WorldWideScience

Sample records for harmonic generation study

  1. Study of high-order harmonic generation from nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Singhal, H; Naik, P A; Srivastava, A K; Singh, A; Chari, R; Khan, R A; Chakera, J A; Gupta, P D [Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India); Ganeev, R A, E-mail: himanshu@rrcat.gov.i [Institute of Electronics, Uzbekistan Academy of Sciences, Tashkent 100125 (Uzbekistan)

    2010-01-28

    An experimental study on high-order harmonic generation from the interaction of 45 fs Ti:sapphire laser pulses with preformed plasma plumes of metal nanoparticles was carried out. Highly efficient harmonic generation in the range of 9th order to 19th order was observed for Ag nanoparticles. The stability of harmonic generation was enhanced by utilizing special target fabrication techniques and through optimizing the conditions of plasma plume formation. Broadband harmonic generation was observed through the optimization of femtosecond laser intensity and through the use of spectrally broadened laser pulses. The harmonic generation was compared for various target materials (nano and bulk) and for Ag nanoparticle targets prepared from different fabrication techniques. Efficient generation of even- and odd-order harmonics was observed through the use of two-colour pulses. The observations can be explained qualitatively from symmetry breaking of high-order harmonic generation through the introduction of second harmonic pulses. The spectral broadening and shift of harmonic radiation can be understood from the self-modulation of the laser and harmonic radiation in the plasma.

  2. Studies of harmonic generation in free electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Goldammer, K.

    2007-11-12

    Nonlinear harmonic generation is one of the most interesting aspects of Free Electron Lasers under study today. It provides for coherent, high intensity radiation at higher harmonics of the FEL resonant frequency. The sources, numerical simulation and applications of harmonic radiation in cascaded High Gain Harmonic Generation FELs were the subject of this thesis. Harmonic emission in FELs originates from harmonic microbunching of the particles and the particular electron trajectory during FEL interaction. Numerical FEL simulation codes model these analytical equations and predict the performance of Free Electron Lasers with good accuracy. This thesis has relied heavily upon the FEL simulation code Genesis 1.3 which has been upgraded in the framework of this thesis to compute harmonic generation in a self-consistent manner. Tests against analytical predictions suggest that the harmonic power levels as well as harmonic gain lengths are simulated correctly. A benchmark with the FEL simulation code GINGER yields excellent agreement of the harmonic saturation length and saturation power. The new version of the simulation code Genesis was also tested against measurements from the VUV-FEL FLASH at DESY. The spectral power distributions of fundamental and third harmonic radiation were recorded at 25.9 nm and 8.6 nm, respectively. The relative bandwidths (FWHM) were in the range of 2 % for both the fundamental as well as the third harmonic, which was accurately reproduced by time-dependent simulations with Genesis. The new code was also used to propose and evaluate a new design for the BESSY Soft X-Ray FEL, a cascaded High Gain Harmonic Generation FEL proposed by BESSY in Berlin. The original design for the BESSY High Energy FEL line requires four HGHG stages to convert the initial seed laser wavelength of 297.5 nm down to 1.24 nm. A new scheme is proposed that makes use of fifth harmonic radiation from the first stage and reduces the number of HGHG stages to three. It

  3. Phononic High Harmonic Generation

    OpenAIRE

    Ganesan, Adarsh; Do, Cuong; Seshia, Ashwin A.

    2016-01-01

    This paper reports the first experimental evidence for phononic low-order to high-order harmonic conversion leading to high harmonic generation. Similar to parametric resonance, phononic high harmonic generation is also mediated by a threshold dependent instability of a driven phonon mode. Once the threshold for instability is met, a cascade of harmonic generation processes is triggered. Firstly, the up-conversion of first harmonic phonons into second harmonic phonons is established. Subseque...

  4. Studies of surfaces using optical second-harmonic generation

    Energy Technology Data Exchange (ETDEWEB)

    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.

  5. Second harmonic generation at fatigue cracks by low-frequency Lamb waves: Experimental and numerical studies

    Science.gov (United States)

    Yang, Yi; Ng, Ching-Tai; Kotousov, Andrei; Sohn, Hoon; Lim, Hyung Jin

    2018-01-01

    This paper presents experimental and theoretical analyses of the second harmonic generation due to non-linear interaction of Lamb waves with a fatigue crack. Three-dimensional (3D) finite element (FE) simulations and experimental studies are carried out to provide physical insight into the mechanism of second harmonic generation. The results demonstrate that the 3D FE simulations can provide a reasonable prediction on the second harmonic generated due to the contact nonlinearity at the fatigue crack. The effect of the wave modes on the second harmonic generation is also investigated in detail. It is found that the magnitude of the second harmonic induced by the interaction of the fundamental symmetric mode (S0) of Lamb wave with the fatigue crack is much higher than that by the fundamental anti-symmetric mode (A0) of Lamb wave. In addition, a series of parametric studies using 3D FE simulations are conducted to investigate the effect of the fatigue crack length to incident wave wavelength ratio, and the influence of the excitation frequency on the second harmonic generation. The outcomes show that the magnitude and directivity pattern of the generated second harmonic depend on the fatigue crack length to incident wave wavelength ratio as well as the ratio of S0 to A0 incident Lamb wave amplitude. In summary, the findings of this study can further advance the use of second harmonic generation in damage detection.

  6. Harmonic arbitrary waveform generator

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Brock Franklin

    2017-11-28

    High frequency arbitrary waveforms have applications in radar, communications, medical imaging, therapy, electronic warfare, and charged particle acceleration and control. State of the art arbitrary waveform generators are limited in the frequency they can operate by the speed of the Digital to Analog converters that directly create their arbitrary waveforms. The architecture of the Harmonic Arbitrary Waveform Generator allows the phase and amplitude of the high frequency content of waveforms to be controlled without taxing the Digital to Analog converters that control them. The Harmonic Arbitrary Waveform Generator converts a high frequency input, into a precision, adjustable, high frequency arbitrary waveform.

  7. Second harmonic generation imaging

    CERN Document Server

    2013-01-01

    Second-harmonic generation (SHG) microscopy has shown great promise for imaging live cells and tissues, with applications in basic science, medical research, and tissue engineering. Second Harmonic Generation Imaging offers a complete guide to this optical modality, from basic principles, instrumentation, methods, and image analysis to biomedical applications. The book features contributions by experts in second-harmonic imaging, including many pioneering researchers in the field. Written for researchers at all levels, it takes an in-depth look at the current state of the art and possibilities of SHG microscopy. Organized into three sections, the book: Provides an introduction to the physics of the process, step-by-step instructions on how to build an SHG microscope, and comparisons with related imaging techniques Gives an overview of the capabilities of SHG microscopy for imaging tissues and cells—including cell membranes, muscle, collagen in tissues, and microtubules in live cells—by summarizing experi...

  8. A Case Study of Harmonic Impact on a Motor-Generator Set System

    Energy Technology Data Exchange (ETDEWEB)

    Joung, Pil-Bum [KHNP CRI, Daejeon (Korea, Republic of)

    2016-10-15

    Motor-Generator Sets are usually used to supply power to a Control Element Drive Mechanism Control System (CEDMCS) at nuclear power plants with pressurized water reactors. Two Motor-Generator Sets, which have 100% capacity, are operated in parallel to improve the reliability of the power supply to the CEDMCS. Fig. 1 presents a diagram of a Motor- Generator Set system. The system of a Motor-Generator Set is composed of electrical equipment, such as a motor, a fly-wheel, and a generator, an exciter and protection-control device, such as a protective relay, synchro check relay, and an auto voltage regulator. In general, the harmonic impact of electrical equipment increases the deterioration of the equipment, the motor, and the generator’s lifetime, which can also be caused by vibration and over-heating and maloperation of the protection-control device. In this paper, we came to understand the harmonic impact on the Motor-Generator Set system through a study of delaying parallel operation by non-operation of the synchro check relay and the fault of under voltage protective relay. Thus, KHNP has established and applied the measures of harmonic reduction by the CEDMCS, such as limiting the voltage harmonic distortion to less than 10%, which is described in IEEE Std 519.

  9. Efficient third harmonic generation in photonic nanowires

    OpenAIRE

    Broderick, N.G.R.; Lohe, M. A.; Lee, T; Shaaram, Afshar V.; Monro, T.M.

    2013-01-01

    In a photonic nanowire the strong optical confinement allows for the phase matching of nonlinear interactions that would not normally be phase matched, while the large longitudinal component of the electric field serves to further enhance the effective nonlinearity. Thus such waveguides are good choices for studying nonlinear effects such as third harmonic generation. In this paper we analyse third harmonic generation analytically and present the criteria for optimal harmonic generation. In a...

  10. Study of Nonlinear Propagation of Ultrashort Laser Pulses and Its Application to Harmonic Generation

    Science.gov (United States)

    Weerawarne, Darshana L.

    Laser filamentation, which is one of the exotic nonlinear optical phenomena, is self-guidance of high-power laser beams due to the dynamic balance between the optical Kerr effect (self-focusing) and other nonlinear effects such as plasma defocusing. It has many applications including supercontinuum generation (SCG), high-order harmonic generation (HHG), lightning guiding, stand-off sensing, and rain making. The main focus of this work is on studying odd-order harmonic generation (HG) (i.e., 3o, 5o, 7o, etc., where o is the angular frequency) in centrosymmetric media while a high-power, ultrashort harmonic-driving pulse undergoes nonlinear propagation such as laser filamentation. The investigation of highly-controversial nonlinear indices of refraction by measuring low-order HG in air is carried out. Furthermore, time-resolved (i.e., pump-probe) experiments and significant harmonic enhancements are presented and a novel HG mechanism based on higher-order nonlinearities is proposed to explain the experimental results. C/C++ numerical simulations are used to solve the nonlinear Schrodinger equation (NLSE) which supports the experimental findings. Another project which I have performed is selective sintering using lasers. Short-pulse lasers provide a fascinating tool for material processing, especially when the conventional oven-based techniques fail to process flexible materials for smart energy/electronics applications. I present experimental and theoretical studies on laser processing of nanoparticle-coated flexible materials, aiming to fabricate flexible electronic devices.

  11. Harmonic generation in the generalized Sagdeev pseudopotential

    Science.gov (United States)

    Akbari-Moghanjoughi, M.

    2017-09-01

    In this paper, we study the nonlinear harmonic generation effect in different oscillator models. For weakly nonlinear systems, we use the generalized forced Korteweg de Vries Burgers (KdVB) and modified KdVB (mKdVB) models in order to classify three fundamentally different harmonic structures in a nonlinear dynamical system. The first is called the internal harmonic structure which exists due to the self oscillation of the system in the absence of dissipation effect and is shown to follow either relations of nf or (2n - 1)f depending on the symmetry of oscillator potential in which n is an integer number and f is the fundamental frequency which is exactly obtained for the Helmholtz oscillator. The second structure is the resonant harmonics which appears in the presence of damping and follows the harmonic structure nf0 in which f0 is the linear resonance frequency. Finally, the last harmonic structure appears in the presence of dissipation and external periodic forcing effects which we call the external harmonic pattern. It is shown that the external harmonic pattern, in which f1 is the driving frequency, always follows the nf1 rule regardless of the potential symmetry. We then extend our analysis to study the harmonic generation in the fully nonlinear generalized Sagdeev potential for real plasmas with isothermal and adiabatic ion fluids and investigate the effects of different plasma parameters such as the fractional ion temperature and normalized ion acoustic speed on all three kinds of harmonic generation.

  12. High-order harmonic generation in laser plasma: Recent achievements

    Science.gov (United States)

    Ganeev, R. A.

    2012-07-01

    Recent studies of high-order harmonic generation of laser radiation in laser-produced plasma show new attractive developments in this field. Those include generation of extended harmonics in plasma plumes, new approaches in application of two-color pump, generation of extremely broadened harmonics, further developments in harmonic generation in clusters (fullerenes, carbon nanotubes, in-situ produced nanoparticles), destructive interference of harmonics from different emitters, resonance-induced enhancement of harmonics, applications of high pulse repetition rate lasers for the enhancement of average power of generating harmonics, observation of quantum path signatures, etc. We review some of these recent developments.

  13. High-harmonic generation in amorphous solids.

    Science.gov (United States)

    You, Yong Sing; Yin, Yanchun; Wu, Yi; Chew, Andrew; Ren, Xiaoming; Zhuang, Fengjiang; Gholam-Mirzaei, Shima; Chini, Michael; Chang, Zenghu; Ghimire, Shambhu

    2017-09-28

    High-harmonic generation in isolated atoms and molecules has been widely utilized in extreme ultraviolet photonics and attosecond pulse metrology. Recently, high-harmonic generation has been observed in solids, which could lead to important applications such as all-optical methods to image valance charge density and reconstruct electronic band structures, as well as compact extreme ultraviolet light sources. So far these studies are confined to crystalline solids; therefore, decoupling the respective roles of long-range periodicity and high density has been challenging. Here we report the observation of high-harmonic generation from amorphous fused silica. We decouple the role of long-range periodicity by comparing harmonics generated from fused silica and crystalline quartz, which contain the same atomic constituents but differ in long-range periodicity. Our results advance current understanding of the strong-field processes leading to high-harmonic generation in solids with implications for the development of robust and compact extreme ultraviolet light sources.Although higher harmonic generation from solids has become of interest in many fields, its observation is typically limited to crystalline solids. Here, the authors demonstrate that higher harmonics can be generated from amorphous solids.

  14. Second harmonic generation study of the air/liquid interface of different solutions

    Science.gov (United States)

    Sun, Kai; Li, Dechun; Cao, Lihua; Li, Ying; Song, Xinwang; Li, Chunxiu; Li, Yaping; Cao, Xulong

    2013-09-01

    As an intrinsically surface-specific technique, Second Harmonic Generation (SHG) is widely used in the study of interface in recent years. The SHG signals from the air/liquid interface of Rhodamine B and Sodium Dodecyl Benzene Sulfonate (SDBS) aqueous solutions were obtained and analyzed, which demonstrate that the SHG signal intensity of Rhodamine B is stronger than that of SDBS. Compared with one single solution, the SHG signal intensity of the mixed aqueous solution of Rhodamine B and SDBS decreases. From the UV-VIS absorption spectrum of the two aqueous solutions, it can be seen that Rhodamine B has an absorption peak closer to the second harmonic frequency. Therefore the resonance of the second harmonic frequency with the frequency of the dipole transitions of the chromophore considerably enhances the signal intensity. Furthermore, the hyperpolarizabilities of the molecules of Rhodamine B and SDBS are calculated from first-principles, which reveal that the hyperpolarizability of Rhodamine B molecule is greater than that of SDBS molecule. When they are mixed, molecules of Rhodamine B and SDBS gather together because Rhadamine B molecule carries positive surface charge and SDBS is anionic surfactant, causing the decrease of the SHG intensity of the mixed solution.

  15. High order harmonic generation in rare gases

    Energy Technology Data Exchange (ETDEWEB)

    Budil, Kimberly Susan [Univ. of California, Davis, CA (United States)

    1994-05-01

    The process of high order harmonic generation in atomic gases has shown great promise as a method of generating extremely short wavelength radiation, extending far into the extreme ultraviolet (XUV). The process is conceptually simple. A very intense laser pulse (I ~1013-1014 W/cm2) is focused into a dense (~1017 particles/cm3) atomic medium, causing the atoms to become polarized. These atomic dipoles are then coherently driven by the laser field and begin to radiate at odd harmonics of the laser field. This dissertation is a study of both the physical mechanism of harmonic generation as well as its development as a source of coherent XUV radiation. Recently, a semiclassical theory has been proposed which provides a simple, intuitive description of harmonic generation. In this picture the process is treated in two steps. The atom ionizes via tunneling after which its classical motion in the laser field is studied. Electron trajectories which return to the vicinity of the nucleus may recombine and emit a harmonic photon, while those which do not return will ionize. An experiment was performed to test the validity of this model wherein the trajectory of the electron as it orbits the nucleus or ion core is perturbed by driving the process with elliptically, rather than linearly, polarized laser radiation. The semiclassical theory predicts a rapid turn-off of harmonic production as the ellipticity of the driving field is increased. This decrease in harmonic production is observed experimentally and a simple quantum mechanical theory is used to model the data. The second major focus of this work was on development of the harmonic "source". A series of experiments were performed examining the spatial profiles of the harmonics. The quality of the spatial profile is crucial if the harmonics are to be used as the source for experiments, particularly if they must be refocused.

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

    Science.gov (United States)

    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.

  17. Numerical study of fourth-harmonic generation of a picosecond laser pulse with time predelay

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, T.; Kato, Y.; Daido, H. [Institute of Laser Engineering, Osaka University, Yamada-oka 2-6, Suita, Osaka 565 (Japan)

    1996-06-01

    We describe fourth-harmonic generation of a picosecond laser pulse with KDP crystals. The coupled nonlinear equations for the parametric process including the third-order nonlinear susceptibility have been solved. Applying a time predelay in the doubling crystal between the extraordinary and the ordinary waves of the fundamental pulse causes the group-velocity mismatch and the nonlinear phase shift in the doubling crystal to be compensated for each other, resulting in pulse duration compression at the fourth-harmonic wavelength. It is shown that the reduction from a 1-ps fundamental pulse to a 0.25-ps fourth-harmonic pulse can be achieved at an incident intensity of 50 GW/cm{sup 2}. {copyright} {ital 1996 Optical Society of America.}

  18. Does high harmonic generation conserve angular momentum?

    CERN Document Server

    Fleischer, Avner; Diskin, Tzvi; Sidorenko, Pavel; Cohen, Oren

    2013-01-01

    High harmonic generation (HHG) is a unique and useful process in which infrared or visible radiation is frequency up converted into the extreme ultraviolet and x ray spectral regions. As a parametric process, high harmonic generation should conserve the radiation energy, momentum and angular momentum. Indeed, conservation of energy and momentum have been demonstrated. Angular momentum of optical beams can be divided into two components: orbital and spin (polarization). Orbital angular momentum is assumed to be conserved and recently observed deviations were attributed to propagation effects. On the other hand, conservation of spin angular momentum has thus far never been studied, neither experimentally nor theoretically. Here, we present the first study on the role of spin angular momentum in extreme nonlinear optics by experimentally generating high harmonics of bi chromatic elliptically polarized pump beams that interact with isotropic media. While observing that the selection rules qualitatively correspond...

  19. Fluorescent DNA probes at liquid/liquid interfaces studied by surface second harmonic generation

    OpenAIRE

    Licari, Giuseppe Léonardo; Brevet, Pierre-François; Vauthey, Eric

    2016-01-01

    The properties of a series of oxazole yellow dyes, including the dicationic YOPRO-1 and its homodimeric parent YOYO-1 and two monocationic dyes (YOSAC-1 and YOSAC-3), have been investigated at the dodecane/water interface using stationary and time-resolved surface second harmonic generation (SSHG) combined with quantum chemical calculations. Whereas YOYO-1 exists predominantly as a H-dimer in aqueous solution, the stationary SSHG spectra reveal that such dimers are not formed at the interface...

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

    Energy Technology Data Exchange (ETDEWEB)

    Feller, Marla Beth [Univ. of California, Berkeley, CA (United States)

    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.

  1. Studying the effect of photodynamic therapy (PDT) to enhance healing of femur fractures using polarimetric second-harmonic generation microscopy

    Science.gov (United States)

    Golaraei, Ahmad; Raja, Vaishnavi; Akens, Margarete K.; Wilson, Brian C.; Barzda, Virginijus

    2017-07-01

    Linear polarization-in, polarization-out second-harmonic generation microscopy was used to study the effect of Photodynamic therapy treatment on enhancing the healing of femur fracture by investigating the ultrastructure of collagen as a major component of bone matrix.

  2. High Harmonic Generation XUV Spectroscopy for Studying Ultrafast Photophysics of Coordination Complexes

    Science.gov (United States)

    Ryland, Elizabeth S.; Lin, Ming-Fu; Benke, Kristin; Verkamp, Max A.; Zhang, Kaili; Vura-Weis, Josh

    2017-06-01

    Extreme ultraviolet (XUV) spectroscopy is an inner shell technique that probes the M_{2,3}-edge excitation of atoms. Absorption of the XUV photon causes a 3p→3d transition, the energy and shape of which is directly related to the element and ligand environment. This technique is thus element-, oxidation state-, spin state-, and ligand field specific. A process called high-harmonic generation (HHG) enables the production of ultrashort (˜20fs) pulses of collimated XUV photons in a tabletop instrument. This allows transient XUV spectroscopy to be conducted as an in-lab experiment, where it was previously only possible at accelerator-based light sources. Additionally, ultrashort pulses provide the capability for unprecedented time resolution (˜50fs IRF). This technique has the capacity to serve a pivotal role in the study of electron and energy transfer processes in materials and chemical biology. I will present the XUV transient absorption instrument we have built, along with ultrafast transient M_{2,3}-edge absorption data of a series of small inorganic molecules in order to demonstrate the high specificity and time resolution of this tabletop technique as well as how our group is applying it to the study of ultrafast electronic dynamics of coordination complexes.

  3. Fullerenes: The attractive medium for harmonic generation

    Science.gov (United States)

    Ganeev, R. A.

    2011-01-01

    We review the results of systematic experimental studies of high-order harmonic generation (HHG) in C60-rich laser-produced plasma under different plasma conditions and laser parameters. The morphology of fullerene clusters before and after ablation is analyzed to define the optimal conditions of excitation of C60-containing targets. The enhancement of HHG efficiency in C60-rich plasmas by using the two-color pump technique is discussed. The conversion efficiency for the odd and even harmonics in the vicinity of surface plasmon resonance of the C60-containing plasma (40-70 nm) was estimated to be in the range of 10-4.

  4. Study on the crucial conditions for efficient third harmonic generation using a metal-hybrid-metal plasmonic slot waveguide.

    Science.gov (United States)

    Wu, Tingting; Shum, Perry Ping; Sun, Yunxu; Shao, Xuguang; Huang, Tianye

    2015-01-12

    We provide a comprehensive study on the efficient third harmonic generation (THG) in a lossy metal-hybrid-metal asymmetric plasmonic slot waveguide (MHM) to develop a method for efficient THG by focusing on the modal phase-matching condition (PMC), the third-order nonlinear susceptibility of the nonlinear interactive material, and the pump-harmonic modal overlap in conjunction with reasonable linear propagation loss. In addition to the PMC and the nonlinear material, the stimulated THG process can be greatly enhanced by the large pump-harmonic modal overlap. With 1 W pump power, simulation results present that THG conversion efficiency up to 2.79 × 10(-4) within 4.5 ����m MHM can be achieved.

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

    Energy Technology Data Exchange (ETDEWEB)

    Boomadevi, Shanmugam, E-mail: sboomi@gmail.com [Department of Physics, Periyar Maniammai University, Thanjavur-613 403, Tamil Nadu (India); Pandiyan, Krishnamoorthy [School of Electrical and Electronics Engineering, SASTRA University, Thanjavur-613 401, Tamil Nadu (India)

    2014-01-01

    Single crystals of L-alanine of dimensions 2×1.1×0.5 cm{sup 3} 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.

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

    Science.gov (United States)

    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.

  7. High orbital angular momentum harmonic generation

    CERN Document Server

    Vieira, J; Alves, E P; Fonseca, R A; Mendonça, J T; Bingham, R; Norreys, P; Silva, L O

    2016-01-01

    We identify and explore a high orbital angular momentum (OAM) harmonics generation and amplification mechanism that manipulates the OAM independently of any other laser property, by preserving the initial laser wavelength, through stimulated Raman backscattering in a plasma. The high OAM harmonics spectra can extend at least up to the limiting value imposed by the paraxial approximation. We show with theory and particle-in-cell simulations that the orders of the OAM harmonics can be tuned according to a selection rule that depends on the initial OAM of the interacting waves. We illustrate the high OAM harmonics generation in a plasma using several examples including the generation of prime OAM harmonics. The process can also be realised in any nonlinear optical Kerr media supporting three-wave interactions.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1999-08-24

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

  9. Fluorescent DNA probes at liquid/liquid interfaces studied by surface second harmonic generation.

    Science.gov (United States)

    Licari, Giuseppe; Brevet, Pierre-François; Vauthey, Eric

    2016-01-28

    The properties of a series of oxazole yellow dyes, including the dicationic YOPRO-1 and its homodimeric parent YOYO-1 and two monocationic dyes (YOSAC-1 and YOSAC-3), have been investigated at the dodecane/water interface using stationary and time-resolved surface second harmonic generation (SSHG) combined with quantum chemical calculations. Whereas YOYO-1 exists predominantly as a H-dimer in aqueous solution, the stationary SSHG spectra reveal that such dimers are not formed at the interface. No significant H-aggregation was observed with YOPRO-1, neither in solution nor at the interface. In the case of the monocationic YOSAC dyes, a distinct SSHG band due to H-aggregates was measured at the interface, whereas only weak aggregation was found in solution. These distinct aggregation behaviors can be explained by the different orientations of the dyes at the interface, as revealed from the analysis of polarization-resolved experiments, the doubly-charged dyes lying more flat on the interface than the singly charged ones. Although YOYO-1 and YOPRO-1 do not form H-dimer/aggregates at the interface, time-resolved SSHG measurements point to the occurrence of intra- and intermolecular interactions, respectively, which inhibit the ultrafast non-radiative decay of the excited dyes via large amplitude motion, and lead to a nanosecond excited-state lifetime. The distinct behavior evidenced here for YOYO-1 and YOSAC dyes points to their potential use as fluorescent or SHG interfacial probes.

  10. Harmonic Generation by Microwave-frequency Microplasma

    Science.gov (United States)

    Parsons, Stephen; Hoskinson, Alan; Hopwood, Jeffrey

    2013-09-01

    A microplasma may operate as a nonlinear circuit element and generate power at the harmonics of the drive frequency. As an example, microplasma is sustained using 1 W of power at 1.3 GHz in a small discharge gap formed in a split-ring resonator. A probe extends into the microplasma and extracts the 3rd harmonic power through a tuned resonator at 3.9 GHz. The experimental data show that this non-optimized system produces a +38 dB increase in 3rd harmonic power in the presence of a microplasma. Two origins of nonlinearity are described: the harmonic conduction current due to electron collection by microelectrodes, and the harmonic displacement current due to the voltage-dependent sheath capacitance. PIC-MC simulations suggest that the microplasma nonlinearity may also be exploited at frequencies of 100 GHz. Support was provided by the DARPA Microscale Plasma Devices program under award FA9550-12-1-0006.

  11. High harmonic generation from axial chiral molecules.

    Science.gov (United States)

    Wang, Dian; Zhu, Xiaosong; Liu, Xi; Li, Liang; Zhang, Xiaofan; Lan, Pengfei; Lu, Peixiang

    2017-09-18

    Axial chiral molecules, whose stereogenic element is an axis rather than a chiral center, have attracted widespread interest due to their important application, such as asymmetric synthesis and chirality transfer. We investigate high harmonic generation from axial chiral molecules with bichromatic counterrotating circularly polarized laser fields. High harmonic generation from three typical molecules: (Sa)-3-chloropropa-1,2-dien-1-ol, propadiene, and (Ra)-2,3-pentadiene is simulated with time-dependent density-functional theory and strong field approximation. We found that harmonic spectra for 3D oriented axial chiral molecules exhibit obvious circular dichroism. However, the circular dichroism of High harmonic generation from an achiral molecule is much trivial. Moreover, the dichroism of high harmonic generation still exists when axial chiral molecules are 1D oriented,such as (Sa) -3-chloropropa-1,2-dien-1-ol. For a special form of axial chiral molecules with the formula abC=C=Cab (a, b are different substituents), like (Ra)-2,3-pentadiene, the dichroism discriminations disappear when the molecules are only in 1D orientation. The circular dichroism of high harmonic generation from axial chiral molecules is well explained by the trajectory analysis based on the semiclassical three-step mechanism.

  12. Full quantum trajectories resolved high-order harmonic generation.

    Science.gov (United States)

    Ye, Peng; He, Xinkui; Teng, Hao; Zhan, Minjie; Zhong, Shiyang; Zhang, Wei; Wang, Lifeng; Wei, Zhiyi

    2014-08-15

    We use a carrier-envelope-phase stabilized sub-2-cycle laser pulse to generate high-order harmonics and study how the two-dimensional spectrum of harmonics, with the resolutions in temporal frequency and spatial frequency, is shaped by the laser phase. An arrowlike spectrum obtained experimentally when the gas cell is located in front of the laser focus point shows a resolution of full quantum trajectories; i.e., harmonics from different trajectories stand on different positions in this spectrum. In particular, due to the laser phase combined with the classical-like action, the harmonics from short and long trajectories differ maximally in their curvatures of wave fronts in the generation area, and so occupy very different ranges of spatial frequency at the far field. The result directly gives a full map of quantum trajectories in high-order harmonic generation. The conclusion is supported by an analytical model and quantum mechanics simulations.

  13. Optical Third-Harmonic Generation in Graphene

    Directory of Open Access Journals (Sweden)

    Sung-Young Hong

    2013-06-01

    Full Text Available We report strong third-harmonic generation in monolayer graphene grown by chemical vapor deposition and transferred to an amorphous silica (glass substrate; the photon energy is in three-photon resonance with the exciton-shifted van Hove singularity at the M point of graphene. The polarization selection rules are derived and experimentally verified. In addition, our polarization- and azimuthal-rotation-dependent third-harmonic-generation measurements reveal in-plane isotropy as well as anisotropy between the in-plane and out-of-plane nonlinear optical responses of graphene. Since the third-harmonic signal exceeds that from bulk glass by more than 2 orders of magnitude, the signal contrast permits background-free scanning of graphene and provides insight into the structural properties of graphene.

  14. Microwave harmonic generation and nonlinearity in microplasmas

    Science.gov (United States)

    Gregório, José; Parsons, Stephen; Hopwood, Jeffrey

    2016-06-01

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

  15. SEVENTH HARMONIC 20 GHz CO-GENERATOR

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay L

    2014-04-08

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

  16. Harmonic analysis of Doubly Fed Induction Generators

    DEFF Research Database (Denmark)

    Lindholm, Morten; Rasmussen, Tonny Wederberg

    2003-01-01

    This paper gives an overview of the frequency spectrum of the stator and rotor currents in a doubly fed induction generator (DFIG) used in wind power applications. The paper also presents a method to eliminate higher harmonics and interharmonics in the DFIG stator current. The method is implemented...

  17. Using Second Harmonic Generation Microscopy to Study the Three-Dimensional Structure of Collagen and its Degradation Mechanism

    Science.gov (United States)

    Mega, Yair

    Collagen is one of the most abundant proteins found in the human body. Its crystalline structure possesses no centrosymmetry, allowing it to emit second-harmonic waves. Second harmonic generation (SHG) microscopy utilizes the latter quality to produce high-resolution images of collagen rich tissues and therefore become a key research tool in the biomedical field. We developed a new model, intended to be used together with second harmonic generation (SHG) microscopy, to thoroughly investigate collagen-based tissues. We use our SHG model to reveal information in real time from enzymatic biochemical processes. We also present a novel method used to measure quantitatively the direction of the fibers within the tissue, from SHG images. Using this method, we were able to reconstruct an angular map of the orientation of collagen fibers from multiple sections across the entire area of a human cornea. The structure we obtained demonstrates the criss-crossing structure of the human cornea, previously suggested in the literature. In addition, we also report work on a unique step-wise three-photon fluorescence excitation discovered in melanin. This unique fluorescence mechanism was exploited to discriminate melanin on a small-size, low-cost and low laser power setup which was used as a prototype for a handheld device. The latter study is a part of a larger on-going effort in our group to explore new diagnosis methods to be used for early skin cancer screening. Finally, this work demonstrates a spectroscopy-based method to correct for blood vessel thickness effect. The method analyzes spectral shift from a molecular imaging agent and correlate the shifts to the length of the optical path in blood. The correction method described in this work is intended to be implemented on a guided catheter near infrared fluorescence (NIRF) intra-vascular imaging system. In this imaging system, this study's results will used to correct for the radial distance between the imaging tip of the

  18. Nonlinear harmonic generation in distributed optical klystrons

    CERN Document Server

    Freund, H P

    2001-01-01

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

  19. Harmonic sums and polylogarithms generated by cyclotomic polynomials

    Energy Technology Data Exchange (ETDEWEB)

    Ablinger, Jakob; Schneider, Carsten [Johannes Kepler Univ., Linz (Austria). Research Inst. for Symbolic Computation; Bluemlein, Johannes [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)

    2011-05-15

    The computation of Feynman integrals in massive higher order perturbative calculations in renormalizable Quantum Field Theories requires extensions of multiply nested harmonic sums, which can be generated as real representations by Mellin transforms of Poincare-iterated integrals including denominators of higher cyclotomic polynomials. We derive the cyclotomic harmonic polylogarithms and harmonic sums and study their algebraic and structural relations. The analytic continuation of cyclotomic harmonic sums to complex values of N is performed using analytic representations. We also consider special values of the cyclotomic harmonic polylogarithms at argument x=1, resp., for the cyclotomic harmonic sums at N{yields}{infinity}, which are related to colored multiple zeta values, deriving various of their relations, based on the stuffle and shuffle algebras and three multiple argument relations. We also consider infinite generalized nested harmonic sums at roots of unity which are related to the infinite cyclotomic harmonic sums. Basis representations are derived for weight w=1,2 sums up to cyclotomy l=20. (orig.)

  20. Noble Gas Clusters and Nanoplasmas in High Harmonic Generation

    CERN Document Server

    Aladi, M; Rácz, P; Földes, I B

    2015-01-01

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

  1. Generation of higher harmonic internal waves by oscillating spheroids

    Science.gov (United States)

    Shmakova, Natalia; Ermanyuk, Evgeny; Flór, Jan-Bert

    2017-11-01

    Oscillating bodies in stratified fluids may emit higher harmonics in addition to fundamental waves. In the present experimental study, we consider higher harmonics of an internal wave field generated by a horizontally oscillating spheroid in a linearly stratified fluid for moderate to high oscillation amplitudes, i.e., scaled oscillation amplitude A /a ≥0.5 , with a the minor radius of the spheroid. Three different spheroid shapes are tested. The results are discussed in the context of the different theories on the generation of higher harmonics. Higher harmonics are observed at the intersections of fundamental wave beams, and at the critical points of the topography where the topographic slope equals the wave slope. The velocity amplitudes of the fundamental, second, and third harmonic waves grow respectively linearly, quadratically, and with the third power of the scaled oscillation amplitude A /a . Though these amplitudes are generally higher when the object's slope is larger, the increase in amplitude above and below the axisymmetric oscillating objects is found to be due to the effect of focusing. In order to discern the relative importance of the harmonics to the fundamental wave, the horizontal structure of the wave amplitude is measured. The results suggest that the n th harmonic of the internal wave field is associated with a radiation diagram corresponding to a multipole of order 2n, with 2 n directions of propagation.

  2. Spatial mode discrimination using second harmonic generation

    DEFF Research Database (Denmark)

    Delaubert, Vincent; Lassen, Mikael Østergaard; Pulford, David

    2007-01-01

    -Kleinmann analysis, taking into account the full description of the multi-mode field inside the nonlinear crystal in a type I phase-maching condition. The good agreement between experiments and theory shows that the effect is well understood and that we have reliable models required for the design of novel photonics......Second harmonic generation can be used as a technique for controlling the spatial mode structure of optical beams. We demonstrate experimentally the generation of higher order spatial modes, and that it is possible to use nonlinear phase matching as a predictable and robust technique...... for the conversion of transverse electric modes of the second harmonic output. For a given TEMn0 pump mode the output mode can be altered continuously by adjusting the laser wavelength, the focusing of the pump or the temperature of the nonlinear medium. We make quantitative comparisons with a generalized Boyd...

  3. High-order harmonic generation in laser plasma plumes

    CERN Document Server

    Ganeev, Rashid A

    2013-01-01

    This book represents the first comprehensive treatment of high-order harmonic generation in laser-produced plumes, covering the principles, past and present experimental status and important applications. It shows how this method of frequency conversion of laser radiation towards the extreme ultraviolet range matured over the course of multiple studies and demonstrated new approaches in the generation of strong coherent short-wavelength radiation for various applications. Significant discoveries and pioneering contributions of researchers in this field carried out in various laser scientific centers worldwide are included in this first attempt to describe the important findings in this area of nonlinear spectroscopy. "High-Order Harmonic Generation in Laser Plasma Plumes" is a self-contained and unified review of the most recent achievements in the field, such as the application of clusters (fullerenes, nanoparticles, nanotubes) for efficient harmonic generation of ultrashort laser pulses in cluster-containin...

  4. Second Harmonic Generation in Subdiffractive Two-Dimensional Photonic Crystals

    CERN Document Server

    Nistor, Cristian

    2013-01-01

    The PhD thesis is devoted to the study of second harmonic generation of narrow beams in photonic crystals. The basic idea is that if both frequencies, the fundamental and second harmonics are in the region of self-collimation, then the second harmonics of narrow beams can be very efficient. The beams do not spread diffractively during propagation and interaction. The phase matching is ensured for all components of the interacting beams. This allows to enhance the nonlinear interaction efficiency several times. The thesis rewises the theory of self-collimation of narrow beams in photonic crystals, and presents the theory of second harmonics in photonic crystals. Calculations in photonic crystals of different configurations are presented, and the recommendations to experimental realisations are given.

  5. Strong nonlinear harmonic generation in a PZT/Aluminum resonator

    Science.gov (United States)

    Parenthoine, D.; Haumesser, L.; Vander Meulen, F.; Tran-Huu-Hue, L.-P.

    2009-11-01

    In this work, the extentional vibration mode of a coupled PZT/ Aluminum rod resonator is studied experimentally. Geometrical characteristics of the PZT are its 27 mm length and its 4×4 mm2 cross section area. The excitation voltage consists in sinusoidal bursts in the frequency range (20-80 kHz). Velocity measurements are performed at both ends of this system, using a laser probe. Strong harmonic distortions in the mechanical response (up to -20 dB with respect to the primary wave amplitude) have been observed. The corresponding input levels are far lower than those which are necessary to observe quadratic second harmonic generation in a free PZT resonator. The strong nonlinear effect can be explained as a super-harmonic resonance of the system due to a specific ratio between the eigen frequencies of the two parts of the resonator. Evolution of fundamental and harmonic responses are observed as a function of input levels, highlighting hysteretic behavior.

  6. Comparative study of nonideal beam effects in high gain harmonic generation and self-seeded free electron lasers

    Directory of Open Access Journals (Sweden)

    Agostino Marinelli

    2010-07-01

    Full Text Available In this paper we investigate and compare the properties of two narrow-bandwidth free-electron laser (FEL schemes, one using self-seeding and the other high gain harmonic generation (HGHG. The two systems have been thoroughly studied analytically and numerically in the past. The aim of this work is to compare their performances when the FEL is driven by an electron beam with nonideal properties, thus including effects such as shot-to-shot energy fluctuations and nonlinear energy chirp. In both cases nonlinearities produce a bandwidth larger than the Fourier transform limited value. However, our analysis indicates that, for approximately the same output power levels, the self-seeding scheme is less affected than the HGHG scheme by quadratic energy chirps in the electron beam longitudinal phase space. This is confirmed by a specific numerical example corresponding to SPARX parameters where the electron beam was optimized to minimize the FEL gain length. The work has been carried out with the aid of the time dependent FEL codes GENESIS 1.3 (3D and PERSEO (1D.

  7. Second Harmonic Generation Studies of Fe(II) Interactions with Hematite (α-Fe2O3)

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, David S.; Hull, Christopher J.; Troiano, Julianne M.; Riha, Shannon C.; Martinson, Alex B.; Rosso, Kevin M.; Geiger, Franz M.

    2013-02-28

    Iron oxides are a ubiquitous class of compounds that are involved in many biological, geological, and technological processes, and the Fe(III)/Fe(II) redox couple is a fundamental transformation pathway; however, the study of iron oxide surfaces in aqueous solution by powerful spectroscopic techniques has been limited due to "strong absorber problem". In this work, atomic layer deposition (ALD) thin films of polycrystalline alpha-Fe2O3 were analyzed using the Eisenthal chi((3)) technique, a variant of second harmonic generation that reports on interfacial potentials. By determining the surface charge densities at multiple pH values, the point of zero charge was found to be 5.5 +/- 0.3. The interaction of aqueous Fe(II) at pH 4 and in 1 mM NaCl with ALD-prepared hematite was found to be fully reversible and to lead to about 4 times more ferrous iron ions adsorbed per square centimeter than on fused-silica surfaces under the same conditions. The data are consistent with a recently proposed conceptual model for net Fe(II) uptake or release that is underlain by a dynamic equilibrium between Fe(II) adsorbed onto hematite, electron transfer into favorable surface sites with attendant Fe(III) deposition, and electron conduction to favorable remote sites that release and replenish aqueous Fe(II).

  8. Study of all-polymer-based waveguide resonant gratings and their applications for optimization of second-harmonic generation

    Science.gov (United States)

    Hoang Luong, Mai; Thanh Ngan Nguyen, Thi; Thanh Nguyen, Chi; Ledoux-Rak, Isabelle; Diep Lai, Ngoc

    2015-09-01

    We investigated theoretically and experimentally the optical properties of all-polymer-based one-dimensional waveguide resonant gratings (WRGs) and their important applications for the optimization of second-harmonic generation (SHG). We first studied the basic theory of the resonant modes of a simple grating-coupled waveguide realized on a material possessing a low refractive index contrast. The optical properties of any WRG were numerically simulated by using the finite-difference time domain method, performed by commercial Lumerical software. The polymer-based surface relief gratings were fabricated on azopolymer Disperse Red 1-Poly-Methyl-Methacrylate (DR1-PMMA) thin films by using the two-beam interference method and mass transport effect. Their experimental reflection spectra measured as a function of incident light wavelength are in good agreement with the theoretical predictions. We then demonstrated a first application of such a polymer-based WRG for nonlinear optics. Thanks to the strong local electrical field in the WRG, due to a guided-mode resonance condition, the SHG signal of an infrared light beam was strongly enhanced by a factor of 25 as compared to the result obtained in a sample without a grating.

  9. Second-harmonic generation in noncentrosymmetric phosphates

    Science.gov (United States)

    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.

  10. High-order harmonic generation from eld-distorted orbitals

    DEFF Research Database (Denmark)

    Spiewanowski, Maciek; Etches, Adam; Madsen, Lars Bojer

    We investigate the eect on high-order harmonic generation of the distortion of molecular orbitals by the driving laser eld. Calculations for high-order harmonic generation including orbital distortion are performed for N2 (high polarizability). Our results allow us to suggest that field...... of the minimum in the high-order harmonic spectra. This is in agreement with experiment....

  11. Coherent intensity fluctuation model for autocorrelation imaging spectroscopy with higher harmonic generating point scatterers-a comprehensive theoretical study.

    Science.gov (United States)

    Slenders, Eli; vandeVen, Martin; Hooyberghs, Jef; Ameloot, Marcel

    2015-07-15

    We present a general analytical model for the intensity fluctuation autocorrelation function for second and third harmonic generating point scatterers. Expressions are derived for a stationary laser beam and for scanning beam configurations for specific correlation methodologies. We discuss free translational diffusion in both three and two dimensions. At low particle concentrations, the expressions for fluorescence are retrieved, while at high particle concentrations a rescaling of the function parameters is required for a stationary illumination beam, provided that the phase shift per unit length of the beam equals zero.

  12. Promoting Spontaneous Second Harmonic Generation through Organogelation.

    Science.gov (United States)

    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.

  13. Glass devices for efficient second harmonic generation

    DEFF Research Database (Denmark)

    Fage-Pedersen, Jacob; Jacobsen, Rune Shim; Kristensen, Martin

    2005-01-01

    We show here that quasi-phase matched (QPM) planar nonlinear devices of high quality can be fabricated by means of periodic poling of the glass. The devices, used for second-harmonic generation (SHG), have accurately-controlled centre wavelengths, and the normalised conversion efficiencies...... are approximately one order of magnitude higher than what has previously been reported for periodically poled glass. In conclusion, we have demonstrated that high-quality nonlinear QPM devices can be fabricated in glass-on-silicon. The technology is easily adaptable to any desired wavelength (e.g. 1550 nm) and can...

  14. Second harmonic generation in resonant optical structures

    Energy Technology Data Exchange (ETDEWEB)

    Eichenfield, Matt; Moore, Jeremy; Friedmann, Thomas A.; Olsson, Roy H.; Wiwi, Michael; Padilla, Camille; Douglas, James Kenneth; Hattar, Khalid Mikhiel

    2018-01-09

    An optical second-harmonic generator (or spontaneous parametric down-converter) includes a microresonator formed of a nonlinear optical medium. The microresonator supports at least two modes that can be phase matched at different frequencies so that light can be converted between them: A first resonant mode having substantially radial polarization and a second resonant mode having substantially vertical polarization. The first and second modes have the same radial order. The thickness of the nonlinear medium is less than one-half the pump wavelength within the medium.

  15. Effect of undulator harmonics field on free-electron laser harmonic generation

    Directory of Open Access Journals (Sweden)

    Qika Jia

    2011-06-01

    Full Text Available The harmonics field effect of a planar undulator on free-electron laser (FEL harmonic generation has been analyzed. For both the linear case and the nonlinear case, the harmonic fraction of the radiation can be characterized by the coupling coefficients. The modification of the coupling coefficients is given when the third harmonics magnetic field component exists, thus the enhancement of the harmonic radiation can be predicted. The numerical results show that with the third harmonics magnetic field component that has the opposite sign to the fundamental, the intensity of third-harmonic radiation can be increased distinctly for both the small signal gain and the nonlinear harmonic generation. The increase is larger for the smaller undulator deflecting parameter.

  16. Probing energetics with second harmonic generation

    Science.gov (United States)

    Konek, Christopher; Mason, Brian; Stoltz, Chad; Gump, Jared; Wilkinson, John

    2009-06-01

    We focus on the insensitive high explosive 1,3,5-triamino-2,4,6- trinitrobenzene (TATB) with the goal of obtaining structural information as a function of pressure and temperature. Prior experiments from Los Alamos (Son et al. J. Phys. Chem. B. 1999, 103 (26) 5434) demonstrated that in high temperature environments (approaching 300^o C) TATB increases in efficiency as a nonlinear optical medium, possibly undergoing structural changes which alter the crystal symmetry. We use the nonlinear optical technique second harmonic generation (SHG) to probe TATB in a diamond anvil cell experimental setup to perform measurements at high pressure. Additionally, by exploiting the electronic absorption features of TATB to perform resonantly enhanced second harmonic generation (RE-SHG) experiments, we probe the electronic transitions in the visible range as a function of pressure and temperature, to observe electronic changes that would occur. Polarization resolved SHG experiments allow further insight into changes in crystal structure. These static measurements may have implications for shocked TATB.

