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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 microscopy of axonemes.

    PubMed

    Odin, Christophe; Heichette, Claire; Chretien, Denis; Le Grand, Yann

    2009-05-25

    We performed Second Harmonic Microscopy of axonemes obtained from sea urchin sperm. Using polarization analysis and a trade-off between signal and photodamage, we were able to determine, for the first time to our knowledge, the nonlinear susceptibility chizxx/chixzx = 1.1+/-0.2 and chizzz/chixzx = 4+/-0.5 of axonemes.

  11. 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.

  12. 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.

  13. 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.

  14. Second harmonic generation in human ovarian neoplasias

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

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

  15. 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.

  16. 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 %.

  17. 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

  18. 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.

  19. Prediction of Metastasis Using Second Harmonic Generation

    DTIC Science & Technology

    2016-07-01

    photon focal volume and the thin tissue section), producing a single F and B image for each sample. Then an arbitrary threshold was chosen by a blinded...AWARD NUMBER: W81XWH-15-1-0040 TITLE: Prediction of Metastasis Using Second Harmonic Generation PRINCIPAL INVESTIGATOR: Edward Brown...ABOVE ADDRESS. 1. REPORT DATE July 2016 2. REPORT TYPE Final 3. DATES COVERED 1May2015 - 30Apr2016 Prediction of Metastasis Using Second Harmonic

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

    SciTech Connect

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

    2015-05-01

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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

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

    SciTech Connect

    Emel'yanov, Vladimir I

    2011-02-28

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

  13. Generating Second Harmonics In Nonlinear Resonant Cavities

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  14. 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.

  15. 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.

  16. Second-harmonic superprism effect in photonic crystals.

    PubMed

    Centeno, Emmanuel

    2005-05-01

    By exploitation of the nonlinear optical properties of two-dimensional photonic crystals, a second-harmonic superprism effect is demonstrated. The anisotropy of the dispersion curves allows control of the propagation direction of the second-harmonic field. Smooth variations of the fundamental wavelength or the angle of incidence produce a drastic angular shift of the second-harmonic emission.

  17. 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.

  18. 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.

  19. Second-harmonic generation imaging of cancer.

    PubMed

    Keikhosravi, Adib; Bredfeldt, Jeremy S; Sagar, Abdul Kader; Eliceiri, Kevin W

    2014-01-01

    The last 30 years has seen great advances in optical microscopy with the introduction of sophisticated fluorescence-based imaging methods such as confocal and multiphoton laser scanning microscopy. There is increasing interest in using these methods to quantitatively examine sources of intrinsic biological contrast including autofluorescent endogenous proteins and light interactions such as second-harmonic generation (SHG) in collagen. In particular, SHG-based microscopy has become a widely used quantitative modality for imaging noncentrosymmetric proteins such as collagen in a diverse range of tissues. Due to the underlying physical origin of the SHG signal, it is highly sensitive to collagen fibril/fiber structure and, importantly, to collagen-associated changes that occur in diseases such as cancer, fibrosis, and connective tissue disorders. An overview of SHG physics background and technologies is presented with a focused review on applications of SHG primarily as applied to cancer. © 2014 Elsevier Inc. All rights reserved.

  20. 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

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. Second-harmonic generation in noncentrosymmetric phosphates

    NASA Astrophysics Data System (ADS)

    Li, Zhi; Liu, Qiong; Wang, Ying; Iitaka, Toshiaki; Su, Haibin; Tohyama, Takami; Yang, Zhihua; Pan, Shilie

    2017-07-01

    Motivated by the discovery of more and more phosphates with relatively strong nonlinear optic effect, we studied the mechanism of the second-harmonic generation (SHG) effect in several phosphates by band model and first-principles calculations. When the energy of an incident photon is much smaller than the band gap of material, the SHG is almost frequency independent and determined by the combination of Berry connection and a symmetric tensor. The SHG effect in phosphates can be enhanced by the enhancement of orbital hybridization or the reduction of charge-transfer energy, which results in widened bandwidth of occupied state and reduced band gap in the electronic structure, respectively. By the first-principles calculation on the electronic structures of several phosphates—BPO4, LiCs2PO4 , β -Li3VO4 , and β -Li3PO4 —we interpreted the relatively strong SHG effect in LiCs2PO4 and β -Li3VO4 as the consequence of the reduced charge-transfer energy compared to their parent β -Li3PO4 , while the enhanced SHG in BPO4 is resulting from enhanced orbital hybridization.

  8. 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.

  9. 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.

  10. Ultrafast Plasmonic Control of Second Harmonic Generation

    DOE PAGES

    Davidson, Roderick B.; Yanchenko, Anna; Ziegler, Jed I.; ...

    2016-06-01

    Efficient frequency conversion techniques are crucial to the development of plasmonic metasurfaces for information processing and signal modulation. In principle, nanoscale electric-field confinement in nonlinear materials enables higher harmonic conversion efficiencies per unit volume than those attainable in bulk materials. Here we demonstrate efficient second-harmonic generation (SHG) in a serrated nanogap plasmonic geometry that generates steep electric field gradients on a dielectric metasurface. An ultrafast control pulse is used to control plasmon-induced electric fields in a thin-film material with inversion symmetry that, without plasmonic enhancement, does not exhibit an even-order nonlinear optical response. The temporal evolution of the plasmonic near-fieldmore » is characterized with ~100 as resolution using a novel nonlinear interferometric technique. The serrated nanogap is a unique platform in which to investigate optically controlled, plasmonically enhanced harmonic generation in dielectric materials on an ultrafast time scale. Lastly, this metamaterial geometry can also be readily extended to all-optical control of other nonlinear phenomena, such as four-wave mixing and sum- and difference-frequency generation, in a wide variety of dielectric materials.« less

  11. Ultrafast Plasmonic Control of Second Harmonic Generation

    SciTech Connect

    Davidson, Roderick B.; Yanchenko, Anna; Ziegler, Jed I.; Avanesyan, Sergey M.; Lawrie, Benjamin J.; Haglund, Richard F.

    2016-06-01

    Efficient frequency conversion techniques are crucial to the development of plasmonic metasurfaces for information processing and signal modulation. In principle, nanoscale electric-field confinement in nonlinear materials enables higher harmonic conversion efficiencies per unit volume than those attainable in bulk materials. Here we demonstrate efficient second-harmonic generation (SHG) in a serrated nanogap plasmonic geometry that generates steep electric field gradients on a dielectric metasurface. An ultrafast control pulse is used to control plasmon-induced electric fields in a thin-film material with inversion symmetry that, without plasmonic enhancement, does not exhibit an even-order nonlinear optical response. The temporal evolution of the plasmonic near-field is characterized with ~100 as resolution using a novel nonlinear interferometric technique. The serrated nanogap is a unique platform in which to investigate optically controlled, plasmonically enhanced harmonic generation in dielectric materials on an ultrafast time scale. Lastly, this metamaterial geometry can also be readily extended to all-optical control of other nonlinear phenomena, such as four-wave mixing and sum- and difference-frequency generation, in a wide variety of dielectric materials.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 34 GHz second-harmonic peniotron oscillator

    NASA Astrophysics Data System (ADS)

    Dressman, Lawrence Jude

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

  17. Resonance amplification of the second harmonic in an optical fiber

    SciTech Connect

    D`yakonov, M.I.; Furman, A.S.

    1995-11-01

    The case is considered where low-intensity seed radiation at a frequency close to that of the second harmonic is injected into an optical fiber in addition to the pump radiation. The seed signal is predicted to undergo exponential amplification. The gain has a resonance dependence on the frequency shift. It is shown that the nonlinearity associated with a decrease in the relaxation time taking place with increasing second-harmonic intensity leads to the signal saturation and broadening of the resonance profile. The relation of this effect with the well-known phenomenon of photoinduced second-harmonic generation (SHG) in an optical fiber is discussed. 16 refs., 1 fig.

  18. 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.

  19. 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.

  20. 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.

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

    PubMed

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

    1995-06-01

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

  2. 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

  3. Wide-bandgap III-Nitride based Second Harmonic Generation

    DTIC Science & Technology

    2014-10-02

    Jun-2014 Approved for Public Release; Distribution Unlimited Final Report: Wide-bandgap III - Nitride based Second Harmonic Generation The views...Report: Wide-bandgap III - Nitride based Second Harmonic Generation Report Title It was demonstrated that GaN, AlGaN and AlN lateral polar structures can...research have been socialized to the III - Nitride Optoelectronics Center of Excellence (ARL SEDD) and to the 2013 ARO Staff Research Symposium and at

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  12. 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.

  13. Second harmonic generation in thin optical fibers via cladding modes.

    PubMed

    Elzahaby, Eman A; Kandas, Ishac; Aly, Moustafa H

    2016-05-30

    Since silica goes under the category of amorphous materials, it is difficult to investigate important processes such as second harmonic generation (SHG) in silica-based fibers. In this paper, we proposed a method for SHG relaying on cladding modes as pump modes. Cladding modes are introduced in optical fibers through tilted long period grating (T-LPG), where power of core mode is transferred into cladding modes. By functionalizing T-LPG with nonlinear coating, the interaction occurs between cladding modes and the coating material, consequently second harmonic signal (SHS) is generated with efficiency up to 0.14%.

  14. 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.

  15. A microchip laser with intracavity second-harmonic generation

    SciTech Connect

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

    2008-12-31

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

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

    SciTech Connect

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

    2016-08-15

    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.

  18. 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.

  19. 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.

  20. Second-harmonic patterned polarization-analyzed reflection confocal microscope

    NASA Astrophysics Data System (ADS)

    Okoro, Chukwuemeka; Toussaint, Kimani C.

    2017-08-01

    We introduce the second-harmonic patterned polarization-analyzed reflection confocal (SPPARC) microscope-a multimodal imaging platform that integrates Mueller matrix polarimetry with reflection confocal and second-harmonic generation (SHG) microscopy. SPPARC microscopy provides label-free three-dimensional (3-D), SHG-patterned confocal images that lend themselves to spatially dependent, linear polarimetric analysis for extraction of rich polarization information based on the Mueller calculus. To demonstrate its capabilities, we use SPPARC microscopy to analyze both porcine tendon and ligament samples and find differences in both circular degree-of-polarization and depolarization parameters. Moreover, using the collagen-generated SHG signal as an endogenous counterstain, we show that the technique can be used to provide 3-D polarimetric information of the surrounding extrafibrillar matrix plus cells or EFMC region. The unique characteristics of SPPARC microscopy holds strong potential for it to more accurately and quantitatively describe microstructural changes in collagen-rich samples in three spatial dimensions.

  1. 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.

  2. Collagen and myosin characterization by orientation field second harmonic microscopy.

    PubMed

    Odin, Christophe; Guilbert, Thomas; Alkilani, Alia; Boryskina, Olena P; Fleury, Vincent; Le Grand, Yann

    2008-09-29

    Collagen and myosin fibrils are endogenous harmonophores that both give rise to Second Harmonic Generation (SHG). By combining four polarization SHG images provided by a scanning microscope, we show that the orientation of the principal axis of the nonlinear susceptibility tensor chi(2) can be determined for each pixel of the image. The ratio rho = chi33/chi15 of the principal components of chi(2) of collagen and myosin was obtained with the same method, and found within the range 1.6-1.8 and 0.5-0.6 respectively. The orientation of the principal axis of chi(2) is shown to be correlated to the orientation of the fibrils themselves. This provides a straightforward method, which we call Orientation Field-Second Harmonic Microscopy (OF-SHM), to reconstruct orientation fields of fibrils at various scales and resolutions in different biological systems (from muscle sarcomere to the whole embryo).

  3. 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

  4. 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.

  5. 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

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

    PubMed

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

    2011-09-01

    We demonstrate that second-harmonic radiation imaging probes are efficient biomarkers for imaging in living tissue. We show that 100 nm and 300 nm BaTiO(3) 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.

  7. 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.

  8. Second harmonic generation from ZnO films and nanostructures

    NASA Astrophysics Data System (ADS)

    Larciprete, Maria Cristina; Centini, Marco

    2015-09-01

    Zinc oxide ZnO is a n-type semiconductor having a wide direct band gap (3.37 eV) as well as a non-centrosymmetric crystal structure resulting from hexagonal wurtzite phase. Its wide transparency range along with its second order nonlinear optical properties make it a promising material for efficient second harmonic generation processes and nonlinear optical applications in general. In this review, we present an extensive analysis of second harmonic generation from ZnO films and nanostructures. The literature survey on ZnO films will include some significant features affecting second harmonic generation efficiency, as crystalline structure, film thickness, surface contributes, and doping. In a different section, the most prominent challenges in harmonic generation from ZnO nanostructures are discussed, including ZnO nanowires, nanorods, and nanocrystals, to name a few. Similarly, the most relevant works regarding third harmonic generation from ZnO films and nanostructures are separately addressed. Finally, the conclusion part summarizes the current standing of published values for the nonlinear optical coefficients and for ZnO films and nanostructures, respectively.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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%.

  14. 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

  15. 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.

  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. 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.

  18. Optical second harmonic generation from Langmuir-type molecular monolayers

    SciTech Connect

    Berkovic, G.; Rasing, Th.; Shen, Y.R.

    1987-01-01

    A single molecular layer is generally sufficient to produce observable optical second harmonic generation (SHG). Furthermore, the selection rules governing this process make the SHG from a single monolayer often stronger than that from the medium supporting the monolayer. We have studied SHG from various Langmuir-type monolayers (i.e., monolayers spread on a water surface) in the following contexts: Study of chemical reactions (e.g., polymerization) and two-dimensional phase transitions in molecular monolayers on water. Development of a new technique to evaluate optical nonlinear coefficients of organic molecules, and their relationship to the molecular structure.

  19. 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)

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Second-harmonic-enhanced feedforward laser-intensity-noise stabilization

    NASA Astrophysics Data System (ADS)

    Stefszky, M.; Silberhorn, C.

    2017-05-01

    Quantum nondemolition theory has been well understood for a number of decades, however, applications of such techniques remain limited owing to the increased complexity that these techniques require. In this paper, quantum nondemolition theory is used to investigate the performance of a real-world device, an electro-optic feedforward intensity-noise eater. It is shown that by replacing the typical beam splitter in such a device with a single-pass second-harmonic generation followed by a dichroic mirror the performance of the noise eater can be significantly improved, even with low conversion efficiencies.

