduce a theoretical model that accounts for the intensity-dependent cavity loss that is due to harmonic generation and that also includes a realistic assumption about the shape and the frequency width of the laser mode. With the help of this model we optimized the performance of a doubling cavity based on a lithium triborate (LBO) crystal. This cavity was used for frequency doubling the output of a single-frequency titanium-doped sapphire laser at 850 nm. We were able to push the total second-harmonic conversion efficiency to 53% (a 1.54-W pump resulted in 820 mW of second-harmonic light), which to our knowledge is the best result ever reported for a LBO-based doubling cavity. , Laser-focused atomic deposition.

  12. High-resolution second-harmonic optical coherence tomography of collagen in rat-tail tendon

    NASA Astrophysics Data System (ADS)

    Jiang, Yi; Tomov, Ivan V.; Wang, Yimin; Chen, Zhongping

    2005-03-01

    A high-resolution second-harmonic optical coherence tomography (SH-OCT) system is demonstrated using a spectrum broadened femtosecond Ti :sapphire laser. An axial resolution of 4.2μm at the second-harmonic wave center wavelength of 400 nm has been achieved. Because the SH-OCT system uses the second-harmonic generation signals that strongly depend on the orientation, polarization, and local symmetry properties of chiral molecules, this technique provides unique contrast enhancement to conventional optical coherence tomography. The system is applied to image biological tissues of the rat-tail tendon. Highly organized collagen fibrils in the rat-tail tendon can be visualized in recorded images.

  13. Efficient second harmonic generation using nonlinear substrates patterned by nano-antenna arrays.

    PubMed

    Bar-Lev, Doron; Scheuer, Jacob

    2013-12-02

    We study theoretically various design considerations for efficient generation of second harmonic using a nonlinear substrate patterned with nano-antennas. The analysis is focused on a gap Bowtie nano-antenna array recessed in LiNbO₃ which is shown to be preferable over on surface structures due to field enhancement, field profile and linear and non-linear polarization considerations. In addition, we develop the nano-antenna counterpart of the Boyd-Klienmann model in order to analyze the impact of a Gaussian shaped fundamental beam on the generated second harmonic. Finally, we show that the dielectric properties of the substrate lead to preferable directions for the incident fundamental harmonic and the emission of the second harmonic. Our analyses lead to several design rules which can enhance second and high harmonic generation from nano-antennas arrays by several orders of magnitude.

  14. The second-harmonic generation susceptibility in semiparabolic quantum wells with applied electric field

    NASA Astrophysics Data System (ADS)

    Yuan, Jian-Hui; Zhang, Yan; Mo, Hua; Chen, Ni; Zhang, Zhihai

    2015-12-01

    The second-harmonic generation susceptibility in semiparabolic quantum wells with applied electric field is investigated theoretically. For the same topic studied by Zhang and Xie [Phys. Rev. B 68 (2003) 235315] [1], some new and reliable results are obtained by us. It is easily observed that the second harmonic generation susceptibility decreases and the blue shift of the resonance is induced with increasing of the frequencies of the confined potential. Moreover, a transition from a two-photon resonance to two single-photon resonances will appear adjusted by the frequencies of the confined potential. Similar results can also be obtained by controlling the applied electric field. Surprisingly, the second harmonic generation susceptibility is weakened in the presence of the electric field, which is in contrast to the conventional case. Finally, the resonant peak and its corresponding resonant energy are also taken into account.

  15. Three-dimensional tooth imaging using multiphoton and second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Chen, Min-Huey; Chen, Wei-Liang; Sun, Yen; Fwu, Peter Tramyeon; Lin, Ming-Gu; Dong, Chen-Yuan

    2007-02-01

    Detailed morphological and cellular information relating to the human tooth have traditionally been obtained through histological studies that required decalcification, staining, and fixation. With the recent invention of multiphoton microscopy, it has become possible to acquire high resolution images without histological procedures. Using an epiilluminated multiphoton microscope, we obtained two-photon excited autofluorescence and second harmonic generation (SHG) images of ex vivo human tooth. By combining these two imaging modalities we obtained submicron resolution images of the enamel, dentin, and the periodontal ligaments. The enamel emits endogenous two-photon autofluorescence. The structure of the dentin is visible from both the autofluorescence and second harmonic generation signals. The periodontal ligament composed mostly of collagen can be visualized by SHG imaging. We also constructed three dimensional images of the enamel, dentin, and periodontal ligament. The effectiveness of using multiphoton and second harmonic generation microscopy to obtain structural information of teeth suggest its potential use in dental diagnostics.

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

    DOE PAGES

    Yang, Sangmo; Okatan, Mahmut Baris; Paranthaman, Mariappan Parans; ...

    2014-11-14

    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

  17. Compression of ultra-short pulses due to cascaded second order nonlinearities in photonic bandgap structures

    NASA Astrophysics Data System (ADS)

    Joseph, Shereena; Shahid Khan, Mohd.; Hafiz, Aurangzeb Khurram

    2016-03-01

    The cascaded second order nonlinearities in a 1-D photonic bandgap structure (1-D PBG) in the spectral domain have been explored. A weak signal pulse operating at frequency of interest is seeded with a strong pulse operating at its second harmonic (SH) frequency. The interaction of both pulses in the periodic structure takes place with a particular phase mismatch condition. The intensity of SH pulse controls the propagation of signal pulse and the signal pulse exhibits pulse compression at particular input SH intensity. Considering the parameter for GaInP/InAlP PBG structure we have demonstrated pulse compression from 290 fs to 155 fs. The dependency of pulse compression on the structural parameters, group velocity mismatch, group velocity dispersion and input intensity of pump has also been explored.

  18. Analysis of second-harmonic generation by primary ultrasonic guided wave propagation in a piezoelectric plate.

    PubMed

    Deng, Mingxi; Xiang, Yanxun

    2015-08-01

    The effect of second-harmonic generation (SHG) by primary ultrasonic guided wave propagation is analyzed, where the nonlinear elastic, piezoelectric, and dielectric properties of the piezoelectric plate material are considered simultaneously. The formal solution of the corresponding second-harmonic displacement field is presented. Theoretical and numerical investigations clearly show that the SHG effect of primary guided wave propagation is highly sensitive to the electrical boundary conditions of the piezoelectric plate. The results obtained may provide a means through which the SHG efficiency of ultrasonic guided wave propagation can effectively be regulated by changing the electrical boundary conditions of the piezoelectric plate.

  19. Retrieving squeezing from classically noisy light in second-harmonic generation

    NASA Astrophysics Data System (ADS)

    Ralph, T. C.; White, A. G.

    1995-05-01

    We report the results of a study of the quantum noise properties of a squeezing system involving a three-level laser pumping two similar second-harmonic-generating crystals. We show that squeezing that has been obscured by intensity and phase noise from the pump laser may be retrieved by difference detection of both second-harmonic outputs. Similarly, the squeezed vacuum formed by combining the two outputs on a 50/50 beam splitter will be squeezed at frequencies that are classically noisy in the individual beams.

  20. Enhanced second harmonic generation in coupled semiconductor whispering gallery mode microresonators

    NASA Astrophysics Data System (ADS)

    Dumeige, Yannick

    2009-02-01

    It has been shown that doubly resonant microcavities can be used to obtain miniaturized parametric devices leading for example to efficient second-harmonic generation (SHG). First we will briefly recall the basic properties of SHG in III-V semiconductor whispering gallery mode microdisks or microrings. Then we will show theoretically that by coupling such microresonators and by using the artificial dispersion of a side-coupled integrated spaced sequence of resonators (SCISSOR) it is possible to adapt the Fresnel phase-matching technique to the case of highly confining waveguides or to enhance the second order nonlinear properties of a semiconductor waveguide by slowing fundamental and second-harmonic waves.

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

    PubMed

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

    2004-05-15

    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.

  2. Influence of Reflections on Frequency Tunability and Mode Competition in the Second-Harmonic THz Gyrotron

    NASA Astrophysics Data System (ADS)

    Khutoryan, Eduard M.; Idehara, Toshitaka; Melnikova, Maria M.; Ryskin, Nikita M.; Dumbrajs, Olgierd

    2017-03-01

    Effect of delayed reflection on operation of a second-harmonic terahertz (THz)-band gyrotron is studied. Theoretical analyses, numerical calculations, and experimental observations for the 0.394-THz Fukui University (FU) and continuous wave (CW) IIB gyrotron are presented. The reflections decrease starting current and expand frequency tunability range owing to excitation of high-order axial modes. They also increase frequency stability, i.e., reduce frequency change due to variation of the magnetic field. In addition, the reflections strongly affect mode competition causing suppress of the second-harmonic mode by the fundamental one and vice versa or, in the case of cooperative mode interaction, mutual power increase.

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

    PubMed

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

    2013-01-01

    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.

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

    PubMed

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

    2015-05-01

    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.

  5. Phase-matched second harmonic generation with on-chip GaN-on-Si microdisks

    NASA Astrophysics Data System (ADS)

    Roland, I.; Gromovyi, M.; Zeng, Y.; El Kurdi, M.; Sauvage, S.; Brimont, C.; Guillet, T.; Gayral, B.; Semond, F.; Duboz, J. Y.; de Micheli, M.; Checoury, X.; Boucaud, P.

    2016-09-01

    We demonstrate phase-matched second harmonic generation in gallium nitride on silicon microdisks. The microdisks are integrated with side-coupling bus waveguides in a two-dimensional photonic circuit. The second harmonic generation is excited with a continuous wave laser in the telecom band. By fabricating a series of microdisks with diameters varying by steps of 8 nm, we obtain a tuning of the whispering gallery mode resonances for the fundamental and harmonic waves. Phase matching is obtained when both resonances are matched with modes satisfying the conservation of orbital momentum, which leads to a pronounced enhancement of frequency conversion.

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

    SciTech Connect

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

    2001-09-03

    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.

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

    PubMed

    Quan, Li; Liu, Xiaozhou; Gong, Xiufen

    2012-10-01

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

  8. 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.

    2015-06-01

    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.

  9. 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

    2015-08-01

    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.

  10. The second harmonic generation in symmetrical and asymmetrical Gaussian potential quantum wells with applied electric field

    NASA Astrophysics Data System (ADS)

    Yuan, Jian-Hui; Chen, Ni; Mo, Hua; Zhang, Yan; Zhang, Zhi-Hai

    2015-12-01

    A detailed investigation of the second harmonic generation in symmetrical and asymmetrical Gaussian potential quantum wells under the influence of applied electric field by using the compact-density-matrix approach and the finite difference method. The results show that the second-harmonic generation susceptibility obtained in two cases can reach the magnitude of 10-4 m/V, which depend dramatically on the applied electric field and the structural parameters. Finally, the resonant peak and its corresponding to the resonant energy are also taken into account.

  11. Intense and tunable second-harmonic generation in biased bilayer graphene

    NASA Astrophysics Data System (ADS)

    Brun, Søren J.; Pedersen, Thomas G.

    2015-05-01

    The centrosymmetric two-dimensional material bilayer graphene (BLG) does not show dipole-allowed second-harmonic generation (SHG) in its pristine form. However, the symmetry can be broken by applying an electric field perpendicular to the layer. Here, we present a theoretical study of SHG from biased BLG. We show that the sheet second-harmonic susceptibility reaches very large values of several hundred nm2/V in the midinfrared region. The SHG is tunable depending on the strength of the electric field. Furthermore, a strong, tunable double resonance appears in the spectrum. We believe that this study could spark interest in the nonlinear optical properties of biased BLG.

  12. Efficient second harmonic generation in χ(2) profile reconfigured lithium niobate thin film

    NASA Astrophysics Data System (ADS)

    Cai, Lutong; Wang, Yiwen; Hu, Hui

    2017-03-01

    Second harmonic wave was efficiently generated in proton exchanged lithium niobate thin film channel waveguides. Modal dispersion phase matching was achieved between two guided modes at pump and second-harmonic wavelengths with the same polarization, enabling using the largest second-order nonlinear component d33. The χ(2) profile in the lithium niobate thin film was reconfigured by proton exchange, leading to significantly enhanced modal overlap integral between the interacting modes. Normalized conversion efficiency up to 48% W-1 cm-2 was achieved in experiments.

  13. Phase-matched second harmonic generation with on-chip GaN-on-Si microdisks

    PubMed Central

    Roland, I.; Gromovyi, M.; Zeng, Y.; El Kurdi, M.; Sauvage, S.; Brimont, C.; Guillet, T.; Gayral, B.; Semond, F.; Duboz, J. Y.; de Micheli, M.; Checoury, X.; Boucaud, P.

    2016-01-01

    We demonstrate phase-matched second harmonic generation in gallium nitride on silicon microdisks. The microdisks are integrated with side-coupling bus waveguides in a two-dimensional photonic circuit. The second harmonic generation is excited with a continuous wave laser in the telecom band. By fabricating a series of microdisks with diameters varying by steps of 8 nm, we obtain a tuning of the whispering gallery mode resonances for the fundamental and harmonic waves. Phase matching is obtained when both resonances are matched with modes satisfying the conservation of orbital momentum, which leads to a pronounced enhancement of frequency conversion. PMID:27687007

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

    SciTech Connect

    Jha, Pallavi; Agrawal, Ekta

    2014-05-15

    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.

  15. X-ray production and second-harmonic generation during femtosecond laser microdrilling

    NASA Astrophysics Data System (ADS)

    Gordienko, V. M.; Zhvaniya, I. A.; Makarov, I. A.

    2015-08-01

    We investigated X-ray yield and second-harmonic generation during femtosecond laser drilling of solid targets placed in vacuum or air. Laser pulse intensity was about 1016 W/cm2 and repetition rate was 10 Hz. Hard X-ray yield ( E > 2.5 keV) and second-harmonic signal are non-monotone and reach a maximum during formation of microchannel in a target. That indicates that both signals can be utilized as a feedback for monitoring laser energy deposition to the target under laser microdrilling. Spectrum of second harmonic emitted from laser-drilled microchannel is blueshifted regardless of target type or environment (vacuum or air surrounding the target). The blueshift reaches the value of about 30 nm. The spectrum of fundamental radiation backreflected from the microchannel has also corresponding blueshift. This testifies that the cloud of ablated particles accumulates inside the microchannel. Incident laser radiation undergoes self-action inside the cloud, as a result occurs the spectral modification of incident radiation and its second harmonic.

  16. Enhanced second harmonic generation by photonic-plasmonic Fano-type coupling in nanoplasmonic arrays.

    PubMed

    Walsh, Gary F; Dal Negro, Luca

    2013-07-10

    In this communication, we systematically investigate the effects of Fano-type coupling between long-range photonic resonances and localized surface plasmons on the second harmonic generation from periodic arrays of Au nanoparticles arranged in monomer and dimer geometries. Specifically, by scanning the wavelength of an ultrafast tunable pump laser over a large range, we measure the second harmonic excitation spectra of these arrays and demonstrate their tunability with particle size and separation. Moreover, through a comparison with linear optical transmission spectra, which feature asymmetric Fano-type lineshapes, we demonstrate that the second harmonic generation is enhanced when coupled photonic-plasmonic resonances of the arrays are excited at the fundamental pump wavelength, thus boosting the intensity of the electromagnetic near-fields. Our experimental results, which are supported by numerical simulations of linear optical transmission and near-field enhancement spectra based on the Finite Difference Time Domain method, demonstrate a direct correlation between the onset of Fano-type coupling and the enhancement of second harmonic generation in arrays of Au nanoparticles. Our findings enable the engineering of the nonlinear optical response of Fano-type coupled nanoparticle arrays that are relevant to a number of device applications in nonlinear nano-optics and plasmonics, such as on-chip frequency generators, modulators, switchers, and sensors.

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

    PubMed

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

    2015-09-02

    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.

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

    PubMed

    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

    2015-05-01

    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.

  19. Comparison of fundamental, second harmonic, and superharmonic imaging: a simulation study.

    PubMed

    van Neer, Paul L M J; Danilouchkine, Mikhail G; Verweij, Martin D; Demi, Libertario; Voormolen, Marco M; van der Steen, Anton F W; de Jong, Nico

    2011-11-01

    In medical ultrasound, fundamental imaging (FI) uses the reflected echoes from the same spectral band as that of the emitted pulse. The transmission frequency determines the trade-off between penetration depth and spatial resolution. Tissue harmonic imaging (THI) employs the second harmonic of the emitted frequency band to construct images. Recently, superharmonic imaging (SHI) has been introduced, which uses the third to the fifth (super) harmonics. The harmonic level is determined by two competing phenomena: nonlinear propagation and frequency dependent attenuation. Thus, the transmission frequency yielding the optimal trade-off between the spatial resolution and the penetration depth differs for THI and SHI. This paper quantitatively compares the concepts of fundamental, second harmonic, and superharmonic echocardiography at their optimal transmission frequencies. Forward propagation is modeled using a 3D-KZK implementation and the iterative nonlinear contrast source (INCS) method. Backpropagation is assumed to be linear. Results show that the fundamental lateral beamwidth is the narrowest at focus, while the superharmonic one is narrower outside the focus. The lateral superharmonic roll-off exceeds the fundamental and second harmonic roll-off. Also, the axial resolution of SHI exceeds that of FI and THI. The far-field pulse-echo superharmonic pressure is lower than that of the fundamental and second harmonic. SHI appears suited for echocardiography and is expected to improve its image quality at the cost of a slight reduction in depth-of-field.

  20. Second-Harmonic Scattering as a Probe of Structural Correlations in Liquids.

    PubMed

    Tocci, Gabriele; Liang, Chungwen; Wilkins, David M; Roke, Sylvie; Ceriotti, Michele

    2016-11-03

    Second-harmonic scattering experiments of water and other bulk molecular liquids have long been assumed to be insensitive to interactions between the molecules. The measured intensity is generally thought to arise from incoherent scattering due to individual molecules. We introduce a method to compute the second-harmonic scattering pattern of molecular liquids directly from atomistic computer simulations, which takes into account the coherent terms. We apply this approach to large-scale molecular dynamics simulations of liquid water, where we show that nanosecond second-harmonic scattering experiments contain a coherent contribution arising from radial and angular correlations on a length scale of ≲1 nm, much shorter than had been recently hypothesized ( Shelton , D. P. J. Chem. Phys. 2014 , 141 ). By combining structural correlations from simulations with experimental data ( Shelton , D. P. J. Chem. Phys. 2014 , 141 ), we can also extract an effective molecular hyperpolarizability in the liquid phase. This work demonstrates that second-harmonic scattering experiments and atomistic simulations can be used in synergy to investigate the structure of complex liquids, solutions, and biomembranes, including the intrinsic intermolecular correlations.

  1. 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.

    1973-01-01

    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.

  2. Second harmonic generation from patterned GaAs inside a subwavelength metallic hole array

    NASA Astrophysics Data System (ADS)

    Fan, Wenjun; Zhang, Shuang; Malloy, K. J.; Brueck, S. R. J.; Panoiu, N. C.; Osgood, R. M.

    2006-10-01

    By extending GaAs dielectric posts with a large second-order nonlinear susceptibility through the holes of a subwavelength metallic hole array coupled to the metal surface-plasma wave, strong second harmonic (SH) signal is observed. The SH signal is strengthened as a result of the enhanced electromagnetic fields inside the hole apertures.

  3. 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

    2014-03-31

    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.

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

    SciTech Connect

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

    2016-03-31

    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. (lasers)

  5. Improved quantification of collagen anisotropy with polarization-resolved second harmonic generation microscopy.

    PubMed

    Hristu, Radu; Stanciu, Stefan G; Tranca, Denis E; Stanciu, George A

    2016-10-24

    Imaging tissue samples by polarization-resolved second harmonic generation microscopy provides both qualitative and quantitative insights into collagen organization in a label-free manner. Polarization-resolved second harmonic generation microscopy goes beyond simple intensity-based imaging by adding the laser beam polarization component and applying different quantitative metrics such as the anisotropy factor. It thus provides valuable information on collagen arrangement not available with intensity measurements alone. Current established approaches are limited to calculating the anisotropy factor for only a particular laser beam polarization and no general guidelines on how to select the best laser beam polarization have yet been defined. Here, we introduce a novel methodology for selecting the optimal laser beam polarization for characterizing tissues using the anisotropy in the purpose of identifying cancer signatures. We show that the anisotropy factor exhibits a similar laser beam polarization dependence to the second harmonic intensity and we combine it with the collagen orientation index computed by Fast Fourier Transform analysis of the recorded images to establish a framework for choosing the laser beam polarization that is optimal for an accurate interpretation of polarization-resolved second harmonic generation microscopy images and anisotropy maps, and hence a better differentiation between healthy and dysplastic areas. SHG image of skin tissue (a) and a selected area of interest for which we compute the SHG intensity (b) and anisotropy factor (c) dependence on the laser beam polarization and also the FFT spectrum (d) to evaluate the collagen orientation index.

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

    SciTech Connect

    Purohit, Gunjan Rawat, Priyanka; Gauniyal, Rakhi

    2016-01-15

    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.

  7. Experimental demonstration of linear precompensation of a nonlinear transfer function due to second-harmonic generation.

    PubMed

    Vidal, Sébastien; Luce, Jacques; Penninckx, Denis

    2011-01-01

    We report on what we believe is the first experimental demonstration of the linear precompensation of a nonlinear transfer function due to frequency conversion. As a proof of principle, we show the effective precompensation with an interferometric filter of FM-to-AM conversion due to second-harmonic generation in a potassium titanyl phosphate crystal.

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

    SciTech Connect

    Olsen, M.K.

    2004-09-01

    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.

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

    PubMed

    Williams, Justin C; Campagnola, Paul J

    2015-12-16

    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.

  10. Investigation of second harmonic generation in glutamic acid-metal complexes

    SciTech Connect

    Cooper, T.M.; Cline, S.M.; Zelmon, D.E.; Vuppuladhadium, R.; Gupta, S.D.; Ramabadran, U.B.

    1996-12-31

    To design new second order nonlinear crystals, the authors have characterized a series of dipeptide complexes and copper glutamate. They tested 16 materials using powder second harmonic generation. The best of these materials was copper glutamate. Results of initial nonlinear optical characterization of the copper glutamate powder determined by the Kurtz powder test are presented.

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

    SciTech Connect

    Keicher, D.M.

    1994-01-01

    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. Homoclinic orbits and chaos in a second-harmonic generating optical cavity

    SciTech Connect

    Holm, D.; Kovacic, G., Timofeyev, I.

    1997-04-01

    We present two large families of Silnikov-type homoclinic orbits in a two mode-model that describes second-harmonic generation in a passive optical cavity. These families of homoclinic orbits give rise to chaotic dynamics in the model. 4 refs., 1 fig.

  13. 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

    2016-01-01

    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.

  14. Effect of Laser Beam Filamentation on Second Harmonic Spectrum in Laser Plasma Interaction

    NASA Astrophysics Data System (ADS)

    Sharma, Prerana; Sharma, R. P.

    2009-11-01

    This paper presents the laser beam filamentation at ultra relativistic laser powers, when the restriction on the beam is relaxed during filamentation process. On account of laser beam intensity gradient and background density gradients in filamentary regions the electron plasma wave (epw) at pump wave frequency is generated, this epw is found to be highly localized on account of the laser beam filaments. Interaction of incident laser beam with these epw leads to second harmonic generation. The second harmonic spectrum has also been studied in detail and its correlation with the filamentation of the laser beam has been established. Starting almost with a monochromatic component of laser beam propagation, the second harmonic spectrum becomes more complicated and broadened as the laser beam propagates further, and filamentation takes place. For the typical laser beam and plasma parameters: λ0= 1064 nm, power flux (10^22 W/cm^2),φp=0.03φ0, vth=0.1c, n0=1.9x10^19. We found that conversion efficiency comes out to be (E2/E0) = 8x10-3, and the spectrum is quite broad which depends upon the laser beam propagation distance. The results (specifically, second harmonic spectral feature) presented here may be used for the diagnostics of laser produced plasmas.

  15. 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

    2015-05-01

    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.

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

    SciTech Connect

    Petrov, Dmitri

    2010-09-15

    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.

  17. 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

    2007-02-01

    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.

  18. 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. |

    1995-12-31

    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.

  19. A study of electric-field-induced second-harmonic generation in asymmetrical Gaussian potential quantum wells

    NASA Astrophysics Data System (ADS)

    Zhai, Wangjian

    2014-12-01

    Electric-field-induced second-harmonic generation in asymmetrical Gaussian potential quantum wells is investigated using the effective mass approximation employing the compact density matrix method and the iterative approach. Our results show that the absolute value, the real part and the imaginary part of second-harmonic generation are greatly affected by the height of the Gaussian potential quantum wells, the range of the Gaussian confinement potential and the applied electric field. The relationship between the absolute value and the imaginary part of second-harmonic generation together with the relationship between the absolute value and the real part of second-harmonic generation is studied. It is found that no matter how the height of the Gaussian potential quantum wells, the range of the Gaussian confinement potential and the applied electric field vary, the resonant peaks of the absolute value of second-harmonic generation do not originate from the imaginary part but from the real part.

  20. Self-Phase-Matched Second-Harmonic and White-Light Generation in a Biaxial Zinc Tungstate Single Crystal

    PubMed Central

    Osewski, Pawel; Belardini, Alessandro; Petronijevic, Emilija; Centini, Marco; Leahu, Grigore; Diduszko, Ryszard; Pawlak, Dorota A.; Sibilia, Concita

    2017-01-01

    Second-order nonlinear optical materials are used to generate new frequencies by exploiting second-harmonic generation (SHG), a phenomenon where a nonlinear material generates light at double the optical frequency of the input beam. Maximum SHG is achieved when the pump and the generated waves are in phase, for example through birefringence in uniaxial crystals. However, applying these materials usually requires a complicated cutting procedure to yield a crystal with a particular orientation. Here we demonstrate the first example of phase matching under the normal incidence of SHG in a biaxial monoclinic single crystal of zinc tungstate. The crystal was grown by the micro-pulling-down method with the (102) plane perpendicular to the growth direction. Additionally, at the same time white light was generated as a result of stimulated Raman scattering and multiphoton luminescence induced by higher-order effects such as three-photon luminescence enhanced by cascaded third-harmonic generation. The annealed crystal offers SHG intensities approximately four times larger than the as grown one; optimized growth and annealing conditions may lead to much higher SHG intensities. PMID:28338074

  1. Self-Phase-Matched Second-Harmonic and White-Light Generation in a Biaxial Zinc Tungstate Single Crystal

    NASA Astrophysics Data System (ADS)

    Osewski, Pawel; Belardini, Alessandro; Petronijevic, Emilija; Centini, Marco; Leahu, Grigore; Diduszko, Ryszard; Pawlak, Dorota A.; Sibilia, Concita

    2017-03-01

    Second-order nonlinear optical materials are used to generate new frequencies by exploiting second-harmonic generation (SHG), a phenomenon where a nonlinear material generates light at double the optical frequency of the input beam. Maximum SHG is achieved when the pump and the generated waves are in phase, for example through birefringence in uniaxial crystals. However, applying these materials usually requires a complicated cutting procedure to yield a crystal with a particular orientation. Here we demonstrate the first example of phase matching under the normal incidence of SHG in a biaxial monoclinic single crystal of zinc tungstate. The crystal was grown by the micro-pulling-down method with the (102) plane perpendicular to the growth direction. Additionally, at the same time white light was generated as a result of stimulated Raman scattering and multiphoton luminescence induced by higher-order effects such as three-photon luminescence enhanced by cascaded third-harmonic generation. The annealed crystal offers SHG intensities approximately four times larger than the as grown one; optimized growth and annealing conditions may lead to much higher SHG intensities.

  2. In-phased second harmonic wave array generation with intra-Talbot-cavity frequency-doubling.

    PubMed

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

    2015-03-23

    The Talbot cavity is one promising method to synchronize the phase of a laser array. However, it does not achieve the lowest array mode with the same phase but the highest array mode with the anti-phase between every two adjacent lasers, which is called out-phase locking. Consequently, their far-field images exhibit 2-peak profiles. We propose intra-Talbot-cavity frequency-doubling. By placing a nonlinear crystal in a Talbot cavity, the Talbot cavity generates an out-phased fundamental wave array, which is converted into an in-phase-locked second harmonic wave array at the nonlinear crystal. We demonstrate numerical calculations and experiments on intra-Talbot-cavity frequency-doubling and obtain an in-phase-locked second harmonic wave array for a Nd:YVO₄ array laser.

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

    DOEpatents

    Boyd, Gary T.; Shen, Yuen-Ron

    1989-01-01

    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.

  4. Second harmonic generation in three-dimensional structures based on homogeneous centrosymmetric metallic spheres.

    PubMed

    Xu, Jinying; Zhang, Xiangdong

    2012-01-16

    The theory of second harmonic generation (SHG) in three-dimensional structures consisting of arbitrary distributions of metallic spheres made of centrosymmetric materials is developed by means of multiple scattering of electromagnetic multipole fields. The electromagnetic field at both the fundamental frequency and second harmonic, as well as the scattering cross section, are calculated in a series of particular cases such as a single metallic sphere, two metallic spheres, chains of metallic spheres, and other distributions of the metallic spheres. It is shown that the linear and nonlinear optical response of all ensembles of metallic spheres is strongly influenced by the excitation of localized surface plasmon-polariton resonances. The physical origin for such a phenomenon has also been analyzed.

  5. Stimulated Brillouin scattering at the second harmonic of a laser in two-ion-species plasma

    NASA Astrophysics Data System (ADS)

    Yadav, Sushila; Kaur, Sukhdeep; Tripathi, V. K.

    2008-12-01

    A high power laser (ω0, k0), propagating through a two-ion-species plasma, produces oscillatory electron velocity at the second harmonic due to V×B force. This velocity parametrically couples an ion acoustic wave (ω, k) and a scattered electromagnetic wave (ω1, k1), where ω1=ω-2ω0, k1=k-2k0 causing second harmonic Brillouin scattering. The growth rate, far above the threshold, scales linearly with laser intensity. It has maximum growth rate slightly tilted to side scattering and vanishes for back scattering. The presence of light ion species introduces linear damping on the ion mode, diminishing the growth rate of the parametric instability.

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

    PubMed

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

    2016-09-21

    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.

  7. 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

    2013-07-15

    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.

  8. 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

    2006-02-01

    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.

  9. Monitoring of collagen shrinkage by use of second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

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

    2006-02-01

    Thermal treatment induced collagen shrinkage has a great number of applications in medical practice. Clinically, the there is lack of reliable non-invasive methods to quantify the shrinkage. Overt treatment by heat application can lead to devastating results. We investigate the serial changes of collagen shrinkage by thermal treatment of rat tail tendons. The change in length is correlated with the finding in second harmonic generation microscopy and histology. Rat tail tendon shortens progressively during initial thermal treatment. After a certain point in time, the length then remains almost constant despite further thermal treatment. The intensity of second harmonic generation signals also progressively decreases initially and then remains merely detectable upon further thermal treatment. It prompts us to develop a mathematic model to quantify the dependence of collagen shrinkage on changes of SHG intensity. Our results show that SHG intensity can be used to predict the degree of collagen shrinkage during thermal treatment for biomedical applications.

  10. Far-field radiation patterns of second harmonic generation from gold nanoparticles under tightly focused illumination.

    PubMed

    Sun, Jingwei; Wang, Xianghui; Chang, Shengjiang; Zeng, Ming; Shen, Si; Zhang, Na

    2016-04-04

    We study far-field angular radiation patterns of second harmonic generation (SHG) from gold nanosphere, nanocube, nanorod, and nanocup illuminated by tightly focused linearly and radially polarized beams, respectively. It is found that under linearly polarized illumination, far-field forward-scattering SHG (FSHG) dominates second harmonic (SH) responses generated by those gold particles. On the contrary, it is amazing that significant backward-scattering SHG (BSHG) can be observed when those gold nanoparticles are excited by a focused radially polarized beam. For the case of gold nanosphere, the effective point dipole systems are developed to reasonably elucidate this interesting difference. Our investigations suggest that for SHG microscopy with backward detection scheme, tightly focused radially polarized beam could be a promising excitation field to improve the backward SH signal.

  11. Determine electric field directions at semiconductor surfaces by femtosecond frequency domain interferometric second harmonic (FDISH) generation

    NASA Astrophysics Data System (ADS)

    Nelson, C. A.; Zhu, X.-Y.

    2016-10-01

    Optical excitations at semiconductor surfaces or interfaces are accompanied by transient interfacial electric fields due to charge redistribution or transfer. While such transient fields may be probed by time-resolved second harmonic generation (TR-SHG), it is difficult to determine the field direction, which is invaluable to unveiling the underlying physics. Here we apply a time-resolved frequency domain interferometric second harmonic (TR-FDISH) generation technique to determine the phase relationship between the SH field emitted from bulk GaAs(1 0 0) and the transient SH field from the space charge region. The interference between these two SH fields allow us to unambiguously determine the directions of transient electric fields. Since SH fields from a static bulk contribution and a changing electric field contribution are present at most semiconductor surfaces or interfaces under optical excitation, the TR-FDISH technique is of general significance to probing the dynamics of interfacial charge transfer/redistribution.

  12. Investigating starch gelatinization through Stokes vector resolved second harmonic generation microscopy

    PubMed Central

    Mazumder, Nirmal; Xiang, Lu Yun; Qiu, Jianjun; Kao, Fu-Jen

    2017-01-01

    The changes of the morphology during heating and the degree of crystallinity of dry and hydrated starch granules are investigated using second harmonic generation (SHG) based Stokes polarimetry. A spatial distribution of various polarization parameters, such as the degree of polarization (DOP), the degree of linear polarization (DOLP), and the degree of circular polarization (DOCP) are extracted and compared with the two dimensional second harmonic (SH) Stokes images of starch granules. The SH signal from hydrated and dry starch on heating differed significantly in DOLP and DOCP values, indicating that hydrated starch has a greater degree of ultrastructural amylopectin disorder. The detail of denaturation and the phase transition of hydrated starch demonstrate the significant influence of thermal processing. PMID:28383522

  13. 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.

    2015-02-23

    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.

  14. 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

    2013-02-28

    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)

  15. 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.

    2015-12-21

    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.

  16. 2D Arrays of Hexagonal Plasmonic Necklaces for Enhanced Second Harmonic Generation.

    PubMed

    Gómez-Tornero, Alejandro; Tserkezis, Christos; Mateos, Luis; Bausá, Luisa E; Ramírez, Mariola O

    2017-02-10

    Hexagonal plasmonic necklaces of silver nanoparticles organized in 2D superlattices on functional ferroelectric templates are fabricated in large-scale spatial regions by using a surfactant-free photo-deposition process. The plasmonic necklaces support broad radiative plasmonic resonances allowing the enhancement of second harmonic generation (SHG) at the ferroelectric domain boundaries. A 400-fold SHG enhancement is achieved at the near-UV spectral region with subsequent interest for technological applications.

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

    PubMed

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

    2016-06-01

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

  18. Generation Of 369.4-Nanometers Second Harmonic From A Diode Laser

    NASA Technical Reports Server (NTRS)

    Williams, Angelyn P.; Maleki, Lutfollah

    1995-01-01

    Experimental laser system features polarization feedback scheme maintaining frequency lock. Generates light at wavelength of 369.4 nanometers by second-harmonic generation from 738.8-nanometers laser diode. System prototype of source of 369.4-nanometers radiation used to optically pump 2S1/2 ' 2P1/2 transition in 171Yb+ ions in lightweight, low-power trapped-ion frequency-standard apparatus.

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

    SciTech Connect

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

    2015-10-28

    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.

  20. Second harmonic generation in a low-loss orientation-patterned GaAs waveguide.

    PubMed

    Fedorova, K A; McRobbie, A D; Sokolovskii, G S; Schunemann, P G; Rafailov, E U

    2013-07-15

    The technology of low-loss orientation-patterned gallium arsenide (OP-GaAs) waveguided crystals was developed and realized by reduction of diffraction scattering on the waveguide pattern. The propagation losses in the OP-GaAs waveguide were estimated to be as low as 2.1 dB/cm, thus demonstrating the efficient second harmonic generation at 1621 nm under an external pumping.

  1. Near-field coupling and second-harmonic generation in split-ring resonator arrays

    NASA Astrophysics Data System (ADS)

    Grynko, Yevgen; Meier, Torsten; Linden, Stefan; Niesler, Fabian B. P.; Wegener, Martin; Förstner, Jens

    2012-09-01

    We simulate the linear and nonlinear optical response from split-ring resonator (SRR) arrays to study collective effects between the constituent SRRs that determine spectral properties of the second harmonic generation (SHG). We apply the Discontinuous Galerkin Time Domain (DGTD) method and the hydrodynamic Maxwell-Vlasov model to calculate the SHG emission. Our model is able to qualitatively reproduce and explain the non-monotonic dependence of the spectral SHG transmission measured experimentally for SRR arrays with different lattice constants [1].

  2. Highly Efficient Optical Second Harmonic Generation in Poled Ti-Doped Silica Glasses

    NASA Astrophysics Data System (ADS)

    Tanaka, Katsuhisa; Kashima, Kenichi; Hirao, Kazuyuki; Soga, Naohiro; Yamagata, Shigeru; Mito, Akihiro; Nasu, Hiroyuki

    1995-01-01

    Optical second harmonic intensity of poled Ti-doped silica glasses prepared by the Verneuil method has been measured. The second-order nonlinear coefficient, d33, of the glasses prepared from starting materials of TiO2 and SiO2 powders ranges from 0.2 to 0.5 pm/V. These values are one order of magnitude larger than that for silica glass without intentional dopants.

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

    PubMed

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

    2016-06-15

    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.

  4. Symmetry breaking in the second harmonic field of self-assembled metallic nanostructures

    NASA Astrophysics Data System (ADS)

    Belardini, A.; Benedetti, A.; Centini, M.; Fazio, E.; Bertolotti, M.; Sibilia, C.; Haus, Joseph W.; Sarangan, Andrew

    2015-05-01

    Here we present both an overview of different nonlinear optical phenomena occurring in nanopatterned materials and new results on the symmetry induced second harmonic generation (SHG) signal from metallic nanowires. A discussion about symmetry breaking in artificial chiral metamaterials is presented, while the experimental evidence was given by second order nonlinear optical measurements on different samples. Here, new SHG measurements on regular array of tilted nanowires (NWs) produced by grazing evaporating gold on a silicon substrate were presented and discussed. The surface composed by tilted wires can induce an optical chiral response of the whole sample when the light impinges on the sample on an out-of-normal incidence angle (extrinsic chirality). The measurements were performed by using circular polarised laser excitation at the wavelength of 800nm and by observing the second harmonic response at the wavelength of 400nm in different polarization states. The second harmonic generation process results to be very sensitive to the symmetry breaking at the interfaces of investigated samples.

  5. Cumulative Second Harmonic Generation in Lamb Waves for the Detection of Material Nonlinearities

    SciTech Connect

    Bermes, Christian; Jacobs, Laurence J.; Kim, Jin-Yeon; Qu, Jianmin

    2007-03-21

    An understanding of the generation of higher harmonics in Lamb waves is of critical importance for applications such as remaining life prediction of plate-like structural components. The objective of this work is to use nonlinear Lamb waves to experimentally investigate inherent material nonlinearities in aluminum plates. These nonlinearities, e.g. lattice anharmonicities, precipitates or vacancies, cause higher harmonics to form in propagating Lamb waves. The amplitudes of the higher harmonics increase with increasing propagation distance due to the accumulation of nonlinearity while the Lamb wave travels along its path. Special focus is laid on the second harmonic, and a relative nonlinearity parameter is defined as a function of the fundamental and second harmonic amplitude. The experimental setup uses an ultrasonic transducer and a wedge for the Lamb wave generation, and laser interferometry for detection. The experimentally measured Lamb wave signals are processed with a short-time Fourier transformation (STFT), which yields the amplitudes at different frequencies as functions of time, allowing the observation of the nonlinear behavior of the material. The increase of the relative nonlinearity parameter with propagation distance as an indicator of cumulative second harmonic generation is shown in the results for the alloy aluminum 1100-H14.

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

    SciTech Connect

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

    2010-05-15

    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.

  7. Optical second-harmonic generation in lossy media: Application to GaSe and InSe

    NASA Astrophysics Data System (ADS)

    Bringuier, E.; Bourdon, A.; Piccioli, N.; Chevy, A.

    1994-06-01

    The paper deals with optical second-harmonic generation in a medium absorbing the second-harmonic radiation, and where phase matching between the fundamental and second-harmonic radiation is not necessarily achieved. We first take the waves to be in the form of traveling waves, and describe the damping of the fundamental beam due to harmonic creation. It is found that both second-harmonic absorption and phase mismatch enhance the depletion length of the pump wave. Before depletion, the second-harmonic output power is independent of the traversed thickness if it exceeds the second-harmonic attenuation length. When depletion occurs, the second-harmonic output power is constant, instead of quadratic, in the input power. Next, second-harmonic generation in a plane-parallel plate of lossy material is envisaged in the case of normal incidence, including the multiple reflections expected in high-reflectance materials. The expressions of the harmonic output intensity, transmitted or reflected, of this paper and from the conventional treatment, are compared. The deviation is noticeable in the case of the transmitted harmonic power, and may be considerable in the case of the reflected power. Last, measurements of the second-harmonic output intensity in GaSe and InSe are reported at a fundamental wavelength of 1.06 μm. The sample dependence is in good agreement with our theory, which in turn is applied to derive new values of the nonlinear optical susceptibilities in the layered-structured III-VI materials. The treatment is fully analytical and may be applied to a wealth of materials.

  8. 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

    2013-12-02

    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.

  9. Imaging of collagen matrix remodeling in three-dimensional space using second harmonic generation and two photon excitation fluorescence

    NASA Astrophysics Data System (ADS)

    Abraham, Thomas; Carthy, Jon; McManus, Bruce

    2009-02-01

    Second harmonic generation (SHG), a nonlinear optical phenomenon, exhibits several in-common characteristics of twophoton excited fluorescence (TPEF) microscopy. These characteristics include identical equipment requirements from experiment to experiment and the intrinsic capability of generating 3-dimensional (D) high resolution images. Structural protein arrays that are highly ordered, such as collagen, produce strong SHG signals without the need for any exogenous label (stain). SHG and TPEF can be used together to provide information on structural rearrangements in 3D space of the collagen matrix associated with various physiological processes. In this study, we used SHG and TPEF to detect cellmediated structural reorganization of the extracellular collagen matrix in 3D space triggered by dimensional changes of embedded fibroblasts. These fibroblasts were cultured in native type I collagen gels and were stimulated to contract for a period of 24 hours. The gels were stained for cell nuclei with Hoechst and for actin with phalloidin conjugated to Alexa Fluor 488. We used non-de-scanned detectors and spectral scanning mode both in the reflection geometry for generating the 3D images and for SHG spectra, respectively. We used a tunable infrared laser with 100-fs pulses at a repetition rate of 80-MHz tuned to 800-nm for Hoechst and Alexa 488 excitations. We employed a broad range of excitation wavelengths (800 to 880-nm) with a scan interval of 10 nm to detect the SHG signal. We found that spectrally clean SHG signal peaked at 414-nm with excitation wavelength of 830-nm. The SHG spectrum has a full width half maximum (FWHM) bandwidth of 6.60-nm, which is consistent with its scaling relation to FWHM bandwidth 100-fs excitation pulses. When stimulated to contract, we found the fibroblasts to be highly elongated as well as interconnected in 2D space, and the collagen matrix, in the form of a visibly clear fibril structure, accumulated around the cells. In the absence of

  10. Enhanced generation of a second-harmonic wave in a composite of metamaterial and microwave plasma with various permittivities.