  17. Spontaneous Polarization in Bio-organic Materials Studied by Scanning Pyroelectric Microscopy (SPEM) and Second Harmonic Generation Microscopy (SHGM)

    Science.gov (United States)

    Putzeys, T.; Wübbenhorst, M.; van der Veen, M. A.

    2015-06-01

    Bio-organic materials such as bones, teeth, and tendon generally show nonlinear optical (Masters and So in Handbook of Biomedical Nonlinear Optical Microscopy, 2008), pyro- and piezoelectric (Fukada and Yasuda in J Phys Soc Jpn 12:1158, 1957) properties, implying a permanent polarization, the presence of which can be rationalized by describing the growth of the sample and the creation of a polar axis according to Markov's theory of stochastic processes (Hulliger in Biophys J 84:3501, 2003; Batagiannis et al. in Curr Opin Solid State Mater Sci 17:107, 2010). Two proven, versatile techniques for probing spontaneous polarization distributions in solids are scanning pyroelectric microscopy (SPEM) and second harmonic generation microscopy (SHGM). The combination of pyroelectric scanning with SHG-microscopy in a single experimental setup leading to complementary pyroelectric and nonlinear optical data is demonstrated, providing us with a more complete image of the polarization in organic materials. Crystals consisting of a known polar and hyperpolarizable material, CNS (4-chloro-4-nitrostilbene) are used as a reference sample, to verify the functionality of the setup, with both SPEM and SHGM images revealing the same polarization domain information. In contrast, feline and human nails exhibit a pyroelectric response, but a second harmonic response is absent for both keratin containing materials, implying that there may be symmetry-allowed SHG, but with very inefficient second harmonophores. This new approach to polarity detection provides additional information on the polar and hyperpolar nature in a variety of (bio) materials.

  18. Enhanced third harmonic generation with graphene metasurfaces

    Science.gov (United States)

    Jin, Boyuan; Guo, Tianjing; Argyropoulos, Christos

    2017-09-01

    The nonlinear responses of different materials provide useful mechanisms for optical switching, low noise amplification, and harmonic frequency generation. However, the nonlinear processes usually have an extremely weak nature and require high input power to be excited. To alleviate this severe limitation, we propose new designs of ultrathin nonlinear metasurfaces composed of patterned graphene micro-ribbons to significantly enhance third harmonic generation (THG) at far-infrared and terahertz (THz) frequencies. The incident wave is tightly confined and significantly boosted along the surface of graphene in these configurations due to the excitation of highly localized plasmons. The bandwidth of the resonant response becomes narrower due to the introduction of a metallic substrate below the graphene micro-ribbons, which leads to zero transmission and standing waves inside the intermediate dielectric spacer layer. The enhancement of the incident field, combined with the large nonlinear conductivity of graphene, can dramatically increase the THG conversion efficiency by several orders of magnitude. In addition, the resonant frequency of the metasurface can be adjusted by dynamically tuning the Fermi energy of graphene via electrical or chemical doping. As a result, the THG wave can be optimized and tuned to be emitted at different frequencies without the need to change the nonlinear metasurface geometry. The proposed nonlinear metasurfaces provide a new way to realize compact and efficient nonlinear sources at the far-infrared and THz frequency ranges, as well as new frequency generation and wave mixing devices which are expected to be useful for nonlinear THz spectroscopy and noninvasive THz imaging applications.

  19. Plasma harmonics

    CERN Document Server

    Ganeev, Rashid A

    2014-01-01

    Preface; Why plasma harmonics? A very brief introduction Early stage of plasma harmonic studies - hopes and frustrations New developments in plasma harmonics studies: first successes Improvements of plasma harmonics; Theoretical basics of plasma harmonics; Basics of HHG Harmonic generation in fullerenes using few-cycle pulsesVarious approaches for description of observed peculiarities of resonant enhancement of a single harmonic in laser plasmaTwo-colour pump resonance-induced enhancement of odd and even harmonics from a tin plasmaCalculations of single harmonic generation from Mn plasma;Low-o

  20. Second Harmonic Generation of Unpolarized Light

    Science.gov (United States)

    Ding, Changqin; Ulcickas, James R. W.; Deng, Fengyuan; Simpson, Garth J.

    2017-11-01

    A Mueller tensor mathematical framework was applied for predicting and interpreting the second harmonic generation (SHG) produced with an unpolarized fundamental beam. In deep tissue imaging through SHG and multiphoton fluorescence, partial or complete depolarization of the incident light complicates polarization analysis. The proposed framework has the distinct advantage of seamlessly merging the purely polarized theory based on the Jones or Cartesian susceptibility tensors with a more general Mueller tensor framework capable of handling partial depolarized fundamental and/or SHG produced. The predictions of the model are in excellent agreement with experimental measurements of z -cut quartz and mouse tail tendon obtained with polarized and depolarized incident light. The polarization-dependent SHG produced with unpolarized fundamental allowed determination of collagen fiber orientation in agreement with orthogonal methods based on image analysis. This method has the distinct advantage of being immune to birefringence or depolarization of the fundamental beam for structural analysis of tissues.

  1. High-order harmonic generation via multicolor beam superposition

    Science.gov (United States)

    Sarikhani, S.; Batebi, S.

    2017-09-01

    In this article, femtosecond pulses, especially designed by multicolor beam superposition are used for high-order harmonic generation. To achieve this purpose, the spectral difference between the beams, and their width are taken to be small values, i.e., less than 1 nm. Applying a Gaussian distribution to the beam intensities leads to a more distinct pulses. Also, it is seen that these pulses have an intrinsic linear chirp. By changing the width of the Gaussian distributions, we can have several pulses with different bandwidths and hence various pulse duration. Thus, the study of these broadband pulse influences, in contrast with monochromatic pulses, on the atomic or molecular targets was achievable. So, we studied numerically the effect of these femtosecond pulses on behavior of the high-order harmonics generated after interaction between the pulse and the atomic hydrogen. For this study, we adjusted the beam intensities so that the produced pulse intensity be in the over-barrier ionization region. This makes the power spectrum of high-order harmonics more extensive. Cutoff frequency of the power spectrum along with the first harmonic intensity and its shift from the incident pulse are investigated. Additionally, maximum ionization probability with respect to the pulse bandwidth was also studied.

  2. High order harmonic generation with femtosecond mid-infrared laser

    Science.gov (United States)

    Lin, Jinpu; Nees, John; Krushelnick, Karl; Dollar, Franklin; Nguyen, Tam

    2017-10-01

    There has been growing interest in high order harmonic generation (HHG) from laser-solid interactions as a compact source of coherent x-rays. The ponderomotive potential in laser-plasma interactions increases with longer laser wavelength, so there may be significant differences in the physics of harmonic generation and other phenomena when experiments are conducted with mid-infrared lasers. Previous experiments, however, have been done almost exclusively with near-infrared lasers. In this work, we report the results of experiments performed with millijoule, 40 fs, 2 µm laser pulses generated by an optical parametric amplifier (OPA) which are focused onto solid targets such as silicon and glass. The HHG efficiency, polarization dependence, and x-ray emission are studied and compared to measurements with near-infrared lasers. Funded by AFOSR MURI.

  3. OPTICAL SECOND-HARMONIC GENERATION IN CRYSTALLINE AMINO ACIDS.

    Science.gov (United States)

    RIECKHOFF, K E; PETICOLAS, W L

    1965-02-05

    Optically active amino acids contain many highly efficient optical second-harmonic generators. When light from a ruby laser at 6943 A falls on the crystalline amino acids with sufficient intensity, the second harmonic of the light at 3471 A can be observed. Although the symmetry requirements for optical second-harmonic generation are always met by isomerically pure optically active substances, there is considerable variation in efficiency for the generation of the second harmonic, ranging from almost zero to greater than that of potassium dihydrogen phosphate, the most efficient known.

  4. High-order-harmonic generation from field-distorted orbitals

    DEFF Research Database (Denmark)

    Spiewanowski, Maciek; Etches, Adam; Madsen, Lars Bojer

    2013-01-01

    We investigate the effect on high-order-harmonic generation of the distortion of molecular orbitals by the driving laser field. Calculations for high-order-harmonic generation including orbital distortion are performed for N2. Our results allow us to suggest that field distortion is the reason why...

  5. Density-Matrix Renormalization Group Study of Third Harmonic Generation in One-Dimensional Mott Insulator Coupled with Phonon

    Science.gov (United States)

    Sota, Shigetoshi; Yunoki, Seiji; Tohyama, Takami

    2015-05-01

    We examine the third-order non-linear optical response of a one-dimensional Mott insulator coupled with phonons. The Mott insulator is described by an extended Hubbard-Holstein model. The third harmonic generation (THG) of the model is calculated by dynamical density-matrix renormalization group. We find that the electron-phonon interaction enhances the intensity of THG if the on-site Coulomb interaction is comparable to the band width, but the enhancement is small for a realistic parameter value of a typical Mott insulator Sr2CuO3. The low-energy spin excitation does not contribute to the optical response if the electron-phonon coupling is neglected. We find that the THG spectrum can detect the spin excitations even for no electron-phonon coupling. The introduction of the electron-phonon coupling leads to a slight increase of low-energy weight in THG without peak structure through phonon-assisted spin excitation. To fully understand the phonon-assisted spin excitation, we additionally calculate the linear susceptibility of a doped Hubbard-Holstein model, showing a spectral distribution different from that at half filling.

  6. Second harmonic generation from the `centrosymmetric' crystals

    Directory of Open Access Journals (Sweden)

    Venkatram Nalla

    2015-05-01

    Full Text Available 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.

  7. Improved Efficiency Type II Second Harmonic Generation

    Science.gov (United States)

    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.

  8. Strong nonlinear harmonic generation in a PZT/Aluminum resonator

    Energy Technology Data Exchange (ETDEWEB)

    Parenthoine, D; Haumesser, L; Meulen, F Vander; Tran-Huu-Hue, L-P, E-mail: parenthoine@univ-tours.f [University Francois Rabelais of Tours, U 930 Imagerie et Cerveau, CNRS 2448, ENIVL, rue de la Chocolaterie, BP 3410, 41034 Blois (France)

    2009-11-01

    In this work, the extentional vibration mode of a coupled PZT/ Aluminum rod resonator is studied experimentally. Geometrical characteristics of the PZT are its 27 mm length and its 4x4 mm{sup 2} cross section area. The excitation voltage consists in sinusoidal bursts in the frequency range (20-80 kHz). Velocity measurements are performed at both ends of this system, using a laser probe. Strong harmonic distortions in the mechanical response (up to -20 dB with respect to the primary wave amplitude) have been observed. The corresponding input levels are far lower than those which are necessary to observe quadratic second harmonic generation in a free PZT resonator. The strong nonlinear effect can be explained as a super-harmonic resonance of the system due to a specific ratio between the eigen frequencies of the two parts of the resonator. Evolution of fundamental and harmonic responses are observed as a function of input levels, highlighting hysteretic behavior.

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

    Science.gov (United States)

    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

  10. Study of carrier blocking property of poly-linalyl acetate thin layer by electric-field-induced optical second-harmonic generation measurement

    Science.gov (United States)

    Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa; Anderson, Liam J.; Jacob, Mohan V.

    2014-02-01

    By using electric-field-induced optical second-harmonic generation (EFISHG) measurement, we studied the carrier-blocking property of poly-linalyl acetate (PLA) thin layers sandwiched in indium-zinc-oxide (IZO)/PLA/C60/Al double-layer diodes. Results showed that the PLA layer totally blocks electrons crossing the C60 layer, and also blocks holes entering from the IZO layer. The EFISHG measurement effectively substantiates the hole-blocking electron-blocking property of the PLA layer sandwiched in double layer diodes.

  11. Spectral phase distribution retrieval through coherent control of harmonic generation.

    Science.gov (United States)

    Papalazarou, E; Kovacev, M; Tzallas, P; Benis, E P; Kalpouzos, C; Tsakiris, G D; Charalambidis, D

    2006-04-28

    The temporal intensity distribution of the third harmonic of a Ti:sapphire laser generated in Xe gas is fully reconstructed from its spectral phase and amplitude distributions. The spectral phases are retrieved by cross correlating the fundamental laser frequency field with that of the third harmonic, in a three laser versus one harmonic photon coupling scheme. The third harmonic spectral amplitude distribution is extracted from its field autocorrelation. The measured pulse duration is found to be in agreement with that expected from lowest order perturbation theory both for unstretched and chirped pulses.

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

    NARCIS (Netherlands)

    Goh, S.J.; Tao, Y.; van der Slot, Petrus J.M.; Bastiaens, Hubertus M.J.; Herek, Jennifer Lynn; Biedron, S.G.; Danailov, M.B.; Milton, S.V.; Boller, Klaus J.

    2015-01-01

    For exploring the application potential of coherent soft x-ray (SXR) and extreme ultraviolet radiation (XUV) provided by high-harmonic generation, it is important to characterize the central output parameters. Of specific importance are pulse-to-pulse (shot-to-shot) fluctuations of the high-harmonic

  13. Optical second harmonic generation from Wannier excitons

    DEFF Research Database (Denmark)

    Pedersen, Thomas Garm; Cornean, Horia

    2007-01-01

    , a simplified three-band Wannier exciton model of cubic semiconductors is applied and a closed form expression for the complex second harmonic response function including broadening is derived. Our calculated spectra are found to be in excellent agreement with the measured response near the band edge...

  14. High-order harmonic generation from polar molecules

    DEFF Research Database (Denmark)

    Etches, Adam

    When a molecule is submitted to a very intense laser pulse it emits coherent bursts of light in each optical half-cycle of the laser field. This process is known as high-order harmonic generation because the spectrum consists of many peaks at energies corresponding to an integer amount of laser...... photons. The harmonics contain information about the wave function of the loosest bound electron on an Ångström length scale and attosecond time scale. However, accurate theoretical models are needed in order to extract this information. In this thesis the most widely used model of high-order harmonic...... generation is extended to polar molecules by including the laser-induced Stark shift of each molecular orbitals. The Stark shift is shown to have a major influence on the relative strength of harmonic bursts in neighbouring half-cycles, as well as leaving an imprint on the phase of the harmonics...

  15. Second harmonic generation in Te crystal using free electron laser

    CERN Document Server

    Yamauchi, T; Minehara, E J

    2002-01-01

    The second harmonic generation signal converted from the fundamental wavelength of 22 mu m of a free electron laser was observed for the first time using a birefringent Te crystal. The experimental conversion efficiency of Te crystal for second harmonic generation is 0.53%, which is equivalent to the theoretical value within a factor of 2. The Te crystal has been incorporated into an autocorrelator system to measure the micro-pulse width of infrared free electron laser successfully. (author)

  16. Surface structure enhanced second harmonic generation in organic nanofibers

    DEFF Research Database (Denmark)

    Fiutowski, Jacek; Maibohm, Christian; Kostiucenko, Oksana

    Second-harmonic generation upon femto-second laser irradiation of nonlinearly optically active nanofibers grown from nonsymmetrically functionalized para-quarterphenylene (CNHP4) molecules is investigated. Following growth on mica templates, the nanofibers have been transferred onto lithography......-defined regular arrays of gold square nanostructures. These nanostructure arrays induce local field enhancement, which significantly lowers the threshold for second harmonic generation in the nanofibers....

  17. Layer Tunable Third-Harmonic Generation in Multilayer Black Phosphorus

    CERN Document Server

    Youngblood, Nathan; Nemilentsau, Andrei; Low, Tony; Li, Mo

    2016-01-01

    Black phosphorus has been the subject of growing interest due to its unique band structure that is both layer dependent and anisotropic. While many have studied the linear optical response of black phosphorus, the nonlinear response has remained relatively unexplored. Here we report on the observation of third-harmonic generation in black phosphorus using an ultrafast near-IR laser and measure chi(3) experimentally for the first time. It was found that chi(3) is highly dependent on both the incident polarization and the number of layers present.

  18. The echo-enabled harmonic generation options for FLASH II

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Haixiao [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Shanghai Inst. of Applied Physics (China); Decking, Winfried; Faatz, Bart [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2011-03-15

    FLASH II is an upgrade to the existing free electron laser (FEL) FLASH. The echo-enabled harmonic generation (EEHG) scheme is proposed to be a potential seeding option of FLASH II. In this paper, the possibility of EEHG operation of FLASH II is investigated for the first time. With a combination of existing numerical codes, i.e. a laser-beam interaction code in an undulator (LBICU), a beam tracking code in a chicane (ELEGANT) and an universal FEL simulating code (GENESIS), the effects of beam energy chirp and coherent synchrotron radiation (CSR) on EEHG operation are studied as well. In addition, several interesting issues concerning EEHG simulation are discussed. (orig.)

  19. Polarization gating of high harmonic generation in the water window

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jie; Ren, Xiaoming; Yin, Yanchun; Cheng, Yan; Cunningham, Eric; Wu, Yi; Chang, Zenghu, E-mail: Zenghu.Chang@ucf.edu [Institute for the Frontier of Attosecond Science and Technology, CREOL and Department of Physics, University of Central Florida, Orlando, Florida 32816 (United States)

    2016-06-06

    We implement the polarization gating (PG) technique with a two-cycle, 1.7 μm driving field to generate an attosecond supercontinuum extending to the water window spectral region. The ellipticity dependence of the high harmonic yield over a photon energy range much broader than previous work is measured and compared with a semi-classical model. When PG is applied, the carrier-envelope phase (CEP) is swept to study its influence on the continuum generation. PG with one-cycle (5.7 fs) and two-cycle (11.3 fs) delay are tested, and both give continuous spectra spanning from 50 to 450 eV under certain CEP values, strongly indicating the generation of isolated attosecond pulses in the water window region.

  20. Surface plasmon-enhanced transverse magnetic second-harmonic generation.

    Science.gov (United States)

    Zheng, Wei; Hanbicki, Aubrey T; Jonker, Berry T; Lüpke, Gunter

    2013-11-18

    We present experimental studies on surface plasmon (SP) enhanced transverse magnetic second-harmonic generation (T-MSHG) in single-crystal iron films grown by molecular beam epitaxy at room temperature on MgO (001) substrates. We show that it is possible to achieve both strongly enhanced T-MSHG intensity and high magnetic contrast ratio under attenuated total reflection configuration without using complex heterostructures because MSHG is generated directly at the iron surface where SPs are present. The T-MSHG has a much larger contrast ratio than transverse magneto-optical Kerr effect (T-MOKE) and shows great potential for a new generation of bio-chemical sensors due to its very high surface sensitivity. In addition, by analyzing the experimental results and the simulations based on SP field-enhancement theory, we demonstrate that the second-order susceptibility of MSHG shows great anisotropy and the tensor χ(xzz)(odd) is dominant in our sample.

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

    Science.gov (United States)

    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.

  2. Optical second harmonic generation from Pt nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, N.; Aratake, K.; Okushio, R.; Iwai, T. [Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); Sugawara, A. [Hitachi Advanced Research Laboratory, Akanuma 2520, Hatoyama, Saitama 350-0395 (Japan); Sano, H. [Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); Mizutani, G. [Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan)], E-mail: mizutani@jaist.ac.jp

    2007-09-15

    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 {chi}{sub 222}{sup (2)}, with the suffix 2 indicating the direction [11-bar0], 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.

  3. Internalization of fluorescent dextrans in the submandibular salivary glands of live animals: a study combining intravital two-photon microscopy and second harmonic generation

    Science.gov (United States)

    Masedunskas, Andrius; Weigert, Roberto

    2008-02-01

    Here we show that a combination of two-photon microscopy and second harmonic generation can be successfully used to study endocytosis in the submandibular salivary glands of live animals. First, we have characterized the threedimensional structure of the acini and the ducts forming the parenchyma of the excised glands by exciting various endogenous molecules, which highlight the shape of the cells and various components of the extracellular matrix. Next, by time-lapse imaging we show the dynamic distribution of fluorescent probes injected systemically. This was achieved by using a custom-made holder aimed to reduce the motion artifacts associated with the heartbeat and the respiration in the live animals. Finally, we show that fluorescent dextrans are internalized primarily by the supporting cells in the salivary glands, a characteristic shared by other secretory organs such as the pancreas.

  4. The roles of photo-carrier doping and driving wavelength in high harmonic generation from a semiconductor.

    Science.gov (United States)

    Wang, Zhou; Park, Hyunwook; Lai, Yu Hang; Xu, Junliang; Blaga, Cosmin I; Yang, Fengyuan; Agostini, Pierre; DiMauro, Louis F

    2017-11-22

    High-harmonic generation from gases produces attosecond bursts and enables high-harmonic spectroscopy to explore electron dynamics in atoms and molecules. Recently, high-harmonic generation from solids has been reported, resulting in novel phenomena and unique control of the emission, absent in gas-phase media. Here we investigate high harmonics from semiconductors with controllable induced photo-carrier densities, as well as the driving wavelengths. We demonstrate that the dominant generation mechanism can be identified by monitoring the variation of the harmonic spectra with the carrier density. Moreover, the harmonic spectral dependence on the driving wavelength is reported and a different dependence from the well-known one in gas-phase media is observed. Our study provides distinct control of the harmonic process from semiconductors, sheds light on the underlying mechanism and helps optimize the harmonic properties for future solid-state attosecond light sources.

  5. Spatial properties of odd and even low order harmonics generated in gas.

    Science.gov (United States)

    Lambert, G; Andreev, A; Gautier, J; Giannessi, L; Malka, V; Petralia, A; Sebban, S; Stremoukhov, S; Tissandier, F; Vodungbo, B; Zeitoun, Ph

    2015-01-14

    High harmonic generation in gases is developing rapidly as a soft X-ray femtosecond light-source for applications. This requires control over all the harmonics characteristics and in particular, spatial properties have to be kept very good. In previous literature, measurements have always included several harmonics contrary to applications, especially spectroscopic applications, which usually require a single harmonic. To fill this gap, we present here for the first time a detailed study of completely isolated harmonics. The contribution of the surrounding harmonics has been totally suppressed using interferential filtering which is available for low harmonic orders. In addition, this allows to clearly identify behaviors of standard odd orders from even orders obtained by frequency-mixing of a fundamental laser and of its second harmonic. Comparisons of the spatial intensity profiles, of the spatial coherence and of the wavefront aberration level of 5ω at 160 nm and 6ω at 135 nm have then been performed. We have established that the fundamental laser beam aberrations can cause the appearance of a non-homogenous donut-shape in the 6ω spatial intensity distribution. This undesirable effect can be easily controlled. We finally conclude that the spatial quality of an even harmonic can be as excellent as in standard generation.

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

    DEFF Research Database (Denmark)

    Bache, Morten; Bang, Ole; Zhou, Binbin

    2010-01-01

    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. ...

  7. Enhanced high-order harmonic generation from Argon-clusters

    NARCIS (Netherlands)

    Tao, Yin; Hagmeijer, Rob; Bastiaens, Hubertus M.J.; Goh, S.J.; van der Slot, P.J.M.; Biedron, S.; Milton, S.; Boller, Klaus J.

    2017-01-01

    High-order harmonic generation (HHG) in clusters is of high promise because clusters appear to offer an increased optical nonlinearity. We experimentally investigate HHG from Argon clusters in a supersonic gas jet that can generate monomer-cluster mixtures with varying atomic number density and

  8. General Theory of Harmonics Generation thru Energy Transformation

    Science.gov (United States)

    Czyzyk, Don

    2013-04-01

    Energy, whatever its form, can be converted into an electrical signal. When analyzed is found to be comprised of a continuum of sinusoidal frequencies called a harmonic spectrum H/S. This paper addresses the question of how/why, in general, are these sinusoidal frequencies (harmonics) generated and in particular how they are produced in electronic circuits. To address this question many varied experiments were performed. Some experiments used just batteries while others used mechanical, acoustic, pneumatic, thermal, magnetic, hydraulic or photonic devices. All these devices were used to investigate the nature of harmonic generation from the perspective of the en masse movement of conduction electrons. Primarily performing electronic experiments on the envelope of a single pulse revealed that a pulse of one wavelength can be separated into basic individual segments. The energy of each individual segment, when absorbed by conduction electrons, is transformed into a unique H/S. Recombining all the individual segments that comprise a pulse envelope, involves the constructive or destructive interactions of their harmonic spectrums leading to the amplitudes of some harmonics being increased and others reduced or eliminated. The result is a pulse envelope with a different harmonic series.

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

    Science.gov (United States)

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

    2015-09-21

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

  10. Harmonic Generation in a Traveling-Wave Tube

    Science.gov (United States)

    Wong, Patrick; Zhang, Peng; Lau, Y. Y.; Greening, Geoffrey; Gilgenbach, Ronald; Chernin, David; Simon, David; Hoff, Brad

    2016-10-01

    Crowding of electron orbits in a traveling-wave tube (TWT) may lead to significant harmonic contents in the beam current, even in the linear regime. Here, we consider a wideband TWT that exhibits gain at the second harmonic. We analytically formulate equations governing the evolution of the generation of second harmonic, including axial variations of the Pierce parameters. The second harmonic output is phase-controlled by the input signal which consists only of a fundamental frequency. Several test cases are performed and compared with simulation using the CHRISTINE code. Reasonable agreement between theory and simulation is found. Work supported by AFOSR FA9550-15-1-0097, ONR N00014-16-1-2353, and L-3 Communications Electron Device Division.

  11. Avalanche effect and gain saturation in high harmonic generation

    CERN Document Server

    Serrat, Carles; Budesca, Josep M; Seres, Jozsef; Seres, Enikoe; Aurand, Bastian; Hoffmann, Andreas; Namba, Shinichi; Kuehl, Thomas; Spielmann, Christian

    2015-01-01

    Optical amplifiers in all ranges of the electromagnetic spectrum exhibit two essential characteristics: i) the input signal during the propagation in the medium is multiplied by the avalanche effect of the stimulated emission to produce exponential growth and ii) the amplification saturates at increasing input signal. We demonstrate that the strong-field theory in the frame of high harmonic generation fully supports the appearance of both the avalanche and saturation effects in the amplification of extreme ultraviolet attosecond pulse trains. We confirm that the amplification takes place only if the seed pulses are perfectly synchronized with the driving strong field in the amplifier. We performed an experimental study and subsequent model calculation on He gas driven by intense 30-fs-long laser pulses, which was seeded with an attosecond pulse train at 110 eV generated in a separated Ne gas jet. The comparison of the performed calculations with the measurements clearly demonstrates that the pumped He gas med...

  12. Theory of second-harmonic generation in silica nanowires

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper

    2010-01-01

    The possibility of second-harmonic generation based on surface dipole and bulk multipole nonlinearities in silica nanowires is investigated numerically. Both circular and microstructured nanowires are considered. Phase matching is provided by propagating the pump field in the fundamental mode......, while generating the second harmonic in one of the modes of the LP11 multiplet. This is shown to work in both circular and microstructured nanowires, although only one of the LP11 modes can be phase-matched in the microstructure. The prospect of obtaining large conversion efficiencies in silica......-based nanowires is critically discussed, based on simulations of second-harmonic generation in nanowires with a fluctuating phase-matching wavelength. It is concluded that efficient wavelength conversion will either require strong improvements in the nanowire uniformity, or an increase of the second...

  13. Confocal Imaging of Biological Tissues Using Second Harmonic Generation

    Energy Technology Data Exchange (ETDEWEB)

    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.

  14. Plasma high-order-harmonic generation from ultraintense laser pulses

    Science.gov (United States)

    Tang, Suo; Kumar, Naveen; Keitel, Christoph H.

    2017-05-01

    Plasma high-order-harmonic generation from an extremely intense short-pulse laser is explored by including the effects of ion motion, electron-ion collisions, and radiation reaction force in the plasma dynamics. The laser radiation pressure induces plasma ion motion through the hole-boring effect, resulting in frequency shifting and widening of the harmonic spectra. The classical radiation reaction force slightly mitigates the frequency broadening caused by the ion motion. Based on the results and physical considerations, parameter maps highlighting the optimum regions for generating a single intense attosecond pulse and coherent XUV radiation are presented.

  15. Cluster size dependence of high-order harmonic generation

    Science.gov (United States)

    Tao, Y.; Hagmeijer, R.; Bastiaens, H. M. J.; Goh, S. J.; van der Slot, P. J. M.; Biedron, S. G.; Milton, S. V.; Boller, K.-J.

    2017-08-01

    We investigate high-order harmonic generation (HHG) from noble gas clusters in a supersonic gas jet. To identify the contribution of harmonic generation from clusters versus that from gas monomers, we measure the high-order harmonic output over a broad range of the total atomic number density in the jet (from 3×1016 to 3 × 1018 {{cm}}-3) at two different reservoir temperatures (303 and 363 K). For the first time in the evaluation of the harmonic yield in such measurements, the variation of the liquid mass fraction, g, versus pressure and temperature is taken into consideration, which we determine, reliably and consistently, to be below 20% within our range of experimental parameters. By comparing the measured harmonic yield from a thin jet with the calculated corresponding yield from monomers alone, we find an increased emission of the harmonics when the average cluster size is less than 3000. Using g, under the assumption that the emission from monomers and clusters add up coherently, we calculate the ratio of the average single-atom response of an atom within a cluster to that of a monomer and find an enhancement of around 100 for very small average cluster size (∼200). We do not find any dependence of the cut-off frequency on the composition of the cluster jet. This implies that HHG in clusters is based on electrons that return to their parent ions and not to neighboring ions in the cluster. To fully employ the enhanced average single-atom response found for small average cluster sizes (∼200), the nozzle producing the cluster jet must provide a large liquid mass fraction at these small cluster sizes for increasing the harmonic yield. Moreover, cluster jets may allow for quasi-phase matching, as the higher mass of clusters allows for a higher density contrast in spatially structuring the nonlinear medium.

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

    CERN Document Server

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

    2016-01-01

    Isotropic gases irradiated by long pulses of intense IR light can generate very high harmonics of the incident field. It is generally accepted that, due to the symmetry of the generating medium, be it an atomic or an isotropic molecular gas, only odd harmonics of the driving field can be produced. Here we show how the interplay of electronic and nuclear dynamics can lead to a marked breakdown of this standard picture: a substantial part of the harmonic spectrum can consist of even rather than odd harmonics. We demonstrate the effect using ab-initio solutions of the time-dependent Schr\\"odinger equation for $H$$_2$$^+$ and its isotopes in full dimensionality. By means of a simple analytical model, we identify its physical origin, which is the appearance of a permanent dipole moment in dissociating homonuclear molecules, caused by light-induced localization of the electric charge during dissociation. The effect arises for sufficiently long laser pulses and the region of the spectrum where even harmonics are pro...

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

    Science.gov (United States)

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

    2014-05-01

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

  18. Harmonic Resonance Damping with a Hybrid Compensation System in Power Systems with Dispersed Generation

    DEFF Research Database (Denmark)

    Chen, Zhe; Pedersen, John Kim; Blaabjerg, Frede

    2004-01-01

    A hybrid compensation system consisting of an active filter and a group of distributed passive filters has been studied previously. The passive filters are used for each distorting load or Dispersed Generation (DG) unit to remove major harmonics and provide reactive power compensation. The active...... filter is connected in parallel with the distributed passive filters and loads/DGs to correct the system unbalance and remove the remaining harmonic components. The effectiveness of the presented compensation system has also been demonstrated. This paper studies the performance of the hybrid compensation...... system under system harmonic resonance. The harmonic resonance and the characteristics of harmonic sources are briefly described. The damping effects of the active filter in the hybrid filter system are analyzed with a simplified circuit. An example system including various power electronic interfaces...

  19. Synthesis of Variable Harmonic Impedance in Inverter-Interfaced Distributed Generation Unit for Harmonic Damping Throughout a Distribution Network

    DEFF Research Database (Denmark)

    Wang, Xiongfei; Blaabjerg, Frede; Chen, Zhe

    2012-01-01

    at the dominant harmonic frequencies. Thus, the harmonic voltage drop on the grid-side inductance and the harmonic resonances throughout a distribution feeder with multiple shunt-connected capacitors can be effectively attenuated. Simulation and laboratory test results validate the performance of the proposed......This paper proposes a harmonic impedance synthesis technique for voltage-controlled distributed generation inverters in order to damp harmonic voltage distortion on a distribution network. The approach employs a multiloop control scheme, where a selective harmonic load current feedforward loop...... based on the bandpass filter is developed, in addition to the inner inductor current and the outer capacitor voltage control loops. Together with the use of multiple resonant integrators in the voltage control loop, the negative harmonic inductances and positive harmonic resistances are synthesized...

  20. Synthesis of variable harmonic impedance in inverter-interfaced distributed generation unit for harmonic damping throughout a distribution network

    DEFF Research Database (Denmark)

    Wang, Xiongfei; Blaabjerg, Frede; Chen, Zhe

    2012-01-01

    harmonic frequencies. Thus, the harmonic voltage drop and harmonic resonances throughout a distribution line with multiple shunt-connected capacitors can be effectively attenuated. Simulation and laboratory test results are shown to verify the performance of the proposed control method.......This paper proposes a harmonic impedance synthesis technique for voltage-controlled distributed generation inverter in order to damp harmonic voltage distortion on a distribution network. The approach employs a multiloop control scheme, where a selective load harmonic current feedforward loop based...... on band-pass filter is developed in addition to the inner inductor current and the outer capacitor voltage control loops. Together with the use of multiple resonant integrators in the voltage control loop, the negative harmonic inductances and positive harmonic resistances are synthesized at dominant...

  1. Role of Rydberg States In High-order Harmonic Generation

    CERN Document Server

    Beaulieu, Samuel; Comby, Antoine; Wanie, Vincent; Petit, Stéphane; Légaré, François; Catoire, Fabrice; Mairesse, Yann

    2016-01-01

    The role of Rydberg states in strong field physics has known a renewed interest in the past few years with the study of resonant high-order harmonic generation. In addition to its fundamental in- terest, this process could create bright sources of coherent vacuum and extreme ultraviolet radiation with controlled polarization state. We investigate the spectral, spatial and temporal characteristics of the radiation produced near the ionization threshold of argon by few-cycle laser pulses. The intensity-dependence of the emission shows that two different pathways interfere to populate the Rydberg states. Furthermore, we show that the population of Rydberg states can lead to different emission mecanisms: either direct emission through XUV Free Induction Decay, or sequentially with absorption of additional photons, in processes similar to resonance-enhanced multiphoton above- threshold ionization. Last, using the attosecond lighthouse technique we show that the resonant emission from Rydberg states is not temporal...

  2. High-Harmonic Generation Enhanced by Dynamical Electron Correlation

    Science.gov (United States)

    Tikhomirov, Iliya; Sato, Takeshi; Ishikawa, Kenichi L.

    2017-05-01

    We theoretically study multielectron effects in high-harmonic generation (HHG), using all-electron first-principles simulations for a one-dimensional model atom. In addition to the usual plateau and cutoff (from a cation in the present case, since the neutral is immediately ionized), we find a prominent resonance peak far above the plateau and a second plateau extended beyond the first cutoff. These features originate from the dication response enhanced by orders of magnitude due to the action of the Coulomb force from the rescattering electron, and, hence, are a clear manifestation of electron correlation. Although the present simulations are done in 1D, the physical mechanism underlying the dramatic enhancement is expected to hold also for three-dimensional real systems. This will provide new possibilities to explore dynamical electron correlation in intense laser fields using HHG, which is usually considered to be of single-electron nature in most cases.

  3. Second-harmonic generation imaging of collagen in ancient bone

    Directory of Open Access Journals (Sweden)

    B. Thomas

    2017-12-01

    Full Text Available Second-harmonic generation imaging (SHG captures triple helical collagen molecules near tissue surfaces. Biomedical research routinely utilizes various imaging software packages to quantify SHG signals for collagen content and distribution estimates in modern tissue samples including bone. For the first time using SHG, samples of modern, medieval, and ice age bones were imaged to test the applicability of SHG to ancient bone from a variety of ages, settings, and taxa. Four independent techniques including Raman spectroscopy, FTIR spectroscopy, radiocarbon dating protocols, and mass spectrometry-based protein sequencing, confirm the presence of protein, consistent with the hypothesis that SHG imaging detects ancient bone collagen. These results suggest that future studies have the potential to use SHG imaging to provide new insights into the composition of ancient bone, to characterize ancient bone disorders, to investigate collagen preservation within and between various taxa, and to monitor collagen decay regimes in different depositional environments.

  4. Role of the Ionic Potential in High Harmonic Generation

    CERN Document Server

    Shafir, D; Higuet, J; Soifer, H; Dagan, M; Descamps, D; Mevel, E; Petit, S; Worner, H J; Pons, B; Dudovich, N; Mairesse, Y

    2013-01-01

    Recollision processes provide direct insight into the structure and dynamics of electronic wave functions. However, the strength of the process sets its basic limitations - the interaction couples numerous degrees of freedom. In this Letter we decouple the basic steps of the process and resolve the role of the ionic potential which is at the heart of a broad range of strong field phenomena. Specifically, we measure high harmonic generation from argon atoms. By manipulating the polarization of the laser field we resolve the vectorial properties of the interaction. Our study shows that the ionic core plays a significant role in all steps of the interaction. In particular, Coulomb focusing induces an angular deflection of the electrons before recombination. A complete spatiospectral analysis reveals the influence of the potential on the spatiotemporal properties of the emitted light.

  5. Second harmonic generation from photonic structured GaN nanowalls

    Energy Technology Data Exchange (ETDEWEB)

    Soya, Takahiro; Inose, Yuta; Kunugita, Hideyuki; Ema, Kazuhiro; Yamano, Kouji; Kikuchi, Akihiko; Kishino, Katsumi, E-mail: t-soya@sophia.ac.j [Department of Engineering and Applied Sciences, Sophia University 7-1, Kioi-cho, Chiyoda-ku, Tokyo 102-8554 (Japan)

    2009-11-15

    We observed large enhancement of reflected second harmonic generation (SHG) using the one-dimensional photonic effect in regularly arranged InGaN/GaN single-quantum-well nanowalls. Using the effect when both fundamental and SH resonate with the photonic mode, we obtained enhancement of about 40 times compared with conditions far from resonance.

  6. Multi-order nonlinear diffraction in second harmonic generation

    DEFF Research Database (Denmark)

    Saltiel, S. M.; Neshev, D.; Krolikowski, Wieslaw

    We analyze the emission patterns in the process of second harmonic (SH) generation in χ(2) nonlinear gratings and identify for the first time, to the best of our knowledge, the evidence of Raman-Nath type nonlinear diffraction in frequency doubling processes....

  7. High intensity direct third harmonic generation in BBO

    Energy Technology Data Exchange (ETDEWEB)

    Banks, P.S., LLNL

    1998-02-23

    The azimuthal dependence of second- and third-order coupling are used to measure the relative contributions of each to direct third harmonic generation with efficiencies up to 6%. The values of {xi}{sub ij}{sup (3)} are measured.

  8. Theory of surface second-harmonic generation in silica nanowires

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper

    2010-01-01

    -based nanowires is critically discussed, based on simulations of second-harmonic generation in nanowires with a fluctuating phase-matching wavelength. It is concluded that efficient wavelength conversion will require strong improvements in the nanowire uniformity, peak powers well in excess of 10 KW, increase...

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Directory of Open Access Journals (Sweden)

    Davidson II Roderick B.

    2015-05-01

    Full Text Available The enhanced electric field at plasmonic resonances in nanoscale antennas can lead to efficient harmonic generation, especially when the plasmonic geometry is asymmetric on either inter-particle or intra-particle levels. The planar Archimedean nanospiral offers a unique geometrical asymmetry for second-harmonic generation (SHG because the SHG results neither from arranging centrosymmetric nanoparticles in asymmetric groupings, nor from non-centrosymmetric nanoparticles that retain a local axis of symmetry. Here, we report forward SHG from planar arrays of Archimedean nanospirals using 15 fs pulses from a Ti:sapphire oscillator tuned to 800 nm wavelength. The measured harmonic-generation efficiencies are 2.6·10−9, 8·10−9 and 1.3·10−8 for left-handed circular, linear, and right-handed circular polarizations, respectively. The uncoated nanospirals are stable under average power loading of as much as 300 μWper nanoparticle. The nanospirals also exhibit selective conversion between polarization states. These experiments show that the intrinsic asymmetry of the nanospirals results in a highly efficient, two-dimensional harmonic generator that can be incorporated into metasurface optics.

  11. Second harmonic generation from corona-poled polymer thin films ...

    Indian Academy of Sciences (India)

    2014-02-09

    Feb 9, 2014 ... Abstract. We characterize thermal stability of second harmonic generation (SHG) properties of four different Y-type polymers poled using corona poling method. These polymers are based on donor–acceptor–donor-type repeating unit with different aromatic moieties acting as donors and dicyanomethylene ...

  12. Polarization-Modulated Second Harmonic Generation Microscopy in Collagen

    Energy Technology Data Exchange (ETDEWEB)

    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

  13. High-order harmonic generation in a capillary discharge

    Science.gov (United States)

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

    2010-06-01

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

  14. Measurement of the angular distributions of high-order harmonic generations from aligned CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Lu, H; Zhao, S T; Zhang, Z X; Liu, P; Zeng, Z N; Li, R X; Xu, Z Z, E-mail: peng@siom.ac.cn, E-mail: ruxinli@mail.shcnc.ac.cn [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, No. 390, Qinghe Road, Jiading District, Shanghai 201800 (China)

    2011-02-01

    In this study, the angular distributions of harmonics emission from aligned CO{sub 2} are explored experimentally and theoretically, and the validity of Strong Field Approximation (SFA) model in the molecular high harmonic generation is therefore studied. The study shows that for describing the angle distribution of high harmonic generation from molecules, SFA is roughly consistent with the qualitative analysis, while the quantitative analysis is different.

  15. Harmonic generation by atomic and nanoparticle precursors in a ZnS laser ablation plasma

    Energy Technology Data Exchange (ETDEWEB)

    Oujja, M.; Lopez-Quintas, I.; Benítez-Cañete, A.; Nalda, R. de; Castillejo, M., E-mail: marta.castillejo@iqfr.csic.es

    2017-01-15

    Highlights: • Plume species in infrared ns laser ablation of ZnS studied by low-order harmonic generation. • Different spatiotemporal properties of harmonics from atoms and nanoparticles. • Results compared with calculations of optical frequency up-conversion in perturbative regime. - Abstract: Harmonic generation of a driving laser propagating across a laser ablation plasma serves for the diagnosis of multicomponent plumes. Here we study the contribution of atomic and nanoparticle precursors to the generation of coherent ultraviolet and vacuum ultraviolet light as low-order harmonics of the fundamental emission (1064 nm) of a Q-switched Nd:YAG laser in a nanosecond infrared ZnS laser ablation plasma. Odd harmonics from the 3rd up to the 9th order (118.2 nm) have been observed with distinct temporal and spatial characteristics which were determined by varying the delay between the ablation and driving nanosecond pulses and by spatially scanning the plasma with the focused driving beam propagating parallel to the target. At short distances from the target surface (≤1 mm), the harmonic intensity displays two temporal components peaked at around 250 ns and 10 μs. While the early component dies off quickly with increasing harmonic order and vanishes for the 9th order, the late component is notably intense for the 7th harmonic and is still clearly visible for the 9th. Spectral analysis of spontaneous plume emissions help to assign the origin of the two components. While the early plasma component is mainly constituted by neutral Zn atoms, the late component is mostly due to nanoparticles, which upon interaction with the driving laser are subject to breakup and ionization. With the aid of calculations of the phase matching integrals within the perturbative model of optical harmonic generation, these results illustrate how atom and nanoparticle populations, with differing temporal and spatial distributions within the ablation plasma, contribute to the nonlinear

  16. Elastography using harmonic ultrasonic imaging: a feasibility study.

    Science.gov (United States)

    Desai, Raghavendra Reddy; Krouskop, Thomas A; Righetti, Raffaella

    2010-04-01

    Tissue Harmonic Imaging (THI) is a relatively new modality that has had a significant impact in the ultrasound field. In the recent past, imaging the mechanical properties of tissues using elastography has also gained great interest. In this paper, we investigate the feasibility of combining these two state-of-the-art ultrasound-imaging modalities. The performance of elastograms obtained using harmonic ultrasonic signals is studied with simulations and compared to the performance of conventional elastograms using standard statistical methods. Experiments are used as a proof of the technical feasibility of generating tissue-harmonic elastograms using experimental harmonic signals. The results of our simulation study indicate that all image quality factors considered in this study (elastographic signal-to-noise ratio, elastographic contrast-to-noise ratio and spatial resolution) may be improved when using harmonic ultrasonic signals, provided that the ultrasound system is characterized by high bandwidth, high sampling frequency and large lateral sampling. Preliminary experimental results suggest that it is technically feasible to generate experimental elastograms using harmonic signals, provided that the sonographic signal-to-noise ratio of the pre- and postcompression harmonic frames is sufficiently high to guarantee reliable values of correlation.

  17. Harmonics generation near ion-cyclotron frequency of ECR plasma

    Science.gov (United States)

    Chowdhury, Satyajit; Biswas, Subir; Chakrabarti, Nikhil; Pal, Rabindranath

    2017-10-01

    Wave excitation at different frequency regime is employed in the MaPLE device ECR plasma for varied excitation amplitude. At very low amplitude excitation, mainly fundamental frequency mode of the exciter signal frequency comes into play. With the increase in amplitude of applied perturbation, harmonics are generated and dominant over the fundamental frequency mode. There is a fixed critical amplitude of exciter to yield the harmonics and is independent of applied frequency. Observed harmonics and the main frequency mode has propagation characteristics and are discussed here. Exact mode number and propagation nature are also tried to measure in the experiment. Detailed experimental results will be presented. Department of Science and Technology of Government of India (Project No. SB/S2/HEP-005/2014).

  18. Cluster size dependence of high-order harmonic generation

    CERN Document Server

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

    2016-01-01

    We investigate high-order harmonic generation (HHG) from noble gas clusters in a supersonic gas jet. To identify the contribution of harmonic generation from clusters versus that from gas monomers, we measure the high-order harmonic output over a broad range of the total atomic number density in the jet (from 3x10^{16} cm^{-3} to 3x10^{18} cm^{-3}) at two different reservoir temperatures (303 K and 363 K). For the first time in the evaluation of the harmonic yield in such measurements, the variation of the liquid mass fraction, g, versus pressure and temperature is taken into consideration, which we determine, reliably and consistently, to be below 20% within our range of experimental parameters. Based on measurements with a thin jet where significant variations in reabsorption and the phase matching conditions can be neglected, we conclude that atoms in the form of small clusters (average cluster size < 1000 atoms) provide the same higher-order nonlinear response as single-atoms. This implies that HHG in ...