  5. Nonresonant Recirculating Type II Second-Harmonic Generator

    NASA Astrophysics Data System (ADS)

    Ross, T. Sean; Moore, Gerald T.

    2004-04-01

    We show an experimental proof of concept for a nonresonant recirculation method to increase the conversion efficiency of second-harmonic generation (SHG) with type II phase matching. As much as a factor-of-4 efficiency increase compared with that of single-pass SHG is possible, provided that the recirculation length is within the coherence length of the pump laser. Nonresonant recirculating SHG may be valuable in systems in which intracavity doubling is not practicable, such as high-power cw bulk solid-state or fiber lasers.

  6. Analysis of magnetic nanoparticles using second harmonic responses

    NASA Astrophysics Data System (ADS)

    Tanaka, Saburo; Suzuki, Toshifumi; Kobayashi, Kazuya; Liao, Shu-Hsien; Horng, Herng-Er; Yang, Hong-Chang

    2017-10-01

    Magnetic particle imaging (MPI) is a new medical imaging technology with a number of potential applications. It is based on utilizing the non-linear magnetization response for magnetic nanoparticles (MNPs). We have proposed a method to improve the detection sensitivity for the magnetization of MNPs, and their imaging technique, based on the detection of a second harmonic of the response using a high Tc SQUID. The advantage of using the second harmonic is that the response can be measured even with small amplitudes. In this paper, superparamagnetic MNPs with different diameters and different compositions of materials were analyzed by this method. In the MNPs, Resovist was found to be almost one order of magnitude larger than that of the other MNPs tested. The magnetic moments of the MNPs were estimated by fitting with the Langevin function to obtain the magnetic moments m of Resovist of 3.62×10-18 [J/T]. The magnetic moment m of Resovist was 7.4 times larger than the other MNPs.

  7. Link between premidnight second harmonic poloidal waves and auroral undulations

    NASA Astrophysics Data System (ADS)

    Motoba, T.; Takahashi, K.; Ukhorskiy, A. Y.; Gkioulidou, M.; Mitchell, D. G.; Lanzerotti, L. J.; Korotova, G. I.; Donovan, E.; Wygant, J. R.; Kletzing, C.; Kurth, W. S.; Blake, J. B.

    2016-12-01

    We report, for the first time, an auroral undulation event on 1 May 2013 observed by an all-sky imager (ASI) at Athabasca (L = 4.6), Canada, for which in situ field and particle measurements in the conjugate magnetosphere were available from a Van Allen Probes spacecraft. The ASI observed a train of auroral undulation structures emerging in the pre-midnight subauroral ionosphere, during the growth phase of a substorm. The undulations propagated westward at a speed of 3-4 km s-1. The successive passage over an observing point yielded quasi-periodic oscillations in diffuse auroral emissions with a period of 40 s. In the conjugate magnetosphere the spacecraft encountered second harmonic poloidal ULF oscillations in the magnetic and electric fields. The field oscillations were accompanied by the corresponding oscillations in energetic particle fluxes. Most interestingly, both field and particle oscillations at the spacecraft had one-to-one association with the auroral luminosity oscillations around its footprint. Our findings strongly suggest that this auroral undulation event is closely linked to the generation of second harmonic poloidal waves.

  8. 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.

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

    PubMed

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

    2014-12-26

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

  10. 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.

  11. 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.

  12. Tuner of a Second Harmonic Cavity of the Fermilab Booster

    SciTech Connect

    Terechkine, I.; Duel, K.; Madrak, R.; Makarov, A.; Romanov, G.; Sun, D.; Tan, C.-Y.

    2015-05-17

    Introducing a second harmonic cavity in the accelerating system of the Fermilab Booster promises significant reduc-tion of the particle beam loss during the injection, transi-tion, and extraction stages. To follow the changing energy of the beam during acceleration cycles, the cavity is equipped with a tuner that employs perpendicularly biased AL800 garnet material as the frequency tuning media. The required tuning range of the cavity is from 75.73 MHz at injection to 105.64 MHz at extraction. This large range ne-cessitates the use of a relatively low bias magnetic field at injection, which could lead to high RF loss power density in the garnet, or a strong bias magnetic field at extraction, which could result in high power consumption in the tuner’s bias magnet. The required 15 Hz repetition rate of the device and high sensitivity of the local RF power loss to the level of the magnetic field added to the challenges of the bias system design. In this report, the main features of a proposed prototype of the second harmonic cavity tuner are presented.

  13. Laser second harmonic generation in a magnetoplasma assisted by an electrostatic wave

    NASA Astrophysics Data System (ADS)

    Tyagi, Yachna; Tripathi, Deepak; Walia, Keshav

    2017-04-01

    A laser produced plasma, and an electrostatic wave, helps to generate a strong harmonic radiation. The electrostatic wave assists k matching and contributes to non-linear coupling. In the case of the Bernstein wave assisted second harmonic, the frequency of the second harmonic is shifted from the laser second harmonic by electron cyclotron frequency. The lower hybrid wave (LHW) assisted second harmonic has frequency slightly shifted from the laser second harmonic. The upper hybrid wave (UHW) assisted second harmonic has frequency shifted by an amount ω that lies between max( ω c , ω p ) and ω U H . At a 0 = 0.1 and n ω , k → / n0 0 = 0.1, the normalized amplitude value the of electrostatic wave assisted second harmonic is quite high near the upper hybrid resonance. The effect of increasing ω c / ω p increases the max value of normalized amplitude.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. On probing conformation of microtubules by second-harmonic generation

    NASA Astrophysics Data System (ADS)

    Sharoukhov, Denis; Lim, Hyungsik

    2016-01-01

    Microtubule (MT) is a component of cytoskeleton playing an important role in a variety of cellular processes. Altering the structure of MT is a crucial mechanism of modulating the function, but it is difficult to measure the in vivo conformation. We present here the use of second-harmonic generation (SHG) for acquiring information about the architecture of MTs in living tissue. Axonal MTs were imaged by polarization-resolved SHG and anisotropy in the molecular structure was determined by means of the second-order tensor analysis. The feasibility of the second-order tensor analysis was tested for measuring the conformational changes induced by MT-stabilizing drug. It demonstrates that the new optical contrast may be useful for investigating the dynamics of MT cytoskeleton in vivo.

  19. 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.

  20. Second harmonic generation in media with inhomogeneous magnetization

    NASA Astrophysics Data System (ADS)

    Kolmychek, I. A.; Dolgikh, I. A.; Zhou, X.; Adeyeye, A. O.; Murzina, T. V.

    2017-09-01

    Anisotropy of the nonlinear magnetooptical (MO) response in regular arrays of Py antidots and «C»-, «U»- and «O»- shaped Py nanoelements is studied by means of the MO Kerr effect at the second harmonic (SH) wavelength. We demonstrate that the values of the MO effect and coercivity depend substantially on the azimuthal orientation of the antidots array relatively to the external magnetic field. In the arrays of «C»-, «U»- and «O»- shaped Py nanoelements the circular dichroism (CD) of the SH response was observed due to the extrinsic chirality of the samples. We demonstrate that the averaged over the azimuthal angle value of the CD depends on the applied to the structure magnetic field.

  1. Efficient Second-Harmonic Generation in Nanocrystalline Silicon Nanoparticles.

    PubMed

    Makarov, Sergey V; Petrov, Mihail I; Zywietz, Urs; Milichko, Valentin; Zuev, Dmitry; Lopanitsyna, Natalia; Kuksin, Alexey; Mukhin, Ivan; Zograf, George; Ubyivovk, Evgeniy; Smirnova, Daria A; Starikov, Sergey; Chichkov, Boris N; Kivshar, Yuri S

    2017-05-10

    Recent trends to employ high-index dielectric particles in nanophotonics are motivated by their reduced dissipative losses and large resonant enhancement of nonlinear effects at the nanoscale. Because silicon is a centrosymmetric material, the studies of nonlinear optical properties of silicon nanoparticles have been targeting primarily the third-harmonic generation effects. Here we demonstrate, both experimentally and theoretically, that resonantly excited nanocrystalline silicon nanoparticles fabricated by an optimized laser printing technique can exhibit strong second-harmonic generation (SHG) effects. We attribute an unexpectedly high yield of the nonlinear conversion to a nanocrystalline structure of nanoparticles supporting the Mie resonances. The demonstrated efficient SHG at green light from a single silicon nanoparticle is 2 orders of magnitude higher than that from unstructured silicon films. This efficiency is significantly higher than that of many plasmonic nanostructures and small silicon nanoparticles in the visible range, and it can be useful for a design of nonlinear nanoantennas and silicon-based integrated light sources.

  2. 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.

  3. 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.

  4. 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.

  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. 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

  7. 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.

  8. Second harmonic generation from an individual amorphous selenium nanosphere

    NASA Astrophysics Data System (ADS)

    Ma, C. R.; Yan, J. H.; Wei, Y. M.; Yang, G. W.

    2016-10-01

    Among the numerous nonlinear optics effects, second harmonic generation (SHG) is always a hotspot and it is extensively used for optical frequency conversion, biomedical imaging, etc. However, SHG is forbidden in a medium with inversion symmetry under the electric-dipole approximation. Here, we demonstrated SHG from a single amorphous selenium (a-Se) nanosphere under near-infrared femtosecond pulse excitation. It was found that SH spectra are tunable with the size of a-Se nanospheres and the SHG efficiency of a single a-Se sphere with a diameter over 300 nm is estimated at 10-8. We also established two physical mechanisms of SHG from the amorphous nanospheres. There is an electric-dipole contribution to the second-order nonlinearity in view of the inevitable structural discontinuity at the surface. The discontinuity of the normal component of the electric field strength leads to the quadrupole-type contributions arising from the large electric field gradient. The SHG process can be enhanced by resonance near the fundamental wavelength, giving rise to the detectable second harmonic (SH) spectra of a single a-Se nanosphere (d > 300 nm) or two small a-Se nanospheres (d = 200 nm) aggregated into a dimer, while the single nanosphere with smaller size (d > 300 nm) is undetectable. As an essential trace element for animals, a-Se features unique biological compatibility and has specific properties of optical nonlinearity within the optical window in biological tissue. This discovery makes a-Se nanospheres promising both in nonlinear optics and biomedicine.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. Functional imaging of muscle cells by second harmonic generation

    NASA Astrophysics Data System (ADS)

    Nucciotti, Valentina; Sacconi, Leonardo; Linari, Marco; Lombardi, Vincenzo; Piazzesi, Gabriella; Piroddi, Nicoletta; Poggesi, Corrado; Tesi, Chiara; Vanzi, Francesco; Pavone, Francesco S.

    2006-02-01

    The intrinsically ordered arrays of proteins (mainly actin and myosin) constituting the myofibrils within muscle cells are at the basis of a strong Second Harmonic Generation (SHG) from muscle fibers and isolated myofibrils. We have characterized the SHG signal with regard to its polarization and potential source within the muscle cell. The lateral resolution that can be achieved through SHG imaging of muscle strongly depends on sample depth. In fact, a comparison between intact muscle fibers and single myofibrils demonstrates that, whereas in both cases the alternation of dark I bands and bright A bands is visible, the contours of these bands are much better resolved in myofibrils than in fibers. Further, imaging of myofibrils revealed the presence of a darker zone in the centre of the A band. These effects of scattering by tissue on the image resolution were also studied with regard to the polarization of the SHG signal. The polarization-dependence of SHG intensity represents a powerful tool for the investigation of the structural dynamics occurring in the emitting proteins during the active cycle of muscle contraction. The prospective to perform functional studies requires a complete characterization of the effects of scattering and possibly multiple emitting populations on the measured SHG signal. Also, SHG is extremely sensitive to the degree of order present in the filament array, offering an interesting potential in the development of non-invasive tools for the diagnosis of degenerative diseases affecting skeletal muscles.

  14. Metrology of Multiphoton Microscopes Using Second Harmonic Generation Nanoprobes.

    PubMed

    Mahou, Pierre; Malkinson, Guy; Chaudan, Élodie; Gacoin, Thierry; Beaurepaire, Emmanuel; Supatto, Willy

    2017-09-19

    In multiphoton microscopy, the ongoing trend toward the use of excitation wavelengths spanning the entire near-infrared range calls for new standards in order to quantify and compare the performances of microscopes. This article describes a new method for characterizing the imaging properties of multiphoton microscopes over a broad range of excitation wavelengths in a straightforward and efficient manner. It demonstrates how second harmonic generation (SHG) nanoprobes can be used to map the spatial resolution, field curvature, and chromatic aberrations across the microscope field of view with a precision below the diffraction limit and with unique advantages over methods based on fluorescence. KTiOPO4 nanocrystals are used as SHG nanoprobes to measure and compare the performances over the 850-1100 nm wavelength range of several microscope objectives designed for multiphoton microscopy. Finally, this approach is extended to the post-acquisition correction of chromatic aberrations in multicolor multiphoton imaging. Overall, the use of SHG nanoprobes appears as a uniquely suited method to standardize the metrology of multiphoton microscopes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Planar light bullets under conditions of second-harmonic generation

    NASA Astrophysics Data System (ADS)

    Sazonov, Sergey V.; Mamaikin, Mikhail S.; Komissarova, Maria V.; Zakharova, Irina G.

    2017-08-01

    We study solutions to second-harmonic-generation equations in two-dimensional media with anomalous dispersion. The analytical solution is obtained in an approximate form of the planar spatiotemporal two-component soliton by means of the averaged Lagrangian method. It is shown that a decrease in the amplitudes of both soliton components and an increase in the value of the transverse coordinate are accompanied by an increase in their temporal duration. Within this variational approach, we have managed to find a stability criterion for the light bullet and a period of oscillations of soliton parameters. Then, we use the obtained form as an initial configuration to carry out the direct numerical simulation of soliton dynamics. We demonstrate stable propagation of spatiotemporal solitons undergoing small oscillations predicted analytically for a long distance. The formation of a two-component light bullet is shown when we launch a pulse only at the fundamental frequency. In addition, we investigate the phase and group-velocity mismatch effects on the propagation of pulses.