    PubMed

    Iwai, Akinori; Nakamura, Yoshihiro; Sakai, Osamu

    2015-09-01

    The generation of a second-harmonic wave, which is one typical nonlinear feature, is enhanced in a composite of plasma and metamaterial. When we generate plasma by an injection of microwaves, whose frequencies are fundamental, we observe intensified second-harmonic waves in the cases of negative-refractive-index states in which both metamaterial permeability and plasma permittivity are negative for the fundamental waves. We performed the measurements at multiple levels of microwave input power up to 300 W to regulate permittivity in the negative polarity for the fundamental wave and in the transient region, including the positive-zero-negative values, for the second-harmonic wave. We clarified that the observed enhancement results from high electron density in negative-permittivity plasma, the propagating fundamental frequency wave not being attenuated in the negative-refractive-index state, and partial phase matching between the fundamental and second-harmonic waves.

  11. Second-Harmonic Coherent Driving of a Spin Qubit in a Si/SiGe Quantum Dot.

    PubMed

    Scarlino, P; Kawakami, E; Ward, D R; Savage, D E; Lagally, M G; Friesen, Mark; Coppersmith, S N; Eriksson, M A; Vandersypen, L M K

    2015-09-04

    We demonstrate coherent driving of a single electron spin using second-harmonic excitation in a Si/SiGe quantum dot. Our estimates suggest that the anharmonic dot confining potential combined with a gradient in the transverse magnetic field dominates the second-harmonic response. As expected, the Rabi frequency depends quadratically on the driving amplitude, and the periodicity with respect to the phase of the drive is twice that of the fundamental harmonic. The maximum Rabi frequency observed for the second harmonic is just a factor of 2 lower than that achieved for the first harmonic when driving at the same power. Combined with the lower demands on microwave circuitry when operating at half the qubit frequency, these observations indicate that second-harmonic driving can be a useful technique for future quantum computation architectures.

  12. Polar structure of disclination loops in nematic liquid crystals probed by second-harmonic-light scattering.

    PubMed

    Pardaev, Shokir A; Williams, J C; Twieg, R J; Jakli, A; Gleeson, J T; Ellman, B; Sprunt, S

    2015-03-01

    Angle-resolved, second-harmonic-light scattering (SHLS) measurements are reported for three different classes of thermotropic nematic liquid crystals (NLCs): polar and nonpolar rodlike compounds and a bent-core compound. Results revealing well-defined scattering peaks are interpreted in terms of the electric polarization induced by distortions of the nematic orientational field ("flexopolarity") associated with inversion wall defects, nonsingular disclinations, analogous to Neel walls in ferromagnets, that often exhibit a closed loop morphology in NLCs. Analysis of the SHLS patterns based on this model provides a "proof-of-concept" for a potentially useful method to probe the flexopolar properties of NLCs.

  13. Second harmonic generation in binary systems of pi-conjugated compounds

    NASA Astrophysics Data System (ADS)

    Wakita, Katsuya; Sonoda, Nobuo; Shimizu, Tokihiko; Kaida, Satoshi

    1990-12-01

    A large Second Harmonic Generation (SHG) intensity which was 60 times as large as that of urea was observed in p-nitroaniline (PNA) I N-(p--nitrophenyl)ethylenediamine (NPEN) system. Results of X-ray and Scanning Electron Microscopy (SEM) analysis showed the new crystal structure. And this SHG intensity was related to cooling rate for solidification. The optimum cooling rate was in the range of 2°C/sec to 10°C/sec. Moreover, results of X-ray analysis and SHG measurements of similar binary systems showed that hydrogen bond and unique non- planar structure of NPEN played an important role for SHG and its stability.

  14. A 230-GHz radiometer system employing a second-harmonic mixer

    NASA Technical Reports Server (NTRS)

    Goldsmith, P. F.; Plambeck, R. L.

    1976-01-01

    A radiometer system for use in the 1.3 mm region has been constructed and used for radio astronomical observations. A second-harmonic mixer employing a single Schottky diode downconverts the incident power to an IF frequency of about 1400 MHz. The measured double-sideband system noise temperature is 6000 K (noise figure = 13 dB) and the double-sideband mixer conversion loss is calculated to be 10 dB. The mixer is tunable over a range of at least 15 GHz.

  15. Pure second harmonic current-phase relation in spin-filter Josephson junctions.

    PubMed

    Pal, Avradeep; Barber, Z H; Robinson, J W A; Blamire, M G

    2014-01-01

    Higher harmonics in current-phase relations of Josephson Junctions are predicted to be observed when the first harmonic is suppressed. Conventional theoretical models predict higher harmonics to be extremely sensitive to changes in barrier thickness, temperature, and so on. Here we report experiments with Josephson junctions incorporating a spin-dependent tunnelling barrier, revealing a current-phase relation for highly spin polarized barriers that is purely second harmonic in nature and is insensitive to changes in barrier thickness. This observation implies that the standard theory of Cooper pair transport through tunnelling barriers is not applicable for spin-dependent tunnelling barriers.

  16. Giant enhancement of second harmonic generation in nonlinear photonic crystals with distributed Bragg reflector mirrors.

    PubMed

    Ren, Ming-Liang; Li, Zhi-Yuan

    2009-08-17

    We theoretically investigate second harmonic generation (SHG) in one-dimensional multilayer nonlinear photonic crystal (NPC) structures with distributed Bragg reflector (DBR) as mirrors. The NPC structures have periodic modulation on both the linear and second-order susceptibility. Three major physical mechanisms, quasi-phase matching (QPM) effect, slow light effect at photonic band gap edges, and cavity effect induced by DBR mirrors can be harnessed to enhance SHG. Selection of appropriate structural parameters can facilitate coexistence of these mechanisms to act collectively and constructively to create very high SHG conversion efficiency with an enhancement by up to seven orders of magnitude compared with the ordinary NPC where only QPM works.

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

    SciTech Connect

    Levine, Z.H.

    1994-12-31

    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.

  18. Experimental investigations of second-harmonic spectra and Langmuir wave collapse

    SciTech Connect

    Dahmani, F.; Ghobrini, D.; EL-Mahdaoui, M. )

    1991-09-01

    Two kinds of experimental results obtained from time-resolved second-harmonic spectra for 1.06 {mu}m laser-produced plasma are presented. At moderate laser intensities ({le}2{times}10{sup 14} W/cm{sup 2}) the results are explained with parametric and electron decay instabilities. Whereas, at high laser intensities ({ge}6{times}10{sup 14} W/cm{sup 2}) the Langmuir strong turbulence is used to explain experimental results. In addition to results obtained by Briand {ital et} {ital al}. (Phys. Fluids B {bold 2}, 160 (1990)), a second sequence of collapses is observed.

  19. Hilbert reconstruction of phase-shifted second-harmonic holographic images.

    PubMed

    Smith, David R; Winters, David G; Schlup, Philip; Bartels, Randy A

    2012-06-01

    New techniques are presented that make phase-shifting holography viable for second-harmonic generation (SHG) holography with weak object fields. We developed an intrinsic phase shift calibration of SHG holograms, an algorithm that extracts the reference and object intensity directly from a set of phase-shifted holographic data, and a more robust phase-shifting holography reconstruction algorithm based on π-shifted hologram pairs that permits self-calibration of the phase shift and recovery of the complex field through a Hilbert transform.

  20. Quantitative biomarkers of colonic dysplasia based on intrinsic second-harmonic generation signal

    NASA Astrophysics Data System (ADS)

    Zhuo, Shuangmu; Zhu, Xiaoqin; Wu, Guizhu; Chen, Jianxin; Xie, Shusen

    2011-12-01

    Most colorectal cancers arise from dysplastic lesions, such as adenomatous polyps, and these lesions are difficult to be detected by the current endoscopic screening approaches. Here, we present the use of an intrinsic second-harmonic generation (SHG) signal as a novel means to differentiate between normal and dysplastic human colonic tissues. We find that the SHG signal can quantitatively identify collagen change associated with colonic dysplasia that is indiscernible by conventional pathologic techniques. By comparing normal with dysplastic mucosa, there were significant differences in collagen density and collagen fiber direction, providing substantial potential to become quantitative intrinsic biomarkers for in vivo clinical diagnosis of colonic dysplasia.

  1. Application of quantitative second-harmonic generation microscopy to dynamic conditions.

    PubMed

    Kabir, Mohammad M; Inavalli, V V G Krishna; Lau, Tung-Yuen; Toussaint, Kimani C

    2013-01-01

    We present a quantitative second-harmonic generation (SHG) imaging technique that quantifies the 2D spatial organization of collagen fiber samples under dynamic conditions, as an image is acquired. The technique is demonstrated for both a well-aligned tendon sample and a randomly aligned, sparsely distributed collagen scaffold sample. For a fixed signal-to-noise ratio, we confirm the applicability of this method for various window sizes (pixel areas) as well as with using a gridded overlay map that allows for correlations of fiber orientations within a given image. This work has direct impact to in vivo biological studies by incorporating simultaneous SHG image acquisition and analysis.

  2. Chiral imaging of collagen by second-harmonic generation circular dichroism

    PubMed Central

    Lee, H.; Huttunen, M. J.; Hsu, K.-J.; Partanen, M.; Zhuo, G.-Y.; Kauranen, M.; Chu, S.-W.

    2013-01-01

    We provide evidence that the chirality of collagen can give rise to strong second-harmonic generation circular dichroism (SHG-CD) responses in nonlinear microscopy. Although chirality is an intrinsic structural property of collagen, most of the previous studies ignore that property. We demonstrate chiral imaging of individual collagen fibers by using a laser scanning microscope and type-I collagen from pig ligaments. 100% contrast level of SHG-CD is achieved with sub-micrometer spatial resolution. As a new contrast mechanism for imaging chiral structures in bio-tissues, this technique provides information about collagen morphology and three-dimensional orientation of collagen molecules. PMID:23761852

  3. Communication: Reactions and adsorption at the surface of silver nanoparticles probed by second harmonic generation.

    PubMed

    Gan, Wei; Gonella, Grazia; Zhang, Min; Dai, Hai-Lung

    2011-01-28

    Even though nanoparticles have dimensions much smaller than the optical wavelength and shapes commonly with inversion symmetry, we show, for the first time, direct experimental evidence that second harmonic generation (SHG) can be detected from the surface layer of metallic nanoparticles, in this case 40 nm radius Ag particles. The SH intensity detected is shown to substantially decrease upon chemical bonding of thiol molecules to the Ag particle surface. The surface generated SH intensity can be used for probing properties and processes at the nanoparticle surface.

  4. Effective medium multipolar tensor analysis of second-harmonic generation from metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Zdanowicz, Mariusz; Kujala, Sami; Husu, Hannu; Kauranen, Martti

    2011-02-01

    We present a detailed multipolar tensor analysis of second-harmonic (SH) generation from arrays of L-shaped gold nanoparticles. We define three effective nonlinear tensors, which include electric dipoles only (Aeee) and lowest-order magnetic (and quadrupole) effects at the fundamental (Aeem) and the SH (Amee) frequency. The components of the various tensors are distinguished through their different transformations as the experimental geometry is varied. The response is dominated by electric-dipole effects. However, the higher multipoles also play a significant role and are more important at the fundamental frequency than at the SH frequency. The results correlate well with the particles' plasmonic resonances and symmetry rules.

  5. Second-harmonic generation in a silicon-carbide-based photonic crystal nanocavity.

    PubMed

    Yamada, Shota; Song, Bong-Shik; Jeon, Seungwoo; Upham, Jeremy; Tanaka, Yoshinori; Asano, Takashi; Noda, Susumu

    2014-04-01

    We demonstrate second-harmonic generation (SHG) in a silicon-carbide (SiC)-based heterostructure photonic crystal nanocavity by using a pulsed laser. We observe SHG light radiated from the SiC nanocavity and estimate the conversion efficiency in the cavity to be 2.59×10(-5) (=0.15  W(-1)) at an average input power of 0.17 mW. The near-field patterns and polarization characteristics of the SHG light are investigated experimentally and theoretically, and the results are in qualitatively good agreement.

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

    NASA Astrophysics Data System (ADS)

    McConnell, Gail; Ferguson, Allister I.

    2005-03-01

    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.

  7. Resolution and contrast enhancement of subtractive second harmonic generation microscopy with a circularly polarized vortex beam

    PubMed Central

    Tian, Nian; Fu, Ling; Gu, Min

    2015-01-01

    We extend the subtractive imaging method to label-free second harmonic generation (SHG) microscopy to enhance the spatial resolution and contrast. This method is based on the intensity difference between two images obtained with circularly polarized Gaussian and doughnut-shaped beams, respectively. By characterizing the intensity and polarization distributions of the two focused beams, we verify the feasibility of the subtractive imaging method in polarization dependent SHG microscopy. The resolution and contrast enhancement in different biological samples is demonstrated. This work will open a new avenue for the applications of SHG microscopy in biomedical research. PMID:26364733

  8. Nanoscale optical properties of metal nanoparticles probed by Second Harmonic Generation microscopy.

    PubMed

    Shen, Hong; Nguyen, Ngoc; Gachet, David; Maillard, Vincent; Toury, Timothée; Brasselet, Sophie

    2013-05-20

    We report spatial and vectorial imaging of local fields' confinement properties in metal nanoparticles with branched shapes, using Second Harmonic Generation (SHG) microscopy. Taking advantage of the coherent nature of this nonlinear process, the technique provides a direct evidence of the coupling between the excitation polarization and both localization and polarization specificities of local fields at the sub-diffraction scale. These combined features, which are governed by the nanoparticles' symmetry, are not accessible using other contrasts such as linear optical techniques or two-photon luminescence.

  9. Multipole interference in the second-harmonic optical radiation from gold nanoparticles.

    PubMed

    Kujala, Sami; Canfield, Brian K; Kauranen, Martti; Svirko, Yuri; Turunen, Jari

    2007-04-20

    We provide experimental evidence of higher multipole (magnetic dipole and electric quadrupole) radiation in second-harmonic (SH) generation from arrays of metal nanoparticles. Fundamental differences in the radiative properties of electric dipoles and higher multipoles yield opposite interference effects observed in the SH intensities measured in the reflected and transmitted directions. These interference effects clearly depend on the polarization of the fundamental field, directly indicating the importance of multipole effects in the nonlinear response. We estimate that higher multipoles contribute up to 20% of the total emitted SH field amplitude for certain polarization configurations.

  10. Laser dyes excited by high PRR Nd:YAG laser second-harmonic radiation

    NASA Astrophysics Data System (ADS)

    Soldatov, A. N.; Donin, V. I.; Jakovin, D. V.; Reimer, I. V.

    2008-01-01

    The lasing characteristics of red-emitting dyes in ethanol excited by Nd:YAG laser second-harmonic radiation are examined. The Nd:YAG laser was pumped by a diode matrix. The pump pulse repetition rates (PRRs) were 2.5 - 10 kHz and the pulse duration was 60 - 300 ns. The following dyes were evaluated: oxazine 17, DCM, DCM sp, and pyridine 1. The conversion efficiency for oxazine was 25 % without wavelength selection and 15 % with wavelength selection over the tuning range from 630 to 700 nm. The Nd:YAG and dye laser designs used are described elsewhere [1,2].

  11. High-resolution frequency-domain second-harmonic optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Su, Jianping; Tomov, Ivan V.; Jiang, Yi; Chen, Zhongping

    2007-04-01

    We used continuum generated in an 8.5 cm long fiber by a femtosecond Yb fiber laser to improve threefold the axial resolution of frequency domain second-harmonic optical coherence tomography (SH-OCT) to 12 μm. The acquisition time was shortened by more than 2 orders of magnitude compared to the time-domain SH-OCT. The system was applied to image biological tissue of fish scales, pig leg tendon, and rabbit eye sclera. Highly organized collagen fibrils can be visualized in the recorded images. Polarization dependence on the SH has been used to obtain polarization resolved images.

  12. Estimation of transverse spin penetration length using second-harmonic measurement: Proposal of an experimental method

    NASA Astrophysics Data System (ADS)

    Baláž, Pavel; Zwierzycki, Maciej; Ansermet, Jean-Philippe; Barnaś, Józef

    2016-10-01

    A theoretical description of spin current injection from a nonmagnetic layer into a magnetic one is presented, with the main emphasis on the description and determination of the penetration depth of spin current component transverse to the magnetization. This penetration depth also determines the depth of spin transfer torque generation. Physically, the spin current may be driven by an external electric field or by a temperature gradient. To determine the penetration depth we used ab initio calculations of channel and mixing conductances as well as of mixing transmission. The results are then used to determine the second harmonic voltage response, which in turn can be used to determine the penetration depth experimentally.

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

    NASA Astrophysics Data System (ADS)

    Baghban, Mohammad Amin; Gallo, Katia

    2016-09-01

    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.

  14. Characterization of magnetization-induced second harmonic generation in iron oxide polymer nanocomposites.

    PubMed

    Vandendriessche, Stefaan; Valev, Ventsislav K; Verbiest, Thierry

    2012-01-10

    We have measured the magnetization-induced second harmonic generation (MSHG) of a nanocomposite consisting of iron oxide nanoparticles in a polymer film. The existing theoretical framework is extended to include DC magnetic fields in order to characterize the MSHG signal and analyze the measurements. Additionally, magnetic hysteresis loops are measured for four principal polarizer-analyzer configurations, revealing the P(IN)-P(OUT) and S(IN)-P(OUT) polarizer-analyzer configurations to be sensitive to the transverse magnetic field. These results demonstrate the use of MSHG and the applied formalism as a tool to study magnetic nanoparticles and their magnetic properties.

  15. Second harmonic conversion in cubic silicon carbide at 1.06 micron

    NASA Technical Reports Server (NTRS)

    Harris, G. L.; Jones, E. W.; Spencer, M. G.; Jackson, K. H.

    1991-01-01

    This letter describes second harmonic conversion in cubic silicon carbide (beta-SiC) at a wavelength of 1.06 micron. Epitaxial layers of beta-SiC formed by vapor phase growth on silicon are indeed birefringent, and thus phase matchable. Phase-matched films of beta-SiC have respectable conversion efficiencies even in the presence of adsorption at 532 nm. The measured value of the effective second order nonlinear susceptibility for beta-SiC is chi super (2) eff = 1.05 +/- 0.3 x 10 exp -9 esu.

  16. The Use of Second Harmonic Generation to Image the Extracellular Matrix During Tumor Progression

    PubMed Central

    Burke, Kathleen; Brown, Edward

    2014-01-01

    Abstract Metastasis is the leading cause of cancer mortality, resulting from changes in the tumor microenvironment which increases tumor cell migration, dispersal to distant organs, and subsequent survival. This is accompanied by changes in tumor collagen which may allow cells to travel more efficiently away from a primary tumor and invade the surrounding tissue. Second Harmonic generation (SHG) is an intrinsic optical signal that has expanded our understanding of collagen evolution throughout tumor progression. This article addresses current research into tumor progression using SHG, as well as the future prospects of using SHG to advance our understanding of the tumor microenvironment. PMID:28243512

  17. Surface plasmon polariton excitation by second harmonic generation in single organic nanofibers.

    PubMed

    Simesen, Paw; Søndergaard, Thomas; Skovsen, Esben; Fiutowski, Jacek; Rubahn, Horst-Günter; Bozhevolnyi, Sergey I; Pedersen, Kjeld

    2015-06-15

    Coherent local excitation of surface plasmon polaritons (SPPs) by second-harmonic generation (SHG) in individual aligned crystalline organic functionalized para-phenylene nanofibers deposited on a thin silver film is demonstrated. The SH-SPP generation is considered theoretically and investigated experimentally with angular-resolved leakage radiation spectroscopy for normal incidence of the excitation beam. Both measurements and simulations show asymmetric excitation of left- and right-propagating SH-SPPs, which is explained as an effect of fiber molecules being oriented at an angle relative to the silver film surface.

  18. Strong enhancement of second harmonic generation in 2-methyl-4-nitroaniline nanofibers

    NASA Astrophysics Data System (ADS)

    Isakov, Dmitry; de Matos Gomes, Etelvina; Belsley, Michael Scott; Almeida, Bernardo; Cerca, Nuno

    2012-07-01

    An effective control of the second harmonic generation (SHG) efficiency in electrospun nanofibers of nonlinear optically active 2-methyl-4-nitroaniline and carrier polymer poly(l-lactic acid) (MNA-PLLA) is presented. The SHG efficiency of the MNA-PLLA fibers strongly depends on the diameter of the nanofibers and can be increased up to an order of magnitude by controlling the electrospinning processing parameters. For optimal electrospinning process conditions, MNA-PLLA nanofibers with an effective nonlinear optical coefficient that is two orders of magnitude greater than the counterpart bulk powder MNA may be obtained. The work can be used as a guideline for the manufacture of nanophotonic devices.

  19. Uniform polarity microtubule assemblies imaged in native brain tissue by second-harmonic generation microscopy.

    PubMed

    Dombeck, Daniel A; Kasischke, Karl A; Vishwasrao, Harshad D; Ingelsson, Martin; Hyman, Bradley T; Webb, Watt W

    2003-06-10

    Microtubule (MT) ensemble polarity is a diagnostic determinant of the structure and function of neuronal processes. Here, polarized MT structures are selectively imaged with second-harmonic generation (SHG) microscopy in native brain tissue. This SHG is found to colocalize with axons in both brain slices and cultured neurons. Because SHG arises only from noninversion symmetric structures, the uniform polarity of axonal MTs leads to the observed signal, whereas the mixed polarity in dendrites leads to destructive interference. SHG imaging provides a tool to investigate the kinetics and function of MT ensemble polarity in dynamic native brain tissue structures and other subcellular motility structures based on polarized MTs.

  20. Femtosecond superradiance in semiconductor lasers: anomalous internal second-harmonic generation

    NASA Astrophysics Data System (ADS)

    Vasil'ev, P. P.; Putilin, A. N.; Sergeev, A. B.

    2016-10-01

    The emission of anomalously bright blue light under internal doubling of the frequency of femtosecond superradiance pulses in the active medium of semiconductor GaAs/AlGaAs laser heterostructures has been experimentally found. The efficiency of the internal second-harmonic generation is an order of magnitude higher than in the conventional lasing regime. This effect is due to the formation of a transient ordered state of electrons and holes under superradiance, occurrence of dynamic coherent population lattices, and periodic modulation of the nonlinear susceptibility of the medium.

  1. Electric field-induced optical second harmonic generation in nematic liquid crystal 5CB

    NASA Astrophysics Data System (ADS)

    Torgova, S. I.; Shigorin, V. D.; Maslyanitsyn, I. A.; Todorova, L.; Marinov, Y. G.; Hadjichristov, G. B.; Petrov, A. G.

    2014-12-01

    Electric field-induced second harmonic generation (EFISH) was studied for the liquid crystal 4-cyano-4'-pentylbiphenyl (5CB) (a nematic phase material at room temperature). The intensity of coherent SHG from 5CB cells upon DC electric field was measured for various initial orientations of the liquid crystal. The dependence of the SHG intensity on the pump beam incidence angle was obtained in transmission geometry using sample rotation method. The experimental results (the registered light intensity in the output SHG interference patterns) were theoretically modelled and analyzed.

  2. Chiral imaging of collagen by second-harmonic generation circular dichroism.

    PubMed

    Lee, H; Huttunen, M J; Hsu, K-J; Partanen, M; Zhuo, G-Y; Kauranen, M; Chu, S-W

    2013-06-01

    We provide evidence that the chirality of collagen can give rise to strong second-harmonic generation circular dichroism (SHG-CD) responses in nonlinear microscopy. Although chirality is an intrinsic structural property of collagen, most of the previous studies ignore that property. We demonstrate chiral imaging of individual collagen fibers by using a laser scanning microscope and type-I collagen from pig ligaments. 100% contrast level of SHG-CD is achieved with sub-micrometer spatial resolution. As a new contrast mechanism for imaging chiral structures in bio-tissues, this technique provides information about collagen morphology and three-dimensional orientation of collagen molecules.

  3. 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

    2007-02-28

    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)

  4. Predictions of quantum mechanics and stochastic electrodynamics in travelling wave second harmonic generation

    NASA Astrophysics Data System (ADS)

    Olsen, M. K.; Dechoum, K.; Plimak, L. I.

    2001-04-01

    We show that stochastic electrodynamics and quantum mechanics give quantitatively different predictions for the quantum nondemolition (QND) correlations in travelling wave second harmonic generation. Using phase space methods and stochastic integration, we calculate correlations in both the positive-P and truncated Wigner representations, the latter being equivalent to the semi-classical theory of stochastic electrodynamics. We show that the semi-classical results are different in the regions where the system performs best in relation to the QND criteria, and that they significantly overestimate the performance in these regions.

  5. Multiferroic Behavior in Barium Hexaferrite Probed with Optical Second Harmonic Generation

    NASA Astrophysics Data System (ADS)

    Vlahos, Eftihia; Denev, Sava; Gopalan, Venkatraman; Kimura, Tsuyoshi

    2007-03-01

    Barium hexaferrite Ba0.5Sr1.5Zn2Fe12O22 is a very promising material, which exhibits significant magnetoelectric (ME) effect, i.e., the generation of electric polarization/magnetization by the application of magnetic/electric) field. Optical second harmonic generation (SHG) in the reflection geometry was used to determine the magnetic point group symmetries and phase transitions of the sample versus temperature, and variable magnetic field. Simultaneous measurements of magnetocapacitance, and ME current as functions of temperature and applied magnetic field are performed and correlated with SHG measurements.

  6. The role of electromagnetic interactions in second harmonic generation from plasmonic metamaterials

    NASA Astrophysics Data System (ADS)

    Alberti, Julian; Linnenbank, Heiko; Linden, Stefan; Grynko, Yevgen; Förstner, Jens

    2016-02-01

    We report on second harmonic generation spectroscopy on a series of rectangular arrays of split-ring resonators. Within the sample series, the lattice constants are varied, but the area of the unit cell is kept fixed. The SHG signal intensity of the different arrays upon resonant excitation of the fundamental plasmonic mode strongly depends on the respective arrangement of the split-ring resonators. This finding can be explained by variations of the electromagnetic interactions between the split-ring resonators in the different arrays. The experimental results are in agreement with numerical calculations based on the discontinuous Galerkin time-domain method.

  7. Correlating second harmonic optical responses of single Ag nanoparticles with morphology.

    PubMed

    Jin, Rongchao; Jureller, Justin E; Kim, Hee Y; Scherer, Norbert F

    2005-09-14

    Femtosecond laser excited second harmonic (SH) activity from single Ag nanoparticles is reported. A correlation of SH single-particle measurements with high-resolution imaging of particle morphology by TEM was achieved by creating position markers on an optical and electron transparent substrate (Si3N4 thin film, approximately 100 nm). We compared the SH activity of single Ag nanoparticles (nanospheres versus nanorods) and cluster structures (composed of two or multiple particles, e.g., dimers and trimers). The direct correlation of single-particle structures and SH activity, spectral and power dependence, strongly suggests one-photon resonant driven nonlinear oscillator response mechanism.

  8. Graphics processing unit-based quantitative second-harmonic generation imaging

    NASA Astrophysics Data System (ADS)

    Kabir, Mohammad Mahfuzul; Jonayat, ASM; Patel, Sanjay; Toussaint, Kimani C., Jr.

    2014-09-01

    We adapt a graphics processing unit (GPU) to dynamic quantitative second-harmonic generation imaging. We demonstrate the temporal advantage of the GPU-based approach by computing the number of frames analyzed per second from SHG image videos showing varying fiber orientations. In comparison to our previously reported CPU-based approach, our GPU-based image analysis results in ˜10× improvement in computational time. This work can be adapted to other quantitative, nonlinear imaging techniques and provides a significant step toward obtaining quantitative information from fast in vivo biological processes.

  9. Second-harmonic generation enhancement in the presence of Tamm plasmon-polaritons.

    PubMed

    Afinogenov, B I; Bessonov, V O; Fedyanin, A A

    2014-12-15

    Resonant enhancement of second-harmonic generation (SHG) intensity from a thin metal film is demonstrated in a Tamm plasmon-polariton mode excited at a metal/photonic crystal interface using nonlinear spectroscopy. Nonlinear effects enhancement in proposed structures exhibit strong polarization dependence (1:200 for the orthogonal fundamental polarizations). SHG enhancement factor evinces considerable angular dependence, rising from 50 for the 45° angle of incidence to 170 for the 10° angle of incidence. The results are analyzed numerically using a nonlinear transfer matrix technique. The findings elucidate the potential of Tamm plasmon-polaritons in the nonlinear optical applications.

  10. Second harmonic generation microscopy to investigate collagen configuration: a pericarditis case study.

    PubMed

    Bélisle, Jonathan; Zigras, Tiffany; Costantino, Santiago; Cartier, Raymond; Butany, Jagdish; Wiseman, Paul W; Leask, Richard L

    2010-01-01

    We have used second-harmonic-generation (SHG) to image collagen fibers in pericardial tissue removed from a patient with constrictive pericarditis and compared this to healthy pericardium. SHG imaging allowed for the visualization of collagen fibers without the need for staining or pretreatment. Images were compared to stained histology slides. Collagen fibers in SHG and histology images displayed the same structure and morphology. The mature collagen of the parietal pericardium was easily distinguishable from the new collagen accumulation due to the pericarditis. SHG imaging can provide a convenient and valuable architectural profile of collagen organization.

  11. Discrete convolution of digital optical signals during noncollinear second harmonic generation in the LiIO3 crystal

    NASA Astrophysics Data System (ADS)

    Berishev, I. E.; Rakovskii, V. Iu.; Selishchev, A. V.; Shcherbakov, A. S.

    1989-04-01

    The paper reports results of an experimental study of the possibility of implementing the discrete convolution of digital optical signals using the effect of second harmonic generation in a crystal with quadratic nonlinearity. With reference to results obtained for a LiIO3 single crystal, it is shown that, in the regime of noncollinear optical second harmonic generation, a nonlinear crystal can be used as a high-speed active element of a digital optical processor with parallel coding of binary data.

  12. Enhanced second harmonic generation of MoS2 layers on a thin gold film.

    PubMed

    Zeng, Jianhua; Yuan, Maohui; Yuan, Weiguang; Dai, Qiaofeng; Fan, Haihua; Lan, Sheng; Tie, Shaolong

    2015-08-28

    The linear and nonlinear optical properties of thin MoS2 layers exfoliated on an Au/SiO2 substrate were investigated both numerically and experimentally. It was found that the MoS2 layers with different thicknesses exhibited different colors on the gold film. The reflection spectra of the MoS2 layers with different thicknesses were calculated by using the finite-difference time-domain technique and the corresponding chromaticity coordinates were derived. The electric field enhancement factors at both the fundamental light and the second harmonic were calculated and the enhancement factors for second harmonic generation (SHG) were estimated for the MoS2 layers with different thicknesses. Different from the MoS2 layers on a SiO2/Si substrate where the maximum SHG was observed in the single-layer MoS2, the maximum SHG was achieved in the 17 nm-thick MoS2 layer on the Au/SiO2 substrate. As compared with the MoS2 layers on the SiO2/Si substrate, a significant enhancement in SHG was found for the MoS2 layers on the Au/SiO2 substrate due to the strong localization of the electric field. More interestingly, it was demonstrated experimentally that optical data storage can be realized by modifying the SHG intensity of a MoS2 layer through thinning its thickness.

  13. Modulation Index Adjustment for Recovery of Pure Wavelength Modulation Spectroscopy Second Harmonic Signal Waveforms

    PubMed Central

    Wei, Wei; Chang, Jun; Wang, Qiang; Qin, Zengguang

    2017-01-01

    A new technique of modulation index adjustment for pure wavelength modulation spectroscopy second harmonic signal waveforms recovery is presented. As the modulation index is a key parameter in determining the exact form of the signals generated by the technique of wavelength modulation spectroscopy, the method of modulation index adjustment is applied to recover the second harmonic signal with wavelength modulation spectroscopy. By comparing the measured profile with the theoretical profile by calculation, the relationship between the modulation index and average quantities of the scanning wavelength can be obtained. Furthermore, when the relationship is applied in the experimental setup by point-by-point modulation index modification for gas detection, the results show good agreement with the theoretical profile and signal waveform distortion (such as the amplitude modulation effect caused by diode laser) can be suppressed. Besides, the method of modulation index adjustment can be used in many other aspects which involve profile improvement. In practical applications, when the amplitude modulation effect can be neglected and the stability of the detection system is limited by the sampling rate of analog-to-digital, modulation index adjustment can be used to improve detection into softer inflection points and solve the insufficient sampling problem. As a result, measurement stability is improved by 40%. PMID:28098842

  14. Pattern formation of second harmonic conical waves in a nonlinear medium with extended defect structure.

    PubMed

    Lin, Y C; Su, K W; Huang, K F; Chen, Y F

    2014-11-17

    We experimentally demonstrate the propagation of the conical second harmonic fields generated from a nonlinear crystal with extended defects to investigate their pattern formation. The generated second harmonic waves are found to be the interference of multiple Bessel-like beams that originate from distinct longitudinal layers inside the crystal. To reconstruct the experimental results, we model the individual Bessel-like beam to be the superposition of an ensemble of identical decentered Gaussian waves with random phases. We present that the randomness of the phases leads the Bessel-like beams to show wave profiles with different extent of localization. Moreover, we use the coherent superposition of the developed wave functions with a phase factor to manifest the interference of multiple Bessel-like beams. The relative phases among the Bessel-like beams are shown to be closely related to the near and far-field patterns. With the experimental observations and the theoretical model, the relative phases are decided to successfully reconstruct the propagation characteristics of the multiple Bessel-like beams.

  15. Highly efficient second harmonic generation in hyperbolic metamaterial slot waveguides with large phase matching tolerance.

    PubMed

    Sun, Yu; Zheng, Zheng; Cheng, Jiangtao; Sun, Guodong; Qiao, Guofu

    2015-03-09

    Highly efficient second harmonic generation (SHG) bridging the mid-infrared (IR) and near-IR wavelengths in a coupled hyperbolic metamaterial waveguide with a nonlinear-polymer-filled nanoscale slot is theoretically investigated. By engineering the geometrical parameters, the collinear phase matching condition is satisfied between the even hybrid modes at the fundamental frequency (3,100 nm) and the second harmonic (1,550 nm). Two modes manifest the great field overlap and the significant field enhancement in the nonlinear integration area (i.e. the slot), which leads to extreme large nonlinear coupling coefficient. For a low pumping power of 100 mW, the device length is as short as 2.19 µm and the normalized conversion efficiency comes up to more than 6.37 × 10(5) W(-1)cm(-2) which outperforms that of the plasmonic-based structures. Moreover, the efficient SHG can be achieved with great phase matching tolerance, i.e., a small theoretical fabrication-error sensitivity to filling ratio and a broad pump bandwidth in a compact device length of 2.19 µm using 100 mW pump. The proposed scheme links the mature near-IR devices to the mid-IR regime and have a great potential for integrated chip-scale all-optical signal processes.

  16. Highly efficient second harmonic generation of a light carrying orbital angular momentum in an external cavity.

    PubMed

    Zhou, Zhi-Yuan; Li, Yan; Ding, Dong-Sheng; Zhang, Wei; Shi, Shuai; Shi, Bao-Sen; Guo, Guang-Can

    2014-09-22

    Traditional methods for generating a light carrying orbital angular momentum (OAM) include the use of holographic diffraction gratings, vortex phase plates and spatial light modulators. Here we report a new method for highly efficient second-harmonic generation (SHG) of a light with OAM. By properly aligning an external cavity that contains a quasi-phase matching nonlinear crystal and pumping it with a light carrying OAM, mode matching between the pump light and the cavity's higher order Laguerre-Gaussian (LG) mode is achieved, SHG with a conversion efficiency of up to 10.3% is obtained. We have demonstrated for the first time that the cavity can stably operate at its higher order LG mode similar to that of a Gaussian mode. The second harmonic generated light has an OAM value that is double with respected to the OAM value of the pump light. The parameters that affect the beam quality and conversion efficiency are discussed in detail. Our work opens a brand new field in laser optics and makes the first step toward high efficiency processing using a light carrying OAM.

  17. Discrimination of radiation quality through second harmonic out-of-phase cw-ESR detection.

    PubMed

    Marrale, Maurizio; Longo, Anna; Brai, Maria; Barbon, Antonio; Brustolon, Marina

    2014-02-01

    The ability to discriminate the quality of ionizing radiation is important because the biological effects produced in tissue strongly depends on both absorbed dose and linear energy transfer (LET) of ionizing particles. Here we present an experimental electron spin resonance (ESR) analysis aimed at discriminating the effective LETs of various radiation beams (e.g., 19.3 MeV protons, (60)Co photons and thermal neutrons). The measurement of the intensities of the continuous wave spectrometer signal channel first harmonic in-phase and the second harmonic out-of-phase components are used to distinguish the radiation quality. A computational analysis, was carried out to evaluate the dependence of the first harmonic in-phase and second harmonic out-of-phase components on microwave power, modulation amplitude and relaxation times, and highlights that these components could be used to point out differences in the relaxation times. On the basis of this numerical analysis the experimental results are discussed. The methodology described in this study has the potential to provide information on radiation quality.

  18. Second harmonic excitation spectroscopy in studies of Fano-type coupling in plasmonic arrays (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Walsh, Gary F.; Trevino, Jacob T.; Pecora, Emanuele Francesco; Dal Negro, Luca

    2015-09-01

    Scattering by plasmon resonances of metallic nanoparticles can be tailored by particle material, size, shape, and local as well as long-range order. In this presentation we discuss a series of experiments in which long-range Fano-type coupling between grating resonances and localized surface palsmon (LSP) resonances were studied using second harmonic excitation (SH-E) spectroscopy. By tuning the excitation wavelength of a femtosecond laser and measuring the relative second harmonic (SH) signal we demonstrated that when long-range grating resonances spectrally overlap with those of the LSPs, electromagnetic field enhancement occurs on the surface of the nanoparticles leading to an increase in nonlinear scattering. This effect has been demonstrated for periodic arrays of monomers and dimers, bi-periodic antenna arrays for multi-spectral focusing to a single point, and chirped nanoparticle structures for broadband field enhancement. Results are supported by finite difference time domain simulations showing that electromagnetic fields are enhanced close on the surface of the nanoparticles when long-range structural resonances are excited. These studies have revealed design principles for engineering the interplay of photonic and plasmonic coupling for future linear and nonlinear plasmonic devices.

  19. Interest of second harmonic generation imaging for diagnosis in thick and opaque tissue.

    PubMed

    Werkmeister, E; de Isla, N; Marchal, L; Stoltz, J F; Dumas, D

    2008-01-01

    In articular hyaline cartilage, chondrocytes are surrounded by an extracellular matrix which is mainly composed by collagen and proteoglycanes. Pathological specimens show a partial or complete degradation of this matrix. Therefore, it could be interesting to know how mechanical or biochemical constraints applied to cartilage specimens induce modifications of the cartilage network. Multiphoton technology combined to Second Harmonic Generation (SHG) enables to image cartilage specimens in a non-invasive mode with high resolution at deep penetration. By placing a band pass filter in front of the transmitted light detector, SHG signal with frequency doubled can be isolated for a new contrast imaging. SHG (second harmonic generation) is a diffusion process generated from organized structures and does not need any fluorescent staining. Due to their non-centrosymetric structure, collagen fibrilles present a high second-order non-linear susceptibility and thus give rise to a strong SHG signal when exposed to high enough electric fields produced by a focal point of a femtosecond pulsed laser (multiphoton microscopy). As the extracellular matrix of cartilage is in part constituted by collagen fibers, it can be imaged with this contrast tool. The intensity of SHG signals strongly depends on the organization of collagen fibers. Thus a modification of the extracellular matrix in terms of 3D-organization of collagen induced by mechanical stress can be shown with this contrast tool.

  20. Texture analysis applied to second harmonic generation image data for ovarian cancer classification.

    PubMed

    Wen, Bruce L; Brewer, Molly A; Nadiarnykh, Oleg; Hocker, James; Singh, Vikas; Mackie, Thomas R; Campagnola, Paul J

    2014-09-01

    Remodeling of the extracellular matrix has been implicated in ovarian cancer. To quantitate the remodeling, we implement a form of texture analysis to delineate the collagen fibrillar morphology observed in second harmonic generation microscopy images of human normal and high grade malignant ovarian tissues. In the learning stage, a dictionary of “textons”—frequently occurring texture features that are identified by measuring the image response to a filter bank of various shapes, sizes, and orientations—is created. By calculating a representative model based on the texton distribution for each tissue type using a training set of respective second harmonic generation images, we then perform classification between images of normal and high grade malignant ovarian tissues. By optimizing the number of textons and nearest neighbors, we achieved classification accuracy up to 97% based on the area under receiver operating characteristic curves (true positives versus false positives). The local analysis algorithm is a more general method to probe rapidly changing fibrillar morphologies than global analyses such as FFT. It is also more versatile than other texture approaches as the filter bank can be highly tailored to specific applications (e.g., different disease states) by creating customized libraries based on common image features.

  1. Characterization of the correlation between collagen fibril thickness and forward and backward second harmonic signal

    NASA Astrophysics Data System (ADS)

    Hsueh, Chiu-Mei; Hovhannisyan, Vladimir A.; Dong, Chen-Yuan

    2011-07-01

    Optical-based microscopy plays an important role in various scientific fields such as physics, chemistry and biology. Second harmonic generation (SHG) microscopy has become one of the indispensable tools for biomedical imaging for the last decade because the signal generated from SHG is sensitive to the objective structure and this amazing non-invasive method can also directly observe the objective without using extra fluorescent labels, especially for collagen molecules. As the most abundant protein in animals, collagen is responsible for a number of important structural and functional roles in vertebrates. For certain diseases, it has been shown that collagen fiber diameter has a significant variation and thus as a vital symptom for diagnosis. Moreover, collagen diameter is also a key parameter for fibrogenesis studying. Therefore, the determination of collagen fiber diameter is important for studying biophysical processes and identifying bioengineering applications. In this study, we investigated various collagen fibril thicknesses and the corresponding forward (FSHG) and backward (BSHG) second harmonic signal intensity variation. Our result exhibits that SHG intensity can quantify describe the relative collagen fibril thickness alteration, which also indicates the coherent effect difference between FSHG and BSHG. This approach demonstrates the capability of SHG imaging in providing collagen mechanical information and that may be applied in the evaluation of advancing collagen issues in vivo.

  2. Pulsed Bessel-Gauss beams: a depleted wave model for type II second-harmonic generation.

    PubMed

    Sabaeian, Mohammad; Motazedian, Alireza; Mohammad Rezaee, Mostafa; Jalil-Abadi, Fatemeh Sedaghat

    2014-11-10

    In this work, a three-dimensional and time-dependent nonlinear wave model to describe the generation of pulsed Bessel-Gauss second-harmonic waves (SHWs) is presented. Three coupled equations, two for ordinary and extraordinary fundamental waves and one for extraordinary SHWs, describing type II second-harmonic generation (SHG) in a KTiOPO4 (KTP) crystal were solved by considering the depletion of fundamental waves (FWs). The results examined the validity of nondepleted wave approximation against the energy of pulses, beam spot size, and interaction length. It was shown that for pulses with spot sizes of ωf=80  μm and energy of 0.8j, the nonlinear interaction was accomplished over a distance of ∼5  mm. Therefore, for KTP crystals with lengths longer than 5 mm, the nondepleted wave approximation can no longer be valid. To be valid, the crystal must be shorter than the interaction length, i.e., 5 mm.

  3. Ethylenediaminium di(2-nitrophenolate) single crystals as materials for optical second harmonic generation

    NASA Astrophysics Data System (ADS)

    Thangaraj, M.; Ravi, G.; Sabari Girisun, T. C.