  19. Use of extended laser plasma for generation of high-order harmonics of picosecond duration

    Energy Technology Data Exchange (ETDEWEB)

    Ganeev, R A; Boltaev, G S; Reyimbaev, Sh; Sherniyozov, Kh; Usmanov, T [Institute of Ion-Plasma and Laser Technologies, Uzbekistan Academy of Sciences, Akademgorodok, Tashkent 100125 (Uzbekistan)

    2015-07-31

    We report the results of experimental investigations on the generation of picosecond radiation harmonics in extended laser plasma produced on the surface of different metal targets. The effect of plasma length, heating pulse duration and delay between the heating and transformable pulses on the efficiency of conversion to higher harmonics is studied. The λ = 1064 nm radiation conversion to a short-wavelength (down to 50 nm, 21st harmonic) range in extended plasma of several metals is demonstrated. (interaction of laser radiation with matter. laser plasma)

  20. Third-order-harmonic generation in coherently spinning molecules

    Science.gov (United States)

    Prost, E.; Zhang, H.; Hertz, E.; Billard, F.; Lavorel, B.; Bejot, P.; Zyss, Joseph; Averbukh, Ilya Sh.; Faucher, O.

    2017-10-01

    The rotational Doppler effect occurs when circularly polarized light interacts with a rotating anisotropic material. It is manifested by the appearance of a spectral shift ensuing from the transfer of angular momentum and energy between radiation and matter. Recently, we reported terahertz-range rotational Doppler shifts produced in third-order nonlinear optical conversion [O. Faucher et al., Phys. Rev. A 94, 051402(R) (2016), 10.1103/PhysRevA.94.051402]. The experiment was performed in an ensemble of coherently spinning molecules prepared by a short laser pulse exhibiting a twisted linear polarization. The present work provides an extensive analysis of the rotational Doppler effect in third-order-harmonic generation from spinning linear molecules. The underlying physics is investigated both experimentally and theoretically. The implication of the rotational Doppler effect in higher-order processes like high-order-harmonic generation is discussed.

  1. Generation of intense high harmonics: (i) To test and improve resolution of accumulative X-ray streak camera; (ii) To study the effects of Carrier envelope phase on XUV super continuum generation by polarization gating

    Science.gov (United States)

    Shakya, Mahendra Man

    The first part of this thesis describes our novel design, test, and application of our X-ray streak camera to the pulse duration measurement of soft X-rays. We demonstrated a significant improvement in the resolution of the x-ray streak camera by reducing the electron beam size in the deflection plates. This was accomplished by adding a slit in front of the focusing lens and the deflection plates. The temporal resolution reached 280 fs when the slit width was 5 mum. The camera was operated in an accumulative mode and tested by using a 25 fs laser with 2 kHz repetition rate and 1-2% RMS pulse energy stability. We conclude that deflection aberrations, which limit the resolution of the camera, can be appreciably reduced by eliminating the wide-angle electrons. We also employed the same streak camera to demonstrate that it is capable of measuring the pulse duration of X-rays. We measured the pulse duration of X-rays emitted from Ni-like Ag and Cd grazing-incidence laser to be ˜5ps. The measured value agrees with the prediction made by the model and the measurement made by changing the delay as a function of the pulse duration. The streak camera was also tested with various sources of X-ray such as high harmonics generation of soft x-rays from an argon atom using a high power Ti:sapphire laser source of KLS. The result of the measurement manifests its capability for serving as a detector in the study of ultrafast dynamics in the field of physics, chemistry, biology and medical sciences. The second part of this thesis describes our design of a spectrometer to study the effect of the Carrier envelope (CE) phase on polarization gated extreme-ultraviolet (XUV) super-continuum generation. Because the challenge of making single shot experiment possible is to generate a sufficient number of photons, our setup has been built to allow generation of high order harmonics at the maximum phase matched pressure. This is the first time to our knowledge that phase matching in the

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

    CERN Document Server

    Davidson, Roderick B; Vargas, Guillermo; Avanesyan, Sergey M; Haglund, Richard F

    2015-01-01

    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 pulse from a Ti:sapphire oscillator tuned to 800 nm wavelength. The measured harmonic-generation efficiencies are 2.6*10-9, 8*10-9 and 1.3*10-8 for left-handed circular, linear, and right-handed circular polarizations, respectively. The uncoated nanospirals are stable under average power loading of as much as 300 uW per nanoparticle. The nanospirals also exhibit a selective conversion between polarization states. These exp...

  3. The study of radiation-induced damage and remodeling of extracellular matrix of rectum and bladder by second-harmonic generation microscopy

    Science.gov (United States)

    Kochueva, Marina V.; Sergeeva, Ekaterina A.; Ignatjeva, Natalya Yu.; Zakharkina, Olga L.; Kuznetzov, Sergej S.; Kiseleva, Elena B.; Babak, Ksenia V.; Kamensky, Vladislav A.; Maslennikova, Anna V.

    2014-02-01

    Adverse events in normal tissues after irradiation of malignant tumors are of great importance in modern radiation oncology. Second harmonic generation (SHG) microscopy allows observe the structure of collagen fibers and bundles without additional staining. The study objective was evaluation the dose-time dependences of the structural changes occurring in collagen of rat rectum and bladder after gamma-irradiation. Animals were irradiated by a local field at single doses of 10 Gy and 40 Gy. The study of collagen state was carried out in a week and a month after radiation exposure. Paraffin-embedded material was sectioned on the slices 10 mkm thick and SHG-imaging was performed by LSM 510 Meta (Carl Zeiss, Germany). Excitation was implemented with a pulsed (100-fs) titanium-sapphire laser at a wavelength of 800 nm and a pulse repetition frequency of 80 MHz, registration was performed at two wavelengths: 362-415 nm according to collagen fluorescence and 512-576 nm according to myoglobin fluorescence. In a week after irradiation, sings of epithelial damage and edema of submucosal layer, more significant after the dose of 40 Gy were observed on LSM-images. The SHG signal decreased at this time reflecting the processes of collagen degradation independently either in bladder or in rectum. In a month after radiation the increase of size and number of collagen-bearing structures was observed, more essential after irradiation in a dose of 40 Gy. LSM microscopy with SHG allows evaluate changes of normal tissues after ionizing radiation and get information in addition to standard and special histological staining.

  4. High harmonic generation from impulsively aligned SO2

    Science.gov (United States)

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

    2016-05-01

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

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

  7. High-order harmonic generation by polyatomic molecules

    Science.gov (United States)

    Odžak, S.; Hasović, E.; Milošević, D. B.

    2017-04-01

    We present a theory of high-order harmonic generation by arbitrary polyatomic molecules based on the molecular strong-field approximation (MSFA) in the framework of the S-matrix theory. A polyatomic molecule is modeled by an (N + 1)-particle system, which consists of N heavy atomic (ionic) centers and an electron. We derived various versions (with or without the dressing of the initial and/or final molecular state) of the MSFA. The general expression for the T-matrix element takes a simple form for neutral polyatomic molecules. We show the existence of the interference minima in the harmonic spectrum and explain these minima as a multiple-slit type of interference. This is illustrated by numerical examples for the nitrous oxide (N2O) molecule exposed to strong linearly polarized laser field.

  8. Low- and high-order harmonic generation in the extended plasmas produced by laser ablation of zinc and manganese targets

    Energy Technology Data Exchange (ETDEWEB)

    Ganeev, R. A., E-mail: rashid-ganeev@mail.ru [Ophthalmology and Advanced Laser Medical Center, Saitama Medical University, Saitama 350-0495 (Japan); Physical Department, Voronezh State University, Voronezh 394006 (Russian Federation); Baba, M.; Suzuki, M.; Yoneya, S.; Kuroda, H. [Ophthalmology and Advanced Laser Medical Center, Saitama Medical University, Saitama 350-0495 (Japan)

    2014-12-28

    The systematic studies of the harmonic generation of ultrashort laser pulses in the 5-mm-long Zn and Mn plasmas (i.e., application of nanosecond, picosecond, and femtosecond pulses for ablation, comparison of harmonic generation from atomic, ionic, and cluster-contained species of plasma, variation of plasma length, two-color pump of plasmas, etc.) are presented. The conversion efficiency of the 11th–19th harmonics generated in the Zn plasma was ∼5 × 10{sup −5}. The role of the ionic resonances of Zn near the 9th and 10th harmonics on the enhancement of harmonics is discussed. The enhancement of harmonics was also analyzed using the two-color pump of extended plasmas, which showed similar intensities of the odd and even harmonics along the whole range of generation. The harmonics up to the 107th order were demonstrated in the case of manganese plasma. The comparison of harmonic generation in the 5-mm-long and commonly used short (≤0.5 mm) plasma plumes showed the advanced properties of extended media.

  9. Multi-channel electronic and vibrational dynamics in polyatomic resonant high-order harmonic generation

    Science.gov (United States)

    Ferré, A.; Boguslavskiy, A. E.; Dagan, M.; Blanchet, V.; Bruner, B. D.; Burgy, F.; Camper, A.; Descamps, D.; Fabre, B.; Fedorov, N.; Gaudin, J.; Geoffroy, G.; Mikosch, J.; Patchkovskii, S.; Petit, S.; Ruchon, T.; Soifer, H.; Staedter, D.; Wilkinson, I.; Stolow, A.; Dudovich, N.; Mairesse, Y.

    2015-01-01

    High-order harmonic generation in polyatomic molecules generally involves multiple channels of ionization. Their relative contribution can be strongly influenced by the presence of resonances, whose assignment remains a major challenge for high-harmonic spectroscopy. Here we present a multi-modal approach for the investigation of unaligned polyatomic molecules, using SF6 as an example. We combine methods from extreme-ultraviolet spectroscopy, above-threshold ionization and attosecond metrology. Fragment-resolved above-threshold ionization measurements reveal that strong-field ionization opens at least three channels. A shape resonance in one of them is found to dominate the signal in the 20–26 eV range. This resonance induces a phase jump in the harmonic emission, a switch in the polarization state and different dynamical responses to molecular vibrations. This study demonstrates a method for extending high-harmonic spectroscopy to polyatomic molecules, where complex attosecond dynamics are expected. PMID:25608712

  10. Harmonic Wave Generated by Contact Acoustic Nonlinearity in Obliquely Incident Ultrasonic Wave

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Dong Seok; Choi, Sung Ho; Kim, Chung Seok; Jhang, Kyung Young [Hangyang University, Seoul (Korea, Republic of)

    2012-08-15

    The objective of this study is to image the harmonic wave generated by contact acoustic nonlinearity in obliquely incident ultrasonic wave for early detection of closed cracks. A closed crack has been simulated by contacting two aluminum block specimens producing solid-solid contact interfaces and then acoustic nonlinearity has been imaged with contact pressure. Sampling phased array(SPA) and synthetic aperture focusing technique(SAFT) are used for imaging techniques. The amplitude of the fundamental frequency decreased with applying pressure. But, the amplitude of second harmonic increased with pressure and was a maximum amplitude at the simulation point of closed crack. Then, the amplitude of second harmonic decreased. As a result, harmonic imaging of contact acoustic nonlinearity is possible and it is expected to be apply for early detection of initial cracks.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    Burke, Kathleen; Tang, Ping; Brown, Edward

    2013-03-01

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

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

    Science.gov (United States)

    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.

  14. Effect of localized microstructural evolution on higher harmonic generation of guided wave modes

    Science.gov (United States)

    Choi, Gloria; Liu, Yang; Yao, Xiaochu; Lissenden, Cliff J.

    2015-03-01

    Higher harmonic generation of ultrasonic waves has the potential to be used to detect precursors to macroscale damage of phenomenon like fatigue due to microstructural evolution contributing to nonlinear material behavior. Aluminum plates having various plastic zone sizes were plastically deformed to different levels. The fundamental shear horizontal mode was then generated in the plate samples via a magnetostrictive transducer. After propagating through the plastic zone the primary wave mode (SH0) and its third harmonic (sh0) were received by a second transducer. Results of a parallel numerical study using the S1-s2 Lamb mode pair, where sensitivity to changes in third order elastic constants were investigated, are described within the context of the experimental results. Specimens used within both studies are geometrically similar and have double edge notches for dog bone samples that introduce localized plastic deformation. Through both studies, the size of the plastic zone with respect to the propagation distance and damage intensity influence the higher harmonics.

  15. Application of smooth exterior scaling method to calculate the high harmonic generation spectra.

    Science.gov (United States)

    Kalita, Dhruba J; Gupta, Ashish K

    2013-02-21

    We have calculated the high harmonic generation spectra from Xe atom by imposing different kinds of absorbing potentials. Owing to the center of inversion of the model system, one should get odd harmonics only. However, using negative imaginary potentials as an absorbing boundary condition, we have also got even order harmonics along with the odd order harmonics. These non-odd order harmonics are generated due to the spurious reflections occurring at the grid boundary. On the contrary, when smooth exterior scaling methods are used as an absorbing boundary condition, only odd order harmonics are obtained. Hence, smooth exterior scaling methods impose proper absorbing boundary condition.

  16. Soluble semiconductors AAsSe2 (A = Li, Na) with a direct-band-gap and strong second harmonic generation: a combined experimental and theoretical study.

    Science.gov (United States)

    Bera, Tarun K; Jang, Joon I; Song, Jung-Hwan; Malliakas, Christos D; Freeman, Arthur J; Ketterson, John B; Kanatzidis, Mercouri G

    2010-03-17

    AAsSe(2) (A = Li, Na) have been identified as a new class of polar direct-band gap semiconductors. These I-V-VI(2) ternary alkali-metal chalcoarsenates have infinite single chains of (1/infinity)[AsQ(2)(-)] derived from corner-sharing pyramidal AsQ(3) units with stereochemically active lone pairs of electrons on arsenic. The conformations and packing of the chains depend on the structure-directing alkali metals. This results in at least four different structural types for the Li(1-x)Na(x)AsSe(2) stoichiometry (alpha-LiAsSe(2), beta-LiAsSe(2), gamma-NaAsSe(2), and delta-NaAsSe(2)). Single-crystal X-ray diffraction studies showed an average cubic NaCl-type structure for alpha-LiAsSe(2), which was further demonstrated to be locally distorted by pair distribution function (PDF) analysis. The beta and gamma forms have polar structures built of different (1/infinity)[AsSe(2)(-)] chain conformations, whereas the delta form has nonpolar packing. A wide range of direct band gaps are observed, depending on composition: namely, 1.11 eV for alpha-LiAsSe(2), 1.60 eV for LiAsS(2), 1.75 eV for gamma-NaAsSe(2), 2.23 eV for NaAsS(2). The AAsQ(2) materials are soluble in common solvents such as methanol, which makes them promising candidates for solution processing. Band structure calculations performed with the highly precise screened-exchange sX-LDA FLAPW method confirm the direct-gap nature and agree well with experiment. The polar gamma-NaAsSe(2) shows very large nonlinear optical (NLO) second harmonic generation (SHG) response in the wavelength range of 600-950 nm. The theoretical studies confirm the experimental results and show that gamma-NaAsSe(2) has the highest static SHG coefficient known to date, 337.9 pm/V, among materials with band gaps larger than 1.0 eV.

  17. Nonlinear Metasurface for Simultaneous Control of Spin and Orbital Angular Momentum in Second Harmonic Generation.

    Science.gov (United States)

    Li, Guixin; Wu, Lin; Li, King F; Chen, Shumei; Schlickriede, Christian; Xu, Zhengji; Huang, Siya; Li, Wendi; Liu, Yanjun; Pun, Edwin Y B; Zentgraf, Thomas; Cheah, Kok W; Luo, Yu; Zhang, Shuang

    2017-12-13

    The spin and orbital angular momentum (SAM and OAM) of light is providing a new gateway toward high capacity and robust optical communications. While the generation of light with angular momentum is well studied in linear optics, its further integration into nonlinear optical devices will open new avenues for increasing the capacity of optical communications through additional information channels at new frequencies. However, it has been challenging to manipulate the both SAM and OAM of nonlinear signals in harmonic generation processes with conventional nonlinear materials. Here, we report the generation of spin-controlled OAM of light in harmonic generations by using ultrathin photonic metasurfaces. The spin manipulation of OAM mode of harmonic waves is experimentally verified by using second harmonic generation (SHG) from gold meta-atom with 3-fold rotational symmetry. By introducing nonlinear phase singularity into the metasurface devices, we successfully generate and measure the topological charges of spin-controlled OAM mode of SHG through an on-chip metasurface interferometer. The nonlinear photonic metasurface proposed in this work not only opens new avenues for manipulating the OAM of nonlinear optical signals but also benefits the understanding of the nonlinear spin-orbit interaction of light in nanoscale devices.

  18. Characterization of muscle contraction with second harmonic generation microscopy

    Science.gov (United States)

    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

  19. Diode end pumped laser and harmonic generator using same

    Science.gov (United States)

    Byer, Robert L. (Inventor); Dixon, George J. (Inventor); Kane, Thomas J. (Inventor)

    1988-01-01

    A second harmonic, optical generator is disclosed in which a laser diode produces an output pumping beam which is focused by means of a graded, refractive index rod lens into a rod of lasant material, such as Nd:YAG, disposed within an optical resonator to pump the lasant material and to excite the optical resonator at a fundamental wavelength. A non-linear electro-optic material such as MgO:LiNbO.sub.3 is coupled to the excited, fundamental mode of the optical resonator to produce a non-linear interaction with the fundamental wavelength producing a harmonic. In one embodiment, the gain medium and the non-linear material are disposed within an optical resonator defined by a pair of reflectors, one of which is formed on a face of the gain medium and the second of which is formed on a face of the non-linear medium. In another embodiment, the non-linear, electro-optic material is doped with the lasant ion such that the gain medium and the non-linear doubling material are co-extensive in volume. In another embodiment, a non-linear, doubling material is disposed in an optical resonator external of the laser gai medium for improved stability of the second harmonic generation process. In another embodiment, the laser gain medium andthe non-linear material are bonded together by means of an optically transparent cement to form a mechanically stable, monolithic structure. In another embodiment, the non-linear material has reflective faces formed thereon to define a ring resonator to decouple reflections from the non-linear medium back to the gain medium for improved stability.

  20. New results of the high-gain harmonic generation free-electron laser experiment

    CERN Document Server

    Doyuran, A; Ben-Zvi, I; Biedron, S G; Di Mauro, Louis F; Graves, W; Jagger, J M; Johnson, E; Krinsky, S; Malone, R; Pogorelsky, I V; Rakowsky, G; Sajaev, Vadim; Shaftan, T; Skaritka, J; Vasserman, I B; Wang, X J; Woodle, M; Yakimenko, V; Yu, L H

    2001-01-01

    We report on the experimental investigation of high-gain harmonic generation carried out at the Accelerator Test Facility at Brookhaven National Laboratory. A seed CO sub 2 laser at a wavelength of 10.6 mu m was used to generate FEL output at a 5.3-mu m wavelength. The duration of the output pulse was measured using a second-harmonic intensity autocorrelator, and the coherence length was measured using an interferometer. We also measured the energy distribution of the electron beam after it exited the second undulator, observing behavior consistent with that is expected at saturation. The intensity of the harmonic components of the output at 2.65 and 1.77 mu m was determined relative to that of the 5.3-mu m fundamental. Finally, using a corrector magnet upstream of the radiator, steering effects on the trajectories of the electron and light beams were studied.

  1. Resonant-optical-second-harmonic generation from thin C60 films

    NARCIS (Netherlands)

    Koopmans, Bert; Anema, Anton; Jonkman, Harry T.; Sawatzky, George A.; Woude, Folkert van der

    1993-01-01

    We studied the optical-second-harmonic generation from thin C60 films, using a combination of frequency-, rotational-, angular-, and film-thickness-dependent measurements. We present a method to resolve the phase of χ(2) by exploiting the interference between the C60 overlayer contribution and the

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2006-02-01

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

  5. Real-time observation of interfering crystal electrons in high-harmonic generation.

    Science.gov (United States)

    Hohenleutner, M; Langer, F; Schubert, O; Knorr, M; Huttner, U; Koch, S W; Kira, M; Huber, R

    2015-07-30

    Acceleration and collision of particles has been a key strategy for exploring the texture of matter. Strong light waves can control and recollide electronic wavepackets, generating high-harmonic radiation that encodes the structure and dynamics of atoms and molecules and lays the foundations of attosecond science. The recent discovery of high-harmonic generation in bulk solids combines the idea of ultrafast acceleration with complex condensed matter systems, and provides hope for compact solid-state attosecond sources and electronics at optical frequencies. Yet the underlying quantum motion has not so far been observable in real time. Here we study high-harmonic generation in a bulk solid directly in the time domain, and reveal a new kind of strong-field excitation in the crystal. Unlike established atomic sources, our solid emits high-harmonic radiation as a sequence of subcycle bursts that coincide temporally with the field crests of one polarity of the driving terahertz waveform. We show that these features are characteristic of a non-perturbative quantum interference process that involves electrons from multiple valence bands. These results identify key mechanisms for future solid-state attosecond sources and next-generation light-wave electronics. The new quantum interference process justifies the hope for all-optical band-structure reconstruction and lays the foundation for possible quantum logic operations at optical clock rates.

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

    Science.gov (United States)

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

    2009-04-01

    Second harmonic generation of a right circularly polarized Gaussian electromagnetic beam in a magnetized plasma is investigated. The beam causes Ohmic heating of electrons and subsequent redistribution of the plasma, leading to self-defocusing. The radial density gradient, in conjunction with the oscillatory electron velocity, produces density oscillation at the wave frequency. The density oscillation beats with the oscillatory velocity to produce second harmonic current density, giving rise to resonant second harmonic radiation when the wave frequency is one-third of electron cyclotron frequency. The second harmonic field has azimuthal dependence as exp(iθ). The self-defocusing causes a reduction in the efficiency of harmonic generation.

  7. Imaging Cytometry of Human Leukocytes with Third Harmonic Generation Microscopy

    Science.gov (United States)

    Wu, Cheng-Ham; Wang, Tzung-Dau; Hsieh, Chia-Hung; Huang, Shih-Hung; Lin, Jong-Wei; Hsu, Szu-Chun; Wu, Hau-Tieng; Wu, Yao-Ming; Liu, Tzu-Ming

    2016-11-01

    Based on third-harmonic-generation (THG) microscopy and a k-means clustering algorithm, we developed a label-free imaging cytometry method to differentiate and determine the types of human leukocytes. According to the size and average intensity of cells in THG images, in a two-dimensional scatter plot, the neutrophils, monocytes, and lymphocytes in peripheral blood samples from healthy volunteers were clustered into three differentiable groups. Using these features in THG images, we could count the number of each of the three leukocyte types both in vitro and in vivo. The THG imaging-based counting results agreed well with conventional blood count results. In the future, we believe that the combination of this THG microscopy-based imaging cytometry approach with advanced texture analysis of sub-cellular features can differentiate and count more types of blood cells with smaller quantities of blood.

  8. Two-Color Laser High-Harmonic Generation in Cavitated Plasma Wakefields

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Carl; Benedetti, Carlo; Esarey, Eric; Leemans, Wim

    2016-10-03

    A method is proposed for producing coherent x-rays via high-harmonic generation using a laser interacting with highly-stripped ions in cavitated plasma wakefields. Two laser pulses of different colors are employed: a long-wavelength pulse for cavitation and a short-wavelength pulse for harmonic generation. This method enables efficient laser harmonic generation in the sub-nm wavelength regime.

  9. Two-color laser high-harmonic generation in cavitated plasma wakefields

    Science.gov (United States)

    Schroeder, C. B.; Benedetti, C.; Esarey, E.; Leemans, W. P.

    2017-03-01

    A method is proposed for producing coherent x-rays via high-harmonic generation using a laser interacting with highly-stripped ions in cavitated plasma wakefields. Two laser pulses of different colors are employed: a long-wavelength pulse for cavitation and a short-wavelength pulse for harmonic generation. This method enables efficient laser harmonic generation in the sub-nm wavelength regime.

  10. Generation of higher order Gauss-Laguerre modes in single-pass 2nd harmonic generation

    DEFF Research Database (Denmark)

    Buchhave, Preben; Tidemand-Lichtenberg, Peter

    2008-01-01

    We present a realistic method for dynamic simulation of the development of higher order modes in second harmonic generation. The deformation of the wave fronts due to the nonlinear interaction is expressed by expansion in higher order Gauss-Laguerre modes....

  11. Static third-harmonic lines in widely variable fiber continuum generation

    Science.gov (United States)

    Tu, Haohua; Zhao, Youbo; Liu, Yuan; Boppart, Stephen A.

    2014-01-01

    An intriguing phenomenon of third-harmonic generation under fiber continuum generation is the emission of an anharmonic signal. One popular interpretation of this effect has developed into a general theory of fiber third-harmonic generation. Here we produce "static" third-harmonic lines dictated fully by fiber properties independent of pump parameters, in contrast to the signals of all known phase-matched nonlinear optical processes that vary dynamically with these parameters. We argue that the anharmonic signal is an illusion of the continuum generation, that it is in fact harmonic, and that this theory should be reevaluated.

  12. Ultrafast nanoscale imaging using high order harmonic generation (Conference Presentation)

    Science.gov (United States)

    Merdji, Hamed

    2017-05-01

    Ultrafast coherent diffraction using soft and hard X-rays is actually revolutionizing imaging science thanks to new sources recently available. This powerful technique extends standard X-ray diffraction towards imaging of non-crystalline objects and leads actually to a strong impact in physics, chemistry and biology. New ultrashort pulses recently available hold the promise of watching matter evolving with unprecedented space and time resolution. Femtosecond coherent and intense radiation in the soft X-ray (λ = 10-40 nm) is currently produced in our laboratory, from highly non linear frequency conversion (high harmonic generation). A high intensity UV-X coherent beam is obtained using a loose focusing geometry, which allows coupling a very high amount of Ti:Sapphire laser system energy in the HHG process. Using a long gas cell and a long focal length lens, the emitting volume can be increased by orders of magnitude compared to standard HHG set-ups. This approach, allows reaching up to 1x1011 photons per shot for the 25th harmonic (λ=32nm). We have already demonstrated nanoscale imaging in a single shot mode reaching 70 nm spatial resolution and 20 femtoseconds snapshot [1]. We then implemented a recently proposed holographic technique using extended references. This technique, easy to implement, allows a direct non iterative image reconstruction. In the single shot regime, we demonstrated a spatial resolution of 110nm [2].This opens fascinating perspectives in imaging dynamical phenomena to be spread over a large scientific community. I will present recent results in the investigation of femtosecond phase spin-reversals of magnetic nano-domains [3]. Finally, I will report on recent development on noise sensitivity of the technique and perspectives in attosecond coherent imaging [4]. [1] A. Ravasio et al., Physical Review Letters 103, 028104 (2009). [2] D. Gauthier et al., Physical Review Letters 105, 093901 (2010). [3] Vodungbo et al., Nature Communications 3

  13. Quasi-phase-matching for third harmonic generation in noble gases employing ultrasound.

    Science.gov (United States)

    Sapaev, U K; Babushkin, I; Herrmann, J

    2012-09-24

    We study a novel method of quasi-phase-matching for third harmonic generation in a gas cell using the periodic modulation of the gas pressure and thus of the third order nonlinear coefficient in the axial direction created by an ultrasound wave. Using a comprehensive numerical model we describe the quasi-phase matched third harmonic generation of UV (at 266 nm) and VUV pulses (at 133 nm) by using pump pulses at 800 nm and 400 nm, respectively, with pulse energy in the range from 3 mJ to 1 J. In addition, using chirped pump pulses, the generation of sub-20-fs VUV pulses without the necessity for an external chirp compensation is predicted.

  14. Coherence properties of the harmonic generation in intense laser field; Proprietes de coherence de la generation harmonique en champ laser intense

    Energy Technology Data Exchange (ETDEWEB)

    Salieres, P.

    1995-07-03

    In this thesis is presented an experimental and theoretical study of the harmonic generation in intense field and coherence properties of this radiation. The first part reminds the main harmonic specter characteristics. Follow then experimental studies of the tray extension with the laser lighting, the harmonic generation by ions, and the influence of the laser field on the efficiency of generation. The second part presents the quantum model of the harmonic generation in tunnel regime that we have used for the calculation of the dipoles. We compare dependence in lighting of some harmonic, by insisting on the characteristic behavior of the atomic phase. The theory of the propagation is presented in third part. After the reminder of the case of a perturbative polarization, we develop the case of the polarization in tunnel regime. With the help of numerical simulations, we show the influence of the atomic phase on the agreement of phase, and therefore on the efficiency of conversion and profiles of generation in the medium. The importance of the geometry of the interaction is underlined. The part IV presents the study of the spatial coherence of the harmonic radiation. We develop first consequences of the theory of the agreement of phase for profiles of emission. Then the comparison with experimental profiles is detailed in function of the different parameters( order of non linearity, laser lighting, position of the focus by report in the gaseous medium). The study of the spectral and temporal coherence of the part V begins with the experimental effect investigation of the ionization on specters of the harmonic of weak order. We present then theoretical predictions of the preceding model for spectral and temporal profiles of the harmonic of highest order, generated in tunnel regime. The part VI is devoted to the UVX source aspect of the harmonic radiation. (Abstract Truncated)

  15. Imaging leukocytes in vivo with third harmonic generation microscopy

    Science.gov (United States)

    Tsai, Cheng-Kun; Chen, Chien-Kuo; Chen, Yu-Shing; Wu, Pei-Chun; Hsieh, Tsung-Yuan; Liu, Han-Wen; Yeh, Chiou-Yueh; Lin, Win-Li; Chia, Jean-San; Liu, Tzu-Ming

    2013-02-01

    Without a labeling, we demonstrated that lipid granules in leukocytes have distinctive third harmonic generation (THG) contrast. Excited by a 1230nm femtosecond laser, THG signals were generated at a significantly higher level in neutrophils than other mononuclear cells, whereas signals in agranular lymphocytes were one order smaller. These characteristic THG features can also be observed in vivo to trace the newly recruited leukocytes following lipopolysaccharide (LPS) challenge. Furthermore, using video-rate THG microscopy, we also captured images of blood cells in human capillaries. Quite different from red-blood-cells, every now and then, round and granule rich blood cells with strong THG contrast appeared in circulation. The corresponding volume densities in blood, evaluated from their frequencies of appearance and the velocity of circulation, fall within the physiological range of human white blood cell counts. These results suggested that labeling-free THG imaging may provide timely tracing of leukocyte movement and hematology inspection without disturbing the normal cellular or physiological status.

  16. Third harmonic generation of CO2 laser radiation in AgGaSe2 crystal

    Indian Academy of Sciences (India)

    ... for second harmonic and third harmonic generations are 6.3% and 2.4% respectively with the input fundamental pump power density of 5.9 MW/cm2 only. The wavelength of the fundamental CO2 laser radiation used for the generation of harmonics is 10.6 m, (20) line. A compact TEA CO2 laser source has been built in ...

  17. Harmonic generation in laser-produced plasmas containing atoms, ions and clusters: a review. JMO Series: Attosecond and Strong Field Science

    Science.gov (United States)

    Ganeev, R. A.

    2012-03-01

    A review of studies of the high-order harmonic generation of laser radiation in laser-produced plasma revealed recent developments in this field. These include new approaches in application of two-colour pumps, generation of extremely broadened harmonics, further developments in harmonic generation in clusters (fullerenes, carbon nanotubes), destructive interference of harmonics from different emitters, new approaches in resonance-induced enhancement of harmonics, applications of high pulse repetition rate lasers for the enhancement of average power of generating harmonics and observation of quantum path signatures, etc. We show that this method of frequency conversion of laser radiation towards the extreme ultraviolet range became mature during multiple sets of studies carried out in many laboratories worldwide and demonstrated new approaches in the generation of strong coherent short-wavelength radiation for various applications.

  18. Resonant second-harmonic-generation circular-dichroism microscopy reveals molecular chirality in native biological tissues

    CERN Document Server

    Chen, Mei-Yu; Kan, Che-Wei; Lin, Yen-Yin; Ye, Cin-Wei; Wu, Meng-Jer; Liu, Hsiang-Lin; Chu, Shi-Wei

    2016-01-01

    Conventional linear optical activity effects are widely used for studying chiral materials. However, poor contrast and artifacts due to sample anisotropy limit the applicability of these methods. Here we demonstrate that nonlinear second-harmonic-generation circular dichroism spectral microscopy can overcome these limits. In intact collagenous tissues, clear spectral resonance is observed with sub-micrometer spatial resolution. By performing gradual protein denaturation studies, we show that the resonant responses are dominantly due to the molecular chirality.

  19. Harmonics: Generation and Suppression in AC System Networks ...

    African Journals Online (AJOL)

    Majority of loads such as induction motors, battery chargers, static converters, light fittings, arc furnaces, transformers, cables, transmission lines and so on draw both sinusoidal currents and currents which are multiples of the supply frequency, commonly called harmonics. These harmonics are out of phase with the supply ...

  20. Influence of micro- and macro-processes on the high-order harmonic generation in laser-produced plasma

    Energy Technology Data Exchange (ETDEWEB)

    Ganeev, R. A., E-mail: rashid-ganeev@mail.ru [Ophthalmology and Advanced Laser Medical Center, Saitama Medical University, 38 Morohongo, Moroyama-machi, Iruma-gun, Saitama 350-0495 (Japan); Physical Department, Voronezh State University, Voronezh 394006 (Russian Federation)

    2016-03-21

    We compare the resonance-induced enhancement of single harmonic and the quasi-phase-matching-induced enhancement of the group of harmonics during propagation of the tunable mid-infrared femtosecond pulses through the perforated laser-produced indium plasma. We show that the enhancement of harmonics using the macro-process of quasi-phase-matching is comparable with the one using micro-process of resonantly enhanced harmonic. These studies show that joint implementation of the two methods of the increase of harmonic yield could be a useful tool for generation of strong short-wavelength radiation in different spectral regions. We compare these effects in indium, as well as in other plasmas.

  1. Prospects of odd and even harmonic generation by an atom in a high-intensity laser field

    Science.gov (United States)

    Bogatskaya, A. V.; Volkova, E. A.; Popov, A. M.

    2017-05-01

    A new approach for studying the spontaneous emission of an atomic system in the presence of a high-intensity laser field is used to study the process of harmonic generation. The analysis is based on consideration of quantum system interaction, with the quantized field modes being in the vacuum state, while the intense laser field is considered to be classically beyond perturbation theory. The numerical analysis of the emission from the single one-electron 1D atom irradiated by the femtosecond laser pulse of a Ti:Sa laser is discussed. It is demonstrated that not only odd, but also even harmonics can be emitted if the laser field is strong enough. The origin of the appearance of even harmonics is studied. The obtained results are compared with those found in the framework of the semiclassical approach that is widely used to study harmonic generation. It is found that the semiclassical approach is inapplicable in the strong-field limit.

  2. Organized Aggregation of Porphyrins in Lipid Bilayers for Third Harmonic Generation Microscopy.

    Science.gov (United States)

    Cui, Liyang; Tokarz, Danielle; Cisek, Richard; Ng, Kenneth K; Wang, Fan; Chen, Juan; Barzda, Virginijus; Zheng, Gang

    2015-11-16

    Nonlinear optical microscopy has become a powerful tool for high-resolution imaging of cellular and subcellular composition, morphology, and interactions because of its high spatial resolution, deep penetration, and low photo-damage to tissue. Developing specific harmonic probes is essential for exploiting nonlinear microscopic imaging for biomedical applications. We report an organized aggregate of porphyrins (OAP) that formed within lipidic nanoparticles showing fingerprint spectroscopic properties, structure-associated second harmonic generation, and superradiant third harmonic generation. The OAP facilitated harmonic microscopic imaging of living cells with significantly enhanced contrast. The structure-dependent switch between harmonic (OAP-intact) and fluorescence (OAP-disrupted) generation enabled real-time multi-modality imaging of the cellular fate of nanoparticles. Robustly produced under various conditions and easily incorporated into pre-formed lipid nanovesicles, OAP provides a biocompatible nanoplatform for harmonic imaging. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Effect of composition and temperature on the second harmonic generation in silver phosphate glasses

    Science.gov (United States)

    Konidakis, I.; Psilodimitrakopoulos, S.; Kosma, K.; Lemonis, A.; Stratakis, E.

    2018-01-01

    We herein employ nonlinear laser imaging microscopy to explicitly study the dynamics of second harmonic generation (SHG) in silver iodide phosphate glasses. While glasses of this family have gained extensive scientific attention over the years due to their superior conducting properties, considerably less attention has been paid to their unique nonlinear optical characteristics. In the present study, firstly, it is demonstrated that SHG signal intensity is enhanced upon increasing silver content due to the random formation of silver microstructures within the glass network. Secondly, the SHG temperature dynamics were explored near the glass transition temperature (Tg) regime, where significant glass relaxation phenomena occur. It is found that heating towards the Tg improves the SHG efficiency, whereas above Tg, the capacity of glasses to generate second harmonic radiation is drastically suppressed. The novel findings of this work are considered important in terms of the potential employment of these glasses for the realization of advanced photonic applications like optical-switches and wavelength conversion devices.

  4. Second-Harmonic Generation by Electromagnetic Waves at the Surface of a Semi-Infinite Metal

    Science.gov (United States)

    2010-05-01

    Second-Harmonic Generation by Electromagnetic Waves at the Surface of a Semi-Infinite Metal Frank Crowne and Christian Fazi Sensors and...DATES COVERED 00-00-2010 to 00-00-2010 4. TITLE AND SUBTITLE Second-Harmonic Generation by Electromagnetic Waves at the Surface of a Semi

  5. Misconceptions regarding Second Harmonic Generation in X-Ray Free-Electron Lasers

    CERN Document Server

    Geloni, G; Schneidmiller, E; Yurkov, M V

    2005-01-01

    Nonlinear generation of coherent harmonic radiation is an important option in the operation of a X-ray FEL facility since it broadens the spectral range of the facility itself, thus allowing for a wider scope of experimental applications. We found that up-to-date theoretical understanding of second harmonic generation is incorrect. Derivation of correct radiation characteristics will follow our criticism.

  6. Noninvasive corneal stromal collagen imaging using two-photon-generated second-harmonic signals.

    Science.gov (United States)

    Morishige, Naoyuki; Petroll, W Matthew; Nishida, Teruo; Kenney, M Cristina; Jester, James V

    2006-11-01

    To investigate the feasibility of using femtosecond-pulse lasers to produce second-harmonic generated (SHG) signals to noninvasively assess corneal stromal collagen organization. The Eye Institute, University of California, Irvine, California, USA. Mouse, rabbit, and human corneas were examined by two-photon confocal microscopy using a variable-wavelength femtosecond lasers to produce SHG signals. Two types were detected: forward scattered and backward scattered. Wavelength dependence of the SHG signal was confirmed by spectral separation using the 510 Meta (Zeiss). To verify the spatial relation between SHG signals and corneal cells, staining of cytoskeletons and nuclei was performed. Second-harmonic-generated signal intensity was strongest with an excitation wavelength of 800 nm for all 3 species. Second-harmonic-generated forward signals showed a distinct fibrillar pattern organized into bands suggesting lamellae, while backscattered SHG signals appeared more diffuse and indistinct. Reconstruction of SHG signals showed two patterns of lamellar organization: highly interwoven in the anterior stroma and orthogonally arranged in the posterior stroma. Unique to the human cornea was the presence of transverse, sutural lamellae that inserted into Bowman's layer, suggesting an anchoring function. Using two-photon confocal microscopy to generate SHG signals from the corneal collagen provides a powerful new approach to noninvasively study corneal structure. Human corneas had a unique organizational pattern with sutural lamellae to provide important biomechanical support that was not present in mouse or rabbit corneas.

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

    Science.gov (United States)

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

    2017-11-01

    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.

  8. Detailed Equivalent VSC-HVDC Modelling for Time Domain Harmonic Stability Studies in Wind Power Plants

    DEFF Research Database (Denmark)

    Glasdam, Jakob Bærholm; Bak, Claus Leth; Kocewiak, Lukasz Hubert

    2017-01-01

    system with 201 voltage levels, without loss of accuracy compared to conventional modelling of the converter. Harmonic stability is a core concern for both existing and future offshore wind power plants (OWPPs). A harmonic stability study will be undertaken with focus on the number of wind turbine...... generators in service, as this is known to influence the harmonic stability in OWPPs. The paper demonstrates the necessity of the inclusion of a detailed equivalent model of the HVDC converter for harmonic stability studies in the time domain. By implementation of active filtering in the converters...

  9. The analysis of harmonic generation coefficients in the ablative Rayleigh-Taylor instability

    Science.gov (United States)

    Lu, Yan; Fan, Zhengfeng; Lu, Xinpei; Ye, Wenhua; Zou, Changlin; Zhang, Ziyun; Zhang, Wen

    2017-10-01

    In this research, we use the numerical simulation method to investigate the generation coefficients of the first three harmonics and the zeroth harmonic in the Ablative Rayleigh-Taylor Instability. It is shown that the interface shifts to the low temperature side during the ablation process. In consideration of the third-order perturbation theory, the first three harmonic amplitudes of the weakly nonlinear regime are calculated and then the harmonic generation coefficients are obtained by curve fitting. The simulation results show that the harmonic generation coefficients changed with time and wavelength. Using the higher-order perturbation theory, we find that more and more harmonics are generated in the later weakly nonlinear stage, which is caused by the negative feedback of the later higher harmonics. Furthermore, extending the third-order theory to the fifth-order theory, we find that the second and the third harmonics coefficients linearly depend on the wavelength, while the feedback coefficients are almost constant. Further analysis also shows that when the fifth-order theory is considered, the normalized effective amplitudes of second and third harmonics can reach about 25%-40%, which are only 15%-25% in the frame of the previous third-order theory. Therefore, the third order perturbation theory is needed to be modified by the higher-order theory when ηL reaches about 20% of the perturbation wavelength.

  10. Quantum interference during high-order harmonic generation from aligned molecules.

    Science.gov (United States)

    Kanai, Tsuneto; Minemoto, Shinichirou; Sakai, Hirofumi

    2005-05-26

    High-order harmonic generation (HHG) from atoms and molecules offers potential application as a coherent ultrashort radiation source in the extreme ultraviolet and soft X-ray regions. In the three-step model of HHG, an electron tunnels out from the atom and may recombine with the parent ion (emitting a high-energy photon) after undergoing laser-driven motion in the continuum. Aligned molecules can be used to study quantum phenomena in HHG associated with molecular symmetries; in particular, simultaneous observations of both ion yields and harmonic signals under the same conditions serve to disentangle the contributions from the ionization and recombination processes. Here we report evidence for quantum interference of electron de Broglie waves in the recombination process of HHG from aligned CO2 molecules. The interference takes place within a single molecule and within one optical cycle. Characteristic modulation patterns of the harmonic signals measured as a function of the pump-probe delay are explained with simple formulae determined by the valence orbital of the molecules. We propose that simultaneous observations of both ion yields and harmonic signals can serve as a new route to probe the instantaneous structure of molecular systems.

  11. Large second-harmonic generation in thermally poled silica waveguides

    DEFF Research Database (Denmark)

    Arentoft, Jesper; Kristensen, Martin; Pedersen, K.

    2001-01-01

    We report the observation of very large second-harmonic signals from thermally poled silica waveguide samples. Secondary ion mass spectrometry measurements show that significant amounts of silver ions are injected from the top electrode during poling.......We report the observation of very large second-harmonic signals from thermally poled silica waveguide samples. Secondary ion mass spectrometry measurements show that significant amounts of silver ions are injected from the top electrode during poling....

  12. Time and Temperature Dependent Microrheology of Dye-Doped Polymers Using Second Harmonic Generation.

    Science.gov (United States)

    Ghebremichael, Fassil

    The goal of this work is to build an understanding of the microscopic viscoelastic properties of a polymer. We used electric field induced second harmonic (EFISH) measurements of organic molecular probes to study such microrheological properties. Polymers of high optical quality are doped with dye molecules and spin coated into 2-3 mu m thick films. When one of these films is irradiated with laser light at a particular wavelength, in the presence of a static field, second harmonic light (at half the incident wavelength) is generated owing to the dyes' nonlinearities. Note that the host polymer's function is to provide a rigid matrix to hold the guest molecule in place. Such materials are often called molecular materials because the bulk response can be explained directly in terms of a linear sum of the molecular properties. As such, the second harmonic signal is a function of the degree of net orientation of the dye molecules because second harmonic generation is disallowed in bulk centrosymmetric materials. Second harmonic generation is thus a powerful tool in the study of molecular orientation order. The polymer's temperature dependent microscopic environment, elastic strength, and free volume can be determined from second harmonic probed motion of the dye molecules when subjected to external forces such as electric fields. Such studies can be used to help understand the relationship between the microscopic and macroscopic mechanical and optical properties of the dye-polymer system. In this work, the application of a unique electric field temporal profile on the films doped with disperse red 1 (DR1) dye helped us to determine the microscopic elasticities and viscosities and the nature of the distribution of sites of poly(methyl methacrylate), PMMA polymer. With this determination, we were able to better model a dye -polymer system. Our model is shown to be consistent with the experimental results. Our electric field profile has also led to a time

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

    Science.gov (United States)

    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.

  14. High-order-harmonic generation in atomic and molecular systems

    Science.gov (United States)

    Suárez, Noslen; Chacón, Alexis; Pérez-Hernández, Jose A.; Biegert, Jens; Lewenstein, Maciej; Ciappina, Marcelo F.

    2017-03-01

    High-order-harmonic generation (HHG) results from the interaction of ultrashort laser pulses with matter. It configures an invaluable tool to produce attosecond pulses, moreover, to extract electron structural and dynamical information of the target, i.e., atoms, molecules, and solids. In this contribution, we introduce an analytical description of atomic and molecular HHG, that extends the well-established theoretical strong-field approximation (SFA). Our approach involves two innovative aspects: (i) First, the bound-continuum and rescattering matrix elements can be analytically computed for both atomic and multicenter molecular systems, using a nonlocal short range model, but separable, potential. When compared with the standard models, these analytical derivations make possible to directly examine how the HHG spectra depend on the driven media and laser-pulse features. Furthermore, we can turn on and off contributions having distinct physical origins or corresponding to different mechanisms. This allows us to quantify their importance in the various regions of the HHG spectra. (ii) Second, as reported recently [N. Suárez et al., Phys. Rev. A 94, 043423 (2016), 10.1103/PhysRevA.94.043423], the multicenter matrix elements in our theory are free from nonphysical gauge- and coordinate-system-dependent terms; this is accomplished by adapting the coordinate system to the center from which the corresponding time-dependent wave function originates. Our SFA results are contrasted, when possible, with the direct numerical integration of the time-dependent Schrödinger equation in reduced and full dimensionality. Very good agreement is found for single and multielectronic atomic systems, modeled under the single active electron approximation, and for simple diatomic molecular systems. Interference features, ubiquitously present in every strong-field phenomenon involving a multicenter target, are also captured by our model.