  16. Two-Photon Resonant Second Harmonic Generation in Atomic Xeon

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

    Vacuum ultraviolet (VUV) radiation at 124.8 nm (9.93 eV) was produced from two-photon resonant second harmonic generation (SHG) in a Xeon gaseous medium and used to probe molecular samples of acetone, furan, thiophene, ammonia, and methane. The mass spectra recorded from the species with ionization energies below 9.93 eV were dominated by the parent ions. The parent ions were only observed when the incident UV radiation was tuned to resonate with the two-photon transition 5p^5(^2P_{3/2}^0)6p[1/2]_0 - 5p^6 ^1S_0 of Xe at 80119.474 cm^{-1}. The pressure dependence and the resonant nature of the parent ions observed support the mechanism for SHG as the ionization-initiated electric field induced SHG via the third-order nonlinear susceptibility, χ^{(3)}, which is enhanced by the coupling between the 5p^5(^2P_{3/2}^0)6p[1/2]_0 and the nearby 5p^5(^2P_{3/2}^0)5d[1/2]_1 states of Xe atoms.

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

    PubMed

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

    2009-03-07

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-03-01

    Vacuum ultraviolet (VUV) radiation at 124.8 nm (9.93 eV) was produced from two-photon resonant second harmonic generation (SHG) in a xeon gaseous medium and used to probe molecular samples of acetone, furan, thiophene, ammonia, and methane. The mass spectra recorded from the species with ionization energies below 9.93 eV were dominated by the parent ions. The parent ions were only observed when the incident UV radiation was tuned to resonate with the two-photon transition 5p5(P23/20)6p[1/2]0←5p6S10 of Xe at 80 119.474 cm-1. The pressure dependence and the resonant nature of the parent ions observed support the mechanism for SHG as the ionization-initiated electric field induced SHG via the third-order nonlinear susceptibility χ(3), which is enhanced by the coupling between the 5p5(P23/20)6p[1/2]0 and the nearby 5p5(P23/20)5d[1/2]1 states of Xe atoms.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. Second harmonic generation imaging microscopy with a high-power ultrafast fiber laser

    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. SHG is of growing interest to those in the biomedical community studying structural proteins such as collagen and to those in neuroscience using voltage-sensitive dyes. An important consideration in the application of non-linear phenomena such as SHG to routine microscopy is the complexity of the laser source used for excitation. Almost all applications in ultrafast microscopy currently employ mode-locked Ti:sapphire lasers, and though these systems have improved considerably in recent years, they are still expensive, large and complicated for those with skills outside of ultrafast optics. Here we report on SHG microscopy using a high power femtosecond fiber laser. The Femtopower1060 from Fianium Ltd. is an ultrafast fiber laser operating at 1064nm. With a passively mode-locked master source, a high power fiber amplifier and a built-in pulse compressor, the laser produces high quality pulses shorter than 200fs with a repetition rate of 100MHz and an average power of 1W. The unit is turn-key, air-cooled and maintenance free with a small footprint and proves to be an excellent source for SHG and two-photon microscopy at this wavelength outside the range of most Ti:sapphire systems and without those systems' complexity.

  7. Second harmonic generation on self-assembled GaAs/Au nanowires with thickness gradient

    NASA Astrophysics Data System (ADS)

    Belardini, A.; Leahu, G.; Centini, M.; Li Voti, R.; Fazio, E.; Sibilia, C.; Repetto, D.; Buatier de Mongeot, F.

    2017-05-01

    Here we investigated the SH generation at the wavelength of 400 nm (pump laser at 800 nm, 120 fs pulses) of a "metasurface" composed by an alternation of GaAs nano-grooves and Au nanowires capping portions of flat GaAs. The nano-grooves depth and the Au nanowires thickness gradually vary across the sample. The samples are obtained by ion bombardment at glancing angle on a 150 nm Au mask evaporated on a GaAs plane wafer. The irradiation process erodes anisotropically the surface, creating Au nanowires and, at high ion dose, grooves in the underlying GaAs substrate (pattern transfer). The SHG measurements are performed for different pump linear polarization angle at different positions on the "metasurface" in order to explore the regions with optimal conditions for SHG efficiency. The pump polarization angle is scanned by rotating a half-wave retarder plate. While the output SH signal in reflection is analyzed by setting the polarizer in `s' or `p' configuration in front of the detector. The best polarization condition for SHG is obtained in the configuration where the pump and second harmonic fields are both `p' polarized, and the experiments show a SH polarization dependence of the same symmetry of bulk GaAs. Thus, the presence of gold contributes only as field localization effect, but do not contributes directly as SH generator.

  8. 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

  9. 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.

  10. 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.

  11. 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

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

    PubMed

    Neeman, Lior; Ben-Zvi, Regev; Rechav, Katya; Popovitz-Biro, Ronit; Oron, Dan; Joselevich, Ernesto

    2017-02-08

    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.

  13. 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.

  14. Second harmonic generation imaging of skeletal muscle tissue and myofibrils

    NASA Astrophysics Data System (ADS)

    Campagnola, Paul J.; Mohler, William H.; Plotnikov, Sergey; Millard, Andrew C.

    2006-02-01

    Second Harmonic Generation (SHG) imaging microscopy is used to examine the morphology and structural properties of intact muscle tissue. Using biochemical and optical analysis, we characterize the molecular structure underlying SHG from the complex muscle sarcomere. We find that SHG from isolated myofibrils is abolished by extraction of myosin, but is unaffected by removal or addition of actin filaments. We thus determined that the SHG emission arises from domains of the sarcomere containing thick filaments. By fitting the SHG polarization anisotropy to theoretical response curves, we find an orientation for the harmonophore that corresponds well to the pitch angle of the myosin rod α-helix with respect to the thick filament axis. Taken together, these data indicate that myosin rod domains are the key structures giving rise to SHG from striated muscle. Using SHG imaging microscopy, we have also 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. Fast Fourier Transform (FFT) analysis shows quantitatively that the periodicity of the sarcomere structure is unaltered by the clearing process. Also, comparison of the SHG angular polarization dependence shows no change in the supramolecular organization of acto-myosin complexes. 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 pronounced lack of dependence of glycerol concentration on the imaging depth indicates that refractive index matching plays only a minor role in the optical clearing of muscle.

  15. 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.

  16. Giant Optical Second Harmonic Generation in Two-Dimensional Multiferroics.

    PubMed

    Wang, Hua; Qian, Xiaofeng

    2017-08-09

    Nonlinear optical properties of materials such as second and higher order harmonic generation and electro-optic effect play pivotal roles in lasers, frequency conversion, electro-optic modulators, switches, and so forth. The strength of nonlinear optical responses highly depends on intrinsic crystal symmetry, transition dipole moments, specific optical excitation, and local environment. Using first-principles electronic structure theory, here we predict giant second harmonic generation (SHG) in recently discovered two-dimensional (2D) ferroelectric-ferroelastic multiferroics-group IV monochalcogenides (i.e., GeSe, GeS, SnSe, and SnS). Remarkably, the strength of SHG susceptibility in GeSe and SnSe monolayers is more than 1 order of magnitude higher than that in monolayer MoS2, and 2 orders of magnitude higher than that in monolayer hexagonal BN. Their extraordinary SHG is dominated by the large residual of two opposite intraband contributions in the SHG susceptibility. More importantly, the SHG polarization anisotropy is strongly correlated with the intrinsic ferroelastic and ferroelectric orders in group IV monochalcogenide monolayers. Our present findings provide a microscopic understanding of the large SHG susceptibility in 2D group IV monochalcogenide multiferroics from first-principles theory and open up a variety of new avenues for 2D ferroelectrics, multiferroics, and nonlinear optoelectronics, for example, realizing active electrical/optical/mechanical switching of ferroic orders in 2D multiferroics and in situ ultrafast optical characterization of local atomistic and electronic structures using noncontact noninvasive optical SHG techniques.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

    Fukuda, Makoto; Imano, Kazuhiko

    2012-09-01

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

  3. 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.

  4. 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.

  5. [Simulation and analysis of second-harmonic signal based on tunable diode laser absorption spectroscopy].

    PubMed

    Li, Han; Liu, Jian-Guo; He, Ya-Bai; He, Jun-Feng; Yao, Lu; Xu, Zhen-Yu; Chen, Jiu-Ying; Yuan, Song; Kan, Rui-Feng

    2013-04-01

    Tunable diode laser absorption spectroscopy (TDLAS) is a new gas detection technique developed recently with high spectral resolution, high sensitivity and fast time response. The second-harmonic signal of wavelength modulation spectroscopy (WMS) is often used as the detection signal for gas concentration inversion. Using Simulink, a visual modeling and simulation platform, the authors simulated the WMS signal based on TDLAS, and got the second-harmonic signal by using lock-in amplifier algorithm. Digital orthogonal algorithm was studied in this paper. The relationship between second-harmonic signals and the modulation indexes was analyzed by comparing changes of second-harmonic under different modulation indexes, in order to find out the optimized parameters for second-harmonic detection.

  6. Nonclassical correlations and entanglement in intracavity second harmonic generation

    NASA Astrophysics Data System (ADS)

    Lim, Oo-Kaw

    Quantum information science is a rapidly growing field of research that combines the techniques developed in quantum optics with those of information science. One primary goal of the field is to implement a quantum information network using non-classical light sources such as entangled photon pairs. The process of parametric down conversion has been widely used to generate entangled photons as well as twin beams that have intensity correlations below the shot noise limit. The complementary process - second harmonic generation (SHG) is less well studied in comparison. This dissertation presents the techniques of generating non-classical optical fields using SHG in the continuous variable regime of quantum mechanics. Using a potassium niobate crystal in a resonator, bright blue light was generated through frequency doubling of an infrared beam. We report an observation of 1 dB noise reduction in the amplitude fluctuations of the harmonic output. By double-passing the nonlinear crystal sitting inside a resonator, we set up a singly resonant system which allows two harmonic beams to escape at two different ports. Using a self-consistent propagation model and solutions of the traveling wave SHG, we show that such a dual ported cavity can be used to generate entangled beams with nonclassical intensity correlations in the harmonic outputs. We obtain 0.9 dB of twin-beam intensity correlation from the resonator and demonstrate the inseparability of the two beams with a balanced Mach-Zehnder interferometer. In addition to the generation of quantum correlated states of light, we also investigate the dynamic of coherent light in SHG such as the generation of optical vortices. We demonstrate generation and frequency doubling of unit charge vortices in a linear astigmatic resonator. Through an appropriate alignment of a near confocal cavity, we couple higher order transverse modes of the fundamental laser beam into a vortex mode. With the presence of a nonlinear crystal, a

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Second harmonic microscopic imaging and spectroscopic characterization in prostate pathological tissue.

    PubMed

    Huang, Yanyue; Zhuang, Zhengfei

    2014-01-01

    Second harmonic microscopic imaging and spectroscopy technology has become a powerful tool for biomedical studies, especially in cancer research. In this paper, second harmonic generation in benign prostatic hyperplasia (BPH) and prostate cancer (PC) tissues in mouse model (C57BL6) have been reported. Excitated samples with different wavelength near-infrared laser from 780 to 850 nm we found that second harmonic signals from BPH nuclei stronger than that from PC, and a wavelength sensitivity was also observed in this experiment. Providing useful help for prostate malignancy diagnosis and identifying tissue components on clinic. © 2013 Wiley Periodicals, Inc.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

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

    PubMed

    Fuji, Takao; Horio, Takuya; Suzuki, Toshinori

    2007-09-01

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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    Second-harmonic generation (SHG) has proven to be an effective method to both image and detect structural variations in fibrillar collagen. The ability to detect these differences is especially useful in studying diseases like cancer and fibrosis.1 SHG techniques have historically been limited by their ability to penetrate and image through strongly scattering tissues. Recently, optical wavefront shaping has enabled light to be focused through highly scattering media such as biological tissue.2-4 This technology also enables us to examine the dependence of second harmonic generation on the spatial phase of the pump laser. Here, we demonstrate that wavefront shaping can be used to enhance the generation of second harmonic light from collagen fibrils even when scattering is low or non-existent.

  7. 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

  8. 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.

  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. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1992-10-01

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

  12. Fano-resonance-based mode-matching hybrid metasurface for enhanced second-harmonic generation.

    PubMed

    Li, Zhi; Liu, Wenwei; Li, Zhancheng; Cheng, Hua; Chen, Shuqi; Tian, Jianguo

    2017-08-15

    Plasmonic nanostructures have been considered as potential candidates for enhancing the nonlinear upconversion rate at nanoscale levels due to their strong near-field enhancement. Here, we propose a Fano-resonance-based mode-matching hybrid metasurface that combines the advantages of Fano resonances and mode-matching for boosting second-harmonic conversion. A confined and strong near-field intensity is generated by gold nanoantennas within the volume of polycrystalline zinc sulfide nanoparticles, thus resulting in a larger effective second-harmonic coefficient. The combination of the abovementioned features allows for the realization of a second-harmonic generation (SHG) conversion efficiency of 5.55×10(-8), and the SHG signal is twice that obtained with dipole hybrid metasurfaces. Our designed metasurface may pave the way for optimizing nonlinear light-matter interactions at the nanoscale.

  13. 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.

  14. 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.

  15. Planar second-harmonic generation with noncollinear pumps in disordered media.

    PubMed

    Roppo, Vito; Dumay, David; Trull, Jose; Cojocaru, Crina; Saltiel, Solomon M; Staliunas, Kestutis; Vilaseca, Ramon; Neshev, Dragomir N; Krolikowski, Wieslaw; Kivshar, Yuri S

    2008-09-01

    We study experimentally the process of the second harmonic generation by two noncollinear beams in quadratic nonlinear crystals with a disordered structure of ferroelectric domains. We show that the second-harmonic radiation is emitted in the form of two cones as well as in a plane representing the cross-correlation of the two fundamental pulses. We demonstrate the implementation of this parametric process for characterisation of femtosecond pulses, enabling the estimation of pulse width, chirp, and front tilt. This is achieved through monitoring the evolution of the autocorrelation trace inside the nonlinear crystal.

  16. 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.

  17. 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.

  18. 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.

  19. 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

    2017-07-01

    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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Non-collinear interaction model of the second harmonic generation of a copper vapor laser

    NASA Astrophysics Data System (ADS)

    Omatsu, T.; Kuroda, K.; Shimura, T.; Chihara, M.; Itoh, M.; Ogura, I.