    2014-09-01

    An organic second harmonic generation (SHG) active material, ethylenediaminium di(2-nitrophenolate) (EDA2NP) was synthesized through proton transfer reaction. Good quality single crystals of dimension 6×4×2 mm3 were grown by solvent evaporation method using ethanol as a solvent for the first time in literature. The lattice parameters of the grown crystals were determined by X-ray diffraction studies. Fourier Transform Infra Red (FT-IR) spectrum was recorded to identify the presence of various functional groups and the molecular structure was confirmed by nuclear magnetic resonance (NMR) spectrum. Thermal analyses of the grown crystal were carried out using thermo gravimetric-differential thermal analysis (TG-DTA) and differential scanning calorimetry (DSC) curves. Optical (UV-vis-NIR) analysis shows that the grown crystals were found to be transparent (450-2500 nm) in the entire visible region. The existence of second harmonic generation signals was observed by using Nd:YAG laser with fundamental wavelength of 1064 nm.

  4. Tunable second harmonic generation of monolayer MoS2 by Se doping

    NASA Astrophysics Data System (ADS)

    Le, C. T.; Clark, D. J.; Senthilkumar, V.; Jang, J. I.; Cho, H.-Y.; Kim, Y. S.; Binghamton University Collaboration

    As a transition metal dichalcogenides whose bandgap becomes direct with inversion symmetry breaking in the monolayer limit, MoS2 has been getting ample attention as next-generation nonlinear optic material for its strong optical nonlinear properties. In this study, we demonstrate the wavelength second harmonic generation tunability of monolayer Mo(S, Se)2. Employing the two-zone furnaces system, we selenized as-grown monolayer MoS2at different temperature. X-ray photoluminescence spectroscopy was used to confirm the chemical composition of selenized film. Photoluminescence spectra shows the red shift in optical bandgap from 1.83 to 1.53 eV as a function of concentration Se replacing S. Second harmonic generation characteristics were measured in reflection geometry using ps pulse from Nd:YAG laser. Applying the previous bulk model, we calculated that the maximum value of χ (2)varied from ~40 pm/V for pure MoS2 to ~100 pm/V for pure MoSe2.We believe that our findings along with the ability to stack different 2D materials will create stacked 2D heterostructure with high χ (2)over a wide range of wavelength from visible to NIR. This research was supported by Priority Research Centers Program (2009-0093818), the Basic Science Research Program (2015-019609), and Basic Research Lab Program (2014-071686) through the National Research Foundation of Korea (NRF), funded by the Korean g.

  5. Second-harmonic generation in metallic nanoparticles: Clarification of the role of the surface

    NASA Astrophysics Data System (ADS)

    Ciracì, Cristian; Poutrina, Ekaterina; Scalora, Michael; Smith, David R.

    2012-09-01

    We present a numerical investigation of the second-order nonlinear optical properties of metal-based metamaterial nanoresonators. The nonlinear optical response of the metal is described by a hydrodynamic model, with the effects of electron pressure in the electron gas also taken into account. We show that as the pressure term tends to zero the amount of converted second-harmonic field tends to an asymptotic value. In this limit it becomes possible to rewrite the nonlinear surface contributions as functions of the value of the polarization vector inside the bulk region. Nonlocality thus can be incorporated into numerical simulations without actually utilizing the nonlocal equation of motion or solving for the rapidly varying fields that occur near the metal surface. We use our model to investigate the second-harmonic generation process with three-dimensional gold nanoparticle arrays and show that nanocrescents can easily attain conversion efficiencies of ˜6.0×10-8 for pumping peak intensities of a few tens of MW/cm2.

  6. Electrical control of second-harmonic generation in a WSe2 monolayer transistor

    DOE PAGES

    Seyler, Kyle L.; Schaibley, John R.; Gong, Pu; ...

    2015-04-20

    Nonlinear optical frequency conversion, in which optical fields interact with a nonlinear medium to produce new field frequencies, is ubiquitous in modern photonic systems. However, the nonlinear electric susceptibilities that give rise to such phenomena are often challenging to tune in a given material and, so far, dynamical control of optical nonlinearities remains confined to research laboratories as a spectroscopic tool. In this paper, we report a mechanism to electrically control second-order optical nonlinearities in monolayer WSe2, an atomically thin semiconductor. We show that the intensity of second-harmonic generation at the A-exciton resonance is tunable by over an order ofmore » magnitude at low temperature and nearly a factor of four at room temperature through electrostatic doping in a field-effect transistor. Such tunability arises from the strong exciton charging effects in monolayer semiconductors, which allow for exceptional control over the oscillator strengths at the exciton and trion resonances. The exciton-enhanced second-harmonic generation is counter-circularly polarized to the excitation laser due to the combination of the two-photon and one-photon valley selection rules, which have opposite helicity in the monolayer. Finally, our study paves the way towards a new platform for chip-scale, electrically tunable nonlinear optical devices based on two-dimensional semiconductors.« less

  7. Electrical control of second-harmonic generation in a WSe2 monolayer transistor

    SciTech Connect

    Seyler, Kyle L.; Schaibley, John R.; Gong, Pu; Rivera, Pasqual; Jones, Aaron M.; Wu, Sanfeng; Yan, Jiaqiang; Mandrus, David G.; Yao, Wang; Xu, Xiaodong

    2015-04-20

    Nonlinear optical frequency conversion, in which optical fields interact with a nonlinear medium to produce new field frequencies, is ubiquitous in modern photonic systems. However, the nonlinear electric susceptibilities that give rise to such phenomena are often challenging to tune in a given material and, so far, dynamical control of optical nonlinearities remains confined to research laboratories as a spectroscopic tool. In this paper, we report a mechanism to electrically control second-order optical nonlinearities in monolayer WSe2, an atomically thin semiconductor. We show that the intensity of second-harmonic generation at the A-exciton resonance is tunable by over an order of magnitude at low temperature and nearly a factor of four at room temperature through electrostatic doping in a field-effect transistor. Such tunability arises from the strong exciton charging effects in monolayer semiconductors, which allow for exceptional control over the oscillator strengths at the exciton and trion resonances. The exciton-enhanced second-harmonic generation is counter-circularly polarized to the excitation laser due to the combination of the two-photon and one-photon valley selection rules, which have opposite helicity in the monolayer. Finally, our study paves the way towards a new platform for chip-scale, electrically tunable nonlinear optical devices based on two-dimensional semiconductors.

  8. Protein conformation and molecular order probed by second-harmonic-generation microscopy

    NASA Astrophysics Data System (ADS)

    Vanzi, Francesco; Sacconi, Leonardo; Cicchi, Riccardo; Pavone, Francesco S.

    2012-06-01

    Second-harmonic-generation (SHG) microscopy has emerged as a powerful tool to image unstained living tissues and probe their molecular and supramolecular organization. In this article, we review the physical basis of SHG, highlighting how coherent summation of second-harmonic response leads to the sensitivity of polarized SHG to the three-dimensional distribution of emitters within the focal volume. Based on the physical description of the process, we examine experimental applications for probing the molecular organization within a tissue and its alterations in response to different biomedically relevant conditions. We also describe the approach for obtaining information on molecular conformation based on SHG polarization anisotropy measurements and its application to the study of myosin conformation in different physiological states of muscle. The capability of coupling the advantages of nonlinear microscopy (micrometer-scale resolution in deep tissue) with tools for probing molecular structure in vivo renders SHG microscopy an extremely powerful tool for the advancement of biomedical optics, with particular regard to novel technologies for molecular diagnostic in vivo.

  9. Significance of accurate diffraction corrections for the second harmonic wave in determining the acoustic nonlinearity parameter

    SciTech Connect

    Jeong, Hyunjo; Zhang, Shuzeng; Li, Xiongbing; Barnard, Dan

    2015-09-15

    The accurate measurement of acoustic nonlinearity parameter β for fluids or solids generally requires making corrections for diffraction effects due to finite size geometry of transmitter and receiver. These effects are well known in linear acoustics, while those for second harmonic waves have not been well addressed and therefore not properly considered in previous studies. In this work, we explicitly define the attenuation and diffraction corrections using the multi-Gaussian beam (MGB) equations which were developed from the quasilinear solutions of the KZK equation. The effects of making these corrections are examined through the simulation of β determination in water. Diffraction corrections are found to have more significant effects than attenuation corrections, and the β values of water can be estimated experimentally with less than 5% errors when the exact second harmonic diffraction corrections are used together with the negligible attenuation correction effects on the basis of linear frequency dependence between attenuation coefficients, α{sub 2} ≃ 2α{sub 1}.

  10. Texture analysis applied to second harmonic generation image data for ovarian cancer classification

    NASA Astrophysics Data System (ADS)

    Wen, Bruce L.; Brewer, Molly A.; Nadiarnykh, Oleg; Hocker, James; Singh, Vikas; Mackie, Thomas R.; Campagnola, Paul J.

    2014-09-01

    Remodeling of the extracellular matrix has been implicated in ovarian cancer. To quantitate the remodeling, we implement a form of texture analysis to delineate the collagen fibrillar morphology observed in second harmonic generation microscopy images of human normal and high grade malignant ovarian tissues. In the learning stage, a dictionary of "textons"-frequently occurring texture features that are identified by measuring the image response to a filter bank of various shapes, sizes, and orientations-is created. By calculating a representative model based on the texton distribution for each tissue type using a training set of respective second harmonic generation images, we then perform classification between images of normal and high grade malignant ovarian tissues. By optimizing the number of textons and nearest neighbors, we achieved classification accuracy up to 97% based on the area under receiver operating characteristic curves (true positives versus false positives). The local analysis algorithm is a more general method to probe rapidly changing fibrillar morphologies than global analyses such as FFT. It is also more versatile than other texture approaches as the filter bank can be highly tailored to specific applications (e.g., different disease states) by creating customized libraries based on common image features.

  11. Exact iterative solution of second harmonic generation in quasi-phase-matched structures.

    PubMed

    Ren, Ming-Liang; Li, Zhi-Yuan

    2010-03-29

    A versatile and accurate approach that combines a numerical iteration technique and a transfer-matrix method (TMM) is developed to solve the general problem of second harmonic generation (SHG) with pump depletion in quasi-phase-matched (QPM) nonlinear optical structures. We derive the iterative formulae from the nonlinear coupled wave equations and obtain the intensity distribution of fundamental wave and second harmonic wave by TMM. The approach shows quick numerical convergence of iteration and maintains perfect conservation of total energy. The simulation results show that the model coincides with the one under undepleted pump approximation very well when the SHG efficiency is small (well below 15%) and agrees very well with the effective nonlinear susceptibility model in handling general SHG problems even when the conversion efficiency is high up to 100%. Our method is applicable to general nonlinear optical structures, such as periodic, quasi-periodic, and aperiodic QPM structures, photonic crystals, and micro-cavities that might involve complicated modulation on the linear and nonlinear susceptibility.

  12. Propagation dynamics and X-pulse formation in phase-mismatched second-harmonic generation

    SciTech Connect

    Valiulis, G.; Jukna, V.; Jedrkiewicz, O.; Clerici, M.; Rubino, E.; DiTrapani, P.

    2011-04-15

    This paper concerns the theoretical, numerical, and experimental study of the second-harmonic-generation (SHG) process under conditions of phase and group-velocity mismatch and aims to demonstrate the dimensionality transition of the SHG process caused by the change of the fundamental wave diameter. We show that SHG from a narrow fundamental beam leads to the spontaneous self-phase-matching process with, in addition, the appearance of angular dispersion for the off-axis frequency components generated. The angular dispersion sustains the formation of the short X pulse in the second harmonic (SH) and is recognized as three-dimensional (3D) dynamics. On the contrary, the large-diameter fundamental beam reduces the number of the degrees of freedom, does not allow the generation of the angular dispersion, and maintains the so-called one-dimensional (1D) SHG dynamics, where the self-phase-matching appears just for axial components and is accompanied by the shrinking of the SH temporal bandwidth, and sustains a long SH pulse formation. The transition from long SH pulse generation typical of the 1D dynamics to the short 3D X pulse is illustrated numerically and experimentally by changing the conditions from the self-defocusing to the self-focusing regime by simply tuning the phase mismatch. The numerical and experimental verification of the analytical results are also presented.

  13. Second harmonic generation in nanoscale films of transition metal dichalcogenide: Accounting for multipath interference

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    The transfer matrix method has been widely used to calculate wave propagation through the layered structures consisting entirely of either linear or nonlinear optical materials. In the present work, we develop the transfer matrix method for structures consisting of alternating layers of linear and nonlinear optical materials. The result is presented in a form that allows one to directly substitute the values of material constants, refractive index and absorption coefficient, into the expressions describing the second harmonic generation (SHG) field. The model is applied to the calculation of second harmonic (SH) field generated in nano-thin layers of transition metal dichalcogenides exfoliated on top of silicon oxide/silicon Fabry-Perot cavity. These structures are intensively studied both in view of their unique properties and perspective applications. A good agreement between experimental and numerical results can be achieved by small modification of optical constants, which may arise in an experiment due to a strong electric field of an incident focused pump laser beam. By considering the SHG effect, this paper completes the series of works describing the role of Fabry-Perot cavity in different optical effects (optical reflection, photoluminescence and Raman scattering) in 2D semiconductors that is extremely important for characterization of these unique materials.

  14. Measurement of attenuation coefficients of the fundamental and second harmonic waves in water

    NASA Astrophysics Data System (ADS)

    Zhang, Shuzeng; Jeong, Hyunjo; Cho, Sungjong; Li, Xiongbing

    2016-02-01

    Attenuation corrections in nonlinear acoustics play an important role in the study of nonlinear fluids, biomedical imaging, or solid material characterization. The measurement of attenuation coefficients in a nonlinear regime is not easy because they depend on the source pressure and requires accurate diffraction corrections. In this work, the attenuation coefficients of the fundamental and second harmonic waves which come from the absorption of water are measured in nonlinear ultrasonic experiments. Based on the quasilinear theory of the KZK equation, the nonlinear sound field equations are derived and the diffraction correction terms are extracted. The measured sound pressure amplitudes are adjusted first for diffraction corrections in order to reduce the impact on the measurement of attenuation coefficients from diffractions. The attenuation coefficients of the fundamental and second harmonics are calculated precisely from a nonlinear least squares curve-fitting process of the experiment data. The results show that attenuation coefficients in a nonlinear condition depend on both frequency and source pressure, which are much different from a linear regime. In a relatively lower drive pressure, the attenuation coefficients increase linearly with frequency. However, they present the characteristic of nonlinear growth in a high drive pressure. As the diffraction corrections are obtained based on the quasilinear theory, it is important to use an appropriate source pressure for accurate attenuation measurements.

  15. Quantitative second-harmonic generation imaging to detect osteogenesis imperfecta in human skin samples

    NASA Astrophysics Data System (ADS)

    Adur, J.; Ferreira, A. E.; D'Souza-Li, L.; Pelegati, V. B.; de Thomaz, A. A.; Almeida, D. B.; Baratti, M. O.; Carvalho, H. F.; Cesar, C. L.

    2012-03-01

    Osteogenesis Imperfecta (OI) is a genetic disorder that leads to bone fractures due to mutations in the Col1A1 or Col1A2 genes that affect the primary structure of the collagen I chain with the ultimate outcome in collagen I fibrils that are either reduced in quantity or abnormally organized in the whole body. A quick test screening of the patients would largely reduce the sample number to be studied by the time consuming molecular genetics techniques. For this reason an assessment of the human skin collagen structure by Second Harmonic Generation (SHG) can be used as a screening technique to speed up the correlation of genetics/phenotype/OI types understanding. In the present work we have used quantitative second harmonic generation (SHG) imaging microscopy to investigate the collagen matrix organization of the OI human skin samples comparing with normal control patients. By comparing fibril collagen distribution and spatial organization, we calculated the anisotropy and texture patterns of this structural protein. The analysis of the anisotropy was performed by means of the two-dimensional Discrete Fourier Transform and image pattern analysis with Gray-Level Co-occurrence Matrix (GLCM). From these results, we show that statistically different results are obtained for the normal and disease states of OI.

  16. A 0.33-THz second-harmonic frequency-tunable gyrotron

    NASA Astrophysics Data System (ADS)

    Zheng-Di, Li; Chao-Hai, Du; Xiang-Bo, Qi; Li, Luo; Pu-Kun, Liu

    2016-02-01

    Dynamics of the axial mode transition process in a 0.33-THz second-harmonic gyrotron is investigated to reveal the physical mechanism of realizing broadband frequency tuning in an open cavity circuit. A new interaction mechanism about propagating waves, featured by wave competition and wave cooperation, is presented and provides a new insight into the beam-wave interaction. The two different features revealed in the two different operation regions of low-order axial modes (LOAMs) and high-order axial modes (HOAMs) respectively determine the characteristic of the overall performance of the device essentially. The device performance is obtained by the simulation based on the time-domain nonlinear theory and shows that using a 12-kV/150-mA electron beam and TE-3,4 mode, the second harmonic gyrotron can generate terahertz radiations with frequency-tuning ranges of about 0.85 GHz and 0.60 GHz via magnetic field and beam voltage tuning, respectively. Additionally, some non-stationary phenomena in the mode startup process are also analyzed. The investigation in this paper presents guidance for future developing high-performance frequency-tunable gyrotrons toward terahertz applications. Project supported by the National Natural Science Foundation of China (Grant Nos. 61471007, 61531002, 61522101, and 11275206) and the Seeding Grant for Medicine and Information Science of Peking University, China (Grant No. 2014-MI-01).

  17. Quantitative differentiation of normal and scarred tissues using second-harmonic generation microscopy.

    PubMed

    Yildirim, Murat; Quinn, Kyle P; Kobler, James B; Zeitels, Steven M; Georgakoudi, Irene; Ben-Yakar, Adela

    2016-11-01

    The aim of this study was to differentiate normal and scarred hamster cheek pouch samples by applying a quantitative image analysis technique for determining collagen fiber direction and density in second-harmonic generation microscopy images. This paper presents a collagen tissue analysis of scarred cheek pouches of four adult male Golden Syrian hamsters as an animal model for vocal fold scarring. One cheek pouch was scarred using an electrocautery unit and the other cheek was used as a control for each hamster. A home-built upright microscope and a compact ultrafast fiber laser were used to acquire depth resolved epi-collected second-harmonic generation images of collagen fibers. To quantify the average fiber direction and fiber density in each image, we applied two-dimensional Fourier analysis and intensity thresholding at five different locations for each control and scarred tissue sample, respectively. The resultant depth-resolved average fiber direction variance for scarred hamster cheek pouches (0.61 ± 0.03) was significantly lower (p < 0.05) than control tissue (0.73 ± 0.04), indicating increased fiber alignment within the scar. Depth-resolved average voxel density measurements indicated scarred tissues contained greater (p < 0.005) fiber density (0.72 ± 0.09) compared to controls (0.18 ± 0.03). In the present study, image analysis of both fiber alignment and density from depth-resolved second-harmonic generation images in epi-detection mode enabled the quantification of the increased collagen fiber deposition and alignment typically observed in fibrosis. The epi-detection geometry is the only viable method for in vivo imaging as well as imaging thick turbid tissues. These quantitative endpoints, clearly differentiating between control and scarred hamster cheek pouches, provide an objective means to characterize the extent of vocal fold scarring in vivo in preclinical and clinical research. In particular, this non-invasive method

  18. Second-harmonic generation from bimetal composites doped with metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Daneshfar, Nader

    2016-05-01

    In the present paper, we study the nonlinear optical response of the bimetal composites doped with metal nanoparticles in the framework of nonlinear Mie theory combined with the Maxwell-Garnett model. We concentrate on the second-order harmonic generation from bimetal nanocomposites including silver and gold particles, since sometimes the nonlinear optical response is sensitive to the more accurate of material structure than linear optical response. We show that optical second harmonic generation is strongly sensitive to temperature as an environmental parameter, interparticle plasmon coupling between Au and Ag nanoparticles (the filling factor of inclusions), the particle size and the surrounding medium. However, this work shows good potential of bimetal composites for nonlinear optics at the nanoscale.

  19. Modal engineering of second-harmonic generation in single GaP nanopillars.

    PubMed

    Sanatinia, Reza; Anand, Srinivasan; Swillo, Marcin

    2014-09-10

    We report on modal dispersion engineering for second-harmonic generation (SHG) from single vertical GaP nanopillars/nanowaveguides, fabricated by a top-down approach, using optical modal overlap between the pump (830 nm) and SHG (415 nm). We present a modal analysis for the SHG process in GaP nanopillars and demonstrate efficient utilization of the longitudinal component of the nonlinear polarization density. Our SHG measurements show quantitatively the presented model. We experimentally demonstrate that polarization beam shaping and field distribution modification of the radiated SHG light, at nanometer scale, can be achieved by tuning the pillar diameter and linear pump polarization. SHG from single pillars can be used as femtosecond nanoscopic light sources at visible wavelengths applicable for single cell/molecular imaging and interesting for future integrated nanophotonics components. While this work focuses on GaP nanopillars, the results are applicable to other semiconductor nanowire materials and synthesis methods.

  20. Functional second harmonic generation microscopy probes molecular dynamics with high temporal resolution

    PubMed Central

    Förderer, Moritz; Georgiev, Tihomir; Mosqueira, Matias; Fink, Rainer H. A.; Vogel, Martin

    2016-01-01

    Second harmonic generation (SHG) microscopy is a powerful tool for label free ex vivo or in vivo imaging, widely used to investigate structure and organization of endogenous SHG emitting proteins such as myosin or collagen. Polarization resolved SHG microscopy renders supplementary information and is used to probe different molecular states. This development towards functional SHG microscopy is calling for new methods for high speed functional imaging of dynamic processes. In this work we present two approaches with linear polarized light and demonstrate high speed line scan measurements of the molecular dynamics of the motor protein myosin with a time resolution of 1 ms in mammalian muscle cells. Such a high speed functional SHG microscopy has high potential to deliver new insights into structural and temporal molecular dynamics under ex vivo or in vivo conditions. PMID:26977360

  1. A linear algorithm for quantitative measure of corneal collagen fiber orientation using second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    McLean, James; DiMarzio, Charles

    2016-03-01

    There is significant interest in the scientific community to develop a reliable and precise quantification of the direction of collagen fibers within the cornea in order to learn more about how collagen contributes to the cornea's shape and structure. Previous work has shown that quantification of these fibers' orientations is possible using Second Harmonic Generation (SHG) microscopy, a modality that utilizes the non-centrosymmetric properties of collagen to obtain details of their macromolecular structure. Many attempts at using SHG to this purpose result in whole volume approximations which do not take into account variations through the depth of the cornea. Additionally, other algorithms have used non-linear processes which limit computation time and result in sensitivity to sample area, resolution, and illumination. We propose a linear method for quantification of collagen fiber orientation which utilizes the precise sectioning properties of SHG and is independent of non-linear artifacts to aid in further classification of cornea structure.

  2. Second harmonic generation of diamond-blade diced KTiOPO4 ridge waveguides.

    PubMed

    Chen, Chen; Rüter, Christian E; Volk, Martin F; Chen, Cheng; Shang, Zhen; Lu, Qingming; Akhmadaliev, Shavkat; Zhou, Shengqiang; Chen, Feng; Kip, Detlef

    2016-07-25

    We report on the fabrication of ridge waveguides in KTiOPO4 nonlinear optical crystals through carbon ion irradiation followed by precise diamond blade dicing. The diced side-walls have low roughness, which allows for low propagation loss of ~1dB/cm in fabricated of ridges. The waveguide property investigation has been performed at 1064 nm as well as 532 nm, showing good guidance at both TE and TM polarizations. Based on type II phase matching configuration, efficient second harmonic generation of green light at room temperature has been realized. High conversion efficiencies of ~1.12%W-1 and ~12.4% have been obtained for frequency doubling under the pump of continuous-wave (CW) and pulsed fundamental waves at 1064 nm, respectively.

  3. In situ observation of collagen thermal denaturation by second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Liao, C.-S.; Zhuo, Z.-Y.; Yu, J.-Y.; Chao, P.-H. G.; Chu, S.-W.

    2010-02-01

    Collagen denaturation is of fundamental importance for clinical treatment. Conventionally, the denaturation process is quantified by the shrinkage of collagen fibers, but the underlying molecular origin has not been fully understood. Since second harmonic generation (SHG) is related to the molecular packing of the triple helix in collagen fibers, this nonlinear signal provides an insight of molecular dynamics during thermal denaturation. With the aid of SHG microscopy, we found a new step in collagen thermal denaturation process, de-crimp. During the de-crimp step, the characteristic crimp pattern of collagen fascicles disappeared due to the breakage of interconnecting bonds between collagen fibrils, while SHG intensity remained unchanged, suggesting the intactness of the triple helical molecules. At higher temperature, shrinkage is observed with strongly reduced SHG intensity, indicating denaturation at the molecular level.

  4. Molecular Order of Arterial Collagen Using Circular Polarization Second-Harmonic Generation Imaging

    PubMed Central

    Turcotte, Raphaël; Mattson, Jeffrey M.; Wu, Juwell W.; Zhang, Yanhang; Lin, Charles P.

    2016-01-01

    Second-harmonic generation (SHG) originates from the interaction between upconverted fields from individual scatterers. This renders SHG microscopy highly sensitive to molecular distribution. Here, we aim to take advantage of the difference in SHG between aligned and partially aligned molecules to probe the degree of molecular order during biomechanical testing, independently of the absolute orientation of the scattering molecules. Toward this goal, we implemented a circular polarization SHG imaging approach and used it to quantify the intensity change associated with collagen fibers straightening in the arterial wall during mechanical stretching. We were able to observe the delayed alignment of collagen fibers during mechanical loading, thus demonstrating a simple method to characterize molecular distribution using intensity information alone. PMID:26806883

  5. Macroscopic control of quantum paths in high order harmonics by a weak second harmonic field.

    PubMed

    Wang, Shaoyi; Zhang, Qingbin; Hong, Weiyi; Zhu, Xiaosong; Lu, Peixiang

    2011-12-05

    The phase matching of quantum paths in high-order harmonic generation is investigated in a two-color laser field. Our results show that the phase-matching properties of the short and long trajectories can be modulated effectively by adding a weak second harmonic field. This scheme can not only achieve the quantum path selection, but more importantly it can achieve on-axis phase matching for both of the two trajectories simultaneously. A bright interference pattern induced by the simultaneously phase-matched two trajectories can be observed by placing a near-field on-axis filter, which has great potential for experimentally characterizing the full single-atom dipole moment.

  6. Two-Photon Luminescence and Second Harmonic Generation from Gold Micro-Plates

    PubMed Central

    Wang, Xu; Shi, Hao; Wang, Naiyin; Cheng, Lianghui; Gao, Ying; Huang, Lu; Jiang, Yuqiang

    2014-01-01

    Micron-sized gold plates were prepared by reducing chloroauric acid with lemongrass extract. Their two-photon luminescence (TPL) and second harmonic generation (SHG) were investigated. The results show that the TPL and SHG intensity of gold plates is dependent on the wavelength and polarization of excitation laser. The TPL intensity of gold plates decreases with the increase of the excitation wavelength except for a small peak around 820–840 nm, while SHG intensity increases with the excitation wavelength redshift. In addition, it is found that the TPL intensity of the gold plate’s edge is related with the angle between the edge orientation and the polarization direction of the excitation light. The TPL intensity increases with the angle increase from 0° to 90°. PMID:25268923

  7. Plasmon assisted enhanced second-harmonic generation in single hybrid Au/ZnS nanowires

    NASA Astrophysics Data System (ADS)

    Jassim, Nadia M.; Wang, Kai; Han, Xiaobo; Long, Hua; Wang, Bing; Lu, Peixiang

    2017-02-01

    We demonstrate the enhanced second-harmonic generation (SHG) in single ZnS nanowires (NWs) attached with gold nanoparticles (Au NPs). The hybrid Au/ZnS NWs with different densities of the attached Au NPs were prepared by a simple solution impregnation method. By comparing with bare ZnS NWs, ∼1.3, ∼6.6, ∼7 and ∼2 times enhancement of SH intensity was achieved in the hybrid Au/ZnS NWs with low, moderate, high and ultrahigh densities of the attached Au NPs, respectively. The enhanced SHG in the hybrid Au/ZnS NWs is attributed to the strong local-fields from the Au cluster under the near-resonant condition, which is supported by the related dark-field scattering spectra. This hybrid Au/ZnS NWs provide a simple platform for enhancing nonlinear optical responses, which have potential applications in nano-probing and nano-sensing.

  8. Visualization of collagen regeneration in mouse dorsal skin using second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Luo, T.; Chen, J. X.; Zhuo, S. M.; Lu, K. C.; Jiang, X. S.; Liu, Q. G.

    2009-03-01

    The purpose of this study is to highlight a clearer understanding of the process of collagen regeneration during wound healing. By means of second harmonic generation (SHG) microscopy, the changes of collagen arrangement at the wound margin were analyzed at 0, 3, 5, 7, 11 and 13 days post injury. The degree of collagen disorders associated with the healing process was quantitatively obtained using the aspect ratio of polar plot image of collagen azimuthal angles and the healing status of collagen could be estimated by arithmetical mean deviation ( Ra) of the collagen SHG images. Our results suggest that SHG microscopy has potential advances in the collagen studies during wound healing and the arrangement of collagen fibers gradually transformed from disorder to order so as to contract the wound. It is capable of promoting clinical application of the noninvasive imaging tool and the analysis methods of collagen disorder as an effective scar management for prevention and treatment about aberrant healing.

  9. Imaging Fibrosis and Separating Collagens using Second Harmonic Generation and Phasor Approach to Fluorescence Lifetime Imaging

    PubMed Central

    Ranjit, Suman; Dvornikov, Alexander; Stakic, Milka; Hong, Suk-Hyun; Levi, Moshe; Evans, Ronald M.; Gratton, Enrico

    2015-01-01

    In this paper we have used second harmonic generation (SHG) and phasor approach to auto fluorescence lifetime imaging (FLIM) to obtain fingerprints of different collagens and then used these fingerprints to observe bone marrow fibrosis in the mouse femur. This is a label free approach towards fast automatable detection of fibrosis in tissue samples. FLIM has previously been used as a method of contrast in different tissues and in this paper phasor approach to FLIM is used to separate collagen I from collagen III, the markers of fibrosis, the largest groups of disorders that are often without any effective therapy. Often characterized by an increase in collagen content of the corresponding tissue, the samples are usually visualized by histochemical staining, which is pathologist dependent and cannot be automated. PMID:26293987

  10. Quantitative analysis of thermally-induced alterations of corneal stroma by second-harmonic generation imaging

    NASA Astrophysics Data System (ADS)

    Matteini, P.; Rossi, F.; Ratto, F.; Cicchi, R.; Kapsokalyvas, D.; Pavone, F. S.; Pini, R.

    2010-02-01

    Thermal modifications induced in the corneal stroma were investigated by means of second harmonic generation (SHG) imaging. Whole fresh cornea samples were heated in a water bath at temperatures in the 35-80 °C range for a 4-min time. SHG images of the structural modifications induced at each temperature were acquired from different areas of cross-sectioned corneal stroma by using an 880 nm linearly- and circularly-polarized excitation light emitted by a mode-locked Ti:Sapphire laser. The SHG images were then analyzed by means of both an empirical approach and a 2D-theoretical model. The proposed analyses provide a detailed description of the changes occurring in the structural architecture of the cornea during the thermal treatment. Our results allow us to depict a temperature-dependent biochemical model for the progressive destructuration occurring to collagen fibrils and nonfibrillar components of the stroma.

  11. Monitoring process of human keloid formation based on second harmonic generation imaging

    NASA Astrophysics Data System (ADS)

    Jiang, X. S.; Chen, S.; Chen, J. X.; Zhu, X. Q.; Zheng, L. Q.; Zhuo, S. M.; Wang, D. J.

    2011-09-01

    In this paper, the morphological variation of collagen among the whole dermis from keloid tissue was investigated using second harmonic generation (SHG) microscopy. In the deep dermis of keloids, collagen bundles show apparently regular gap. In the middle dermis, the collagen bundles are randomly oriented and loosely arranged in the pattern of fine mesh while the collagen bundles are organized in a parallel manner in the superficial dermis near the epidermis. The developed parameters COI and BD can be used to further quantitatively describe these changes. Our results demonstrate the potential of SHG microscopy to understand the formation process of human keloid scar at the cellular level through imaging collagen variations in different depth of dermis.

  12. Polarization-resolved second-harmonic generation imaging for liver fibrosis assessment without labeling

    NASA Astrophysics Data System (ADS)

    Lin, Jian; Pan, Shiying; Zheng, Wei; Huang, Zhiwei

    2013-10-01

    We apply the polarization-resolved second-harmonic generation (PR-SHG) microscopy to investigate the changes of collagen typings (type I vs type III) and collagen fibril orientations of liver tissue in bile-duct-ligation (BDL) rat models. The PR-SHG results show that the second-order susceptibility tensor ratios (χ31/χ15 and χ33/χ15) of collagen fibers increase with liver fibrotic progression after BDL surgery, reflecting an increase of the type III collagen component with the severity of liver fibrosis; and the square root of the collagen type III to type I ratio linearly correlates (R2 = 0.98) with histopathological scores. Furthermore, the collagen fibril orientations become more random with liver fibrosis transformation as compared to normal liver tissue. This work demonstrates that PR-SHG microscopy has the potential for label-free diagnosis and characterization of liver fibrosis based on quantitative analysis of collagen typings and fibril orientations.

  13. Acceleration of lithotripsy using cavitation bubbles induced by second-harmonic superimposition

    NASA Astrophysics Data System (ADS)

    Osuga, Masamizu; Yasuda, Jun; Jimbo, Hayato; Yoshizawa, Shin; Umemura, Shin-ichiro

    2016-07-01

    Shock wave lithotripsy potentially produces residual stone fragments too large to pass through ureters and significant injury to the normal tissue surrounding the stone. Previous works have shown that the collapse of cavitation bubbles induced by high-intensity focused ultrasound can produce small stone fragments via cavitation erosion. However, the erosion rate is hypothesized to be reduced by ultrasound attenuation by excessively generated bubble clouds. If so, it is important to generate the bubbles only on the stone surface. The effects of peak-negative-enhanced (PNE) and peak-positive-enhanced (PPE) waves obtained by second-harmonic superimposition were investigated to control cavitation bubbles. With the PNE waves, the bubbles were generated only on the stone surface and the maximum erosion rate was 232 ± 32 mg/min. All the fragments were smaller than 2 mm, which makes them pass through ureters naturally. The proposed method shows the potential to significantly improve the speed of lithotripsy.

  14. Second-harmonic generation imaging of collagen fibers in myocardium for atrial fibrillation diagnosis

    NASA Astrophysics Data System (ADS)

    Tsai, Ming-Rung; Chiu, Yu-Wei; Lo, Men Tzung; Sun, Chi-Kuang

    2010-03-01

    Atrial fibrillation (AF) is the most common irregular heart rhythm and the mortality rate for patients with AF is approximately twice the mortality rate for patients with normal sinus rhythm (NSR). Some research has indicated that myocardial fibrosis plays an important role in predisposing patients to AF. Therefore, realizing the relationship between myocardial collagen fibrosis and AF is significant. Second-harmonic generation (SHG) is an optically nonlinear coherent process to image the collagen network. We perform SHG microscopic imaging of the collagen fibers in the human atrial myocardium. Utilizing the SHG images, we can identify the differences in morphology and the arrangement of collagen fibers between NSR and AF tissues. We also quantify the arrangement of the collagen fibers using Fourier transform images and calculating the values of angle entropy. We indicate that SHG imaging, a nondestructive and reproducible method to analyze the arrangement of collagen fibers, can provide explicit information about the relationship between myocardial fibrosis and AF.

  15. Multimodal two-photon imaging using a second harmonic generation-specific dye

    PubMed Central

    Nuriya, Mutsuo; Fukushima, Shun; Momotake, Atsuya; Shinotsuka, Takanori; Yasui, Masato; Arai, Tatsuo

    2016-01-01

    Second harmonic generation (SHG) imaging can be used to visualize unique biological phenomena, but currently available dyes limit its application owing to the strong fluorescent signals that they generate together with SHG. Here we report the first non-fluorescent and membrane potential-sensitive SHG-active organic dye Ap3. Ap3 is photostable and generates SH signals at the plasma membrane with virtually no fluorescent signals, in sharp contrast to the previously used fluorescent dye FM4-64. When tested in neurons, Ap3-SHG shows linear membrane potential sensitivity and fast responses to action potentials, and also shows significantly reduced photodamage compared with FM4-64. The SHG-specific nature of Ap3 allows simultaneous and completely independent imaging of SHG signals and fluorescent signals from various reporter molecules, including markers of cellular organelles and intracellular calcium. Therefore, this SHG-specific dye enables true multimodal two-photon imaging in biological samples. PMID:27156702

  16. Enhancement of second harmonic generation in nanocrystalline SiC films based natural microcavities

    NASA Astrophysics Data System (ADS)

    Semenov, A. V.; Skorik, S. N.; Jedryka, J.; Ozga, K.; Kityk, I. V.

    2017-01-01

    We explore second harmonic generation (SHG) features of nanocrystalline SiC films based natural microcavities (MC) with resonance modes in the vicinity of the fundamental radiation at 1064 nm wavelength for nanocrystalline films of 24R, 27R polytypes characterized by high radiation doubling frequency coefficients. The natural walls of the SiC NC serve a role of cavities. To learn the nonlinear resonance features of the MC near the fundamental wavelength 1064 nm three series of the nc-SiC films indicated as 7495, 7517 and 7522 with thicknesses varying within 250-600 nm were fabricated. The role of the coherent and non-coherent contributions with taking into an account of cavity resonance modes is discussed. The giant increase of the SHG was achieved which may be used for further fabrication of the frequency transducers and nonlinear optical triggers.

  17. Enhancement of the second-harmonic generation in a quantum dot-metallic nanoparticle hybrid system

    NASA Astrophysics Data System (ADS)

    Singh, Mahi R.

    2013-03-01

    We have investigated the second-harmonic generation (SHG) and dipole-dipole interaction in a quantum dot and metallic nanoparticle hybrid system. A strong probe field is applied to create two-photon absorption in the quantum dot and metallic nanoparticle. SHG photons and SHG surface plasmon polaritons are emitted by the quantum dot and metallic nanoparticle, respectively. Induced dipoles are created in the quantum dot and the metallic nanoparticle due to two-photon absorption and hence both systems interact with each other via the dipole-dipole interaction. It is found that SHG signals produced by the quantum dot and nanoparticle are enhanced by the dipole-dipole interaction and also that the SHG signal can be switched on and off by applying a control field. The theoretical findings of this paper are supported by recent experimental studies. The present hybrid system can be used to fabricate nano-sensors and all-optical nano-switching devices.

  18. Exciton coupling model for the emergence of second harmonic generation from assemblies of centrosymmetric molecules.

    PubMed

    Snyder, Gregory R; Chowdhury, Azhad U; Simpson, Garth J

    2014-06-19

    A simple model is presented for interpreting the presence of substantial second harmonic generation (SHG) activity from assemblies of centrosymmetric molecular building blocks. Using butadiene as a computationally tractable centrosymmetric model system, time-dependent Hartree-Fock calculations of the nonlinear polarizability of butadiene dimer were well-described through exciton coupling arguments based on the electronic structure of the monomer and the relative orientation between the monomers within the dimer. Experimental studies of the centrosymmetric molecule 2,6-di-tert-butylanthraquinone suggest the formation of a combination of SHG-active and SHG-inactive crystal forms. The structure for the centrosymmetric form is known, serving as a negative control for the model, while the presence of an additional SHG-active metastable form is consistent with predictions of the model for alternative molecular packing configurations.

  19. Analysis of collagen fiber domain organization by Fourier second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Ghazaryan, Ara; Tsai, Halley F.; Hayrapetyan, Gor; Chen, Wei-Liang; Chen, Yang-Fang; Jeong, Myung Yung; Kim, Chang-Seok; Chen, Shean-Jen; Dong, Chen-Yuan

    2013-03-01

    We present an automated and systematic two-dimensional discrete Fourier transform (2D-FFT) approach to analyze collagen fiber organization through the use of second harmonic generation (SHG) microscopy. Average orientations of individual domains and Ising-like order parameters introduced to characterize the correlation between orientations of adjacent domains may be used to quantitatively characterize fibrous tissues. Our approach was applied to analyze tissues including rat tail tendon, mouse skin, bovine corneas, and human corneas. We also show that collagen fiber organization in normal and keratokonus human corneas may be distinguished. The current approach may be used for the quantitative differentiation of SHG collagen fiber morphology in different tissues and may be applied for diagnostic purposes.

  20. Second harmonic generation polarization microscopy with tightly focused linearly and radially polarized beams

    NASA Astrophysics Data System (ADS)

    Yew, E. Y. S.; Sheppard, C. J. R.

    2007-07-01

    Second harmonic generation microscopy was conducted on rat-tail tendons with linearly and radially polarized beams. Transverse and axial field components were generated in the focal region through tight focusing of linearly and radially polarized. It was found that the generated SHG signals could not be qualitatively explained with a scalar approximation to the electric field at the focus. Only by accounting for the interactions of the axial and transverse components of the electric field interacting through the nonlinear susceptibility χ(2) tensor could the SHG images be explained. For the case of collagen we find that the SHG signal varies as a function of the analyzer angle with a cos2 or sin2 dependency for linearly polarized beams. For tightly focused radially polarized beams we find that the output SHG is radially polarized after collimation and is independent of the analyzer angle.

  1. Monitoring the thermally induced structural transitions of collagen by use of second-harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Lin, Sung-Jan; Hsiao, Chih-Yuan; Sun, Yen; Lo, Wen; Lin, Wei-Chou; Jan, Gwo-Jen; Jee, Shiou-Hwa; Dong, Chen-Yuan

    2005-03-01

    The thermal disruption of collagen I in rat tail tendon is investigated with second-harmonic generation (SHG) microscopy. We investigate its effects on SHG images and intensity in the temperature range 25°-60°C. We find that the SHG signal decreases rapidly starting at 45°C. However, SHG imaging reveals that breakage of collagen fibers is not evident until 57°C and worsens with increasing temperature. At 57°C, structures of both molten and fibrous collagen exist, and the disruption of collagen appears to be complete at 60°C. Our results suggest that, in addition to intensity measurement, SHG imaging is necessary for monitoring details of thermally induced changes in collagen structures in biomedical applications.

  2. High sensitive translational temperature measurement using characteristic curve of second harmonic signal in wavelength modulation spectroscopy

    NASA Astrophysics Data System (ADS)

    Matsui, Makoto; Yamada, Tohru

    2017-01-01

    A high sensitive measurement system of translational temperature of plasma was developed. In this system, which is based on wavelength modulation spectroscopy, a peak value of second harmonic signal was measured as a function of modulation depth. The translational temperature was estimated by fitting the theoretically calculated curve to the measured characteristic curve. The performance of this system was examined using microwave discharge plasma. As a result of comparison with conventional laser absorption spectroscopy, both results show good agreement in the measurable region of the laser absorption spectroscopy. Next, the measurable limit of this system was investigated by decreasing the target number density. The detectable fractional absorption was as low as 3.7 × 10-5 in which condition the signal to noise ratio was the order of single digit at the averaging number of 40. This value is more than two orders of magnitude lower than that of the laser absorption spectroscopy.