  15. Advanced properties of extended plasmas for efficient high-order harmonic generation

    Energy Technology Data Exchange (ETDEWEB)

    Ganeev, R. A. [Ophthalmology and Advanced Laser Medical Center, Saitama Medical University, Saitama 350-0495 (Japan); Physics Department, Voronezh State University, Voronezh 394006 (Russian Federation); Suzuki, M.; Kuroda, H. [Ophthalmology and Advanced Laser Medical Center, Saitama Medical University, Saitama 350-0495 (Japan)

    2014-05-15

    We demonstrate the advanced properties of extended plasma plumes (5 mm) for efficient harmonic generation of laser radiation compared with the short lengths of plasmas (∼0.3–0.5 mm) used in previous studies. The harmonic conversion efficiency quadratically increased with the growth of plasma length. The studies of this process along the whole extreme ultraviolet range using the long plasma jets produced on various metal surfaces, particularly including the resonance-enhanced laser frequency conversion and two-color pump, are presented. Such plasmas could be used for the quasi-phase matching experiments by proper modulation of the spatial characteristics of extended ablating area and formation of separated plasma jets.

  16. Second harmonic generation in 3-d uniform arrangement of type I collagen on nonlinear optics microscopy.

    Science.gov (United States)

    Zhuang, Z F; Zhu, M F; Guo, Z Y; Liu, S H

    2013-01-01

    Second harmonic microscopic imaging and spectroscopy technology has become a powerful tool for biomedical studies, especially in fibrosis-related diseases research. And type I collagen is the major risk factors for fibrotic diseases. In this study, model for three-dimensional (3-D) uniform arrangement type I collagen is set up for researching the second harmonic generation (SHG) on nonlinear optics microscopy. Based on this model, we discuss the influence of different length and size collagen in 3-D arrangement type I collagen. Results can guide us to neatly judge the size, length, and molecules density effect on SHG. For practical application, this theoretical approach can lead us to analyze different severity of collagen diseases. © Wiley Periodicals, Inc.

  17. Resonance enhanced high-order harmonic generation in H2+ by two sequential laser pulses.

    Science.gov (United States)

    Wang, Baoning; He, Lixin; Wang, Feng; Yuan, Hua; Zhu, Xiaosong; Lan, Pengfei; Lu, Peixiang

    2017-07-24

    We investigate high-order harmonic generation in H2+ by using two sequential laser pulses, which consist of a 800-nm pump pulse and a time-delayed 1600-nm probe pulse. Based on the solution of the time-dependent Schrödinger equation, we demonstrate that the harmonic cutoff in our two-pulse scheme is significantly extended compared to that in the 1600-nm probe pulse alone. Meanwhile, the harmonic efficiency is enhanced by 2-3 orders of magnitude due to charge-resonance-enhanced ionization steered by the 800-nm pump pulse. By using a probe pulse with longer wavelength, our scheme can be used for efficient high harmonic generation in the water window region. In addition, the influence of the intensity of the pump pulse and the relative time delay of the two laser pulses on the harmonic generation are also investigated.

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

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Y.; Roland, I.; Checoury, X.; Han, Z.; El Kurdi, M.; Sauvage, S.; Boucaud, P., E-mail: philippe.boucaud@ief.u-psud.fr [Institut d' Electronique Fondamentale, CNRS - Univ. Paris Sud 11, Bâtiment 220, F-91405 Orsay (France); Gayral, B. [Univ. Grenoble Alpes, INAC-SP2M, CEA-CNRS group Nanophysique et Semiconducteurs, F-38000 Grenoble (France); CEA, INAC-SP2M, CEA-CNRS group Nanophysique et Semiconducteurs, F-38000 Grenoble (France); Brimont, C.; Guillet, T. [Université Montpellier 2, Laboratoire Charles Coulomb UMR 5221, F-34905 Montpellier (France); Mexis, M.; Semond, F. [CRHEA-CNRS, Rue Bernard Grégory, F-06560 Valbonne (France)

    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.

  19. Ab initio multiscale simulation of high-order harmonic generation in solids

    Science.gov (United States)

    Floss, Isabella; Lemell, Christoph; Wachter, Georg; Smejkal, Valerie; Sato, Shunsuke A.; Tong, Xiao-Min; Yabana, Kazuhiro; Burgdörfer, Joachim

    2018-01-01

    High-order-harmonic generation by a highly nonlinear interaction of infrared laser fields with matter allows for the generation of attosecond pulses in the XUV spectral regime. This process, well established for atoms, has been recently extended to the condensed phase. Remarkably well-pronounced harmonics up to order ˜30 have been observed for dielectrics. We establish a route toward an ab initio multiscale simulation of solid-state high-order-harmonic generation. We find that mesoscopic effects of the extended system, in particular the realistic sampling of the entire Brillouin zone, the pulse propagation in the dense medium, and the inhomogeneous illumination of the crystal, have a strong effect on the harmonic spectra. Our results provide an explanation for the formation of clean harmonics and have implications for a wide range of nonlinear optical processes in dense media.

  20. On the dipole, velocity and acceleration forms in high-order harmonic generation from a single atom or molecule

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Madsen, Lars Bojer

    2011-01-01

    On the dipole, velocity and acceleration forms in high-order harmonic generation from a single atom or molecule......On the dipole, velocity and acceleration forms in high-order harmonic generation from a single atom or molecule...

  1. Experimental observation of second-harmonic generation and diffusion inside random media

    NARCIS (Netherlands)

    Faez, Sanli; Johnson, P. M.; Mazurenko, D. A.; Lagendijk, Ad

    We have experimentally measured the distribution of the second-harmonic intensity that is generated inside a highly scattering slab of porous gallium phosphide. Two complementary techniques for determining the distribution are used. First, the spatial distribution of second-harmonic light intensity

  2. Localized and propagating surface plasmon resonances in aperture-based third harmonic generation.

    Science.gov (United States)

    Nezami, Mohammadreza S; Gordon, Reuven

    2015-12-14

    We investigate the influence of localized and propagating surface plasmons on third harmonic generation from rectangular apertures in metal films. We designed optimal aperture array structures by using finite-difference time-domain simulations with nonlinear scattering theory. From this design space, we fabricated and measured the third harmonic in the region of maximal performance. We find the highest third harmonic conversion efficiency when the localized resonance is tuned to the fundamental wavelength and the propagating (Bragg) resonance is tuned to the third harmonic; this is 2.5 times larger than the case where the both localized and propagating are tuned to the fundamental wavelength. The two remaining configurations where also investigated with much lower conversion efficiency. When the Bragg resonance is tuned to the third harmonic, directivity improves the collection of third harmonic emission. On the other hand, due to the inherent absorption of gold at the third harmonic, tuning the localized surface plasmon resonance to the third harmonic is less beneficial. All cases showed quantitative agreement with the original theoretical analysis. This work points towards an optimal design criterion for harmonic generation from thin plasmonic metasurfaces.

  3. High-order-harmonic generation in gas with a flat-top laser beam

    Energy Technology Data Exchange (ETDEWEB)

    Boutu, W.; Auguste, T.; Binazon, L.; Gobert, O.; Carre, B. [Service des Photons, Atomes et Molecules, CEA-Saclay, FR-91191 Gif-sur-Yvette Cedex (France); Boyko, O.; Valentin, C. [Laboratoire d' Optique Appliquee, UMR 7639 ENSTA/CNRS/Ecole Polytechnique, FR-91761 Palaiseau (France); Sola, I.; Constant, E.; Mevel, E. [Universite de Bordeaux, CEA, CNRS UMR 5107, CELIA (Centre Lasers Intenses et Applications), FR-33400 Talence (France); Balcou, Ph. [Laboratoire d' Optique Appliquee, UMR 7639 ENSTA/CNRS/Ecole Polytechnique, FR-91761 Palaiseau (France); Universite de Bordeaux, CEA, CNRS UMR 5107, CELIA (Centre Lasers Intenses et Applications), FR-33400 Talence (France); Merdji, H. [Service des Photons, Atomes et Molecules, CEA-Saclay, FR-91191 Gif-sur-Yvette Cedex (France); PULSE Institute for Ultrafast Energy Science, Stanford Linear Accelerator Center, Stanford University, 2575 Sand Hill Road, Menlo Park, California 94025 (United States)

    2011-12-15

    We present experimental and numerical results on high-order-harmonic generation with a flat-top laser beam. We show that a simple binary tunable phase plate, made of two concentric glass plates, can produce a flat-top profile at the focus of a Gaussian infrared beam. Both experiments and numerical calculations show that there is a scaling law between the harmonic generation efficiency and the increase of the generation volume.

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

    Science.gov (United States)

    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.

  5. Second-harmonic generation from a thin spherical layer and No-generation conditions

    Science.gov (United States)

    Kapshai, V. N.; Shamyna, A. A.

    2017-09-01

    In the Rayleigh-Gans-Debye approximation, we solve the problem of second-harmonic generation by an elliptically polarized electromagnetic wave incident on the surface of a spherical particle that is coated by an optically nonlinear layer and is placed in a dielectric. The formulas obtained characterize the spatial distribution of the electric field of the second harmonic in the far-field zone. The most general form of the second-order dielectric susceptibility tensor is considered, which contains four independent components, with three of them being nonchiral and one, chiral. Consistency and inconsistencies between the obtained solution and formulas from works of other authors are found. We analyze the directivity patterns that characterize the spatial distribution of the generated radiation for the nonchiral layer and their dependences on the anisotropy and ellipticity coefficients of the incident wave. It is found that, with increasing radius of the nonlinear layer, the generated radiation becomes more directional. Combinations of parameters for which no radiation is generated are revealed. Based on this, we propose methods for experimental determination of the anisotropy coefficients.

  6. A research technique for the effect of higher harmonic voltages on the operating parameters of a permanent magnet synchronous generator

    Directory of Open Access Journals (Sweden)

    Hasanova L. H.

    2017-12-01

    Full Text Available Nowadays permanent magnet synchronous machines those frequency-controlled from stator side with frequency inverters made on the basis of power transistors or fully controlled thyristors, are widely used as motors and generators. In future they are also promising a good application in transport, including marine. Modern frequency inverters are equipped with a control system based on sine-shaped pulse width modulation. While shaping the voltage in the output of the inverter, in addition to the fundamental harmonic, higher harmonic components are also included in the voltage shape, which certainly affect the operating parameters of the generator (electromagnetic torque, power, currents. To determine this effect the modeling and investigation technique of higher harmonic voltages in the "electric network – frequency converter – synchronous machine with permanent magnets" system has been developed. The proposed equations of a frequency-controlled permanent magnet synchronous machine allow relatively simply reproduce the harmonic composition of the voltage in the output of a frequency inverter equipped with the control system based on a sinusoidal pulse width modulation. The developed research technique can be used for inverters with any number and composition of voltage harmonic components feeding a stator winding of a permanent magnet synchronous machine. On a particular case, the efficiency of the research technique of the higher harmonics influence on the operating parameters of the generator has been demonstrated. At the same time, the study has been carried out taking into account the shape of the voltage curve feeding the windings of the synchronous machine containing in addition to the fundamental harmonic the 8, 10, 11, 13, 14 and 16-th harmonic components, and the rated active power of the synchronous machine has been equal to 1 500 kW.

  7. A novel harmonic control approach of distributed generation converters in a weak microgrid

    DEFF Research Database (Denmark)

    Ding, Guangqian; Gao, Feng; Tang, Yi

    2014-01-01

    This paper proposes a novel approach to compensate the voltage at the point of common coupling (PCC) and the grid line current harmonics through a distributed generation (DG) interfacing converter in a weak microgrid. In the proposed approach, the PCC voltage is indirectly derived from the measured...... converter output voltage, DG line current and line impedance. A voltage closed-loop controller and a current closed-loop controller are designed to achieve both functions of DG real power generation and PCC harmonics compensation. Therefore, the traditional harmonic measurement devices installed at the PCC...... as well as the long distance communication between the PCC and the converter are fully eliminated. In order to avoid overcompensation, a harmonic current limitation algorithm is implemented in the control loop. bBy properly dispatching the harmonic compensation capability, multiple DG unites can...

  8. LED lamp modelling for harmonic studies in distribution systems

    OpenAIRE

    Molina, Julio; Mesas García, Juan José; Mesbahi, Nadhir; Sainz Sapera, Luis

    2017-01-01

    Energy saving policies have boosted the use of light emitting diode (LED) lamps in distribution networks. These lamps are non-linear loads which inject harmonic currents into the distribution system, which has led to a decrease in the system power quality. Study of the modelling of these lamps would allow the prediction of harmonic emissions into distribution systems. This study presents a frequency-domain LED lamp model for harmonic emission calculation, together with a simple estimation pro...

  9. Second Harmonic Generation Imaging Analysis of Collagen Arrangement in Human Cornea

    OpenAIRE

    Park, Choul Yong; Lee, Jimmy K.; Chuck, Roy S.

    2015-01-01

    In this paper, we imaged human cornea using a second harmonic generation imaging technique. The horizontal collagen bundle arrangement of corneal stroma as a function of depth and location was analyzed.

  10. Sensitivity of echo enabled harmonic generation to sinusoidal electron beam energy structure

    Science.gov (United States)

    Hemsing, E.; Garcia, B.; Huang, Z.; Raubenheimer, T.; Xiang, D.

    2017-06-01

    We analytically examine the bunching factor spectrum of a relativistic electron beam with sinusoidal energy structure that then undergoes an echo-enabled harmonic generation (EEHG) transformation to produce high harmonics. The performance is found to be described primarily by a simple scaling parameter. The dependence of the bunching amplitude on fluctuations of critical parameters is derived analytically, and compared with simulations. Where applicable, EEHG is also compared with high gain harmonic generation (HGHG) and we find that EEHG is generally less sensitive to several types of energy structure. In the presence of intermediate frequency modulations like those produced by the microbunching instability, EEHG has a substantially narrower intrinsic bunching pedestal.

  11. Pattern formation in singly resonant second-harmonic generation with competing parametric oscillation

    DEFF Research Database (Denmark)

    Lodahl, P.; Saffman, M.

    1999-01-01

    fundamental field, and its coupling to a pair of nondegenerate parametric fields. The parametric fields are driven by the nonresonant second-harmonic field. Analysis indicates the existence of transverse instability of the pump field alone, as well as the possibility of simultaneous instability of the pump......We theoretically investigate the generation of spatial patterns in intracavity second-harmonic generation. We consider a cavity with planar mirrors that is resonant at the fundamental frequency, but not at the second-harmonic frequency. A mean-field model is derived that describes the resonant...

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

    Science.gov (United States)

    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

  13. Stator Current Harmonic Control with Resonant Controller for Doubly Fed Induction Generator

    DEFF Research Database (Denmark)

    Liu, Changjin; Blaabjerg, Frede; Chen, Wenjie

    2012-01-01

    rotor current control loop for harmonic suppression. The overall control scheme is implemented in dq frame. Based on a mathematical model of the DFIG control system, the effects on system stability using the resonant controller, an analysis of the steady-state error, and the dynamic performance......Voltage harmonics in the grid can introduce stator current harmonics in a doubly fed induction generator (DFIG) wind turbine system, which may potentially impact the generated power quality. Therefore, wind turbine current controllers need to be designed to eliminate the impact of grid voltage...

  14. Temporal characterization of harmonic radiation generated by intense laser-plasma interaction

    OpenAIRE

    Nomura, Yutaka

    2008-01-01

    Attosecond physics has become one of the most thriving field of science over the last decade. Although high-order harmonic generation from gaseous media is widely used as the source of attosecond pulses, a demand for more intense coherent extreme ultraviolet (XUV) and soft x-ray (SXR) radiation sources is growing. The process of high-order harmonic generation from plasma surfaces has attracted a strong interest as a promising candidate to meet this demand. Despite many theoretical predictions...

  15. Third-harmonic generation microscopy reveals dental anatomy in ancient fossils.

    Science.gov (United States)

    Chen, Yu-Cheng; Lee, Szu-Yu; Wu, Yana; Brink, Kirstin; Shieh, Dar-Bin; Huang, Timothy D; Reisz, Robert R; Sun, Chi-Kuang

    2015-04-01

    Fossil teeth are primary tools in the study of vertebrate evolution, but standard imaging modalities have not been capable of providing high-quality images in dentin, the main component of teeth, owing to small refractive index differences in the fossilized dentin. Our first attempt to use third-harmonic generation (THG) microscopy in fossil teeth has yielded significant submicrometer level anatomy, with an unexpectedly strong signal contrasting fossilized tubules from the surrounding dentin. Comparison between fossilized and extant teeth of crocodilians reveals a consistent evolutionary signature through time, indicating the great significance of THG microscopy in the evolutionary studies of dental anatomy in fossil teeth.

  16. Ultrasonic harmonic generation from materials with up to cubic nonlinearity.

    Science.gov (United States)

    Kube, Christopher M; Arguelles, Andrea P

    2017-08-01

    This letter considers the combined effects of quadratic and cubic nonlinearity on plane wave propagation in generally anisotropic elastic solids. Displacement solutions are derived that represent the fundamental, second-, and third-harmonic waves. In arriving at the solutions, the quadratic and cubic nonlinearity parameters for generally anisotropic materials are defined. The effects of quadratic and cubic nonlinearity are shown to influence the amplitude and phase of the fundamental wave. In addition, the phase of the third-harmonic depends on a simple combination of the quadratic and cubic nonlinearity parameters. Nonlinearity parameters are given explicitly for materials having isotropic and cubic symmetry. Lastly, acoustic nonlinearity surfaces are introduced, which illustrate the nonlinearity parameters as a function of various propagation directions in anisotropic materials.

  17. Electron motion enhanced high harmonic generation in xenon clusters

    CERN Document Server

    Li, Na; Bai, Ya; Peng, Peng; Li, Ruxin; Xu, Zhizhan

    2016-01-01

    Atomic clusters presents an isolated system that models the bulk materials whose mechanism of HHG remains uncertain, and a promising medium to produce HHG beyond the limited conversion efficiency for gaseous atoms. Here we reveal that the oscillation of collective electron motion within clusters develops after the interaction of intense laser fields, and it significantly enhances the harmonic dipole and increases the quantum phase of the harmonics. Experimentally, the phase matching conditions of HHG from nanometer xenon clusters and atoms are distinguished, which confirms the enhanced internal field that was proposed theoretically a decade ago. The separation of HHG from atoms and clusters allows the determination of the amplitude of the HHG for clusters to be 5 orders higher, corresponding to 4 times higher conversion efficiency for atomic response. The finding provides an insight on the HHG mechanism of bulk materials and a means by which an efficient coherent X-ray source can be developed.

  18. Efficient Third Harmonic Generation from Metal-Dielectric Hybrid Nanoantennas.

    Science.gov (United States)

    Shibanuma, Toshihiko; Grinblat, Gustavo; Albella, Pablo; Maier, Stefan A

    2017-04-12

    High refractive index dielectric nanoantennas are expected to become key elements for nonlinear nano-optics applications due to their large nonlinearities, low energy losses, and ability to produce high electric field enhancements in relatively large nanoscale volumes. In this work, we show that the nonlinear response from a high-index dielectric nanoantenna can be significantly improved by adding a metallic component to build a metal-dielectric hybrid nanostructure. We demonstrate that the plasmonic resonance of a Au nanoring can boost the anapole mode supported by a Si nanodisk, strongly enhancing the electric field inside the large third-order susceptibility dielectric. As a result, a high third harmonic conversion efficiency, which reaches 0.007% at a third harmonic wavelength of 440 nm, is obtained. In addition, by suitably modifying geometrical parameters of the hybrid nanoantenna, we tune the enhanced third harmonic emission throughout the optical regime. Coupling metallic and dielectric nanoantennas to expand the potential of subwavelength structures opens new paths for efficient nonlinear optical effects in the visible range on the nanoscale.

  19. Quantum properties of transverse pattern formation in second-harmonic generation

    DEFF Research Database (Denmark)

    Bache, Morten; Scotto, P.; Zambrini, R.

    2002-01-01

    these equations through extensive numerical simulations and analytically in the linearized limit. Our study, made below and above the threshold of pattern formation, is guided by a microscopic scheme of photon interaction underlying pattern formation in second-harmonic generation. Close to the threshold...... transverse wave number, which are not identified in a linearized analysis, are also described. The intensity differences between opposite points of the far fields are shown to exhibit sub-Poissonian statistics, revealing the quantum nature of the correlations. We observe twin beam correlations in both...

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

    Science.gov (United States)

    Yost, William T.; Cantrell, John H.

    1990-01-01

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

  1. Dependence of third-harmonic generation on melanin concentration in solution

    Science.gov (United States)

    Su, Tung-Yu; Liao, Chien-Sheng; Yang, Chih-Yuan; Zhuo, Zong-Yan; Chen, Szu-Yu; Chu, Shi-Wei

    2011-03-01

    In this study, we performed theoretical analysis and experimental measurement of third harmonic generation (THG) in melanin solution with different concentrations. As predicted by theory, only THG at glass/solution interface was observed due to Guoy phase shift effect. We have shown that this interfacial THG intensity is strongly affected by index matching condition between the two media, leading to minimal THG at a certain melanin concentration. By fitting the dependence of THG intensity versus melanin concentration, linear and nonlinear electric susceptibilities of melanin are obtained, providing a valuable tool to characterize optical properties of biological molecules.

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

    Science.gov (United States)

    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.

  3. Three-colour entanglement produced by the single-pass quasi-phase-matching fourth harmonic generation

    Science.gov (United States)

    Yu, Youbin; Wang, HuaiJun; Zhao, Junwei; Ji, Fengmin; Wang, Yajuan

    2016-08-01

    Three-colour continuous-variable entanglement produced by single-pass cascaded quasi-phase-matching fourth harmonic generation is investigated. The fourth harmonic can be generated through cascaded double-frequency processes in a quasiperiodic optical superlattice by using quasi-phase-matching technology. The conversion dynamics of the cascaded double-frequency processes is studied using quantum stochastic methods. The nature of the entanglement is discussed by applying a necessary and sufficient criterion for continuous-variable entanglement. Strong three-colour entanglement among the fundamental, second-, and fourth-harmonic beams with a double frequency interval can be produced without an optical oscillator cavity. This is experimentally feasible and has potential applications in quantum communication and computation networks.

  4. N2 HOMO-1 orbital cross section revealed through high-order-harmonic generation

    Science.gov (United States)

    Troß, Jan; Ren, Xiaoming; Makhija, Varun; Mondal, Sudipta; Kumarappan, Vinod; Trallero-Herrero, Carlos A.

    2017-03-01

    We measure multi-orbital contributions to high harmonic generation from aligned nitrogen. We show that the change in revival structure in the cutoff harmonics has a counterpart in the angular distribution when a lower-lying orbital contributes to the harmonic yield. This angular distribution is directly observed in the laboratory without any further deconvolution. Because of the high degree of alignment we are able to distinguish angular contributions of the highest occupied molecular orbital 1 (HOMO-1) orbital from angle-dependent spectroscopic features of the HOMO. In particular, we are able to make a direct comparison with the cross section of the HOMO-1 orbital in the extreme ultraviolet region.

  5. Phase distortions of attosecond pulses produced by resonance-enhanced high harmonic generation

    Science.gov (United States)

    Haessler, S.; Strelkov, V.; Elouga Bom, L. B.; Khokhlova, M.; Gobert, O.; Hergott, J.-F.; Lepetit, F.; Perdrix, M.; Ozaki, T.; Salières, P.

    2013-01-01

    Resonant enhancement of high harmonic generation can be obtained in plasmas containing ions with strong radiative transitions resonant with harmonic orders. The mechanism for this enhancement is still debated. We perform the first temporal characterization of the attosecond emission from a tin plasma under near-resonant conditions for two different resonance detunings. We show that the resonance considerably changes the relative phase of neighboring harmonics. For very small detunings, their phase locking may even be lost, evidencing strong phase distortions in the emission process and a modified attosecond structure. These features are well reproduced by our simulations, allowing their interpretation in terms of the phase of the recombination dipole moment.

  6. High-order harmonic generation using a high-repetition-rate turnkey laser

    CERN Document Server

    Lorek, Eleonora; Heyl, Christoph Michael; Carlström, Stefanos; Paleček, David; Zigmantas, Donatas; Mauritsson, Johan

    2014-01-01

    We generate high-order harmonics at high pulse repetition rates using a turnkey laser. High-order harmonics at 400 kHz are observed when argon is used as target gas. In neon we achieve generation of photons with energies exceeding 90 eV ($\\sim$13 nm) at 20 kHz. We measure a photon flux of 4.4$\\cdot10^{10}$ photons per second per harmonic in argon at 100 kHz. Many experiments employing high-order harmonics would benefit from higher repetition rates, and the user-friendly operation opens up for applications of coherent extreme ultra-violet pulses in new research areas.

  7. Generation of µW level plateau harmonics at high repetition rate.

    Science.gov (United States)

    Hädrich, S; Krebs, M; Rothhardt, J; Carstens, H; Demmler, S; Limpert, J; Tünnermann, A

    2011-09-26

    The process of high harmonic generation allows for coherent transfer of infrared laser light to the extreme ultraviolet spectral range opening a variety of applications. The low conversion efficiency of this process calls for optimization or higher repetition rate intense ultrashort pulse lasers. Here we present state-of-the-art fiber laser systems for the generation of high harmonics up to 1 MHz repetition rate. We perform measurements of the average power with a calibrated spectrometer and achieved µW harmonics between 45 nm and 61 nm (H23-H17) at a repetition rate of 50 kHz. Additionally, we show the potential for few-cycle pulses at high average power and repetition rate that may enable water-window harmonics at unprecedented repetition rate. © 2011 Optical Society of America

  8. Infrared-based least-invasive third and second harmonic generation imaging of ocular tissues

    Science.gov (United States)

    Chen, Szu-Yu; Yu, Han-Chieh; Wang, I.-Jong; Sun, Chi-kuang

    2009-02-01

    Cornea functions as an outermost lens and plays an important role in vision. For cornea diagnosis and treatment, a microscopic imaging system with cellular resolution and high eye safety is strongly desired. Recently, the cell morphology of corneal epithelium and endothelium can be revealed by confocal or two-photon fluorescence microscopy, while the collagen fibers in the corneal stroma can be shown by second harmonic generation (SHG) microscopy. However, in most of the developed imaging tools, visible to near-infrared light sources were used. To increase the eye safety, a light source with longer wavelength would be needed. In this presentation, a study using an infrared laser based nonlinear microscopy to investigate the ocular tissues of a mouse eye will be demonstrated. Since most of autofluorescence was suppressed under infrared excitation, third harmonic generation (THG) microscopy was used to reveal the cellular morphology and ~700μm penetrability could be achieved. Combining SHG with THG, in an intact mouse eye, not only the cornea but also the upper half of the lens could be observed with cellular resolution. Our study indicated that infrared-based SHG and THG microscopy could provide a useful in vivo investigating tool for ophthalmology.

  9. A novel intravital multi-harmonic generation microscope for early diagnosis of oral cancer

    Science.gov (United States)

    Cheng, Yu-Hsiang; Lin, Chih-Feng; Shih, Ting-Fang; Sun, Chi-Kuang

    2013-03-01

    Oral cancer is one of the most frequently diagnosed human cancers and leading causes of cancer death all over the world, but the prognosis and overall survival rate are still poor because of delay in diagnosis and lack of early intervention. The failure of early diagnosis is due to insufficiency of proper diagnostic and screening tools and most patients are reluctant to undergo biopsy. Optical virtual biopsy techniques, for imaging cells and tissues at microscopic details capable of differentiating benign from malignant lesions non-invasively, are thus highly desirable. A novel multi-harmonic generation microscope, excited by a 1260 nm Cr:forsterite laser, with second and third harmonic signals demonstrating collagen fiber distribution and cell morphology in a sub-micron resolution, was developed for clinical use. To achieve invivo observation inside the human oral cavity, a small objective probe with a suction capability was carefully designed for patients' comfort and stability. By remotely changing its focus point, the same objective can image the mucosa surface with a low magnification, illuminated by side light-emitting diodes, with a charge-coupled device (CCD) for site location selection before the harmonic generation biopsy was applied. Furthermore, the slow galvanometer mirror and the fast resonant mirror provide a 30 fps frame rate for high-speed real-time observation and the z-motor of this system is triggered at the same rate to provide fast 3D scanning, again ensuring patients' comfort. Focusing on the special cytological and morphological changes of the oral epithelial cells, our preliminary result disclosed excellent consistency with traditional histopathology studies.

  10. Low-frequency approximation for high-order harmonic generation by a bicircular laser field

    Science.gov (United States)

    Milošević, D. B.

    2018-01-01

    We present low-frequency approximation (LFA) for high-order harmonic generation (HHG) process. LFA represents the lowest-order term of an expansion of the final-state interaction matrix element in powers of the laser-field frequency ω . In this approximation the plane-wave recombination matrix element which appears in the strong-field approximation is replaced by the exact laser-free recombination matrix element calculated for the laser-field dressed electron momenta. First, we have shown that the HHG spectra obtained using the LFA agree with those obtained solving the time-dependent Schrödinger equation. Next, we have applied this LFA to calculate the HHG rate for inert gases exposed to a bicircular field. The bicircular field, which consists of two coplanar counter-rotating fields having different frequencies (usually ω and 2 ω ), is presently an important subject of scientific research since it enables efficient generation of circularly polarized high-order harmonics (coherent soft x rays). Analyzing the photorecombination matrix element we have found that the HHG rate can efficiently be calculated using the angular momentum basis with the states oriented in the direction of the bicircular field components. Our numerical results show that the HHG rate for atoms having p ground state, for higher high-order harmonic energies, is larger for circularly polarized harmonics having the helicity -1 . For lower energies the harmonics having helicity +1 prevails. The transition between these two harmonic energy regions can appear near the Cooper minimum, which, in the case of Ar atoms, makes the selection of high-order harmonics having the same helicity much easier. This is important for applications (for example, for generation of attosecond pulse trains of circularly polarized harmonics).

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    A. V. Kudryavtsev

    2016-09-01

    Full Text Available 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.

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

    Science.gov (United States)

    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.

  14. Efficient second-harmonic generation and modal dispersion effects in orientation-patterned GaAs waveguides.

    Science.gov (United States)

    Oron, M B; Pearl, S; Blau, P; Shusterman, S

    2010-08-15

    Efficient second-harmonic conversion of 4 microm radiation was demonstrated in orientation-patterned GaAs (OPGaAs) waveguides (WGs). An experimentally corrected phase-matching curve for second harmonic generation (SHG) in OPGaAs WGs is presented. Influence of WG modes on the SHG process was studied. Two distinct types of SHG in the waveguides were identified and related to the TE and TM modes. Each type has its own dependence on pump polarization. The 21% W(-1) normalized conversion efficiency is within a factor of 0.75 from the predicted value for an ideal WG.

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

    DEFF Research Database (Denmark)

    Simesen, Paw; Søndergaard, Thomas; Skovsen, Esben

    2015-01-01

    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...

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

    Science.gov (United States)

    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.

  17. Attosecond dynamics of light-induced resonant hole transfer in high-order-harmonic generation

    Science.gov (United States)

    You, Jhih-An; Dahlström, Jan Marcus; Rohringer, Nina

    2017-02-01

    We present a study of high-order-harmonic generation (HHG) assisted by extreme ultraviolet (XUV) attosecond pulses, which can lead to the excitation of inner-shell electrons and the generation of a second HHG plateau. With the treatment of a one-dimensional model of krypton, based on time-dependent configuration interaction singles (TDCIS) of an effective two-electron system, we show that the XUV-assisted HHG spectrum reveals the duration of the semiclassical electron trajectories. The results are interpreted by the strong-field approximation (SFA) and the importance of the hole transfer during the tunneling process is emphasized. Finally, coherent population transfer between the inner and outer holes with attosecond pulse trains is discussed.

  18. Tunable orbital angular momentum in high-harmonic generation.

    Science.gov (United States)

    Gauthier, D; Ribič, P Rebernik; Adhikary, G; Camper, A; Chappuis, C; Cucini, R; DiMauro, L F; Dovillaire, G; Frassetto, F; Géneaux, R; Miotti, P; Poletto, L; Ressel, B; Spezzani, C; Stupar, M; Ruchon, T; De Ninno, G

    2017-04-05

    Optical vortices are currently one of the most intensively studied topics in optics. These light beams, which carry orbital angular momentum (OAM), have been successfully utilized in the visible and infrared in a wide variety of applications. Moving to shorter wavelengths may open up completely new research directions in the areas of optical physics and material characterization. Here, we report on the generation of extreme-ultraviolet optical vortices with femtosecond duration carrying a controllable amount of OAM. From a basic physics viewpoint, our results help to resolve key questions such as the conservation of angular momentum in highly nonlinear light-matter interactions, and the disentanglement and independent control of the intrinsic and extrinsic components of the photon's angular momentum at short-wavelengths. The methods developed here will allow testing some of the recently proposed concepts such as OAM-induced dichroism, magnetic switching in organic molecules and violation of dipolar selection rules in atoms.

  19. Optimization of multi-color laser waveform for high-order harmonic generation

    Science.gov (United States)

    Jin, Cheng; Lin, C. D.

    2016-09-01

    With the development of laser technologies, multi-color light-field synthesis with complete amplitude and phase control would make it possible to generate arbitrary optical waveforms. A practical optimization algorithm is needed to generate such a waveform in order to control strong-field processes. We review some recent theoretical works of the optimization of amplitudes and phases of multi-color lasers to modify the single-atom high-order harmonic generation based on genetic algorithm. By choosing different fitness criteria, we demonstrate that: (i) harmonic yields can be enhanced by 10 to 100 times, (ii) harmonic cutoff energy can be substantially extended, (iii) specific harmonic orders can be selectively enhanced, and (iv) single attosecond pulses can be efficiently generated. The possibility of optimizing macroscopic conditions for the improved phase matching and low divergence of high harmonics is also discussed. The waveform control and optimization are expected to be new drivers for the next wave of breakthrough in the strong-field physics in the coming years. Project supported by the Fundamental Research Funds for the Central Universities of China (Grant No. 30916011207), Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U. S. Department of Energy (Grant No. DE-FG02-86ER13491), and Air Force Office of Scientific Research, USA (Grant No. FA9550-14-1-0255).

  20. Probing multirescattering dynamics and electron quantum paths for below- and near-threshold harmonic generation of H2 in an intense laser field

    Science.gov (United States)

    Heslar, John; Chu, Shih-I.

    2017-04-01

    Most previous studies of high-order-harmonic generation have focused on the regime beyond the ionization threshold; the dynamical origin of below- and near-threshold harmonics, particularly for the molecular systems, is less understood and largely unexplored. Here, we report a self-interaction free time-dependent density-functional-theory study along with an extended semiclassical study for the nonperturbative probing of the dynamical origin of below- and near-threshold harmonic generation of the H2 molecule in an intense near-infrared laser field. Our approach allows an accurate study of the electron trajectories as a function of energy, time, and position for below-, near-, and above-threshold harmonics for electrons departing initially from each of the individual hydrogen cores of the H2 molecule. We discover that short trajectories are multiphoton dominated and can have multiple returns for below-threshold harmonics, and excited-state resonances can have significant effects on the generation of neighboring below-threshold harmonics. Furthermore, we find that the electron dynamics for below-threshold long, short, and resonant trajectories differ greatly depending upon which hydrogen core (left or right) the electron was released from initially. An intuitive and appealing picture of near- and below-threshold harmonic generation discovered in our study can give guidance to future experiments in this forefront area of ultrafast atomic, molecular, and optical physics.

  1. Extreme Ultraviolet Fractional Orbital Angular Momentum Beams from High Harmonic Generation

    Science.gov (United States)

    Turpin, Alex; Rego, Laura; Picón, Antonio; San Román, Julio; Hernández-García, Carlos

    2017-03-01

    We investigate theoretically the generation of extreme-ultraviolet (EUV) beams carrying fractional orbital angular momentum. To this end, we drive high-order harmonic generation with infrared conical refraction (CR) beams. We show that the high-order harmonic beams emitted in the EUV/soft x-ray regime preserve the characteristic signatures of the driving beam, namely ringlike transverse intensity profile and CR-like polarization distribution. As a result, through orbital and spin angular momentum conservation, harmonic beams are emitted with fractional orbital angular momentum, and they can be synthesized into structured attosecond helical beams -or “structured attosecond light springs”- with rotating linear polarization along the azimuth. Our proposal overcomes the state of the art limitations for the generation of light beams far from the visible domain carrying non-integer orbital angular momentum and could be applied in fields such as diffraction imaging, EUV lithography, particle trapping, and super-resolution imaging.

  2. High-order harmonic generation from polyatomic molecules including nuclear motion and a nuclear modes analysis

    DEFF Research Database (Denmark)

    Madsen, Christian Bruun; Abu-Samha, Mahmoud; Madsen, Lars Bojer

    2010-01-01

    as a nuclear correlation function. We express the nuclear correlation function in terms of Franck-Condon factors, which allows us to decompose nuclear motion into modes and identify the modes that are dominant in the high-order harmonic generation process. We show results for the isotopes CH4 and CD4......We present a generic approach for treating the effect of nuclear motion in high-order harmonic generation from polyatomic molecules. Our procedure relies on a separation of nuclear and electron dynamics where we account for the electronic part using the Lewenstein model and nuclear motion enters...... and thereby provide direct theoretical support for a recent experiment [S. Baker et al., Science 312, 424 (2006)] that uses high-order harmonic generation to probe the ultrafast structural nuclear rearrangement of ionized methane....

  3. Extreme Ultraviolet Fractional Orbital Angular Momentum Beams from High Harmonic Generation.

    Science.gov (United States)

    Turpin, Alex; Rego, Laura; Picón, Antonio; San Román, Julio; Hernández-García, Carlos

    2017-03-10

    We investigate theoretically the generation of extreme-ultraviolet (EUV) beams carrying fractional orbital angular momentum. To this end, we drive high-order harmonic generation with infrared conical refraction (CR) beams. We show that the high-order harmonic beams emitted in the EUV/soft x-ray regime preserve the characteristic signatures of the driving beam, namely ringlike transverse intensity profile and CR-like polarization distribution. As a result, through orbital and spin angular momentum conservation, harmonic beams are emitted with fractional orbital angular momentum, and they can be synthesized into structured attosecond helical beams -or "structured attosecond light springs"- with rotating linear polarization along the azimuth. Our proposal overcomes the state of the art limitations for the generation of light beams far from the visible domain carrying non-integer orbital angular momentum and could be applied in fields such as diffraction imaging, EUV lithography, particle trapping, and super-resolution imaging.

  4. A way for studying the impact of PEDOT:PSS interface layer on carrier transport in PCDTBT:PC{sub 71}BM bulk hetero junction solar cells by electric field induced optical second harmonic generation measurement

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Zubair, E-mail: zubairtarar@um.edu.my; Abdullah, Shahino Mah; Sulaiman, Khaulah [Low Dimensional Materials Research Centre (LDMRC), Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Taguchi, Dai; Iwamoto, Mitsumasa [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 O-Okayama, Meguro-ku, Tokyo 152-8552 (Japan)

    2015-04-28

    Electric-field-induced optical second-harmonic generation (EFISHG) measurement was employed to study the impact of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS) interface layer on the carrier transport mechanism of the PCDTBT:PC{sub 71}BM bulk heterojunction (BHJ) organic solar cells (OSCs). We revealed that the electric fields in the PCDTBT and PC{sub 71}BM were allowed to be measured individually by choosing fundamental laser wavelengths of 1000 nm and 1060 nm, respectively, in dark and under illumination. The results showed that the direction of the internal electric fields in the PCDTBT:PC{sub 71}BM BHJ layer is reversed by introducing the PEDOT:PSS layer, and this results in longer electron transport time in the BHJ layer. We conclude that TR-EFISHG can be used as a novel way for studying the impact of interfacial layer on the transport of electrons and holes in the bulk-heterojunction OSCs.

  5. On second-harmonic generation in nonuniformly magnetized media

    Science.gov (United States)

    Karashtin, E. A.

    2017-11-01

    This paper presents a theoretical study of new effects of double-frequency optical signal generation in magnetic media with a nonuniform magnetization distribution. The study is based on the hydrodynamic approximation of the motion of conduction electrons in the field of an electromagnetic wave and equations for the mean electron spin. Within this approach, the mechanisms of the toroidal moment effect, which was experimentally discovered earlier in a system of magnetic particles with a vertical magnetization distribution as well as in a multilayered magnetic system (which is a collinear nonuniform magnetic system), are demonstrated. A new effect that appears due to the presence of equilibrium spin currents in a nonuniform magnetic system is studied in detail. This effect was predicted from the symmetry and can occur only in noncollinearly magnetized media. It is shown that this effect has a resonance nature with a resonance at a pump frequency equal to the plasma frequency of conduction electrons. Estimates of the susceptibility at the double frequency for the parameters of nickel and the typical scale of variation in the magnetization, which is equal to 10 nm, show that the susceptibility near the frequency of the plasma resonance at the chosen parameters is on the order of 10-9 esu, which holds up a hope of the experimental detection of this effect.

  6. Stator Current Harmonic Reduction in a Novel Half Quasi-Z-Source Wind Power Generation System

    Directory of Open Access Journals (Sweden)

    Shoudao Huang

    2016-09-01

    Full Text Available The generator stator current gets distorted with unacceptable levels of total harmonic distortion (THD because impedance-source wind power generation systems use three-phase diode rectifiers. The stator current harmonics will cause increasing losses and torque ripple, which reduce the efficiency and stability of the system. This paper proposes a novel half quasi-Z-source inverter (H-qZSI for grid-connected wind power generation systems, which can reduce the generator stator current harmonics a great deal. When H-qZSI operates in the shoot-through zero state, the derivative of the generator stator current is only determined by the instantaneous value of the generator stator voltage, so the nonlinear relationship between generator stator current and stator voltage is improved compared with the traditional impedance-source inverter. Theoretically, it is indicated that the stator current harmonics can be reduced effectively by means of the proposed H-qZSI. Finally, simulation and experimental results are given to verify the theoretical analysis.

  7. Data harmonization and federated analysis of population-based studies: the BioSHaRE project.

    Science.gov (United States)

    Doiron, Dany; Burton, Paul; Marcon, Yannick; Gaye, Amadou; Wolffenbuttel, Bruce H R; Perola, Markus; Stolk, Ronald P; Foco, Luisa; Minelli, Cosetta; Waldenberger, Melanie; Holle, Rolf; Kvaløy, Kirsti; Hillege, Hans L; Tassé, Anne-Marie; Ferretti, Vincent; Fortier, Isabel

    2013-11-21

    Individual-level data pooling of large population-based studies across research centres in international research projects faces many hurdles. The BioSHaRE (Biobank Standardisation and Harmonisation for Research Excellence in the European Union) project aims to address these issues by building a collaborative group of investigators and developing tools for data harmonization, database integration and federated data analyses. Eight population-based studies in six European countries were recruited to participate in the BioSHaRE project. Through workshops, teleconferences and electronic communications, participating investigators identified a set of 96 variables targeted for harmonization to answer research questions of interest. Using each study's questionnaires, standard operating procedures, and data dictionaries, harmonization potential was assessed. Whenever harmonization was deemed possible, processing algorithms were developed and implemented in an open-source software infrastructure to transform study-specific data into the target (i.e. harmonized) format. Harmonized datasets located on server in each research centres across Europe were interconnected through a federated database system to perform statistical analysis. Retrospective harmonization led to the generation of common format variables for 73% of matches considered (96 targeted variables across 8 studies). Authenticated investigators can now perform complex statistical analyses of harmonized datasets stored on distributed servers without actually sharing individual-level data using the DataSHIELD method. New Internet-based networking technologies and database management systems are providing the means to support collaborative, multi-center research in an efficient and secure manner. The results from this pilot project show that, given a strong collaborative relationship between participating studies, it is possible to seamlessly co-analyse internationally harmonized research databases while allowing

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

    Science.gov (United States)

    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.

  9. Green bright squeezed light from a cw periodically poled KTP second harmonic generator

    DEFF Research Database (Denmark)

    Andersen, Ulrik Lund; Buchhave, Preben

    2002-01-01

    We present the experimental observation of bright amplitude squeezed light from a singly resonant second harmonic generator (SHG) based on a periodically poled potassium titanyl phosphate (KTP) crystal. Contrary to conventional SHG, the interacting waves in this device couple efficiently using...... quasi phase matching (QPM) and more importantly QPM allows access to higher valued elements of the nonlinear tensor than is possible under the constraint of birefringence phase matching. We observe a noise reduction of 13% below the shot noise limit in the generated second harmonic field. This noise...

  10. Coherent hard x rays from attosecond pulse train-assisted harmonic generation.

    Science.gov (United States)

    Klaiber, Michael; Hatsagortsyan, Karen Z; Müller, Carsten; Keitel, Christoph H

    2008-02-15

    High-order harmonic generation from atomic systems is considered in the crossed fields of a relativistically strong infrared laser and a weak attosecond pulse train of soft x rays. Due to one-photon ionization by the x-ray pulse, the ionized electron obtains a starting momentum that compensates the relativistic drift, which is induced by the laser magnetic field, and allows the electron to efficiently emit harmonic radiation upon recombination with the atomic core in the relativistic regime. This way, short pulses of coherent hard x rays of up to 40 keV energy can be generated.

  11. Fourth-harmonic generation of picosecond glass laser pulses with cesium lithium borate crystals

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, L.B.; Daido, H.; Kato, Y.; Nakai, S. [Institute of Laser Engineering, Osaka University, 2-6, Yamada-Oka, Suita 565 (Japan); Zhang, T. [Yamanashi University, Faculty of Engineering, 4-3-11 Takeda, Kofu, Yamanashi 400 (Japan); Mori, Y.; Sasaki, T. [Department of Electrical Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565 (Japan)

    1996-12-01

    We report the fourth-harmonic generation of 1.5 ps, 1.053 {mu}m glass laser pulses, where group velocity mismatch plays a significant role, at intensities up to 100 GW/cm{sup 2} using newly developed crystal, cesium lithium borate (CsLiB{sub 6}O{sub 10}). Type-I doubler and type-I quadrupler were used in the fourth harmonic generation experimental scheme. Energy conversion efficiencies of 24{percent} and 53{percent} have been achieved for frequency quadrupling and doubling of the fundamental glass laser pulses, respectively. {copyright} {ital 1996 American Institute of Physics.}

  12. Tunable High Harmonic Generation driven by a Visible Optical Parametric Amplifier

    Directory of Open Access Journals (Sweden)

    Keathley P.

    2013-03-01

    Full Text Available We studied high-harmonic generation (HHG in Ar, Ne and He gas jets using a broadly tunable, high-energy optical parametric amplifier (OPA in the visible wavelength range. We optimized the noncollinear OPA to deliver tunable, femtosecond pulses with 200-500 μJ energy at 1-kHz repetition rate with excellent spatiotemporal properties, suitable for HHG experiments. By tuning the central wavelength of the OPA while keeping energy, duration and beam size constant, we experimentally studied the scaling law of conversion efficiency and cut-off energy with the driver wavelength in argon and helium respectively. Our measurements show a λ−5.9±0.9 wavelength dependence of the conversion efficiency and a λ1.7±0.2 dependence of the HHG cut-off photon energy over the full visible range in agreement with previous experiments of near- and mid-IR wavelengths. By tuning the central wavelength of the driver source and changing the gas, the high order harmonic spectra in the extreme ultraviolet cover the full range of photon energy between ~25 eV and ~100 eV. Due to the high coherence intrinsic in HHG, as well as the broad and continuous tunability in the extreme UV range, a high energy, high repetition rate version of this source might be an ideal seed for free electron lasers.