    1990-10-01

    We estimated theoretically the conversion efficiency of the second harmonic generation of a copper vapor laser (CVL) beam. Since the CVL beam is only partially coherent, the theory for the coherent beam is useless for the second harmonic generation of the CVL beam. The focused CVL beam was considered as a set of bundles of rays with propagated in different directions through a crystal and non-collinear interaction between these bundles of rays was investigated. On the basis of this model, we found that the conversion efficiency depends on the product of the beam divergence and the beam diameter, and the length of a nonlinear crystal.

  9. Conversion of the optical orbital angular momentum in a plasmon-assisted second-harmonic generation

    SciTech Connect

    Wang, Yongmei; Wei, Dunzhao; Zhu, Yunzhi; Huang, Xiaoyang; Fang, Xinyuan; Zhong, Weihao; Wang, Qianjin; Zhang, Yong; Xiao, Min

    2016-08-22

    We experimentally demonstrate the plasmon-assisted second-harmonic generation of an optical orbital angular momentum (OAM) beam. Because of the shape resonance, the plasmons in a periodic array of rectangular metal holes greatly enhance the nonlinear optical conversion of an OAM state. The OAM conservation (i.e., 2l{sub 1} = l{sub 2} with l{sub 1} and l{sub 2} being the OAM numbers of the fundamental and second-harmonic waves, respectively) holds well under our experimental configuration. Our results provide a potential way to realize nonlinear optical manipulation of an OAM mode in a nano-photonic device.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. Three-dimensional second-harmonic generation imaging of fibrillar collagen in biological tissues.

    PubMed

    Xie, Jiansong; Ferbas, John; Juan, Gloria

    2012-07-01

    Multiphoton-induced second-harmonic generation (SHG) has developed into a very powerful approach for in depth visualization of some biological structures with high specificity. In this unit, we describe the basic principles of three-dimensional SHG microscopy. In addition, we illustrate how SHG imaging can be utilized to assess collagen fibrils in biological tissues. Some technical considerations are also addressed.

  19. 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.

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

    PubMed

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

    2012-06-18

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

  1. Double resonant excitation of the second harmonic of terahertz raditation in dielectric-graphene layered metamaterials

    NASA Astrophysics Data System (ADS)

    Rapoport, Yu; Grimalsky, V.; Lavrinenko, A. V.; Boardman, A.

    2017-09-01

    Excitation of the second harmonic of THz radiation is investigated theoretically in the planar multilayered structure dielectric-graphene-dielectric-graphene-…. It is studied the case of the oblique incidence of the s-polarized fundamental wave, where the electric field is parallel to the interfaces, and generation of the p-type second harmonic wave occurs. The original concept is proposed to employ the double resonance arrangement for the effective generation of the second harmonic. The double resonant case can be realized when a high-permittivity dielectric is at the input of the structure and the vacuum is at the output. The high efficiency is demonstrated; the second harmonic reflectance coefficient is ≥0.01 under realistic values of the collision frequency in graphene >1012 s-1. Such a great efficiency, which is four-five orders of magnitude higher than reported for the graphene-dielectric structures previously, is proposed for the first time. To compute the nonlinear surface currents, two approaches were used, the kinetic and the hydrodynamic. A qualitative agreement between two approaches, proven in the present modeling, ensures an applicability of the results.

  2. 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%.

  3. 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.

  4. 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. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Theoretical Study on the Dual-wavelength Second Harmonic Generation with Transverse Gradient Nested Optical Superlattice

    NASA Astrophysics Data System (ADS)

    Xiao, Xuan; Jiang, Jian; Lu, Yun-qing; Zhang, Jian-dong; Wang, Kai; Zhang, Zu-xing

    2017-06-01

    Dual-wavelength second harmonic generation with transverse gradient nested optical superlattice is investigated. The ratio of SHG of two fundamental wavelengths can be controlled by adjusting the position of incident light. This study shows that the efficiency of SHG is related to the temperature and coherent length of the nested structure.

  12. 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.

  13. 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.

  14. Theory of backward second-harmonic localization in nonlinear left-handed media

    NASA Astrophysics Data System (ADS)

    Centeno, Emmanuel; Ciracì, Cristian

    2008-12-01

    Recent research on photonic crystals possessing a quadratic nonlinear response has revealed a second-harmonic light localization phenomenon that originates from an all-angle phase matching between counterpropagating Bloch modes at the fundamental and double frequencies [E. Centeno , Phys. Rev. Lett. 98, 263903 (2007)]. In this paper, we develop an electromagnetic theory describing the nature of this parametric light localization, which appears in properly design metamaterials or photonic crystals exhibiting nonlinear left-handed behaviors. We demonstrate that interferences between converging phase-matched and diverging anti-phase-matched waves create a localized second-harmonic wave focused on the pump emitter on the scale of half the wavelength. This light trapping is accompanied by the enhancement of the second-harmonic intensity, which linearly increases with the size of the two-dimensional domain. We finally show that the second-harmonic localization effect previously proposed for GaN photonic crystals can also be obtained with LiNbO3 material.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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)

  20. 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.

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

    SciTech Connect

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

    2005-05-15

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

  2. 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.

  3. 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.

  4. 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

  5. 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.

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

    PubMed

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

    2017-03-24

    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.

  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. 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

  9. Coherent combining of second-harmonic generators by active phase control of the fundamental waves.

    PubMed

    Odier, Alice; Durécu, Anne; Melkonian, Jean-Michel; Lombard, Laurent; Lefebvre, Michel; Bourdon, Pierre

    2017-08-15

    Coherent beam combining by active phase control could be useful for power scaling fiber-laser-pumped optical frequency converters. However, a fast phase modulator operating at the frequency-converted wavelength, a non-standard component, would be necessary. Fortunately, nonlinear conversion processes rely on a phase-matching condition allowing for indirect phase control using standard phase modulators. In this Letter, coherent combining of second-harmonic generators is demonstrated in both birefringent and quasi-phase-matching schemes in CW regime. Phase control operates at the fundamental wavelength, using all-fiber electro-optic modulators. An excellent beam combination is achieved with a residual phase error of λ/30 on the second-harmonic wave.

  10. A 0.4-THz Second Harmonic Gyrotron with Quasi-Optical Confocal Cavity

    NASA Astrophysics Data System (ADS)

    Guan, Xiaotong; Fu, Wenjie; Yan, Yang

    2017-09-01

    Mode density is very relevant for harmonic gyrotron cavity. Theoretical investigations suggest that quasi-optical confocal waveguide performs low mode density and good mode-selective character. By selecting the appropriate mode and optimizing the cavity parameters, the quasi-optical confocal cavity is suitable for high-harmonic terahertz gyrotron without mode competition. In order to verify the theoretical analysis, a 0.4-THz second harmonic gyrotron has been designed and experimented. Driven by a 40-kV, 4.75-A electron beam and 7.51-T magnetic field, the gyrotron prototype could generate 6.44 kW of output power at 395.35 GHz, which corresponds to an electron efficiency of 3.4%. There is no mode competition between the second harmonic and fundamental observed in the experiments.

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    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.

  12. 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.

  13. 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.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    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.

  16. 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.

  17. Polarization-resolved second harmonic generation microscopy of chiral G-shaped metamaterials

    NASA Astrophysics Data System (ADS)

    Mamonov, Evgeniy A.; Maydykovskiy, Anton I.; Kolmychek, Irina A.; Magnitskiy, Sergey A.; Murzina, Tatiana V.

    2017-08-01

    Chiral planar metamaterials are known for their possibility to show strong nonlinear optical effects such as second harmonic generation (SHG) circular dichroism or asymmetric SHG. The underlying mechanisms are commonly discussed in terms of local field effects and formation of localized SHG sources (so called "hotspots") that are sensitive to the shape and size of meta-atoms. Nevertheless, a full characterization of the polarization state of the nonlinear optical radiation from the hotspots has not been performed until now. Here we present the results of the polarization-resolved second harmonic generation microscopy studies of planar chiral G-shaped metamaterials. We demonstrate that the SHG radiation coming from the hotspots that are localized within a single meta-atom is partially polarized; moreover, the SHG polarization state reveals the chirality of the structure. The observed effects are attributed to the induced plasmonic current oscillations at the fundamental frequency along with the local field distribution.

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

    PubMed

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

    2017-04-06

    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.

  19. 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.

  20. Nonlinear Optical Magnetism Revealed by Second-Harmonic Generation in Nanoantennas.

    PubMed

    Kruk, Sergey S; Camacho-Morales, Rocio; Xu, Lei; Rahmani, Mohsen; Smirnova, Daria A; Wang, Lei; Tan, Hark Hoe; Jagadish, Chennupati; Neshev, Dragomir N; Kivshar, Yuri S

    2017-06-14

    Nonlinear effects at the nanoscale are usually associated with the enhancement of electric fields in plasmonic structures. Recently emerged new platform for nanophotonics based on high-index dielectric nanoparticles utilizes optically induced magnetic response via multipolar Mie resonances and provides novel opportunities for nanoscale nonlinear optics. Here, we observe strong second-harmonic generation from AlGaAs nanoantennas driven by both electric and magnetic resonances. We distinguish experimentally the contribution of electric and magnetic nonlinear response by analyzing the structure of polarization states of vector beams in the second-harmonic radiation. We control continuously the transition between electric and magnetic nonlinearities by tuning polarization of the optical pump. Our results provide a direct observation of nonlinear optical magnetism through selective excitation of multipolar nonlinear modes in nanoantennas.

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

    PubMed Central

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

    2013-01-01

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

  2. Submillisecond second harmonic holographic imaging of biological specimens in three dimensions

    PubMed Central

    Smith, David R.; Winters, David G.; Bartels, Randy A.

    2013-01-01

    Optical microscopy has played a critical role for discovery in biomedical sciences since Hooke’s introduction of the compound microscope. Recent years have witnessed explosive growth in optical microscopy tools and techniques. Information in microscopy is garnered through contrast mechanisms, usually absorption, scattering, or phase shifts introduced by spatial structure in the sample. The emergence of nonlinear optical contrast mechanisms reveals new information from biological specimens. However, the intensity dependence of nonlinear interactions leads to weak signals, preventing the observation of high-speed dynamics in the 3D context of biological samples. Here, we show that for second harmonic generation imaging, we can increase the 3D volume imaging speed from sub-Hertz speeds to rates in excess of 1,500 volumes imaged per second. This transformational capability is possible by exploiting coherent scattering of second harmonic light from an entire specimen volume, enabling new observational capabilities in biological systems. PMID:24173034

  3. 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.

  4. 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.

  5. 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.

  6. Second-harmonic generation in longitudinal epsilon-near-zero materials

    NASA Astrophysics Data System (ADS)

    Vincenti, M. A.; Kamandi, M.; de Ceglia, D.; Guclu, C.; Scalora, M.; Capolino, F.

    2017-07-01

    We investigate second-harmonic generation from anisotropic or longitudinal epsilon-near-zero materials. We find conversion efficiencies well above their isotropic counterparts owing to additional field intensity enhancement provided by the anisotropy. At the same time, anisotropic epsilon-near-zero materials are also less sensitive to the material's losses compared to the isotropic ones. In turn, these improvements become pivotal for epsilon-near-zero materials that do not possess bulk dipole-allowed quadratic nonlinearities. We predict that second-harmonic generation from a Dy:CdO/Si multilayer with longitudinal epsilon-near-zero properties can exceed the conversion efficiency of a homogeneous Dy:CdO slab of equivalent thickness by at least 20 times for almost any angle of incidence.

  7. 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.

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

    PubMed Central

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

    2012-01-01

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

  9. 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)

  10. 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.

  11. Surface diffusion of Sb on Si(111) measured by second harmonic microscopy

    SciTech Connect

    Allen, C.E.; Seebauer, E.G. )

    1995-01-01

    Surface diffusion of Sb on Si(111) has been studied by second harmonic microscopy, which uses surface second harmonic generation to monitor surface concentration profiles with a 3 [mu]m spatial resolution. At temperatures near 55% of the bulk melting point and in the coverage range 0 < [theta] < 0.12, the activation energy, E[sub diff], and pre-exponential factor, D[sub 0], were found to be 60 [+-] 3 kcal/mol and 6 x 10[sup 3+0.7] cm[sup 2]/s, respectively. The high prefactor and activation energy indicate that the surface diffusion is governed by a recently developed adatom-vacancy mechanism. 38 refs., 4 figs., 1 tab.

  12. 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].

  13. 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.

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

    PubMed

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

    2017-09-01

    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. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. 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.

  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. D-glucose-induced second harmonic generation response in human erythrocytes.

    PubMed

    Lev, Dmitry; Puzenko, Alexander; Manevitch, Alexandra; Manevitch, Zacharia; Livshits, Leonid; Feldman, Yuri; Lewis, Aaron

    2009-02-26

    The first experimental results of the nonresonant second harmonic generation (SHG) studies of human erythrocytes membrane exposed to various glucose concentrations in phosphate buffered saline (PBS solution) are presented in this article. It is shown that the SHG signal from the membrane can be altered as a function of glucose concentration. The link between the variation of the SHG intensity and the membrane dielectric permittivity with glucose is established both theoretically and experimentally by comparison with time domain dielectric spectroscopy (TDDS) measurement data.

  18. 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.

  19. Second-harmonic generation in AlGaAs microdisks in the telecom range.

    PubMed

    Mariani, S; Andronico, A; Lemaître, A; Favero, I; Ducci, S; Leo, G

    2014-05-15

    We report on second-harmonic generation in whispering-gallery-mode AlGaAs microcavities suspended on a GaAs pedestal. Frequency doubling of a 1.58 μm pump is observed with 7×10(-4)   W(-1) conversion efficiency. This device can be integrated in a monolithic photonic chip for classical and quantum applications in the telecom band.

  20. 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.

  1. 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.