  3. Silicon photonic crystal cavity enhanced second-harmonic generation from monolayer WSe2

    NASA Astrophysics Data System (ADS)

    Fryett, Taylor K.; Seyler, Kyle L.; Zheng, Jiajiu; Liu, Chang-Hua; Xu, Xiaodong; Majumdar, Arka

    2017-03-01

    Nano-resonators integrated with two-dimensional materials (e.g. transition metal dichalcogenides) have recently emerged as a promising nano-optoelectronic platform. Here we demonstrate resonator-enhanced second-harmonic generation (SHG) in tungsten diselenide using a silicon photonic crystal cavity. By pumping the device with ultrafast laser pulses near the cavity mode at the telecommunication wavelength, we observe a near visible SHG with a narrow linewidth and near unity linear polarization, originated from the coupling of the pump photon to the cavity mode. The observed SHG is enhanced by factor of ∼200 compared to a bare monolayer on silicon. Our results imply the efficacy of cavity integrated monolayer materials for nonlinear optics and the potential of building a silicon-compatible second-order nonlinear integrated photonic platform.

  4. Tuning the mapping of second-harmonic generation in silver nanoshells

    NASA Astrophysics Data System (ADS)

    Li, Z. J.; Gao, S. Y.; Han, D.

    2011-10-01

    The distribution patterns of the second-harmonic generation (SHG) enhancement factor in the incident plane of silver nanoshell at resonance frequencies have been studied by using electrostatic approximation. The mapping feature of SHG corresponding to double frequency local field enhancement is different from that of fundamental case. At longer wavelength (SHG enhancement resulting from local field at double frequency), large SHG enhancements are only observed outside the shell. However, hot spots also take place inside the silver shell at shorter wavelength (SHG enhancement resulting from local field at fundamental frequency). The effect of outer surrounding media on the SHG corresponding to local field at fundamental frequency is also very different from that of double frequency. It has been found that the azimuth angle dependent SHG at shorter wavelength split into two maximums when the surrounding dielectric constant is increased, which is absent for SHG at longer wavelength.

  5. Nanotwin Detection and Domain Polarity Determination via Optical Second Harmonic Generation Polarimetry.

    PubMed

    Ren, Ming-Liang; Agarwal, Rahul; Nukala, Pavan; Liu, Wenjing; Agarwal, Ritesh

    2016-07-13

    We demonstrate that optical second harmonic generation (SHG) can be utilized to determine the exact nature of nanotwins in noncentrosymmetric crystals, which is challenging to resolve via conventional transmission electron or scanned probe microscopies. Using single-crystalline nanotwinned CdTe nanobelts and nanowires as a model system, we show that SHG polarimetry can distinguish between upright (Cd-Te bonds) and inverted (Cd-Cd or Te-Te bonds) twin boundaries in the system. Inverted twin boundaries are generally not reported in nanowires due to the lack of techniques and complexity associated with the study of the nature of such defects. Precise characterization of the nature of defects in nanocrystals is required for deeper understanding of their growth and physical properties to enable their application in future devices.

  6. Second harmonic generation (SHG) and two-photon fluorescence (TPF) contrast imaging in biomaterial analysis

    NASA Astrophysics Data System (ADS)

    Lang, Xuye; Lyubovitsky, Julia

    2015-07-01

    Collagen hydrogels are natural biomaterials that comprise 3D networks of high water content and have viscoelastic properties and biocompatibility similar to native tissues. Consequently, these materials play an important role in tissue engineering and regenerative medicine for quite some time. Second harmonic generation (SHG) and two-photon fluorescence (TPF) contrasts transpire as valuable label-free spectroscopic probes for analysis of these biomaterials and this presentation will report the structural, mechanical and physicochemical parameters leading to the observed optical SHG and TPF effects in synthesized 3D collagen hydrogels. We will present results regarding understanding the dependency of collagen fiber formation on ion types, new results regarding strengthening of these biomaterials with a nontoxic chemical cross-linker genipin and polarization selection of collagen fibers' orientations.

  7. Surface plasmon-driven second-harmonic generation asymmetry in anisotropic plasmonic crystals

    NASA Astrophysics Data System (ADS)

    Chekhov, A. L.; Razdolski, I.; Kirilyuk, A.; Rasing, Th.; Stognij, A. I.; Murzina, T. V.

    2016-04-01

    We report a strong angular asymmetry of optical second-harmonic generation (SHG) in plasmonic crystals formed by an Au grating on top of an anisotropic bismuth-thulium iron garnet (BTIG) film. We found that a weak anisotropy-driven angular SHG asymmetry of the crystalline BTIG is resonantly enhanced and reaches 95% as the surface plasmon polariton (SPP) is excited at the Au/BTIG interface. The asymmetry introduced by an interference of the odd and even (with respect to the angle of incidence) SHG fields is attributed to the anisotropy of the BTIG film. The angular SHG spectra are reproduced using a simple model with a resonant SPP-induced SHG contribution from the anisotropic Au/BTIG interface. The observed asymmetry of the SHG provides valuable insight into the mechanisms of nonlinear plasmonics and can noticeably expand its abilities regarding active light conversion and manipulation.

  8. Second-harmonic microscopy of strain fields around through-silicon-vias

    NASA Astrophysics Data System (ADS)

    Cho, Yujin; Shafiei, Farbod; Mendoza, B. S.; Lei, Ming; Jiang, Tengfei; Ho, P. S.; Downer, M. C.

    2016-04-01

    Through-Silicon-Vias (TSVs)—10 μm-diameter conducting rods that connect vertically stacked silicon layers—provide three dimensional circuit integration, but introduce strain in the surrounding silicon when thermally cycled. Here, we noninvasively probe strain fields around Cu TSVs in Si(001) using optical second-harmonic generation (SHG) microscopy. Results are compared with micro-Raman spectra of the strained regions. We find that SHG probes strain fields more quickly than Raman spectroscopy, while maintaining comparable sensitivity and spatial resolution, and avoiding the need for spectral analysis. Moreover, SHG is selectively sensitive to axial shear components uiz (i = x, y) of the strain tensor that are often neglected in Raman analysis. Thus, SHG complements Raman spectroscopy.

  9. [Lycopene and beta-carotene content in tomato analyzed by the second harmonic].

    PubMed

    Ouyang, Shun-Li; Zhou, Mi; Cao, Biao; Men, Zhi-Wei; Gao, Shu-Qin; Li, Zuo-Wei; Lu, Guo-Hui; Yang, Jian-Ge

    2009-12-01

    Lycopene and beta-carotene are two important nutritional components in tomato. The main Raman spectrum group of lycopene and beta-carotene abundant in tomato is identical and difficult to be distinguished through fundamental frequency. With excitation wavelength of 514.5 nm, the excited light was just present in the half width range of the main absorption bands of Lycopene and beta-carotene, so the resonance Raman effect can occur. Based on resonance Raman spectra, by on-body measuring the second harmonic of stretching vibration of carbon-carbon conjugated double bond in lycopene and beta-carotene, the content of lycopene and beta-carotene can be obtained according to the integrated intensity of each component calculated by software. And this provides a method for on-body determining the content of the components with the homologous group.

  10. Polarization response of second-harmonic images for different collagen spatial distributions

    NASA Astrophysics Data System (ADS)

    Ávila, Francisco J.; del Barco, Oscar; Bueno, Juan M.

    2016-06-01

    The response to polarization of second-harmonic generation (SHG) microscopy images of samples with different collagen distributions (quasialigned, partially organized, and nonorganized) has been analyzed. A linear decay relationship between the external arrangement and polarization sensitivity was found. SHG signal from nonorganized samples presented a large structural dispersion and a weak dependence with incident polarization. Polarization dependence is also associated with the internal organization of the collagen fibers, directly related to the ratio of hyperpolarizabilities ρ. This parameter can experimentally be computed from the modulation of the SHG signal. The results show that both external and internal collagen structures are closely related. This provides a tool to obtain information of internal properties from the polarimetric response of the external spatial distribution of collagen, which might be useful in clinical diagnosis of pathologies related to changes in collagen structure.

  11. Large optical second harmonic generation in a low-bandgap polymer

    NASA Astrophysics Data System (ADS)

    Vanbel, Maarten K.; Vandendriessche, Stefaan; Willot, Pieter; Koeckelberghs, Guy; Verbiest, Thierry

    2014-10-01

    Recent research has focused on developing low-bandgap polymers for harvesting solar energy, fine-tuning desirable properties including power conversion efficiency, carrier mobilities and broad light absorption. However, little attention has been paid to their nonlinear optical properties. We characterized the optical second harmonic generation of corona poled films of poly(cyclopenta[2,1-b;3,4-b']dithiophen-4-ylidenedioctylmalonate). Despite being amorphous and lacking a typical donor-acceptor dye, these films display large nonlinear optical susceptibilities. Coupled with their stability and low absorption in the relevant wavelength region, these polymer films compare favorably to other materials. Our results show the promise of low-bandgap polymers for nonlinear optical applications.

  12. Enabling Multiphoton and Second Harmonic Generation Imaging in Paraffin-Embedded and Histologically Stained Sections

    PubMed Central

    Monaghan, Michael G.; Kroll, Sebastian; Brucker, Sara Y.

    2016-01-01

    Nonlinear microscopy, namely multiphoton imaging and second harmonic generation (SHG), is an established noninvasive technique useful for the imaging of extracellular matrix (ECM). Typically, measurements are performed in vivo on freshly excised tissues or biopsies. In this article, we describe the effect of rehydrating paraffin-embedded sections on multiphoton and SHG emission signals and the acquisition of nonlinear images from hematoxylin and eosin (H&E)-stained sections before and after a destaining protocol. Our results reveal that bringing tissue sections to a physiological state yields a significant improvement in nonlinear signals, particularly in SHG. Additionally, the destaining of sections previously processed with H&E staining significantly improves their SHG emission signals during imaging, thereby allowing sufficient analysis of collagen in these sections. These results are important for researchers and pathologists to obtain additional information from paraffin-embedded tissues and archived samples to perform retrospective analysis of the ECM or gain additional information from rare samples. PMID:27018844

  13. Observation of the second harmonic in Thomson scattering from relativistic electrons.

    PubMed

    Babzien, Marcus; Ben-Zvi, Ilan; Kusche, Karl; Pavlishin, Igor V; Pogorelsky, Igor V; Siddons, David P; Yakimenko, Vitaly; Cline, David; Zhou, Feng; Hirose, Tachishige; Kamiya, Yoshio; Kumita, Tetsuro; Omori, Tsunehiko; Urakawa, Junji; Yokoya, Kaoru

    2006-02-10

    A free relativistic electron in an electromagnetic field is a pure case of a light-matter interaction. In the laboratory environment, this interaction can be realized by colliding laser pulses with electron beams produced from particle accelerators. The process of single photon absorption and reemission by the electron, so-called linear Thomson scattering, results in radiation that is Doppler shifted into the x-ray and gamma-ray regions. At elevated laser intensity, nonlinear effects should come into play when the transverse motion of the electrons induced by the laser beam is relativistic. In the present experiment, we achieved this condition and characterized the second harmonic of Thomson x-ray scattering using the counterpropagation of a 60 MeV electron beam and a subterawatt CO2 laser beam.

  14. Observation of the Second Harmonic in Thomson Scattering from Relativistic Electrons

    NASA Astrophysics Data System (ADS)

    Babzien, Marcus; Ben-Zvi, Ilan; Kusche, Karl; Pavlishin, Igor V.; Pogorelsky, Igor V.; Siddons, David P.; Yakimenko, Vitaly; Cline, David; Zhou, Feng; Hirose, Tachishige; Kamiya, Yoshio; Kumita, Tetsuro; Omori, Tsunehiko; Urakawa, Junji; Yokoya, Kaoru

    2006-02-01

    A free relativistic electron in an electromagnetic field is a pure case of a light-matter interaction. In the laboratory environment, this interaction can be realized by colliding laser pulses with electron beams produced from particle accelerators. The process of single photon absorption and reemission by the electron, so-called linear Thomson scattering, results in radiation that is Doppler shifted into the x-ray and γ-ray regions. At elevated laser intensity, nonlinear effects should come into play when the transverse motion of the electrons induced by the laser beam is relativistic. In the present experiment, we achieved this condition and characterized the second harmonic of Thomson x-ray scattering using the counterpropagation of a 60 MeV electron beam and a subterawatt CO2 laser beam.

  15. Optimal second-harmonic generation in split-ring resonator arrays

    NASA Astrophysics Data System (ADS)

    Grynko, Yevgen; Meier, Torsten; Linden, Stefan; Niesler, Fabian B. P.; Wegener, Martin; Förstner, Jens

    2013-03-01

    Previous experimental measurements and numerical simulations give evidence of strong electric and magnetic field interaction between split-ring resonators in dense arrays. One can expect that such interactions have an influence on the second harmonic generation. We apply the Discontinuous Galerkin Time Domain method and the hydrodynamic Maxwell-Vlasov model to simulate the linear and nonlinear optical response from SRR arrays. The simulations show that dense placement of the constituent building blocks appears not always optimal and collective effects can lead to a significant suppression of the near fields at the fundamental frequency and, consequently, to the decrease of the SHG intensity. We demonstrate also the great role of the symmetry degree of the array layout which results in the variation of the SHG efficiency in range of two orders of magnitude.

  16. Effects of fundamental and second harmonic electron cyclotron resonances on ECRIS.

    PubMed

    Kato, Yushi; Satani, Takashi; Asaji, Toyohisa; Sato, Fuminobu; Iida, Toshiyuki

    2008-02-01

    A new concept on magnetic field of plasma production and confinement has been proposed to enhance efficiency of an electron cyclotron resonance (ECR) plasma for broad and dense ion beam source under the low pressure. The magnetic field configuration is constructed by a pair of comb-shaped magnet which has opposite polarity to each other, and which cylindrically surrounds the plasma chamber. This magnetic configuration suppresses the loss due to E x B drift, and then plasma confinement is enhanced. The profiles of the electron temperature and density are measured around the ECR zones of the fundamentals and the second harmonics for 2.45 GHz and 11-13 GHz microwaves by using Langmuir probe. Their characteristics and effects are clarified under various operating conditions in both of simple multipole and comb-shaped magnetic configurations.

  17. Conformation, orientation and interaction in molecular monolayers: A surface second harmonic and sum frequency generation study

    SciTech Connect

    Superfine, R.; Huang, J.Y.; Shen, Y.R.

    1988-12-01

    We have used sum frequency generation (SFG) to study the order in a silane monolayer before and after the deposition of a coadsorbed liquid crystal monolayer. We observe an increase in the order of the chain of the silane molecule induced by the interpenetration of the liquid crystal molecules. By using second harmonic generation (SHG) and SFG, we have studied the orientation and conformation of the liquid crystal molecule on clean and silane coated glass surfaces. On both surfaces, the biphenyl group is tilted by 70{degree} with the alkyl chain end pointing away from the surface. The shift in the C-H stretch frequencies in the coadsorbed system indicates a significant interaction between molecules. 9 refs., 3 figs.

  18. Second harmonic generation studies in L-alanine single crystals grown from solution

    NASA Astrophysics Data System (ADS)

    Boomadevi, Shanmugam; Pandiyan, Krishnamoorthy

    2014-01-01

    Single crystals of L-alanine of dimensions 2×1.1×0.5 cm3 were grown by evaporation method using deionised water as a solvent. The morphology of the grown crystals had (1 2 0) and (0 1 1) as their prominent faces. UV-vis-near IR spectrum shows the transparency range of L-alanine crystal available for frequency doubling from 250 to 1400 nm. Phase-matched second harmonic generation was observed in L-alanine sample by using 7 ns Q-switched Nd:YAG laser with OPO set up. In the present work, phase matching was achieved by angle and wavelength tuning. The angular and spectral phase-matching bandwidths were determined experimentally for a 1.5 mm thick L-alanine crystal and the results have been compared with their theoretical results. Further the possible reasons for the broadening of SHG spectrum have been discussed.

  19. Dynamical centrosymmetry breaking - A novel mechanism for second harmonic generation in graphene

    NASA Astrophysics Data System (ADS)

    Carvalho, David N.; Marini, Andrea; Biancalana, Fabio

    2017-03-01

    We discover an unusual phenomenon that occurs when a graphene monolayer is illuminated by a short and intense pulse at normal incidence. Due to the pulse-induced oscillations of the Dirac cones, a dynamical breaking of the layer's centrosymmetry takes place, leading to the generation of second harmonic waves. We prove that this result can only be found by using the full Dirac equation and show that the widely used semiconductor Bloch equations fail to reproduce this and some other important physics of graphene. Our results open new windows in the understanding of nonlinear light-matter interactions in a wide variety of new 2D materials with a gapped or ungapped Dirac-like dispersion.

  20. Analysis of spatial lamellar distribution from adaptive-optics second harmonic generation corneal images.

    PubMed

    Bueno, Juan M; Palacios, Raquel; Chessey, Mary K; Ginis, Harilaos

    2013-07-01

    The spatial organization of stromal collagen of ex-vivo corneas has been quantified in adaptive-optics second harmonic generation (SHG) images by means of an optimized Fourier transform (FT) based analysis. At a particular depth location, adjacent lamellae often present similar orientations and run parallel to the corneal surface. However this pattern might be combined with interweaved collagen bundles leading to crosshatched structures with different orientations. The procedure here reported provides us with both principal and crosshatched angles. This is also able to automatically distinguish a random distribution from a cross-shaped one, since it uses the ratio of the axes lengths of the best-fitted ellipse of the FT data as an auxiliary parameter. The technique has successfully been applied to SHG images of healthy corneas (both stroma and Bowman's layer) of different species and to corneas undergoing cross-linking treatment.

  1. Second harmonic generation imaging of the collagen in myocardium for atrial fibrillation diagnosis

    NASA Astrophysics Data System (ADS)

    Tsai, Ming-Rung; Chiou, Yu-We; Sun, Chi-Kuang

    2009-02-01

    Myocardial fibrosis, a common sequela of cardiac hypertrophy, has been shown to be associated with arrhythmias in experimental models. Some research has indicated that myocardial fibrosis plays an important role in predisposing patients to atrial fibrillation. Second harmonic generation (SHG) is an optically nonlinear coherent process to image the collagen network. In this presentation, we observe the SHG images of the collagen matrix in atrial myocardium and we analyzed of collagen fibers arrangement by using Fourier-transform analysis. Moreover, comparing the SHG images of the collagen fibers in atrial myocardium between normal sinus rhythm (NSR) and atrial fibrillation (AF), our result indicated that it is possible to realize the relation between myocardial fibrosis and AF.

  2. Second harmonic generation at the probe tip for background-free near-field optical imaging.

    PubMed

    Dong, Zhaogang; Soh, Yeng Chai

    2012-08-13

    Second harmonic generation (SHG) has been applied to reduce background signals in near-field optical imaging, but this technique is usually limited to samples with strong second-order nonlinear susceptibilities. To overcome this limitation, in this paper, we present a versatile background-free SHG configuration, where it utilizes the second-order nonlinear susceptibility of the probe which essentially functions as a near-field polarizer capable of filtering out the background signal component. In the theoretical analysis, we first model the probe-sample optical interactions at both the fundamental frequency and the second harmonic frequency by using the coupled dipole method. The theoretical model reveals that the proposed versatile background-free SHG configuration requires two conditions. The first condition is that the incident optical field must be s-polarized. The second condition is that the probe must be made of crystals from symmetry class 222, symmetry class 622, symmetry class 422, symmetry class 42m, symmetry class 43m or symmetry class 23. To demonstrate the effectiveness of the proposed versatile background-free SHG configuration, a probe made of deuterated potassium dideuterium phosphate (DKDP) crystal from symmetry class 42m is analyzed numerically. It is shown that when imaging samples with negligible second-order nonlinear susceptibilities, the proposed background-free SHG configuration improves the imaging contrast by more than one-order of magnitude as compared to all other imaging configurations. Moreover, we also investigate the dependence of its performance on other parameters, such as the probe-sample distance, the relative size between probe and sample, and the tilt angle of probe crystal. It is believed that the proposed configuration could be widely used to achieve high contrast near-field optical imaging.

  3. Three-layer model for the surface second-harmonic generation yield including multiple reflections

    NASA Astrophysics Data System (ADS)

    Anderson, Sean M.; Mendoza, Bernardo S.

    2016-09-01

    We present the three-layer model to calculate the surface second-harmonic generation (SSHG) yield. This model considers that the surface is represented by three regions or layers. The first layer is the vacuum region with a dielectric function ɛv(ω ) =1 from where the fundamental electric field impinges on the material. The second layer is a thin layer (ℓ ) of thickness d characterized by a dielectric function ɛℓ(ω ) , and it is in this layer where the SSHG takes place. The third layer is the bulk region denoted by b and characterized by ɛb(ω ) . Both the vacuum and bulk layers are semi-infinite. The model includes the multiple reflections of both the fundamental and the second-harmonic (SH) fields that take place at the thin layer ℓ . We obtain explicit expressions for the SSHG yield for the commonly used s and p polarizations of the incoming 1 ω and outgoing 2 ω electric fields, where no assumptions for the symmetry of the surface are made. These symmetry assumptions ultimately determine which components of the surface nonlinear second-order susceptibility tensor χ (-2 ω ;ω ,ω ) are different from zero, and thus contribute to the SSHG yield. Then, we particularize the results for the most commonly investigated surfaces, the (001), (110), and (111) crystallographic faces, taking their symmetries into account. We use the three-layer model and compare it against the experimental results of a Si(111)(1 ×1 ):H surface, as a test case, and use it to predict the SSHG yield of a Si(001)(2 ×1 ) surface.

  4. Electric-Field Switchable Second-Harmonic Generation in Bilayer MoS2 by Inversion Symmetry Breaking.

    PubMed

    Klein, J; Wierzbowski, J; Steinhoff, A; Florian, M; Rösner, M; Heimbach, F; Müller, K; Jahnke, F; Wehling, T O; Finley, J J; Kaniber, M

    2017-01-11

    We demonstrate pronounced electric-field-induced second-harmonic generation in naturally inversion symmetric 2H stacked bilayer MoS2 embedded into microcapacitor devices. By applying strong external electric field perturbations (|F| = ±2.6 MV cm(-1)) perpendicular to the basal plane of the crystal, we control the inversion symmetry breaking and, hereby, tune the nonlinear conversion efficiency. Strong tunability of the nonlinear response is observed throughout the energy range (Eω ∼ 1.25-1.47 eV) probed by measuring the second-harmonic response at E2ω, spectrally detuned from both the A- and B-exciton resonances. A 60-fold enhancement of the second-order nonlinear signal is obtained for emission at E2ω = 2.49 eV, energetically detuned by ΔE = E2ω - EC = -0.26 eV from the C-resonance (EC = 2.75 eV). The pronounced spectral dependence of the electric-field-induced second-harmonic generation signal reflects the bandstructure and wave function admixture and exhibits particularly strong tunability below the C-resonance, in good agreement with density functional theory calculations. Moreover, we show that the field-induced second-harmonic generation relies on the interlayer coupling in the bilayer. Our findings strongly suggest that the strong tunability of the electric-field-induced second-harmonic generation signal in bilayer transition metal dichalcogenides may find applications in miniaturized electrically switchable nonlinear devices.

  5. a Comparison of Different Coherent Deep Ultraviolet Generations Using Second Harmonic Generation with Blue Laser Diode Excitation

    NASA Astrophysics Data System (ADS)

    Tangtrongbenchasil, C.; Nonaka, K.

    2008-11-01

    Nano-focus beam applications of short wavelength approximately 220 nm now play important roles in engineering and industrial sections. At present, light sources at approximately 220 nm are commercially available but large size, difficult to maintain, and expensive. Compact wavelength tunable and cost effective light sources at approximately 220 nm are required. Laser diode with sum-frequency generation methods are employed to generated the shorter wavelength approximately 220 nm. This paper presents comparison of second harmonic generation schemes using a nonlinear optic crystal and two types of laser diode, which are a 440 nm single mode blue laser diode and a 450 nm multimode Fabry-Perot blue laser diode, has potential to generate wide tunable coherent deep ultraviolet-c at approximately 220 nm. Using the blue laser diode with the sum-frequency technique, a high second harmonic power is hardly observed due to low conversion efficiency. The best performance of second harmonic generation using blue laser diode, nonlinear optic crystal, and an high-Q external cavity laser diode was observed as 1.1 μW second harmonic ultraviolet-c power at 224.45 nm ultraviolet-c wavelength and 5.75 nm ultraviolet wavelength tunability. In addition, the improvement of increasing second harmonic power approximately 220 nm and the limitation of wavelength tuning of short wavelength are also theoretically discussed in this paper.

  6. Texture analysis applied to second harmonic generation image data for disease classification and development of a multi-view second harmonic generation imaging platform

    NASA Astrophysics Data System (ADS)

    Wen, Lianggong

    Many diseases, e.g. ovarian cancer, breast cancer and pulmonary fibrosis, are commonly associated with drastic alterations in surrounding connective tissue, and changes in the extracellular matrix (ECM) are associated with the vast majority of cellular processes in disease progression and carcinogenesis: cell differentiation, proliferation, biosynthetic ability, polarity, and motility. We use second harmonic generation (SHG) microscopy for imaging the ECM because it is a non-invasive, non-linear laser scanning technique with high sensitivity and specificity for visualizing fibrillar collagen. In this thesis, we are interested in developing imaging techniques to understand how the ECM, especially the collagen architecture, is remodeled in diseases. To quantitate remodeling, we implement a 3D texture analysis to delineate the collagen fibrillar morphology observed in SHG microscopy images of human normal and high grade malignant ovarian tissues. In the learning stage, a dictionary of "textons"---frequently occurring texture features that are identified by measuring the image response to a filter bank of various shapes, sizes, and orientations---is created. By calculating a representative model based on the texton distribution for each tissue type using a training set of respective mages, we then perform classification between normal and high grade malignant ovarian tissues classification based on the area under receiver operating characteristic curves (true positives versus false positives). The local analysis algorithm is a more general method to probe rapidly changing fibrillar morphologies than global analyses such as FFT. It is also more versatile than other texture approaches as the filter bank can be highly tailored to specific applications (e.g., different disease states) by creating customized libraries based on common image features. Further, we describe the development of a multi-view 3D SHG imaging platform. Unlike fluorescence microscopy, SHG excites

  7. Generation of cumulative second-harmonic ultrasonic guided waves with group velocity mismatching: Numerical analysis and experimental validation

    NASA Astrophysics Data System (ADS)

    Xiang, Yanxun; Zhu, Wujun; Deng, Mingxi; Xuan, Fu-Zhen; Liu, Chang-Jun

    2016-11-01

    The generation of second-harmonic Lamb waves in a homogeneous, isotropic, stress-free elastic plate is analytically and experimentally investigated. The numerical analyses show that whether the matching condition of the group velocity is satisfied or not, the integrated amplitude of a second-harmonic Lamb wave accumulates with the propagation distance when both the finite duration of the primary Lamb wave tone burst and the phase velocity matching are given. The theoretical analyses are validated by experimental measurements of an aluminium plate. Our conclusions are different from those of the previous works that reported that the group velocity matching is required for the generation of the cumulative second-harmonic Lamb waves with the finite duration of tone bursts.

  8. Interaction between O{sub 2} and ZnO films probed by time-dependent second-harmonic generation

    SciTech Connect

    Andersen, S. V.; Vandalon, V.; Bosch, R. H. E. C.; Loo, B. W. H. van de; Kessels, W. M. M.; Pedersen, K.

    2014-02-03

    The interaction between O{sub 2} and ZnO thin films prepared by atomic layer deposition has been investigated by time-dependent second-harmonic generation, by probing the electric field induced by adsorbed oxygen molecules on the surface. The second-harmonic generated signal decays upon laser exposure due to two-photon assisted desorption of O{sub 2}. Blocking and unblocking the laser beam for different time intervals reveals the adsorption rate of O{sub 2} onto ZnO. The results demonstrate that electric field induced second-harmonic generation provides a versatile non-contact probe of the adsorption kinetics of molecules on ZnO thin films.

  9. Second harmonic generation by relativistic self-focusing of q-Gaussian laser beam in preformed parabolic plasma channel

    SciTech Connect

    Singh, Arvinder E-mail: naveens222@rediffmail.com; Gupta, Naveen E-mail: naveens222@rediffmail.com

    2015-01-15

    This paper presents an investigation of relativistic self-focusing effect of a q-Gaussian laser beam on second harmonic generation in a preformed parabolic plasma channel. An expression has been derived for density perturbation associated with the plasma wave excited by the laser beam. This in turn acts as a source of second harmonic generation. The moment theory approach has been used to derive a differential equation that governs the evolution of spot size of the laser beam with the distance of propagation. The detailed effects of intensity distribution deviation from Gaussian distribution, intensity of laser beam, density, and depth of the channel have been studied on self-focusing as well as on second harmonic generation.

  10. Quasi-phase-matched second harmonic generation in silicon nitride ring resonators controlled by static electric field.

    PubMed

    de Oliveira, Rafael E P; de Matos, Christiano J S

    2013-12-30

    Actively-controlled second harmonic generation in a silicon nitride ring resonator is proposed and simulated. The ring was designed to resonate at both pump and second harmonic wavelengths and quasi-phase-matched frequency conversion is induced by a periodic static electric field generated by voltage applied to electrodes arranged along the ring. Nonlinear propagation simulations were undertaken and an efficiency of -21.67 dB was calculated for 60 mW of pump power at 1550 nm and for a 30V applied voltage, which compares favorably with demonstrated all-optical second harmonic generation in integrated microresonators. Transient effects were also evaluated. The proposed design can be exploited for the construction of electro-optical devices based on nonlinear effects in CMOS compatible circuits.

  11. Femtosecond nonlinear spectroscopy at surfaces: Second-harmonic probing of hole burning at the Si(111)7x7 surface and fourier-transform sum-frequency vibrational spectroscopy

    SciTech Connect

    McGuire, John Andrew

    2004-11-24

    The high temporal resolution and broad bandwidth of a femtosecond laser system are exploited in a pair of nonlinear optical studies of surfaces. The dephasing dynamics of resonances associated with the adatom dangling bonds of the Si(111)7 x 7 surface are explored by transient second-harmonic hole burning, a process that can be described as a fourth-order nonlinear optical process. Spectral holes produced by a 100 fs pump pulse at about 800 nm are probed by the second harmonic signal of a 100 fs pulse tunable around 800 nm. The measured spectral holes yield homogeneous dephasing times of a few tens of femtoseconds. Fits with a Lorentzian spectral hole centered at zero probe detuning show a linear dependence of the hole width on pump fluence, which suggests that charge carrier-carrier scattering dominates the dephasing dynamics at the measured excitation densities. Extrapolation of the deduced homogeneous dephasing times to zero excitation density yields an intrinsic dephasing time of {approx} 70 fs. The presence of a secondary spectral hole indicates that scattering of the surface electrons with surface optical phonons at 570 cm-1 occurs within the first 200 fs after excitation. The broad bandwidth of femtosecond IR pulses is used to perform IR-visible sum frequency vibrational spectroscopy. By implementing a Fourier-transform technique, we demonstrate the ability to obtain sub-laser-bandwidth spectral resolution. FT-SFG yields a greater signal when implemented with a stretched visible pulse than with a femtosecond visible pulse. However, when compared with multichannel spectroscopy using a femtosecond IR pulse but a narrowband visible pulse, Fourier-transform SFG is found to have an inferior signal-to-noise ratio. A mathematical analysis of the signal-to-noise ratio illustrates the constraints on the Fourier-transform approach.

  12. Combined optical second harmonic generation/quartz crystal microbalance study of underpotential deposition processes: copper electrodeposition on polycrystalline gold.

    PubMed

    Lakkaraju, S; Bennahmias, M J; Borges, G L; Gordon Ii, J G; Lazaga, M; Stone, B M; Ashley, K

    1990-11-20

    Optical second harmonic generation and quartz crystal microbalance techniques are used as in situ probes of copper underpotential deposition on polycrystalline gold surfaces in sulfuric acid electrolyte. The second harmonic signal from a polished bulk gold substrate is observed to decrease by >60% as a result of copper underpotential deposition on gold. Also, the mass of an underpotentially deposited copper adlayer is monitored in situ by an oscillating quartz crystal microbalance, yielding an estimated coverage of ~8.0 x 10(-10) mol cm(-2) and an electrosorption valency of 1.5 for a copper adlayer on the surface of vapor-deposited polycrystalline gold.

  13. Enhanced optical second harmonic generation in hybrid polymer nanoassemblies based on coupled surface plasmon resonance of a gold nanoparticle array

    NASA Astrophysics Data System (ADS)

    Ishifuji, Miki; Mitsuishi, Masaya; Miyashita, Tokuji

    2006-07-01

    Effective utilization of coupled surface plasmon resonance from gold nanoparticles was demonstrated experimentally for optoelectronic applications based on second-order nonlinear optics. Hybrid polymer nanoassemblies were constructed by manipulating gold nanoparticle arrays with nonlinear optical active polymer nanosheets to investigate the second harmonic generation. The gold nanoparticle arrays were assembled on heterodeposited polymer nanosheets. The second harmonic light intensity was enhanced by a factor of 8. The observed enhancement was attributed to coupling of surface plasmons between two adjacent gold nanoparticles, thereby enhancing the surface electromagnetic field around the nanoparticles at the fundamental light wavelength (1064nm).

  14. Depolarization of radiation from high-power neodymium lasers and second harmonic generation of partly depolarized radiation

    SciTech Connect

    Arifzhanov, S.B.; Gulamov, A.A.; Redkorechev, V.I.; Usmanov, T.

    1985-07-01

    A theoretical analysis is made of two mechanisms (linear and nonlinear) of depolarization of radiation emitted by high-power solid-state glass lasers: these mechanisms are anisotropy-induced in the active elements and a nonlinear rotation of the polarization ellipse. In the cases of linear and circular polarization of practical interest, a qualitative and numerical analysis is made of the influence of depolarization of the radiation on second harmonic generation by the second type of interaction in KDP crystals. It is shown that in a field of partly depolarized radiation the second harmonic generation efficiency is limited mainly by depolarization of the radiation.

  15. Polar Second-Harmonic Imaging to Resolve Pure and Mixed Crystal Phases along GaAs Nanowires.

    PubMed

    Timofeeva, Maria; Bouravleuv, Alexei; Cirlin, George; Shtrom, Igor; Soshnikov, Ilya; Reig Escalé, Marc; Sergeyev, Anton; Grange, Rachel

    2016-10-12

    In this work, we report an optical method for characterizing crystal phases along single-semiconductor III-V nanowires based on the measurement of polarization-dependent second-harmonic generation. This powerful imaging method is based on a per-pixel analysis of the second-harmonic-generated signal on the incoming excitation polarization. The dependence of the second-harmonic generation responses on the nonlinear second-order susceptibility tensor allows the distinguishing of areas of pure wurtzite, zinc blende, and mixed and rotational twins crystal structures in individual nanowires. With a far-field nonlinear optical microscope, we recorded the second-harmonic generation in GaAs nanowires and precisely determined their various crystal structures by analyzing the polar response for each pixel of the images. The predicted crystal phases in GaAs nanowire are confirmed with scanning transmission electron and high-resolution transmission electron measurements. The developed method of analyzing the nonlinear polar response of each pixel can be used for an investigation of nanowire crystal structure that is quick, sensitive to structural transitions, nondestructive, and on-the-spot. It can be applied for the crystal phase characterization of nanowires built into optoelectronic devices in which electron microscopy cannot be performed (for example, in lab-on-a-chip devices). Moreover, this method is not limited to GaAs nanowires but can be used for other nonlinear optical nanostructures.

  16. High energy cw-diode pumped Nd:YVO4 regenerative amplifier with efficient second harmonic generation.

    PubMed

    Lührmann, Markus; Theobald, Christian; Wallenstein, Richard; L'huillier, Johannes A

    2009-12-07

    We report on a 888 nm diode-pumped Nd:YVO4 regenerative amplifier with up to 33.7 W output power with a repetition-rate of 20 kHz and an adjustable pulse duration between 217 ps and 1 ns. This setup allowed for efficient second harmonic generation with an efficiency of up to 79%.

  17. Enhanced second-harmonic generation by means of high-power confinement in a photovoltaic soliton-induced waveguide.

    PubMed

    Lou, Cibo; Xu, Jingjun; Qiao, Haijun; Zhang, Xinzheng; Chen, Yunlin; Chen, Zhigang

    2004-05-01

    We present the first experimental demonstration of enhanced second-harmonic generation (SHG) by means of power confinement with a femtosecond laser in a photovoltaic soliton-induced waveguide. A dark spatial soliton created with a weak cw laser beam in a photovoltaic lithium niobate crystal induces an efficient waveguide for SHG, leading to a 60% enhancement of the conversion efficiency.

  18. The application of the symmetry properties of optical second harmonic generation to studies of interfaces and gases

    SciTech Connect

    Feller, M.B.

    1991-11-01

    Optical second harmonic generation has proven to be a powerful tool for studying interfaces. The symmetry properties of the process allow for surface sensitivity not available with other optical methods. In this thesis, we take advantage of these symmetry properties SHG to study a variety of interesting systems not previously studied with this technique. We show that optical second harmonic generation is an effective surface probe with a submonolayer sensitivity for media without inversion symmetry. We demonstrate the technique at a gallium arsenide surface, exploiting the different symmetry properties of the bulk and surface of the crystal to isolate the surface contribution. We also demonstrate that optical second harmonic generation can be used to determine the anisotropic orientational distribution of a surface monolayer of molecules. We apply the technique to study homogeneously aligned liquid crystal cells. To further explore the LC-polymer interface, we used SHG to study the surface memory effect. The surface memory effect is the rendering of an isotropic interface anisotropic by putting it in contact with an anisotropic bulk. Last, we describe some preliminary measurements of a time-resolved spectroscopic study of the phenomenon of second harmonic generation in a gas. The construction of a 500 microjoule pulsed, tunable laser source is described.

  19. Efficient second-harmonic imaging of collagen in histological slides using Bessel beam excitation

    NASA Astrophysics Data System (ADS)

    Vuillemin, Nelly; Mahou, Pierre; Débarre, Delphine; Gacoin, Thierry; Tharaux, Pierre-Louis; Schanne-Klein, Marie-Claire; Supatto, Willy; Beaurepaire, Emmanuel

    2016-07-01

    Second-harmonic generation (SHG) is the most specific label-free indicator of collagen accumulation in widespread pathologies such as fibrosis, and SHG-based measurements hold important potential for biomedical analyses. However, efficient collagen SHG scoring in histological slides is hampered by the limited depth-of-field of usual nonlinear microscopes relying on focused Gaussian beam excitation. In this work we analyze theoretically and experimentally the use of Bessel beam excitation to address this issue. Focused Bessel beams can provide an axially extended excitation volume for nonlinear microscopy while preserving lateral resolution. We show that shaping the focal volume has consequences on signal level and scattering directionality in the case of coherent signals (such as SHG) which significantly differ from the case of incoherent signals (two-photon excited fluorescence, 2PEF). We demonstrate extended-depth SHG-2PEF imaging of fibrotic mouse kidney histological slides. Finally, we show that Bessel beam excitation combined with spatial filtering of the harmonic light in wave vector space can be used to probe collagen accumulation more efficiently than the usual Gaussian excitation scheme. These results open the way to SHG-based histological diagnoses.

  20. Resonantly enhanced second-harmonic generation using III–V semiconductor all-dielectric metasurfaces

    SciTech Connect

    Liu, Sheng; Sinclair, Michael B.; Saravi, Sina; Keeler, Gordon A.; Yang, Yuanmu; Reno, John; Peake, Gregory M.; Setzpfandt, Frank; Staude, Isabelle; Pertsch, Thomas; Brener, Igal

    2016-08-08

    Nonlinear optical phenomena in nanostructured materials have been challenging our perceptions of nonlinear optical processes that have been explored since the invention of lasers. For example, the ability to control optical field confinement, enhancement, and scattering almost independently allows nonlinear frequency conversion efficiencies to be enhanced by many orders of magnitude compared to bulk materials. Also, the subwavelength length scale renders phase matching issues irrelevant. Compared with plasmonic nanostructures, dielectric resonator metamaterials show great promise for enhanced nonlinear optical processes due to their larger mode volumes. Here, we present, for the first time, resonantly enhanced second-harmonic generation (SHG) using gallium arsenide (GaAs) based dielectric metasurfaces. Using arrays of cylindrical resonators we observe SHG enhancement factors as large as 104 relative to unpatterned GaAs. At the magnetic dipole resonance, we measure an absolute nonlinear conversion efficiency of ~2 × 10–5 with ~3.4 GW/cm2 pump intensity. In conclusion, the polarization properties of the SHG reveal that both bulk and surface nonlinearities play important roles in the observed nonlinear process.

  1. Resonantly enhanced second-harmonic generation using III–V semiconductor all-dielectric metasurfaces

    DOE PAGES

    Liu, Sheng; Sinclair, Michael B.; Saravi, Sina; ...

    2016-08-08

    Nonlinear optical phenomena in nanostructured materials have been challenging our perceptions of nonlinear optical processes that have been explored since the invention of lasers. For example, the ability to control optical field confinement, enhancement, and scattering almost independently allows nonlinear frequency conversion efficiencies to be enhanced by many orders of magnitude compared to bulk materials. Also, the subwavelength length scale renders phase matching issues irrelevant. Compared with plasmonic nanostructures, dielectric resonator metamaterials show great promise for enhanced nonlinear optical processes due to their larger mode volumes. Here, we present, for the first time, resonantly enhanced second-harmonic generation (SHG) using galliummore » arsenide (GaAs) based dielectric metasurfaces. Using arrays of cylindrical resonators we observe SHG enhancement factors as large as 104 relative to unpatterned GaAs. At the magnetic dipole resonance, we measure an absolute nonlinear conversion efficiency of ~2 × 10–5 with ~3.4 GW/cm2 pump intensity. In conclusion, the polarization properties of the SHG reveal that both bulk and surface nonlinearities play important roles in the observed nonlinear process.« less

  2. Second-harmonic and two-photon imaging and polarimetry of articular cartilage

    NASA Astrophysics Data System (ADS)

    Mansfield, Jessica; Winlove, C. Peter; Moger, Julian; Knapp, Karen; Matcher, Steve

    2007-02-01

    Articular cartilage possesses an extensive extracellular matrix consisting of a highly organised network of collagen fibres embedded in a much finer mesh of proteoglycans and other glycoproteins. Many fundamental issues of cartilage biomechanics, its ageing and the development of osteoarthritis concern the detailed organisation of this matrix. Here we investigate the application of multi-photon microscopy to characterise the structure of the extracellular matrix. In reflection mode both second harmonic Generation (SHG) and two photon fluorescence (TPF) imaging modalities reveal differences in the pericellular and inter-territorial matrix in normal tissue and additional changes in degenerative lesions. The SHG signal from the surface zone is dependent on the direction of polarization of the laser excitation beam but the TPF signal is not. The former can be quantified to determine fibre orientation although the pattern is less well resolved than in tendon, reflecting the less regular orientation of the finer fibres. Nevertheless, previously unreported subtle variations in fibre orientation over the surface of the cartilage can be observed. In order to characterise variations with depth we carried out polarization sensitivity experiments at depths up to 180 microns into the tissue. At greater depths the polarization sensitivity is affected by the birefringence and dichroism of the overlying tissue and we have quantified these effects to allow correction of the data.