  13. Revisiting the boundary conditions for second-harmonic generation at metal-dielectric interfaces

    Science.gov (United States)

    Nireekshan Reddy, K.; Chen, Parry Y.; Fernández-Domínguez, Antonio I.; Sivan, Yonatan

    2017-09-01

    We study second-harmonic generation (SHG) arising from surface nonlinearity at a metal-dielectric interface using a spectral decomposition method. Since our method avoids the need to consider the generalized boundary condition across the metal-dielectric interface in the presence of a perpendicular surface source, we retrieve the known discontinuity of the tangential component of the electric field ($E_{\\parallel}^ {2\\omega}$) for a general geometry, based on a purely mathematical argument. Further, we reaffirm the standard convention of the implementation of this condition, namely, that the surface dipole source radiates as if placed outside the metal surface for arbitrary geometries. We also study and explain the spectral dependence of the discontinuity of the tangential component of the electric field at second harmonic. Finally, we note that the default settings of the commercial numerical package COMSOL Multiphysics fail to account for the $E_{\\parallel}^ {2\\omega}$-discontinuity. We provide a simple recipe that corrects the boundary condition within these existing settings.

  14. Investigating the origin of third harmonic generation from diabolo optical antennas

    Science.gov (United States)

    Shi, Liping; Andrade, José R. C.; Kim, Hyunwoong; Han, Seunghwoi; Nicolas, Rana; Franz, Dominik; Boutu, Willem; Heidenblut, Torsten; Segerink, Frans B.; Bastiaens, Bert; Merdji, Hamed; Kim, Seung-Woo; Morgner, Uwe; Kovačev, Milutin

    2017-10-01

    We propose to use diabolo nanoantennas for experimentally investigating the origin of the enhanced third harmonic generation by localized surface plasmon polaritons. In such a geometry, the opposing apexes of bowties are electrically connected by a thin gold nanorod, which has two important functions in discriminating the point of harmonic generation. First, the inserted gold nanorod shifts the field enhancement area to be far away from the dielectric substrate material. Next, the accumulation of free charges at the adjacent bowtie tips produces a strong electric field inside the gold nanorod. The diabolo nanoantennas allow us to examine the contribution of the bare gold susceptibility to the third harmonic conversion. Our results reveal that the bare gold does not significantly enhance the harmonic generation at high pump intensity. From this, we deduce that in regular bowtie antennas, the enhanced harmonic photons mainly arise from the substrate sapphire that is located in the feedgap of the bowtie, where the electric near-field is significantly enhanced by the localized surface plasmons.

  15. High harmonics generation at the interaction of an intense fs laser pulse with an overdense plasma layer

    Science.gov (United States)

    Mihailescu, A.; Stancalie, V.; Pais, V.

    2014-04-01

    Harmonics generated with fs laser pulses are not only among the most intense sources in the wavelength range of a few tens of nanometers but also a far better source than X-ray lasers from the coherence point of view. It is anticipated, that in the near future, the harmonics issued from femtosecond laser-produced plasmas will represent a coherent source much brighter than all other XUV sources apart from the XFEL. These particular aspects, correlated with the fact that high order harmonics produced by reflection of an ultrashort and intense laser pulse on an overdense plasma layer impose virtually no restrictions on the intensity of the laser employed, lead the way to a series of potential applications in plasma diagnostics and nonlinear optics. This work presents a theoretical study on the high harmonics generation mechanism occurring at the reflection of a femtosecond Ti-Sapphire terawatt laser pulse (λ0 = 0.8 μm and pulse durations around 100-150 fs) on an overdense steep Al plasma layer. Insights on how different laser parameters influence this generation mechanism and its efficiency are provided.

  16. Is rigorous retrospective harmonization possible? Application of the DataSHaPER approach across 53 large studies

    NARCIS (Netherlands)

    Fortier, Isabel; Doiron, Dany; Little, Julian; Ferretti, Vincent; L'Heureux, Francois; Stolk, Ronald P.; Knoppers, Bartha M.; Hudson, Thomas J.; Burton, Paul R.

    2011-01-01

    Methods This article examines the value of using the DataSHaPER for retrospective harmonization of established studies. Using the DataSHaPER approach, the potential to generate 148 harmonized variables from the questionnaires and physical measures collected in 53 large population-based studies (6.9

  17. Sensitivity of echo enabled harmonic generation to sinusoidal electron beam energy structure

    Directory of Open Access Journals (Sweden)

    E. Hemsing

    2017-06-01

    Full Text Available We analytically examine the bunching factor spectrum of a relativistic electron beam with sinusoidal energy structure that then undergoes an echo-enabled harmonic generation (EEHG transformation to produce high harmonics. The performance is found to be described primarily by a simple scaling parameter. The dependence of the bunching amplitude on fluctuations of critical parameters is derived analytically, and compared with simulations. Where applicable, EEHG is also compared with high gain harmonic generation (HGHG and we find that EEHG is generally less sensitive to several types of energy structure. In the presence of intermediate frequency modulations like those produced by the microbunching instability, EEHG has a substantially narrower intrinsic bunching pedestal.

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

    Science.gov (United States)

    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.

  19. Generating harmonized SUV within the EANM EARL accreditation program: software approach versus EARL-compliant reconstruction.

    Science.gov (United States)

    Lasnon, Charline; Salomon, Thibault; Desmonts, Cédric; Dô, Pascal; Oulkhouir, Youssef; Madelaine, Jeannick; Aide, Nicolas

    2017-02-01

    Evolutions in hardware and software PET technology, such as point spread function (PSF) reconstruction, have been shown to improve diagnostic performance, but can also lead to important device-dependent and reconstruction-dependent variations in standardized uptake values (SUVs). This may preclude the multicentre use of SUVs as a prognostic or diagnostic tool or as a biomarker of the early response to antineoplastic treatments. This study compared two SUV harmonization strategies using a newer reconstruction algorithm that improves lesion detection while maintaining comparability with older systems: (1) the use of a second reconstruction compliant with harmonization standards and (2) the use of a proprietary software tool (EQ.PET). PET data from 50 consecutive non-small cell lung cancer patients were reconstructed with PSF reconstruction for optimal tumor detection and an ordered subset expectation maximization (OSEM3D) reconstruction to mimic a former generation PET. An additional PSF reconstruction was performed with a 7 mm Gaussian filter (PSF7, first method), and, post-reconstruction, the EQ filter (same Gaussian filter) was applied to the PSF data (PSFEQ, second method) for harmonization purposes. The 7 mm kernel filter was chosen to comply with the European Association of Nuclear Medicine (EANM) standards. SUVs for all reconstructions were compared with regression analyses and/or Bland-Altman plots. Overall, 171 lesions were analyzed: 55 lung lesions (32.2%), 87 lymph nodes (50.9%), and 29 metastases (16.9%). In these lesions, the mean PSF7/OSEM3D ratios for SUVmax and SUVpeak were 1.02 (95% CI: 0.93-1.11) and 1.04 (95% CI: 0.95-1.14), respectively. The mean PSFEQ/OSEM3D ratios for SUVmax and SUVpeak were 1.01 (95% CI: 0.91-1.11) and 1.04 (95% CI: 0.94-1.14), respectively. When comparing PSF7 and PSFEQ, Bland-Altman analysis showed that the mean PSF7/PSFEQ ratios for SUVmax and SUVpeak were 1.01 (95% CI: 0.96-1.06) and 1.01 (95% CI: 0.97-1.04), respectively

  20. Contactless Characterization of Carrier Injection and Recombination Processes at Semiconductor Interfaces Using Second-Harmonic Generation

    Science.gov (United States)

    Pasternak, R.; Shirokaya, Y. V.; Marka, Z.; Miller, J. K.; Rashkeev, S. N.; Pantelides, S. T.; Tolk, N. H.; Choi, B. K.; Fleetwood, D. M.; Schrimpf, R. D.

    2003-03-01

    Leakage currents can be significantly enhanced in MOS devices by exposure to ionizing radiation. We have demonstrated that second-harmonic generation (SHG) is a useful technique for the characterization of carrier transport in X-ray damaged ultra-thin oxides. Our results show also that this technique is more sensitive to the detection of damage in thin oxide films than conventional electrical measurement approaches. Using this technique which we have designated Laser Interrogated Leakage Current (LILC), we have performed time-dependent measurements, which provide dynamical information about injection, trapping, detrapping, transport and recombination processes in thin layers of SiO2 on Si. In addition, we have shown for the first time that optical SHG measurements can be performed effectively on an oxide sample with a gradually varying thickness (from 1 nm to 6.5 nm) which cannot be studied by conventional electronic measurements.

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

    Science.gov (United States)

    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.

  2. Spectral Phase Modulation and chirped pulse amplification in High Gain Harmonic Generation

    CERN Document Server

    Wu, Zilu; Krinsky, Sam; Loos, Henrik; Murphy, James; Shaftan, Timur; Sheehy, Brian; Shen, Yuzhen; Wang, Xijie; Yu Li Hua

    2004-01-01

    High Gain Harmonic Generation (HGHG), because it produces longitudinally coherent pulses derived from a coherent seed, presents remarkable possibilities for manipulating FEL pulses. If spectral phase modulation imposed on the seed modulates the spectral phase of the HGHG in a deterministic fashion, then chirped pulse amplification, pulse shaping, and coherent control experiments at short wavelengths become possible. In addition, the details of the transfer function will likely depend on electron beam and radiator dynamics and so prove to be a useful tool for studying these. Using the DUVFEL at the National Synchrotron Light Source at Brookhaven National Laboratory, we present spectral phase analyses of both coherent HGHG and incoherent SASE ultraviolet FEL radiation, applying Spectral Interferometry for Direct Electric Field Reconstruction (SPIDER), and assess the potential for employing compression and shaping techniques.

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

    Energy Technology Data Exchange (ETDEWEB)

    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 %.

  4. Cerenkov second-harmonic generation in the strong conversion limit: New effects

    NARCIS (Netherlands)

    Krijnen, Gijsbertus J.M.; Hoekstra, Hugo; Stegeman, George I.; Torruellas, William

    1996-01-01

    Using beam propagation method calculations, we show that new effects occur for second-harmonic generation in the Čerenkov regime when it is optimized for efficient coupling to leaky modes. The fundamental throughput becomes independent of the input power over a few decades; i.e., optical power

  5. Third harmonic generation of CO2 laser radiation in AgGaSe2 crystal

    Indian Academy of Sciences (India)

    September 2000 physics pp. 405–412. Third harmonic generation of CO2 laser radiation in. AgGaSe2 crystal. GOPAL C BHAR, PATHIK KUMBHAKAR. ½. , D V SATYANARAYANA. ¾. ,. N S N BANERJEE. ¾. , U NUNDY. ¾ and C G CHAO. ¿. Laser Laboratory, Physics Department, Burdwan University, Burdwan 713 104, ...

  6. Plasmonic enhancement of High Harmonic Generation revisited: Predominance of Atomic Line Emission

    Directory of Open Access Journals (Sweden)

    Ropers C.

    2013-03-01

    Full Text Available We demonstrate nanostructure-enhanced extreme ultraviolet fluorescence from noble gases driven by low-energy, few-cycle light pulses. Despite sufficient local intensities, plasmon-enhanced high harmonic generation is not observed, which follows from the small, nanometer-size coherent source volume.

  7. In vivo optical virtual biopsy of human oral cavity with harmonic generation microscopy

    Science.gov (United States)

    Tsai, M.-R.; Chen, S.-Y.; Shieh, D.-B.; Lou, P.-J.; Sun, C.-K.

    2010-02-01

    Oral cancer ranked number four in both cancer incident and mortality in Taiwanese male population. Early disease diagnosis and staging is essential for its clinical success. However, most patients were diagnosed in their late disease stage as ideal prescreening procedures are yet to be developed especially when dealing with a large surface of precancerous lesions. Therefore, how to detect and confirm the diagnosis of these early stage lesions are of significant clinical value. Harmonic generation process naturally occurred in biological molecules and requires no energy deposition to the target molecule. Thus harmonic generation microscopy (HGM) could potentially serve as a noninvasive tool for screening of human oral mucosal diseases. The in vivo optical biopsy of human oral cavity with HGM could be achieved with high spatial resolution to resolve dynamic physiological process in the oral mucosal tissue with equal or superior quality but devoid of complicated physical biopsy procedures. The second harmonic generation (SHG) provide significant image contrast for biomolecules with repetitive structures such as the collagen fibers in the lamina propria and the mitotic spindles in dividing cells. The cell morphology in the epithelial layer, blood vessels and blood cells flow through the capillaries can be revealed by third harmonic generation (THG) signals. Tissue transparent technology was used to increase the optical penetration of the tissue. In conclusion, this report demonstrates the first in vivo optical virtual biopsy of human oral mucosa using HGM and revealed a promising future for its clinical application for noninvasive in vivo diseases diagnosis.

  8. Investigating the origin of third harmonic generation from diabolo optical antennas

    NARCIS (Netherlands)

    Shi, Liping; Andrade, J.R.; Kim, Hyunwoong; Han, S.; Nicolas, Rana; Franz, Dominik; Boutu, Willem; Heidenblut, Torsten; Segerink, F.B.; Bastiaens, Hubertus M.J.; Merdji, Hamed; Kim, Seung-Woo; Morgner, Uwe; Kovacev, M.

    2017-01-01

    We propose to use diabolo nanoantennas for experimentally investigating the origin of the enhanced third harmonic generation by localized surface plasmon polaritons. In such a geometry, the opposing apexes of bowties are electrically connected by a thin gold nanorod, which has two important

  9. Optical generation of a circular harmonic filter for rotation and translation invariant optical pattern recognition

    Science.gov (United States)

    Cheng, Yeou-Yen

    1987-01-01

    A new method to generate a circular harmonic filter with both rotation and translation invariance is described, which is based on a phase-shifted double-exposure (PSDE) technique. An expression for the peak correlation intensity at the origin for the correlation plane as a function of target orientation for the PSDE filter is derived. Experimental results confirming the theoretical predictions are provided.

  10. High harmonic generation in H2 and HD by two-colour femtosecond ...

    Indian Academy of Sciences (India)

    bonding molecular orbital (MO) [36], and the harmonics are generated by the nuclear motions on the two lowest ... strongly suppresses the long electronic trajectories, due to the rapidly decaying behaviour of the (vibrational) autocorrelation function ... free electron trajectory loses its relevance. Thus, from this viewpoint also, ...

  11. Second-Harmonic Generation Scanning Microscopy on Domains in Al Surfaces

    DEFF Research Database (Denmark)

    Pedersen, Kjeld; Bozhevolnyi, Sergey I.

    1999-01-01

    Scanning optical second-harmonic generation microscopy has been used to investigate domains in the surface of polycrystaline Al. Strong contrast among the crystalline grains is obtained due to variations in their crystallographic orientations and thus also nonlinear response. The origin of the co...

  12. Observation of self-pulsing in singly resonant optical second-harmonic generation with competing nonlinearities

    DEFF Research Database (Denmark)

    Bache, Morten; Lodahl, Peter; Mamaev, Alexander V.

    2002-01-01

    We predict and experimentally observe temporal self-pulsing in singly resonant intracavity second-harmonic generation under conditions of simultaneous parametric oscillation. The threshold for self-pulsing as a function of cavity tuning and phase mismatch are found from analysis of a three-compon...

  13. High harmonic generation in H2 and HD by two-colour femtosecond ...

    Indian Academy of Sciences (India)

    We have taken the pulse duration of T = 50 fs for both the fields, and the molecular initial vibrational level 0 = 0. We have argued that for these combinations, the harmonic generation due to transitions in the electronic continuum by tunnelling or multiphoton ionization may be neglected and only the electronic transitions ...

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

    DEFF Research Database (Denmark)

    Saravi, Sina; Quintero-Bermudez, Rafael; Setzpfandt, Frank

    2016-01-01

    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 maxima...

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

    Energy Technology Data Exchange (ETDEWEB)

    Trull, J.; Wang, B.; Parra, A.; Vilaseca, R.; Cojocaru, C. [Departament de Física i Enginyeria Nuclear, Universitat Politècnica Catalunya, Terrassa 08222 (Spain); Sola, I. [Grupo de Investigación en Óptica Extrema (GIOE), Departamento de Física Aplicada, Universidad de Salamanca, Plaza de la Merced s/n, 37008 Salamanca (Spain); Krolikowski, W. [Laser Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia); Science Program, Texas A and M University at Qatar, Doha (Qatar); Sheng, Y. [Laser Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

    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.

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

    Science.gov (United States)

    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.

  17. Ultra-broadband Photonic Harmonic Mixer Based on Optical Comb Generation

    DEFF Research Database (Denmark)

    Zhao, Ying; Pang, Xiaodan; Deng, Lei

    2012-01-01

    We propose a novel photonic harmonic mixer operating at frequencies up to the millimeter-wave (MMW) band. By combining a broadband fiber-wireless signal with highorder harmonics of a fundamental local oscillator in an optical frequency comb generator, frequency down-conversion can be implemented...... without using costly ultra-broadband photodiode. It is theoretically shown that the down-conversion efficiency and the bandwidth of the mixer is highly dependent on the optical modulation indices and the fundamental frequency of comb lines. Down-conversion of a W-band (75-110GHz) fiberwireless signal...

  18. Coherent hard x-rays from attosecond pulse train-assisted harmonic generation

    OpenAIRE

    Klaiber, Michael; Hatsagortsyan, Karen Z.; Müller, Carsten; Keitel, Christoph H.

    2007-01-01

    High-order harmonic generation from atomic systems is considered in the crossed fields of a relativistically strong infrared laser and a weak attosecond-pulse train of soft x-rays. Due to one-photon ionization by the x-ray pulse, the ionized electron obtains a starting momentum that compensates the relativistic drift which is induced by the laser magnetic field, and allows the electron to efficiently emit harmonic radiation upon recombination with the atomic core in the relativistic regime. I...

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

    Science.gov (United States)

    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

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

    Directory of Open Access Journals (Sweden)

    Fong Gloria

    2011-01-01

    Full Text Available Abstract 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

  1. Opportunities for chiral discrimination using high harmonic generation in tailored laser fields

    CERN Document Server

    Smirnova, Olga; Patchkovskii, Serguei

    2015-01-01

    Chiral discrimination with high harmonic generation (cHHG method) has been introduced in the recent work by R. Cireasa et al ( Nat. Phys. 11, 654 - 658, 2015). In its original implementation, the cHHG method works by detecting high harmonic emission from randomly oriented ensemble of chiral molecules driven by elliptically polarized field, as a function of ellipticity. Here we discuss future perspectives in the development of this novel method, the ways of increasing chiral dichroism using tailored laser pulses, new detection schemes involving high harmonic phase measurements, and concentration-independent approaches. Using the example of the epoxypropane molecule C$_3$H$_6$O (also known as 1,2-propylene oxide), we show theoretically that application of two-color counter-rotating elliptically polarized laser fields yields an order of magnitude enhancement of chiral dichroism compared to single color elliptical fields. We also describe how one can introduce a new functionality to cHHG: concentration-independen...

  2. Carrier-wave Rabi-flopping signatures in high-order harmonic generation for alkali atoms.

    Science.gov (United States)

    Ciappina, M F; Pérez-Hernández, J A; Landsman, A S; Zimmermann, T; Lewenstein, M; Roso, L; Krausz, F

    2015-04-10

    We present a theoretical investigation of carrier-wave Rabi flopping in real atoms by employing numerical simulations of high-order harmonic generation (HHG) in alkali species. Given the short HHG cutoff, related to the low saturation intensity, we concentrate on the features of the third harmonic of sodium (Na) and potassium (K) atoms. For pulse areas of 2π and Na atoms, a characteristic unique peak appears, which, after analyzing the ground state population, we correlate with the conventional Rabi flopping. On the other hand, for larger pulse areas, carrier-wave Rabi flopping occurs, and is associated with a more complex structure in the third harmonic. These characteristics observed in K atoms indicate the breakdown of the area theorem, as was already demonstrated under similar circumstances in narrow band gap semiconductors.

  3. Probe of Multi-electron Dynamics in Xenon by Caustics in High Order Harmonic Generation

    CERN Document Server

    Faccialà, Davide; Bruner, Barry D; Ciriolo, Anna G; De Silvestri, Sandro; Devetta, Michele; Negro, Matteo; Soifer, Hadas; Stagira, Salvatore; Dudovich, Nirit; Vozzi, Caterina

    2016-01-01

    We investigated the giant resonance in Xenon by high-order harmonic generation spectroscopy driven by a two-color field. The addition of a non-perturbative second harmonic component parallel to the driving field breaks the symmetry between neighboring sub-cycles resulting in the appearance of spectral caustics at two distinct cut-off energies. By controlling the phase delay between the two color components it is possible to tailor the harmonic emission in order to amplify and isolate the spectral feature of interest. In this paper we demonstrate how this control scheme can be used to investigate the role of electron correlations that give birth to the giant resonance in Xenon. The collective excitations of the giant dipole resonance in Xenon combined with the spectral manipulation associated with the two color driving field allow to see features that are normally not accessible and to obtain a quantitative good agreement between the experimental results and the theoretical predictions.

  4. Carrier-wave Rabi flopping signatures in high-order harmonic generation for alkali atoms

    CERN Document Server

    Ciappina, M F; Landsman, A S; Zimmermann, T; Lewenstein, M; Roso, L; Krausz, F

    2015-01-01

    We present the first theoretical investigation of carrier-wave Rabi flopping in real atoms by employing numerical simulations of high-order harmonic generation (HHG) in alkali species. Given the short HHG cutoff, related to the low saturation intensity, we concentrate on the features of the third harmonic of sodium (Na) and potassium (K) atoms. For pulse areas of 2$\\pi$ and Na atoms, a characteristic unique peak appears, which, after analyzing the ground state population, we correlate with the conventional Rabi flopping. On the other hand, for larger pulse areas, carrier-wave Rabi flopping occurs, and is associated with a more complex structure in the third harmonic. These new characteristics observed in K atoms indicate the breakdown of the area theorem, as was already demonstrated under similar circumstances in narrow band gap semiconductors.

  5. Spatial coherence in high-order-harmonic generation from periodic solid structures

    Science.gov (United States)

    Liu, Lu; Zhao, Jing; Dong, Wenpu; Liu, Jinlei; Huang, Yindong; Zhao, Zengxiu

    2017-11-01

    We theoretically investigate the high-harmonic generation (HHG) from periodical structures driven by an intense laser pulse. Including the full bands, the single electron time-dependent Schrödinger equation is numerically solved in the velocity gauge using Bloch states to obtain the emission spectra. The contributions from different crystal sites are identified using the localized Wannier functions and time-frequency analysis. It is found that the cutoff energy of harmonics is depending on the migration distance of the electron and the instantaneous laser field strength when the electron transports into the related sites. We show that the coherence among different sites during electron propagation is crucial for HHG from solids which can be taken advantage to control the individual site contribution to the certain frequency range of the total harmonic spectra.

  6. X-ray FEL based on harmonics generation and electron beam outcoupling

    Energy Technology Data Exchange (ETDEWEB)

    Litvinenko, V.N.; Burnham, B. [Duke Univ., Durham, NC (United States)

    1995-12-31

    Electron beam outcoupling was suggested by N. A. Vinokurov as a method of optics independent outcoupling for high power FELs. The bunching of the electron beam is provided in a master oscillator. The prebunched electron beam then radiates coherently into an additional wiggler called the radiator. The electron beam is turned by an achromatic bend into this wiggler and its radiation propagates with a small angle with respect to the OK-4 optical axis. Thus, the radiation will pass around the mirror of the master oscillator optical cavity and can then be utilized. This scheme is perfectly suited for harmonic generation if the radiator wiggler is tuned on one of the master oscillator wavelength harmonics. This system is reminiscent of a klystron operating on a harmonic of the reference frequency. In this paper we present the theory of this device, its spectral and spatial characteristics of radiation, the optimization of the master oscillator, the achromatic bend and bunching for harmonic generation, and influence of beam parameters (energy spread, emittance, etc.) on generated power. Examples of possible storage ring and linac driven systems are discussed.

  7. Wannier-Bloch Approach to Localization in High-Harmonics Generation in Solids

    Directory of Open Access Journals (Sweden)

    Edyta N. Osika

    2017-05-01

    Full Text Available Emission of high-order harmonics from solids provides a new avenue in attosecond science. On the one hand, it allows us to investigate fundamental processes of the nonlinear response of electrons driven by a strong laser pulse in a periodic crystal lattice. On the other hand, it opens new paths toward efficient attosecond pulse generation, novel imaging of electronic wave functions, and enhancement of high-order harmonic-generation (HHG intensity. A key feature of HHG in a solid (as compared to the well-understood phenomenon of HHG in an atomic gas is the delocalization of the process, whereby an electron ionized from one site in the periodic lattice may recombine in any other. Here, we develop an analytic model, based on the localized Wannier wave functions in the valence band and delocalized Bloch functions in the conduction band. This Wannier-Bloch approach assesses the contributions of individual lattice sites to the HHG process and hence precisely addresses the question of localization of harmonic emission in solids. We apply this model to investigate HHG in a ZnO crystal for two different orientations, corresponding to wider and narrower valence and conduction bands, respectively. Interestingly, for narrower bands, the HHG process shows significant localization, similar to harmonic generation in atoms. For all cases, the delocalized contributions to HHG emission are highest near the band-gap energy. Our results pave the way to controlling localized contributions to HHG in a solid crystal.

  8. Experimental and simulation studies on the behavior of signal harmonics in magnetic particle imaging.

    Science.gov (United States)

    Murase, Kenya; Konishi, Takashi; Takeuchi, Yuki; Takata, Hiroshige; Saito, Shigeyoshi

    2013-07-01

    Our purpose in this study was to investigate the behavior of signal harmonics in magnetic particle imaging (MPI) by experimental and simulation studies. In the experimental studies, we made an apparatus for MPI in which both a drive magnetic field (DMF) and a selection magnetic field (SMF) were generated with a Maxwell coil pair. The MPI signals from magnetic nanoparticles (MNPs) were detected with a solenoid coil. The odd- and even-numbered harmonics were calculated by Fourier transformation with or without background subtraction. The particle size of the MNPs was measured by transmission electron microscopy (TEM), dynamic light-scattering, and X-ray diffraction methods. In the simulation studies, the magnetization and particle size distribution of MNPs were assumed to obey the Langevin theory of paramagnetism and a log-normal distribution, respectively. The odd- and even-numbered harmonics were calculated by Fourier transformation under various conditions of DMF and SMF and for three different particle sizes. The behavior of the harmonics largely depended on the size of the MNPs. When we used the particle size obtained from the TEM image, the simulation results were most similar to the experimental results. The similarity between the experimental and simulation results for the even-numbered harmonics was better than that for the odd-numbered harmonics. This was considered to be due to the fact that the odd-numbered harmonics were more sensitive to background subtraction than were the even-numbered harmonics. This study will be useful for a better understanding, optimization, and development of MPI and for designing MNPs appropriate for MPI.

  9. Ionization effects on spectral signatures of quantum-path interference in high-harmonic generation.

    Science.gov (United States)

    Holler, M; Zaïr, A; Schapper, F; Auguste, T; Cormier, E; Wyatt, A; Monmayrant, A; Walmsley, I A; Gallmann, L; Salières, P; Keller, U

    2009-03-30

    The interference between the emission originating from the short and long electron quantum paths is intrinsic to the high harmonic generation process. We investigate the universal properties of these quantum-path interferences in various generation media and discuss how ionization effects influence the observed interference structures. Our comparison of quantum-path interferences observed in xenon, argon, and neon demonstrates that our experimental tools are generally applicable and should also allow investigating more complex systems such as molecules or clusters.

  10. Optical second harmonic generation studies of the nature of the oxide-covered and clean c(4 × 4) and (2 × 4) reconstructed GaAs(001) surfaces

    Science.gov (United States)

    Armstrong, S. R.; Hoare, R. D.; Pemble, M. E.; Povey, I. M.; Stafford, A.; Taylor, A. G.; Joyce, B. A.; Neave, J. H.; Zhang, J.

    1993-07-01

    We report the application of the "epioptic" technique of optical second harmonic generation (SHG) to the study of surface chemical processes occurring at the technologically important (001) surfaces of the non-centrosymmetric compound semiconductor GaAs. SHG has been used to monitor the thermal removal of surface contamination from an GaAs(001) substrate mounted in a conventional molecular beam epitaxy (MBE) chamber. Rotational anisotropy plots of the reflected SH signal recorded at near-normal incidence indicate that the oxide layer is not fully disordered and possesses some structural anisotropy, i.e. some preferred net surface orientation. In addition the rotational anisotropy plots were observed to change in both intensity and apparent phase between the oxide-covered surface and the clean reconstructed surfaces. Following heating to 850 K under the background As 2 flux present in the chamber, the SH signal from the clean, reconstructed surface was approximately 5 × weaker than that observed for the contaminated surface and was subsequently found to be insensitive to the reconstruction change between the (2 × 4) and c(4 × 4) surfaces, in agreement with theoretical predictions for surfaces having 2mm and 4mm symmetry, respectively. These data are discussed in terms of the difficulties encountered when attempting to observe a surface SH response from a non-centrosymmetric substrate. The sensitivity of the technique towards the thin oxide overlayer suggests that for overlayers which are likely to possess net oriented in-plane dipoles due to the structural mismatch with the substrate, an SH response may be observed in preference to a bulk response when a normal incidence geometry is employed.

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

    Energy Technology Data Exchange (ETDEWEB)

    Spratt, Kyle S., E-mail: sprattkyle@gmail.com; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hamilton, Mark F. [Applied Research Laboratories, The University of Texas at Austin, P. O. Box 8029, Austin, Texas 78713–8029, US (United States)

    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.

  12. Theoretical investigation of the isolated attosecond pulse generation by restraining the spatial distribution of high-order harmonic emission

    Science.gov (United States)

    Xia, Chang-Long; Liu, Qi-Ying; Miao, Xiang-Yang

    2018-01-01

    Isolated attosecond pulse (IAP) generation is theoretically investigated by using a few-cycle laser pulse from a two-dimensional model of hydrogen molecular ion. The harmonic spectra from two nuclei of hydrogen molecular ion lead to interference. We investigate the spatial distribution in harmonic generation and propose a scheme to restrain the harmonic generation from the nucleus along the positive-x direction, and thus the interference is weaken in spatial. By using a few-cycle 800 nm chirped laser pulse, the harmonics are mainly generated from the nucleus along negative-x direction in the region of 130th to 230th order. The harmonic spectra are smooth and are mainly contributed by the short quantum path near the cutoff region and IAP with a duration of 97 as is generated. The semiclassical of three-step model is also used to illustrate the physical mechanism.

  13. Second and third harmonic generation associated to infrared transitions in a Morse quantum well under applied electric and magnetic fields

    Science.gov (United States)

    Restrepo, R. L.; Kasapoglu, E.; Sakiroglu, S.; Ungan, F.; Morales, A. L.; Duque, C. A.

    2017-09-01

    The effects of electric and magnetic fields on the second and third harmonic generation coefficients in a Morse potential quantum well are theoretically studied. The energy levels and corresponding wave functions are obtained by solving the Schrödinger equation for the electron in the parabolic band scheme and effective mass approximations and the envelope function approach. The results show that both the electric and the magnetic fields have significant influence on the magnitudes and resonant peak energy positions of the second and third harmonic generation responses. In general, the Morse potential profile becomes wider and shallower as γ -parameter increases and so the energies of the bound states will be functions of this parameter. Therefore, we can conclude that the effects of the electric and magnetic fields can be used to tune and control the optical properties of interest in the range of the infrared electromagnetic spectrum.

  14. Organic materials for second harmonic generation. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Twieg, R.J. (comp.)

    1985-03-31

    Materials were chosen by screening the Cambridge Crystallographic Index for new noncentrosymmetric crystalline compounds, by screening commercially available materials or by synthesis of unique new substances. Measurements were then made on the powder form of these materials. Langmuir-Blodgett films were deposited and studied. In addition to the above studies, a computer program was developed to calculate (hyper) polarizabilities of organic molecules and thus aid in the selection of materials for testing. The nonlinear molecules have been divided into three classes according to absorption cutoff: 400 to 500 nm, 300 to 400 nm, and 200 to 300 nm. 108 refs., 7 tabs. (WRF)

  15. Concept for power scaling second harmonic generation using a cascade of nonlinear crystals

    DEFF Research Database (Denmark)

    Hansen, Anders Kragh; Tawfieq, Mahmoud; Jensen, Ole Bjarlin

    2015-01-01

    Within the field of high-power second harmonic generation (SHG), power scaling is often hindered by adverse crystal effects such as thermal dephasing arising from the second harmonic (SH) light, which imposes limits on the power that can be generated in many crystals. Here we demonstrate a concept...... for efficient power scaling of single-pass SHG beyond such limits using a cascade of nonlinear crystals, in which the first crystal is chosen for high nonlinear efficiency and the subsequent crystal(s) are chosen for power handling ability. Using this highly efficient singlepass concept, we generate 3.7 W...... of continuous-wave diffraction-limited 2 ( 1.25) M = light at 532 nm from 9.5 W of non-diffraction-limited 2 ( 7.7) M = light from a tapered laser diode, while avoiding significant thermal effects. Besides constituting the highest SH power yet achieved using a laser diode, this demonstrates that the concept...

  16. Harmonization of initial estimates of shale gas life cycle greenhouse gas emissions for electric power generation.

    Science.gov (United States)

    Heath, Garvin A; O'Donoughue, Patrick; Arent, Douglas J; Bazilian, Morgan

    2014-08-05

    Recent technological advances in the recovery of unconventional natural gas, particularly shale gas, have served to dramatically increase domestic production and reserve estimates for the United States and internationally. This trend has led to lowered prices and increased scrutiny on production practices. Questions have been raised as to how greenhouse gas (GHG) emissions from the life cycle of shale gas production and use compares with that of conventionally produced natural gas or other fuel sources such as coal. Recent literature has come to different conclusions on this point, largely due to differing assumptions, comparison baselines, and system boundaries. Through a meta-analytical procedure we call harmonization, we develop robust, analytically consistent, and updated comparisons of estimates of life cycle GHG emissions for electricity produced from shale gas, conventionally produced natural gas, and coal. On a per-unit electrical output basis, harmonization reveals that median estimates of GHG emissions from shale gas-generated electricity are similar to those for conventional natural gas, with both approximately half that of the central tendency of coal. Sensitivity analysis on the harmonized estimates indicates that assumptions regarding liquids unloading and estimated ultimate recovery (EUR) of wells have the greatest influence on life cycle GHG emissions, whereby shale gas life cycle GHG emissions could approach the range of best-performing coal-fired generation under certain scenarios. Despite clarification of published estimates through harmonization, these initial assessments should be confirmed through methane emissions measurements at components and in the atmosphere and through better characterization of EUR and practices.

  17. Attosecond lighthouse above 100 eV from high-harmonic generation of mid-infrared pulses

    Science.gov (United States)

    Kovács, K.; Negro, M.; Vozzi, C.; Stagira, S.; Tosa, V.

    2017-10-01

    In this paper, we numerically investigate the possibility to obtain a lighthouse emission for the attosecond pulses produced by high-order harmonics of a strong mid-infrared fundamental pulse without any optical element inserted in the path of the generating beam. The parameters of the driving pulse, focusing geometry, gas medium and detection configuration are currently experimentally feasible. Here, we study in detail the specific propagation conditions of the laser beam, and describe the exact mechanism of the sensitive space-time variation of the medium’s refractive index that lead to the dynamic wavefront rotation. This basic requirement for the lighthouse phenomenon is transmitted to the harmonic bursts, which are emitted with different divergence in successive optical half-cycles, thus can be detected in the far field at increasing distances from the optical axis. In this configuration, spectral filtering of the harmonics is not necessary, therefore the total harmonic pulse power might be used in further pump-probe experiments.

  18. Two-chicane compressed harmonic generation of soft x rays

    Directory of Open Access Journals (Sweden)

    Daniel Ratner

    2011-02-01

    Full Text Available Seeding an electron bunch prior to compression simultaneously shifts the laser modulation to shorter wavelengths while decreasing the required modulation amplitude. The final x-ray wavelength is then tunable by controlling the compression factor with the rf phase. In this paper we describe a two-chicane scheme that allows for large modulation amplitudes, extending the method to photocathode beams with significant uncorrelated energy spreads. The downside of such compressed seeding is the need to maintain bunching across an extended accelerator region. We present analytical estimates and computer simulations to study tolerances for a sample lattice. We also note that transportation of the fine compressed modulation structure is helped by error self-correction in the second chicane, an effect that may be of more general interest.

  19. Neck dissection with harmonic scalpel and electrocautery? A randomised study.

    Science.gov (United States)

    Verma, Roshan K; Mathiazhagan, Arulalan; Panda, Naresh K

    2017-10-01

    Is the use of harmonic scalpel for neck dissection useful? Literature search did not show a single, prospective, randomised control trial. We intended to study the role of harmonic scalpel in neck dissection and compare it with conventional electrocautery technique for oral cavity carcinoma. 40 patients undergoing selective neck dissection for primary oral cavity malignancy were enrolled in this study. The harmonic scalpel (HS) group consisted of 20 patients, and the electrocautery technique (ET) group comprised of 20 patients. The following variables were examined: intraoperative blood loss, operative time, number of ligatures used, postoperative drain, and postoperative hospital stay. Intraoperative blood loss was found to be significantly reduced in harmonic scalpel group as compared to electrocautery group. However, we found no difference in other parameters like operative time, postop drain, postoperative hospital stay and number of ligatures used between both groups. Harmonic scalpel for neck dissection is associated with significantly lesser intraoperative blood loss as compared to electrocautery. There is no effect on operative time and postoperative hospital stay in both groups. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  20. Mechanism of equivalent electric dipole oscillation for high-order harmonic generation from grating-structured solid-surface by femtosecond laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yang; Song, Hai-Ying; Liu, H.Y.; Liu, Shi-Bing, E-mail: sbliu@bjut.edu.cn

    2017-07-12

    Highlights: • Proposed a valid mechanism of high harmonic generation by laser grating target interaction: oscillation of equivalent electric dipole (OEED). • Found that there also exist harmonic emission at large emission angle but not just near-surface direction as the former researches had pointed out. • Show the process of the formation and motion of electron bunches at the grating-target surface irradiating with femtosecond laser pulse. - Abstract: We theoretically study high-order harmonic generation (HHG) from relativistically driven overdense plasma targets with rectangularly grating-structured surfaces by femtosecond laser pulses. Our particle-in-cell (PIC) simulations show that, under the conditions of low laser intensity and plasma density, the harmonics emit principally along small angles deviating from the target surface. Further investigation of the surface electron dynamics reveals that the electron bunches are formed by the interaction between the laser field and the target surface, giving rise to the oscillation of equivalent electric-dipole (OEED), which enhances specific harmonic orders. Our work helps understand the mechanism of harmonic emissions from grating targets and the distinction from the planar harmonic scheme.

  1. Nonsequential double-recombination high-order-harmonic generation in molecularlike systems

    Science.gov (United States)

    Hansen, Kenneth K.; Madsen, Lars Bojer

    2017-07-01

    We present a study of nonsequential double-recombination (NSDR) high-harmonic generation (HHG) in a molecularlike system. We have calculated the HHG spectrum for a wide range of internuclear distances, and using a Coulomb-corrected three-step model we are able to analyze and predict the observed NSDR HHG cutoffs precisely for all internuclear distances. It is shown through this Coulomb-corrected three-step (CC-TSM) model that there is an intrinsic dependence on the location of the nuclei in the NSDR HHG process not seen in one-electron HHG. This dependence originates from the strong electron correlation in the NSDR HHG process, and it modifies the classically allowed return energies which in return changes the cutoffs observed in the HHG spectra. It is observed that the CC-TSM correctly predicts cutoffs at all internuclear distances with differences of more than six harmonics being observed between the CC-TSM and the normal three-step model for the laser parameters used. We also observe that the NSDR HHG process changes for internuclear distances of R ≳8 -9 a.u., which is proposed to stem from a change in the charge-transfer dynamics within the molecule. For large internuclear distances of R ≳13 a.u., we observe a clear signature of the point of emission for the first electron emitted in the NSDR HHG signal and we also see signs of molecular exchange paths contributing to the HHG spectrum for these internuclear distances.

  2. New trends in high-order harmonics generation using the mid-infrared pulses propagating through the laser-produced plasmas

    Science.gov (United States)

    Ganeev, R. A.

    2017-06-01

    Various recently emerged applications of mid-infrared pulses for high-order harmonic generation in laser plasmas produced on the surfaces of various materials are reviewed. Among them are (a) the highorder harmonic generation in Ag, Sn, fullerene, and graphene nanoparticle-containing plasmas using tunable two-color mid-infrared pulses, (b) efficiency dependence on the generating particle properties in the case of two-color high-harmonic generation of the longer-wavelength radiation in the plasmas, and (c) high-order sum and difference frequency generation using tunable two- and three-color commensurate and incommensurate mid-infrared pumps of graphite plasma. These studies demonstrate the perspectives of the frequency conversion of mid-infrared radiation in the extended laser-produced plasmas.

  3. Modelling third harmonic ion cyclotron acceleration of deuterium beams for JET fusion product studies experiments

    DEFF Research Database (Denmark)

    Schneider, M.; Johnson, T.; Dumont, R.

    2016-01-01

    Recent JET experiments have been dedicated to the studies of fusion reactions between deuterium (D) and Helium-3 (3He) ions using neutral beam injection (NBI) in synergy with third harmonic ion cyclotron radio-frequency heating (ICRH) of the beam. This scenario generates a fast ion deuterium tail...

  4. Squeezing and entanglement in doubly resonant, type II, second-harmonic generation

    DEFF Research Database (Denmark)

    Andersen, Ulrik Lund; Buchhave, Preben

    2003-01-01

    We investigate, theoretically, the generation of bright and vacuum-squeezed light as well as entanglement in intracavity, type II, phase-matched second-harmonic generation. The cavity in which the crystal is embedded is resonant at the fundamental frequency but not at the second-harmonic frequency....... A simple model for the process using semiclassical theory is derived, and quadrature-squeezing spectra of the involved fundamental fields are deduced. The analysis shows that vacuum squeezing reminiscent of subthreshold optical parametric oscillator squeezing is present and, in the ideal case, perfect....... Under slight modifications of the operational conditions, the system is shown to produce efficient bright, squeezed light. Furthermore, we investigate the degree of polarization squeezing and find that three Stokes parameters can be squeezed simultaneously. Finally, we gauge the process for possible...

  5. Soft X-Ray Second Harmonic Generation as an Interfacial Probe

    Science.gov (United States)

    Lam, R. K.; Raj, S. L.; Pascal, T. A.; Pemmaraju, C. D.; Foglia, L.; Simoncig, A.; Fabris, N.; Miotti, P.; Hull, C. J.; Rizzuto, A. M.; Smith, J. W.; Mincigrucci, R.; Masciovecchio, C.; Gessini, A.; Allaria, E.; De Ninno, G.; Diviacco, B.; Roussel, E.; Spampinati, S.; Penco, G.; Di Mitri, S.; Trovò, M.; Danailov, M.; Christensen, S. T.; Sokaras, D.; Weng, T.-C.; Coreno, M.; Poletto, L.; Drisdell, W. S.; Prendergast, D.; Giannessi, L.; Principi, E.; Nordlund, D.; Saykally, R. J.; Schwartz, C. P.

    2018-01-01

    Nonlinear optical processes at soft x-ray wavelengths have remained largely unexplored due to the lack of available light sources with the requisite intensity and coherence. Here we report the observation of soft x-ray second harmonic generation near the carbon K edge (˜284 eV ) in graphite thin films generated by high intensity, coherent soft x-ray pulses at the FERMI free electron laser. Our experimental results and accompanying first-principles theoretical analysis highlight the effect of resonant enhancement above the carbon K edge and show the technique to be interfacially sensitive in a centrosymmetric sample with second harmonic intensity arising primarily from the first atomic layer at the open surface. This technique and the associated theoretical framework demonstrate the ability to selectively probe interfaces, including those that are buried, with elemental specificity, providing a new tool for a range of scientific problems.

  6. Soft X-Ray Second Harmonic Generation as an Interfacial Probe

    Energy Technology Data Exchange (ETDEWEB)

    Lam, R. K.; Raj, S. L.; Pascal, T. A.; Pemmaraju, C. D.; Foglia, L.; Simoncig, A.; Fabris, N.; Miotti, P.; Hull, C. J.; Rizzuto, A. M.; Smith, J. W.; Mincigrucci, R.; Masciovecchio, C.; Gessini, A.; Allaria, E.; De Ninno, G.; Diviacco, B.; Roussel, E.; Spampinati, S.; Penco, G.; Di Mitri, S.; Trovò, M.; Danailov, M.; Christensen, S. T.; Sokaras, D.; Weng, T. -C.; Coreno, M.; Poletto, L.; Drisdell, W. S.; Prendergast, D.; Giannessi, L.; Principi, E.; Nordlund, D.; Saykally, R. J.; Schwartz, C. P.

    2018-01-01

    Nonlinear optical processes at soft x-ray wavelengths have remained largely unexplored due to the lack of available light sources with the requisite intensity and coherence. Here we report the observation of soft x-ray second harmonic generation near the carbon K edge (~284 eV) in graphite thin films generated by high intensity, coherent soft x-ray pulses at the FERMI free electron laser. Our experimental results and accompanying first-principles theoretical analysis highlight the effect of resonant enhancement above the carbon K edge and show the technique to be interfacially sensitive in a centrosymmetric sample with second harmonic intensity arising primarily from the first atomic layer at the open surface. This technique and the associated theoretical framework demonstrate the ability to selectively probe interfaces, including those that are buried, with elemental specificity, providing a new tool for a range of scientific problems.

  7. Harmonic generation by internal waves in a thermohaline staircase with rotation

    Science.gov (United States)

    Wunsch, Scott

    2017-11-01

    Thermohaline staircases, generated by double-diffusive convection, are found in many regions of the ocean. Oceanic internal waves interact with these staircases. Recent results show that, in linear theory, internal waves with sufficiently long wavelengths are transmitted through the staircase, while short wavelengths may be reflected. However, nonlinear self-interaction of internal waves with the sharp density jumps within the staircase is expected to generate double-wavenumber harmonics of the incident waves. This effect removes energy from the incident waves, reducing the transmitted energy in some cases. Energy transferred to the harmonic waves may also impact the stability of the staircase. Here, weakly nonlinear theory is used to explore the implications of this nonlinear effect on the dynamics of internal waves in oceanic thermohaline staircases. Rotation is included, and variations with latitude are considered.