  2. Quantifying collagen structure in breast biopsies using second-harmonic generation imaging.

    PubMed

    Ambekar, Raghu; Lau, Tung-Yuen; Walsh, Michael; Bhargava, Rohit; Toussaint, Kimani C

    2012-09-01

    Quantitative second-harmonic generation imaging is employed to assess stromal collagen in normal, hyperplastic, dysplastic, and malignant breast tissues. The cellular scale organization is quantified using Fourier transform-second harmonic generation imaging (FT-SHG), while the molecular scale organization is quantified using polarization-resolved second-harmonic generation measurements (P-SHG). In the case of FT-SHG, we apply a parameter that quantifies the regularity in collagen fiber orientation and find that malignant tissue contains locally aligned fibers compared to other tissue conditions. Alternatively, using P-SHG we calculate the ratio of tensor elements (d(15)/d(31), d(22)/d(31), and d(33)/d(31)) of the second-order susceptibility χ(2) for collagen fibers in breast biopsies. In particular, d(15)/d(31) shows potential differences across the tissue pathology. We also find that trigonal symmetry (3m) is a more appropriate model to describe collagen fibers in malignant tissues as opposed to the conventionally used hexagonal symmetry (C6). This novel method of targeting collagen fibers using a combination of two quantitative SHG techniques, FT-SHG and P-SHG, holds promise for breast tissue analysis and applications to characterizing cancer in a manner that is compatible with clinical practice.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Second Harmonic Correlation Spectroscopy: Theory and Principles for Determining Surface Binding Kinetics.

    PubMed

    Sly, Krystal L; Conboy, John C

    2017-06-01

    A novel application of second harmonic correlation spectroscopy (SHCS) for the direct determination of molecular adsorption and desorption kinetics to a surface is discussed in detail. The surface-specific nature of second harmonic generation (SHG) provides an efficient means to determine the kinetic rates of adsorption and desorption of molecular species to an interface without interference from bulk diffusion, which is a significant limitation of fluorescence correlation spectroscopy (FCS). The underlying principles of SHCS for the determination of surface binding kinetics are presented, including the role of optical coherence and optical heterodyne mixing. These properties of SHCS are extremely advantageous and lead to an increase in the signal-to-noise (S/N) of the correlation data, increasing the sensitivity of the technique. The influence of experimental parameters, including the uniformity of the TEM00 laser beam, the overall photon flux, and collection time are also discussed, and are shown to significantly affect the S/N of the correlation data. Second harmonic correlation spectroscopy is a powerful, surface-specific, and label-free alternative to other correlation spectroscopic methods for examining surface binding kinetics.

  8. Second harmonic generation in one-dimensional nonlinear photonic crystals solved by the transfer matrix method

    NASA Astrophysics Data System (ADS)

    Li, Jing-Juan; Li, Zhi-Yuan; Zhang, Dao-Zhong

    2007-05-01

    The transfer matrix method has been widely used to calculate the scattering of electromagnetic waves. In this paper, we develop the conventional transfer matrix method to analyze the problem of second harmonic generation in a one-dimensional multilayer nonlinear optical structure. In the designed nonlinear photonic crystal structure, the linear and nonlinear optical parameters are both periodically modulated. We have taken into account the multiple reflection and interference effects of both the linear and nonlinear optical waves during the construction of the transfer matrix for each composite layer. Application of this method to multilayer nonlinear photonic crystal structures with different refractive indices indicates that the proposed method is an exact approach and can simulate the generation of the second harmonic field precisely. In an optimum structure, the second harmonic generation efficiency can be several orders of magnitude larger than in a conventional quasi-phase-matched nonlinear structure with the same sample length. The reason is that, due to the presence of photonic band gap edges, the density of states of the electromagnetic fields is large, the group velocity is small, and the local field is enhanced. All three factors contribute to significant enhancement of the nonlinear optical interactions.

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

    NASA Astrophysics Data System (ADS)

    Kobayashi, Takayoshi; Liu, Jun; Okamura, Kotaro

    2012-04-01

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

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. Label-free discrimination of normal and fibroadenomal breast tissues using second harmonic generation imaging.

    PubMed

    Zheng, Liqin; Zhuo, Shuangmu; Chen, Gang; Zhu, Xiaoqin; Jiang, Xingshan; Yan, Jun; Chen, Jianxin; Xie, Shusen

    2011-01-01

    Early detection of fibroadenoma (FA) is critical for preventing subsequent breast cancer. In this work, we show that label-free second harmonic generation (SHG) imaging is feasible and effective in quantitatively differentiating the fibroadenomal tissue from normal breast tissue. With the advent of the clinical portability of miniature SHG microscopy, we believe that the technique has great potential in offering a noninvasive in vivo imaging tool for early detection of FA and monitoring the treatment responses of FA in clinics. Copyright © 2011 Wiley Periodicals, Inc.

  5. 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.

  6. 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.

  7. 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].

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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)

  14. 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.

  15. 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.

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

    PubMed

    Kabir, Mohammad Mahfuzul; Jonayat, A S M; Patel, Sanjay; Toussaint, Kimani C

    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.

  17. 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.

  18. 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.

  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. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Atomically Phase-Matched Second-Harmonic Generation in a 2D Crystal

    DTIC Science & Technology

    2016-08-26

    single or a few atomic layers. Rich physical properties, such as the emerging photoluminescence6,7, excellent transistor on-off ratio8, optical valley...OPEN ORIGINAL ARTICLE Atomically phase-matched second-harmonic generation in a 2D crystal Mervin Zhao1,2,*, Ziliang Ye1,2,*, Ryuji Suzuki3,4,*, Yu...arising from a single atomic layer, where the SH light elucidated important information such as the grain boundaries and electronic structure in these ultra

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. Quantifying external and internal collagen organization from Stokes-vector-based second harmonic generation imaging polarimetry

    NASA Astrophysics Data System (ADS)

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

    2017-10-01

    Collagen organization has been analyzed at both external and internal scales by combining Stokes-vector polarimetry and second harmonic generation microscopy. A significant linear relationship between the diattenuation and the external collagen organization was found. The dominant orientation of the collagen fibers was found to run parallel to the axis of diattenuation. Information on the collagen chirality was obtained from the circular dichroism, which showed also a strong dependence with the internal collagen organization. The results show that certain polarimetric parameters might be useful to extract quantitative information and characterize collagen arrangement.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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}.

  20. Polarization second harmonic generation microscopy provides quantitative enhanced molecular specificity for tissue diagnostics.

    PubMed

    Kumar, Rajesh; Grønhaug, Kirsten M; Romijn, Elisabeth I; Finnøy, Andreas; Davies, Catharina L; Drogset, Jon O; Lilledahl, Magnus B

    2015-09-01

    Due to specific structural organization at the molecular level, several biomolecules (e.g., collagen, myosin etc.) which are strong generators of second harmonic generation (SHG) signals, exhibit unique responses depending on the polarization of the excitation light. By using the polarization second harmonic generation (p-SHG) technique, the values of the second order susceptibility components can be used to differentiate the types of molecule, which cannot be done by the use of a standard SHG intensity image. In this report we discuss how to implement p-SHG on a commercial multiphoton microscope and overcome potential artifacts in susceptibility (χ) image. Furthermore we explore the potential of p-SHG microscopy by applying the technique to different types of tissue in order to determine corresponding reference values of the ratio of second-order χ tensor elements. These values may be used as a bio-marker to detect any structural alterations in pathological tissue for diagnostic purposes. The SHG intensity image (red) in (a) shows the distribution of collagen fibers in ovary tissue but cannot determine the type of collagen fiber. However, the histogram distribution (b) for the values of the χ tensor element ratio can be used to quantitatively identify the types of collagen fibers. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. 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.

  2. 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.

  3. 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

  4. Three-Dimensional Geometry of Collagenous Tissues by Second Harmonic Polarimetry.

    PubMed

    Reiser, Karen; Stoller, Patrick; Knoesen, André

    2017-06-01

    Collagen is a biological macromolecule capable of second harmonic generation, allowing label-free detection in tissues; in addition, molecular orientation can be determined from the polarization dependence of the second harmonic signal. Previously we reported that in-plane orientation of collagen fibrils could be determined by modulating the polarization angle of the laser during scanning. We have now extended this method so that out-of-plane orientation angles can be determined at the same time, allowing visualization of the 3-dimensional structure of collagenous tissues. This approach offers advantages compared with other methods for determining out-of-plane orientation. First, the orientation angles are directly calculated from the polarimetry data obtained in a single scan, while other reported methods require data from multiple scans, use of iterative optimization methods, application of fitting algorithms, or extensive post-optical processing. Second, our method does not require highly specialized instrumentation, and thus can be adapted for use in almost any nonlinear optical microscopy setup. It is suitable for both basic and clinical applications. We present three-dimensional images of structurally complex collagenous tissues that illustrate the power of such 3-dimensional analyses to reveal the architecture of biological structures.

  5. Three-Dimensional Geometry of Collagenous Tissues by Second Harmonic Polarimetry

    DOE PAGES

    Reiser, Karen; Stoller, Patrick; Knoesen, André

    2017-06-01

    Collagen is a biological macromolecule capable of second harmonic generation, allowing label-free detection in tissues; in addition, molecular orientation can be determined from the polarization dependence of the second harmonic signal. Previously we reported that in-plane orientation of collagen fibrils could be determined by modulating the polarization angle of the laser during scanning. We have now extended this method so that out-of-plane orientation angles can be determined at the same time, allowing visualization of the 3-dimensional structure of collagenous tissues. This approach offers advantages compared with other methods for determining out-of-plane orientation. First, the orientation angles are directly calculated frommore » the polarimetry data obtained in a single scan, while other reported methods require data from multiple scans, use of iterative optimization methods, application of fitting algorithms, or extensive post-optical processing. Second, our method does not require highly specialized instrumentation, and thus can be adapted for use in almost any nonlinear optical microscopy setup. It is suitable for both basic and clinical applications. We present three-dimensional images of structurally complex collagenous tissues that illustrate the power of such 3-dimensional analyses to reveal the architecture of biological structures.« less

  6. 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.

  7. 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.

  8. All-prism achromatic phase matching for tunable second-harmonic generation

    SciTech Connect

    Richman, Bruce A.; Bisson, Scott E.; Trebino, Rick; Jacobson, Alexander

    1999-05-01

    Achromatic phase matching (APM) involves dispersing the light entering a nonlinear optical crystal so that a wide range of wavelengths is simultaneously phase matched. We constructed an APM apparatus consisting of six prisms, the final dispersion angle of which was optimized to match to second order in wavelength the type I phase-matching angle of {beta} barium borate (BBO). With this apparatus, we doubled tunable fundamental light from 620 to 700 nm in wavelength using a 4-mm-long BBO crystal. An analogous set of six prisms after the BBO crystal, optimized to second order in second-harmonic wavelength, realigned the output second-harmonic beams. Computer simulations predict that adjustment of a single prism can compensate angular misalignment of any or all the prisms before the crystal, and similarly for the prisms after the crystal. We demonstrated such compensations with the experimental device. The simulations also indicate that the phase-matching wavelength band can be shifted and optimized for different crystal lengths. {copyright} 1999 Optical Society of America

  9. 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.

  10. Double resonant plasmonic nanoantennas for efficient second harmonic generation in zinc oxide

    NASA Astrophysics Data System (ADS)

    Weber, Nils; Protte, Maximilian; Walter, Felicitas; Georgi, Philip; Zentgraf, Thomas; Meier, Cedrik

    2017-05-01

    We demonstrate the efficient generation of second harmonic light in zinc oxide (ZnO) by utilizing double resonant plasmonic nanoantenna arrays. The antenna design is based on two gold dipole rods with plasmonic resonances at ω and 2 ω , enabling strong localization of light at the fundamental frequency ω within the ZnO, as well as improved reemission of the second harmonic generation (SHG) at 2 ω into the far field. Wavelength-dependent SHG measurements show that the intensity of the far-field signal strongly depends on the properties of the ZnO substrate: While a bulk-ZnO substrate causes the SHG signal emitted from the nanoantennas to decrease, a thin-film ZnO substrate provides a strongly enhanced signal from the double resonant antennas. Comparing the wavelength-dependent results from the double resonant antennas with single dipole rods, the enhancement of the SHG intensity is more than twofold. Our experimental results confirm theoretical calculations of the SHG obtained from the double resonant antenna arrays.

  11. 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.

  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 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.

  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. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Quantitative analysis of diseased horse tendons using Fourier-transform-second-harmonic generation imaging

    NASA Astrophysics Data System (ADS)

    Sivaguru, Mayandi; Durgam, Sushmitha; Ambekar, Raghu; Luedtke, David; Fried, Glenn; Stewart, Allison; Toussaint, Kimani C., Jr.

    2011-03-01

    Fourier transform-second-harmonic generation (FT-SHG) imaging is used to quantitatively assess the structural organization of collagen fibers in tendonitis-induced horse tendons. Fiber orientation, isotropy, and the ratio of forward to backward SHG signal (F/B ratio) are used to differentiate the fiber organization between the normal and diseased horse tendons. Each second-harmonic generation (SHG) image is divided into several smaller regions of interest (ROI) and the aforementioned quantitative metrics are calculated across the whole grid. ROIs are further labeled as dark (no or minimal presence of fibers), isotropic (random fiber organization), or anisotropic (regular fiber organization) regions. Results show that the normal tendon possesses minimal isotropic regions and small standard deviations in the histograms of orientation and F/B ratio, indicating an intact and highly regular fiber organization. However, the tendonitis-induced horse tendons possess higher number of dark and isotropic regions, and larger standard deviations of the measured parameters, suggesting significantly disoriented and disorganized collagen fibers. This type of quantification would be highly beneficial in diagnosing and determining the stage of tendonitis in clinical settings. Not limited to tendonitis, the technique could also be applied to other diseases that structurally affect collagen fibers. The advantage of FT-SHG over the conventional polarization microscopy is also discussed.

  4. 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.

  5. 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

  6. 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.

  7. Second harmonic generation studies of adsorption at a liquid-liquid electrochemical interface

    SciTech Connect

    Higgins, D.A.; Corn, R.M. )

    1993-01-14

    The technique of optical second harmonic generation (SHG) is applied to the measurement of molecular adsorption at the interface between two immiscible electrolyte solutions (ITIES). The resonant second harmonic response from 2-(n-octadecylamino) naphthalene-6-sulfonate (ONS) is used in conjunction with interfacial tension measurements to optically determine the relative surface coverage of the anionic surfactant molecule at a charged water-dichloroethane interface. At a pH of 9, ONS adsorption occurs at all potentials positive of the potential of zero charge. The potential-dependent adsorption of ONS can be described by a Frumkin isotherm with a free energy of adsorption that varies linearly with applied potential. The potential dependence of the SHG from the interface provides important information on the position of the adsorbed ONS molecules with respect to the ITIES. At a pH of 3, both the anionic form of ONS and the protonated zwitterionic form of ONS are present at the liquid-liquid interface. At very positive potentials, the anionic ONS at the interface undergoes a field-dependent conversion to the zwitterionic form. 32 refs., 6 figs.