  3. Polarization second harmonic generation by image correlation spectroscopy on collagen type I hydrogels.

    PubMed

    Paesen, Rik; Sanen, Kathleen; Smisdom, Nick; Michiels, Luc; Ameloot, Marcel

    2014-05-01

    Successful engineering of biomimetic tissue relies on an accurate quantification of the mechanical properties of the selected scaffold. To improve this quantification, typical bulk rheological measurements are often complemented with microscopic techniques, including label-free second harmonic generation (SHG) imaging. Image correlation spectroscopy (ICS) has been applied to obtain quantitative information from SHG images of fibrous scaffolds. However, the typical polarization SHG (P-SHG) effect, which partly defines the shape of the autocorrelation function (ACF), has never been taken into account. Here we propose a new and flexible model to reliably apply ICS to P-SHG images of fibrous structures. By starting from a limited number of straightforward assumptions and by taking into account the P-SHG effect, we were able to cope with the typically observed ACF particularities. Using simulated datasets, the resulting model was thoroughly evaluated and compared with models previously described in the literature. We showed that our new model has no restrictions concerning the fibre length for the density retrieval. For certain length ranges, the model can additionally be used to obtain the average fibre length and the P-SHG related non-zero susceptibility tensor element ratios. From experimental data on collagen type I hydrogels, values of SHG tensor element ratios and fibre thickness were determined which match values reported in the literature, thereby underpinning the validity and applicability of our new model.

  4. Birefringence and second harmonic generation on tendon collagen following red linearly polarized laser irradiation.

    PubMed

    Silva, Daniela Fátima Teixeira; Gomes, Anderson Stevens Leonidas; de Campos Vidal, Benedicto; Ribeiro, Martha Simões

    2013-04-01

    Regarding the importance of type I collagen in understanding the mechanical properties of a range of tissues, there is still a gap in our knowledge of how proteins perform such work. There is consensus in literature that the mechanical characteristics of a tissue are primarily determined by the organization of its molecules. The purpose of this study was to characterize the organization of non-irradiated and irradiated type I collagen. Irradiation was performed with a linearly polarized HeNe laser (λ = 632.8 nm) and characterization was undertaken using polarized light microscopy to investigate the birefringence and second harmonic generation to analyze nonlinear susceptibility. Rats received laser irradiation (P = 6.0 mW, I = 21.2 mW/cm(2), E ≈ 0.3 J, ED = 1.0 J/cm(2)) on their healthy Achilles tendons, which after were extracted to prepare the specimens. Our results show that irradiated samples present higher birefringence and greater non-linear susceptibility than non-irradiated samples. Under studied conditions, we propose that a red laser with polarization direction aligned in parallel to the tendon long axis promotes further alignment on the ordered healthy collagen fibrils towards the electric field incident. Thus, prospects for biomedical applications for laser polarized radiation on type I collagen are encouraging since it supports greater tissue organization.

  5. Giant enhancement of second harmonic generation by engineering double plasmonic resonances at nanoscale.

    PubMed

    Ren, Ming-Liang; Liu, Si-Yun; Wang, Ben-Li; Chen, Bao-Qin; Li, Jiafang; Li, Zhi-Yuan

    2014-11-17

    We have investigated second harmonic generation (SHG) from Ag-coated LiNbO₃(LN) core-shell nanocuboids and found that giant SHG can occur via deliberately designed double plasmonic resonances. By controlling the aspect ratio, we can tune fundamental wave (FW) and SHG signal to match the longitudinal and transverse plasmonic modes simultaneously, and achieve giant enhancement of SHG by 3 × 10(5) in comparison to a bare LN nanocuboid and by about one order of magnitude to the case adopting only single plasmonic resonance. The underlying key physics is that the double-resonance nanoparticle enables greatly enhanced trapping and harvesting of incident FW energy, efficient internal transfer of optical energy from FW to the SHG signal, and much improved power to transport the SHG energy from the nanoparticle to the far-field region. The proposed double-resonance nanostructure can serve as an efficient subwavelength coherent light source through SHG and enable flexible engineering of light-matter interaction at nanoscale.

  6. Second-Harmonic Generation and Relaxation in Polyurea Thin Films Prepared by Vapor Deposition Polymerization

    NASA Astrophysics Data System (ADS)

    Hikita, Masayuki; Yamada, Sinichi; Mizutani, Teruyosi

    1993-06-01

    Aromatic polyurea thin (PU) films were fabricated by means of coevaporation of 4,4'-diphenylmethane diisocyanate (MDI) and either 4,4'-diamino diphenyl methane (DDM) or 4,4'-diamino diphenyl ether (DDE). For the two PU films, second-harmonic generation (SHG) caused by corona poling and the subsequent isothermal decay were investigated. The second-order nonlinear coefficient d33 was estimated to be 5.3 and 6.3 pm/V for PU(DDM) and PU(DDE), respectively, and proved to exhibit almost no decay with time up to 2000 h. It was also found that annealing prior to the poling process caused no additional increase of SHG. This result was interpreted in terms of increase in the packing density of molecules, leading to suppression of the molecular orientation. PU films containing excess residual isocyanate groups showed a large SHG decay to about 60% of the initial value within 10 min. It was concluded that the residual isocyanate groups in as-deposited PU films greatly affects the behavior of SHG relaxation.

  7. Experimental and modelling investigations into the laser ablation with picosecond pulses at second harmonics

    NASA Astrophysics Data System (ADS)

    Boerner, Paul; Zandonadi, Germana; Eberle, Gregory; Wegener, Konrad

    2015-03-01

    Ablation threshold experiments on various materials are carried out using a picosecond laser generating second harmonic radiation in air at atmospheric pressure. Various materials are investigated which vary according to their different electronic band gap structure and include: silicon, fine grain polycrystalline diamond, copper, steel and tungsten carbide. Through the use of scanning electron microscopy and 3D confocal microscopy, the crater depth and diameter are determined and a correlation is found. The ablation thresholds are given for the aforementioned materials and compared with recent literature results. Picosecond laser-material interactions are modelled using the two-temperature model, simulated and compared with experimental results for metallic materials. An extension of the two-temperature model to semiconducting and insulating materials is discussed. This alternative model uses multiple rate equations to describe the transient free electron density. Additionally, a set of coupled ordinary differential equations describes the processes of multiphoton excitation, inverse bremsstrahlung, and collisional excitation. The resulting electron density distribution can be used as an input for an electron density dependent twotemperature model. This multiple rate equation model is a generic and fast model, which provides important information like ablation threshold, ablation depth and optical properties.

  8. Second Harmonic Generation for time-resolved monitoring of membrane pore dynamics subserving electroporation of neurons

    PubMed Central

    Zalvidea, Dobryna; Claverol-Tinturé, Enric

    2011-01-01

    Electroporation of neurons, i.e. electric-field induced generation of membrane nanopores to facilitate internalization of molecules, is a classic technique used in basic neuroscience research and recently has been proposed as a promising therapeutic strategy in the area of neuro-oncology. To optimize electroporation parameters, optical techniques capable of delivering time and spatially-resolved information on electroporation pore formation at the nanometer scale would be advantageous. For this purpose we describe here a novel optical method based on second harmonic generation (SHG) microscopy. Due to the nonlinear and coherent nature of SHG, the 3D radiation lobes from stained neuronal membranes are sensitive to the spatial distribution of scatterers in the illuminated patch, and in particular to nanopore formation.We used phase-array analysis to computationally study the SHG signal as a function of nanopore size and nanopore population density and confirmed experimentally, in accordance with previous work, the dependence of nanopore properties on membrane location with respect to the electroporation electric field; higher nanopore densities, lasting < 5 milliseconds, are observed at membrane patches perpendicular to the field whereas lower density is observed at partly tangent locations. Differences between near-anode and near-cathode cell poles are also measured, showing higher pore densities at the anodic pole compared to cathodic pole. This technique is promising for the study of nanopore dynamics in neurons and for the optimization of novel electroporation-based therapeutic approaches. PMID:21339876

  9. Second harmonic generation microscopy differentiates collagen type I and type III in COPD

    NASA Astrophysics Data System (ADS)

    Suzuki, Masaru; Kayra, Damian; Elliott, W. Mark; Hogg, James C.; Abraham, Thomas

    2012-03-01

    The structural remodeling of extracellular matrix proteins in peripheral lung region is an important feature in chronic obstructive pulmonary disease (COPD). Multiphoton microscopy is capable of inducing specific second harmonic generation (SHG) signal from non-centrosymmetric structural proteins such as fibrillar collagens. In this study, SHG microscopy was used to examine structural remodeling of the fibrillar collagens in human lungs undergoing emphysematous destruction (n=2). The SHG signals originating from these diseased lung thin sections from base to apex (n=16) were captured simultaneously in both forward and backward directions. We found that the SHG images detected in the forward direction showed well-developed and well-structured thick collagen fibers while the SHG images detected in the backward direction showed striking different morphological features which included the diffused pattern of forward detected structures plus other forms of collagen structures. Comparison of these images with the wellestablished immunohistochemical staining indicated that the structures detected in the forward direction are primarily the thick collagen type I fibers and the structures identified in the backward direction are diffusive structures of forward detected collagen type I plus collagen type III. In conclusion, we here demonstrate the feasibility of SHG microscopy in differentiating fibrillar collagen subtypes and understanding their remodeling in diseased lung tissues.

  10. Second Harmonic Imaging improves Echocardiograph Quality on board the International Space Station

    NASA Technical Reports Server (NTRS)

    Garcia, Kathleen; Sargsyan, Ashot; Hamilton, Douglas; Martin, David; Ebert, Douglas; Melton, Shannon; Dulchavsky, Scott

    2008-01-01

    Ultrasound (US) capabilities have been part of the Human Research Facility (HRF) on board the International Space Station (ISS) since 2001. The US equipment on board the ISS includes a first-generation Tissue Harmonic Imaging (THI) option. Harmonic imaging (HI) is the second harmonic response of the tissue to the ultrasound beam and produces robust tissue detail and signal. Since this is a first-generation THI, there are inherent limitations in tissue penetration. As a breakthrough technology, HI extensively advanced the field of ultrasound. In cardiac applications, it drastically improves endocardial border detection and has become a common imaging modality. U.S. images were captured and stored as JPEG stills from the ISS video downlink. US images with and without harmonic imaging option were randomized and provided to volunteers without medical education or US skills for identification of endocardial border. The results were processed and analyzed using applicable statistical calculations. The measurements in US images using HI improved measurement consistency and reproducibility among observers when compared to fundamental imaging. HI has been embraced by the imaging community at large as it improves the quality and data validity of US studies, especially in difficult-to-image cases. Even with the limitations of the first generation THI, HI improved the quality and measurability of many of the downlinked images from the ISS and should be an option utilized with cardiac imaging on board the ISS in all future space missions.

  11. Quadrupole second harmonic generation and sum-frequency generation in ZnO quantum dots

    SciTech Connect

    Maikhuri, Deepti; Purohit, S. P. Mathur, K. C.

    2015-04-15

    The second harmonic generation (SHG) and the sum frequency generation (SFG) processes are investigated in the conduction band states of the singly charged ZnO quantum dot (QD) embedded in the HfO{sub 2}, and the AlN matrices. With two optical fields of frequency ω{sub p} and ω{sub q} incident on the dot, we study the variation with frequency of the second order nonlinear polarization resulting in SHG and SFG, through the electric dipole and the electric quadrupole interactions of the pump fields with the electron in the dot. We obtain enhanced value of the second order nonlinear susceptibility in the dot compared to the bulk. The effective mass approximation with the finite confining barrier is used for obtaining the energy and wavefunctions of the quantized confined states of the electron in the conduction band of the dot. Our results show that both the SHG and SFG processes depend on the dot size, the surrounding matrix and the polarization states of the pump beams.

  12. Second harmonic generation correlation spectroscopy for characterizing translationally diffusing protein nanocrystals.

    PubMed

    Dow, Ximeng Y; Dettmar, Christopher M; DeWalt, Emma L; Newman, Justin A; Dow, Alexander R; Roy-Chowdhury, Shatabdi; Coe, Jesse D; Kupitz, Christopher; Fromme, Petra; Simpson, Garth J

    2016-07-01

    Second harmonic generation correlation spectroscopy (SHG-CS) is demonstrated as a new approach to protein nanocrystal characterization. A novel line-scanning approach was performed to enable autocorrelation analysis without sample damage from the intense incident beam. An analytical model for autocorrelation was developed, which includes a correction for the optical scattering forces arising when focusing intense, infrared beams. SHG-CS was applied to the analysis of BaTiO3 nanoparticles ranging from 200 to ∼500 nm and of photosystem I nanocrystals. A size distribution was recovered for each sample and compared with the size histogram measured by scanning electron microscopy (SEM). Good agreement was observed between the two independent measurements. The intrinsic selectivity of the second-order nonlinear optical process provides SHG-CS with the ability to distinguish well ordered nanocrystals from conglomerates and amorphous aggregates. Combining the recovered distribution of particle diameters with the histogram of measured SHG intensities provides the inherent hyperpolarizability per unit volume of the SHG-active nanoparticles. Simulations suggest that the SHG activity per unit volume is likely to exhibit relatively low sensitivity to the subtle distortions within the lattice that contribute to resolution loss in X-ray diffraction, but high sensitivity to the presence of multi-domain crystals.

  13. In vivo wound healing diagnosis with second harmonic and fluorescence lifetime imaging

    NASA Astrophysics Data System (ADS)

    Deka, Gitanjal; Wu, Wei-Wen; Kao, Fu-Jen

    2013-06-01

    Skin wounds heal when a series of cell lineages are triggered, followed by collagen deposition, to reconstruct damaged tissues. This study evaluates the regeneration of collagen and change in cellular metabolic rate in vivo during wound healing in rats, with second harmonic generation (SHG) and fluorescence lifetime imaging microscopy respectively. The metabolic rate of cells is reflected through the lifetime of the autofluorescence from the co-enzyme protein, reduced nicotinamide adenine dinucleotide, due to its change in the relative concentration of bound and free forms. A higher than normal cellular metabolic rate is observed during the first week of healing, which decreases gradually after eight days of wound formation. SHG signal intensity change indicates the net degradation of collagen during the inflammatory phase, and net regeneration begins on day five. Eventually, the quantity of collagen increases gradually to form a scar tissue as the final product. Importantly, this work demonstrates the feasibility of an in vivo imaging approach for a normal wound on rat skin, which has the potential to supplement the noninvasive clinical diagnosis of wounds.

  14. Spatially resolved observation of the fundamental and second harmonic standing kink modes using SDO/AIA

    NASA Astrophysics Data System (ADS)

    Pascoe, D. J.; Goddard, C. R.; Nakariakov, V. M.

    2016-09-01

    Aims: We consider a coronal loop kink oscillation observed by the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO) which demonstrates two strong spectral components. The period of the lower frequency component being approximately twice that of the shorter frequency component suggests the presence of harmonics. Methods: We examine the presence of two longitudinal harmonics by investigating the spatial dependence of the loop oscillation. The time-dependent displacement of the loop is measured at 15 locations along the loop axis. For each position the displacement is fitted as the sum of two damped sinusoids, having periods P1 and P2, and a damping time τ. The shorter period component exhibits anti-phase oscillations in the loop legs. Results: We interpret the observation in terms of the first (global or fundamental) and second longitudinal harmonics of the standing kink mode. The strong excitation of the second harmonic appears connected to the preceding coronal mass ejection (CME) which displaced one of the loop legs. The oscillation parameters found are P1 = 5.00±0.62 min, P2 = 2.20±0.23 min, P1/ 2P2 = 1.15±0.22, and τ/P = 3.35 ± 1.45. A movie associated to Fig. 5 is available in electronic form at http://www.aanda.org

  15. Computational segmentation of collagen fibers from second-harmonic generation images of breast cancer.

    PubMed

    Bredfeldt, Jeremy S; Liu, Yuming; Pehlke, Carolyn A; Conklin, Matthew W; Szulczewski, Joseph M; Inman, David R; Keely, Patricia J; Nowak, Robert D; Mackie, Thomas R; Eliceiri, Kevin W

    2014-01-01

    Second-harmonic generation (SHG) imaging can help reveal interactions between collagen fibers and cancer cells. Quantitative analysis of SHG images of collagen fibers is challenged by the heterogeneity of collagen structures and low signal-to-noise ratio often found while imaging collagen in tissue. The role of collagen in breast cancer progression can be assessed post acquisition via enhanced computation. To facilitate this, we have implemented and evaluated four algorithms for extracting fiber information, such as number, length, and curvature, from a variety of SHG images of collagen in breast tissue. The image-processing algorithms included a Gaussian filter, SPIRAL-TV filter, Tubeness filter, and curvelet-denoising filter. Fibers are then extracted using an automated tracking algorithm called fiber extraction (FIRE). We evaluated the algorithm performance by comparing length, angle and position of the automatically extracted fibers with those of manually extracted fibers in twenty-five SHG images of breast cancer. We found that the curvelet-denoising filter followed by FIRE, a process we call CT-FIRE, outperforms the other algorithms under investigation. CT-FIRE was then successfully applied to track collagen fiber shape changes over time in an in vivo mouse model for breast cancer.

  16. Collagenous extracellular matrix of cartilage submitted to mechanical forces studied by second harmonic generation microscopy.

    PubMed

    Werkmeister, Elisabeth; de Isla, Natalia; Netter, Patrick; Stoltz, Jean-François; Dumas, Dominique

    2010-01-01

    Osteoarthritis is a degenerative pathology leading to degradation of the extracellular matrix (ECM). Similar effects can be visualized when applying mechanical or biochemical constraints on cartilaginous tissue. Here, we characterized modification of the ECM appearing under mechanical compression and/or biochemical action (hypoxia environment, nitric oxide and collagenase action). In recent decades, multiphoton microscopy has proved its interest for observing living, thick and opaque biological tissues. Thus, the main components of the cartilaginous ECM can be observed without fluorescent labeling. In particular, the collagen network emits strong second harmonic generation (SHG) signal which could be collected at half of the excitation wavelength. Combining autofluorescence and SHG signal detection enables to obtain complementary structural information. Here, we proved that multiphoton microscopy represents an appropriate tool for ex vitro cartilage imaging. First, we showed that SHG signal specifically comes from collagen (collagenase digestion). Further, we verified that the use of an appropriate band-pass filter enables to reject the autofluorescence from the ECM. Once this specificity was shown, we followed modification of the cartilage ECM submitted to mechanical or biochemical constraints (compression, enzymatic digestion). By performing textural analysis of SHG images (Haralick's method), we showed the restructuration of the collagen network according to constraints.

  17. Optical clearing for improved contrast in second harmonic generation imaging of skeletal muscle.

    PubMed

    Plotnikov, Sergey; Juneja, Vaibhav; Isaacson, Ariel B; Mohler, William A; Campagnola, Paul J

    2006-01-01

    Using second harmonic generation (SHG) imaging microscopy, we have examined the effect of optical clearing with glycerol to achieve greater penetration into specimens of skeletal muscle tissue. We find that treatment with 50% glycerol results in a 2.5-fold increase in achievable SHG imaging depth. Signal processing analyses using fast Fourier transform and continuous wavelet transforms show quantitatively that the periodicity of the sarcomere structure is unaltered by the clearing process and that image quality deep in the tissue is improved with clearing. Comparison of the SHG angular polarization dependence also shows no change in the supramolecular organization of acto-myosin complexes. By contrast, identical treatment of mouse tendon (collagen based) resulted in a strong decrease in SHG response. We suggest that the primary mechanism of optical clearing in muscle with glycerol treatment results from the reduction of cytoplasmic protein concentration and concomitant decrease in the secondary inner filter effect on the SHG signal. The lack of glycerol concentration dependence on the imaging depth indicates that refractive index matching plays only a minor role in the optical clearing of muscle. SHG and optical clearing may provide an ideal mechanism to study physiology in highly scattering skeletal or cardiac muscle tissue with significantly improved depth of penetration and achievable imaging depth.

  18. Towards protein-crystal centering using second-harmonic generation (SHG) microscopy

    PubMed Central

    Kissick, David J.; Dettmar, Christopher M.; Becker, Michael; Mulichak, Anne M.; Cherezov, Vadim; Ginell, Stephan L.; Battaile, Kevin P.; Keefe, Lisa J.; Fischetti, Robert F.; Simpson, Garth J.

    2013-01-01

    The potential of second-harmonic generation (SHG) microscopy for automated crystal centering to guide synchrotron X-­ray diffraction of protein crystals was explored. These studies included (i) comparison of microcrystal positions in cryoloops as determined by SHG imaging and by X-ray diffraction rastering and (ii) X-ray structure determinations of selected proteins to investigate the potential for laser-induced damage from SHG imaging. In studies using β2 adrenergic receptor membrane-protein crystals prepared in lipidic mesophase, the crystal locations identified by SHG images obtained in transmission mode were found to correlate well with the crystal locations identified by raster scanning using an X-­ray minibeam. SHG imaging was found to provide about 2 µm spatial resolution and shorter image-acquisition times. The general insensitivity of SHG images to optical scatter enabled the reliable identification of microcrystals within opaque cryocooled lipidic mesophases that were not identified by conventional bright-field imaging. The potential impact of extended exposure of protein crystals to five times a typical imaging dose from an ultrafast laser source was also assessed. Measurements of myoglobin and thaumatin crystals resulted in no statistically significant differences between structures obtained from diffraction data acquired from exposed and unexposed regions of single crystals. Practical constraints for integrating SHG imaging into an active beamline for routine automated crystal centering are discussed. PMID:23633594

  19. Analysis of second-harmonic-generation microscopy in a mouse model of ovarian carcinoma.

    PubMed

    Watson, Jennifer M; Rice, Photini F; Marion, Samuel L; Brewer, Molly A; Davis, John R; Rodriguez, Jeffrey J; Utzinger, Urs; Hoyer, Patricia B; Barton, Jennifer K

    2012-07-01

    Second-harmonic-generation (SHG) imaging of mouse ovaries ex vivo was used to detect collagen structure changes accompanying ovarian cancer development. Dosing with 4-vinylcyclohexene diepoxide and 7,12-dimethylbenz[a]anthracene resulted in histologically confirmed cases of normal, benign abnormality, dysplasia, and carcinoma. Parameters for each SHG image were calculated using the Fourier transform matrix and gray-level co-occurrence matrix (GLCM). Cancer versus normal and cancer versus all other diagnoses showed the greatest separation using the parameters derived from power in the highest-frequency region and GLCM energy. Mixed effects models showed that these parameters were significantly different between cancer and normal (P<0.008). Images were classified with a support vector machine, using 25% of the data for training and 75% for testing. Utilizing all images with signal greater than the noise level, cancer versus not-cancer specimens were classified with 81.2% sensitivity and 80.0% specificity, and cancer versus normal specimens were classified with 77.8% sensitivity and 79.3% specificity. Utilizing only images with greater than of 75% of the field of view containing signal improved sensitivity and specificity for cancer versus normal to 81.5% and 81.1%. These results suggest that using SHG to visualize collagen structure in ovaries could help with early cancer detection.

  20. Uranyl adsorption at the muscovite (mica)/water interface studied by second harmonic generation.

    PubMed

    Saslow Gomez, Sarah A; Jordan, David S; Troiano, Julianne M; Geiger, Franz M

    2012-10-16

    Uranyl adsorption at the muscovite (mica)/water interface was studied by second harmonic generation (SHG). Using the nonresonant χ(3) technique and the Gouy-Chapman model, the initial surface charge density of the mica surface was determined to be -0.022(1) C/m(2) at pH 6 and in the presence of dissolved carbonate. Under these same conditions, uranyl adsorption isotherms collected using nonresonant χ(3) experiments and resonantly enhanced SHG experiments that probe the ligand-to-metal charge transfer bands of the uranyl cation yielded a uranyl binding constant of 3(1) × 10(7) M(-1), corresponding to a Gibbs free energy of adsorption of -52.6(8) kJ/mol, and a maximum surface charge density at monolayer uranyl coverage of 0.028(3) C/m(2). These results suggest favorable adsorption of uranyl ions to the mica interface through strong ion-dipole or hydrogen interactions, with a 1:1 uranyl ion to surface site ratio that is indicative of monovalent cations ((UO(2))(3)(OH)(5)(+), (UO(2))(4)(OH)(7)(+), UO(2)OH(+), UO(2)Cl(+), UO(2)(CH(3)COO(-))(+)) binding at the interface, in addition to neutral uranyl species (UO(2)(OH)(2) and UO(2)CO(3)). This work provides benchmark measurements to be used in the improvement of contaminant transport modeling.

  1. The Interferometric Measurement of Phase Mismatch in Potential Second Harmonic Generators.

    NASA Astrophysics Data System (ADS)

    Sinofsky, Edward Lawrence

    This dissertation combines aspects of lasers, nonlinear optics and interferometry to measure the linear optical properties involved in phase matched second harmonic generation, (SHG). A new measuring technique has been developed to rapidly analyze the phase matching performance of potential SHGs. The data taken is in the form of interferograms produced by the self referencing nonlinear Fizeau interferometer (NLF), and correctly predicts when phase matched SHG will occur in the sample wedge. Data extracted from the interferograms produced by the NLF, allows us to predict both phase matching temperatures for noncritically phase matchable crystals and crystal orientation for angle tuned crystals. Phase matching measurements can be made for both Type I and Type II configurations. Phase mismatch measurements were made at the fundamental wavelength of 1.32 (mu)m, for: calcite, lithium niobate, and gadolinium molybdate (GMO). Similar measurements were made at 1.06 (mu)m. for calcite. Phase matched SHG was demonstrated in calcite, lithium niobate and KTP, while phase matching by temperature tuning is ruled out for GMO.

  2. 3D texture analysis for classification of second harmonic generation images of human ovarian cancer

    PubMed Central

    Wen, Bruce; Campbell, Kirby R.; Tilbury, Karissa; Nadiarnykh, Oleg; Brewer, Molly A.; Patankar, Manish; Singh, Vikas; Eliceiri, Kevin. W.; Campagnola, Paul J.

    2016-01-01

    Remodeling of the collagen architecture in the extracellular matrix (ECM) has been implicated in ovarian cancer. To quantify these alterations we implemented a form of 3D texture analysis to delineate the fibrillar morphology observed in 3D Second Harmonic Generation (SHG) microscopy image data of normal (1) and high risk (2) ovarian stroma, benign ovarian tumors (3), low grade (4) and high grade (5) serous tumors, and endometrioid tumors (6). We developed a tailored set of 3D filters which extract textural features in the 3D image sets to build (or learn) statistical models of each tissue class. By applying k-nearest neighbor classification using these learned models, we achieved 83–91% accuracies for the six classes. The 3D method outperformed the analogous 2D classification on the same tissues, where we suggest this is due the increased information content. This classification based on ECM structural changes will complement conventional classification based on genetic profiles and can serve as an additional biomarker. Moreover, the texture analysis algorithm is quite general, as it does not rely on single morphological metrics such as fiber alignment, length, and width but their combined convolution with a customizable basis set. PMID:27767180

  3. Analysis of second-harmonic-generation microscopy in a mouse model of ovarian carcinoma

    PubMed Central

    Watson, Jennifer M.; Rice, Photini F.; Marion, Samuel L.; Brewer, Molly A.; Davis, John R.; Rodriguez, Jeffrey J.; Utzinger, Urs; Hoyer, Patricia B.

    2012-01-01

    Abstract. Second-harmonic-generation (SHG) imaging of mouse ovaries ex vivo was used to detect collagen structure changes accompanying ovarian cancer development. Dosing with 4-vinylcyclohexene diepoxide and 7,12-dimethylbenz[a]anthracene resulted in histologically confirmed cases of normal, benign abnormality, dysplasia, and carcinoma. Parameters for each SHG image were calculated using the Fourier transform matrix and gray-level co-occurrence matrix (GLCM). Cancer versus normal and cancer versus all other diagnoses showed the greatest separation using the parameters derived from power in the highest-frequency region and GLCM energy. Mixed effects models showed that these parameters were significantly different between cancer and normal (P<0.008). Images were classified with a support vector machine, using 25% of the data for training and 75% for testing. Utilizing all images with signal greater than the noise level, cancer versus not-cancer specimens were classified with 81.2% sensitivity and 80.0% specificity, and cancer versus normal specimens were classified with 77.8% sensitivity and 79.3% specificity. Utilizing only images with greater than of 75% of the field of view containing signal improved sensitivity and specificity for cancer versus normal to 81.5% and 81.1%. These results suggest that using SHG to visualize collagen structure in ovaries could help with early cancer detection. PMID:22894485

  4. Resonantly Enhanced Second-Harmonic Generation Using III-V Semiconductor All-Dielectric Metasurfaces

    NASA Astrophysics Data System (ADS)

    Liu, Sheng; Sinclair, Michael B.; Saravi, Sina; Keeler, Gordon A.; Yang, Yuanmu; Reno, John; Peake, Gregory M.; Setzpfandt, Frank; Staude, Isabelle; Pertsch, Thomas; Brener, Igal

    2016-09-01

    Nonlinear optical phenomena in nanostructured materials have been challenging our perceptions of nonlinear optical processes that have been explored since the invention of lasers. For example, the ability to control optical field confinement, enhancement, and scattering almost independently, allows nonlinear frequency conversion efficiencies to be enhanced by many orders of magnitude compared to bulk materials. Also, the subwavelength length scale renders phase matching issues irrelevant. Compared with plasmonic nanostructures, dielectric resonator metamaterials show great promise for enhanced nonlinear optical processes due to their larger mode volumes. Here, we present, for the first time, resonantly enhanced second-harmonic generation (SHG) using Gallium Arsenide (GaAs) based dielectric metasurfaces. Using arrays of cylindrical resonators we observe SHG enhancement factors as large as 104 relative to unpatterned GaAs. At the magnetic dipole resonance we measure an absolute nonlinear conversion efficiency of ~2X10^(-5) with ~3.4 GW/cm2 pump intensity. The polarization properties of the SHG reveal that both bulk and surface nonlinearities play important roles in the observed nonlinear process.

  5. Resonantly Enhanced Second-Harmonic Generation Using III-V Semiconductor All-Dielectric Metasurfaces.

    PubMed

    Liu, Sheng; Sinclair, Michael B; Saravi, Sina; Keeler, Gordon A; Yang, Yuanmu; Reno, John; Peake, Gregory M; Setzpfandt, Frank; Staude, Isabelle; Pertsch, Thomas; Brener, Igal

    2016-09-14

    Nonlinear optical phenomena in nanostructured materials have been challenging our perceptions of nonlinear optical processes that have been explored since the invention of lasers. For example, the ability to control optical field confinement, enhancement, and scattering almost independently allows nonlinear frequency conversion efficiencies to be enhanced by many orders of magnitude compared to bulk materials. Also, the subwavelength length scale renders phase matching issues irrelevant. Compared with plasmonic nanostructures, dielectric resonator metamaterials show great promise for enhanced nonlinear optical processes due to their larger mode volumes. Here, we present, for the first time, resonantly enhanced second-harmonic generation (SHG) using gallium arsenide (GaAs) based dielectric metasurfaces. Using arrays of cylindrical resonators we observe SHG enhancement factors as large as 10(4) relative to unpatterned GaAs. At the magnetic dipole resonance, we measure an absolute nonlinear conversion efficiency of ∼2 × 10(-5) with ∼3.4 GW/cm(2) pump intensity. The polarization properties of the SHG reveal that both bulk and surface nonlinearities play important roles in the observed nonlinear process.

  6. Direct probing of contact electrification by using optical second harmonic generation technique

    NASA Astrophysics Data System (ADS)

    Chen, Xiangyu; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa; Wang, Zhong Lin

    2015-08-01

    Contact electrification between two different materials is one of the oldest fields of study in solid-state physics. Here, we introduced an innovative system based on optical electric-field-induced second harmonic generation (EFI-SHG) technique that can directly monitor the dynamic performance of the contact electrification on the surface of polyimide film. After the contact, the EFI-SHG system visualized briefly three relaxations of the tribo-induced charges on the surface of a polyimide film, a fast relaxation within 3 min followed by two much slower relaxations, which were possibly related to different charge diffusion routes. The contact electrification under several special experimental conditions (wind, water and steam) was studied to demonstrate the high flexibility and material selectivity of the EFI-SHG. The EFI-SHG studies confirmed the motion of the water can remove the surface charge, while the appearance and the evaporation of a thin water layer cannot enhance the charge diffusion. We anticipate that this experimental technique will find a variety of applications in the field of contact electrification and the development of the recently invented triboelectric nano generator.

  7. Infrared-based least-invasive third and second harmonic generation imaging of ocular tissues

    NASA Astrophysics Data System (ADS)

    Chen, Szu-Yu; Yu, Han-Chieh; Wang, I.-Jong; Sun, Chi-kuang

    2009-02-01

    Cornea functions as an outermost lens and plays an important role in vision. For cornea diagnosis and treatment, a microscopic imaging system with cellular resolution and high eye safety is strongly desired. Recently, the cell morphology of corneal epithelium and endothelium can be revealed by confocal or two-photon fluorescence microscopy, while the collagen fibers in the corneal stroma can be shown by second harmonic generation (SHG) microscopy. However, in most of the developed imaging tools, visible to near-infrared light sources were used. To increase the eye safety, a light source with longer wavelength would be needed. In this presentation, a study using an infrared laser based nonlinear microscopy to investigate the ocular tissues of a mouse eye will be demonstrated. Since most of autofluorescence was suppressed under infrared excitation, third harmonic generation (THG) microscopy was used to reveal the cellular morphology and ~700μm penetrability could be achieved. Combining SHG with THG, in an intact mouse eye, not only the cornea but also the upper half of the lens could be observed with cellular resolution. Our study indicated that infrared-based SHG and THG microscopy could provide a useful in vivo investigating tool for ophthalmology.

  8. Second harmonic generation imaging of corneal stroma after infection by Pseudomonas aeruginosa

    PubMed Central

    Robertson, Danielle M.; Rogers, Nathan A.; Petroll, W. Matthew; Zhu, Meifang

    2017-01-01

    Pseudomonas aeruginosa is a pathogenic gram-negative organism that has the ability to cause blinding corneal infections following trauma and during contact lens wear. In this study, we investigated the directional movement and orientation of an invasive corneal isolate of P. aeruginosa in the corneal stroma during infection of ex vivo and in vivo rabbit corneas using multiphoton fluorescence and second harmonic generation (SHG) imaging. Ex vivo, rabbit corneas were subject to three partial thickness wounds prior to inoculation. In vivo, New Zealand white rabbits were fit with P. aeruginosa laden contact lenses in the absence of a penetrating wound. At all time points tested, infiltration of the corneal stroma by P. aeruginosa revealed a high degree of alignment between the bacteria and collagen lamellae ex vivo (p < 0.001). In vivo, P. aeruginosa traveled throughout the stroma in discrete regions or bands. Within each region, the bacteria showed good alignment with collagen lamellae (P = 0.002). Interestingly, in both the in vitro and in vivo models, P. aeruginosa did not appear to cross the corneal limbus. Taken together, our findings suggest that P. aeruginosa exploits the precise spacing of collagen lamellae in the central cornea to facilitate spread throughout the stroma.

  9. Crystal growth and second harmonic generation efficiency of a chalcone derivative

    NASA Astrophysics Data System (ADS)

    Meenatchi, V.; Muthu, K.; Rajasekar, M.; Meenakshisundaram, SP.

    2013-06-01

    Single crystals of (2E,6E)-2-(4-fluorobenzylidine)-6-(4-methoxybenzylidine)cyclohexanone (FBMBC) have been grown by a slow evaporation solution growth technique from ethanol at room temperature. The single crystal X-ray diffraction study reveals that the FBMBC belongs to triclinic system and the cell parameters are a=9.790(6) Å, b=12.08(7) Å, c=14.09(9) Å and V=1577 Å3. The structure and the crystallinity of the material were further confirmed by powder X-ray diffraction analysis. The various functional groups present in the molecule are confirmed by Fourier transform infrared spectral analysis. The scanning electron microscopy study reveals the surface morphology of the as-grown crystal. Thermogravimetric/differential thermal analysis studies reveal the purity of the material and the crystals are transparent in the visible region having a low optical cut-off at ∼475 nm. The second harmonic generation efficiency of FBMBC is estimated by the Kurtz and Perry technique. Theoretical calculations were performed using the Hartree-Fock method with 6-31 G(d,p) as the basis set to derive the optimized geometry and the first-order molecular hyperpolarizability (β) values.

  10. Second harmonic generation imaging of skin wound healing and scarring in a rabbit ear model

    NASA Astrophysics Data System (ADS)

    Tang, Yiyan; Zhu, Xiaoqin; Xiong, Shuyuan; Chen, Jianxin

    2012-12-01

    Skin wound healing and scarring in rabbit ears was examined by second harmonic generation (SHG) microscopy. Rabbit ear wound model was created by punching from the ventral surface with removal of epidermis, dermis and perichondrium. The samples were collected weekly, and cut into 100 μm thickness sections for SHG imaging. SHG imaging system was operated at 810 nm, producing SHG signals at half the excitation wavelength 405 nm. A Plan-Neofluar objective (x40 and NA=0.75) was employed for focusing the excitation beam into tissue samples and was also used to collect the backscattered intrinsic SHG signals. Our results showed apparent difference in collagen content and microstructure at various wound healing and scarring time points. It suggested that SHG signals from collagen can serve as a good indicator for characterization of wound status. With the advancement on miniaturization, microscopy based on SHG will become a valuable tool for monitoring the wound healing and scarring in vivo, and help to guide the improvement of scar appearance with appropriate and subtle modulation during wound healing based on better understanding of scarring response mechanism.

  11. Quantitative evaluation of skeletal muscle defects in second harmonic generation images

    NASA Astrophysics Data System (ADS)

    Liu, Wenhua; Raben, Nina; Ralston, Evelyn

    2013-02-01

    Skeletal muscle pathologies cause irregularities in the normally periodic organization of the myofibrils. Objective grading of muscle morphology is necessary to assess muscle health, compare biopsies, and evaluate treatments and the evolution of disease. To facilitate such quantitation, we have developed a fast, sensitive, automatic imaging analysis software. It detects major and minor morphological changes by combining texture features and Fourier transform (FT) techniques. We apply this tool to second harmonic generation (SHG) images of muscle fibers which visualize the repeating myosin bands. Texture features are then calculated by using a Haralick gray-level cooccurrence matrix in MATLAB. Two scores are retrieved from the texture correlation plot by using FT and curve-fitting methods. The sensitivity of the technique was tested on SHG images of human adult and infant muscle biopsies and of mouse muscle samples. The scores are strongly correlated to muscle fiber condition. We named the software MARS (muscle assessment and rating scores). It is executed automatically and is highly sensitive even to subtle defects. We propose MARS as a powerful and unbiased tool to assess muscle health.

  12. Fully integrated reflection-mode photoacoustic, two-photon, and second harmonic generation microscopy in vivo

    PubMed Central

    Song, Wei; Xu, Qiang; Zhang, Yang; Zhan, Yang; Zheng, Wei; Song, Liang

    2016-01-01

    The ability to obtain comprehensive structural and functional information from intact biological tissue in vivo is highly desirable for many important biomedical applications, including cancer and brain studies. Here, we developed a fully integrated multimodal microscopy that can provide photoacoustic (optical absorption), two-photon (fluorescence), and second harmonic generation (SHG) information from tissue in vivo, with intrinsically co-registered images. Moreover, using a delicately designed optical-acoustic coupling configuration, a high-frequency miniature ultrasonic transducer was integrated into a water-immersion optical objective, thus allowing all three imaging modalities to provide a high lateral resolution of ~290 nm with reflection-mode imaging capability, which is essential for studying intricate anatomy, such as that of the brain. Taking advantage of the complementary and comprehensive contrasts of the system, we demonstrated high-resolution imaging of various tissues in living mice, including microvasculature (by photoacoustics), epidermis cells, cortical neurons (by two-photon fluorescence), and extracellular collagen fibers (by SHG). The intrinsic image co-registration of the three modalities conveniently provided improved visualization and understanding of the tissue microarchitecture. The reported results suggest that, by revealing complementary tissue microstructures in vivo, this multimodal microscopy can potentially facilitate a broad range of biomedical studies, such as imaging of the tumor microenvironment and neurovascular coupling. PMID:27576922

  13. Fully integrated reflection-mode photoacoustic, two-photon, and second harmonic generation microscopy in vivo

    NASA Astrophysics Data System (ADS)

    Song, Wei; Xu, Qiang; Zhang, Yang; Zhan, Yang; Zheng, Wei; Song, Liang

    2016-08-01

    The ability to obtain comprehensive structural and functional information from intact biological tissue in vivo is highly desirable for many important biomedical applications, including cancer and brain studies. Here, we developed a fully integrated multimodal microscopy that can provide photoacoustic (optical absorption), two-photon (fluorescence), and second harmonic generation (SHG) information from tissue in vivo, with intrinsically co-registered images. Moreover, using a delicately designed optical-acoustic coupling configuration, a high-frequency miniature ultrasonic transducer was integrated into a water-immersion optical objective, thus allowing all three imaging modalities to provide a high lateral resolution of ~290 nm with reflection-mode imaging capability, which is essential for studying intricate anatomy, such as that of the brain. Taking advantage of the complementary and comprehensive contrasts of the system, we demonstrated high-resolution imaging of various tissues in living mice, including microvasculature (by photoacoustics), epidermis cells, cortical neurons (by two-photon fluorescence), and extracellular collagen fibers (by SHG). The intrinsic image co-registration of the three modalities conveniently provided improved visualization and understanding of the tissue microarchitecture. The reported results suggest that, by revealing complementary tissue microstructures in vivo, this multimodal microscopy can potentially facilitate a broad range of biomedical studies, such as imaging of the tumor microenvironment and neurovascular coupling.

  14. Probing Interfacial Electronic States in CdSe Quantum Dots using Second Harmonic Generation Spectroscopy

    DOE PAGES

    Doughty, Benjamin L.; Ma, Yingzhong; Shaw, Robert W

    2015-01-07

    Understanding and rationally controlling the properties of nanomaterial surfaces is a rapidly expanding field of research due to the dramatic role they play on the optical and electronic properties vital to light harvesting, emitting and detection technologies. This information is essential to the continued development of synthetic approaches designed to tailor interfaces for optimal nanomaterial based device performance. In this work, closely spaced electronic excited states in model CdSe quantum dots (QDs) are resolved using second harmonic generation (SHG) spectroscopy, and the corresponding contributions from surface species to these states are assessed. Two distinct spectral features are observed in themore » SHG spectra, which are not readily identified in linear absorption and photoluminescence excitation spectra. These features include a weak band at 395 6 nm, which coincides with transitions to the 2S1/2 1Se state, and a much more pronounced band at 423 4 nm arising from electronic transitions to the 1P3/2 1Pe state. Chemical modification of the QD surfaces through oxidation resulted in disappearance of the SHG band corresponding to the 1P3/2 1Pe state, indicating prominent surface contributions. Signatures of deep trap states localized on the surfaces of the QDs are also observed. We further find that the SHG signal intensities depend strongly on the electronic states being probed and their relative surface contributions, thereby offering additional insight into the surface specificity of SHG signals from QDs.« less

  15. Second harmonic generation imaging as a potential tool for staging pregnancy and predicting preterm birth

    NASA Astrophysics Data System (ADS)

    Akins, Meredith L.; Luby-Phelps, Katherine; Mahendroo, Mala

    2010-03-01

    We use second harmonic generation (SHG) microscopy to assess changes in collagen structure of murine cervix during cervical remodeling of normal pregnancy and in a preterm birth model. Visual inspection of SHG images revealed substantial changes in collagen morphology throughout normal gestation. SHG images collected in both the forward and backward directions were analyzed quantitatively for changes in overall mean intensity, forward to backward intensity ratio, collagen fiber size, and porosity. Changes in mean SHG intensity and intensity ratio take place in early pregnancy, suggesting that submicroscopic changes in collagen fibril size and arrangement occur before macroscopic changes become evident. Fiber size progressively increased from early to late pregnancy, while pores between collagen fibers became larger and farther apart. Analysis of collagen features in premature cervical remodeling show that changes in collagen structure are dissimilar from normal remodeling. The ability to quantify multiple morphological features of collagen that characterize normal cervical remodeling and distinguish abnormal remodeling in preterm birth models supports future studies aimed at development of SHG endoscopic devices for clinical assessment of collagen changes during pregnancy in women and for predicting risk of preterm labor which occurs in 12.5% of all pregnancies.