  8. High gain harmonic generation free electron lasers enhanced by pseudoenergy bands

    Directory of Open Access Journals (Sweden)

    Takashi Tanaka

    2017-08-01

    Full Text Available We propose a new scheme for high gain harmonic generation free electron lasers (HGHG FELs, which is seeded by a pair of intersecting laser beams to interact with an electron beam in a modulator undulator located in a dispersive section. The interference of the laser beams gives rise to a two-dimensional modulation in the energy-time phase space because of a strong correlation between the electron energy and the position in the direction of dispersion. This eventually forms pseudoenergy bands in the electron beam, which result in efficient harmonic generation in HGHG FELs in a similar manner to the well-known scheme using the echo effects. The advantage of the proposed scheme is that the beam quality is less deteriorated than in other existing schemes.

  9. A single-electron approach for many-electron dynamics in high-order harmonic generation

    CERN Document Server

    Schild, Axel

    2016-01-01

    We present a novel ab-initio single-electron approach to correlated electron dynamics in strong laser fields. By writing the electronic wavefunction as a product of a marginal one-electron wavefunction and a conditional wavefunction, we show that the exact harmonic spectrum can be obtained from a single-electron Schr\\"odinger equation. To obtain the one-electron potential in practice, we propose an adiabatic approximation, i.e. a potential is generated that depends only on the position of one electron. This potential, together with the laser interaction, is then used to obtain the dynamics of the system. For a model Helium atom in a laser field, we show that by using our approach, the high-order harmonic generation spectrum can be obtained to a good approximation.

  10. Direct detection of the parametrically generated half-harmonic voltage in a Josephson tunnel junction

    DEFF Research Database (Denmark)

    Mygind, Jesper; Pedersen, Niels Falsig; Sørensen, O. H.

    1976-01-01

    The first direct observation of the parametrically generated half-harmonic voltage in a Josephson tunnel junction is reported. A microwave signal at f=17.25 GHz is applied to the junction dc current biased at zero voltage such that the Josephson plasma resonance fp=f/2. Under these conditions a l...... a large-amplitude microwave signal is emitted at fp provided the input power exceeds a threshold value. The results are compared to existing theory. Applied Physics Letters is copyrighted by The American Institute of Physics.......The first direct observation of the parametrically generated half-harmonic voltage in a Josephson tunnel junction is reported. A microwave signal at f=17.25 GHz is applied to the junction dc current biased at zero voltage such that the Josephson plasma resonance fp=f/2. Under these conditions...

  11. Third-harmonic terahertz generation from graphene in a parallel-plate waveguide

    Science.gov (United States)

    Navaeipour, Parvin; Al-Naib, Ibraheem; Dignam, Marc M.

    2018-01-01

    Graphene as a zero-band-gap two-dimensional semiconductor with a linear electron band dispersion near the Dirac points has the potential to exhibit very interesting nonlinear optical properties. In particular, third-harmonic generation of terahertz radiation should occur due to the nonlinear relationship between the crystal momentum and the current density. In this work, we investigate the terahertz nonlinear response of graphene inside a parallel-plate waveguide. We optimize the plate separation and Fermi energy of the graphene to maximize third-harmonic generation, by maximizing the nonlinear interaction while minimizing the loss and phase mismatch. The results obtained show an increase by more than a factor of 100 in the power efficiency relative to a normal-incidence configuration for a 2.0-THz incident field.

  12. Resonance-modulated wavelength scaling of high-order-harmonic generation from H2+

    Science.gov (United States)

    Wang, Baoning; He, Lixin; Wang, Feng; Yuan, Hua; Zhu, Xiaosong; Lan, Pengfei; Lu, Peixiang

    2018-01-01

    Wavelength scaling of high-order harmonic generation (HHG) in a non-Born-Oppenheimer treatment of H2+ is investigated by numerical simulations of the time-dependent Schrödinger equation. The results show that the decrease in the wavelength-dependent HHG yield is reduced compared to that in the fixed-nucleus approximation. This slower wavelength scaling is related to the charge-resonance-enhanced ionization effect, which considerably increases the ionization rate at longer driving laser wavelengths due to the relatively larger nuclear separation. In addition, we find an oscillation structure in the wavelength scaling of HHG from H2+. Upon decreasing the laser intensity or increasing the nuclear mass, the oscillation structure will shift towards a longer wavelength of the laser pulse. These results permit the generation of an efficient harmonic spectrum in the midinfrared regime by manipulating the nuclear dynamics of molecules.

  13. A piezoelectric pulse generator for low frequency non-harmonic vibration

    Science.gov (United States)

    Jiang, Hao; Yeatman, Eric M.

    2013-12-01

    This paper reports a new piezoelectric prototype for pulse generation by energy harvesting from low frequency non-harmonic vibration. The pulse generator presented here consists of two parts: the electromechanical part and the load circuit. A metal rolling rod is used as the proof mass, moving along the substrate to achieve both actuating of the piezoelectric cantilever by magnetic coupling and self-synchronous switching of the circuit. By using this new approach, the energy from the piezoelectric transduction mechanism is regulated simultaneously when it is extracted. This allows a series of tuneable pulses to be generated, which can be applied to self-powered RF wireless sensor network (WSN) nodes.

  14. Combined action of the bound-electron nonlinearity and the tunnel-ionization current in low-order harmonic generation in noble gases.

    Science.gov (United States)

    Sapaev, Usman; Husakou, Anton; Herrmann, Joachim

    2013-10-21

    We study numerically low-order harmonic generation in noble gases pumped by intense femtosecond laser pulses in the tunneling ionization regime. We analyze the influence of the phase-mismatching on this process, caused by the generated plasma, and study in dependence on the pump intensity the origin of harmonic generation arising either from the bound-electron nonlinearity or the tunnel-ionization current. It is shown that in argon the optimum pump intensity of about 100 TW/cm² leads to the maximum efficiency, where the main contribution to low-order harmonics originates from the bound-electron third and fifth order susceptibilities, while for intensities higher than 300 TW/cm² the tunnel-ionization current plays the dominant role. Besides, we predict that VUV pulses at 133 nm can be generated with relatively high efficiency of about 1.5 × 10⁻³ by 400 nm pump pulses.

  15. Second Harmonic Generation Imaging and Fourier Transform Spectral Analysis Reveal Damage in Fatigue-Loaded Tendons

    Science.gov (United States)

    Fung, David T.; Sereysky, Jedd B.; Basta-Pljakic, Jelena; Laudier, Damien M.; Huq, Rumana; Jepsen, Karl J.; Schaffler, Mitchell B.; Flatow, Evan L.

    2016-01-01

    Conventional histologic methods provide valuable information regarding the physical nature of damage in fatigue-loaded tendons, limited to thin, two-dimensional sections. We introduce an imaging method that characterizes tendon microstructure three-dimensionally and develop quantitative, spatial measures of damage formation within tendons. Rat patellar tendons were fatigue loaded in vivo to low, moderate, and high damage levels. Tendon microstructure was characterized using multiphoton microscopy by capturing second harmonic generation signals. Image stacks were analyzed using Fourier transform-derived computations to assess frequency-based properties of damage. Results showed 3D microstructure with progressively increased density and variety of damage patterns, characterized by kinked deformations at low, fiber dissociation at moderate, and fiber thinning and out-of-plane discontinuities at high damage levels. Image analysis generated radial distributions of power spectral gradients, establishing a “fingerprint” of tendon damage. Additionally, matrix damage was mapped using local, discretized orientation vectors. The frequency distribution of vector angles, a measure of damage content, differed from one damage level to the next. This study established an objective 3D imaging and analysis method for tendon microstructure, which characterizes directionality and anisotropy of the tendon microstructure and quantitative measures of damage that will advance investigations of the microstructural basis of degradation that precedes overuse injuries. PMID:20232150

  16. Imaging corneal crosslinking by autofluorescence 2-photon microscopy, second harmonic generation, and fluorescence lifetime measurements.

    Science.gov (United States)

    Steven, Philipp; Hovakimyan, Marina; Guthoff, Rudolf F; Hüttmann, Gereon; Stachs, Oliver

    2010-12-01

    To evaluate the use of 2-photon microscopy (TPM), which excites tissue autofluorescence, in detecting and calculating the grade of collagen corneal crosslinks, which are not visible through the slitlamp and in vivo confocal microscopy. Departments of Ophthalmology, University of Lübeck, Lübeck, and University of Rostock, Rostock, Germany. Experimental study. Corneas of rabbits were treated with different crosslinking (CXL) protocols. Two weeks after treatment, the corneas were evaluated in vivo by confocal microscopy. Eyes were enucleated and TPM was performed at 710 nm and 826 nm excitation wavelengths to detect tissue autofluorescence, second harmonic generation, and fluorescence lifetime measurements (FLIM). Eyes were then fixed and analyzed by histology. Crosslinking following the standard protocol generated a strong autofluorescence signal in the stroma that was detected by TPM. This signal was weakly present in the control specimens, and a sharp transition zone between the peripheral zone and the CXL zone was seen. On FLIM, an increase in corneal crosslinks was measured when the standard protocol was used. Two-photon microscopy, a noninvasive method, was able to detect the effects of therapeutic CXL and measure the grade of CXL. In addition to postoperative treatment control, the technique has possibilities for use in online dosimetry during 2-photon triggered CXL. Copyright © 2010 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  17. Optical second harmonic generation phase measurement at interfaces of some organic layers with indium tin oxide

    OpenAIRE

    Ngah Demon, Siti Zulaikha; Miyauchi, Yoshihiro; Mizutani, Goro; Matsushima, Toshinori; Murata, Hideyuki

    2014-01-01

    We observed phase shift in optical second harmonic generation (SHG) from interfaces of indium tin oxide (ITO)/copper phthalocyanine (CuPc) and ITO/pentacene. Phase correction due to Fresnel factors of the sample was taken into account. The phase of SHG electric field at the ITO/pentacene interface, ϕ_ with respect to the phase of SHG of bare substrate ITO was 160°, while the interface of ITO/CuPc had a phase of 140°.

  18. Optical second harmonic generation phase measurement at interfaces of some organic layers with indium tin oxide

    Science.gov (United States)

    Ngah Demon, Siti Zulaikha; Miyauchi, Yoshihiro; Mizutani, Goro; Matsushima, Toshinori; Murata, Hideyuki

    2014-08-01

    We observed phase shift in optical second harmonic generation (SHG) from interfaces of indium tin oxide (ITO)/copper phthalocyanine (CuPc) and ITO/pentacene. Phase correction due to Fresnel factors of the sample was taken into account. The phase of SHG electric field at the ITO/pentacene interface, ϕinterface with respect to the phase of SHG of bare substrate ITO was 160°, while the interface of ITO/CuPc had a phase of 140°.

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

    Science.gov (United States)

    2016-08-26

    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...intensity on layer number as a result of atomically phase-matched nonlinear dipoles in layers of the 3R crystal that constructively interfere. By

  20. Power characteristics of CW second harmonic generation in periodically poled LiNbO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Bong Hoon; Rhee, Bum Ku [Dept. of Physics, Sogang University, Seoul (Korea, Republic of); Cha, Myoung Sik [Research Center for Dielectric and Advanced Matter Physics. Busan National University, Busan (Korea, Republic of)

    2002-07-01

    Power characteristics of CW second harmonic generation (SHG) in 0.5-mm-thick periodically poled LiNbO{sub 3} (PPLN) witha 6.5 μm domain period were investigated as a function of crystal length, and confocal parameter which was varied by using a lens of different focal length. We found there is the optimum condition of confocal parameter for SHG for a given intensity.

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

    Science.gov (United States)

    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.

  2. High-contrast imaging of mycobacterium tuberculosis using third-harmonic generation microscopy

    Science.gov (United States)

    Kim, Bo Ram; Lee, Eungjang; Park, Seung-Han

    2015-07-01

    Nonlinear optical microcopy has become an important tool in investigating biomaterials due to its various advantages such as label-free imaging capabilities. In particular, it has been shown that third-harmonic generation (THG) signals can be produced at interfaces between an aqueous medium (e.g. cytoplasm, interstitial fluid) and a mineralized lipidic surface. In this work, we have demonstrated that label-free high-contrast THG images of the mycobacterium tuberculosis can be obtained using THG microscopy.

  3. Demonstration of the dual-tripler scheme for increased-bandwidth third-harmonic generation.

    Science.gov (United States)

    Babushkin, A; Craxton, R S; Oskoui, S; Guardalben, M J; Keck, R L; Seka, W

    1998-06-15

    The dual-tripler scheme for enhancing the bandwidth of third-harmonic generation proposed by Eimerl et al. [Opt. Lett. 22, 1208 (1997)] is experimentally demonstrated for the conversion of 1054-nm radiation to 351 nm. It is shown that the spacing between the triplers must be carefully controlled. The results are in excellent agreement with theory and indicate that fusion lasers can be frequency tripled with a threefold increase in bandwidth.

  4. Broad-band second-harmonic generation in holey optical fibers

    OpenAIRE

    Monro, T.M.; Pruneri, V.; Broderick, N.G.R.; Faccio, D.; Kazansky, P. G.; Richardson, D.J.

    2001-01-01

    Holey fibers are shown to have an ideal geometry for efficient parametric processes due to their tailorable modal properties. These fibers can have the additional advantage of single-mode operation at all the interacting wavelengths. We demonstrate theoretically that by appropriate choice of holey fiber geometry, these fibers can be up to four orders of magnitude more efficient for second harmonic generation than conventional poled fibers

  5. Local excitation of surface plasmon polaritons by second-harmonic generation in crystalline organic nanofibers

    DEFF Research Database (Denmark)

    Skovsen, Esben; Søndergaard, Thomas; Fiutowski, Jacek

    2012-01-01

    Coherent local excitation of surface plasmon polaritons (SPPs) by second-harmonic generation (SHG) in aligned crystalline organic functionalized para-phenylene nanofibers deposited on a thin silver film is demonstrated. The excited SPPs are characterized using angle-resolved leakage radiation....... This is explained both as a consequence of approaching the peak of the fibers nonlinear response at the wavelength 772 nm, and as a consequence of better coupling to SPPs due to their stronger confinement. © 2012 Optical Society...

  6. Hyperglycemia-induced abnormalities in rat and human corneas: the potential of second harmonic generation microscopy.

    OpenAIRE

    Gaël Latour; Laura Kowalczuk; Michèle Savoldelli; Jean-Louis Bourges; Karsten Plamann; Francine Behar-Cohen; Marie-Claire Schanne-Klein

    2012-01-01

    International audience; BACKGROUND: Second Harmonic Generation (SHG) microscopy recently appeared as an efficient optical imaging technique to probe unstained collagen-rich tissues like cornea. Moreover, corneal remodeling occurs in many diseases and precise characterization requires overcoming the limitations of conventional techniques. In this work, we focus on diabetes, which affects hundreds of million people worldwide and most often leads to diabetic retinopathy, with no early diagnostic...

  7. The origin of second harmonic generation hotspots in chiral optical metamaterials [Invited

    OpenAIRE

    Valev, V.K.; Zheng, X.; Biris, C. G.; Silhanek, A. V.; Volskiy, V.; De Clercq, Ben; Aktsipetrov, Oleg A.; Ameloot, Marcel; Panoiu, N C; Vandenbosch, G. A. E.; Moshchalkov, V. V.

    2011-01-01

    Novel ways to detect the handedness in chiral optical metamaterials by means of the second harmonic generation (SHG) process have recently been proposed. However, the precise origin of the SHG emission has yet to be unambiguously established. In this paper, we present computational simulations of both the electric currents and the electromagnetic fields in chiral planar metamaterials, at the fundamental frequency (FF), and discuss the implications of our results on the characteristics of expe...

  8. Grain size effect of monolayer MoS2 transistors characterized by second harmonic generation mapping

    KAUST Repository

    Lin, Chih-Pin

    2015-08-27

    We investigated different CVD-synthesized MoS2 films, aiming to correlate the device characteristics with the grain size. The grain size of MoS2 can be precisely characterized through nondestructive second harmonic generation mapping based on the degree of inversion symmetry. The devices with larger grains at the channel region show improved on/off current ratio, which can be explained by the less carrier scattering caused by the grain boundaries.

  9. Singularity-driven second- and third-harmonic generation at {epsilon}-near-zero crossing points

    Energy Technology Data Exchange (ETDEWEB)

    Vincenti, M. A.; Ceglia, D. de [AEgis Technologies Inc., Huntsville, Alabama 35806 (United States); Ciattoni, A. [Consiglio Nazionale delle Ricerche, CNR-SPIN, I-67100 L' Aquila (Italy); Scalora, M. [Charles M. Bowden Research Center, RDECOM, Redstone Arsenal, Alabama 35898-5000 (United States)

    2011-12-15

    We show an alternative path to efficient second- and third-harmonic generation in proximity of the zero crossing points of the dielectric permittivity in conjunction with low absorption. Under these circumstances, any material, either natural or artificial, will show similar degrees of field enhancement followed by strong harmonic generation, without resorting to any resonant mechanism. The results presented in this paper provide a general demonstration of the potential that the zero-crossing-point condition holds for nonlinear optical phenomena. We investigate a generic Lorentz medium and demonstrate that a singularity-driven enhancement of the electric field may be achieved even in extremely thin layers of material. We also discuss the role of nonlinear surface sources in a realistic scenario where a 20-nm layer of CaF{sub 2} is excited at 21 {mu}m, where {epsilon}{approx} 0. Finally, we show similar behavior in an artificial composite material that includes absorbing dyes in the visible range, provide a general tool for the improvement of harmonic generation using the {epsilon}{approx} 0 condition, and illustrate that this singularity-driven enhancement of the field lowers the thresholds for a plethora of nonlinear optical phenomena.

  10. Autonomous control of inverter-interfaced Distributed Generation units for harmonic current filtering and resonance damping in an islanded microgrid

    DEFF Research Database (Denmark)

    Wang, Xiongfei; Blaabjerg, Frede; Chen, Zhe

    2012-01-01

    Harmonic current filtering and resonance damping have become important concerns on the control of an islanded microgrids. To address these challenges, this paper proposes a control method of inverter-interfaced Distributed Generation (DG) units, which can autonomously share harmonic currents and ...

  11. Fully automated muscle quality assessment by Gabor filtering of second harmonic generation images

    Science.gov (United States)

    Paesen, Rik; Smolders, Sophie; Vega, José Manolo de Hoyos; Eijnde, Bert O.; Hansen, Dominique; Ameloot, Marcel

    2016-02-01

    Although structural changes on the sarcomere level of skeletal muscle are known to occur due to various pathologies, rigorous studies of the reduced sarcomere quality remain scarce. This can possibly be explained by the lack of an objective tool for analyzing and comparing sarcomere images across biological conditions. Recent developments in second harmonic generation (SHG) microscopy and increasing insight into the interpretation of sarcomere SHG intensity profiles have made SHG microscopy a valuable tool to study microstructural properties of sarcomeres. Typically, sarcomere integrity is analyzed by fitting a set of manually selected, one-dimensional SHG intensity profiles with a supramolecular SHG model. To circumvent this tedious manual selection step, we developed a fully automated image analysis procedure to map the sarcomere disorder for the entire image at once. The algorithm relies on a single-frequency wavelet-based Gabor approach and includes a newly developed normalization procedure allowing for unambiguous data interpretation. The method was validated by showing the correlation between the sarcomere disorder, quantified by the M-band size obtained from manually selected profiles, and the normalized Gabor value ranging from 0 to 1 for decreasing disorder. Finally, to elucidate the applicability of our newly developed protocol, Gabor analysis was used to study the effect of experimental autoimmune encephalomyelitis on the sarcomere regularity. We believe that the technique developed in this work holds great promise for high-throughput, unbiased, and automated image analysis to study sarcomere integrity by SHG microscopy.

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

    Science.gov (United States)

    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.

  13. The Study of Damped Harmonic Oscillations Using an Electronic Counter

    Science.gov (United States)

    Wadhwa, Ajay

    2009-01-01

    We study damped harmonic oscillations in mechanical systems like the loaded spring and simple pendulum with the help of an oscillation measuring electronic counter. The experimental data are used in a software program that solves the differential equation for damped vibrations of any system and determines its position, velocity and acceleration as…

  14. A Comparative Study of the Use of Harmonic Scalpel versus ...

    African Journals Online (AJOL)

    Context: Oncosurgery is an emerging branch with the set goals of prolonging the life and ensuring the best possible quality of life to the surviving patient. The use of harmonic scalpel has proved to be beneficial in a variety of surgeries but its role in breast surgery is still controversial. Aims: We conducted this study to ...

  15. Crystal growth and second harmonic generation efficiency of a chalcone derivative

    Energy Technology Data Exchange (ETDEWEB)

    Meenatchi, V.; Muthu, K.; Rajasekar, M.; Meenakshisundaram, SP., E-mail: aumats2009@gmail.com

    2013-06-15

    Single crystals of (2E,6E)-2-(4-fluorobenzylidine)-6-(4-methoxybenzylidine)cyclohexanone (FBMBC) have been grown by a slow evaporation solution growth technique from ethanol at room temperature. The single crystal X-ray diffraction study reveals that the FBMBC belongs to triclinic system and the cell parameters are a=9.790(6) Å, b=12.08(7) Å, c=14.09(9) Å and V=1577 Å{sup 3}. The structure and the crystallinity of the material were further confirmed by powder X-ray diffraction analysis. The various functional groups present in the molecule are confirmed by Fourier transform infrared spectral analysis. The scanning electron microscopy study reveals the surface morphology of the as-grown crystal. Thermogravimetric/differential thermal analysis studies reveal the purity of the material and the crystals are transparent in the visible region having a low optical cut-off at ∼475 nm. The second harmonic generation efficiency of FBMBC is estimated by the Kurtz and Perry technique. Theoretical calculations were performed using the Hartree–Fock method with 6-31 G(d,p) as the basis set to derive the optimized geometry and the first-order molecular hyperpolarizability (β) values.

  16. Wannier-Bloch approach to localization in high harmonics generation in solids

    CERN Document Server

    Osika, Edyta N; Ortmann, Lisa; Suárez, Noslen; Pérez-Hernández, Jose Antonio; Szafran, Bartłomiej; Ciappina, Marcelo F; Sols, Fernando; Landsman, Alexandra S; Lewenstein, Maciej

    2016-01-01

    Emission of high-order harmonics from solids provides a new avenue in attosecond science. On one hand, it allows to investigate fundamental processes of the non-linear response of electrons driven by a strong laser pulse in a periodic crystal lattice. On the other hand, it opens new paths toward efficient attosecond pulse generation, novel imaging of electronic wave functions, and enhancement of high-order harmonic generation (HHG) intensity. A key feature of HHG in a solid (as compared to the well-understood phenomena of HHG in an atomic gas) is the delocalization of the process, whereby an electron ionized from one site in the periodic lattice may recombine with any other. Here, we develop an analytic model, based on the localized Wannier wave functions in the valence band and delocalized Bloch functions in the conduction band. This Wannier-Bloch approach assesses the contributions of individual lattice sites to the HHG process, and hence addresses precisely the question of localization of harmonic emission...

  17. Minimum in the high-order harmonic generation spectrum from molecules: role of excited states

    DEFF Research Database (Denmark)

    Han, Yong-Chang; Madsen, Lars Bojer

    2010-01-01

    that the coherent laser coupling induced between the 2Σ+g(1sσg) ground state and the first excited 2Σ+u(2pσu) state leads to two dominating amplitudes for the high-order harmonic generation that may interfere: amplitudes describing recombination back into the σg and σu states, respectively. These two amplitudes may......We model the process of high-order harmonic generation by solving the time-dependent Schrödinger equation for H+2 in the fixed nuclei approximation including full 3D electron motion for nonvanishing angles between the nuclear axis and the linear polarization of the driving pulse. We show...... interfere destructively or constructively. The effect of a destructive interference is very clear through the occurrence of a minimum in the high-order harmonic spectrum. We show cases where such a minimum in the spectrum is approximately at the position predicted by the simple two-centre interference...

  18. The Interplay of Symmetry and Scattering Phase in Second Harmonic Generation from Gold Nanoantennas.

    Science.gov (United States)

    Gennaro, Sylvain D; Rahmani, Mohsen; Giannini, Vincenzo; Aouani, Heykel; Sidiropoulos, Themistoklis P H; Navarro-Cía, Miguel; Maier, Stefan A; Oulton, Rupert F

    2016-08-10

    Nonlinear phenomena are central to modern photonics but, being inherently weak, typically require gradual accumulation over several millimeters. For example, second harmonic generation (SHG) is typically achieved in thick transparent nonlinear crystals by phase-matching energy exchange between light at initial, ω, and final, 2ω, frequencies. Recently, metamaterials imbued with artificial nonlinearity from their constituent nanoantennas have generated excitement by opening the possibility of wavelength-scale nonlinear optics. However, the selection rules of SHG typically prevent dipole emission from simple nanoantennas, which has led to much discussion concerning the best geometries, for example, those breaking centro-symmetry or incorporating resonances at multiple harmonics. In this work, we explore the use of both nanoantenna symmetry and multiple harmonics to control the strength, polarization and radiation pattern of SHG from a variety of antenna configurations incorporating simple resonant elements tuned to light at both ω and 2ω. We use a microscopic description of the scattering strength and phases of these constituent particles, determined by their relative positions, to accurately predict the SHG radiation observed in our experiments. We find that the 2ω particles radiate dipolar SHG by near-field coupling to the ω particle, which radiates SHG as a quadrupole. Consequently, strong linearly polarized dipolar SHG is only possible for noncentro-symmetric antennas that also minimize interference between their dipolar and quadrupolar responses. Metamaterials with such intra-antenna phase and polarization control could enable compact nonlinear photonic nanotechnologies.

  19. Second harmonic generation in nano-structured thin-film lithium niobate waveguides.

    Science.gov (United States)

    Wang, Cheng; Xiong, Xiao; Andrade, Nicolas; Venkataraman, Vivek; Ren, Xi-Feng; Guo, Guang-Can; Lončar, Marko

    2017-03-20

    Integrated thin-film lithium niobate platform has recently emerged as a promising candidate for next-generation, high-efficiency wavelength conversion systems that allow dense packaging and mass-production. Here we demonstrate efficient, phase-matched second harmonic generation in lithographically-defined thin-film lithium niobate waveguides with sub-micron dimensions. Both modal phase matching in fixed-width waveguides and quasi-phase matching in periodically grooved waveguides are theoretically proposed and experimentally demonstrated. Our low-loss (~3.0 dB/cm) nanowaveguides possess normalized conversion efficiencies as high as 41% W-1cm-2.

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

    Science.gov (United States)

    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.

  1. Anomalous circular dichroism in high harmonic generation of stereoisomers with two chiral centers.

    Science.gov (United States)

    Zhu, Xiaosong; Liu, Xi; Lan, Pengfei; Wang, Dian; Zhang, Qingbin; Li, Wei; Lu, Peixiang

    2016-10-31

    When a molecule has more than one chiral center, it can be either a chiral molecule or a meso isomer. High harmonic generation (HHG) of stereoisomers with two chiral centers driven by circularly polarized (CP) laser pulses is investigated. Counterintuitively, it is found that the HHG exhibits prominent circular dichroism for the meso isomer, while the harmonic spectra with left and right CP laser pulses are nearly the same for the chiral isomers. We show that the anomalous circular dichroism is attributed to the characteristic recollision dynamics of HHG. This feature makes the HHG a promising tool to discriminate the meso isomer and racemic mixture, where no optical activity can be found in both cases. Similar dichroism responses are also found by applying the counter-rotating bicircular laser pulses.

  2. Dynamical effects and terahertz harmonic generation in low-doped bulk semiconductors and submicron structures

    Energy Technology Data Exchange (ETDEWEB)

    Persano Adorno, D.; Capizzo, M.C.; Zarcone, M. [Dipartimento di Fisica e Tecnologie Relative, Viale delle Scienze, Ed. 18, 90128, Palermo (Italy)

    2006-08-15

    We present results obtained using a three-dimensional multivalleys Monte Carlo (MC) model to simulate the nonlinear carrier dynamics under the influence of an intense sub-terahertz electric field in a doped bulk semiconductor. By self-consistently coupling a one-dimensional Poisson solver to the ensemble MC code we simulate also the nonlinear carrier dynamics in n{sup +}nn{sup +} structures operating under large-amplitude periodic signals and investigate the voltage-current characteristic hysteresis cycle and the high-order harmonic efficiency. For both cases we discuss the dependence of the nonlinearities and of the harmonic generation efficiency on the frequency and the intensity of the alternating signal. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Measuring the angle-dependent photoionization cross section of nitrogen using high-harmonic generation

    Science.gov (United States)

    Ren, Xiaoming; Makhija, Varun; Le, Anh-Thu; Troß, Jan; Mondal, Sudipta; Jin, Cheng; Kumarappan, Vinod; Trallero-Herrero, Carlos

    2013-10-01

    We exploit the relationship between high harmonic generation (HHG) and the molecular photorecombination dipole to extract the molecular-frame differential photoionization cross section (PICS) in the extreme ultraviolet (XUV) for molecular nitrogen. A shape resonance and a Cooper-type minimum are reflected in the pump-probe time delay measurements of different harmonic orders, where high-order rotational revivals are observed in N2. We observe the energy- and angle-dependent Cooper minimum and shape resonance directly in the laboratory-frame HHG yield by achieving a high degree of alignment, ≥0.8. The interplay between PICS and rotational revivals is confirmed by simulations using the quantitative rescattering theory. Our method of extracting molecular-frame structural information points the way to similar measurements in more complex molecules.

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

    Science.gov (United States)

    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.

  5. High-power green light generation by second harmonic generation of single-frequency tapered diode lasers

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin; Andersen, Peter E.; Sumpf, Bernd

    2010-01-01

    laser emits in excess of 9 W single-frequency output power with a good beam quality. The output from the tapered diode laser is frequency doubled using periodically poled MgO:LiNbO3. We investigate the modulation potential of the green light and improve the modulation depth from 1:4 to 1:50.......We demonstrate the generation of high power (>1.5W) and single-frequency green light by single-pass second harmonic generation of a high power tapered diode laser. The tapered diode laser consists of a DBR grating for wavelength selectivity, a ridge section and a tapered section. The DBR tapered...

  6. Harmonization of initial estimates of shale gas life cycle greenhouse gas emissions for electric power generation

    Science.gov (United States)

    Heath, Garvin A.; O’Donoughue, Patrick; Arent, Douglas J.; Bazilian, Morgan

    2014-01-01

    Recent technological advances in the recovery of unconventional natural gas, particularly shale gas, have served to dramatically increase domestic production and reserve estimates for the United States and internationally. This trend has led to lowered prices and increased scrutiny on production practices. Questions have been raised as to how greenhouse gas (GHG) emissions from the life cycle of shale gas production and use compares with that of conventionally produced natural gas or other fuel sources such as coal. Recent literature has come to different conclusions on this point, largely due to differing assumptions, comparison baselines, and system boundaries. Through a meta-analytical procedure we call harmonization, we develop robust, analytically consistent, and updated comparisons of estimates of life cycle GHG emissions for electricity produced from shale gas, conventionally produced natural gas, and coal. On a per-unit electrical output basis, harmonization reveals that median estimates of GHG emissions from shale gas-generated electricity are similar to those for conventional natural gas, with both approximately half that of the central tendency of coal. Sensitivity analysis on the harmonized estimates indicates that assumptions regarding liquids unloading and estimated ultimate recovery (EUR) of wells have the greatest influence on life cycle GHG emissions, whereby shale gas life cycle GHG emissions could approach the range of best-performing coal-fired generation under certain scenarios. Despite clarification of published estimates through harmonization, these initial assessments should be confirmed through methane emissions measurements at components and in the atmosphere and through better characterization of EUR and practices. PMID:25049378

  7. Second harmonic generation property of monolayer TMDCs and its potential application in producing terahertz radiation.

    Science.gov (United States)

    Hu, Lei; Wei, Dongshan; Huang, Xuri

    2017-12-28

    Second harmonic generation (SHG) properties in two-dimensional (2D) transition-metal dichalcogenides (TMDCs) have aroused great interest. However, until now SHG for TMDC monolayer alloys is seldom investigated. Meanwhile, there is considerable controversy over the static SHG coefficients of monolayer MoS2. The feasibility to produce terahertz (THz) radiation via SHG in pure and alloyed TMDCs has never been reported. We first calculate the SHG coefficients of monolayer MoS2, MoSe2, and MoS2(1-x)Se2x using the independent particle approximation plus scissors correction. We then simulate their THz absorption by applying density function perturbation theory plus the Lorentzian line and try to calculate their zero-frequency THz refractive index and birefringence. The physical property of MoS2(1-x)Se2x alloys is simulated by considering various combinations. Results indicate that monolayer MoS2, MoSe2, and MoS2(1-x)Se2x possess large static SHG coefficients and THz birefringence and display low absorption over broadband THz frequencies. Therefore, they have applications in producing THz radiation via SHG. This study demonstrates that THz radiation can be attained in a large number of monolayers and few-layers and will extend applications of 2D materials. Moreover, it is possible to identify the magnitude of static coefficients of single-layer MoS2 by measuring THz intensities.

  8. Precise characterization of self-catalyzed III-V nanowire heterostructures via optical second harmonic generation

    Science.gov (United States)

    Yu, Ying; Wang, Jing; Wei, Yu-Ming; Zhou, Zhang-Kai; Ni, Hai-Qiao; Niu, Zhi-Chuan; Wang, Xue-Hua; Yu, Si-Yuan

    2017-09-01

    We demonstrate the utility of optical second harmonic generation (SHG) polarimetry to perform structural characterization of self-assembled zinc-blende/wurtzite III-V nanowire heterostructures. By analyzing four anisotropic SHG polarimetric patterns, we distinguish between wurtzite (WZ), zinc-blende (ZB) and ZB/WZ mixing III-V semiconducting crystal structures in nanowire systems. By neglecting the surface contributions and treating the bulk crystal within the quasi-static approximation, we can well explain the optical SHG polarimetry from the NWs with diameter from 200-600 nm. We show that the optical in-coupling and out-coupling coefficients arising from depolarization field can determine the polarization of the SHG. We also demonstrate micro-photoluminescence of GaAs quantum dots in related ZB and ZB/WZ mixing sections of core-shell NW structure, in agreement with the SHG polarimetry results. The ability to perform in situ SHG-based crystallographic study of semiconducting single and multi-crystalline nanowire heterostructures will be useful in displaying structure-property relationships of nanodevices.

  9. Excitonic effects in third-harmonic generation: The case of carbon nanotubes and nanoribbons

    Science.gov (United States)

    Attaccalite, C.; Cannuccia, E.; Grüning, M.

    2017-03-01

    Linear and nonlinear optical properties of low-dimensional nanostructures have attracted great interest from the scientific community as tools to probe the strong confinement of electrons and for possible applications in optoelectronic devices. In particular it has been shown that the linear optical response of carbon nanotubes [F. Wang et al., Science 308, 838 (2005), 10.1126/science.1110265] and graphene nanoribbons [Nat. Commun. 5 4253 (2014), 10.1038/ncomms5253] is dominated by bounded electron-hole pairs, excitons. The role of excitons in linear response has been widely studied, but still, little is known about their effect on nonlinear susceptibilities. Using a recently developed methodology [Phys. Rev. B 88, 235113 (2013), 10.1103/PhysRevB.88.235113] based on well-established ab initio many-body perturbation theory approaches, we find that quasiparticle shifts and excitonic effects significantly modify the third-harmonic generation in carbon nanotubes and graphene nanoribbons. For both systems the net effect of many-body effects is to reduce the intensity of the main peak in the independent-particle spectrum and redistribute the spectral weight among several excitonic resonances.

  10. Second harmonic generation microscopy differentiates collagen type I and type III in COPD

    Science.gov (United States)

    Suzuki, Masaru; Kayra, Damian; Elliott, W. Mark; Hogg, James C.; Abraham, Thomas

    2012-03-01

    The structural remodeling of extracellular matrix proteins in peripheral lung region is an important feature in chronic obstructive pulmonary disease (COPD). Multiphoton microscopy is capable of inducing specific second harmonic generation (SHG) signal from non-centrosymmetric structural proteins such as fibrillar collagens. In this study, SHG microscopy was used to examine structural remodeling of the fibrillar collagens in human lungs undergoing emphysematous destruction (n=2). The SHG signals originating from these diseased lung thin sections from base to apex (n=16) were captured simultaneously in both forward and backward directions. We found that the SHG images detected in the forward direction showed well-developed and well-structured thick collagen fibers while the SHG images detected in the backward direction showed striking different morphological features which included the diffused pattern of forward detected structures plus other forms of collagen structures. Comparison of these images with the wellestablished immunohistochemical staining indicated that the structures detected in the forward direction are primarily the thick collagen type I fibers and the structures identified in the backward direction are diffusive structures of forward detected collagen type I plus collagen type III. In conclusion, we here demonstrate the feasibility of SHG microscopy in differentiating fibrillar collagen subtypes and understanding their remodeling in diseased lung tissues.

  11. Femtosecond pump-probe second-harmonic generation from silicon nanogratings

    Science.gov (United States)

    An, Yong; Green, Avery; Diebold, Alain

    Silicon nanogratings with fin-like nanogroove arrays have been used in nanoelectronics to build field effect transistors (FinFETs), which have attracted enormous attention due to their superior electronic properties. They can also be used in photonic systems to achieve desired linear and nonlinear optical functionalities. Here we perform second-harmonic generation (SHG) measurements using femtosecond laser pulses on a set of 28, 42, and 65 nm-pitch Si nanogratings to study rotational anisotropy and ultrafast dynamics of SHG. We observe that in pump-probe SHG experiments, the SHG signal from a Si nanograting can be instantaneously enhanced 32% by an autocorrelated pump pulse. The enhancement is caused by pump-induced transient polarization of photoexcited charge in the nanogratings. We also find that charge photoinjection magnifies the quadrupole SHG component significantly more than the dipole SHG component. These results provide insight into the SHG response at the nanoscale, dynamic behaviors of SHG upon photoexcitation, and ultrafast dynamics of photoexcited carriers in Si nanogratings. Furthermore, SHG results from nanogratings of different pitches provide guidance for using the SHG technique to characterize feature dimensions in Si nanogratings.

  12. Imaging Collagen in Scar Tissue: Developments in Second Harmonic Generation Microscopy for Biomedical Applications.

    Science.gov (United States)

    Mostaço-Guidolin, Leila; Rosin, Nicole L; Hackett, Tillie-Louise

    2017-08-15

    The ability to respond to injury with tissue repair is a fundamental property of all multicellular organisms. The extracellular matrix (ECM), composed of fibrillar collagens as well as a number of other components is dis-regulated during repair in many organs. In many tissues, scaring results when the balance is lost between ECM synthesis and degradation. Investigating what disrupts this balance and what effect this can have on tissue function remains an active area of research. Recent advances in the imaging of fibrillar collagen using second harmonic generation (SHG) imaging have proven useful in enhancing our understanding of the supramolecular changes that occur during scar formation and disease progression. Here, we review the physical properties of SHG, and the current nonlinear optical microscopy imaging (NLOM) systems that are used for SHG imaging. We provide an extensive review of studies that have used SHG in skin, lung, cardiovascular, tendon and ligaments, and eye tissue to understand alterations in fibrillar collagens in scar tissue. Lastly, we review the current methods of image analysis that are used to extract important information about the role of fibrillar collagens in scar formation.

  13. Tuning third harmonic generation of impurity doped quantum dots in the presence of Gaussian white noise

    Science.gov (United States)

    Saha, Surajit; Ghosh, Manas

    2016-03-01

    We perform a broad exploration of profiles of third harmonic generation (THG) susceptibility of impurity doped quantum dots (QDs) in the presence and absence of noise. We have invoked Gaussian white noise in the present study. A Gaussian impurity has been introduced into the QD. Noise has been applied to the system additively and multiplicatively. A perpendicular magnetic field emerges out as a confinement source and a static external electric field has been applied. The THG profiles have been pursued as a function of incident photon energy when several important parameters such as electric field strength, magnetic field strength, confinement energy, dopant location, Al concentration, dopant potential, relaxation time and noise strength assume different values. Moreover, the role of the pathway through which noise is applied (additive/multiplicative) on the THG profiles has also been deciphered. The THG profiles are found to be decorated with interesting observations such as shift of THG peak position and maximization/minimization of THG peak intensity. Presence of noise alters the characteristics of THG profiles and sometimes enhances the THG peak intensity. Furthermore, the mode of application of noise (additive/multiplicative) also regulates the THG profiles in a few occasions in contrasting manners. The observations highlight the possible scope of tuning the THG coefficient of doped QD systems in the presence of noise and bears tremendous technological importance.

  14. Quantification of collagen distributions in rat hyaline and fibro cartilages based on second harmonic generation imaging

    Science.gov (United States)

    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 wound repair following cartilage injury.

  15. Solid-state three-step model for high-harmonic generation from periodic crystals

    CERN Document Server

    Ikemachi, Takuya; Sato, Takeshi; Yumoto, Junji; Kuwata-Gonokami, Makoto; Ishikawa, Kenichi L

    2016-01-01

    We study high-harmonic generation (HHG) from solids driven by intense laser pulses using the time-dependent Schrodinger equation for a one-dimensional model periodic crystal. Based on the simulation results, we propose a simple model that can quantitatively explain many aspects of solid- state HHG, some of which have been experimentally observed. Incorporating interband tunneling, intraband acceleration, and recombination with the valence-band hole, our model can be viewed as a solid-state counterpart of the familiar three-step model highly successful for gas-phase HHG and provides a unified basis to understand HHG from gaseous media and solid-state materials. The solid-state three-step model describes how, by repeating intraband acceleration and interband tunneling, electrons climb up across multiple conduction bands. The key parameter in predicting the HHG spectrum structure from the band-climbing process is the peak-to-valley (or valley-to-peak) full amplitude of the pulse vector potential $A(t)$. When the...

  16. Low-temperature anomalies of photoinduced second harmonic generation in skutterudites

    CERN Document Server

    Viennois, R; Terki, F; Charar, S; Muntzer, A; Kasperczyk, J; Ravot, D; Tedenac, J C

    2003-01-01

    Photoinduced second harmonic generation (PISHG) was found in skutterudite compounds of CeFe sub 4 Sb sub 1 sub 2 and Ce sub 0 sub . sub 7 Fe sub 3 sub . sub 5 Ni sub 0 sub . sub 5 Sb sub 1 sub 2. Measurements versus temperature, pump-probe delaying time and external magnetic field were performed. The studied compounds belong to moderate heavy fermion compounds (HFC) in the ground state. The PISHG signals appear at 6.8 and 4.9 K for CeFe sub 4 Sb sub 1 sub 2 and Ce sub 0 sub . sub 7 Fe sub 3 sub . sub 5 Ni sub 0 sub . sub 5 Sb sub 1 sub 2 , respectively. We suspect that these signals are due to anharmonic electron-phonon interactions creating a charge density non-centrosymmetry. The observed effects are caused either by a possible phase transition or by drastic changes in the electron structure of the HFC with decreasing temperature.

  17. Optical characterisation of plasmonic nanostructures on planar substrates using second-harmonic generation.

    Science.gov (United States)

    Persechini, Lina; Verre, Ruggero; Smith, Christopher M; Fleischer, Karsten; Shvets, Igor V; Ranjan, Mukesh; Facsko, Stefan; McGilp, John F

    2015-10-05

    Off-normal, polarization dependent second-harmonic generation (SHG) measurements were performed ex situ on plasmonic nanostructures grown by self-assembly on nanopatterned templates. These exploratory studies of Ag nanoparticle (NP) arrays show that the sensitivity of SHG to the local fields, which are modified by the NP size, shape and distribution, makes it a promising fixed wavelength characterization technique that avoids the complexity of spectroscopic SHG. The off-normal geometry provides access to the out-of-plane SH response, which is typically an order-of-magnitude larger than the in-surface-plane response measured using normal incidence, for example in SHG microscopy. By choosing the plane of incidence orthogonal to the NP array direction, it was shown that the p-polarized SH response, as a function of input polarization, is very sensitive to NP morphology, with a change of 20% in the aspect ratio of the NPs producing a variation of a factor of 30 in the easily measureable ratio of the p-polarized SH field strength for s- and p-polarized input. The results show that such a fixed geometry could be used for the in situ characterization of anisotropic nanostructure morphology during growth by self-assembly, which could be particularly useful in situations where rotating the sample may be neither desirable nor easily accomplished.

  18. Effective nonlinearities and multi-wavelength second-harmonic generation in modulated quasi-phase-matching gratings

    DEFF Research Database (Denmark)

    Bang, Ole; Graversen, T. W.; Clausen, Carl A. Balslev

    2000-01-01

    Quasi-phase-matching gratings induces Kerr effects in quadratic nonlinear materials. We show analytically and confirm numerically how modulating the grating changes the effective quadratic and cubic nonlinearities and allows for multi-wavelength second-harmonic generation.......Quasi-phase-matching gratings induces Kerr effects in quadratic nonlinear materials. We show analytically and confirm numerically how modulating the grating changes the effective quadratic and cubic nonlinearities and allows for multi-wavelength second-harmonic generation....

  19. Third Harmonic Generation of a Short Pulse Laser in a Tunnel Ionizing Plasma: Effect of Self-Defocusing

    OpenAIRE

    Niti Kant

    2013-01-01

    Third harmonic generation of a Gaussian short pulse laser in a tunnel ionizing plasma is investigated. A Gaussian short pulse laser propagating through a tunnel ionizing plasma generates third harmonic wave. Inhomogeneity of the electric field along the wavefront of the fundamental laser pulse causes more ionization along the axis of propagation while less ionization off axis, leading to strong density gradient with its maximum on the axis of propagation. The medium acts like a diverging lens...

  20. Autonomous Control of Inverter-Interfaced Distributed Generation Units for Harmonic Current Filtering and Resonance Damping in an Islanded Microgrid

    DEFF Research Database (Denmark)

    Wang, Xiongfei; Blaabjerg, Frede; Chen, Zhe

    2014-01-01

    Harmonic current filtering and resonance damping have become important concerns in the operation and control of the islanded microgrids. To address these challenges, this paper proposes a control method for the inverter-interfaced Distributed Generation (DG) units, which can autonomously share...... the harmonic currents and resonance damping burdens. The approach employs a load compensator, which is based on the decomposition of output current, in addition to the outer droop-based power controller as well as the inner voltage and current controllers. The load compensator consists of a virtual fundamental...... impedance loop for the enhanced reactive power sharing, and a variable harmonic impedance loop which allows to counteract the harmonic voltage drops across the grid-side inductance of DG inverter and also to dampen out harmonic resonance propagation in the microgrid. Lastly, the laboratory tests on a three...