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

    PubMed

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

    2017-01-15

    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%.

  9. Surface diffusion of Sb on Ge(111) monitored quantitatively with optical second harmonic microscopy

    SciTech Connect

    Schultz, K.A.; Seebauer, E.G. )

    1992-11-01

    Surface diffusion of Sb on Ge(111) has been measured with the newly developed technique of optical second harmonic microscopy. In this method, concentration profiles at submonolayer coverage are imaged directly by surface second harmonic generation with 5 {mu} spatial resolution. A Boltzmann--Matano analysis yields the coverage dependence of the diffusivity {ital D} without parametrization. Experiments were performed at roughly 70% of the bulk melting temperature {ital T}{sub {ital m}}. In the coverage range 0{le}{theta}{le}0.6, the activation energy {ital E}{sub diff} remains constant at 47.5{plus minus}1.5 kcal/mol, but the pre-exponential factor {ital D}{sub 0} decreases from 8.7{times}10{sup 3{plus minus}0.4} to 1.6{times}10{sup 2{plus minus}0.4} cm{sup 2}/s. Both {ital E}{sub diff} and {ital D}{sub 0} are quite large, which is consistent with high-temperature measurements in other systems. The inadequacies of current theories for high-temperature surface diffusion are outlined, and a new vacancy model is proposed for low-coverage diffusion. The model accounts semiquantitatively for the large values of {ital E}{sub diff} and {ital D}{sub 0}, and suggests that these quantities may be manipulated using doping levels and photon illumination. An islanding mechanism is proposed to explain the decrease in {ital D}{sub 0} with {theta}.

  10. Surface diffusion of Sb on Ge(111) investigated by second harmonic microscopy

    SciTech Connect

    Schultz, K.A.

    1992-01-01

    Surface diffusion of Sb on Ge(111) has been measured with the newly-developed technique of second harmonic microscopy. In this method, concentration profiles at submonolayer coverage are imaged directly by second harmonic generation with 5 [mu]m spatial resolution. A Boltzmann-Matano analysis of the concentration profiles yields the coverage dependence of the diffusivity D without parameterization. Experiments were performed at roughly 70% of the bulk melting temperature T[sub m]. In the coverage range of 0 < [theta] < 0.6, the activation energy E[sub diff] remains constant at 47.5 [+-] 1.5 kcal/mol. The corresponding pre-exponential factor decreases from 8.7 [times] 10[sup 3[+-]0.4] to 1.6 [times] 10[sup 2[+-]0.4] cm[sup 2]/sec. The results are explained in terms of a new vacancy model for surface diffusion at high-temperatures. The model accounts semiquantitatively for the large values of E[sub diff] and D[sub o], and suggest that these quantities may be manipulated by bulk doping levels and photon illumination of the surface.

  11. 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.

  12. 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).

  13. Note: 15-fs, 15-μJ green pulses from two-stage temporal compressor of ytterbium laser pulses.

    PubMed

    Konyashchenko, A V; Kostryukov, P V; Losev, L L; Tenyakov, S Yu

    2012-10-01

    15-fs, 15-μJ light pulses at the central wavelength of 515 nm were generated by two-stage nonlinear compression of 300-fs, 150-μJ ytterbium laser pulses. The compression was based on the pulse spectrum broadening by self-phase modulation in gas filled capillary and second harmonic generation in crystal.

  14. 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

  15. Epithelial Ovarian Cancer Diagnosis of Second-Harmonic Generation Images: A Semiautomatic Collagen Fibers Quantification Protocol.

    PubMed

    Zeitoune, Angel A; Luna, Johana Sj; Salas, Kynthia Sanchez; Erbes, Luciana; Cesar, Carlos L; Andrade, Liliana Ala; Carvahlo, Hernades F; Bottcher-Luiz, Fátima; Casco, Victor H; Adur, Javier

    2017-01-01

    A vast number of human pathologic conditions are directly or indirectly related to tissular collagen structure remodeling. The nonlinear optical microscopy second-harmonic generation has become a powerful tool for imaging biological tissues with anisotropic hyperpolarized structures, such as collagen. During the past years, several quantification methods to analyze and evaluate these images have been developed. However, automated or semiautomated solutions are necessary to ensure objectivity and reproducibility of such analysis. This work describes automation and improvement methods for calculating the anisotropy (using fast Fourier transform analysis and the gray-level co-occurrence matrix). These were applied to analyze biopsy samples of human ovarian epithelial cancer at different stages of malignancy (mucinous, serous, mixed, and endometrial subtypes). The semiautomation procedure enabled us to design a diagnostic protocol that recognizes between healthy and pathologic tissues, as well as between different tumor types.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Multi-direction high-efficiency second harmonic generation in ellipse structure nonlinear photonic crystals

    SciTech Connect

    Chen, Bao-Qin; Zhang, Chao; Liu, Rong-Juan; Li, Zhi-Yuan

    2014-10-13

    We have designed and fabricated a lithium niobate (LN) nonlinear photonic crystal (NPC) with a two-dimensional (2D) ellipse structure of inverse poling domains. The structure can offer continuously varying reciprocal lattice vectors in different directions to compensate the phase-mismatching during the second harmonic generation (SHG) for diverse pump wavelengths. We consider three propagation directions with large effective nonlinear susceptibility and measure the nonlinear conversion efficiency of SHG. The experimental data are in good agreement with the quantitative calculation results using the effective susceptibility model with pump depletion. With high-efficiency SHG in multiple propagation direction, the 2D ellipse structure of LN NPC has the potential to realize various broadband nonlinear frequency conversion processes in different propagation direction with a single crystal.

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

    PubMed

    Monaghan, Michael G; Kroll, Sebastian; Brucker, Sara Y; Schenke-Layland, Katja

    2016-06-01

    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.

  3. Imaging the noncentrosymmetric structural organization of tendon with Interferometric Second Harmonic Generation microscopy.

    PubMed

    Rivard, Maxime; Popov, Konstantin; Couture, Charles-André; Laliberté, Mathieu; Bertrand-Grenier, Antony; Martin, François; Pépin, Henri; Pfeffer, Christian P; Brown, Cameron; Ramunno, Lora; Légaré, François

    2014-08-01

    We report the imaging of tendon with Interferometric Second Harmonic Generation microscopy. We observe that the noncentrosymmetric structural organization can be maintained along the fibrillar axis over more than 150 μm, while in the transverse direction it is ∼1-15 μm. Those results are explained by modeling tendon as a heterogeneous distribution of noncentrosymmetric nano-cylinders (collagen fibrils) oriented along the fibrillar axis. The preservation of the noncentrosymmetric structural organization over multiple tens of microns reveals that tendon is made of domains in which the ratio between fibrils with positive and negative polarity is unbalanced. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. In vitro imaging of thyroid tissues using two-photon excited fluorescence and second harmonic generation.

    PubMed

    Huang, Zufang; Li, Zuanfang; Chen, Rong; Lin, Juqiang; Li, Yongzeng; Li, Chao

    2010-08-01

    To evaluate the feasibility of two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) imaging to discriminate the normal, nodular goiter and papillary cancerous thyroid tissue. In total, 45 fresh thyroid specimens (normal, 15; nodular goiter, 12; and papillary cancerous, 18) from 31 subjects were directly imaged by the TPEF and SHG combination method. The microstructure of follicle and collagen structure in thyroid tissue were clearly identified, morphologic changes between normal, nodular goiter, and papillary cancerous thyroid tissue were well characterized by using two-photon excitation fluorescence. SHG imaging of the collagen matrix also revealed the differences between normal and abnormal. Our preliminary study suggests that the TPEF and SHG combination method might be a useful tool in revealing pathologic changes in thyroid tissue.

  5. 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.

  6. The Binding of Roxarsone at the Silica/Water Interface Studied with Second Harmonic Generation

    NASA Astrophysics Data System (ADS)

    Konek, Christopher; Ostrowski, David; Geiger, Franz

    2005-03-01

    Arsenic is a carcinogen that can also cause chronic poisoning when ingested via drinking water in quantities as low as 10 micrograms/L. In the US, organic arsenicals such as Roxarsone are commonly used as feed additives in the poultry industry. The use of poultry litter as fertilizer results in environmental arsenic deposition rates of up to 50 metric tons per year; the subsequent environmental fate of Roxarsone is unknown. We use second harmonic generation (SHG) to study the thermodynamics and kinetics of Roxarsone binding to environmentally relevant mineral oxide/water interfaces. Roxarsone binding to water/SiO2 interfaces is fully reversible, consistent with high Roxarsone mobility. Results from Langmuir isotherm measurements and surface SHG spectra are presented as well.

  7. Multi-stimuli manipulation of antiferromagnetic domains assessed by second-harmonic imaging.

    PubMed

    Chauleau, J-Y; Haltz, E; Carrétéro, C; Fusil, S; Viret, M

    2017-08-01

    Among the variety of magnetic textures available in nature, antiferromagnetism is one of the most 'discrete' because of the exact cancellation of its staggered internal magnetization. It is therefore very challenging to probe. However, its insensitivity to external magnetic perturbations, together with the intrinsic sub-picosecond dynamics, make it very appealing for tomorrow's information technologies. Thus, it is essential to understand the microscopic mechanisms governing antiferromagnetic domains to achieve accurate manipulation and control. Using optical second-harmonic generation, a unique and laboratory-available tool, we succeeded in imaging with sub-micrometre resolution both electric and antiferromagnetic orders in the model multiferroic BiFeO3. We show here that antiferromagnetic domains can be manipulated with low power consumption, using sub-coercive electric fields and sub-picosecond light pulses. Interestingly, we also show that antiferromagnetic and ferroelectric domains can behave independently, thus revealing that magneto-electric coupling can lead to various arrangements of the two orders.

  8. Studies of molecular adsorbates at interfaces by optical second-harmonic generation. [p-nitrobenzoic acid

    SciTech Connect

    Tom, H.W.K.; Heinz, T.F.; Shen, Y.R.

    1982-12-01

    Optical second-harmonic generation (SHG) is surface-specific and has the sensitivity to detect submonolayers of molecules. It can be applied to study molecular adsorbates at the interface between any two centrosymmetric media. This has been demonstrated by using dye and p-nitrobenzoic acid (PNBA) molecules adsorbed on smooth fused quartz substrates as examples. With resonant SHG, the S/sub 0/ A..-->.. S/sub 2/ transition of the adsorbed dye molecules was measured. From the polarization dependence of the SHG, the orientation of PNBA at both the air/quartz and the ethanol/quartz interfaces was deduced. By varying the concentration of PNBA in ethanol, an adsorption isotherm for PNBA at the ethanol/quartz interfaces was also obtained.

  9. 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.

  10. 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.

  11. Resonant second-harmonic generation in a ballistic graphene transistor with an ac-driven gate

    NASA Astrophysics Data System (ADS)

    Korniyenko, Y.; Shevtsov, O.; Löfwander, T.

    2016-01-01

    We report a theoretical study of time-dependent transport in a ballistic graphene field effect transistor. We develop a model based on Floquet theory describing Dirac electron transmission through a harmonically driven potential barrier. Photon-assisted tunneling results in excitation of quasibound states at the barrier. Under resonance conditions, the excitation of the quasibound states leads to promotion of higher-order sidebands and, in particular, an enhanced second harmonic of the source-drain conductance. The resonances in the main transmission channel are of the Fano form, while they are of the Breit-Wigner form for sidebands. For weak ac drive strength Z1, the dynamic Stark shift scales as Z14, while the resonance broadens as Z12. We discuss the possibility of utilizing the resonances in prospective ballistic high-frequency devices, in particular frequency doublers operating at high frequencies and low temperatures.

  12. 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.

  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. Macromolecular structure of cellulose studied by second-harmonic generation imaging microscopy

    NASA Astrophysics Data System (ADS)

    Brown, R. Malcom; Millard, Andrew C.; Campagnola, Paul J.

    2003-11-01

    The macromolecular structure of purified cellulose samples is studied by second-harmonic generation (SHG) imaging microscopy. We show that the SHG contrast in both Valonia and Acetobacter cellulose strongly resembles that of collagen from animal tissues, both in terms of morphology and polarization anisotropy. Polarization analysis shows that microfibrils in each lamella are highly aligned and ordered and change directions by 90° in adjacent lamellae. The angular dependence of the SHG intensity fits well to a cos2 θ distribution, which is characteristic of the electric dipole interaction. Enzymatic degradation of Valonia fibers by cellulase is followed in real time by SHG imaging and results in exponential decay kinetics, showing that SHG imaging microscopy is ideal for monitoring dynamics in biological systems.

  15. Study of ocean slicks by nonlinear laser processes. I - Second-harmonic generation

    NASA Astrophysics Data System (ADS)

    Frysinger, Glenn S.; Asher, William E.; Korenowski, Gerald M.; Barger, William R.; Klusty, Mark A.; Frew, Nelson M.; Nelson, Robert K.

    1992-04-01

    Reflected optical second-harmonic generation (SHG) was applied for the first time to in situ study of the air-sea interface. SHG signals were detected from the first several molecular layers of the ocean surface during the SAR X Band Ocean Nonlinearities (SAXON) Chesapeake Light Tower experiment in 1988, and during experiments on Nantucket Sound at the Woods Hole Oceanographic Institution in 1989. The SHG response of the ocean surface was observed to correlate with increased slick activity and surface tension measurements of surface water organic content. The SHG reponse was similar for naturally occurring slicks and for artificially created slicks of several known materials. The SHG signal intensity was also used to estimate the second-order nonlinear optical susceptibility of the ocean surface. It was determined that the SHG nonlinear laser technique is a useful noninvasive probe for in situ studies of ocean surface chemistry.

  16. 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.

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

    PubMed

    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.

  18. 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.

  19. 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.

  20. 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.