  16. Observation of tendon repair in animal model using second-harmonic-generation microscopy

    NASA Astrophysics Data System (ADS)

    Hase, Eiji; Minamikawa, Takeo; Sato, Katsuya; Takahashi, Mitsuhiko; Yasui, Takashi

    2016-03-01

    Tendon rupture is a trauma difficult to recover the condition before injury. In previous researches, tensile test and staining method have been widely used to elucidate the mechanism of the repair process from the viewpoints of the mechanical property and the histological findings. However, since both methods are destructive and invasive, it is difficult to obtain both of them for the same sample. If both the mechanical property and the histological findings can be obtained from the same sample, one may obtain new findings regarding mechanisms of tendon repairing process. In this paper, we used second-harmonic-generation (SHG) microscopy, showing high selectivity and good image contrast to collagen molecules as well as high spatial resolution, optical three-dimensional sectioning, deep penetration, and without additional staining. Since SHG light intensity sensitively reflects the structural maturity of collagen molecule and its aggregates, it will be a good indicator for the repairing degree of the ruptured tendon. From comparison of SHG images between the 4-weeks-repaired tendon and the sound tendon in the animal model, we confirmed that SHG light intensity of the repaired tendon was significantly lower than that of the sound tendon, indicating that the collagen structure in the repaired tendon is still immature. Furthermore, we performed both SHG imaging and the tensile test for the same sample, and confirmed a correlation between them. This result shows a potential of SHG light for an indicator of the histological and mechanical recovery of the ruptured tendon.

  17. Second-harmonic generation and fluorescence lifetime imaging microscopy through a rodent mammary imaging window

    NASA Astrophysics Data System (ADS)

    Young, Pamela A.; Nazir, Muhammad; Szulczewski, Michael J.; Keely, Patricia J.; Eliceiri, Kevin W.

    2012-03-01

    Tumor-Associated Collagen Signatures (TACS) have been identified that manifest in specific ways during breast tumor progression and that correspond to patient outcome. There are also compelling metabolic changes associated with carcinoma invasion and progression. We have characterized the difference in the autofluorescent properties of metabolic co-factors, NADH and FAD, between normal and carcinoma breast cell lines. Also, we have shown in vitro that increased collagen density alters metabolic genes which are associated with glycolysis and leads to a more invasive phenotype. Establishing the relationship between collagen density, cellular metabolism, and metastasis in physiologically relevant cancer models is crucial for developing cancer therapies. To study cellular metabolism with respect to collagen density in vivo, we use multiphoton fluorescence excitation microscopy (MPM) in conjunction with a rodent mammary imaging window implanted in defined mouse cancer models. These models are ideal for the study of collagen changes in vivo, allowing determination of corresponding metabolic changes in breast cancer invasion and progression. To measure cellular metabolism, we collect fluorescence lifetime (FLIM) signatures of NADH and FAD, which are known to change based on the microenvironment of the cells. Additionally, MPM systems are capable of collecting second harmonic generation (SHG) signals which are a nonlinear optical property of collagen. Therefore, MPM, SHG, and FLIM are powerful tools with great potential for characterizing key features of breast carcinoma in vivo. Below we present the current efforts of our collaborative group to develop intravital approaches based on these imaging techniques to look at defined mouse mammary models.

  18. Second harmonic generation in a polar ferrimagnet GaFeO3

    NASA Astrophysics Data System (ADS)

    Igarashi, Jun-Ichi; Nagao, Tatsuya

    2010-07-01

    We have studied second harmonic generation (SHG) in a polar ferrimagnet GaFeO3 , employing a FeO6 cluster model in which the Fe atom is slightly shifted from the center of the octahedron. The electric-dipole transition could take place between the 3d states through the effective hybridization of the 4p states with the 3d states, due to the breaking of the space-inversion symmetry. In the third-order perturbation with Hint=-(1)/(c)jṡA , we calculate the probability per unit time, Iηaa , for the process that two photons are absorbed with polarization parallel to the a axis and one photon is emitted with polarization parallel to the η(=a,b,c) axis. The calculated SHG intensities consist of several peaks as a function of two-photon energy in agreement with the experiments. It is found that the corresponding amplitude Saaa at each Fe site changes its sign while Sbaa remains the same with the reversal of the direction of the local magnetic moment. This implies that Iaaa would disappear while Ibaa would survive in the paramagnetic phase in accordance with the experiment.

  19. Two-Photon and Second Harmonic Microscopy in Clinical and Translational Cancer Research

    PubMed Central

    PERRY, SETH W.; BURKE, RYAN M.; BROWN, EDWARD B.

    2012-01-01

    Application of two-photon microscopy (TPM) to translational and clinical cancer research has burgeoned over the last several years, as several avenues of pre-clinical research have come to fruition. In this review, we focus on two forms of TPM—two-photon excitation fluorescence microscopy, and second harmonic generation microscopy—as they have been used for investigating cancer pathology in ex vivo and in vivo human tissue. We begin with discussion of two-photon theory and instrumentation particularly as applicable to cancer research, followed by an overview of some of the relevant cancer research literature in areas that include two-photon imaging of human tissue biopsies, human skin in vivo, and the rapidly developing technology of two-photon microendoscopy. We believe these and other evolving two-photon methodologies will continue to help translate cancer research from the bench to the bedside, and ultimately bring minimally invasive methods for cancer diagnosis and treatment to therapeutic reality. PMID:22258888

  20. Structural and molecular conformation of myosin in intact muscle fibers by second harmonic generation

    NASA Astrophysics Data System (ADS)

    Nucciotti, V.; Stringari, C.; Sacconi, L.; Vanzi, F.; Linari, M.; Piazzesi, G.; Lombardi, V.; Pavone, F. S.

    2009-02-01

    Recently, the use of Second Harmonic Generation (SHG) for imaging biological samples has been explored with regard to intrinsic SHG in highly ordered biological samples. As shown by fractional extraction of proteins, myosin is the source of SHG signal in skeletal muscle. SHG is highly dependent on symmetries and provides selective information on the structural order and orientation of the emitting proteins and the dynamics of myosin molecules responsible for the mechano-chemical transduction during contraction. We characterise the polarization-dependence of SHG intensity in three different physiological states: resting, rigor and isometric tetanic contraction in a sarcomere length range between 2.0 μm and 4.0 μm. The orientation of motor domains of the myosin molecules is dependent on their physiological states and modulate the SHG signal. We can discriminate the orientation of the emitting dipoles in four different molecular conformations of myosin heads in intact fibers during isometric contraction, in resting and rigor. We estimate the contribution of the myosin motor domain to the total second order bulk susceptibility from its molecular structure and its functional conformation. We demonstrate that SHG is sensitive to the fraction of ordered myosin heads by disrupting the order of myosin heads in rigor with an ATP analog. We estimate the fraction of myosin motors generating the isometric force in the active muscle fiber from the dependence of the SHG modulation on the degree of overlap between actin and myosin filaments during an isometric contraction.

  1. Structural dynamics of the skeletal muscle fiber by second harmonic generation

    NASA Astrophysics Data System (ADS)

    Nucciotti, V.; Stringari, C.; Sacconi, L.; Vanzi, F.; Linari, M.; Piazzesi, G.; Lombardi, V.; Pavone, F. S.

    2008-02-01

    The high degree of structural order in skeletal muscle allows imaging of this tissue by Second Harmonic Generation (SHG). As previously found (Vanzi et al., J. Muscle Cell Res. Motil. 2006) by fractional extraction of proteins, myosin is the source of SHG signal. A full characterization of the polarization-dependence of the SHG signal can provide very selective information on the orientation of the emitting proteins and their dynamics during contraction. We developed a line scan polarization method, allowing measurements of a full polarization curve in intact muscle fibers from skeletal muscle of the frog to characterize the SHG polarization dependence on different physiological states (resting, rigor and isometric tetanic contraction). The polarization data have been interpreted by means of a model in terms of the average orientation of SHG emitters.The different physiological states are characterized by distinct patterns of SHG polarization. The variation of the orientation of emitting molecules in relation to the physiological state of the muscle demonstrates that one part of SHG signal arises from the globular head of the myosin molecule that cross-links actin and myosin filaments. The dependence of the SHG modulation on the degree of overlap between actin and myosin filaments during an isometric contraction, provides the constraints to estimate the fraction of myosin heads generating the isometric force in the active muscle fiber.

  2. Study of skeletal muscle cross-bridge population dynamics by second harmonic generation

    NASA Astrophysics Data System (ADS)

    Nucciotti, V.; Stringari, C.; Sacconi, L.; Vanzi, F.; Tesi, C.; Pirrodi, N.; Poggesi, C.; Castiglioni, C.; Milani, A.; Linari, M.; Piazzesi, G.; Lombardi, V.; Pavone, F. S.

    2007-02-01

    The high degree of structural order in skeletal muscle allows imaging of this tissue by Second Harmonic Generation (SHG). Biochemical and colocalization studies have gathered an increasing wealth of clues for the attribution of the molecular origin of the muscle SHG signal to the motor protein myosin. Thus, SHG represents a potentially very powerful tool in the investigation of structural dynamics occurring in muscle during active production of force and/or shortening. A full characterization of the polarization-dependence of the SHG signal represents a very selective information on the orientation of the emitting proteins and their dynamics during contraction, provided that different physiological states of muscle (relaxed, rigor and active) exhibit distinct patterns of SHG polarization dependence. Here polarization data are obtained from single frog muscle fibers at rest and during isometric contraction and interpreted, by means of a model, in terms of an average orientation of the SHG emitters which are structured with a cylindrical symmetry about the fiber axis. The setup is optimized for accurate polarization measurements with SHG, combined with a line scan imaging method allowing acquisition of SHG polarization curves in different physiological states. We demonstrate that muscle fiber displays a measurable variation of the orientation of SHG emitters with the transition from rest to isometric contraction.

  3. Functional imaging of skeletal muscle fiber in different physiological states by second harmonic generation

    NASA Astrophysics Data System (ADS)

    Nucciotti, V.; Stringari, C.; Sacconi, L.; Vanzi, F.; Tesi, C.; Piroddi, N.; Poggesi, C.; Castiglioni, C.; Milani, A.; Linari, M.; Piazzesi, G.; Lombardi, V.; Pavone, F. S.

    2007-07-01

    The intrinsically ordered arrays of proteins in skeletal muscle allows imaging of this tissue by Second Harmonic Generation (SHG). Biochemical and colocalization studies have gathered an increasing wealth of clues for the attribution of the molecular origin of the muscle SHG signal to the motor protein myosin. Thus, SHG represents a potentially very powerful tool in the investigation of structural dynamics occurring in muscle during active production of force. A full characterization of the polarization-dependence of the SHG signal represents a very selective information on the orientation of the emitting proteins and their dynamics during contraction, provided that different physiological states of muscle (relaxed, rigor and active) exhibit distinct patterns of SHG polarization dependence. Here polarization data are obtained from single frog muscle fibers at rest and during isometric contraction and interpreted, by means of a model, in terms of an average orientation of the SHG emitters which are structured with a cylindrical symmetry about the fiber axis. Optimizing the setup for accurate polarization measurements with SHG, we developed a line scan imaging method allowing measurement of SHG polarization curves in different physiological states. We demonstrate that muscle fiber displays a measurable variation of the orientation of SHG emitters with the transition from rest to isometric contraction.

  4. Second harmonic generation microscopy for quantitative analysis of collagen fibrillar structure

    PubMed Central

    Chen, Xiyi; Nadiarynkh, Oleg; Plotnikov, Sergey; Campagnola, Paul J

    2013-01-01

    Second-harmonic generation (SHG) microscopy has emerged as a powerful modality for imaging fibrillar collagen in a diverse range of tissues. Because of its underlying physical origin, it is highly sensitive to the collagen fibril/fiber structure, and, importantly, to changes that occur in diseases such as cancer, fibrosis and connective tissue disorders. We discuss how SHG can be used to obtain more structural information on the assembly of collagen in tissues than is possible by other microscopy techniques. We first provide an overview of the state of the art and the physical background of SHG microscopy, and then describe the optical modifications that need to be made to a laser-scanning microscope to enable the measurements. Crucial aspects for biomedical applications are the capabilities and limitations of the different experimental configurations. We estimate that the setup and calibration of the SHG instrument from its component parts will require 2–4 weeks, depending on the level of the user’s experience. PMID:22402635

  5. Electric-field-induced optical second-harmonic generation in doped graphene

    NASA Astrophysics Data System (ADS)

    Margulis, Vl. A.; Muryumin, E. E.; Gaiduk, E. A.

    2016-11-01

    A graphene layer interacting with an incident electromagnetic wave of frequency ω will produce dipole radiation at frequency 2 ω in the presence of an in-plane electric field breaking the spatial inversion symmetry of the graphene. Here, we develop a theory that describes such electric-field-induced second-harmonic generation (EFISHG) from doped graphene. We derive an analytic expression for the relevant third-order nonlinear optical (NLO) susceptibility χ (3)(- 2 ω ; ω , ω , 0) and numerically evaluate the absolute magnitude of the χ (3) for various values of the system's parameters. We find that the |χ (3) | spectrum is dominated by the resonant peak structure located at the incident photon energy ℏω equal to the Fermi energy EF of charge carriers in the doped graphene. We also show that the possibility to tune the doping level of graphene by an external gate voltage allows one to maximize the radiated EFISHG power at ℏω =EF , which may be of practical interest for the designs of the NLO devices based on employing a SHG-signal.

  6. Quantitative evaluation of skeletal muscle defects in second harmonic generation images

    PubMed Central

    Raben, Nina; Ralston, Evelyn

    2013-01-01

    Abstract. Skeletal muscle pathologies cause irregularities in the normally periodic organization of the myofibrils. Objective grading of muscle morphology is necessary to assess muscle health, compare biopsies, and evaluate treatments and the evolution of disease. To facilitate such quantitation, we have developed a fast, sensitive, automatic imaging analysis software. It detects major and minor morphological changes by combining texture features and Fourier transform (FT) techniques. We apply this tool to second harmonic generation (SHG) images of muscle fibers which visualize the repeating myosin bands. Texture features are then calculated by using a Haralick gray-level cooccurrence matrix in MATLAB. Two scores are retrieved from the texture correlation plot by using FT and curve-fitting methods. The sensitivity of the technique was tested on SHG images of human adult and infant muscle biopsies and of mouse muscle samples. The scores are strongly correlated to muscle fiber condition. We named the software MARS (muscle assessment and rating scores). It is executed automatically and is highly sensitive even to subtle defects. We propose MARS as a powerful and unbiased tool to assess muscle health. PMID:23377006

  7. Fully automated muscle quality assessment by Gabor filtering of second harmonic generation images.

    PubMed

    Paesen, Rik; Smolders, Sophie; Vega, José Manolo de Hoyos; Eijnde, Bert O; Hansen, Dominique; Ameloot, Marcel

    2016-02-01

    Although structural changes on the sarcomere level of skeletal muscle are known to occur due to various pathologies, rigorous studies of the reduced sarcomere quality remain scarce. This can possibly be explained by the lack of an objective tool for analyzing and comparing sarcomere images across biological conditions. Recent developments in second harmonic generation (SHG) microscopy and increasing insight into the interpretation of sarcomere SHG intensity profiles have made SHG microscopy a valuable tool to study microstructural properties of sarcomeres. Typically, sarcomere integrity is analyzed by fitting a set of manually selected, one-dimensional SHG intensity profiles with a supramolecular SHG model. To circumvent this tedious manual selection step, we developed a fully automated image analysis procedure to map the sarcomere disorder for the entire image at once. The algorithm relies on a single-frequency wavelet-based Gabor approach and includes a newly developed normalization procedure allowing for unambiguous data interpretation. The method was validated by showing the correlation between the sarcomere disorder, quantified by the M-band size obtained from manually selected profiles, and the normalized Gabor value ranging from 0 to 1 for decreasing disorder. Finally, to elucidate the applicability of our newly developed protocol, Gabor analysis was used to study the effect of experimental autoimmune encephalomyelitis on the sarcomere regularity. We believe that the technique developed in this work holds great promise for high-throughput, unbiased, and automated image analysis to study sarcomere integrity by SHG microscopy.

  8. Probing Interfacial Electronic States in CdSe Quantum Dots using Second Harmonic Generation Spectroscopy

    SciTech Connect

    Doughty, Benjamin L.; Ma, Yingzhong; Shaw, Robert W

    2015-01-07

    Understanding and rationally controlling the properties of nanomaterial surfaces is a rapidly expanding field of research due to the dramatic role they play on the optical and electronic properties vital to light harvesting, emitting and detection technologies. This information is essential to the continued development of synthetic approaches designed to tailor interfaces for optimal nanomaterial based device performance. In this work, closely spaced electronic excited states in model CdSe quantum dots (QDs) are resolved using second harmonic generation (SHG) spectroscopy, and the corresponding contributions from surface species to these states are assessed. Two distinct spectral features are observed in the SHG spectra, which are not readily identified in linear absorption and photoluminescence excitation spectra. These features include a weak band at 395 6 nm, which coincides with transitions to the 2S1/2 1Se state, and a much more pronounced band at 423 4 nm arising from electronic transitions to the 1P3/2 1Pe state. Chemical modification of the QD surfaces through oxidation resulted in disappearance of the SHG band corresponding to the 1P3/2 1Pe state, indicating prominent surface contributions. Signatures of deep trap states localized on the surfaces of the QDs are also observed. We further find that the SHG signal intensities depend strongly on the electronic states being probed and their relative surface contributions, thereby offering additional insight into the surface specificity of SHG signals from QDs.

  9. 3D texture analysis for classification of second harmonic generation images of human ovarian cancer

    NASA Astrophysics Data System (ADS)

    Wen, Bruce; Campbell, Kirby R.; Tilbury, Karissa; Nadiarnykh, Oleg; Brewer, Molly A.; Patankar, Manish; Singh, Vikas; Eliceiri, Kevin. W.; Campagnola, Paul J.

    2016-10-01

    Remodeling of the collagen architecture in the extracellular matrix (ECM) has been implicated in ovarian cancer. To quantify these alterations we implemented a form of 3D texture analysis to delineate the fibrillar morphology observed in 3D Second Harmonic Generation (SHG) microscopy image data of normal (1) and high risk (2) ovarian stroma, benign ovarian tumors (3), low grade (4) and high grade (5) serous tumors, and endometrioid tumors (6). We developed a tailored set of 3D filters which extract textural features in the 3D image sets to build (or learn) statistical models of each tissue class. By applying k-nearest neighbor classification using these learned models, we achieved 83–91% accuracies for the six classes. The 3D method outperformed the analogous 2D classification on the same tissues, where we suggest this is due the increased information content. This classification based on ECM structural changes will complement conventional classification based on genetic profiles and can serve as an additional biomarker. Moreover, the texture analysis algorithm is quite general, as it does not rely on single morphological metrics such as fiber alignment, length, and width but their combined convolution with a customizable basis set.

  10. In vivo multiphoton imaging of the cornea: polarization-resolved second harmonic generation from stromal collagen

    NASA Astrophysics Data System (ADS)

    Latour, G.; Gusachenko, I.; Kowalczuk, L.; Lamarre, I.; Schanne-Klein, M.-C.

    2012-03-01

    Multiphoton microscopy provides specific and contrasted images of unstained collagenous tissues such as tendons or corneas. Polarization-resolved second harmonic generation (SHG) measurements have been implemented in a laserscanning multiphoton microscope. Distortion of the polarimetric response due to birefringence and diattenuation during propagation of the laser excitation has been shown in rat-tail tendons. A model has been developed to account for these effects and correct polarization-resolved SHG images in thick tissues. This new modality is then used in unstained human corneas to access two quantitative parameters: the fibrils orientation within the collagen lamellae and the ratio of the main second-order nonlinear tensorial components. Orientation maps obtained from polarization resolution of the trans-detected SHG images are in good agreement with the striated features observed in the raw images. Most importantly, polarization analysis of the epi-detected SHG images also enables to map the fibrils orientation within the collagen lamellae while epi-detected SHG images of corneal stroma are spatially homogenous and do not enable direct visualization of the fibrils orientation. Depth profiles of the polarimetric SHG response are also measured and compared to models accounting for orientation changes of the collagen lamellae within the focal volume. Finally, in vivo polarization-resolved SHG is performed in rat corneas and structural organization of corneal stroma is determined using epi-detected signals.

  11. Pulsed second-harmonic generation in nonlinear, one-dimensional, periodic structures

    NASA Astrophysics Data System (ADS)

    Scalora, M.; Bloemer, M. J.; Manka, A. S.; Dowling, J. P.; Bowden, C. M.; Viswanathan, R.; Haus, J. W.

    1997-10-01

    We present a numerical study of second-harmonic (SH) generation in a one-dimensional, generic, photonic band-gap material that is doped with a nonlinear χ(2) medium. We show that a 20-period, 12-μm structure can generate short SH pulses (similar in duration to pump pulses) whose energy and power levels may be 2-3 orders of magnitude larger than the energy and power levels produced by an equivalent length of a phase-matched, bulk medium. This phenomenon comes about as a result of the combination of high electromagnetic mode density of states, low group velocity, and spatial phase locking of the fields near the photonic band edge. The structure is designed so that the pump pulse is tuned near the first-order photonic band edge, and the SH signal is generated near the band edge of the second-order gap. This maximizes the density of available field modes for both the pump and SH field. Our results show that the χ(2) response is effectively enhanced by several orders of magnitude. Therefore, mm- or cm-long, quasi-phase-matched devices could be replaced by these simple layered structures of only a few micrometers in length. This has important applications to high-energy lasers, Raman-type sources, and frequency up- and down-conversion schemes.

  12. Analysis of human knee osteoarthritic cartilage using polarization sensitive second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Kumar, Rajesh; Grønhaug, Kirsten M.; Romijn, Elisabeth I.; Drogset, Jon O.; Lilledahl, Magnus B.

    2014-05-01

    Osteoarthritis is one of the most prevalent joint diseases in the world. Although the cause of osteoarthritis is not exactly clear, the disease results in a degradation of the quality of the articular cartilage including collagen and other extracellular matrix components. We have investigated alterations in the structure of collagen fibers in the cartilage tissue of the human knee using mulitphoton microscopy. Due to inherent high nonlinear susceptibility, ordered collagen fibers present in the cartilage tissue matrix produces strong second harmonic generation (SHG) signals. Significant morphological differences are found in different Osteoarthritic grades of cartilage by SHG microscopy. Based on the polarization analysis of the SHG signal, we find that a few locations of hyaline cartilage (mainly type II collagen) is being replaced by fibrocartilage (mainly type I cartilage), in agreement with earlier literature. To locate the different types and quantify the alteration in the structure of collagen fiber, we employ polarization-SHG microscopic analysis, also referred to as _-tensor imaging. The image analysis of p-SHG image obtained by excitation polarization measurements would represent different tissue constituents with different numerical values at pixel level resolution.

  13. Quantification of collagen distributions in rat hyaline and fibro cartilages based on second harmonic generation imaging

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaoqin; Liao, Chenxi; Wang, Zhenyu; Zhuo, Shuangmu; Liu, Wenge; Chen, Jianxin

    2016-10-01

    Hyaline cartilage is a semitransparent tissue composed of proteoglycan and thicker type II collagen fibers, while fibro cartilage large bundles of type I collagen besides other territorial matrix and chondrocytes. It is reported that the meniscus (fibro cartilage) has a greater capacity to regenerate and close a wound compared to articular cartilage (hyaline cartilage). And fibro cartilage often replaces the type II collagen-rich hyaline following trauma, leading to scar tissue that is composed of rigid type I collagen. The visualization and quantification of the collagen fibrillar meshwork is important for understanding the role of fibril reorganization during the healing process and how different types of cartilage contribute to wound closure. In this study, second harmonic generation (SHG) microscope was applied to image the articular and meniscus cartilage, and textural analysis were developed to quantify the collagen distribution. High-resolution images were achieved based on the SHG signal from collagen within fresh specimens, and detailed observations of tissue morphology and microstructural distribution were obtained without shrinkage or distortion. Textural analysis of SHG images was performed to confirm that collagen in fibrocartilage showed significantly coarser compared to collagen in hyaline cartilage (p < 0.01). Our results show that each type of cartilage has different structural features, which may significantly contribute to pathology when damaged. Our findings demonstrate that SHG microscopy holds potential as a clinically relevant diagnostic tool for imaging degenerative tissues or assessing wound repair following cartilage injury.

  14. The Impact of Collagen Fibril Polarity on Second Harmonic Generation Microscopy

    PubMed Central

    Couture, Charles-André; Bancelin, Stéphane; Van der Kolk, Jarno; Popov, Konstantin; Rivard, Maxime; Légaré, Katherine; Martel, Gabrielle; Richard, Hélène; Brown, Cameron; Laverty, Sheila; Ramunno, Lora; Légaré, François

    2015-01-01

    In this work, we report the implementation of interferometric second harmonic generation (SHG) microscopy with femtosecond pulses. As a proof of concept, we imaged the phase distribution of SHG signal from the complex collagen architecture of juvenile equine growth cartilage. The results are analyzed in respect to numerical simulations to extract the relative orientation of collagen fibrils within the tissue. Our results reveal large domains of constant phase together with regions of quasi-random phase, which are correlated to respectively high- and low-intensity regions in the standard SHG images. A comparison with polarization-resolved SHG highlights the crucial role of relative fibril polarity in determining the SHG signal intensity. Indeed, it appears that even a well-organized noncentrosymmetric structure emits low SHG signal intensity if it has no predominant local polarity. This work illustrates how the complex architecture of noncentrosymmetric scatterers at the nanoscale governs the coherent building of SHG signal within the focal volume and is a key advance toward a complete understanding of the structural origin of SHG signals from tissues. PMID:26682809

  15. Monitoring the Photocleaving Dynamics of Colloidal MicroRNA-Functionalized Gold Nanoparticles Using Second Harmonic Generation.

    PubMed

    Kumal, Raju R; Landry, Corey R; Abu-Laban, Mohammad; Hayes, Daniel J; Haber, Louis H

    2015-09-15

    Photoactivated drug delivery systems using gold nanoparticles provide the promise of spatiotemporal control of delivery that is crucial for applications ranging from regenerative medicine to cancer therapy. In this study, we use second harmonic generation (SHG) spectroscopy to monitor the light-activated controlled release of oligonucleotides from the surface of colloidal gold nanoparticles. MicroRNA is functionalized to spherical gold nanoparticles using a nitrobenzyl linker that undergoes photocleaving upon ultraviolet irradiation. The SHG signal generated from the colloidal nanoparticle sample is shown to be a sensitive probe for monitoring the photocleaving dynamics in real time. The photocleaving irradiation wavelength is scanned to show maximum efficiency on resonance at 365 nm, and the kinetics are investigated at varying irradiation powers to demonstrate that the nitrobenzyl photocleaving is a one-photon process. Additional characterization methods including electrophoretic mobility measurements, extinction spectroscopy, and fluorimetry are used to verify the SHG results, leading to a better understanding of the photocleaving dynamics for this model oligonucleotide therapeutic delivery system.

  16. Automated biphasic morphological assessment of hepatitis B-related liver fibrosis using second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Wang, Tong-Hong; Chen, Tse-Ching; Teng, Xiao; Liang, Kung-Hao; Yeh, Chau-Ting

    2015-08-01

    Liver fibrosis assessment by biopsy and conventional staining scores is based on histopathological criteria. Variations in sample preparation and the use of semi-quantitative histopathological methods commonly result in discrepancies between medical centers. Thus, minor changes in liver fibrosis might be overlooked in multi-center clinical trials, leading to statistically non-significant data. Here, we developed a computer-assisted, fully automated, staining-free method for hepatitis B-related liver fibrosis assessment. In total, 175 liver biopsies were divided into training (n = 105) and verification (n = 70) cohorts. Collagen was observed using second harmonic generation (SHG) microscopy without prior staining, and hepatocyte morphology was recorded using two-photon excitation fluorescence (TPEF) microscopy. The training cohort was utilized to establish a quantification algorithm. Eleven of 19 computer-recognizable SHG/TPEF microscopic morphological features were significantly correlated with the ISHAK fibrosis stages (P < 0.001). A biphasic scoring method was applied, combining support vector machine and multivariate generalized linear models to assess the early and late stages of fibrosis, respectively, based on these parameters. The verification cohort was used to verify the scoring method, and the area under the receiver operating characteristic curve was >0.82 for liver cirrhosis detection. Since no subjective gradings are needed, interobserver discrepancies could be avoided using this fully automated method.

  17. Enforcing symmetries in boundary element formulation of plasmonic and second-harmonic scattering problems.

    PubMed

    Mäkitalo, Jouni; Suuriniemi, Saku; Kauranen, Martti

    2014-12-01

    The study of metal nanoparticles and metamaterials has increased the demand for accurate and efficient numerical methods for solving electromagnetic scattering problems. The boundary element method, and especially its Poggio-Miller-Chang-Harrington-Wu-Tsai (PMCHWT) formulation, has received growing interest lately due to its accuracy and stability at plasmon resonance conditions. Consequently, this formulation has been used to model second-harmonic generation (SHG) in plasmonic nanoparticles, which is an area of increasing importance. Many nanostructures exhibit geometrical symmetries, whose identification is often crucial for the qualitative understanding of SHG. In this work, we present the theory and details to take advantage of these symmetries in the PMCHWT formulation. We show that, importantly, the symmetry of the medium can be exploited even though the excitation source does not exhibit a well-defined symmetry. We estimate the obtainable computational benefits and apply the method to the study of the linear and second-order nonlinear properties of multiply split gold ring resonators.

  18. Direct probing of contact electrification by using optical second harmonic generation technique

    PubMed Central

    Chen, Xiangyu; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa; Wang, Zhong Lin

    2015-01-01

    Contact electrification between two different materials is one of the oldest fields of study in solid-state physics. Here, we introduced an innovative system based on optical electric-field-induced second harmonic generation (EFI-SHG) technique that can directly monitor the dynamic performance of the contact electrification on the surface of polyimide film. After the contact, the EFI-SHG system visualized briefly three relaxations of the tribo-induced charges on the surface of a polyimide film, a fast relaxation within 3 min followed by two much slower relaxations, which were possibly related to different charge diffusion routes. The contact electrification under several special experimental conditions (wind, water and steam) was studied to demonstrate the high flexibility and material selectivity of the EFI-SHG. The EFI-SHG studies confirmed the motion of the water can remove the surface charge, while the appearance and the evaporation of a thin water layer cannot enhance the charge diffusion. We anticipate that this experimental technique will find a variety of applications in the field of contact electrification and the development of the recently invented triboelectric nano generator. PMID:26272162

  19. Nonlinear optical response of the collagen triple helix and second harmonic microscopy of collagen liquid crystals

    NASA Astrophysics Data System (ADS)

    Deniset-Besseau, A.; De Sa Peixoto, P.; Duboisset, J.; Loison, C.; Hache, F.; Benichou, E.; Brevet, P.-F.; Mosser, G.; Schanne-Klein, M.-C.

    2010-02-01

    Collagen is characterized by triple helical domains and plays a central role in the formation of fibrillar and microfibrillar networks, basement membranes, as well as other structures of the connective tissue. Remarkably, fibrillar collagen exhibits efficient Second Harmonic Generation (SHG) and SHG microscopy proved to be a sensitive tool to score fibrotic pathologies. However, the nonlinear optical response of fibrillar collagen is not fully characterized yet and quantitative data are required to further process SHG images. We therefore performed Hyper-Rayleigh Scattering (HRS) experiments and measured a second order hyperpolarisability of 1.25 10-27 esu for rat-tail type I collagen. This value is surprisingly large considering that collagen presents no strong harmonophore in its amino-acid sequence. In order to get insight into the physical origin of this nonlinear process, we performed HRS measurements after denaturation of the collagen triple helix and for a collagen-like short model peptide [(Pro-Pro-Gly)10]3. It showed that the collagen large nonlinear response originates in the tight alignment of a large number of weakly efficient harmonophores, presumably the peptide bonds, resulting in a coherent amplification of the nonlinear signal along the triple helix. To illustrate this mechanism, we successfully recorded SHG images in collagen liquid solutions by achieving liquid crystalline ordering of the collagen triple helices.

  20. Protein Conformational Changes Are Detected and Resolved Site Specifically by Second-Harmonic Generation.

    PubMed

    Moree, Ben; Connell, Katelyn; Mortensen, Richard B; Liu, C Tony; Benkovic, Stephen J; Salafsky, Joshua

    2015-08-18

    We present here a straightforward, broadly applicable technique for real-time detection and measurement of protein conformational changes in solution. This method is based on tethering proteins labeled with a second-harmonic generation (SHG) active dye to supported lipid bilayers. We demonstrate our method by measuring the conformational changes that occur upon ligand binding with three well-characterized proteins labeled at lysine residues: calmodulin (CaM), maltose-binding protein (MBP), and dihydrofolate reductase (DHFR). We also create a single-site cysteine mutant of DHFR engineered within the Met20 catalytic loop region and study the protein's structural motion at this site. Using published x-ray crystal structures, we show that the changes in the SHG signals upon ligand binding are the result of structural motions that occur at the labeled sites between the apo and ligand-bound forms of the proteins, which are easily distinguished from each other. In addition, we demonstrate that different magnitudes of the SHG signal changes are due to different and specific ligand-induced conformational changes. Taken together, these data illustrate the potential of the SHG approach for detecting and measuring protein conformational changes for a wide range of biological applications.

  1. Phase and Texture Characterizations of Scar Collagen Second-Harmonic Generation Images Varied with Scar Duration.

    PubMed

    Chen, Guannan; Liu, Yao; Zhu, Xiaoqin; Huang, Zufang; Cai, Jianyong; Chen, Rong; Xiong, Shuyuan; Zeng, Haishan

    2015-08-01

    This work developed a phase congruency algorithm combined with texture analysis to quantitatively characterize collagen morphology in second-harmonic generation (SHG) images from human scars. The extracted phase and texture parameters of the SHG images quantified collagen directionality, homogeneity, and coarseness in scars and varied with scar duration. Phase parameters showed an increasing tendency of the mean of phase congruency with scar duration, indicating that collagen fibers are better oriented over time. Texture parameters calculated from local difference local binary pattern (LD-LBP) and Haar wavelet transform, demonstrated that the LD-LBP variance decreased and the energy of all subimages increased with scar duration. It implied that collagen has a more regular pattern and becomes coarser with scar duration. In addition, the random forest regression was used to predict scar duration, demonstrating reliable performance of the extracted phase and texture parameters in characterizing collagen morphology in scar SHG images. Results indicate that the extracted parameters using the proposed method can be used as quantitative indicators to monitor scar progression with time and can help understand the mechanism of scar progression.

  2. Tumor tissue characterization using polarization-sensitive second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Tokarz, Danielle; Cisek, Richard; Golaraei, Ahmad; Krouglov, Serguei; Navab, Roya; Niu, Carolyn; Sakashita, Shingo; Yasufuku, Kazuhiro; Tsao, Ming-Sound; Asa, Sylvia L.; Barzda, Virginijus; Wilson, Brian C.

    2015-06-01

    Changes in the ultrastructure of collagen in various tumor and non-tumor human tissues including lung, pancreas and thyroid were investigated ex vivo by a polarization-sensitive second harmonic generation (SHG) microscopy technique referred to as polarization-in, polarization-out (PIPO) SHG. This involves measuring the orientation of the linear polarization of outgoing SHG as a function of the linear polarization orientation of incident laser radiation. From the PIPO SHG data, the second-order nonlinear optical susceptibility tensor component ratio, χ(2) ZZZ'/χ(2) ZXX', for each pixel of the SHG image was obtained and presented as color-coded maps. Further, the orientation of collagen fibers in the tissue was deduced. Since the χ(2) ZZZ'/χ(2) ZXX' values represent the organization of collagen in the tissue, theses maps revealed areas of altered collagen structure (not simply concentration) within tissue sections. Statistically-significant differences in χ(2) ZZZ'/χ(2) ZXX' were found between tumor and non-tumor tissues, which varied from organ to organ. Hence, PIPO SHG microscopy could potentially be used to aid pathologists in diagnosing cancer. Additionally, PIPO SHG microscopy could aid in characterizing the structure of collagen in other collagen-related biological processes such as wound repair.

  3. Field enhancement at silicon surfaces by gold ellipsoids probed by optical second-harmonic generation spectroscopy

    NASA Astrophysics Data System (ADS)

    Ulriksen, Hans Ulrik; Pedersen, Kjeld

    2016-12-01

    Optical second-harmonic generation (SHG) spectroscopy has been used to determine the field enhancements from Au nanoparticles on a silicon substrate. Au particles with diameters from 30 to 250 nm have been deposited on a Si substrate passivated by a 1 nm thick surface oxide. The linear optical spectra are dominated by a horizontal plasmon resonance near 1.0 eV, and the experimental spectra are modelled by the island film model in order to extract the linear properties of the metal particles. SHG spectroscopy from this system shows resonances from the metal particles and from the silicon/oxide substrate. By following the evolution of these Si resonances with the size of the Au particles, the field enhancement in the Si surface has been modelled. The effect of the Au particles on SHG at the Si E1 resonance is a combination of charge transfer through the thin oxide that changes the space charge region and an enhancement of the optical field in a thin surface layer of the Si substrate.

  4. Second-Harmonic Generation scanning microscopy of strain fields around Through-Silicon-Vias

    NASA Astrophysics Data System (ADS)

    Cho, Yujin; Shafiei, Farbod; Mendoza, Bernardo; Jiang, Tengfei; Ho, Paul; Downer, Michael

    Through-Silicon-Vias (TSVs) improve electrical performance of integrated circuits and reduce power consumption by interconnecting vertically stacked silicon layers. Cu has been commonly used for TSVs because of its good electrical and mechanical properties. However, mismatch in thermal expansion coefficient of Si and Cu induces strain fields on the surfaces, which can degrade the performance of nearby devices and crack the surfaces. In this work, using non-invasive Second Harmonic Generation (SHG) microscopy, we successfully characterized inhomogeneous distribution of the thermally induced strain fields. High strain gradients strengthen SHG intensity, since it breaks centrosymmetry in Si. In p-polarized incoming beam and s-polarized SHG configuration, we were able to see the strain effect directly, while in p-in/ p-out polarization, strain-induced SHG was coupled with background SHG from Si. We will present SHG micrographs compared with Raman measurement and the theory of strain-induced SHG, as well as wavelength and power dependence of SHG

  5. Multiple-wavelength second-harmonic generations in a two-dimensional periodically poled lithium niobate

    NASA Astrophysics Data System (ADS)

    Ni, Peigen; Ma, Boqin; Feng, Shuai; Cheng, Bingying; Zhang, Daozhong

    2004-03-01

    A two-dimensional nonlinear photonic crystal of lithium niobate with rectangular lattice was fabricated. In this crystal, the quasiphase-matching conditions can be satisfied in different directions for different wavelengths. As a tunable optical parametric oscillator pumped by an yttritium-aluminum-garnet laser with about 4 ns pulse duration was used, we obtained the second-harmonic output at 676 nm (red) and 571 nm (yellow) by the first-order quasiphase-matching, and at 532 nm (green) and 460 nm (blue) by the second-order quasiphase-matching, respectively. The conversion efficiency of fundamental wavelength 1352 and 1142 nm was 33% and 48.2% when the average input power was 1.47 and 2.8 mW, respectively. Our results imply that by using only one frequency conversion element, coherent beams with various colors may be attained. The application of such a two-dimensional nonlinear photonic crystal in the field of color display is expected.

  6. Sum frequency and second harmonic generation from the surface of a liquid microjet

    SciTech Connect

    Smolentsev, Nikolay; Chen, Yixing; Roke, Sylvie; Jena, Kailash C.; Brown, Matthew A.

    2014-11-14

    The use of a liquid microjet as a possible source of interest for Second Harmonic Generation (SHG) and Sum Frequency Generation (SFG) spectroscopy is examined. We measured non-resonant SHG scattering patterns from the air/water interface of a microjet of pure water and observe a strong enhancement of the SHG signal for certain scattering angles. These enhancements can be explained by the optical properties and the shape of the liquid microjet. SFG experiments at the surface of a liquid microjet of ethanol in air show that it is also possible to measure the coherent vibrational SFG spectrum of the ethanol/air interface in this way. Our findings are useful for future far-UV or X-ray based nonlinear optical surface experiments on liquid jets. In addition, combined X-ray photoelectron spectroscopy and SHG/SFG measurements are feasible, which will be very useful in improving our understanding of the molecular foundations of electrostatic and chemical surface properties and phenomena.

  7. Second harmonic generation microscopy analysis of extracellular matrix changes in human idiopathic pulmonary fibrosis

    PubMed Central

    Tilbury, Karissa; Hocker, James; Wen, Bruce L.; Sandbo, Nathan; Singh, Vikas; Campagnola, Paul J.

    2014-01-01

    Abstract. Patients with idiopathic fibrosis (IPF) have poor long-term survival as there are limited diagnostic/prognostic tools or successful therapies. Remodeling of the extracellular matrix (ECM) has been implicated in IPF progression; however, the structural consequences on the collagen architecture have not received considerable attention. Here, we demonstrate that second harmonic generation (SHG) and multiphoton fluorescence microscopy can quantitatively differentiate normal and IPF human tissues. For SHG analysis, we developed a classifier based on wavelet transforms, principle component analysis, and a K-nearest-neighbor algorithm to classify the specific alterations of the collagen structure observed in IPF tissues. The resulting ROC curves obtained by varying the numbers of principal components and nearest neighbors yielded accuracies of >95%. In contrast, simpler metrics based on SHG intensity and collagen coverage in the image provided little or no discrimination. We also characterized the change in the elastin/collagen balance by simultaneously measuring the elastin autofluorescence and SHG intensities and found that the IPF tissues were less elastic relative to collagen. This is consistent with known mechanical consequences of the disease. Understanding ECM remodeling in IPF via nonlinear optical microscopy may enhance our ability to differentiate patients with rapid and slow progression and, thus, provide better prognostic information. PMID:25134793

  8. Direct-substitution method for studying second harmonic generation in arbitrary optical superlattices

    NASA Astrophysics Data System (ADS)

    Chen, Ying; Yang, Xiangbo

    In this paper, we present the direct-substitution (DS) method to study the second-harmonic generation (SHG) in arbitrary one-dimensional optical superlattices (OS). Applying this method to Fibonacci and generalized Fibonacci systems, we obtain the relative intensity of SHG and compare them with previous works. We confirmed the validity of the proposed DS method by comparing our results of SHG in quasiperiodic Fibonacci OS with previous works using analytical Fourier transform method. Furthermore, the three-dimension SHG spectra obtained by DS method present the properties of SHG in Fibonacci OS more distinctly. What's more important, the DS method demands very few limits and can be used to compute directly and conveniently the intensity of SHG in arbitrary OS where the quasi-phase-matching (QPM) can be achieved. It shows that the DS method is powerful for the calculation of electric field and intensity of SHG and can help experimentalists conveniently to estimate the distributions of SHG in any designed polarized systems.

  9. Characterization of salt interferences in second-harmonic generation detection of protein crystals

    PubMed Central

    Closser, R. G.; Gualtieri, E. J.; Newman, J. A.; Simpson, G. J.