  1. Two-photon photoluminescence and second-harmonic generation from unintentionally doped and semi-insulating GaN crystals

    Science.gov (United States)

    Godiksen, R. H.; Aunsborg, T. S.; Kristensen, P. K.; Pedersen, K.

    2017-11-01

    Unintentionally doped and semi-insulating Fe-doped GaN crystals grown by hydride vapor phase epitaxy have been investigated with two-photon photoluminescence and second-harmonic generation spectroscopy to reveal doping effects on the nonlinear optical properties and thus indirectly on crystal properties. Like for linear luminescence, it is found that Fe doping strongly reduces nonlinear luminescence. Recording of second-harmonic generation spectra in transmission probing bulk properties shows no significant difference between doped and un-doped crystals. Reflected second-harmonic generation probing 50-100 nm at the surface, on the other hand, shows significantly lower signal from the doped sample. Secondary ion mass spectroscopy shows that the Fe concentration is higher at the surface than in the bulk of the doped crystal. It is suggested that this causes higher defect density and degraded order in the surface region, thus reducing the second-harmonic signal.

  2. Hyperglycemia-induced abnormalities in rat and human corneas: the potential of second harmonic generation microscopy.

    Directory of Open Access Journals (Sweden)

    Gaël Latour

    Full Text Available BACKGROUND: Second Harmonic Generation (SHG microscopy recently appeared as an efficient optical imaging technique to probe unstained collagen-rich tissues like cornea. Moreover, corneal remodeling occurs in many diseases and precise characterization requires overcoming the limitations of conventional techniques. In this work, we focus on diabetes, which affects hundreds of million people worldwide and most often leads to diabetic retinopathy, with no early diagnostic tool. This study then aims to establish the potential of SHG microscopy for in situ detection and characterization of hyperglycemia-induced abnormalities in the Descemet's membrane, in the posterior cornea. METHODOLOGY/PRINCIPAL FINDINGS: We studied corneas from age-matched control and Goto-Kakizaki rats, a spontaneous model of type 2 diabetes, and corneas from human donors with type 2 diabetes and without any diabetes. SHG imaging was compared to confocal microscopy, to histology characterization using conventional staining and transmitted light microscopy and to transmission electron microscopy. SHG imaging revealed collagen deposits in the Descemet's membrane of unstained corneas in a unique way compared to these gold standard techniques in ophthalmology. It provided background-free images of the three-dimensional interwoven distribution of the collagen deposits, with improved contrast compared to confocal microscopy. It also provided structural capability in intact corneas because of its high specificity to fibrillar collagen, with substantially larger field of view than transmission electron microscopy. Moreover, in vivo SHG imaging was demonstrated in Goto-Kakizaki rats. CONCLUSIONS/SIGNIFICANCE: Our study shows unambiguously the high potential of SHG microscopy for three-dimensional characterization of structural abnormalities in unstained corneas. Furthermore, our demonstration of in vivo SHG imaging opens the way to long-term dynamical studies. This method should be easily

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

    Science.gov (United States)

    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.

  4. 2D Arrays of Hexagonal Plasmonic Necklaces for Enhanced Second Harmonic Generation.

    Science.gov (United States)

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

    2017-04-01

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

  5. Controllable nonlocal behaviour by cascaded second-harmonic generation of fs pulses

    DEFF Research Database (Denmark)

    Bache, Morten; Bang, Ole; Krolikowski, Wieslaw

    2008-01-01

    Second-harmonic generation (SHG) of ultra-short pulses can act as a prototypical nonlocal nonlinear model, since the strength and nature of the temporal nonlocality can be controlled through the phase-mismatch parameter. The presence of a group-velocity mismatch namely implies that when the phase...... compression to few-cycle pulses in the cascaded quadratic soliton compressor, the spectral content of the full coupled SHG model is predicted by the nonlocal model even when few-cycle pulses are interacting....

  6. Enhanced third harmonic generation from the epsilon-near-zero modes of ultrathin films

    Energy Technology Data Exchange (ETDEWEB)

    Luk, Ting S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); De Ceglia, Domenico [National Research Council (AMRDEC), Redstone Arsenal, AL (United States); Liu, Sheng [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Keeler, Gordon Arthur [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Prasankumar, Rohit [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Vincenti, Maria A [National Research Council (AMRDEC), Redstone Arsenal, AL (United States); Scalora, Michael [National Research Council (AMRDEC), Redstone Arsenal, AL (United States); Sinclair, Michael B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); campione, salvatore [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-04-13

    We demonstrate, through our experimentation, efficient third harmonic generation from an indium tin oxide nanofilm (λ/42 thick) on a glass substrate for a pump wavelength of 1.4 μm. A conversion efficiency of 3.3 × 10-6 is achieved by exploiting the field enhancement properties of the epsilon-near-zero mode with an enhancement factor of 200. Furthermore, this nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.

  7. Enhanced third harmonic generation from the epsilon-near-zero modes of ultrathin films

    Energy Technology Data Exchange (ETDEWEB)

    Luk, Ting S., E-mail: tsluk@sandia.gov; Liu, Sheng; Campione, Salvatore [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185 (United States); Center for Integrated Nanotechnologies (CINT), Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185 (United States); Ceglia, Domenico de; Vincenti, Maria A. [National Research Council–AMRDEC, Charles M. Bowden Research Laboratory, Redstone Arsenal, Alabama 35898 (United States); Keeler, Gordon A.; Sinclair, Michael B. [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185 (United States); Prasankumar, Rohit P. [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185 (United States); Center for Integrated Nanotechnologies (CINT-LANL), Los Alamos Laboratories, Los Alamos, New Mexico 87545 (United States); Scalora, Michael [Charles M. Bowden Research Laboratory, AMRDEC, U.S. Army RDECOM, Redstone Arsenal, Alabama 35898 (United States)

    2015-04-13

    We experimentally demonstrate efficient third harmonic generation from an indium tin oxide nanofilm (λ/42 thick) on a glass substrate for a pump wavelength of 1.4 μm. A conversion efficiency of 3.3 × 10{sup −6} is achieved by exploiting the field enhancement properties of the epsilon-near-zero mode with an enhancement factor of 200. This nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.

  8. Second-harmonic-generation measurements on ZnSe under high pressure

    CERN Document Server

    Jin Ming Xing; Mukhtar, E; Ding Da Jun

    2002-01-01

    Second-harmonic-generation (SHG) measurements on ZnSe at high pressure, up to 7 GPa, have been reported. The zinc-blende-rock-salt transition pressure has been determined at room temperature from the SHG in ZnSe using a femtosecond laser. The pressure required to induce transformation from a zinc-blende to a rock-salt structure decreases from 11.5 to 1.07 GPa in a femtosecond laser field. SHG can be used to monitor structural changes under pressure of some materials with nonlinear optical properties.

  9. Advances in high-order harmonic generation sources for time-resolved investigations

    Energy Technology Data Exchange (ETDEWEB)

    Reduzzi, Maurizio [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Institute of Photonics and Nanotechnologies, CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Carpeggiani, Paolo [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Kühn, Sergei [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Calegari, Francesca [Institute of Photonics and Nanotechnologies, CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Nisoli, Mauro; Stagira, Salvatore [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Institute of Photonics and Nanotechnologies, CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Vozzi, Caterina [Institute of Photonics and Nanotechnologies, CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Dombi, Peter [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Wigner Research Center for Physics, 1121 Budapest (Hungary); Kahaly, Subhendu [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Tzallas, Paris; Charalambidis, Dimitris [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Foundation for Research and Technology – Hellas, Institute of Electronic Structure and Lasers, P.O. Box 1527, GR-711 10 Heraklion, Crete (Greece); Varju, Katalin [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Department of Optics and Quantum Electronics, University of Szeged, Dóm tér 9, 6720 Szeged (Hungary); Osvay, Karoly [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); and others

    2015-10-15

    We review the main research directions ongoing in the development of extreme ultraviolet sources based on high-harmonic generation for the synthesization and application of trains and isolated attosecond pulses to time-resolved spectroscopy. A few experimental and theoretical works will be discussed in connection to well-established attosecond techniques. In this context, we present the unique possibilities offered for time-resolved investigations on the attosecond timescale by the new Extreme Light Infrastructure Attosecond Light Pulse Source, which is currently under construction.

  10. Investigation of Heavily Doped Congruent Lithium Tantalite for Single-pass Second Harmonic Generation

    OpenAIRE

    Farsi, Mohammad Vahid

    2013-01-01

    Treball final de màster oficial fet en col·laboració amb Universitat Autònoma de Barcelona (UAB), Universitat de Barcelona (UB) i Institut de Ciències Fotòniques (ICFO) [ANGLÈS] We report a compact , practical, green sources based on single-pass second harmonic generation(SHG) of a picosecond Yb-fiber laser in 10-mm-long, heavily MgO doped congruent lithium tantalite (MgO:cPPLT). The fundamental pump source is 20 ps Yb-fiber laser operating at a repetition rate of 80 MHz. The green source ...

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

    Science.gov (United States)

    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.

  12. Orbital-angular-momentum mixing in type-II second-harmonic generation

    Science.gov (United States)

    Pereira, Leonardo J.; Buono, Wagner T.; Tasca, Daniel S.; Dechoum, Kaled; Khoury, Antonio Z.

    2017-11-01

    We investigate the nonlinear mixing of orbital angular momentum in type-II second-harmonic generation with arbitrary topological charges imprinted on two orthogonally polarized beams. Starting from the basic nonlinear equations for the interacting fields, we derive the selection rules determining the set of paraxial modes taking part in the interaction. Conservation of orbital angular momentum naturally appears as the topological charge selection rule. However, a less intuitive rule applies to the radial orders when modes carrying opposite helicities are combined in the nonlinear crystal, an intriguing feature confirmed by experimental measurements.

  13. Global Harmonization of Comparator Products for Bioequivalence Studies.

    Science.gov (United States)

    Gwaza, Luther; Gordon, John; Leufkens, Hubert; Stahl, Matthias; García-Arieta, Alfredo

    2017-05-01

    Comparator products should be the products that were shown to be safe and efficacious in pivotal clinical trials to ensure prescribability of generics. The use of a common comparator ensures switchability between generics. The selection of the comparator is a national responsibility and may be different between countries. This paper discusses the current recommendations on selection of comparators, the associated problems, and the possibility of harmonization. Most countries follow the World Health Organization (WHO) recommendations for selecting comparator products and require the comparator product to be obtained from their national markets to ensure switchability between the local comparator and their generics. These recommendations are only feasible in the few countries where the repetition of the bioequivalence study is economically feasible, but they are impracticable in all other countries. Furthermore, the exclusive use of the local comparator to ensure switchability is ethically and scientifically questionable. The innovator product from well-regulated markets should be the global comparator. This harmonization is feasible as the concept already applies in the WHO prequalification program. It is ineffectual to harmonize only the requirements for performing bioequivalence studies, if such a study has to be repeated for every single country simply because of the different comparator products.

  14. Evaluation of Therapeutic Tissue Crosslinking (TXL) for Myopia Using Second Harmonic Generation Signal Microscopy in Rabbit Sclera

    Science.gov (United States)

    Zyablitskaya, Mariya; Takaoka, Anna; Munteanu, Emilia L.; Nagasaki, Takayuki; Trokel, Stephen L.; Paik, David C.

    2017-01-01

    Purpose Second harmonic generation signals (SHG) are emitted preferentially from collagenous tissue structures and have been used to evaluate photochemically-induced (CXL) crosslinking changes in the cornea. Since therapeutic tissue crosslinking (TXL) using sodium hydroxymethylglycinate (SMG) of the sclera is a potential treatment for high myopia, we explored the use of SHG microscopy to evaluate the effects. Methods Single sub-Tenon's (sT) injections (400 μL) using SMG (40–400 mM) were made at the equatorial 12 o'clock position of the right eye of cadaveric rabbit heads (n = 16 pairs). After 3.5 hours, confocal microscopy (CM) was performed using 860 nm two-photon excitation and 400 to 450 nm emission. Pixel density and fiber bundle “waviness” analyses were performed on the images. Crosslinking effects were confirmed using thermal denaturation (Tm) temperature. Comparison experiments with riboflavin photochemical crosslinking were done. Results Therapeutic tissue crosslinking localization studies indicated that crosslinking changes occurred at the site of injection and in adjacent sectors. Second harmonic generation signals revealed large fibrous collagenous bundled structures that displayed various degrees of waviness. Histogram analysis showed a nearly 6-fold signal increase in 400 mM SMG over 40 mM. This corresponded to a ΔTm = 13°C for 400 mM versus ΔTm = 4°C for 40 mM. Waviness analysis indicated increased fiber straightening as a result of SMG CXL. Conclusions Second harmonic generation signal intensity and fiber bundle waviness is altered by scleral tissue crosslinking using SMG. These changes provide insights into the macromolecular changes that are induced by therapeutic crosslinking technology and may provide a method to evaluate connective tissue protein changes induced by scleral crosslinking therapies. PMID:28055099

  15. Pseudo-spectral Maxwell solvers for an accurate modeling of Doppler harmonic generation on plasma mirrors with Particle-In-Cell codes

    CERN Document Server

    Blaclard, G; Lehe, R; Vay, J L

    2016-01-01

    With the advent of PW class lasers, the very large laser intensities attainable on-target should enable the production of intense high order Doppler harmonics from relativistic laser-plasma mirrors interactions. At present, the modeling of these harmonics with Particle-In-Cell (PIC) codes is extremely challenging as it implies an accurate description of tens of harmonic orders on a a broad range of angles. In particular, we show here that standard Finite Difference Time Domain (FDTD) Maxwell solvers used in most PIC codes partly fail to model Doppler harmonic generation because they induce numerical dispersion of electromagnetic waves in vacuum which is responsible for a spurious angular deviation of harmonic beams. This effect was extensively studied and a simple toy-model based on Snell-Descartes law was developed that allows us to finely predict the angular deviation of harmonics depending on the spatio-temporal resolution and the Maxwell solver used in the simulations. Our model demonstrates that the miti...

  16. Visible quasi-phase-matched harmonic generation by electric-field-poled lithium niobate

    Science.gov (United States)

    Miller, Gregory D.; Batchko, Robert G.; Fejer, Martin M.; Byer, Robert L.

    1996-05-01

    Laser-based displays and illumination systems are applications which can capitalize on the brightness and efficiency of semiconductor lasers, provided that there is a means for converting their output into the visible spectrum. Semiconductor laser manufacturers can adjust their processes to achieve desired wavelengths in several near-infrared bands; an equally agile conversion technology is needed to permit display and illumination system manufacturers to choose visible wavelengths appropriate to their products. Quasi- phasematched second harmonic generation has the potential to convert high-power semiconductor laser output to the visible with 50% optical-to-optical conversion efficiency in a single-pass bulk configuration, using electric-field-poled lithium niobate. Lithographically- defined electrode structures on the positive or negative polar faces of this crystal are used to control the formation of domains under the influence of electric fields applied using those electrode structures. The quality of the resulting domain patterns not only controls the efficiency of quasi-phasematched second harmonic generation, but also controls the degree of resistance to photorefractive damage. We present a model which is used to identify the optimum electrode duty cycle and applied poling field for domain patterning and compare the predicted domain duty cycle with experimental results. We discuss factors which contribute to inhomogeneous domain pattern quality for samples poled under otherwise ideal conditions and our progress in limiting their influence. Finally, we present optical characterization of a 2.4 mm long 500 micrometers thick sample which produced an average second harmonic power of 1.3 W of 532 nm green from a 9 W average power Q-switched 1064 nm Nd:YAG laser in a loose- focus single-pass configuration.

  17. Inspecting the surface of implanted Si(111) during annealing by reflective second harmonic generation: The influence of chamber pressure

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chung-Wei; Chang, Shoou-Jinn [Institute of Microelectronics and Department of Electrical Engineering and Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701, Taiwan (China); Liu, Chun-Chu [Department of Electrophysics, National Chia Yi University, Chia Yi 600, Taiwan (China); Lo, Kuang-Yao, E-mail: kuanglo@mail.ncyu.edu.tw [Department of Electrophysics, National Chia Yi University, Chia Yi 600, Taiwan (China); Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701, Taiwan (China)

    2013-02-01

    The present study used the reflective second harmonic generation (RSHG) method to analyze the quality of the surface layer of implanted Si(111) and to discuss the influence of chamber pressure during rapid thermal annealing. Under a lower chamber pressure, the recrystallization is better, and the defects are eliminated for a higher implanted dose because dopant phosphorus (P) atoms on the surface region more easily out-diffuse at lower chamber pressures. Thus, the occurrence of less out-diffusion makes more P atoms remain on the surface layer and causes larger defects, especially for higher implanted doses. Defects on the surface region are influenced by chamber pressure. In the current work, the RSHG results showed more detailed information by linking secondary ion mass spectrometry and sheet resistance measurement. - Highlights: ► Rapid thermal annealing (RTA) with different chamber pressures was performed. ► The quality of implanted Si was analyzed by reflective second harmonic generation. ► High-dose implanted Si is obviously influenced by the pressure in the RTA chamber. ► Pressure in the RTA chamber affects the generation of defects. ► Defect suppression is obvious at relatively low chamber pressure.

  18. Nonlinear generation of harmonics through the interaction of an internal wave beam with a model oceanic pycnocline

    Science.gov (United States)

    Diamessis, P. J.; Wunsch, S.; Delwiche, I.; Richter, M. P.

    2014-06-01

    The interaction of an internal wave beam (IWB) with an idealized oceanic pycnocline is examined using two-dimensional fully nonlinear direct numerical simulations based on a spectral multidomain penalty method in the vertical direction. The phenomenon of focus is the nonlinear generation of harmonics. A total of 24 simulations have been performed, varying the normalized pycnocline thickness and the ratio of peak pycnocline Brunt-Väisälä frequency to that of the stratified lower layer. Harmonics at the point of IWB entry into the pycnocline increase in amplitude and number with a measure of the maximum gradient of the Brunt-Väisälä frequency, suggesting refraction as an important factor in harmonic generation. Among the simulations performed, two distinct limits of pycnocline thickness are identified. For thin pynoclines, whose thickness is 10% of the incident IWB's horizontal wavelength, harmonics trapped within the pycnocline have maximum amplitude when their frequency and wavenumber match those of the natural pycnocline interfacial wave mode. Results in this case are compared with weakly nonlinear theory for harmonic generation by plane wave refraction. For thicker pycnoclines, whose thickness is equal the incident IWB's horizontal wavelength, IWB refraction results in harmonic generation at multiple locations in addition to pycnocline entry, giving rise to complex flow structure inside the pycnocline.

  19. Three-dimensional mapping of single gold nanoparticles embedded in a homogeneous transparent matrix using optical second-harmonic generation.

    Science.gov (United States)

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

    2010-10-11

    We report the three-dimensional mapping of 150 nm gold metallic nanoparticles dispersed in a homogeneous transparent polyacrylamide matrix using second-harmonic generation. We demonstrate that the position of single nanoparticles can be well defined using only one incident fundamental beam and the harmonic photon detection performed at right angle. The fundamental laser beam properties are determined using its spatial autocorrelation function and used to prove that single nanoparticles are observed. Polarization resolved measurements are also performed allowing for a clear separation of the second-harmonic response of the single gold metallic nanoparticles from that of aggregates of such nanoparticles.

  20. Investigation of phase matching for third-harmonic generation in silicon slow light photonic crystal waveguides using Fourier optics.

    Science.gov (United States)

    Monat, Christelle; Grillet, Christian; Corcoran, Bill; Moss, David J; Eggleton, Benjamin J; White, Thomas P; Krauss, Thomas F

    2010-03-29

    Using Fourier optics, we retrieve the wavevector dependence of the third-harmonic (green) light generated in a slow light silicon photonic crystal waveguide. We show that quasi-phase matching between the third-harmonic signal and the fundamental mode is provided in this geometry by coupling to the continuum of radiation modes above the light line. This process sustains third-harmonic generation with a relatively high efficiency and a substantial bandwidth limited only by the slow light window of the fundamental mode. The results give us insights into the physics of this nonlinear process in the presence of strong absorption and dispersion at visible wavelengths where bandstructure calculations are problematic. Since the characteristics (e.g. angular pattern) of the third-harmonic light primarily depend on the fundamental mode dispersion, they could be readily engineered.

  1. Simultaneous Second Harmonic Generation of Multiple Wavelength Laser Outputs for Medical Sensing

    Directory of Open Access Journals (Sweden)

    Chang-Seok Kim

    2011-06-01

    Full Text Available Multiple wavelength light sources in the medical spectral window region are useful for various medical sensing applications in tissue by distinguishing the absorption and scattering coefficients optically. We propose a simultaneous second harmonic generation of multiple wavelength fiber laser output using parallel channels of periodically-poled lithium niobate (PPLN waveguides. High intensity dual wavelength lasing output is experimentally realized with two tunable fiber Bragg gratings of 1,547.20 nm and 1,554.48 nm for the efficient conversion to the half wavelengths, 773.60 nm and 777.24 nm, by using two parallel PPLN channels. Compared with a conventional dual second harmonic generation (SHG configuration based on two different input wavelengths from each independent light source, this method has a relatively higher efficiency to align the input light beam into the adjacent parallel PPLN channels simultaneously. The use of fiber lasers offers several advantages since they are relatively inexpensive, provide high power in excess of tens of watts, are widely tunable, and can produce pulses from milliseconds to femtoseconds.

  2. Simultaneous Second Harmonic Generation of Multiple Wavelength Laser Outputs for Medical Sensing

    Science.gov (United States)

    Son, Seung Nam; Song, Jae-Jin; Kang, Jin U.; Kim, Chang-Seok

    2011-01-01

    Multiple wavelength light sources in the medical spectral window region are useful for various medical sensing applications in tissue by distinguishing the absorption and scattering coefficients optically. We propose a simultaneous second harmonic generation of multiple wavelength fiber laser output using parallel channels of periodically-poled lithium niobate (PPLN) waveguides. High intensity dual wavelength lasing output is experimentally realized with two tunable fiber Bragg gratings of 1,547.20 nm and 1,554.48 nm for the efficient conversion to the half wavelengths, 773.60 nm and 777.24 nm, by using two parallel PPLN channels. Compared with a conventional dual second harmonic generation (SHG) configuration based on two different input wavelengths from each independent light source, this method has a relatively higher efficiency to align the input light beam into the adjacent parallel PPLN channels simultaneously. The use of fiber lasers offers several advantages since they are relatively inexpensive, provide high power in excess of tens of watts, are widely tunable, and can produce pulses from milliseconds to femtoseconds. PMID:22163945

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

    Science.gov (United States)

    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.

  4. UV by the fourth harmonic generation of compact side-pumped Yb:YAG laser emission

    Science.gov (United States)

    Cole, Brian; McIntosh, Chris; Hays, Alan; Dilazaro, Tom; Goldberg, Lew

    2016-03-01

    We present a compact, side pumped passively Q-switched Yb:YAG laser that was operated in a burst mode with pump durations of 2-4 ms at low duty cycles. Intra-pump pulse Q-switched pulse repetition frequencies varied from 5-20 kHz depending on the transmission of the Cr:YAG saturable absorber, which was varied from 70% to 94%. Pump duration, pulse repetition frequency and output coupler reflectivity were optimized to yield maximum Yb:YAG laser average power and laser efficiency, while providing sufficient peak intensity, typically 0.3-1 MW, to enable efficient forth harmonic generation (FHG). Pulse energies and durations were in ranges of 0.3-1.8 mJ and 1.5-7ns, respectively, dependent on the unbleached transmission of the Cr:YAG saturable absorber. We achieved an optical efficiency of greater than 15% for the Yb:YAG laser. Extra-cavity 515 nm second harmonic generation (SHG) was achieved using a 5mm long KTP crystal. The 515 nm light was then frequency doubled by focusing it into a 7mm long BBO crystal, resulting in a 15% conversion efficiency from 1030nm to 257.5 nm, with an average UV power greater than 100 mW.

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

    Science.gov (United States)

    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.

  6. Modified Perfect Harmonics Cancellation Control of a Grid Interfaced SPV Power Generation

    Science.gov (United States)

    Singh, B.; Shahani, D. T.; Verma, A. K.

    2015-03-01

    This paper deals with a grid interfaced solar photo voltaic (SPV) power generating system with modified perfect harmonic cancellation (MPHC) control for power quality improvement in terms of mitigation of the current harmonics, power factor correction, control of point of common coupling (PCC) voltage with reactive power compensation and load balancing in a three phase distribution system. The proposed grid interfaced SPV system consists of a SPV array, a dc-dc boost converter and a voltage source converter (VSC) used for the compensation of other connected linear and nonlinear loads at PCC. The reference grid currents are estimated using MPHC method and control signals are derived by using pulse width modulation (PWM) current controller of VSC. The SPV power is fed to the common dc bus of VSC and dc-dc boost converter using maximum power point tracking (MPPT). The dc link voltage of VSC is regulated by using dc voltage proportional integral (PI) controller. The analysis of the proposed SPV power generating system is carried out under dc/ac short circuit and severe SPV-SX and SPV-TX intrusion.

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

    Energy Technology Data Exchange (ETDEWEB)

    Gajić, A. [School of Electrical Engineering, University of Belgrade, Bulevar kralja Aleksandra 73, 11120 Belgrade (Serbia); Telekom Srbija, a.d., Takovska 2, 11000 Belgrade (Serbia); Radovanović, J., E-mail: radovanovic@etf.bg.ac.rs; Milanović, V. [School of Electrical Engineering, University of Belgrade, Bulevar kralja Aleksandra 73, 11120 Belgrade (Serbia); Indjin, D.; Ikonić, Z. [School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom)

    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.

  8. Molecular imaging of melanin distribution in vivo and quantitative differential diagnosis of human pigmented lesions using label-free harmonic generation biopsy (Conference Presentation)

    Science.gov (United States)

    Sun, Chi-Kuang; Wei, Ming-Liang; Su, Yu-Hsiang; Weng, Wei-Hung; Liao, Yi-Hua

    2017-02-01

    Harmonic generation microscopy is a noninvasive repetitive imaging technique that provides real-time 3D microscopic images of human skin with a sub-femtoliter resolution and high penetration down to the reticular dermis. In this talk, we show that with a strong resonance effect, the third-harmonic-generation (THG) modality provides enhanced contrast on melanin and allows not only differential diagnosis of various pigmented skin lesions but also quantitative imaging for longterm tracking. This unique capability makes THG microscopy the only label-free technique capable of identifying the active melanocytes in human skin and to image their different dendriticity patterns. In this talk, we will review our recent efforts to in vivo image melanin distribution and quantitatively diagnose pigmented skin lesions using label-free harmonic generation biopsy. This talk will first cover the spectroscopic study on the melanin enhanced THG effect in human cells and the calibration strategy inside human skin for quantitative imaging. We will then review our recent clinical trials including: differential diagnosis capability study on pigmented skin tumors; as well as quantitative virtual biopsy study on pre- and post- treatment evaluation on melasma and solar lentigo. Our study indicates the unmatched capability of harmonic generation microscopy to perform virtual biopsy for noninvasive histopathological diagnosis of various pigmented skin tumors, as well as its unsurpassed capability to noninvasively reveal the pathological origin of different hyperpigmentary diseases on human face as well as to monitor the efficacy of laser depigmentation treatments. This work is sponsored by National Health Research Institutes.

  9. Influence of the intracavity second harmonic generation on the mode competition in a double-mode diode-pumped Nd : YAG laser

    NARCIS (Netherlands)

    Yermachenko, VM; Karle, RA; Petrovskiy, VN; Protsenko, ED

    The influence of intracavity second harmonic generation on the mode competition in a double-mode diode-pumped Nd:YAG laser is studied theoretically and experimentally. Various configurations of the optical cavity with II-type phase-matching frequency-doubling crystals are considered. The conditions

  10. harmonic load modeling: a case study of 33 kv abuja steel mill feeder

    African Journals Online (AJOL)

    HOD

    An in-depth study of the harmonic orders inherent in a power system network is required before mitigation techniques are adopted. This paper studied the harmonic orders of the 33 kV Abuja Steel Feeder modeled as a harmonic source using measured data. Readings of kW, kVar, kV and Hz were obtained using power ...

  11. Trajectory analysis of high-order-harmonic generation from periodic crystals

    Science.gov (United States)

    Ikemachi, Takuya; Shinohara, Yasushi; Sato, Takeshi; Yumoto, Junji; Kuwata-Gonokami, Makoto; Ishikawa, Kenichi L.

    2017-04-01

    We theoretically study high-order-harmonic generation (HHG) from solids driven by intense laser pulses using a one-dimensional model periodic crystal. By numerically solving the time-dependent Schrödinger equation directly on a real-space grid, we successfully reproduce experimentally observed unique features of solid-state HHG such as the linear cutoff-energy scaling and the sudden transition from a single- to multiple-plateau structure. Based on the simulation results, we propose a simple model that incorporates vector-potential-induced intraband displacement, interband tunneling, and recombination with the valence-band hole. One key parameter is the peak-to-valley amplitude of the pulse vector potential, which determines the crystal momentum displacement during the half cycle. When the maximum peak-to-valley amplitude Apeak reaches the half width π/a of the Brillouin zone with a being the lattice constant, the HHG spectrum exhibits a transition from a single- to multiple-plateau structure, and even further plateaus appear at Apeak=2/π a ,3/π a ,⋯ . The multiple cutoff positions are given as functions of Apeak and the second maximum Apeak', in terms of the energy difference between different bands. Using our recipe, one can draw electron trajectories in the momentum space, from which one can deduce, for example, the time-frequency structure of HHG without elaborate quantum-mechanical calculations. Finally, we reveal that the cutoff positions depend on not only the intensity and wavelength of the pulse, but also its duration, in marked contrast to the gas-phase case. Our model can be viewed as a solid-state and momentum-space counterpart of the familiar three-step model, highly successful for gas-phase HHG, and provide a unified basis to understand HHG from solid-state materials and gaseous media.

  12. Energetics of nonlinear harmonic generation during the incidence of an internal wave beam on a model oceanic pycnocline

    Science.gov (United States)

    Aksu, Anil; Peter, Diamessis; Wunsch, Scott

    2014-11-01

    An energetic analysis of the interaction of a numerically simulated IWB with a model ocean pycnocline is presented. The focus is on the nonlinear generation of harmonics. The analysis consists of a) monitoring the transfer of the primary beam's energy into higher harmonics along the beam path and b) evaluating how any energy trapped inside the pycnocline is distributed across different wave frequencies propagating within it. The majority of the analysis is performed on a dataset spanning a wide range of pycnocline strengths and thicknesses restricted to an IWB propagating at 45° from the horizontal. For such an angle, internal wave refraction is the primary driver of nonlinear harmonic generation. Moreover, all resulting harmonics remain trapped within the pycnocline. Preliminary results from additional simulations with shallower angles of IWB incidence are also analyzed. When the incidence angle is less than 30 degrees, IWB reflection is an additional important mechanism of harmonic generation and lower harmonics are able to radiate back out of the pycnocline.

  13. Second Harmonic Generation Imaging Analysis of Collagen Arrangement in Human Cornea.

    Science.gov (United States)

    Park, Choul Yong; Lee, Jimmy K; Chuck, Roy S

    2015-08-01

    To describe the horizontal arrangement of human corneal collagen bundles by using second harmonic generation (SHG) imaging. Human corneas were imaged with an inverted two photon excitation fluorescence microscope. The excitation laser (Ti:Sapphire) was tuned to 850 nm. Backscatter signals of SHG were collected through a 425/30-nm bandpass emission filter. Multiple, consecutive, and overlapping image stacks (z-stacks) were acquired to generate three dimensional data sets. ImageJ software was used to analyze the arrangement pattern (irregularity) of collagen bundles at each image plane. Collagen bundles in the corneal lamellae demonstrated a complex layout merging and splitting within a single lamellar plane. The patterns were significantly different in the superficial and limbal cornea when compared with deep and central regions. Collagen bundles were smaller in the superficial layer and larger in deep lamellae. By using SHG imaging, the horizontal arrangement of corneal collagen bundles was elucidated at different depths and focal regions of the human cornea.

  14. B-spline algebraic diagrammatic construction: application to photoionization cross-sections and high-order harmonic generation.

    Science.gov (United States)

    Ruberti, M; Averbukh, V; Decleva, P

    2014-10-28

    We present the first implementation of the ab initio many-body Green's function method, algebraic diagrammatic construction (ADC), in the B-spline single-electron basis. B-spline versions of the first order [ADC(1)] and second order [ADC(2)] schemes for the polarization propagator are developed and applied to the ab initio calculation of static (photoionization cross-sections) and dynamic (high-order harmonic generation spectra) quantities. We show that the cross-section features that pose a challenge for the Gaussian basis calculations, such as Cooper minima and high-energy tails, are found to be reproduced by the B-spline ADC in a very good agreement with the experiment. We also present the first dynamic B-spline ADC results, showing that the effect of the Cooper minimum on the high-order harmonic generation spectrum of Ar is correctly predicted by the time-dependent ADC calculation in the B-spline basis. The present development paves the way for the application of the B-spline ADC to both energy- and time-resolved theoretical studies of many-electron phenomena in atoms, molecules, and clusters.

  15. Sub-cycle ionization dynamics revealed by trajectory resolved, elliptically-driven high-order harmonic generation

    Science.gov (United States)

    Larsen, E. W.; Carlström, S.; Lorek, E.; Heyl, C. M.; Paleček, D.; Schafer, K. J.; L’Huillier, A.; Zigmantas, D.; Mauritsson, J.

    2016-01-01

    The sub-cycle dynamics of electrons driven by strong laser fields is central to the emerging field of attosecond science. We demonstrate how the dynamics can be probed through high-order harmonic generation, where different trajectories leading to the same harmonic order are initiated at different times, thereby probing different field strengths. We find large differences between the trajectories with respect to both their sensitivity to driving field ellipticity and resonant enhancement. To accurately describe the ellipticity dependence of the long trajectory harmonics we must include a sub-cycle change of the initial velocity distribution of the electron and its excursion time. The resonant enhancement is observed only for the long trajectory contribution of a particular harmonic when a window resonance in argon, which is off-resonant in the field-free case, is shifted into resonance due to a large dynamic Stark shift. PMID:27991521

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

    Science.gov (United States)

    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.

  17. Efficient enhancement of below-threshold harmonic generation by laser-driven excited states of Cs atom

    Science.gov (United States)

    Guo, Qiao-Ling; Li, Peng-Cheng; Zhou, Xiao-Xin; Chu, Shih-I.

    2018-03-01

    We propose an efficient method for the enhancement of below-threshold harmonic generation (BTHG) by mid-infrared laser-driven excited states of a Cs atom. The BTHG is calculated by solving three-dimensional time-dependent Schrödinger equation accurately and efficiently using the time-dependent generalized pseudospectral method. We adopt an excited state as the initial state of a Cs atom. As a result, the BTHG is significantly enhanced by two orders of magnitude compared with the case of the initial ground state. Furthermore, we find that a single vacuum-ultraviolet pulse can be generated by mid-infrared laser-driven excited states by superposing several below-threshold harmonics of a Cs atom. Our finding suggests that the generation of below-threshold harmonics by laser-driven excited states of an atom can provide a powerful methodology for the production of intense vacuum-ultraviolet pulses.

  18. The sum of the reduced harmonic series generated by four primes determined analytically and computed by using CAS Maple

    Directory of Open Access Journals (Sweden)

    Radovan Potucek

    2013-12-01

    Full Text Available The paper deals with the reduced harmonic series generated by four primes. A formula for the sum of these convergent reduced harmonic series is derived. These sums (concretely 42 from all 12650 sums generated by four different primes smaller than 100 are computed by using the computer algebra system Maple 15 and its programming language, although the formula is valid not only for four arbitrary primes, but also for four integers. We can say that the reduced harmonic series generated by four primes (or by four integers belong to special types of convergent infinite series, such as geometric and telescoping series, which sum can be found analytically by means of a simple formula.

  19. Probabilistic Harmonic Modeling of Wind Power Plants

    DEFF Research Database (Denmark)

    Guest, Emerson; Jensen, Kim H.; Rasmussen, Tonny Wederberg

    2017-01-01

    A probabilistic sequence domain (SD) harmonic model of a grid-connected voltage-source converter is used to estimate harmonic emissions in a wind power plant (WPP) comprised of Type-IV wind turbines. The SD representation naturally partitioned converter generated voltage harmonics into those...... with deterministic phase and those with probabilistic phase. A case study performed on a string of ten 3MW, Type-IV wind turbines implemented in PSCAD was used to verify the probabilistic SD harmonic model. The probabilistic SD harmonic model can be employed in the planning phase of WPP projects to assess harmonic...

  20. Second-harmonic generation of cylindrical electromagnetic waves propagating in an inhomogeneous and nonlinear medium.

    Science.gov (United States)

    Xiong, Hao; Si, Liu-Gang; Ding, Chunling; Yang, Xiaoxue; Wu, Ying

    2012-01-01

    A general description of cylindrical electromagnetic waves propagating in nonlinear and inhomogeneous media is given by deducing cylindrical coupled-wave equations. Based on the cylindrical coupled-wave equations, we analyze second-harmonic generation (SHG) of some special cases of inhomogeneity, and find that the inhomogeneity of the first- and second-order polarization can influence the amplitude of the SHG. From a different point of view, exact solutions of cylindrical electromagnetic waves propagating in a nonlinear medium with a special case of inhomogeneity have been obtained previously. We show that cylindrical SHG in an inhomogeneous and nonlinear medium can also be deduced from exact solutions. As verification, we compare the results obtained from the two different methods and find that descriptions of SHG by the coupled-wave equations are in good agreement with the exact solutions.

  1. Scaling high-order harmonic generation from laser-solid interactions to ultrahigh intensity.

    Science.gov (United States)

    Dollar, F; Cummings, P; Chvykov, V; Willingale, L; Vargas, M; Yanovsky, V; Zulick, C; Maksimchuk, A; Thomas, A G R; Krushelnick, K

    2013-04-26

    Coherent x-ray beams with a subfemtosecond (scale length, which can strongly influence the harmonic generation mechanism. It is shown that for intensities in excess of 10(21)  W cm(-2) an optimum density ramp scale length exists that balances an increase in efficiency with a growth of parametric plasma wave instabilities. We show that for these higher intensities the optimal scale length is c/ω0, for which a variety of HOHG properties are optimized, including total conversion efficiency, HOHG divergence, and their power law scaling. Particle-in-cell simulations show striking evidence of the HOHG loss mechanism through parametric instabilities and relativistic self-phase modulation, which affect the produced spectra and conversion efficiency.

  2. Rotational second harmonic generation endoscopy with 1μm fiber laser system

    Science.gov (United States)

    Liu, Gangjun; Xie, Tuqiang; Yu, Lingfeng; Su, Jianping; Tomov, Ivan V.; Wang, Qiang; Rao, Bin; Zhang, Jun; Chen, Zhongping

    2009-02-01

    We present a kind of rotational two photon mciroendoscopy for 1μm fiber femtosecond laser. The fiber laser provide ultrashort femto-second pulses with center wavelength at 1.034μm and repetition rate of 50MH. The rotational probe is based on double cladding photonic crystal fiber (CD PCF) fiber, Grin lens, microprism and rotational MEMS motor. The MEMS motor has diameter of 2.2mm and can provide 360 degree full view rotation. We experimentally show that the DC PCF fiber works for 1μm fiber laser two photon system. Second harmonic generation (SHG) singnal line profile of rat tail tendon and fish scale was taken with the endoscopy system.

  3. Broadband second-harmonic generation in APPLN with group-velocity matching

    Science.gov (United States)

    Jiang, Jian; Zhang, Jiandong; Wang, Kai; Xiao, Xuan; Zhang, Zuxing

    2017-11-01

    In this paper, we present a method to increase the acceptance bandwidth of second harmonic generation (SHG) with 5 mol% MgO-doped aperiodically poled lithium niobate (APPLN) when the conditions of quasi-phase-matching and group-velocity matching are satisfied simultaneously. The APPLN, with a length of 10 mm, has 3333 uniform domains, with the polarization directions of each domain optimized by a genetic algorithm, to obtain the profile of nonlinear coefficients in the communication band. By adjusting the positions and quantities of the fundamental wavelengths appropriately, the evolution of bandwidths is investigated theoretically. The simulation results show that the acceptance bandwidth of SHG is approximately 243.3 nm for type-I (o + o → e) interaction around the wavelength of zero-group-velocity dispersion in crystal, which is enhanced by 4.5 times that of periodic structures.

  4. Tunable Room Temperature Second Harmonic Generation in Glasses Doped with CuCI Nanocrystalline Quantum Dots

    Energy Technology Data Exchange (ETDEWEB)

    Thantu, Napoleon; Schley, Robert Scott; B. L. Justus

    2003-05-01

    Two-photon excited emission centered at 379-426 nm in photodarkening borosilicate glass doped with CuCl nanocrystalline quantum dots at room temperature has been observed. The emission is detected in the direction of the fundamental near-infrared beam. Time- and frequency-resolved measurements at room temperature and 77 K indicate that the emission is largely coherent light characteristic of second harmonic generation (SHG). An average conversion efficiency of ~10-10 is obtained for a 2 mm thick sample. The observed SHG can originate in the individual noncentrosymmetric nanocrystals, leading to a bulk-like contribution, and at the nanocrystal-glass interface, leading to a surface contribution. The bulk-like conversion efficiency is estimated using previously reported values of coherence length (5m) and bulk nonlinear susceptibility. This bulk-like conversion efficiency estimate is found to be smaller than the measured value, suggesting a more prominent surface contribution.

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

    CERN Document Server

    Fryett, Taylor K; Zheng, Jiajiu; Liu, Chang-Hua; Xu, Xiaodong; Majumdar, Arka

    2016-01-01

    Nano-resonator integrated with two-dimensional materials (e.g. transition metal dichalcogenides) have recently emerged as a promising nano-optoelectronic platform. Here we demonstrate resonatorenhanced second-harmonic generation (SHG) in tungsten diselenide using a silicon photonic crystal cavity. By pumping the device with the 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.

  6. Acoustically induced optical second harmonic generation in hydrogenated amorphous silicon films

    CERN Document Server

    Ebothe, J; Cabarrocas, P R I; Godet, C; Equer, B

    2003-01-01

    Acoustically induced second harmonic generation (AISHG) in hydrogenated amorphous silicon (a-Si : H) films of different morphology has been observed. We have found that with increasing acoustical power, the optical SHG of Gd : YAB laser light (lambda = 2.03 mu m) increases and reaches its maximum value at an acoustical power density of about 2.10 W cm sup - sup 2. With decreasing temperature, the AISHG signal strongly increases below 48 K and correlates well with the temperature behaviour of differential scanning calorimetry indicating near-surface temperature phase transition. The AISHG maxima were observed at acoustical frequencies of 10-11, 14-16, 20-22 and 23-26 kHz. The independently performed measurements of the acoustically induced IR spectra have shown that the origin of the observed phenomenon is the acoustically induced electron-phonon anharmonicity in samples of different morphology.

  7. Imaging the noncentrosymmetric structural organisation of tissue with Interferometric Second Harmonic Generation microscopy

    CERN Document Server

    Rivard, Maxime; Laliberte, Mathieu; Bertrand-Grenier, Antony; Martin, Francois; Pepin, Henri; Pfeffer, Christian P; Brown, Cameron; Rammuno, Lora; Legare, Francois

    2012-01-01

    We report the imaging of tendon, a connective tissue rich in collagen type I proteins, with Interferometric Second Harmonic Generation (I-SHG) microscopy. We observed that the noncentrosymmetric structural organization can be maintained along the fibrillar axis over more than 150 {\\mu}m, while in the transverse direction it is ~1-15 {\\mu}m. Those results are explained by modeling tendon as a heterogeneous distribution of noncentrosymmetric nanocylinders (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 fraction occupied by fibrils oriented in one direction is larger than in the other.

  8. Dynamical centrosymmetry breaking — A novel mechanism for second harmonic generation in graphene

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, David N. [School of Engineering and Physical Sciences, Heriot-Watt University, EH14 4AS Edinburgh (United Kingdom); Marini, Andrea [ICFO-Institut de Ciencies Fotoniques, 08860 Castelldefels (Barcelona) (Spain); Biancalana, Fabio, E-mail: f.biancalana@hw.ac.uk [School of Engineering and Physical Sciences, Heriot-Watt University, EH14 4AS Edinburgh (United Kingdom)

    2017-03-15

    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.

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

    Directory of Open Access Journals (Sweden)

    Angel A Zeitoune

    2017-01-01

    Full Text Available 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.

  10. Optically induced second-harmonic generation in CdI sub 2 -Cu layered nanocrystals

    CERN Document Server

    Voolless, F; Hydaradjan, W

    2003-01-01

    A large enhancement (up to 0.40 pm V sup - sup 1) of the second-order optical susceptibility was observed in CdI sub 2 -Cu single-layered nanocrystals for the Nd:YAG fundamental laser beam lambda = 1.06 mu m. The Cu impurity content and nanolayer thickness of the cleaved layers (about several nanometres) play a crucial role in the observed effect. The temperature dependence of the optical second-harmonic generation (SHG) together with its correlation with Raman spectra of low-frequency modes indicate a key role for the UV-induced anharmonic electron-phonon interactions in the observed effect. The maximal output UV-induced SHG was achieved for a Cu content of about 0.5% and at liquid helium temperatures.

  11. Random laser action with coherent feedback via second-harmonic generation

    CERN Document Server

    Qiao, Yanqi; Cai, Zengyan; Chen, Xianfeng

    2016-01-01

    The random laser action with coherent feedback by second-harmonic generation (SHG) was experimentally demonstrated in this paper. Compared with the conventional random laser action based on photoluminescence effect, which needs strong photoresponse in the active medium and has a fixed response waveband due to the inherent energy level structure of the material, this random SHG laser action indicates a possible confinement of the nonlinear signal with ring cavities and widens the response waveband due to the flexible frequency conversion in nonlinear process. The combination of coherent random laser and nonlinear optics will provide us another possible way to break phase-matching limitations, with fiber or feedback-based wavefront shaping method to transmit the emission signal directionally. This work suggests potential applications in band-tunable random laser, phase-matching-free nonlinear optics and even brings in new consideration about random nonlinear optics (RNO).