  1. Defect mode in the bulk plasmon-polariton gap for giant enhancement of second harmonic generation

    NASA Astrophysics Data System (ADS)

    Reyes Gómez, F.; Mejía-Salazar, J. R.; Oliveira, Osvaldo N.; Porras-Montenegro, N.

    2017-08-01

    We demonstrate that the defect mode in the bulk plasmon-polariton gap of one-dimensional defective metamaterial photonic crystals can be used to achieve a giant enhancement of more than four orders of magnitude in the second harmonic (SH) conversion efficiency only by changing the incidence angle. Furthermore, the one-dimensional photonic crystal may be designed in order for the SH wave to coincide with the edge of the Bragg gap or with the defect mode inside this gap, in which case the enhancement is even higher. Because of the robustness of the bulk plasmon-polariton gap to scaling effects, the present proposal may inspire different routes for frequency upconversion, signal filtering, and switching photonic devices.

  2. Epithelial Ovarian Cancer Diagnosis of Second-Harmonic Generation Images: A Semiautomatic Collagen Fibers Quantification Protocol

    PubMed Central

    Zeitoune, Angel A; Luna, Johana SJ; Sanchez Salas, Kynthia; Erbes, Luciana; Cesar, Carlos L; Andrade, Liliana ALA; Carvahlo, Hernades F; Bottcher-Luiz, Fátima; Casco, Victor H; Adur, Javier

    2017-01-01

    A vast number of human pathologic conditions are directly or indirectly related to tissular collagen structure remodeling. The nonlinear optical microscopy second-harmonic generation has become a powerful tool for imaging biological tissues with anisotropic hyperpolarized structures, such as collagen. During the past years, several quantification methods to analyze and evaluate these images have been developed. However, automated or semiautomated solutions are necessary to ensure objectivity and reproducibility of such analysis. This work describes automation and improvement methods for calculating the anisotropy (using fast Fourier transform analysis and the gray-level co-occurrence matrix). These were applied to analyze biopsy samples of human ovarian epithelial cancer at different stages of malignancy (mucinous, serous, mixed, and endometrial subtypes). The semiautomation procedure enabled us to design a diagnostic protocol that recognizes between healthy and pathologic tissues, as well as between different tumor types. PMID:28469386

  3. Second harmonic spectroscopy to optically detect valley polarization in 2D materials

    NASA Astrophysics Data System (ADS)

    Hipolito, F.; Pereira, Vitor M.

    2017-06-01

    Valley polarization (VP), an induced imbalance in the populations of a multi-valley electronic system, allows emission of second harmonic (SH) light even in centrosymmetric crystals such as graphene. Whereas in systems such as MoS{{}2} or BN this adds to their intrinsic quadratic response, SH generation in a multi-valley inversion-symmetric crystal can provide a direct measure of valley polarization. By computing the nonlinear response and characterizing theoretically the respective SH as a function of polarization, temperature, electron density, and degree of VP, we demonstrate the possibility of disentangling and individually quantifying the intrinsic and valley contributions to the SH. A specific experimental setup is proposed to obtain direct quantitative information about the degree of VP and allow its remote mapping. This approach could prove useful for direct, contactless, real-space monitoring of valley injection and other applications of valley transport and valleytronics.

  4. 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

  5. Multi-stimuli manipulation of antiferromagnetic domains assessed by second-harmonic imaging

    NASA Astrophysics Data System (ADS)

    Chauleau, J.-Y.; Haltz, E.; Carrétéro, C.; Fusil, S.; Viret, M.

    2017-08-01

    Among the variety of magnetic textures available in nature, antiferromagnetism is one of the most `discrete' because of the exact cancellation of its staggered internal magnetization. It is therefore very challenging to probe. However, its insensitivity to external magnetic perturbations, together with the intrinsic sub-picosecond dynamics, make it very appealing for tomorrow's information technologies. Thus, it is essential to understand the microscopic mechanisms governing antiferromagnetic domains to achieve accurate manipulation and control. Using optical second-harmonic generation, a unique and laboratory-available tool, we succeeded in imaging with sub-micrometre resolution both electric and antiferromagnetic orders in the model multiferroic BiFeO3. We show here that antiferromagnetic domains can be manipulated with low power consumption, using sub-coercive electric fields and sub-picosecond light pulses. Interestingly, we also show that antiferromagnetic and ferroelectric domains can behave independently, thus revealing that magneto-electric coupling can lead to various arrangements of the two orders.

  6. Conversion efficiency enhancement technique for a quasiphase matched second-harmonic generation device

    NASA Astrophysics Data System (ADS)

    Shinozaki, Keisuke; Takamori, Takeshi; Watanabe, Kenji; Fukunaga, Toshiaki; Kamijoh, Takeshi

    1992-07-01

    Conversion efficiency enhancement techniques have been demonstrated for quasi-phase matched (QPM) second-harmonic generation (SHG). First, a technique is described for confining the high fundamental optical power density in a waveguide with a domain-inverted grating (SHG waveguide) (i.e., a technique for monolithic integration), the SHG waveguide, and a distributed Bragg reflector (DBR). A 40-percent increase in the conversion compared with a conventional device without a DBR was achieved under QPM conditions. Also described is a method of automatically satisfying QPM conditions, using a laser diode (LD) with antireflection-coated facets. The InP/InGaAsP LDs were used and it was confirmed that the LD oscillated at a wavelength satisfying the QPM conditions. The normalized conversion efficiency was 4.1 percent/W per sq cm.

  7. [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.

  8. Efficient intracavity second-harmonic generation at 1063 nm in a GdCOB crystal

    NASA Astrophysics Data System (ADS)

    Wu, Z. C.; Liu, W. M.

    2011-12-01

    We report an efficient intracavity second-harmonic generation (SHG) at 1063 nm in a non-linear optical crystal, GdCa4O(BO3)3 (GdCOB), performed with a diode end pumped continuous-wave (CW) Nd:GdVO4 laser. In the case of a laser with an a-cut 0.4 at % Nd:GdVO4 crystal frequency-doubled with a GdCOB crystal cut for Type I frequency doubling. A CW SHG output power of 2.25 W has been obtained using a 15 mm long GCOB crystal. The optical conversion efficiency with respect to the incident pump power was 12.4%.

  9. 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.

  10. Second harmonic study of acid-base equilibrium at gold nanoparticle/aqueous interface

    NASA Astrophysics Data System (ADS)

    Ma, Jianqiang; Mandal, Sarthak; Bronsther, Corin; Gao, Zhenghan; Eisenthal, Kenneth B.

    2017-09-01

    Interfacial acid-base equilibrium of the capping molecules is a key factor to stabilize gold nanoparticles (AuNP) in solution. In this study we used Second Harmonic (SH) generation to measure interfacial potential and obtained a surface pKa value of 3.3 ± 0.1 for the carboxyl group in mercaptoundecanoic acid (MUA) molecule at an AuNP/aqueous interface. This pKa value is smaller than its bulk counterpart and indicates that the charged carboxylate group is favored at the AuNP surface. The SH findings are consistent with the effects of the noble metal (gold) surface on a charge in solution, as predicted by the method of images.

  11. 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

  12. 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.

  13. Identification of stacking faults in silicon carbide by polarization-resolved second harmonic generation microscopy.

    PubMed

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

    2017-07-07

    Although silicon carbide is a highly promising crystalline material for a wide range of electronic devices, extended and point defects which perturb the lattice periodicity hold deep implications with respect to device reliability. There is thus a great need for developing new methods that can detect silicon carbide defects which are detrimental to device functionality. Our experiment demonstrates that polarization-resolved second harmonic generation microscopy can extend the efficiency of the "optical signature" concept as an all-optical rapid and non-destructive set of investigation methods for the differentiation between hexagonal and cubic stacking faults in silicon carbide. This technique can be used for fast and in situ characterization and optimization of growth conditions for epilayers of silicon carbide and similar materials.

  14. Optical Second Harmonic Generation in Plasmonic Nanostructures: From Fundamental Principles to Advanced Applications.

    PubMed

    Butet, Jérémy; Brevet, Pierre-François; Martin, Olivier J F

    2015-11-24

    Plasmonics has emerged as an important research field in nanoscience and nanotechnology. Recently, significant attention has been devoted to the observation and the understanding of nonlinear optical processes in plasmonic nanostructures, giving rise to the new research field called nonlinear plasmonics. This review provides a comprehensive insight into the physical mechanisms of one of these nonlinear optical processes, namely, second harmonic generation (SHG), with an emphasis on the main differences with the linear response of plasmonic nanostructures. The main applications, ranging from the nonlinear optical characterization of nanostructure shapes to the optimization of laser beams at the nanoscale, are summarized and discussed. Future directions and developments, made possible by the unique combination of SHG surface sensitivity and field enhancements associated with surface plasmon resonances, are also addressed.

  15. 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.

  16. 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.

  17. 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.

  18. Observation of spontaneous polarization misalignments in periodically poled crystals using second-harmonic generation microscopy.

    PubMed

    Tzeng, Yu-Yi; Zhuo, Zong-Yan; Lee, Ming-Yin; Liao, Chien-Sheng; Wu, Pei-Chun; Huang, Chin-Jie; Chan, Ming-Che; Liu, Tzu-Ming; Lin, Yen-Yin; Chu, Shi-Wei

    2011-06-06

    Periodically poled crystal (PPC) is a key component for nonlinear optical applications. Its poling quality relies largely on successful domain inversion and the alignment of spontaneous polarization (SP) vectors in each domain. Here we report the unexpected observation of bulk second harmonic generation (SHG) in PPC when excitation propagating along its optical axis. Based on its tensorial nature, SHG is highly sensitive to the orientation of SP, and therefore the misalignment of SP in each domain of PPC can be revealed noninvasively by SHG microscopy. This nonlinear imaging modality provides optical sectioning capability with 3D sub-micrometer resolution, so it will be useful for in situ investigation of poling quality in PPC.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. In pixel analysis of molecular structure with Stokes vector resolved second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    We report on measurements and characterization of polarization properties of Second Harmonic (SH) signals using a four-channel photon counting based Stokes polarimeter from type I collagen and starch granules. In this way, the critical polarization parameters including the degree of polarization (DOP), the degree of linear polarization (DOLP), and the degree of circular polarization (DOCP), are extracted from the reconstructed Stokes vector based SH images in a pixel-by-pixel manner. The measurements are further extended to determine the molecular structure and orientation of the samples by varying the polarization states of the incident light and recording the resulting Stokes parameters of the SH signal. The combination of SHG microscopy and Stokes polarimeter hence makes a powerful tool to investigate the structural order of starch granules under water and heating environment.

  9. Second-harmonic focusing by a nonlinear turbid medium via feedback-based wavefront shaping.

    PubMed

    Qiao, Yanqi; Peng, Yajun; Zheng, Yuanlin; Ye, Fangwei; Chen, Xianfeng

    2017-05-15

    Scattering has usually been considered detrimental for optical focusing or imaging. Recently, more and more research has shown that strongly scattering materials can be utilized to focus coherent light by controlling or shaping the incident light. Here, purposeful focusing of second-harmonic waves, which are generated and scattered from nonlinear turbid media via feedback-based wavefront shaping, is presented. This Letter shows a flexible manipulation of both disordered linear and nonlinear scattering signals, indicating more controllable degrees of freedom for the description of turbid media. This technique also provides a possible way to an efficient transmission of nonlinear signal at a desired location in the form of a focal point or other patterns. With the combination of random nonlinear optics and wavefront shaping methods, more interesting applications can be expected in the future, such as nonlinear transmission matrix, multi-frequency imaging, and phase-matching-free nonlinear optics.

  10. 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

  11. Application of quantitative second-harmonic generation microscopy to posterior cruciate ligament for crimp analysis studies

    NASA Astrophysics Data System (ADS)

    Lee, Woowon; Rahman, Hafizur; Kersh, Mariana E.; Toussaint, Kimani C.

    2017-04-01

    We use second-harmonic generation (SHG) microscopy to quantitatively characterize collagen fiber crimping in the posterior cruciate ligament (PCL). The obtained SHG images are utilized to define three distinct categories of crimp organization in the PCL. Using our previously published spatial-frequency analysis, we develop a simple algorithm to quantitatively distinguish the various crimp patterns. In addition, SHG microscopy reveals both the three-dimensional structural variation in some PCL crimp patterns as well as an underlying helicity in these patterns that have mainly been observed using electron microscopy. Our work highlights how SHG microscopy could potentially be used to link the fibrous structural information in the PCL to its mechanical properties.

  12. 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

  13. 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.

  14. 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.

  15. Speckle correlation measurement in a disordered medium observed through second-harmonics generation

    NASA Astrophysics Data System (ADS)

    Ito, Tetsu; Tomita, Makoto

    2004-03-01

    We examined speckle correlation in a disordered medium consisting of LiNbO3 corpuscles, by observing the total intensity of the second-harmonics (SH) light generated by angular correlated two excitation beams. The total SH intensity showed a correlation peak at θ˜0, where θ was the angle between two excitation beams, and decreased as θ was increased. The observation could be understood as the effect of the constructive interference between two volume speckle patterns produced by the excitation beams inside the medium, and the peak could reflect the mutual correlation between two patterns. The experimental results showed good agreements with a theoretical analysis based on a diffusion approximation.

  16. 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.

  17. Experimental demonstration of two-photon Mueller matrix second-harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Okoro, Chukwuemeka; Toussaint, Kimani C.

    2016-01-01

    We present the first experimental demonstration of two-photon Mueller matrix second-harmonic generation (SHG) microscopy for the extraction of representative Mueller matrices. Individual SHG images of porcine sample sets are divided into subimages, and the local nonlinear two-photon Mueller matrices (M) and degree of polarization (p) are determined. Results of the two-photon Mueller matrices from different sample types and the effects of thickness on the mean p distribution per polarization basis are investigated. We find that the p distribution shape changes and an associated bimodal mean difference (μd) increases with thickness. Our approach has potential as a quantitative imaging technique and can be applied to other multiphoton coherent imaging modalities.

  18. 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.

  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. 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.

  2. 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.