    2013-01-01

    Studies were undertaken to assess the merits and limitations of second-harmonic generation (SHG) for the selective detection of protein and polypeptide crystal formation, focusing on the potential for false positives from SHG-active salts present in crystallization media. The SHG activities of salts commonly used in protein crystallization were measured and quantitatively compared with reference samples. Out of 19 salts investigated, six produced significant background SHG and 15 of the 96 wells of a sparse-matrix screen produced SHG upon solvent evaporation. SHG-active salts include phosphates, hydrated sulfates, formates and tartrates, while chlorides, acetates and anhydrous sulfates resulted in no detectable SHG activity. The identified SHG-active salts produced a range of signal intensities spanning nearly three orders of magnitude. However, even the weakest SHG-active salt produced signals that were several orders of magnitude greater than those produced by typical protein crystals. In general, SHG-active salts were identifiable through characteristically strong SHG and negligible two-photon-excited ultraviolet fluorescence (TPE-UVF). Exceptions included trials containing either potassium dihydrogen phosphate or ammonium formate, which produced particularly strong SHG, but with residual weak TPE-UVF signals that could potentially complicate discrimination in crystallization experiments using these precipitants. PMID:24282335

  10. Photoinduced anisotropy of second-harmonic generation from azobenzene-modified alkylsiloxane monolayers

    NASA Astrophysics Data System (ADS)

    Yi, Y. W.; Furtak, T. E.; Farrow, M. J.; Walba, D. M.

    2003-09-01

    Noncontact alignment of liquid crystal displays offers the advantage of reduced contamination and minimal surface charging. This approach also provides a means of reversible alignment after a device has been assembled. With this objective we have synthesized self-assembled monolayers based on dimethylaminoazobenzene units covalently attached to a glass surface by means of a short alkylsiloxane anchor, a derivatized version of methyl red (d-MR). The resulting architecture favors an orientation in which the axis of the azobenzene group should be nearly parallel to the surface with an isotropic azimuthal distribution. Under illumination with polarized light the trans-cis isomerization and subsequent relaxation serves to wiggle the molecule into an orientation perpendicular to the treatment polarization. We have tested this scenario using optical second harmonic generation and supporting optical techniques. We are able to identify a surface order parameter that characterizes the photoalignment of the azobenzene group, and have shown that the treatment illumination promotes the formation of H aggregates of the azobenzene species. We have also demonstrated that the treated d-MR layer successfully aligns a nematic liquid crystal.

  11. Second-harmonic generation microscopy of photocurable polymer intrastromal implants in ex-vivo corneas

    PubMed Central

    Bueno, Juan M.; Palacios, Raquel; Pennos, Alexandros; Artal, Pablo

    2015-01-01

    A custom adaptive-optics (AO) multiphoton microscope was used to visualize the corneal stroma after the insertion of a photocurable polymer material. A lamellar pocket was created and a certain amount of polymer in liquid form was injected. This turned into a rigid film after UV irradiation. Intact eyes were used as control. Tomographic and regular second harmonic generation (SHG) microscopy images were recorded from both control and corneas with polymer implants. In control corneas, the SHG signal decreased uniformly with depth. However, treated corneas exhibited an abrupt loss of SHG signal at the implant location. The use of AO increased the SHG levels and improved the visualization of the stroma, not only at deeper corneal layers but also beneath the implant. Moreover, the absence of SHG signal from the implant allowed its geometrical characterization (thickness and location). This technique offers a potential tool for non-invasive analysis of morphological changes in the cornea after surgery or treatment, and might be useful in future clinical environments. PMID:26114039

  12. Efficient second-harmonic imaging of collagen in histological slides using Bessel beam excitation

    PubMed Central

    Vuillemin, Nelly; Mahou, Pierre; Débarre, Delphine; Gacoin, Thierry; Tharaux, Pierre-Louis; Schanne-Klein, Marie-Claire; Supatto, Willy; Beaurepaire, Emmanuel

    2016-01-01

    Second-harmonic generation (SHG) is the most specific label-free indicator of collagen accumulation in widespread pathologies such as fibrosis, and SHG-based measurements hold important potential for biomedical analyses. However, efficient collagen SHG scoring in histological slides is hampered by the limited depth-of-field of usual nonlinear microscopes relying on focused Gaussian beam excitation. In this work we analyze theoretically and experimentally the use of Bessel beam excitation to address this issue. Focused Bessel beams can provide an axially extended excitation volume for nonlinear microscopy while preserving lateral resolution. We show that shaping the focal volume has consequences on signal level and scattering directionality in the case of coherent signals (such as SHG) which significantly differ from the case of incoherent signals (two-photon excited fluorescence, 2PEF). We demonstrate extended-depth SHG-2PEF imaging of fibrotic mouse kidney histological slides. Finally, we show that Bessel beam excitation combined with spatial filtering of the harmonic light in wave vector space can be used to probe collagen accumulation more efficiently than the usual Gaussian excitation scheme. These results open the way to SHG-based histological diagnoses. PMID:27435390

  13. Fully automated muscle quality assessment by Gabor filtering of second harmonic generation images

    NASA Astrophysics Data System (ADS)

    Paesen, Rik; Smolders, Sophie; Vega, José Manolo de Hoyos; Eijnde, Bert O.; Hansen, Dominique; Ameloot, Marcel

    2016-02-01

    Although structural changes on the sarcomere level of skeletal muscle are known to occur due to various pathologies, rigorous studies of the reduced sarcomere quality remain scarce. This can possibly be explained by the lack of an objective tool for analyzing and comparing sarcomere images across biological conditions. Recent developments in second harmonic generation (SHG) microscopy and increasing insight into the interpretation of sarcomere SHG intensity profiles have made SHG microscopy a valuable tool to study microstructural properties of sarcomeres. Typically, sarcomere integrity is analyzed by fitting a set of manually selected, one-dimensional SHG intensity profiles with a supramolecular SHG model. To circumvent this tedious manual selection step, we developed a fully automated image analysis procedure to map the sarcomere disorder for the entire image at once. The algorithm relies on a single-frequency wavelet-based Gabor approach and includes a newly developed normalization procedure allowing for unambiguous data interpretation. The method was validated by showing the correlation between the sarcomere disorder, quantified by the M-band size obtained from manually selected profiles, and the normalized Gabor value ranging from 0 to 1 for decreasing disorder. Finally, to elucidate the applicability of our newly developed protocol, Gabor analysis was used to study the effect of experimental autoimmune encephalomyelitis on the sarcomere regularity. We believe that the technique developed in this work holds great promise for high-throughput, unbiased, and automated image analysis to study sarcomere integrity by SHG microscopy.

  14. Stacking order dependent second harmonic generation and topological defects in h-BN bilayers.

    PubMed

    Kim, Cheol-Joo; Brown, Lola; Graham, Matt W; Hovden, Robert; Havener, Robin W; McEuen, Paul L; Muller, David A; Park, Jiwoong

    2013-01-01

    The ability to control the stacking structure in layered materials could provide an exciting approach to tuning their optical and electronic properties. Because of the lower symmetry of each constituent monolayer, hexagonal boron nitride (h-BN) allows more structural variations in multiple layers than graphene; however, the structure-property relationships in this system remain largely unexplored. Here, we report a strong correlation between the interlayer stacking structures and optical and topological properties in chemically grown h-BN bilayers, measured mainly by using dark-field transmission electron microscopy (DF-TEM) and optical second harmonic generation (SHG) mapping. Our data show that there exist two distinct h-BN bilayer structures with different interlayer symmetries that give rise to a distinct difference in their SHG intensities. In particular, the SHG signal in h-BN bilayers is observed only for structures with broken inversion symmetry, with an intensity much larger than that of single layer h-BN. In addition, our DF-TEM data identify the formation of interlayer topological defects in h-BN bilayers, likely induced by local strain, whose properties are determined by the interlayer symmetry and the different interlayer potential landscapes.

  15. Protein Conformational Changes Are Detected and Resolved Site Specifically by Second-Harmonic Generation

    PubMed Central

    Moree, Ben; Connell, Katelyn; Mortensen, Richard B.; Liu, C. Tony; Benkovic, Stephen J.; Salafsky, Joshua

    2015-01-01

    We present here a straightforward, broadly applicable technique for real-time detection and measurement of protein conformational changes in solution. This method is based on tethering proteins labeled with a second-harmonic generation (SHG) active dye to supported lipid bilayers. We demonstrate our method by measuring the conformational changes that occur upon ligand binding with three well-characterized proteins labeled at lysine residues: calmodulin (CaM), maltose-binding protein (MBP), and dihydrofolate reductase (DHFR). We also create a single-site cysteine mutant of DHFR engineered within the Met20 catalytic loop region and study the protein’s structural motion at this site. Using published x-ray crystal structures, we show that the changes in the SHG signals upon ligand binding are the result of structural motions that occur at the labeled sites between the apo and ligand-bound forms of the proteins, which are easily distinguished from each other. In addition, we demonstrate that different magnitudes of the SHG signal changes are due to different and specific ligand-induced conformational changes. Taken together, these data illustrate the potential of the SHG approach for detecting and measuring protein conformational changes for a wide range of biological applications. PMID:26287632

  16. In situ time-series monitoring of collagen fibers produced by standing-cultured osteoblasts using a second-harmonic-generation microscope.

    PubMed

    Hase, Eiji; Matsubara, Oki; Minamikawa, Takeo; Sato, Katsuya; Yasui, Takeshi

    2016-04-20

    In bone tissue engineering and regeneration, there is a considerable need for an unstained method of monitoring collagen fibers produced by osteoblasts. This is because collagen fibers play an important role as a bone matrix and continuous monitoring of their temporal dynamics is important in clarifying the organization process toward forming bone tissue. In the work described here, using a second-harmonic-generation (SHG) microscope, we performed in situ time-series monitoring of collagen fibers produced by cultured osteoblasts without the need for staining. Use of the 19 fs near-infrared pulsed light enables us to visualize the temporal dynamics in a thin layer of collagen fibers produced by a single layer of osteoblasts in high-contrast SHG images. While the collagen fibers were produced and stored inside the osteoblasts at an early stage of culturing, the network structure of collagen fibers was formed and locally condensed at a late stage. Furthermore, we extracted a quantitative parameter of collagen maturity degree in the cultured sample by use of image analysis based on a two-dimensional Fourier transform of the SHG image. The proposed method will be useful for in situ quality and quantity control of collagen fibers in bone tissue engineering and regeneration.

  17. Broadband electric-field-induced LP01 and LP02 second harmonic generation in Xe-filled hollow-core PCF.

    PubMed

    Ménard, Jean-Michel; Köttig, Felix; St J Russell, Philip

    2016-08-15

    Second harmonic (SH) generation with 300 fs pump pulses is reported in a xenon-filled hollow-core photonic crystal fiber (PCF) across which an external bias voltage is applied. Phase-matched intermodal conversion from a pump light in the LP01 mode to SH light in the LP02 mode is achieved at a particular gas pressure. Using periodic electrodes, quasi-phase-matched SH generation into the low-loss LP01 mode is achieved at a different pressure. The low linear dispersion of the gas enables phase-matching over a broad spectral window, resulting in a measured bandwidth of ∼10  nm at high pump energies. A conversion efficiency of ∼18%/mJ is obtained. Gas-filled anti-resonant-reflecting hollow-core PCF uniquely offers pressure-tunable phase-matching, ultra-broadband guidance, and a very high optical damage threshold, which hold great promise for efficient three-wave mixing, especially in difficult-to-access regions of the electromagnetic spectrum.

  18. Optical system design of a speckle-free ultrafast Red-Green-Blue (RGB) source based on angularly multiplexed second harmonic generation from a TZDW source

    NASA Astrophysics Data System (ADS)

    Yao, Yuhong; Knox, Wayne H.

    2015-03-01

    We report the optical system design of a novel speckle-free ultrafast Red-Green-Blue (RGB) source based on angularly multiplexed simultaneous second harmonic generation from the efficiently generated Stokes and anti-Stokes pulses from a commercially available photonic crystal fiber (PCF) with two zero dispersion wavelengths (TZDW). We describe the optimized configuration of the TZDW fiber source which supports excitations of dual narrow-band pulses with peak wavelengths at 850 nm, 1260 nm and spectral bandwidths of 23 nm, 26 nm, respectively within 12 cm of commercially available TZDW PCF. The conversion efficiencies are as high as 44% and 33% from the pump source (a custom-built Yb:fiber master-oscillator-power-amplifier). As a result of the nonlinear dynamics of propagation, the dual pulses preserve their ultrashort pulse width (with measured autocorrelation traces of 200 fs and 227 fs,) which eliminates the need for dispersion compensation before harmonic generation. With proper optical design of the free-space harmonic generation system, we achieve milli-Watt power level red, green and blue pulses at 630 nm, 517 nm and 425 nm. Having much broader spectral bandwidths compared to picosecond RGB laser sources, the source is inherently speckle-free due to the ultra-short coherence length (<37 μm) while still maintaining an excellent color rendering capability with >99.4% excitation purities of the three primaries, leading to the coverage of 192% NTSC color gamut (CIE 1976). The reported RGB source features a very simple system geometry, its potential for power scaling is discussed with currently available technologies.

  19. Second harmonic generation microscopy is a novel technique for differential diagnosis of breast fibroepithelial lesions.

    PubMed

    Tan, Wai Jin; Yan, Jie; Xu, Shuoyu; Thike, Aye Aye; Bay, Boon Huat; Yu, Hanry; Tan, Min-Han; Tan, Puay Hoon

    2015-12-01

    Breast fibroepithelial lesions, including fibroadenomas and phyllodes tumours, are commonly encountered in clinical practice. As histological differences between these two related entities may be subtle, resulting in a challenging differential diagnosis, pathological techniques to assist the differential diagnosis of these two entities are of high interest. An accurate diagnosis at biopsy is important given corresponding implications for clinical decision-making including surgical extent and monitoring. Second harmonic generation (SHG) microscopy is a recently developed optical imaging technique capable of robust, powerful and unbiased label-free direct detection of collagen fibril structure in tissue without the use of antibodies. We constructed tissue microarrays emulating limited materials on biopsy to investigate quantitative collagen signal in fibroepithelial lesions using SHG microscopy. Archived formalin-fixed paraffin-embedded materials of 47 fibroepithelial lesions (14 fibroadenomas and 33 phyllodes tumours) were evaluated. Higher collagen signal on SHG microscopy was observed in fibroadenomas than phyllodes tumours on SHG imaging (p<0.001, area under the curve 0.859). At an automated threshold (2.5 million positive pixels), the sensitivity and specificity of the SHG microscopy for fibroadenoma classification was 71.4% and 84.4%, respectively. To corroborate these findings, we performed immunohistochemistry on tissue array sections using collagen I and III primary antibodies. Both collagen I and III immunohistochemical expressions were also significantly higher in fibroadenomas than in phyllodes tumours (p<0.001). In conclusion, label-free collagen quantitation on SHG microscopy is a novel imaging approach that can aid the differential diagnosis of fibroepithelial lesions.

  20. Quantitative second harmonic generation imaging of the diseased state osteogenesis imperfecta: experiment and simulation.

    PubMed

    Lacomb, Ronald; Nadiarnykh, Oleg; Campagnola, Paul J

    2008-06-01

    We report the integrated use of 3D second harmonic generation (SHG) imaging microscopy and Monte Carlo simulation as a combined metric to quantifiably differentiate normal and diseased tissues based on the physical properties of the respective extracellular matrix. To achieve this, we have identified a set of parameters comprised of the SHG creation attributes and the bulk optical parameters, which are used collectively via comparative analysis. Monte Carlo simulations of the SHG axial directional and attenuation responses allow their decomposition into the underlying factors that are not readily obtainable through experimental techniques. Specifically, this approach allows for estimation of the SHG creation attributes (directionality and relative conversion efficiency) and separation of primary and secondary filter effects, collectively that form the observed SHG contrast. The quantitative metric is shown for the connective tissue disorder Osteogenesis Imperfecta (characterized by abnormal assembly of type I collagen) using a murine model that expresses the disease in the dermis layer of skin. Structural dissimilarities between the osteogenesis imperfecta mouse and wild-type tissues lead to significant differences in the SHG depth-dependent directionality and signal attenuation. The Monte Carlo simulations of these responses using measured bulk optical parameters reproduce the experimental data trends, and the extracted emission directionality and conversion efficiencies are consistent with independent determinations. The simulations also illustrate the dominance of primary filter affects on overall SHG generation and attenuation. Thus, the combined method of 3D SHG imaging and modeling forms an essential foundation for parametric description of the matrix properties that are not distinguishable by sole consideration of either bulk optical parameters or SHG alone. Moreover, due to the quasi-coherence of the SHG process in tissues, we submit that this approach

  1. Type-II second-harmonic-generation properties of YCOB and GdCOB single crystals.

    PubMed

    Liu, Yanqing; Qi, Hongwei; Lu, Qingming; Yu, Fapeng; Wang, Zhengping; Xu, Xinguang; Zhao, Xian

    2015-02-09

    As excellent nonlinear optical (NLO) crystals, YCa(4)O(BO(3))(3) (YCOB) and GdCa(4)O(BO(3))(3) (GdCOB) have been paid much attention since their first appearance in 1990's. From that time to now, almost all of related researches and applications have focused on their type-I phase-matching (PM) configurations which possess large effective NLO coefficient (d(eff)). In this paper, type-II second-harmonic-generation (SHG) properties of these two crystals are reported, including PM curve, d(eff), angular acceptance and walk-off angle. Both of the type-II SHG experiments for 1064 and 1320 nm have indicated that the optimum directions which have maximum d(eff) locate in the second octant, i.e. (90° < θ< 180°, 0° < ϕ < 90°). For a (112°, 81.3°)-cut, 24 mm long YCOB crystal, the largest type-II SHG conversion efficiency of a 1064 nm Nd:YAG pico-second laser is 55%, which reaches the same level of the optimum type-I sample. To our knowledge this is the first time that type-II SHG performance of YCOB and GdCOB crystals is investigated intensively. Our research has shown that the smaller d(eff) of type-II PM can be compensated by its larger angular acceptance and less beam walk-off. The same level SHG conversion efficiency implies for such type crystals the type-II components have the potential to replace type-I ones and obtain important NLO applications in the future.

  2. Second-harmonic generation reveals a relationship between metastatic potential and collagen fiber structure

    NASA Astrophysics Data System (ADS)

    Burke, Kathleen A.; Dawes, Ryan P.; Cheema, Mehar K.; Perry, Seth; Brown, Edward

    2014-02-01

    Second Harmonic Generation (SHG) of collagen signals allows for the analysis of collagen structural changes throughout metastatic progression. The directionality of coherent SHG signals, measured through the ratio of the forward-propagating to backward propagating signal (F/B ratio), is affected by fibril diameter, spacing, and order versus disorder of fibril packing within a fiber. As tumors interact with their microenvironment and metastasize, it causes changes in these parameters, and concurrent changes in the F/B ratio. Specifically, the F/B ratio of breast tumors that are highly metastatic to the lymph nodes is significantly higher than those in tumors with restricted lymph node involvement. We utilized in vitro analysis of tumor cell motility through collagen gels of different microstructures, and hence different F/B ratios, to explore the relationship between collagen microstructures and metastatic capabilities of the tumor. By manipulating environmental factors of fibrillogenesis and biochemical factors of fiber composition we created methods of varying the average F/B ratio of the gel, with significant changes in fiber structure occurring as a result of alterations in incubation temperature and increasing type III collagen presence. A migration assay was performed using simultaneous SHG and fluorescent imaging to measure average penetration depth of human tumor cells into the gels of significantly different F/B ratios, with preliminary data demonstrating that cells penetrate deeper into gels of higher F/B ratio caused by lower type III collagen concentration. Determining the role of collagen structure in tumor cell motility will aid in the future prediction metastatic capabilities of a primary tumor.

  3. Investigating membrane nanoporation induced by bipolar pulsed electric fields via second harmonic generation

    NASA Astrophysics Data System (ADS)

    Moen, E. K.; Ibey, B. L.; Beier, H. T.; Armani, A. M.

    2016-09-01

    Electric pulses have become an effective tool for transporting cargo (DNA, drugs, etc.) across cell membranes. This enhanced transport is believed to occur through temporary pores formed in the plasma membrane. Traditionally, millisecond duration, monopolar (MP) pulses are used for electroporation, but bipolar (BP) pulses have proven equally effective as MP pulses with the added advantage of less cytotoxicity. With the goal of further reducing cytotoxic effects and inducing non-thermal, intra-cellular effects, researchers began investigating reduced pulse durations, pushing into the nanosecond regime. Cells exposed to these MP, nanosecond pulsed electric fields (nsPEFs) have shown increased repairable membrane permeability and selective channel activation. However, attempts to improve this further by moving to the BP pulse regime has proven unsuccessful. In the present work, we use second harmonic generation imaging to explore the structural effects of bipolar nsPEFs on the plasma membrane. By varying the temporal spacing between the pulse phases over several orders of magnitude and comparing the response to a single MP case, we systematically examine the disparity in cellular response. Our circuit-based model predicts that, as the temporal spacing increases several orders of magnitude, nanoporation increases and eventually exceeds the MP case. On the whole, our experimental data agree with this assertion; however, a detailed analysis of the data sets demonstrates that biological processes may play a larger role in the observed response than previously thought, dominating the effect for temporal spacing up to 5 μs. These findings could ultimately lead to understanding the biophysical mechanism underlying all electroporation.

  4. Measuring strain using digital image correlation of second harmonic generation images.

    PubMed

    Wentzell, Scott; Sterling Nesbitt, Robert; Macione, James; Kotha, Shiva

    2013-08-09

    The micromechanical environment of bone is crucial to understanding both bone fracture and mechanobiological responses of osteocytes, yet few techniques exist that are capable of measuring strains on the micrometer scale. A method for measuring micrometer level strains has been developed based on digital image correlation (DIC) of second harmonic generation microscopy (SHGM) images. Bovine tibias milled into thin sections were imaged using SHGM under loads of 0 and 15 MPa. Strains were measured using DIC and compared to applied strain values. First and second principal strains decreased in magnitude as the analysis region area increased from 1750 µm(2) to 60,920 µm(2), converging to 1.23 ± 0.74 and -0.745 ± 0.9816 times the applied strain respectively. A representative sample histogram revealed regions of pure tensile and compressive strain, and that strains were highly heterogeneous ranging from 8410 to -8840 microstrain for an applied 2870 microstrain. Comparison with applied strain measures suggested that analysis sizes of 1750 µm(2) and greater were measuring strains on the tissue scale, and higher resolution is required for collagen fibrillar strains. Regions of low SHGM intensity ("dark" regions) were seen which are believed to be lacunar and perilacunar regions of low collagen density. However, no significant differences in strain magnitude were present in dark regions versus regions of high signal intensity. The proposed technique is effective for strains on the size order of bone microarchitecture, and would be useful for studies into the mechanical microenvironment during loading. The technique also has potential for in vivo studies in small animal models.

  5. Spectroscopic studies of magnesium plasma produced by fundamental and second harmonics of Nd:YAG laser

    SciTech Connect

    Haq, S. U. Ahmat, L.; Mumtaz, M.; Nadeem, A.; Shakeel, Hira; Mahmood, S.

    2015-08-15

    In the present experimental work, laser induced magnesium plasma has been characterized using plasma parameters. The plasma has been generated by the fundamental (1064 nm) and second harmonics (532 nm) of Nd:YAG laser. The plasma parameters such as electron temperature and electron number density have been extracted using Boltzmann plot method and Stark broadened line profile, respectively. The laser irradiance dependence and spatial behavior of electron temperature and number density in laser induced magnesium plasma have been studied. The electron temperature as a function of laser irradiance (0.5 to 6.5 GW/cm{sup 2}) ranges from (9.16–10.37) × 10{sup 3 }K and (8.5–10.1)× 10{sup 3 }K, and electron number density from (0.99–1.08) × 10{sup 16} cm{sup −3} and (1.04–1.22) × 10{sup 16}cm{sup −3} for 1064 and 532 nm, respectively. These parameters exhibit fast increase at low laser irradiance and slow increase at high irradiance. The spatial distribution of electron temperature and electron number density shows same decreasing trend up to 2.25 mm from the target surface. The electron temperature and number density decrease from (9.5–8.6) × 10{sup 3 }K, (1.27–1.15) × 10{sup 16}cm{sup −3} and (10.56–8.85)× 10{sup 3 }K, (1.08–0.99) × 10{sup 16} cm{sup −3} for 532 nm and 1064 nm laser ablation wavelengths, respectively.

  6. Forward- and backward-second harmonic generation imaging of corneal and scleral collagen

    NASA Astrophysics Data System (ADS)

    Lo, Wen; Tan, Hsin-Yuan; Lin, Ming-Guo; Hsueh, Chu-Mei; Chen, Wei-Liang; Lin, Sung-Jan; Jee, Shiou-Hwa; Dong, Chen-Yuan

    2008-02-01

    Collagen is the most abundant protein in mammalian and forms various types of tissues. On ocular surface, sclera, limbus and cornea are composed with fibril form collagen. However, unlike other connective tissues with high opacity, cornea has extraordinary high transparency which originates from the regular arrangement of collagen fibers within cornea. Cornea is responsible for 80% of focusing power of our vision and any corneal damage can cause severe vision loss. The high transparency of cornea makes it difficult to probe it without invasive processes, especially stromal structure alternations. Collagen, however, is an effective second harmonic generator due to its non-centrosymmetric molecule structure and can be visualized with nonlinear optical process without labeling. In addition, the deeper penetration and point like effective volume of SHG can also provide 3-dimensional information with minimum invasion. Backward SHG imaging has been approved effectively demonstrating structure alternation in infective keratitis, thermal damage in cornea, corneal scar, post refractive surgery wound healing and keratoconus which is also a main complication after refractive surgery[1-6]. In practical, backward SHG has the potentiality to be developed as clinical examination modality. However, Han et al also demonstrated that backward SHG (BSHG) imaging provides collagen bundle information while forward SHG (FSHG) provides more detailed, submicron fibril structure visualization within corneal stroma[7]. In sclera, which also has type I collagen as its main composition, BSHG and FSHG imaging reveal similar morphology. Comparing with what Legare et al demonstrated that BSHG in bulk tissue mainly originate from backscattered FSHG[8], the huge difference between corneal BSHG and FSHG imaging originate from the high transparency of cornea. However, only BSHG could be applied in practical. Therefore, if the correlation of BSHG and FSHG, which reveals more architecture details, can

  7. Second harmonic super-resolution microscopy for quantification of mRNA at single copy sensitivity.

    PubMed

    Liu, Jing; Cho, Il-Hoon; Cui, Yi; Irudayaraj, Joseph

    2014-12-23

    Cell-specific information on the quantity and localization of key mRNAs at single copy sensitivity in single cells is critical for evaluating basic cellular process, disease risk, and efficacy of therapy. Quantification of overexpressed mRNAs beyond the diffraction limit is constrained by the optical property of the probes and microscopy techniques. In this report, nanosized barium titanium oxide (BaTiO3, BTO) crystals were utilized as probes for mRNA quantification by a second harmonic super-resolution microscopy (SHaSM). The SHaSM was able to detect a single copy of the human epidermal growth factor receptor 2 (Her2) mRNA at a resolution of 55.6 nm with the ability to resolve multiple mRNA copies in a diffraction-limited spot. Her2 mRNA per cell was counted in SK-BR-3, MCF-7, and HeLa cell lines as 595±79.1, 38.9±8.26, and 1.5±2.8, respectively. Our single-cell quantification results were validated with the fluorescence in situ hybridization studies and quantitative PCR, showing better specificity and selectivity over current single-molecule approaches for transcript detection. The SHaSM is expected to have an upper limit of resolving ∼10(4) transcripts in a single cell with the ability to monitor intracellular transcriptional dynamics at video rate. The developed approach has strong potential in clinical research and in the early diagnosis of life-threatening diseases such as cancer.

  8. Second-harmonic generation for studying structural motion of biological molecules in real time and space.

    PubMed

    Salafsky, Joshua S

    2007-11-14

    SHG and sum-frequency generation (SFG) are surface-selective, nonlinear optical techniques whose ability to measure the average tilt angle of molecules on surfaces is well known in non-biological systems. By labeling molecules with a second-harmonic-active dye probe, SHG detection is extended to any biological molecule. The method has been used in previous work to detect biomolecules at an interface and their ligand-induced conformational changes. Here I demonstrate that SHG can be used to study structural motion quantitatively using a probe placed at a specific site (Cys-77) in adenylate kinase, a protein. The protein is also labeled non-site-specifically via amines. Labeled protein is absorbed to a surface and a baseline SH signal is measured. Upon introducing ATP, AMP or a specific inhibitor, AP(5)A, the baseline signal changes depending on the ligand and the labeling site. In particular, a substantial change in SH intensity is produced upon binding ATP to the amine-labeled protein, consistent with the X-ray crystal structures. In contrast, SHG polarization measurements are used to quantitatively determine that no rotation occurs at site Cys-77, in agreement with the lack of motion observed at this site in the X-ray crystal structures. A method for building a global map of conformational change in real time and space is proposed using a set of probes placed at different sites in a biomolecule. For this purpose, SH-active unnatural amino acids are attractive complements to exogenous labels.

  9. Investigating backward scattered second harmonic generation from various mouse collagen tissues

    NASA Astrophysics Data System (ADS)

    Shen, Mengzhe; Tian, Yunxian; Chong, Shau Poh; Zhao, Jianhua; Zeng, Haishan; Tang, Shuo

    2014-02-01

    A confocal multiphoton microscopy system with various detection pinholes was used to differentiate backward scattered second harmonic generation (BS-SHG) from backward generated SHG (BG-SHG) based on the fact that BS-SHG is more scattered and therefore has a much bigger spot size than BG-SHG. BS-SHG is quantified from two types of mouse tissues, such as Achilles tendon, and skin, and at various focal depths. It is found that the BS-SHG contributes less to the total backward SHG for the skin than Achilles tendon with thicknesses of around three hundred micrometers. For tissue with larger F/B intensity ratio such as Achilles tendon, increasing the tissue thickness reduces it tremendously. However, for tissue with smaller F/B intensity ratio, tissue thickness increment does not alter it significantly. In addition, larger F/B intensity ratio might be related with a greater scattering coefficient from our Achilles tendon and skin comparison. When the focal point is moved deeper into tissue, the contribution of BS-SHG is found to decrease due to a reduced pass length of the forward propagated photons. On the contrary, when the tissue thickness increases, the contribution of the BS-SHG is increased. These observations for thicker skin tissues are related with our F/B intensity ratio measurement for thin mouse skin sample in terms of that the magnitude of backward generated SHG are dominant among the total backward SHG in mouse skin tissue. Considering the phase mismatching condition in the forward and backward directions, these results may indicate that quasi-phase matching originating from the regular structure of collagen could help with reducing the phase mismatch especially in the backward direction.

  10. Frequency-resolved optical gating with the use of second-harmonic generation

    SciTech Connect

    DeLong, K.W.; Trebino, R. ); Hunter, J.; White, W.E. )

    1994-11-01

    We discuss the use of second-harmonic generation (SHG) as the nonlinearity in the technique of frequency-resolved optical gating (FROG) for measuring the full intensity and phase evolution of an arbitrary ultrashort pulse. FROG that uses a third-order nonlinearity in the polarization-gate geometry has proved extremely successful, and the algorithm required for extraction of the intensity and the phase from the experimental data is quite robust. However, for pulse intensities less than [similar to] 1 MW, third-order nonlinearities generate insufficient signal strength, and therefore SHG FROG appears necessary. We discuss the theoretical, algorithmic, and experimental considerations of SHG FROG in detail. SHG FROG has an ambiguity in the direction of time, and its traces are somewhat unintuitive. Also, previously published algorithms are generally ineffective at extracting the intensity and the phase of an arbitrary laser pulse from the SHG FROG trace. We present an improved pulse-retrieval algorithm, based on the method of generalized projections, that is far superior to the previously published algorithms, although it is still not so robust as the polarization-gate algorithm. We discuss experimental sources of error such as pump depletion and group-velocity mismatch. We also present several experimental examples of pulses measured with SHG FROG and show that the derived intensities and phases are in agreement with more conventional diagnostic techniques, and we demonstrate the high-dynamic-range capability of SHG FROG. We conclude that, despite the above drawbacks, SHG FROG should be useful in measuring low-energy pulses.

  11. Second harmonic generation quantitative measurements on collagen fibrils through correlation to electron microscopy

    NASA Astrophysics Data System (ADS)

    Bancelin, S.; Aimé, C.; Gusachenko, I.; Kowalczuk, L.; Latour, G.; Coradin, T.; Schanne-Klein, M.-C.

    2015-03-01

    Type I collagen is a major structural protein in mammals that shows highly structured macromolecular organizations specific to each tissue. This biopolymer is synthesized as triple helices, which self-assemble into fibrils (Ø =10-300 nm) and further form various 3D organization. In recent years, Second Harmonic Generation (SHG) microscopy has emerged as a powerful technique to probe in situ the fibrillar collagenous network within tissues. However, this optical technique cannot resolve most of the fibrils and is a coherent process, which has impeded quantitative measurements of the fibril diameter so far. In this study, we correlated SHG microscopy with Transmission Electron Microscopy to determine the sensitivity of SHG microscopy and to calibrate SHG signals as a function of the fibril diameter in reconstructed collagen gels. To that end, we synthetized isolated fibrils with various diameters and successfully imaged the very same fibrils with both techniques, down to 30 nm diameter. We observed that SHG signals scaled as the fourth power of the fibril diameter, as expected from analytical and numerical calculations. This calibration was then applied to diabetic rat cornea in which we successfully recovered the diameter of hyperglycemia-induced fibrils in the Descemet's membrane without having to resolve them. Finally we derived the first hyperpolarizability from a single collagen triple helix which validates the bottom-up approach used to calculate the non-linear response at the fibrillar scale and denotes a parallel alignment of triple helices within the fibrils. These results represent a major step towards quantitative SHG imaging of nm-sized collagen fibrils.

  12. Second harmonic generation in a KNbO3 nanorod and its detection by using a near-field scanning optical microscope

    NASA Astrophysics Data System (ADS)

    Park, D. J.; Kang, P. G.; Jung, J. H.; Lee, H. H.; Choi, S. B.

    2016-04-01

    We report on an observation of second harmonic generation in an individual KNbO3 nanorod by using a near-field scanning optical microscope. The second harmonic is successfully generated by irradiating with a femtosecond laser having center wavelengths of 1200, 1100, and 972 nm. Such a second harmonic yield shows a clear dependence on the incident laser polarization, where maximum yield is obtained when the incident laser polarization is parallel to the long axis of an individual nanorod. A spatially-resolved second harmonic image shows a bright spot at the edge of the nanorod, which is attributed to the elaborated intensity of both fundamental laser light and second harmonic light inside the nanowire owing to cavity-mode formation.

  13. Polarization Second Harmonic Generation Discriminates Between Fresh and Aged Starch-Based Adhesives Used in Cultural Heritage.

    PubMed

    Psilodimitrakopoulos, Sotiris; Gavgiotaki, Evaggelia; Melessanaki, Kristallia; Tsafas, Vassilis; Filippidis, George

    2016-10-01

    In this work, we report that polarization second harmonic generation (PSHG) microscopy, commonly used in biomedical imaging, can quantitatively discriminate naturally aged from fresh starch-based glues used for conservation or restoration of paintings, works of art on paper, and books. Several samples of fresh and aged (7 years) flour and starch pastes were investigated by use of PSHG. In these types of adhesives, widely used in cultural heritage conservation, second harmonic generation (SHG) contrast originates primarily from the starch granules. It was found that in aged glues, the starch SHG effective orientation (SHG angle, θ) shifts to significantly higher values in comparison to the fresh granules. This shift is attributed to the different degree of granule hydration between fresh and aged adhesives. Thus noninvasive high-resolution nonlinear scattering can be employed to detect and quantify the degree of deterioration of restoration adhesives and to provide guidance toward future conservation treatments.

  14. Controlling second-harmonic generation at the nanoscale with monolithic AlGaAs-on-AlOx antennas.

    PubMed

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

    2017-03-17

    We review recent achievements in the field of nanoscale nonlinear AlGaAs photonics based on all-dielectric optical antennas. After discussing the motivation and main technological challenges for the development of an AlGaAs monolithic platform for χ ((2)) nonlinear nanophotonics, we present numerical and experimental investigations of the second-order nonlinear response and physical reasons for high efficiency of second-order nonlinear interactions in the AlGaAs nano-antennas. In particular, we emphasize the role of the dipolar resonances at the fundamental frequency and the multipolar resonances at the second harmonic wavelength. We also discuss second-harmonic generation directionality and show possible strategies to engineer the radiation pattern of nonlinear antennas.

  15. Controlling second-harmonic generation at the nanoscale with monolithic AlGaAs-on-AlOx antennas

    NASA Astrophysics Data System (ADS)

    Carletti, L.; Rocco, D.; Locatelli, A.; De Angelis, C.; Gili, V. F.; Ravaro, M.; Favero, I.; Leo, G.; Finazzi, M.; Ghirardini, L.; Celebrano, M.; Marino, G.; Zayats, A. V.

    2017-03-01

    We review recent achievements in the field of nanoscale nonlinear AlGaAs photonics based on all-dielectric optical antennas. After discussing the motivation and main technological challenges for the development of an AlGaAs monolithic platform for χ (2) nonlinear nanophotonics, we present numerical and experimental investigations of the second-order nonlinear response and physical reasons for high efficiency of second-order nonlinear interactions in the AlGaAs nano-antennas. In particular, we emphasize the role of the dipolar resonances at the fundamental frequency and the multipolar resonances at the second harmonic wavelength. We also discuss second-harmonic generation directionality and show possible strategies to engineer the radiation pattern of nonlinear antennas.

  16. Influence of semicrystalline order on the second-harmonic generation efficiency in the anisotropic bands of myocytes

    NASA Astrophysics Data System (ADS)

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

    2007-04-01

    The influence of semicrystalline order on the second-harmonic generation (SHG) efficiency in the anisotropic bands of Drosophila melanogaster sarcomeres from larval and adult muscle has been investigated. Differences in the semicrystalline order were obtained by using wild-type and mutant strains containing different amounts of headless myosin. The reduction in semicrystalline order without altering the chemical composition of myofibrils was achieved by observing highly stretched sarcomeres and by inducing a loss of viability in myocytes. In all cases the reduction of semicrystalline order in anisotropic bands of myocytes resulted in a substantial decrease in SHG. Second-harmonic imaging during periodic contractions of myocytes revealed higher intensities when sarcomeres were in the relaxed state compared with the contracted state. This study demonstrates that an ordered semicrystalline arrangement of anisotropic bands plays a determining role in the efficiency of SHG in myocytes.

  17. Investigation of thermally-induced phase mismatching in continuous-wave second harmonic generation: a theoretical model.

    PubMed

    Sabaeian, Mohammad; Mousave, Laleh; Nadgaran, Hamid

    2010-08-30

    A fraction of the fundamental beam energy deposited into nonlinear crystals to generate second harmonic waves (SHW) causes a temperature gradient within the crystal. This temperature inhomogeneity can alter the refractive index of the medium leading to a well-known effect called thermal dispersion. Therefore, the generated SHW suffers from thermal lensing and a longitudinal thermal phase mismatching. In this work by coupling the heat equation with second harmonic generation (SHG) formalism applied to type-II configuration along with walk-off effect, we investigate the continuous wave (CW) SHW beam profile and conversion efficiency when a non-linear KTP crystal is under induced thermal load. We have demonstrated for average and high powers, the thermal de-phasing lead to considerable reduction in SHG compared to an ideal case in which induced heat is neglected.

  18. Terahertz-pulse generation by photoionization of air with laser pulses composed of both fundamental and second-harmonic waves.

    PubMed

    Kress, Markus; Löffler, Torsten; Eden, Susanne; Thomson, Mark; Roskos, Hartmut G

    2004-05-15

    Intense radiation in the terahertz (THz) frequency range can be generated by focusing of an ultrashort laser pulse composed of both a fundamental wave and its second-harmonic field into air, as reported previously by Cook et al. [Opt. Lett. 25, 1210 (2000)]. We identify a threshold for THz generation that proves that generation of a plasma is required and that the nonlinearity of air is insufficient to explain our measurements. An additional THz field component generated in the type I beta-barium borate crystal used for second-harmonic generation has to be considered if one is to avoid misinterpretation of this kind of experiment. We conclude with a comparison that shows that the plasma emitter is competitive with other state-of-the-art THz emitters.

  19. Scalar time domain modeling and coupling of second harmonic generation process in GaAs discontinuous optical waveguide.

    PubMed

    Massaro, A; Tasco, V; Todaro, M T; Cingolani, R; De Vittorio, M; Passaseo, A

    2008-09-15

    We present in this work the scalar potential formulation of second harmonic generation process in chi((2)) nonlinear analysis. This approach is intrinsically well suited to the applications of the concept of circuit analysis and synthesis to nonlinear optical problems, and represents a novel alternative method in the analysis of nonlinear optical waveguide, by providing a good convergent numerical solution. The time domain modeling is applied to nonlinear GaAs asymmetrical waveguide with dielectric discontinuities in the hypothesis of quasi phase matching condition in order to evaluate the efficiency conversion of the second harmonic signal. The accuracy of the modeling is validated by the good agreement with the published experimental results. The effective dielectric constant method allows to extend the analysis also to 3D optical waveguides.

  20. Model of third harmonic generation and electric field induced optical second harmonic using simplified bond-hyperpolarizability model

    NASA Astrophysics Data System (ADS)

    Alejo-Molina, Adalberto; Hingerl, Kurt; Hardhienata, Hendradi

    2015-04-01

    We report for the first time a comprehensive study of the fourth rank tensor describing third harmonic generation (THG) and electric field induced second harmonic (EFISH) in centrosymmetric material from two different viewpoints: Group Theory (GT) and the Simplified Bond Hyperpolarizability Model (SBHM). We show that the fourth rank tensor related to THG and direct current (DC) EFISH can be reduced to two independent elements whereas SBHM always gives only one, reproducing perfectly well EFISH experimental results in Metal Oxyde Semiconductor (MOS). We argue that it is possible to reduce the fourth rank tensor describing EFISH to a third rank tensor and further deliver a classical explanation of EFISH regarding symmetry breaking where the term containing $r^3$ in the potential immediately leads to second harmonic generation (SHG).

  1. Traveling-Wave Tube Amplifier Second Harmonic as Millimeter-Wave Beacon Source for Atmospheric Propagation Studies

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Wintucky, Edwin G.

    2014-01-01

    This paper presents the design and test results of a CW millimeter-wave satellite beacon source, based on the second harmonic from a traveling-wave tube amplifier and utilizes a novel waveguide multimode directional coupler. A potential application of the beacon source is for investigating the atmospheric effects on Q-band (37-42 GHz) and V/W-band (71- 76 GHz) satellite-to-ground signals.

  2. Traveling-Wave Tube Amplifier Second Harmonic as Millimeter-Wave Beacon Source for Atmospheric Propagation Studies

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Wintucky, Edwin G.

    2014-01-01

    This paper presents the design and test results of a CW millimeter-wave satellite beacon source, based on the second harmonic from a traveling-wave tube amplifier and utilizes a novel waveguide multimode directional coupler. A potential application of the beacon source is for investigating the atmospheric effects on Q-band (37 to 42 GHz) and V/W-band (71 to 76 GHz) satellite-to-ground signals.

  3. Traveling-Wave Tube Amplifier Second Harmonic as Millimeter-Wave Beacon Source for Atmospheric Propagation Studies

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Wintucky, Edwin G.

    2014-01-01

    The design and test results of a novel waveguide multimode directional coupler for a CW millimeter-wave satellite beacon source are presented. The coupler separates the second harmonic power from the fundamental output power of a traveling-wave tube amplifier. A potential application of the beacon source is for investigating the atmospheric effects on Q-band (37 to 42 GHz) and VW-band (71 to 76 GHz) satellite-to-ground signals.

  4. Noise characterization of mode-locked lasers by comparing the power spectra of the fundamental and second-harmonic pulses

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Chen, L. P.; Liu, J. M.

    1995-10-01

    By comparing the noise power spectra of the fundamental pulses and those of the second-harmonic pulses, the peak intensity fluctuation, the pulse-width fluctuation, the pulse timing jitter, and the cross correlation between the pulse width and the peak intensity fluctuations of a mode-locked pulse train can be separately quantified. The noise characteristics of an actively mode-locked Nd:YLF laser are presented to demonstrate this technique.

  5. Suppression and nonlinear excitation of parasitic modes in second harmonic gyrotrons operating in a very high order mode

    SciTech Connect

    Nusinovich, Gregory S.; Pu, Ruifeng; Granatstein, Victor L.

    2015-07-06

    In recent years, there was an active development of high-power, sub-terahertz (sub-THz) gyrotrons for numerous applications. For example, a 0.67 THz gyrotron delivering more than 200 kW with about 20% efficiency was developed. This record high efficiency was achieved because the gyrotron operated in a high-order TE{sub 31,8}-mode with the power of ohmic losses less than 10% of the power of outgoing radiation. That gyrotron operated at the fundamental cyclotron resonance, and a high magnetic field of about 27 T was created by a pulse solenoid. For numerous applications, it is beneficial to use gyrotrons at cyclotron harmonics which can operate in available cryomagnets with fields not exceeding 15 T. However, typically, the gyrotron operation at harmonics faces severe competition from parasitic modes at the fundamental resonance. In the present paper, we consider a similar 0.67 THz gyrotron designed for operation in the same TE{sub 31,8}-mode, but at the second harmonic. We focus on two nonlinear effects typical for interaction between the fundamental and second harmonic modes, viz., the mode suppression and the nonlinear excitation of the mode at the fundamental harmonic by the second harmonic oscillations. Our study includes both the analytical theory and numerical simulations performed with the self-consistent code MAGY. The simulations show that stable second harmonic operation in the TE{sub 31,8} mode is possible with only modest sacrifice of efficiency and power.

  6. [Second-harmonic detection with tunable diode laser absorption spectroscopy of CO and CO2 at 1.58 microm].

    PubMed

    Tu, Xing-Hua; Liu, Wen-Qing; Zhang, Yu-Jun; Dong, Feng-Zhong; Wang, Min; Wang, Tie-Dong; Wang, Xiao-Mei; Liu, Jian-Guo

    2006-07-01

    Tunable diode laser absorption spectroscopy has been applied in the fields of atmospheric chemistry and monitoring pollutant gases as a new method of measuring trace gases. The technique of remote sensing of CO and CO2 at 760 mm Hg pressure with tunable diode laser absorption spectroscopy in the near-infrared region is introduced. And the relationship between the second-harmonic spectrum of CO2 in Lorentzian line shape and the modulation amplitude is also presented.

  7. Efficient second harmonic generation in an on-chip high-Q crystalline microresonator fabricated by femtosecond laser

    NASA Astrophysics Data System (ADS)

    Lin, Jintian; Xu, Yingxin; Fang, Zhiwei; Wang, Min; Fang, Wei; Cheng, Ya

    2016-03-01

    We report on transiently phase matched second harmonic generation in an on-chip lithium niobate (LN) microresonator fabricated by femtosecond laser direct writing followed by focused ion beam milling. We demonstrate a normalized conversion efficiency of 1.1×10-3/mW in the LN microdisk with a diameter of ~102 μm and a thickness of ~700 nm.

  8. Solar tidal variations of coefficients of second harmonic of gravitational potential of Mercury

    NASA Astrophysics Data System (ADS)

    Ferrandiz, Jose; Barkin, Yury

    2010-05-01

    Variations of coefficients of the second harmonic of Mercury potential caused by the solar tides have been studied. In the paper we use analytical expressions for tidal variations of Stoks coefficients obtained for model of the elastic celestial body with concentric distributions of masses and elastic parameters (Love numbers) and their reduced form with using fundamental elastic parameter k2 of the Mercury. Taking into account the resonant properties of the Mercury motion variations of the Mercury potential coefficients we present in the form of Fourier series on the multiple of corresponding arguments of the Mercury orbital theory. Evaluations of the amplitudes and periods of observed variations of Mercury potential have been tabulated for base elastic model of the Mercury characterized by hypothetic elastic parameter (Love number) k2=0.37 (Dehant et al., 2005). Tidal variations of polar moment of inertia of the Mercury (due to tidal deformations) lead to remarkable variations of the Mercury rotation. Tidal variations of the Mercury axial rotation also have been determined and tabulated. From our results it follows that the tide periodic variations of gravitational coefficients of the Mercury in a few orders bigger then corresponding tidal variations of Earth's geopotential coefficients (Ferrandiz, Getino, 1993). Variations coefficients of the second harmonic of Mercury potential. These variations are determined by the known formulae for variations of coefficients of the second harmonic of geopotential (Ferrandiz, Getino, 1993). Here we present these formulae in some special form as applied to the considered problem about the Mercury tidal deformations: ( ) δJ2 = - 3Tα23-2, δC22 = T α21 - α22 -4, δS22 = T α1α2-2, δC21 = Tα1α3, δS21 = T α2α3. Here T = k2(M R3 -ma3 ) = 1.667 × 10-7 is a estimation of some conditional coefficient of tidal deformation of Mercury. m and Rare the mass and the mean radius of Mercury. Here we have used standard values of

  9. Second harmonic generation of q-Gaussian laser beam in preformed collisional plasma channel with nonlinear absorption

    SciTech Connect

    Gupta, Naveen Singh, Arvinder; Singh, Navpreet

    2015-11-15

    This paper presents a scheme for second harmonic generation of an intense q-Gaussian laser beam in a preformed parabolic plasma channel, where collisional nonlinearity is operative with nonlinear absorption. Due to nonuniform irradiance of intensity along the wavefront of the laser beam, nonuniform Ohmic heating of plasma electrons takes place. Due to this nonuniform heating of plasma, the laser beam gets self-focused and produces strong density gradients in the transverse direction. The generated density gradients excite an electron plasma wave at pump frequency that interacts with the pump beam to produce its second harmonics. The formulation is based on a numerical solution of the nonlinear Schrodinger wave equation in WKB approximation followed by moment theory approach. A second order nonlinear differential equation governing the propagation dynamics of the laser beam with distance of propagation has been obtained and is solved numerically by Runge Kutta fourth order technique. The effect of nonlinear absorption on self-focusing of the laser beam and conversion efficiency of its second harmonics has been investigated.

  10. Nonlinear optical response induced by a second-harmonic electric-field component concomitant with optical near-field excitation

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Maiku; Nobusada, Katsuyuki; Yatsui, Takashi

    2015-10-01

    Electron dynamics excited by an optical near field (ONF) in a two-dimensional quantum dot model was investigated by solving a time-dependent Schrödinger equation. It was found that the ONF excitation of the electron caused two characteristic phenomena: a two-photon absorption and an induction of a magnetic dipole moment with a strong third-harmonic component. By analyzing the interaction dynamics of the ONF and the electron, we explained that the physical mechanism underlying these phenomena was the second-harmonic electric-field component concomitant with the near-field excitation originating from the nonuniformity of the ONF. Despite a y -polarized ONF source, the second-harmonic component of an x -polarized electric field was inherently generated. The effect of the second-harmonic electric-field component is not due to usual second-order nonlinear response but appears only when we explicitly consider the electron dynamics interacting with the ONF beyond the conventional optical response assuming the dipole approximation.

  11. Energy exchange between orthogonally polarized waves by cascaded quasi-phase-matched processes

    NASA Astrophysics Data System (ADS)

    Johnston, B. F.; Dekker, P.; Saltiel, S. M.; Withford, M. J.; Kivshar, Y. S.

    2008-01-01

    By identifying appropriate quasi-phase-matching (QPM) conditions in z-cut congruent lithium niobate, we demonstrate simultaneous QPM of type-I (ooe) and higher order type-0 (eee) second-harmonic-generation, which share a common second harmonic wave. We demonstrate this experimentally at 1064nm, and show that cascading between these processes occurs. The cascading can result in energy exchange between the cross-polarized fundamentals, indicative of an equivalent 3rd order process. The nonlinear phase shifts and transfer functions resulting from this cascading are explored numerically.

  12. The study of radiation-induced damage and remodeling of extracellular matrix of rectum and bladder by second-harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Kochueva, Marina V.; Sergeeva, Ekaterina A.; Ignatjeva, Natalya Yu.; Zakharkina, Olga L.; Kuznetzov, Sergej S.; Kiseleva, Elena B.; Babak, Ksenia V.; Kamensky, Vladislav A.; Maslennikova, Anna V.

    2014-02-01

    Adverse events in normal tissues after irradiation of malignant tumors are of great importance in modern radiation oncology. Second harmonic generation (SHG) microscopy allows observe the structure of collagen fibers and bundles without additional staining. The study objective was evaluation the dose-time dependences of the structural changes occurring in collagen of rat rectum and bladder after gamma-irradiation. Animals were irradiated by a local field at single doses of 10 Gy and 40 Gy. The study of collagen state was carried out in a week and a month after radiation exposure. Paraffin-embedded material was sectioned on the slices 10 mkm thick and SHG-imaging was performed by LSM 510 Meta (Carl Zeiss, Germany). Excitation was implemented with a pulsed (100-fs) titanium-sapphire laser at a wavelength of 800 nm and a pulse repetition frequency of 80 MHz, registration was performed at two wavelengths: 362-415 nm according to collagen fluorescence and 512-576 nm according to myoglobin fluorescence. In a week after irradiation, sings of epithelial damage and edema of submucosal layer, more significant after the dose of 40 Gy were observed on LSM-images. The SHG signal decreased at this time reflecting the processes of collagen degradation independently either in bladder or in rectum. In a month after radiation the increase of size and number of collagen-bearing structures was observed, more essential after irradiation in a dose of 40 Gy. LSM microscopy with SHG allows evaluate changes of normal tissues after ionizing radiation and get information in addition to standard and special histological staining.

  13. An LSPR fiber optic sensor based on in-line micro-holes fabricated by a second harmonic 400nm femtosecond laser

    NASA Astrophysics Data System (ADS)

    Shiraishi, Masahiko; Goya, Kenji; Seki, Atsushi; Watanabe, Kazuhiro

    2016-02-01

    In this study, we have proposed a novel type of localized surface plasmon resonance (LSPR) fiber optic sensor based on in-line/pico-liter micro-holes which can be experimentally fabricated into the fiber waveguide by using a second harmonic 400 nm femtosecond laser. A repetitive pulse train of 1 kHz with a pulse width of 350 fs was irradiated onto a MMGI fiber optic to make three holes that penetrate through the fiber core and work as spectroscopic-microfluidic flow cells. In order to induce the interaction between transmitted light and gold nanoparticles (GNPs) adhered on the inner surface of the flow cells, micro-holes were designed to be the width of approximately 50 μm, along a direction perpendicular to an optical axis of an optical fiber. GNPs with approximately 100 nm of particle diameter adhered onto the inner surface according to 3-aminopropyltriethoxy silane treatment. The transmitted light through the micro-holes was obtained by optical instruments consisted of a white light source and an optical spectrum analyzer. In order to obtain the reference spectrum, the optical spectrum was acquired before dipping the sensor into the GNPs solution. After 30 min of immersing the sensor portion into the GNPs solution, the optical spectrum was also obtained. The reference spectrum which was considered as the baseline, was set to zero and then, the absorbance spectrum was calculated. The absorbance peak at a wavelength of 537 nm occurred in an air condition in the sensing area, which seemed like the resonance peak based on the LSPR.

  14. Monitoring fibrous scaffold guidance of three-dimensional collagen organisation using minimally-invasive second harmonic generation.

    PubMed

    Delaine-Smith, Robin M; Green, Nicola H; Matcher, Stephen J; MacNeil, Sheila; Reilly, Gwendolen C

    2014-01-01

    The biological and mechanical function of connective tissues is largely determined by controlled cellular alignment and therefore it seems appropriate that tissue-engineered constructs should be architecturally similar to the in vivo tissue targeted for repair or replacement. Collagen organisation dictates the tensile properties of most tissues and so monitoring the deposition of cell-secreted collagen as the construct develops is essential for understanding tissue formation. In this study, electrospun fibres with a random or high degree of orientation, mimicking two types of tissue architecture found in the body, were used to culture human fibroblasts for controlling cell alignment. The minimally-invasive technique of second harmonic generation was used with the aim of monitoring and profiling the deposition and organisation of collagen at different construct depths over time while construct mechanical properties were also determined over the culture period. It was seen that scaffold fibre organisation affected cell migration and orientation up to 21 days which in turn had an effect on collagen organisation. Collagen in random fibrous constructs was deposited in alternating configurations at different depths however a high degree of organisation was observed throughout aligned fibrous constructs orientated in the scaffold fibre direction. Three-dimensional second harmonic generation images showed that deposited collagen was more uniformly distributed in random constructs but aligned constructs were more organised and had higher intensities. The tensile properties of all constructs increased with increasing collagen deposition and were ultimately dictated by collagen organisation. This study highlights the importance of scaffold architecture for controlling the development of well-organised tissue engineered constructs and the usefulness of second harmonic generation imaging for monitoring collagen maturation in a minimally invasive manner.

  15. Evaluation of Therapeutic Tissue Crosslinking (TXL) for Myopia Using Second Harmonic Generation Signal Microscopy in Rabbit Sclera

    PubMed Central

    Zyablitskaya, Mariya; Takaoka, Anna; Munteanu, Emilia L.; Nagasaki, Takayuki; Trokel, Stephen L.; Paik, David C.

    2017-01-01

    Purpose Second harmonic generation signals (SHG) are emitted preferentially from collagenous tissue structures and have been used to evaluate photochemically-induced (CXL) crosslinking changes in the cornea. Since therapeutic tissue crosslinking (TXL) using sodium hydroxymethylglycinate (SMG) of the sclera is a potential treatment for high myopia, we explored the use of SHG microscopy to evaluate the effects. Methods Single sub-Tenon's (sT) injections (400 μL) using SMG (40–400 mM) were made at the equatorial 12 o'clock position of the right eye of cadaveric rabbit heads (n = 16 pairs). After 3.5 hours, confocal microscopy (CM) was performed using 860 nm two-photon excitation and 400 to 450 nm emission. Pixel density and fiber bundle “waviness” analyses were performed on the images. Crosslinking effects were confirmed using thermal denaturation (Tm) temperature. Comparison experiments with riboflavin photochemical crosslinking were done. Results Therapeutic tissue crosslinking localization studies indicated that crosslinking changes occurred at the site of injection and in adjacent sectors. Second harmonic generation signals revealed large fibrous collagenous bundled structures that displayed various degrees of waviness. Histogram analysis showed a nearly 6-fold signal increase in 400 mM SMG over 40 mM. This corresponded to a ΔTm = 13°C for 400 mM versus ΔTm = 4°C for 40 mM. Waviness analysis indicated increased fiber straightening as a result of SMG CXL. Conclusions Second harmonic generation signal intensity and fiber bundle waviness is altered by scleral tissue crosslinking using SMG. These changes provide insights into the macromolecular changes that are induced by therapeutic crosslinking technology and may provide a method to evaluate connective tissue protein changes induced by scleral crosslinking therapies. PMID:28055099

  16. Monitoring Fibrous Scaffold Guidance of Three-Dimensional Collagen Organisation Using Minimally-Invasive Second Harmonic Generation

    PubMed Central

    Delaine-Smith, Robin M.; Green, Nicola H.; Matcher, Stephen J.; MacNeil, Sheila; Reilly, Gwendolen C.

    2014-01-01

    The biological and mechanical function of connective tissues is largely determined by controlled cellular alignment and therefore it seems appropriate that tissue-engineered constructs should be architecturally similar to the in vivo tissue targeted for repair or replacement. Collagen organisation dictates the tensile properties of most tissues and so monitoring the deposition of cell-secreted collagen as the construct develops is essential for understanding tissue formation. In this study, electrospun fibres with a random or high degree of orientation, mimicking two types of tissue architecture found in the body, were used to culture human fibroblasts for controlling cell alignment. The minimally-invasive technique of second harmonic generation was used with the aim of monitoring and profiling the deposition and organisation of collagen at different construct depths over time while construct mechanical properties were also determined over the culture period. It was seen that scaffold fibre organisation affected cell migration and orientation up to 21 days which in turn had an effect on collagen organisation. Collagen in random fibrous constructs was deposited in alternating configurations at different depths however a high degree of organisation was observed throughout aligned fibrous constructs orientated in the scaffold fibre direction. Three-dimensional second harmonic generation images showed that deposited collagen was more uniformly distributed in random constructs but aligned constructs were more organised and had higher intensities. The tensile properties of all constructs increased with increasing collagen deposition and were ultimately dictated by collagen organisation. This study highlights the importance of scaffold architecture for controlling the development of well-organised tissue engineered constructs and the usefulness of second harmonic generation imaging for monitoring collagen maturation in a minimally invasive manner. PMID:24587017

  17. Label-free and real-time imaging of dehydration-induced DNA conformational changes in cellular nucleus using second harmonic microscopy

    NASA Astrophysics Data System (ADS)

    Zhuo, Shuangmu; Ni, Ming

    2014-12-01

    Dehydration-induced DNA conformational changes have been probed for the first time with the use of second harmonic microscopy. Unlike conventional approaches, second harmonic microscopy provides a label-free and real-time approach to detect DNA conformational changes. Upon dehydration, cellular DNA undergoes a transition from B- to A-form, whereas cellular nuclei change from invisible to visible under second harmonic microscopy. These results showed that DNA is a second order nonlinear optical material. We further confirmed this by characterizing the nonlinear optical properties of extracted DNA from human cells. Our findings open a new path for SHG imaging. DNA can change its conformations under many circumstances. For example: normal cells turning into cancerous cells and drug molecules binding with DNA. Therefore, the detection of DNA conformational changes with second harmonic microscopy will be a useful tool in cancer therapy and new drug discovery.

  18. Absorption, fluorescence and second harmonic generation in Cr³⁺-doped BiB₃O₆ glasses.

    PubMed

    Kuznik, W; Fuks-Janczarek, I; Wojciechowski, A; Kityk, I V; Kiisk, V; Majchrowski, A; Jaroszewicz, L R; Brik, M G; Nagy, G U L

    2015-06-15

    Synthesis, spectral properties and photoinduced nonlinear optical effects of chromium-doped BiB3O6 glass are studied in the present paper. Absorption, excitation and time resolved luminescence spectra are presented and luminescence decay behavior is discussed. Detailed analysis of the obtained spectra (assignment of the most prominent spectral features in terms of the corresponding Cr(3+) energy levels, crystal field strength Dq, Racah parameters B and C) was performed. A weak photostimulated second harmonic generation signal was found to increase drastically due to poling by proton implantation in the investigated sample.

  19. Correlation of Ge E' defect sites with second-harmonic generation in poled high-water fused silica

    NASA Astrophysics Data System (ADS)

    Henry, Leanne J.

    1995-08-01

    Second-harmonic generation (SHG) in poled high-water fused silica was found to be linearly dependent on the relative concentration of Ge E \\prime defect sites ( <10-15 defect sites/cm 3 ) for the highly pure UV-grade material. For commercial-grade material characterized by higher concentrations of Ge E\\prime defects sites, the SHG appeared to saturate at approximately 0.5 pm/V . No dependence of the SHG was found on the relative concentration of Ge E\\prime defects sites in poled commercial-grade low-water fused silica.

  20. Direct observation of bulk second-harmonic generation inside a glass slide with tightly focused optical fields

    NASA Astrophysics Data System (ADS)

    Wang, Xianghui; Fardad, Shima; Das, Susobhan; Salandrino, Alessandro; Hui, Rongqing

    2016-04-01

    Bulk second-harmonic generation (SHG) inside glass slides is directly detected unambiguously without interference from surface contributions. This is enabled by tightly focused and highly localized ultrashort laser pulses. The theoretical calculations based on vector diffraction theory and the phenomenological model of SHG inside centrosymmetric materials agree well with the measured far-field SHG radiation patterns for different polarization states of the fundamental beam. The results indicate that the observed bulk SHG is predominantly related to the bulk parameter δ' and originates from the three-dimensional field gradient in the focal region.

  1. Decrimping: The first stage of collagen thermal denaturation unraveled by in situ second-harmonic-generation imaging

    NASA Astrophysics Data System (ADS)

    Liao, Chien-Sheng; Zhuo, Zong-Yan; Yu, Jiun-Yann; Tzeng, Yu-Yi; Chu, Shi-Wei; Yu, Shih-Fan; Chao, Pen-Hsiu Grace

    2011-04-01

    With polarized and time-lapsed second-harmonic-generation (SHG) imaging, three distinct thermodynamic stages are revealed during heating of collagenous tissue. In the first "decrimping" stage, SHG intensity remains unchanged while the characteristic crimp pattern of collagen fiber disappears. The intactness of underlying fibrils is confirmed by unaffected second-order susceptibility, suggesting decrimping is related to the breakage of cross-linking between collagen fibrils. In the latter stages, significant SHG decrease is observed, providing quantification to collagen thermal denaturation. This study manifests the benefits of adopting SHG for understanding the thermal response of collagen, and will be useful toward better thermal therapy design.

  2. Pulse-modulated second harmonic imaging microscope quantitatively demonstrates marked increase of collagen in tumor after chemotherapy

    NASA Astrophysics Data System (ADS)

    Raja, Anju M.; Xu, Shuoyu; Sun, Wanxin; Zhou, Jianbiao; Tai, Dean C. S.; Chen, Chien-Shing; Rajapakse, Jagath C.; So, Peter T. C.; Yu, Hanry

    2010-09-01

    Pulse-modulated second harmonic imaging microscopes (PM-SHIMs) exhibit improved signal-to-noise ratio (SNR) over conventional SHIMs on sensitive imaging and quantification of weak collagen signals inside tissues. We quantify the spatial distribution of sparse collagen inside a xenograft model of human acute myeloid leukemia (AML) tumor specimens treated with a new drug against receptor tyrosine kinase (ABT-869), and observe a significant increase in collagen area percentage, collagen fiber length, fiber width, and fiber number after chemotherapy. This finding reveals new insights into tumor responses to chemotherapy and suggests caution in developing new drugs and therapeutic regimens against cancers.

  3. Addressable, large-field second harmonic generation microscopy based on 2D acousto-optical deflector and spatial light modulator.

    PubMed

    Shao, Yonghong; Liu, Honghai; Qin, Wan; Qu, Junle; Peng, Xiang; Niu, Hanben; Gao, Bruce Z

    2012-09-01

    We present an addressable, large-field second harmonic generation microscope by combining a 2D acousto-optical deflector with a spatial light modulator. The SLM shapes an incoming mode-locked, near-infrared Ti:Sapphire laser beam into a multifocus array, which can be rapidly scanned by changing the incident angle of the laser beam using a 2D acousto-optical deflector. Compared to the single-beam-scan technique, the multifocus array scan can increase the scanning rate and the field-of-view size with the multi-region imaging ability.

  4. Addressable, large-field second harmonic generation microscopy based on 2D acousto-optical deflector and spatial light modulator

    PubMed Central

    Shao, Yonghong; Liu, Honghai; Qin, Wan; Qu, Junle; Peng, Xiang; Niu, Hanben

    2013-01-01

    We present an addressable, large-field second harmonic generation microscope by combining a 2D acousto-optical deflector with a spatial light modulator. The SLM shapes an incoming mode-locked, near-infrared Ti:Sapphire laser beam into a multifocus array, which can be rapidly scanned by changing the incident angle of the laser beam using a 2D acousto-optical deflector. Compared to the single-beam-scan technique, the multifocus array scan can increase the scanning rate and the field-of-view size with the multi-region imaging ability. PMID:24307756

  5. In vivo imaging of dermal collagen in skin burn by collagen-sensitive second-harmonic-generation microscopy

    NASA Astrophysics Data System (ADS)

    Yasui, Takeshi; Tanaka, Ryosuke; Hase, Eiji; Fukushima, Shu-ichiro; Araki, Tsutomu

    2013-02-01

    Optical assessment of skin burns is possible with second-harmonic-generation (SHG) microscopy due to its high sensitivity to thermal denaturation of collagen molecules. In contrast to previous studies that were performed using excised tissue specimens ex vivo, in this study, we demonstrated in vivo observation of dermal collagen fibers in living rat burn models with SHG microscopy. We confirmed that changes in SHG vanishing patterns in the SHG images depended on the burn degree. The results imply that SHG microscopy can be used as a low-invasiveness, highly quantitative tool for skin burn assessment.

  6. Tunable visible solid-state lasers based on second-harmonic generation of LiF:F(2) in potassium titanyl phosphate.

    PubMed

    Giffin, S M; McKinnie, I T; Ter-Mikirtychev, V V

    1998-02-01

    A new broadly tunable visible solid-state laser is reported. Wavelengths between 550 and 610 nm are generated by intracavity frequency doubling of tuned and free-running room-temperature pulsed LiF:F(2)(-) lasers in potassium titanyl phosphate. Second-harmonic energy of 1.3 mJ has been achieved, corresponding to a fundamental-to-second-harmonic conversion efficiency of 20%. Operation is optimized with respect to LiF:F(2)(-) laser parameters.

  7. Polarization-Independent Multiple Fano Resonances in Plasmonic Nonamers for Multimode-Matching Enhanced Multiband Second-Harmonic Generation.

    PubMed

    Liu, Shao-Ding; Leong, Eunice Sok Ping; Li, Guang-Can; Hou, Yidong; Deng, Jie; Teng, Jing Hua; Ong, Hock Chun; Lei, Dang Yuan

    2016-01-26

    Plasmonic oligomers composed of metallic nanoparticles are one class of the most promising platforms for generating Fano resonances with unprecedented optical properties for enhancing various linear and nonlinear optical processes. For efficient generation of second-harmonic emissions at multiple wavelength bands, it is critical to design a plasmonic oligomer concurrently having multiple Fano resonances spectrally matching the fundamental excitation wavelengths and multiple plasmon resonance modes coinciding with the harmonic wavelengths. Thus far, the realization of such a plasmonic oligomer remains a challenge. This study demonstrates both theoretically and experimentally that a plasmonic nonamer consisting of a gold nanocross surrounded by eight nanorods simultaneously sustains multiple polarization-independent Fano resonances in the near-infrared region and several higher-order plasmon resonances in the visible spectrum. Due to coherent amplification of the nonlinear excitation sources by the Fano resonances and efficient scattering-enhanced outcoupling by the higher-order modes, the second-harmonic emission of the nonamer is significantly increased at multiple spectral bands, and their spectral positions and radiation patterns can be flexibly manipulated by easily tuning the length of the surrounding nanorods in the nonamer. These results provide us with important implications for realizing ultrafast multichannel nonlinear optoelectronic devices.

  8. Direct optical detection of current induced spin accumulation in metals by magnetization-induced second harmonic generation

    SciTech Connect

    Pattabi, A. Gu, Z.; Yang, Y.; Finley, J.; Lee, O. J.; Raziq, H. A.; Gorchon, J.; Salahuddin, S.; Bokor, J.

    2015-10-12

    Strong spin-orbit coupling in non-magnetic heavy metals has been shown to lead to large spin currents flowing transverse to a charge current in such a metal wire. This in turn leads to the buildup of a net spin accumulation at the lateral surfaces of the wire. Spin-orbit torque effects enable the use of the accumulated spins to exert useful magnetic torques on adjacent magnetic layers in spintronic devices. We report the direct detection of spin accumulation at the free surface of nonmagnetic metal films using magnetization-induced optical surface second harmonic generation. The technique is applied to probe the current induced surface spin accumulation in various heavy metals such as Pt, β-Ta, and Au with high sensitivity. The sensitivity of the technique enables us to measure the time dynamics on a sub-ns time scale of the spin accumulation arising from a short current pulse. The ability of optical surface second harmonic generation to probe interfaces suggests that this technique will also be useful for studying the dynamics of spin accumulation and transport across interfaces between non-magnetic and ferromagnetic materials, where spin-orbit torque effects are of considerable interest.

  9. Diode-Pumped Nd:KGd(WO4)2 Laser: Lasing at Fundamental and Second Harmonic Frequencies

    NASA Astrophysics Data System (ADS)

    Bui, A. A.; Dashkevich, U. I.; Orlovich, V. A.; Khodasevich, I. A.

    2015-09-01

    High-power cw and quasi-cw lasing at the fundamental and second harmonic frequencies is obtained from Nd:KGd(WO 4 ) 2 lasers based on Np- and Ng-cut crystals pumped longitudinally by a diode laser at 879 nm. Because of different crystal lengths, the limiting pump power beyond which the crystals undergo thermomechanical damage is 26.8 W for the N p -cut and 17.3 W for the N g -cut. At these pump powers the cw outputs at λ = 1067.2 nm are 9.4 and 5.4 W, respectively, and the N g -cut crystal output is TEM 00 at the fundamental frequency. With quasicontinuous pumping at a 10% duty cycle the instantaneous laser power reaches ~11 W for both cuts with a periodic duration of 10-20 ms. The differential lasing efficiency relative to the absorbed pump power is 66.4% for cw lasing and 77.4% for quasi-cw operation. With intracavity frequency doubling using a KTP crystal, better results were obtained with the N g -cut crystal because of its simpler thermal lensing. The maximum second harmonic power was ~1.1 W for cw operation and ~2.6 W for quasi-cw operation with a diode laser power of 27.3 W.

  10. Linear and nonlinear Biot waves in a noncohesive granular medium slab: transfer function, self-action, second harmonic generation.

    PubMed

    Legland, J-B; Tournat, V; Dazel, O; Novak, A; Gusev, V

    2012-06-01

    Experimental results are reported on second harmonic generation and self-action in a noncohesive granular medium supporting wave energy propagation both in the solid frame and in the saturating fluid. The acoustic transfer function of the probed granular slab can be separated into two main frequency regions: a low frequency region where the wave propagation is controlled by the solid skeleton elastic properties, and a higher frequency region where the behavior is dominantly due to the air saturating the beads. Experimental results agree well with a recently developed nonlinear Biot wave model applied to granular media. The linear transfer function, second harmonic generation, and self-action effect are studied as a function of bead diameter, compaction step, excitation amplitude, and frequency. This parametric study allows one to isolate different propagation regimes involving a range of described and interpreted linear and nonlinear processes that are encountered in granular media experiments. In particular, a theoretical interpretation is proposed for the observed strong self-action effect.

  11. Cumulative second-harmonic analysis of ultrasonic Lamb waves for ageing behavior study of modified-HP austenite steel.

    PubMed

    Xiang, Yanxun; Deng, Mingxi; Xuan, Fu-Zhen; Liu, Chang-Jun

    2011-12-01

    The cumulative second-harmonic analysis of ultrasonic Lamb wave has been performed to study the precipitation kinetics and microvoid initiation of ferritic Cr-Ni alloy steel during the ageing process. Ageing of ferritic Cr-Ni alloy materials have been done at 1223 K and 1173 K for different degradation time intervals and air cooled. The results show that the normalized acoustic nonlinearity of Lamb wave increases with the formation of fine precipitates at the early stage of ageing till about 1000 h and keeps as a plateau with the precipitates dynamic balance for a long-term ageing, and then decreases gradually at the final holding time with the coarsening of precipitates and initiation of microvoids. The results also show that the variation of nonlinear Lamb wave follows the same trend as that of hardness in materials. Therefore, the cumulative second-harmonic of ultrasonic Lamb waves has been found to be strongly sensitive to the precipitates behavior and microstructure evolution during the thermal ageing of ferritic Cr-Ni alloy steel.

  12. Spontaneous Polarization in Bio-organic Materials Studied by Scanning Pyroelectric Microscopy (SPEM) and Second Harmonic Generation Microscopy (SHGM)

    NASA Astrophysics Data System (ADS)

    Putzeys, T.; Wübbenhorst, M.; van der Veen, M. A.

    2015-06-01

    Bio-organic materials such as bones, teeth, and tendon generally show nonlinear optical (Masters and So in Handbook of Biomedical Nonlinear Optical Microscopy, 2008), pyro- and piezoelectric (Fukada and Yasuda in J Phys Soc Jpn 12:1158, 1957) properties, implying a permanent polarization, the presence of which can be rationalized by describing the growth of the sample and the creation of a polar axis according to Markov's theory of stochastic processes (Hulliger in Biophys J 84:3501, 2003; Batagiannis et al. in Curr Opin Solid State Mater Sci 17:107, 2010). Two proven, versatile techniques for probing spontaneous polarization distributions in solids are scanning pyroelectric microscopy (SPEM) and second harmonic generation microscopy (SHGM). The combination of pyroelectric scanning with SHG-microscopy in a single experimental setup leading to complementary pyroelectric and nonlinear optical data is demonstrated, providing us with a more complete image of the polarization in organic materials. Crystals consisting of a known polar and hyperpolarizable material, CNS (4-chloro-4-nitrostilbene) are used as a reference sample, to verify the functionality of the setup, with both SPEM and SHGM images revealing the same polarization domain information. In contrast, feline and human nails exhibit a pyroelectric response, but a second harmonic response is absent for both keratin containing materials, implying that there may be symmetry-allowed SHG, but with very inefficient second harmonophores. This new approach to polarity detection provides additional information on the polar and hyperpolar nature in a variety of (bio) materials.

  13. Laue diffraction in one-dimensional photonic crystals: The way for phase-matched second-harmonic generation

    NASA Astrophysics Data System (ADS)

    Novikov, V. B.; Maydykovskiy, A. I.; Mantsyzov, B. I.; Murzina, T. V.

    2016-06-01

    Phase-matched second-harmonic generation (SHG) under the Bragg diffraction in the Laue geometry in one-dimensional photonic crystal (PhC) is studied theoretically and experimentally. We demonstrate that the phase-matched SHG can be realized in a PhC by compensation of the material dispersion of the PhC constituent layers of adjustable thickness. The second-order nonlinear susceptibility is introduced in the porous quartz-based PhC by its infiltration by sodium nitrite. We observed that two second-harmonic (SH) beams appear after passing through the PhC under the phase-matched process, which correspond to the transmission and diffraction angular directions. The appearance of the phase-matched SHG is confirmed by a pronounced SH spectral dependence and a narrow SH angular distribution, with the FWHM of the SH peak of approximately 3.5 times smaller as compared to the case of non-phase-matched SHG.

  14. Enhanced second-harmonic generation from metal-integrated semiconductor nanowires via highly confined whispering gallery modes.

    PubMed

    Ren, Ming-Liang; Liu, Wenjing; Aspetti, Carlos O; Sun, Liaoxin; Agarwal, Ritesh

    2014-11-12

    Coherent and tunable nanoscale light sources utilizing optical nonlinearities are required for applications ranging from imaging and bio-sensing to on-chip all-optical signal processing. However, owing to their small sizes, the efficiency of nanostructures even with high nonlinear coefficients is poor, therefore requiring very high excitation energies. Although surface-plasmon resonances of metal nanostructures can enhance surface nonlinear processes such as second-harmonic generation, they still suffer from low conversion efficiencies owing to their intrinsically low nonlinear coefficients. Here we show highly enhanced and directional second-harmonic generation from individual CdS nanowires integrated with silver nanocavities (>1,000 times higher external efficiency compared with bare CdS), in which the lowest-order whispering gallery mode is engineered to concentrate light in the nonlinear material while minimizing Ohmic losses. The directional nonlinear signal is redirected into another waveguide, which is then utilized to configure an optical router that can potentially serve as a tunable coherent light source to enable on-chip signal processing for integrated nanophotonic systems.

  15. First-order thermal correction to the quadratic response tensor and rate for second harmonic plasma emission

    SciTech Connect

    Layden, B.; Cairns, Iver H.; Robinson, P. A.; Percival, D. J.

    2011-02-15

    Three-wave interactions in plasmas are described, in the framework of kinetic theory, by the quadratic response tensor (QRT). The cold-plasma QRT is a common approximation for interactions between three fast waves. Here, the first-order thermal correction (FOTC) to the cold-plasma QRT is derived for interactions between three fast waves in a warm unmagnetized collisionless plasma, whose particles have an arbitrary isotropic distribution function. The FOTC to the cold-plasma QRT is shown to depend on the second moment of the distribution function, the phase speeds of the waves, and the interaction geometry. Previous calculations of the rate for second harmonic plasma emission (via Langmuir-wave coalescence) assume the cold-plasma QRT. The FOTC to the cold-plasma QRT is used here to calculate the FOTC to the second harmonic emission rate, and its importance is assessed in various physical situations. The FOTC significantly increases the rate when the ratio of the Langmuir phase speed to the electron thermal speed is less than about 3.

  16. Large scale synthesis, second-harmonic generation, and piezoelectric properties of a noncentrosymmetric vanadium phosphate, Li2VPO6

    NASA Astrophysics Data System (ADS)

    Lee, Eun Pyo; Lee, Dong Woo; Cho, Yoon-Ho; Thao Tran, T.; Shiv Halasyamani, P.; Ok, Kang Min

    2013-06-01

    The phase pure large scale synthesis, second-harmonic generation, and piezoelectric properties of a vanadium phosphate, Li2VPO6 are reported. The material has been synthesized by a standard solid-state reaction using Li2CO3, V2O5, and NH4H2PO4 as reagents. The phase purity and crystal structure of the reported material have been confirmed by powder X-ray and neutron diffractions. The material crystallizes in orthorhombic space group Pna21 (no. 33) with a=10.32581(7) Å, b=4.63728(3) Å, c=8.56606(5) Å, and Z=4. The noncentrosymmetric layered structure is composed of distorted VO6 octahedra and PO4 tetrahedra. The V5+ cations distort either along the approximate [1 0 1] or [-1 0 1] directions attributable to the alignment of distorted VO6 octahedra, resulting in a polar structure. Powder second-harmonic generating (SHG) measurements on Li2VPO6 using 1064 nm radiation, indicate the material has a SHG efficiency of approximately 10 times that of α-SiO2 and is not phase-matchable (type 1). Converse piezoelectric measurements for the material reveal a piezoelectric coefficient, d33, of 12 pm V-1.

  17. Using Second Harmonic Generation Microscopy to Study the Three-Dimensional Structure of Collagen and its Degradation Mechanism

    NASA Astrophysics Data System (ADS)

    Mega, Yair

    Collagen is one of the most abundant proteins found in the human body. Its crystalline structure possesses no centrosymmetry, allowing it to emit second-harmonic waves. Second harmonic generation (SHG) microscopy utilizes the latter quality to produce high-resolution images of collagen rich tissues and therefore become a key research tool in the biomedical field. We developed a new model, intended to be used together with second harmonic generation (SHG) microscopy, to thoroughly investigate collagen-based tissues. We use our SHG model to reveal information in real time from enzymatic biochemical processes. We also present a novel method used to measure quantitatively the direction of the fibers within the tissue, from SHG images. Using this method, we were able to reconstruct an angular map of the orientation of collagen fibers from multiple sections across the entire area of a human cornea. The structure we obtained demonstrates the criss-crossing structure of the human cornea, previously suggested in the literature. In addition, we also report work on a unique step-wise three-photon fluorescence excitation discovered in melanin. This unique fluorescence mechanism was exploited to discriminate melanin on a small-size, low-cost and low laser power setup which was used as a prototype for a handheld device. The latter study is a part of a larger on-going effort in our group to explore new diagnosis methods to be used for early skin cancer screening. Finally, this work demonstrates a spectroscopy-based method to correct for blood vessel thickness effect. The method analyzes spectral shift from a molecular imaging agent and correlate the shifts to the length of the optical path in blood. The correction method described in this work is intended to be implemented on a guided catheter near infrared fluorescence (NIRF) intra-vascular imaging system. In this imaging system, this study's results will used to correct for the radial distance between the imaging tip of the

  18. Enhancement of second harmonic generation signal in thermally poled glass ceramic with NaNbO{sub 3} nanocrystals

    SciTech Connect

    Malakho, Artem; Fargin, Evelyne; Lahaye, Michel; Lazoryak, Bogdan; Morozov, Vladimir; Van Tendeloo, Gustaaf; Rodriguez, Vincent; Adamietz, Frederic

    2006-09-15

    Glass ceramic composites were prepared by bulk crystallization of NaNbO{sub 3} in sodium niobium borate glasses. A homogeneous bulk crystallization of the NaNbO{sub 3} phase takes place during heat treatments that produces visible-near infrared transparent materials with {approx}30 nm NaNbO{sub 3} nanocrystallites. Upon thermal poling, a strong Na{sup +} depleted nonlinear optical thin layer is observed at the anode side that should induce a large internal static electric field. In addition, the {chi}{sup (2)} response of the poled glass ceramic composites increases from 0.2 up to 1.9 pm/V with the rate of crystallization. Two mechanisms may be considered: a pure structural {chi}{sup (2)} process connected with the occurrence of a spontaneous ferroelectric polarization or an increase of the {chi}{sup (3)} response of the nanocrystallites that enhances the electric field induced second harmonic generation process.

  19. Pb2 BO3 Cl: A Tailor-Made Polar Lead Borate Chloride with Very Strong Second Harmonic Generation.

    PubMed

    Zou, Guohong; Lin, Chensheng; Jo, Hongil; Nam, Gnu; You, Tae-Soo; Ok, Kang Min

    2016-09-19

    A meticulously designed, polar, non-centrosymmetric lead borate chloride, Pb2 BO3 Cl, was synthesized using KBe2 BO3 F2 (KBBF) as a model. Single-crystal X-ray diffraction revealed that the structure of Pb2 BO3 Cl consists of cationic [Pb2 (BO3 )](+) honeycomb layers and Cl(-) anions. Powder second harmonic generation (SHG) measurements on graded polycrystalline Pb2 BO3 Cl indicated that the title compound is phase-matchable (type I) and exhibits a remarkably strong SHG response, which is approximately nine times stronger than that of potassium dihydrogen phosphate, and the largest efficiency observed in materials with structures similar to KBBF. Further characterization suggested that the compound melts congruently at high temperature and has a wide transparency window from the near-UV to the mid-IR region.

  20. Minimally invasive imaging method based on second harmonic generation and multiphoton excitation fluorescence in translational respiratory research.

    PubMed

    Abraham, Thomas; Wadsworth, Samuel; Carthy, Jon M; Pechkovsky, Dmitri V; McManus, Bruce

    2011-01-01

    For translational respiratory research including in the development of clinical diagnostic tools, a minimally invasive imaging method, which can provide both cellular and extracellular structural details with sufficient specificity, sensitivity and spatial resolution, is particularly useful. Multiphoton microscopy causes excitation of endogenously fluorescent macromolecular systems and induces highly specific second harmonic generation signals from non-centrosymmetric macromolecules such as fibrillar collagens. Both these signals can be captured simultaneously to provide spatially resolved 3D structural organization of extracellular matrix as well as the cellular morphologies in their native states. Besides briefly discussing the fundamentals of multiphoton excitation fluorescence and harmonic generation signals and the instrumentation details, this review focuses on the specific applications of these imaging modalities in lung structural imaging, particularly morphological features of alveolar structures, visualizing and quantifying extracellular matrix remodelling accompanying emphysematous destructions as well as the IPF, detecting lung cancers and the potential use in the tissue engineering applications.