  3. Optical second-harmonic diffraction study of anisotropic surface diffusion: CO on Ni(110)

    SciTech Connect

    Xiao, X.; Zhu, X.D.; Daum, W.; Shen, Y.R. )

    1992-10-15

    We describe in detail a technique using optical second-harmonic (SH) diffraction from a one-dimensional laser-induced monolayer grating to probe surface diffusion of adsorbates and its anisotropy on a solid surface. The case of CO on Ni(110) is used as a demonstration. The two orthogonal and independent diffusion tensor components along (1{bar 1}0) and (001) are measured, exhibiting a strong anisotropy in both the activation energy {ital E}{sub diff} and the preexponential factor {ital D}{sub 0} in the diffusion coefficients. A compensation effect between {ital E}{sub diff} and {ital D}{sub 0} is observed. In comparison with CO/Ni(111) and CO/Ni(100), our result suggests that the Ni(110) surface seen by CO is much smoother than Ni(111) and Ni(100). Both advantages and limitations of the present technique are mentioned and possible complications in the data analysis are discussed.

  4. 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.

  5. Theory of surface second-harmonic generation for semiconductors including effects of nonlocal operators

    NASA Astrophysics Data System (ADS)

    Anderson, Sean M.; Tancogne-Dejean, Nicolas; Mendoza, Bernardo S.; Véniard, Valérie

    2015-02-01

    We formulate a theoretical approach of surface second-harmonic generation from semiconductor surfaces based on the length gauge and the electron density operator. Within the independent particle approximation, the nonlinear second-order surface susceptibility tensor χa b c(-2 ω ;ω ,ω ) is calculated, including in one unique formulation (i) the scissors correction, needed to have the correct value of the energy band gap, (ii) the contribution of the nonlocal part of the pseudopotentials, routinely used in ab initio band-structure calculations, and (iii) the derivation for the inclusion of the cut function, used to extract the surface response. The first two contributions are described by spatially nonlocal quantum-mechanical operators and are fully taken into account in the present formulation. As a test case of the approach, we calculate χx x x(-2 ω ;ω ,ω ) for the clean Si (001 )2 ×1 reconstructed surface. The effects of the scissors correction and of the nonlocal part of the pseudopotentials are discussed in surface nonlinear optics. The scissors correction shifts the spectrum to higher energies though the shifting is not rigid and mixes the 1 ω and 2 ω resonances, and has a strong influence in the line shape. The effects of the nonlocal part of the pseudopotentials keeps the same line shape of | χ2×1 x x x(-2 ω ;ω ,ω ) | , but reduces its value by 15%-20%. Therefore the inclusion of the three aforementioned contributions is very important and makes our scheme unprecedented and opens the possibility to study surface second-harmonic generation with more versatility and providing more accurate results.

  6. Second harmonic poloidal waves observed by Van Allen Probes in the dusk-midnight sector

    NASA Astrophysics Data System (ADS)

    Min, Kyungguk; Takahashi, Kazue; Ukhorskiy, Aleksandr Y.; Manweiler, Jerry W.; Spence, Harlan E.; Singer, Howard, J.; Claudepierre, Seth G.; Larsen, Brian A.; Soto-Chavez, A. Rualdo; Cohen, Ross J.

    2017-03-01

    This paper presents observations of ultralow-frequency (ULF) waves from Van Allen Probes. The event that generated the ULF waves occurred 2 days after a minor geomagnetic storm during a geomagnetically quiet time. Narrowband pulsations with a frequency of about 7 mHz with moderate amplitudes were registered in the premidnight sector when Probe A was passing through an enhanced density region near geosynchronous orbit. Probe B, which passed through the region earlier, did not detect the narrowband pulsations but only broadband noise. Despite the single-spacecraft measurements, we were able to determine various wave properties. We find that (1) the observed waves are a second harmonic poloidal mode propagating westward with an azimuthal wave number estimated to be ˜100; (2) the magnetic field fluctuations have a finite compressional component due to small but finite plasma beta (˜0.1); (3) the energetic proton fluxes in the energy ranging from above 10 keV to about 100 keV exhibit pulsations with the same frequency as the poloidal mode and energy-dependent phase delays relative to the azimuthal component of the electric field, providing evidence for drift-bounce resonance; and (4) the second harmonic poloidal mode may have been excited via the drift-bounce resonance mechanism with free energy fed by the inward radial gradient of ˜80 keV protons. We show that the wave active region is where the plume overlaps the outer edge of ring current and suggest that this region can have a wide longitudinal extent near geosynchronous orbit.

  7. 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.

  8. Towards protein-crystal centering using second-harmonic generation (SHG) microscopy

    SciTech Connect

    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.

    2013-05-01

    The potential of second-harmonic generation (SHG) microscopy for automated crystal centering to guide synchrotron X-ray diffraction of protein crystals has been explored. 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 β{sub 2} 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.

  9. Second harmonic generation analysis of early Achilles tendinosis in response to in vivo mechanical loading

    PubMed Central

    2011-01-01

    Background Tenocytes have been implicated in the development of tendinosis, a chronic condition commonly seen in musculoskeletal overuse syndromes. However, the relation between abnormal tenocyte morphology and early changes in the fibrillar collagen matrix has not been closely examined in vivo. Second harmonic generation (SHG) microscopy is a recently developed technique which allows examination of fibrillar collagen structures with a high degree of specificity and resolution. The goal of this study was to examine the potential utility of SHG and multiphoton excitation fluorescence (MPEF) microscopy in understanding the relation between tenocytes and their surrounding collagenous matrix in early tendon overuse lesions. Methods Histological preparations of tendon were prepared from adult male Sprague-Dawley rats subjected to an Achilles tendon loading protocol for 12 weeks (Rat-A-PED), or from sedentary age-matched cage controls. Second harmonic generation and multiphoton excitation fluorescence were performed simultaneously on these tissue sections in at least three different areas. Results SHG microscopy revealed an association between abnormal tenocyte morphology and morphological changes in the fibrillar collagen matrix of mechanically loaded Achilles tendons. Collagen density and organization was significantly reduced in focal micro-regions of mechanically loaded tendons. These pathological changes occurred specifically in association with altered tenocyte morphology. Normal tendons displayed a regular distribution of fibre bundles, and the average size of these bundles as determined by Gaussian analysis was 0.47 μm ± 0.02. In comparison, fibre bundle measures from tendon regions in the vicinity of abnormal tenocytes could not be quantified due to a reduction in their regularity of distribution and orientation. Conclusions SHG microscopy allowed high resolution detection of focal tendon abnormalities affecting the fibrillar collagen matrix. With ongoing

  10. Surface diffusion of In on Ge(111) studied by optical second harmonic microscopy

    SciTech Connect

    Suni, I.I.; Seebauer, E.G. )

    1994-05-01

    Surface diffusion of In on Ge(111) has been measured by optical second harmonic microscopy. This technique employs surface second harmonic generation to directly image submonolayer surface concentration profiles. The coverage dependence of the diffusivity [ital D] can then be obtained from a Boltzmann--Matano analysis. In the coverage range 0.1[lt][theta][lt]0.48, the activation energy [ital E][sub diff] decreased with increasing coverage, ranging from 31 kcal/mol at [theta]=0.1 to 23 kcal/mol at [theta]=0.48. Over the same coverage range, the pre-exponential factor [ital D][sub 0] decreased from 5[times]10[sup 2] to 1[times]10[sup [minus]1] cm[sup 2]/s. This gradual change reflects a change in diffusion mechanism arising from the disordered nature of the Ge(111) surface. At low coverages, In adatoms sink into the top layer of Ge, and diffusion is dominated by thermal formation of adatom-vacancy pairs. At high coverages, diffusion occurs by normal site-to-site hopping. The gradual change in diffusion parameters with coverage was interrupted by an apparent phase transition at [theta]=0.16. At this point, both [ital E][sub diff] and [ital D][sub 0] peaked sharply at 41 kcal/mol and 6[times]10[sup 5] cm[sup 2]/s, respectively. The desorption energy [ital E][sub des] was measured by temperature programmed desorption. [ital E][sub des] decreased from 60 kcal/mol at submonolayer coverages to 55 kcal/mol at multilayer coverages.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. Effect of Precipitation Morphology on the Second Harmonic Generation of Ultrasonic Wave During Tempering in P92 Steel

    NASA Astrophysics Data System (ADS)

    Sahu, Minati Kumari; Swaminathan, J.; Bandyopadhyay, Nil Ratan; Sagar, Sarmistha Palit

    2017-10-01

    This paper reports the generation of second harmonic of ultrasound wave and the variation of its amplitude with the precipitation morphology in P92 steel. P92 steel samples were normalized at 1075 °C and tempered in a range of 715-835 °C at a step of 30 °C to study the effect of nucleation and growth of precipitates on the amplitude of second harmonic of ultrasound wave. It has been observed that the non linear ultrasonic (NLU) parameter which is defined as the ratio of the amplitude of second harmonic to the square of the amplitude of the transmitted signal frequency increases with the nucleation and growth of precipitates. Whereas when the growth of precipitate is restricted and fine secondary precipitates start to nucleate, it decreases. The maximum of NLU parameter corresponds to the optimum tempering temperature for the studied material.

  18. 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.

  19. 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.

  20. Topological charge transformation of beams with embedded fractional phase step in the process of second harmonic generation

    NASA Astrophysics Data System (ADS)

    Stanislovaitis, Paulius; Matijosius, Aidas; Ivanov, Maksym; Smilgevicius, Valerijus

    2017-10-01

    We demonstrate collinear second harmonic generation performed with a beam with an embedded initial phase singularity of strength | l| =1/2. We examine the law of topological charge conservation during this process. Despite the instability of the initial singularity, we observe a counterintuitive topological charge doubling. In the second harmonic, we observe an optical vortex of strength (topological charge) | l| =1. The conservation of topological charge is confirmed by both numerical simulations and the experiment. We also provide a qualitative explanation of the process.

  1. 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.

  2. Spatial modulation of second-harmonic generation via nonlinear Raman-Nath diffraction in an aperiodically poled lithium tantalite.

    PubMed

    Chen, Yuping; Dang, Weirui; Zheng, Yuanlin; Chen, Xianfeng; Deng, Xuewei

    2013-07-01

    We propose and experimentally demonstrate a colorful nonlinear Raman-Nath second-harmonic generation by engineering the quadratic nonlinearity χ((2)) in an aperiodically poled lithium tantalite. The engineered nonlinear structure allows multicolored Raman-Nath second-harmonic signal outputs along a uniform direction, which cannot be achieved in a uniform nonlinear grating. The diffraction angles are independent of the beam waist and the position of incidence. This verifies that nonlinear Raman-Nath diffraction does not depend on the local superlattice structure where the fundamental frequency beam locates, but on the whole nonlinear χ((2)) crystal.

  3. Measurement of orientation and susceptibility ratios using a polarization-resolved second-harmonic generation holographic microscope

    PubMed Central

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

    2012-01-01

    Three-dimensional second-harmonic fields, sample orientation, and susceptibility ratios of biological samples are measured using polarization-resolved second-harmonic generation (SHG) microscopy. The three-dimensional (3D) polarization is gathered by measurement of a series of holograms for which excitation and analyzer polarizations are systematically varied, and the 3D SHG field is recovered through numerical back propagation. Harmonophore orientation is resolved in 3D from a sub-set of polarization-resolved SHG holograms. We further expand on previous approaches for the determination of susceptibility ratios, adding the calculation of multiple ratio values to allow intrinsic verification. PMID:23024896

  4. 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.

  5. Second-harmonic microscopy of unstained living cardiac myocytes: measurements of sarcomere length with 20-nm accuracy

    NASA Astrophysics Data System (ADS)

    Boulesteix, Thierry; Beaurepaire, Emmanuel; Sauviat, Martin-Pierre; Schanne-Klein, Marie-Claire

    2004-09-01

    We extend second-harmonic generation (SHG) microscopy to the measurement of sarcomere length in unstained living cardiac myocytes with 20-nm accuracy. We quantify individual sarcomere shortening in the presence of saxitoxin and find that it is in agreement with mechanical measurements of atrial tissue contracture. This functional application of SHG microscopy is generally applicable to quantify the physiological effects of drugs on contractile tissue. Our data also suggest that packed myosin heads in sarcomere thick filaments are responsible for the large second-harmonic endogenous signal in muscle tissue.

  6. 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).

  7. Doubly forbidden second-harmonic generation from isotropic suspensions: Studies on the purple membrane of Halobacterium halobium

    NASA Astrophysics Data System (ADS)

    Allcock, P.; Andrews, D. L.; Meech, S. R.; Wigman, A. J.

    1996-04-01

    In this paper we report results on second-harmonic generation (SHG) from aqueous suspensions of the purple membrane of Halobacterium halobium. A detailed theory describing this SHG signal is supported by results for the angular distribution of the harmonic emission and validated by experimental measurements with circularly polarized pump radiation-a condition that normally precludes SHG. Hence we identify the precise mechanism for second-harmonic emission in this macroscopically isotropic but microscopically ordered system, resolving confusion over whether the signal should be considered coherent SHG or incoherent hyper-Rayleigh scattering.

  8. 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.

  9. 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%.

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

    SciTech Connect

    Feller, Marla Beth

    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.

  11. Initiation of Explosion of Pentaerythritol Tetranitrate by Pulses of the First and Second Harmonics of a Neodymium Laser

    NASA Astrophysics Data System (ADS)

    Aduev, B. P.; Nurmukhametov, D. R.; Furega, R. I.; Liskov, I. Yu.

    2015-12-01

    It is shown that during initiation of explosion of pentaerythritol tetranitrate (PETN) by the second harmonic of a laser, the primary process of energy absorption is ionization of PETN molecules by the mechanism of two-photon absorption. Possibility of regulating the PETN sensitivity by adding nickel nanoparticles to laser irradiation is established.

  12. 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.

  13. NONLINEAR OPTICS PHENOMENA: Second harmonic and drag current generation by an s-polarised wave rapidly heating a metal

    NASA Astrophysics Data System (ADS)

    Bezhanov, S. G.; Uryupin, Sergey A.

    2010-01-01

    The dependences of the second harmonic and drag current generation efficiency on the electron collision frequency, changing during a rapid heating of electrons and the lattice in a metal in the case of absorption of s-polarised femtosecond radiation, are established.

  14. 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.

  15. Second harmonic generation correlation spectroscopy for characterizing translationally diffusing protein nanocrystals

    PubMed Central

    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.

    2016-01-01

    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. PMID:27377382

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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