  12. Vibrational excitation of hydrogen molecules by two-photon absorption and third-harmonic generation

    Science.gov (United States)

    Miyamoto, Yuki; Hara, Hideaki; Hiraki, Takahiro; Masuda, Takahiko; Sasao, Noboru; Uetake, Satoshi; Yoshimi, Akihiro; Yoshimura, Koji; Yoshimura, Motohiko

    2018-01-01

    We report the coherent excitation of the vibrational state of hydrogen molecules by two-photon absorption and the resultant third-harmonic generation (THG). Parahydrogen molecules cooled by liquid nitrogen are irradiated by mid-infrared nanosecond pulses at 4.8 μm with a nearly Fourier-transform-limited linewidth. The first excited vibrational state of parahydrogen is populated by two-photon absorption of the mid-infrared photons. Because of the narrow linewidth of the mid-infrared pulses, coherence between the ground and excited states is sufficient to induce higher-order processes. Near-infrared photons from the THG are observed at 1.6 μm. The dependence of the intensity of the near-infrared radiation on mid-infrared pulse energy, target pressure, and cell length is determined. We used a simple formula for THG with consideration of realistic experimental conditions to explain the observed results.

  13. Radial index of Laguerre-Gaussian modes in high-order-harmonic generation

    Science.gov (United States)

    Géneaux, Romain; Chappuis, Céline; Auguste, Thierry; Beaulieu, Samuel; Gorman, Timothy T.; Lepetit, Fabien; DiMauro, Louis F.; Ruchon, Thierry

    2017-05-01

    High-order-harmonic generation (HHG) is a tabletop and tunable source of extreme ultraviolet (XUV) light. Its flexibility was lately evidenced by the production of Laguerre-Gaussian (LG) modes in the XUV with a known azimuthal index. Here we investigate the role of the radial index of LG modes in HHG. We show both numerically and experimentally that the mode content of the emitted XUV radiation can be tuned by controlling the weight of the different quantum trajectories involved in the process. The appearance of high-order radial modes is finally linked to the atomic dipole phase of HHG. These results extend the capabilities of shaping the spatial mode of ultrashort XUV pulses of light.

  14. Resonantly enhanced second-harmonic generation using III-V semiconductor all-dielectric metasurfaces

    CERN Document Server

    Liu, Sheng; Keeler, Gordon A; Sinclair, Michael B; Yang, Yuanmu; Reno, John; Pertsch, Thomas; Brener, Igal

    2016-01-01

    Nonlinear optical phenomena in nanostructured materials have been challenging our perceptions of nonlinear optical processes that have been explored since the invention of lasers. For example, the ability to control optical field confinement, enhancement, and scattering almost independently, allows nonlinear frequency conversion efficiencies to be enhanced by many orders of magnitude compared to bulk materials. Also, the subwavelength length scales render phase matching issues irrelevant. Compared with plasmonic nanostructures, dielectric resonator metamaterials show great promise for enhanced nonlinear optical processes due to their larger mode volumes. Here, we present, for the first time, resonantly enhanced second-harmonic generation (SHG) using Gallium Arsenide (GaAs) based dielectric metasurfaces. Using arrays of cylindrical resonators we observe SHG enhancement factors as large as 104 relative to unpatterned GaAs. At the magnetic dipole resonance we measure an absolute nonlinear conversion efficiency o...

  15. Label-free imaging of lipid depositions in C. elegans using third-harmonic generation microscopy.

    Directory of Open Access Journals (Sweden)

    George J Tserevelakis

    Full Text Available Elucidation of the molecular mechanisms regulating lipid storage and metabolism is essential for mitigating excess adiposity and obesity, which has been associated with increased prevalence of severe pathological conditions such as cardiovascular disorders and type II diabetes, worldwide. However, imaging fatty acid distribution and dynamics in vivo, at the cellular or organismal level is challenging. We developed a label-free method for visualizing lipid depositions in vivo, based on third harmonic generation (THG microscopy. THG imaging requires a single pulsed-laser light source, alleviating the technical challenges of implementing coherent anti-Stokes Raman scattering spectroscopy (CARS to detect fat stores in living cells. We demonstrate that THG can be used to efficiently and reliably visualize lipid droplets in Caenorhabditis elegans. Thus, THG microscopy offers a versatile alternative to fluorescence and dye-based approaches for lipid biology research.

  16. Second Harmonic Generation Guided Raman Spectroscopy for Sensitive Detection of Polymorph Transitions

    Energy Technology Data Exchange (ETDEWEB)

    Chowdhury, Azhad U.; Ye, Dong Hye; Song, Zhengtian; Zhang, Shijie; Hedderich, Hartmut G.; Mallick, Babita; Thirunahari, Satyanarayana; Ramakrishnan, Srividya; Sengupta, Atanu; Gualtieri, Ellen J.; Bouman, Charles A.; Simpson, Garth J. (Purdue); (IPDO)

    2017-05-08

    Second harmonic generation (SHG) was integrated with Raman spectroscopy for the analysis of pharmaceutical materials. Particulate formulations of clopidogrel bisulfate were prepared in two crystal forms (Form I and Form II). Image analysis approaches enable automated identification of particles by bright field imaging, followed by classification by SHG. Quantitative SHG microscopy enabled discrimination of crystal form on a per particle basis with 99.95% confidence in a total measurement time of ~10 ms per particle. Complementary measurements by Raman and synchrotron XRD are in excellent agreement with the classifications made by SHG, with measurement times of ~1 min and several seconds per particle, respectively. Coupling these capabilities with at-line monitoring may enable real-time feedback for reaction monitoring during pharmaceutical production to favor the more bioavailable but metastable Form I with limits of detection in the ppm regime.

  17. Harmonization of detailed clinical models with clinical study data standards.

    Science.gov (United States)

    Jiang, G; Evans, J; Oniki, T A; Coyle, J F; Bain, L; Huff, S M; Kush, R D; Chute, C G

    2015-01-01

    This article is part of the Focus Theme of METHODS of Information in Medicine on "Managing Interoperability and Complexity in Health Systems". Data sharing and integration between the clinical research data management system and the electronic health record system remains a challenging issue. To approach the issue, there is emerging interest in utilizing the Detailed Clinical Model (DCM) approach across a variety of contexts. The Intermountain Healthcare Clinical Element Models (CEMs) have been adopted by the Office of the National Coordinator awarded Strategic Health IT Advanced Research Projects for normalization (SHARPn) project for normalizing patient data from the electronic health records (EHR). The objective of the present study is to describe our preliminary efforts toward harmonization of the SHARPn CEMs with CDISC (Clinical Data Interchange Standards Consortium) clinical study data standards. We were focused on three generic domains: demographics, lab tests, and medications. We performed a panel review on each data element extracted from the CDISC templates and SHARPn CEMs. We have identified a set of data elements that are common to the context of both clinical study and broad secondary use of EHR data and discussed outstanding harmonization issues. We consider that the outcomes would be useful for defining new requirements for the DCM modeling community and ultimately facilitating the semantic interoperability between systems for both clinical study and broad secondary use domains.

  18. Characterization of GaN layers by second harmonic generation and photoluminescence

    Science.gov (United States)

    Juodkazis, Saulius; Galeckas, Augustinas; Vaitkus, Juozas V.; Sakai, Shiro; Misawa, Hiroaki

    2001-03-01

    We have observed an apparent rotational anisotropy of the second harmonic generation (SHG) at signal at (lambda) = 405 nm back-reflected from the surface (0001) of 3 micrometers -thick GaN grown by metalorganic chemical vapor deposition (MOCVD). The focusing depth of 2 micrometers was aimed to probe the 10-15 nm-thick buffer layer where both cubic and hexagonal phases of GaN are coexisting. Typical angular dependency clearly indicated the presence of both isotropic and six-fold contributions. The isotropic I(2(omega ))(qq) component has a minor one-fold modulation due to a ca. 2 degree(s) disorientation of the top surface with respect to the hexagonal planes. We attribute the substantial isotropic component to the SHG yield from the bulk of GaN. The occurrence of six-fold I(2(omega )) (qq) anisotropy, however, indicates a complementary nonlinearities, most likely due to hexagonal phase, which is coexisting with the hexagonal one in the buffer layer region. In general, both surface and bulk nonlinearities are contributing to the reflected SH yield. The symmetry of surface can differ from that in the bulk, exhibiting a corresponding angular dependence of harmonic generation. SHG mapping of GaN (ooo1) surface was measured from the ablated pattern. Space-Time-Spectra resolved photoluminescence (PL) was used to characterize the InGaN layers and GaN/InGaN MQW laser structures. Two-photon absorption (TPA) excited mapping of the dislocation network in GaN layers is demonstrated.

  19. Evaluation of tag entanglement as a factor in harmonic radar studies of insect dispersal.

    Science.gov (United States)

    Boiteau, G; Vincent, C; Meloche, F; Leskey, T C; Colpitts, B G

    2011-02-01

    The observation of insects and other small organisms entangled in the habitat after the addition of vertical or trailing electronic tags to their body has generated concerns on the suitability of harmonic radars to track the dispersal of insects. This study compared the walking behavior of adult Colorado potato beetle (Leptinotarsa decemlineata (Say) Chrysomelidae), plum curculio (Conotrachelus nenuphar (Herbst) Curculionidae), and western corn rootworm (Diabrotica virgifera virgifera (LeConte) Chrysomelidae) with and without vertical and or trailing tags in field plots or arenas. The frequency of the larger Colorado potato beetles crossing bare ground or grassy plots was unaffected by the presence of an 8 cm trailing harmonic radar tag. However, plum curculios and western corn rootworms, were either unable to walk with a 4 cm trailing tag (plum curculio) or displayed a reduced ability to successfully cross a bare ground arena. Our results revealed the significant impact of vegetation on successful insect dispersal, whether tagged or not. The vertical movement of these insects on stems, stalks, and tubes was also unaffected by the presence of vertical tags. Trailing tags had a significant negative effect on the vertical movement of the western corn rootworm. Results show that harmonic radar technology is a suitable method for studying the walking paths of the three insects with appropriate tag type and size. The nuisance factor generated by appropriately sized tags was small relative to that of vegetation. © 2011 Entomological Society of America

  20. Noise Analysis of Second-Harmonic Generation in Undoped and MgO-Doped Periodically Poled Lithium Niobate

    OpenAIRE

    Yong Wang; Jorge Fonseca-Campos; Wan-guo Liang; Chang-Qing Xu; Ignacio Vargas-Baca

    2008-01-01

    Noise characteristics of second-harmonic generation (SHG) in periodically poled lithium niobate (PPLN) using the quasiphase matching (QPM) technique are analyzed experimentally. In the experiment, a0.78 μm second-harmonic (SH) wave was generated when a 1.56 μm fundamental wave passed through a PPLN crystal (bulk or waveguide). The time-domain and frequency-domain noise characteristics of the fundamental and SH waves were analyzed. By using the pump-probe method, the noise characteristics of S...

  1. Life cycle water use for electricity generation: a review and harmonization of literature estimates

    Science.gov (United States)

    Meldrum, J.; Nettles-Anderson, S.; Heath, G.; Macknick, J.

    2013-03-01

    This article provides consolidated estimates of water withdrawal and water consumption for the full life cycle of selected electricity generating technologies, which includes component manufacturing, fuel acquisition, processing, and transport, and power plant operation and decommissioning. Estimates were gathered through a broad search of publicly available sources, screened for quality and relevance, and harmonized for methodological differences. Published estimates vary substantially, due in part to differences in production pathways, in defined boundaries, and in performance parameters. Despite limitations to available data, we find that: water used for cooling of thermoelectric power plants dominates the life cycle water use in most cases; the coal, natural gas, and nuclear fuel cycles require substantial water per megawatt-hour in most cases; and, a substantial proportion of life cycle water use per megawatt-hour is required for the manufacturing and construction of concentrating solar, geothermal, photovoltaic, and wind power facilities. On the basis of the best available evidence for the evaluated technologies, total life cycle water use appears lowest for electricity generated by photovoltaics and wind, and highest for thermoelectric generation technologies. This report provides the foundation for conducting water use impact assessments of the power sector while also identifying gaps in data that could guide future research.

  2. Second-harmonic generation of ZnO nanoparticles synthesized by laser ablation of solids in liquids

    Science.gov (United States)

    Rocha-Mendoza, Israel; Camacho-López, Santiago; Luna-Palacios, Yryx Y.; Esqueda-Barrón, Yasmín; Camacho-López, Miguel A.; Camacho-López, Marco; Aguilar, Guillermo

    2018-02-01

    We report the synthesis of small zinc oxide nanoparticles (ZnO NPs) based colloidal suspensions and the study of second-harmonic generation from aggregated ZnO NPs deposited on glass substrates. The colloidal suspensions were obtained using the laser ablation of solids in liquids technique, ablating a Zn solid target immersed in acetone as the liquid medium, with ns-laser pulses (1064 nm) of a Nd-YAG laser. The per pulse laser fluence, the laser repetition rate frequency and the ablation time were kept constant. The absorption evolution of the obtained suspensions was optically characterized through absorption spectroscopy until stabilization. Raman spectroscopy, SEM and HRTEM were used to provide evidence of the ZnO NPs structure. HRTEM results showed that 5-8 nm spheroids ZnO NPs were obtained. Strong second-harmonic signal is obtained from random ZnO monocrystalline NPs and from aggregated ZnO NPs, suggesting that the high efficiency of the nonlinear process may not depend on the NPs size or aggregation state.

  3. Second harmonic generation spectroscopy in the Reststrahl band of SiC using an infrared free-electron laser

    Energy Technology Data Exchange (ETDEWEB)

    Paarmann, Alexander, E-mail: alexander.paarmann@fhi-berlin.mpg.de; Razdolski, Ilya; Melnikov, Alexey; Gewinner, Sandy; Schöllkopf, Wieland; Wolf, Martin [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin (Germany)

    2015-08-24

    The Reststrahl spectral region of silicon carbide has recently attracted much attention owing to its potential for mid-infrared nanophotonic applications based on surface phonon polaritons (SPhPs). Studies of optical phonon resonances responsible for surface polariton formation, however, have so far been limited to linear optics. In this Letter, we report the first nonlinear optical investigation of the Reststrahl region of SiC, employing an infrared free-electron laser to perform second harmonic generation (SHG) spectroscopy. We observe two distinct resonance features in the SHG spectra, one attributed to resonant enhancement of the nonlinear susceptibility χ{sup (2)} and the other due to a resonance in the Fresnel transmission. Our work clearly demonstrates high sensitivity of mid-infrared SHG to phonon-driven phenomena and opens a route to studying nonlinear effects in nanophotonic structures based on SPhPs.

  4. Probing and modeling of carrier motion in organic devices by electric-field-induced optical second-harmonic generation

    Science.gov (United States)

    Iwamoto, Mitsumasa; Manaka, Takaaki; Taguchi, Dai

    2014-10-01

    By probing dielectric polarization originating from dipoles and electrons in materials, we can study dynamical carrier behaviors in materials and also in devices. Maxwell displacement current (MDC) measurement allows us to directly probe orientational dipolar motion in monolayers, while electric-field-induced optical second-harmonic generation (EFISHG) measurement allows dynamical electron and hole transport in solids to be probed directly. By probing nonlinear polarization induced in solids by coupling with incident electromagnetic waves of laser beam and dc electric field that originate from moving carriers, long-range carrier motion is visualized. Experiments using a time-resolved EFISHG technique reveal carrier transfer in organic devices such as organic field-effect transistors, organic light-emitting diodes, organic memory devices, and organic solar cells, and thus enable us to model the carrier transport mechanism. We anticipate that this novel technique using EFISHG can be a powerful tool for studying carrier behaviors in organic devices as well as in organic materials.

  5. Electron-Nuclear Dynamics on Amplitude and Frequency Modulation of Molecular High-Order Harmonic Generation from H2+ and its Isotopes

    Science.gov (United States)

    Liu, Hang; Feng, Liqiang

    2017-09-01

    Electron-nuclear dynamics of molecular high-order harmonic generation from H2+ and its isotopes has been theoretically investigated beyond the Born-Oppenheimer approximations. The results show that (i) due to the different ionisation probabilities and the harmonic emission times, the intensities of the harmonics from H2+ and its isotopes are very sensitive to the initial vibrational state, the pulse duration, and the pulse intensity. (ii) Due to the nonadiabatic effects in molecular high-order harmonic generation, the red-shifts of the harmonics can be found in the lower pulse intensity. With the increase of the pulse intensity, the harmonics are from the red-shifts to the blue-shifts. Moreover, as the pulse duration increases, the blue-shifts of the harmonics can be enhanced. As the initial vibrational state increases, the red-shifts of the harmonics can be decreased, whereas the blue-shifts of the harmonics can be enhanced. However, the shifts of the harmonics are decreased as the nuclear mass increases. (iii) Due to the coupled electron-nuclear dynamics in molecules, the spatial symmetry of the system is broken. As a result, non-odd harmonics can be generated at the larger internuclear distance. With the increase of the initial vibrational state or the nuclear mass, the generation of the non-odd harmonics can be enhanced and reduced, respectively. As the pulse duration or the pulse intensity increase, the generation of the non-odd harmonics can be enhanced. However, the intensities of the non-odd harmonics are decreased when using the longer pulse duration with the much higher laser intensity.

  6. Effect of transition dipole phase on high-order-harmonic generation in solid materials

    Science.gov (United States)

    Jiang, Shicheng; Wei, Hui; Chen, Jigen; Yu, Chao; Lu, Ruifeng; Lin, C. D.

    2017-11-01

    High-order harmonic spectra from solid materials driven by single-color multicycle laser fields sometimes contain even harmonics. In this work we attribute the appearance of even harmonics to the nonzero transition dipole phase (TDP) when the solid system has broken symmetry. By calculating the harmonic efficiency from graphene and gapped graphene by using the semiconductor Bloch equations under the tight-binding approximation, we demonstrate the role of the TDP, which has been ignored for a long time. When the crystal has inversion symmetry, or reflection symmetry with the symmetry plane perpendicular to the laser polarization direction, the TDP can be neglected. Without such symmetry, however, the TDP will lead to the appearance of even harmonics. We further show that the TDP is sensitive to the crystal geometry. To extract the structure information from the harmonic spectra of a solid the TDP cannot be ignored.

  7. Intensity distributions and isolated attosecond pulse generation from molecular high-order harmonic generation in H2+ driven by nonhomogeneous field

    Science.gov (United States)

    Feng, Liqiang; Chu, Tianshu

    2017-10-01

    Intensity distributions and isolated attosecond pulse generation from the molecular high-order harmonic generation (MHHG) in H2+ and T2+ driven by the nonhomogeneous field have been theoretically investigated. (i) Generally speaking, the intensities of the harmonics driven by the homogeneous field can be enhanced as the initial vibrational state increases and much more intense harmonics can be obtained from the light nuclei. However, with the introduction of the nonhomogeneous effect, the enhanced ratios of the harmonic yields are decreased as the initial vibrational state increases. Moreover, the intensities of the harmonics from H2+ and T2+ are very sensitive to the nonhomogeneous effect of the laser field. (ii) The contributions of the MHHG from the two-H nuclei present the periodic variation as a function of the laser phase for the case of the symmetric nonhomogeneous field. However, for the case of the positive and the negative asymmetric nonhomogeneous fields, the left-H and the right-H play the dominating role in the MHHG, respectively. Moreover, as the angle between the laser polarization direction and the molecular axis increases, the intensity differences of the harmonics from the two-H nuclei are increased. (iii) By properly adding a half-cycle pulse into the positive asymmetric nonhomogeneous field, a supercontinuum with the bandwidth of 279 eV and an isolated 25 as pulse can be obtained.

  8. Generation of lower and upper bands of electrostatic electron cyclotron harmonic waves in the Van Allen radiation belts

    Science.gov (United States)

    Zhou, Qinghua; Xiao, Fuliang; Yang, Chang; Liu, Si; He, Yihua; Baker, D. N.; Spence, H. E.; Reeves, G. D.; Funsten, H. O.

    2017-06-01

    Electrostatic electron cyclotron harmonic (ECH) waves generated by the electron loss cone distribution can produce efficient scattering loss of plasma sheet electrons, which has a significant effect on the dynamics in the outer magnetosphere. Here we report two ECH emission events around the same location L≈ 5.7-5.8, MLT ≈ 12 from Van Allen Probes on 11 February (event A) and 9 January 2014 (event B), respectively. The spectrum of ECH waves was centered at the lower half of the harmonic bands during event A, but the upper half during event B. The observed electron phase space density in both events is fitted by the subtracted bi-Maxwellian distribution, and the fitting functions are used to evaluate the local growth rates of ECH waves based on a linear theory for homogeneous plasmas. ECH waves are excited by the loss cone instability of 50 eV-1 keV electrons in the lower half of harmonic bands in the low-density plasmasphere in event A, and 1-10 keV electrons in the upper half of harmonic bands in a relatively high-density region in event B. The current results successfully explain observations and provide a first direct evidence on how ECH waves are generated in the lower and upper half of harmonic frequency bands.

  9. Electrode surface rf harmonics generated by the nonlinear sheath in a coaxial capacitive rf discharge

    Energy Technology Data Exchange (ETDEWEB)

    Savas, S.E. (Applied Materials, Santa Clara, CA (USA))

    1989-07-01

    rf harmonics of the 13.56 MHz excitation signal have been measured on the electrode surface in a large coaxial capacitive discharge. These are seen to have from 10% of the fundamental amplitude for the second harmonic to between 1% and 4% for the third and fourth harmonics. There is evidence that these modes propragate as TEM surface waves (Gould-Trivelpiece modes) along the length of the electrode. The Telegrapher's equations can be written for the system with non-constant shunt capacitance and admittance. The resulting nonlinear equation for the sheath voltage is solved for the harmonics to yield approximate agreement with their observed magnitudes.

  10. Deterministic and Stochastic Study of Wind Farm Harmonic Currents

    DEFF Research Database (Denmark)

    Sainz, Luis; Mesas, Juan Jose; Teodorescu, Remus

    2010-01-01

    Wind farm harmonic emissions are a well-known power quality problem, but little data based on actual wind farm measurements are available in literature. In this paper, harmonic emissions of an 18 MW wind farm are investigated using extensive measurements, and the deterministic and stochastic char...

  11. Analysis of third harmonic generation and four wave mixing in gold nanostructures by nonlinear finite difference time domain.

    Science.gov (United States)

    Sasanpour, Pezhman; Shahmansouri, Afsaneh; Rashidian, Bizhan

    2010-11-01

    Third order nonlinear effects and its enhancement in gold nanostructures has been numerically studied. Analysis method is based on computationally solving nonlinear Maxwell's equations, considering dispersion behavior of permittivity described by Drude model and third order nonlinear susceptibility. Simulation is done by method of nonlinear finite difference time domain method, in which nonlinear equations of electric field are solved by Newton-Raphshon method. As the main outcomes of third order nonlinear susceptibility, four wave mixing and third harmonic generation terms are produced around gold nanostructures. Results of analysis on different geometries and structures show that third order nonlinearity products are more enhanced in places where electric field enhancement is occurred due to surface plasmons. Results indicates that enhancement of nonlinearities is strongly occurred in structures whose interface is dielectric. According to analysis results, nonlinear effects are highly concentrated in the vicinity of nanostructures. Hence this approach can be used in applications where localized ultraviolet light is required.

  12. In vivo visualization of dermal collagen fiber in skin burn by collagen-sensitive second-harmonic-generation microscopy

    Science.gov (United States)

    Tanaka, Ryosuke; Fukushima, Shu-ichiro; Sasaki, Kunihiko; Tanaka, Yuji; Murota, Hiroyuki; Matsumoto, Takeshi; Araki, Tsutomu; Yasui, Takeshi

    2013-06-01

    Optical assessment of skin burns is possible with second-harmonic-generation (SHG) microscopy due to its high sensitivity to thermal denaturation of collagen molecules. In contrast to previous studies that were performed using excised tissue specimens ex vivo, in vivo observation of dermal collagen fibers in living rat burn models with SHG microscopy is demonstrated. Changes in signal vanishing patterns in the SHG images are confirmed to be dependent on the burn degree. Comparison of the SHG images with Masson's trichrome-stained images indicated that the observed patterns were caused by the coexistence of molten and fibrous structures of dermal collagen fibers. Furthermore, a quantitative parameter for burn assessment based on the depth profile of the mean SHG intensity across the entire SHG image is proposed. These results and discussions imply a potential of SHG microscopy as a minimally invasive, highly quantitative tool for skin burn assessment.

  13. Efficiency of different methods of extra-cavity second harmonic generation of continuous wave single-frequency radiation.

    Science.gov (United States)

    Khripunov, Sergey; Kobtsev, Sergey; Radnatarov, Daba

    2016-01-20

    This work presents for the first time to the best of our knowledge a comparative efficiency analysis among various techniques of extra-cavity second harmonic generation (SHG) of continuous-wave single-frequency radiation in nonperiodically poled nonlinear crystals within a broad range of power levels. Efficiency of nonlinear radiation transformation at powers from 1 W to 10 kW was studied in three different configurations: with an external power-enhancement cavity and without the cavity in the case of single and double radiation pass through a nonlinear crystal. It is demonstrated that at power levels exceeding 1 kW, the efficiencies of methods with and without external power-enhancement cavities become comparable, whereas at even higher powers, SHG by a single or double pass through a nonlinear crystal becomes preferable because of the relatively high efficiency of nonlinear transformation and fairly simple implementation.

  14. Analysis of the second harmonic generation signal from a liquid/air and liquid/liquid interface

    Science.gov (United States)

    Pham, Thanh Tung; Jonchère, Alban; Dufrêche, Jean-François; Brevet, Pierre-François; Diat, Olivier

    2017-04-01

    Three different liquid interfaces, water/air, thiophene/air, and water/thiophene, were probed using the second harmonic generation (SHG) technique. Thiophene and water have been chosen because the hyperpolarizability of these molecules has already been measured or calculated and the different values can be found in literature. We have studied the microscopic structure of these interfaces by comparing the components of the second order susceptibility tensor determined from the SHG polarization curve analysis with those determined via a molecular dynamics (MD) simulation of these interfaces. We have indeed computed the structure and orientation of water and thiophene molecules at the liquid/air and liquid/liquid (L/L) interfaces as a function of the distance from the interface. The integrated susceptibility values calculated by MD simulations agree well with SHG results and validate the choice of force fields that should permit to quantify more complex L/L interfaces.

  15. Probing the longitudinal electric field of Bessel beams using second-harmonic generation from nano-objects

    Science.gov (United States)

    Turquet, Léo; Kakko, Joona-Pekko; Karvonen, Lasse; Jiang, Hua; Kauppinen, Esko; Lipsanen, Harri; Kauranen, Martti; Bautista, Godofredo

    2017-08-01

    Non-diffractive Bessel beams are receiving significant interest in optical microscopy due to their remarkably large depth of field. For example, studies have shown the superiority of Bessel beams over Gaussian beams for volumetric imaging of three-dimensionally thick or extended samples. However, the vectorial aspects of the focal fields of Bessel beams are generally obscured when traditional methods are used to characterize their three-dimensional point-spread function in space, which contains contributions from all optical field components. Here, we show experimentally the three-dimensional spatial distribution and enhanced depth of field of the longitudinal electric field components of a focused linearly-polarized Bessel beam. This is done through second-harmonic generation from well-defined vertically-aligned gallium-arsenide nanowires, whose second-order response is primarily driven by the longitudinal fields at the beam focus.

  16. Second harmonic generation in NLO polymers excited by Surface Plasmon enhanced electric field induced by femtosecond optical pulses

    Directory of Open Access Journals (Sweden)

    Kawata Y.

    2013-03-01

    Full Text Available We will report second harmonic generation (SHG in nonlinear optical (NLO polymers excited by surface plasmon enhanced optical fields. The surface plasmon (SP polariton was excited in an attenuated total reflection geometry having the Kretchmann configuration. The NLO polymers, consisting of Disperse Red1 as guest chromophores and poly (methyl methacrylate as host materials, were coated upon the Ag layers. Our experimental results indicated that the SHG signal intensity from the polymer coated Ag films was more than 10 times higher than that from the non-coated Ag films. The SHG autocorrelation traces excited by SP-enhanced fields were also studied and the correlation time was shorter than 150 fs, the temporal resolutions of the present spectrometer.

  17. SEPARATION OF INTERFACE AND BULK CONTRIBUTIONS IN 2ND-HARMONIC GENERATION FROM MAGNETIC AND NONMAGNETIC MULTILAYERS

    NARCIS (Netherlands)

    KOOPMANS, B; JANNER, AM; WIERENGA, HA; RASING, T; SAWATZKY, GA; VANDERWOUDE, F

    We discuss the separation problem of bulk vs interface contributions in optical Second-Harmonic Generation (SHG). A new method is presented, which - in special cases - provides a full separation of all interface and bulk tenser components. The method is based on measurements in a thin-film geometry,

  18. Plasmonic enhancement of second harmonic generation from nonlinear RbTiOPO4 crystals by aggregates of silver nanostructures

    DEFF Research Database (Denmark)

    Sánchez-García, Laura; Tserkezis, Christos; Ramírez, Mariola O

    2016-01-01

    We demonstrate a 60–fold enhancement of the second harmonic generation (SHG) response at the nanoscale in a hybrid metal-dielectric system. By using complex silver nanostructures photochemically deposited on the polar surface of a ferroelectric crystal, we tune the plasmonic resonances from the v...

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

    Science.gov (United States)

    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.

  20. Fiber-based 1150-nm femtosecond laser source for the minimally invasive harmonic generation microscopy

    Science.gov (United States)

    Huang, Jing-Yu; Guo, Lun-Zhang; Wang, Jing-Zun; Li, Tse-Chung; Lee, Hsin-Jung; Chiu, Po-Kai; Peng, Lung-Han; Liu, Tzu-Ming

    2017-03-01

    Harmonic generation microscopy (HGM) has become one unique tool of optical virtual biopsy for the diagnosis of cancer and the in vivo cytometry of leukocytes. Without labeling, HGM can reveal the submicron features of tissues and cells in vivo. For deep imaging depth and minimal invasiveness, people commonly adopt 1100- to 1300-nm femtosecond laser sources. However, those lasers are typically based on bulky oscillators whose performances are sensitive to environmental conditions. We demonstrate a fiber-based 1150-nm femtosecond laser source, with 6.5-nJ pulse energy, 86-fs pulse width, and 11.25-MHz pulse repetition rate. It was obtained by a bismuth borate or magnesium-doped periodically poled lithium niobate (MgO:PPLN) mediated frequency doubling of the 2300-nm solitons, generated from an excitation of 1550-nm femtosecond pulses on a large mode area photonic crystal fiber. Combined with a home-built laser scanned microscope and a tailor-made frame grabber, we achieve a pulse-per-pixel HGM imaging in vivo at a 30-Hz frame rate. This integrated solution has the potential to be developed as a stable HGM system for routine clinical use.

  1. XUV-initiated high harmonic generation: driving inner valence electrons using below-threshold-energy XUV light

    CERN Document Server

    Brown, A C

    2016-01-01

    We propose a novel scheme for resolving the contribution of inner- and outer-valence electrons in XUV-initiated high-harmonic generation in neon. By probing the atom with a low energy (below the 2s ionisation threshold) ultrashort XUV pulse, the 2p electron is steered away from the core, while the 2s electron is enabled to describe recollision trajectories. By selectively suppressing the 2p recollision trajectories we can resolve the contribution of the 2s electron to the high-harmonic spectrum. We apply the classical trajectory model to account for the contribution of the 2s electron, which allows for an intuitive understanding of the process.

  2. Time-resolved photoelectron spectroscopy of polyatomic molecules using 42-nm vacuum ultraviolet laser based on high harmonics generation

    Science.gov (United States)

    Nishitani, Junichi; West, Christopher W.; Higashimura, Chika; Suzuki, Toshinori

    2017-09-01

    Time-resolved photoelectron spectroscopy (TRPES) of gaseous polyatomic molecules using 266-nm (4.7 eV) pump and 42-nm (29.5 eV) probe pulses is presented. A 1-kHz Ti:sapphire laser with a 35 fs pulse duration is employed to generate high harmonics in Kr gas, and the 19th harmonic (42-nm) was selected using two SiC/Mg mirrors. Clear observation of the ultrafast electronic dephasing in pyrazine and photoisomerization of 1,3-cyclohexadiene demonstrates the feasibility of TRPES with the UV pump and VUV probe pulses under weak excitation conditions in the perturbation regime.

  3. Measuring the temporal coherence of a high harmonic generation setup employing a Fourier transform spectrometer for the VUV/XUV

    Energy Technology Data Exchange (ETDEWEB)

    Terschlüsen, J.A., E-mail: Joachim.Terschluesen@physics.uu.se; Agåker, M.; Svanqvist, M.; Plogmaker, S.; Nordgren, J.; Rubensson, J.-E.; Siegbahn, H.; Söderström, J.

    2014-12-21

    In this experiment we used an 800 nm laser to generate high-order harmonics in a gas cell filled with Argon. Of those photons, a harmonic with 42 eV was selected by using a time-preserving grating monochromator. Employing a modified Mach–Zehnder type Fourier transform spectrometer for the VUV/XUV it was possible to measure the temporal coherence of the selected photons to about 6 fs. We demonstrated that not only could this kind of measurement be performed with a Fourier transform spectrometer, but also with some spatial resolution without modifying the XUV source or the spectrometer.

  4. Characterization method of unusual second-order-harmonic generation based on vortex transformation

    Science.gov (United States)

    Zhang, Chaojin; Wu, Erheng; Gu, Mingliang; Hu, Zhengfeng; Liu, Chengpu

    2017-09-01

    When a few-cycle laser beam nonresonantly propagates through an inversion-symmetric medium, beyond the usual odd-order harmonics in the transmission spectra, a well-defined spectral peak at twice the incident laser central frequency is disclosed [T. Tritschler et al., Phys. Rev. Lett. 90, 217404 (2003), 10.1103/PhysRevLett.90.217404]. Beyond the characterization method via the rf measurement of its carrier-envelope phase dependence, here a more direct mode of characterization is proposed by means of vortex transformation where a few-cycle vortex laser is adopted instead: One can easily clarify its origin as an usual third-order harmonic that appears to be a second-order harmonic, based on the criteria that the topological charge number of harmonics is directly proportional to its harmonic order.

  5. Efficient single-pass third-harmonic generation from 1560 nm to 520 nm for pumping doubly-resonant OPO

    Science.gov (United States)

    Zhang, Kong; Wang, Junmin

    2017-08-01

    A ~545 mW single-frequency tunable 520 nm green laser has been demonstrated using a periodically-poled potassium titanyl phosphate (PPKTP) bulk crystal based on single-pass third-harmonic generation (THG) of a 1560 nm laser via single-pass second-harmonic generation (SHG) followed by single-pass sum-frequency generation (SFG). In single-pass SHG, two cascaded periodically-poled magnesium-oxide-doped lithium niobate (PPMgO:LN) crystals were used, and ~3.5 W 780.25 nm doubled laser output is produced, corresponding to maximum doubling efficiency of 26.8%. The system can provide a pump source (520 nm) for an optical parametric oscillator for two-color entangled continuous-variable optical field generation at 1560 and 780 nm and two-color local oscillators for homodyne detection.

  6. In-line production of a bi-circular field for generation of helically polarized high-order harmonics

    Energy Technology Data Exchange (ETDEWEB)

    Kfir, Ofer, E-mail: ofertx@technion.ac.il, E-mail: oren@si.technion.ac.il; Bordo, Eliyahu; Ilan Haham, Gil; Lahav, Oren; Cohen, Oren, E-mail: ofertx@technion.ac.il, E-mail: oren@si.technion.ac.il [Solid State Institute and Physics Department, Technion, Haifa 32000 (Israel); Fleischer, Avner [Solid State Institute and Physics Department, Technion, Haifa 32000 (Israel); Department of Physics and Optical Engineering, Ort Braude College, Karmiel 21982 (Israel)

    2016-05-23

    The recent demonstration of bright circularly polarized high-order harmonics of a bi-circular pump field gave rise to new opportunities in ultrafast chiral science. In previous works, the required nontrivial bi-circular pump field was produced using a relatively complicated and sensitive Mach-Zehnder-like interferometer. We propose a compact and stable in-line apparatus for converting a quasi-monochromatic linearly polarized ultrashort driving laser field into a bi-circular field and employ it for generation of helically polarized high-harmonics. Furthermore, utilizing the apparatus for a spectroscopic spin-mixing measurement, we identify the photon spins of the bi-circular weak component field that are annihilated during the high harmonics process.

  7. Simultaneous generation of ions and high-order harmonics from thin conjugated polymer foil irradiated with ultrahigh contrast laser

    Energy Technology Data Exchange (ETDEWEB)

    Choi, I. W.; Kim, I J.; Pae, K. H.; Nam, K. H.; Lee, C.-L.; Yun, H.; Kim, H. T.; Lee, S. K.; Yu, T. J.; Sung, J. H.; Lee, J. [Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Pirozhkov, A. S.; Ogura, K.; Orimo, S.; Daido, H. [Quantum Beam Science Directorate, Japan Atomic Energy Agency, Kizugawa, Kyoto 619-0215 (Japan)

    2011-10-31

    We report the manufacturing of an (ultra-)thin foil target made of conjugated polymer, poly(9,9'-dioctylfluorene-co-benzothiadiazole) (F8BT), and the simultaneous observation of laser-accelerated ions and second harmonic radiation, when irradiated with ultrahigh-contrast laser pulse at a maximum intensity of 4 x 10{sup 19 }W/cm{sup 2}. Maximum proton energy of 8 MeV is achieved along the target normal direction. Strong second harmonic with over 6% energy ratio compared to fundamental is emitted along the specular direction. Two-dimensional particle-in-cell simulations confirm the simultaneous generation of protons and high-order harmonics, which demonstrates the feasibility of applications requiring particle and radiation sources at once, effectively using the same laser and target.

  8. Analytic model of bunched beams for harmonic generation in the low-gain free electron laser regime

    Directory of Open Access Journals (Sweden)

    G. Penn

    2006-06-01

    Full Text Available One scheme for harmonic generation employs free electron lasers (FELs with two undulators: the first uses a seed laser to modulate the energy of the electron beam; following a dispersive element which acts to bunch the beam, the second undulator radiates at a higher harmonic. These processes are currently evaluated using extensive calculations or simulation codes which can be slow to evaluate and difficult to set up. We describe a simple algorithm to predict the output of a harmonic generation beam line in the low-gain FEL regime, based on trial functions for the output radiation. Full three-dimensional effects are included. This method has been implemented as a Mathematica® package, named CAMPANILE, which runs rapidly and can be generalized to include effects such as asymmetric beams and misalignments. This method is compared with simulation results using the FEL code GENESIS, both for single stages of harmonic generation and for the LUX project, a design concept for an ultrafast x-ray facility, where multiple stages upshift the input laser frequency by factors of up to 200.

  9. Modelling third harmonic ion cyclotron acceleration of deuterium beams for JET fusion product studies experiments

    DEFF Research Database (Denmark)

    Schneider, M.; Johnson, T.; Dumont, R.

    2016-01-01

    Recent JET experiments have been dedicated to the studies of fusion reactions between deuterium (D) and Helium-3 (3He) ions using neutral beam injection (NBI) in synergy with third harmonic ion cyclotron radio-frequency heating (ICRH) of the beam. This scenario generates a fast ion deuterium tail...... ion diagnostics, showing an overall good agreement. Finally, a sawtooth activity for these experiments has been observed and interpreted using SPOT/RFOF simulations in the framework of Porcelli’s theoretical model, where NBI+ICRH accelerated ions are found to have a strong stabilizing effect, leading...

  10. Automated biphasic morphological assessment of hepatitis B-related liver fibrosis using second harmonic generation microscopy

    Science.gov (United States)

    Wang, Tong-Hong; Chen, Tse-Ching; Teng, Xiao; Liang, Kung-Hao; Yeh, Chau-Ting

    2015-08-01

    Liver fibrosis assessment by biopsy and conventional staining scores is based on histopathological criteria. Variations in sample preparation and the use of semi-quantitative histopathological methods commonly result in discrepancies between medical centers. Thus, minor changes in liver fibrosis might be overlooked in multi-center clinical trials, leading to statistically non-significant data. Here, we developed a computer-assisted, fully automated, staining-free method for hepatitis B-related liver fibrosis assessment. In total, 175 liver biopsies were divided into training (n = 105) and verification (n = 70) cohorts. Collagen was observed using second harmonic generation (SHG) microscopy without prior staining, and hepatocyte morphology was recorded using two-photon excitation fluorescence (TPEF) microscopy. The training cohort was utilized to establish a quantification algorithm. Eleven of 19 computer-recognizable SHG/TPEF microscopic morphological features were significantly correlated with the ISHAK fibrosis stages (P 0.82 for liver cirrhosis detection. Since no subjective gradings are needed, interobserver discrepancies could be avoided using this fully automated method.

  11. Second Harmonic Generation Reveals Subtle Fibrosis Differences in Adult and Pediatric Nonalcoholic Fatty Liver Disease.

    Science.gov (United States)

    Liu, Feng; Zhao, Jing-Min; Rao, Hui-Ying; Yu, Wei-Miao; Zhang, Wei; Theise, Neil D; Wee, Aileen; Wei, Lai

    2017-11-20

    Investigate subtle fibrosis similarities and differences in adult and pediatric nonalcoholic fatty liver disease (NAFLD) using second harmonic generation (SHG). SHG/two-photon excitation fluorescence imaging quantified 100 collagen parameters and determined qFibrosis values by using the nonalcoholic steatohepatitis (NASH) Clinical Research Network (CRN) scoring system in 62 adult and 36 pediatric NAFLD liver specimens. Six distinct parameters identified differences among the NASH CRN stages with high accuracy (area under the curve, 0835-0.982 vs 0.885-0.981, adult and pediatric). All portal region parameters showed similar changes across early stages 0, 1C, and 2, in both groups. Parameter values decreased in adults with progression from stage 1A/B to 2 in the central vein region. In children, aggregated collagen parameters decreased, but nearly all distributed collagen parameters increased from stage 1A/B to 2. SHG analysis accurately reproduces NASH CRN staging in NAFLD, as well as reveals differences and similarities between adult and pediatric collagen deposition not captured by currently available quantitative methods.

  12. Second-harmonic generation scattering directionality predicts tumor cell motility in collagen gels

    Science.gov (United States)

    Burke, Kathleen A.; Dawes, Ryan P.; Cheema, Mehar K.; Van Hove, Amy; Benoit, Danielle S. W.; Perry, Seth W.; Brown, Edward

    2015-01-01

    Abstract. Second-harmonic generation (SHG) allows for the analysis of tumor collagen structural changes throughout metastatic progression. SHG directionality, measured through the ratio of the forward-propagating to backward-propagating signal (F/B ratio), is affected by collagen fibril diameter, spacing, and disorder of fibril packing within a fiber. As tumors progress, these parameters evolve, producing concurrent changes in F/B. It has been recently shown that the F/B of highly metastatic invasive ductal carcinoma (IDC) breast tumors is significantly different from less metastatic tumors. This suggests a possible relationship between the microstructure of collagen, as measured by the F/B, and the ability of tumor cells to locomote through that collagen. Utilizing in vitro collagen gels of different F/B ratios, we explored the relationship between collagen microstructure and motility of tumor cells in a “clean” environment, free of the myriad cells, and signals found in in vivo. We found a significant relationship between F/B and the total distance traveled by the tumor cell, as well as both the average and maximum velocities of the cells. Consequently, one possible mechanism underlying the observed relationship between tumor F/B and metastatic output in IDC patient samples is a direct influence of collagen structure on tumor cell motility. PMID:25625899

  13. Synchronous-digitization for Video Rate Polarization Modulated Beam Scanning Second Harmonic Generation Microscopy.

    Science.gov (United States)

    Sullivan, Shane Z; DeWalt, Emma L; Schmitt, Paul D; Muir, Ryan M; Simpson, Garth J

    2015-03-09

    Fast beam-scanning non-linear optical microscopy, coupled with fast (8 MHz) polarization modulation and analytical modeling have enabled simultaneous nonlinear optical Stokes ellipsometry (NOSE) and linear Stokes ellipsometry imaging at video rate (15 Hz). NOSE enables recovery of the complex-valued Jones tensor that describes the polarization-dependent observables, in contrast to polarimetry, in which the polarization stated of the exciting beam is recorded. Each data acquisition consists of 30 images (10 for each detector, with three detectors operating in parallel), each of which corresponds to polarization-dependent results. Processing of this image set by linear fitting contracts down each set of 10 images to a set of 5 parameters for each detector in second harmonic generation (SHG) and three parameters for the transmittance of the fundamental laser beam. Using these parameters, it is possible to recover the Jones tensor elements of the sample at video rate. Video rate imaging is enabled by performing synchronous digitization (SD), in which a PCIe digital oscilloscope card is synchronized to the laser (the laser is the master clock.) Fast polarization modulation was achieved by modulating an electro-optic modulator synchronously with the laser and digitizer, with a simple sine-wave at 1/10th the period of the laser, producing a repeating pattern of 10 polarization states. This approach was validated using Z-cut quartz, and NOSE microscopy was performed for micro-crystals of naproxen.

  14. Second harmonic generation for collagen I characterization in rectal cancer patients with and without preoperative radiotherapy

    Science.gov (United States)

    Blockhuys, Stéphanie; Agarwal, Nisha Rani; Hildesjö, Camilla; Jarlsfelt, Ingvar; Wittung-Stafshede, Pernilla; Sun, Xiao-Feng

    2017-10-01

    Rectal cancer is treated with preoperative radiotherapy (RT) to downstage the tumor, reduce local recurrence, and improve patient survival. Still, the treatment outcome varies significantly and new biomarkers are desired. Collagen I (Col-I) is a potential biomarker, which can be visualized label-free by second harmonic generation (SHG). Here, we used SHG to identify Col-I changes induced by RT in surgical tissue, with the aim to evaluate the clinical significance of RT-induced Col-I changes. First, we established a procedure for quantitative evaluation of Col-I by SHG in CDX2-stained tissue sections. Next, we evaluated Col-I properties in material from 31 non-RT and 29 RT rectal cancer patients. We discovered that the Col-I intensity and anisotropy were higher in the tumor invasive margin than in the inner tumor and normal mucosa, and RT increased and decreased the intensity in inner tumor and normal mucosa, respectively. Furthermore, higher Col-I intensity in the inner tumor was related to increased distant recurrence in the non-RT group but to longer survival in the RT group. In conclusion, we present a new application of SHG for quantitative analysis of Col-I in surgical material, and the first data suggest Col-I intensity as a putative prognostic biomarker in rectal cancer.

  15. Quasiclassical Theory on Third-Harmonic Generation in Conventional Superconductors with Paramagnetic Impurities

    Science.gov (United States)

    Jujo, Takanobu

    2018-02-01

    We investigate the third-harmonic generation (THG) of s-wave superconductors under microwave pulse irradiation. We consider the effect of paramagnetic impurities on the THG intensity of dirty superconductors. The nonlinear response function is calculated using the method of the quasiclassical Green function. It is shown that the amplitude mode is included as the vertex correction and makes a predominant contribution to the THG intensity. When the effect of paramagnetic impurities is weak, the THG intensity shows a peak at the temperature at which the superconducting gap is about the same as the frequency of the incident pulse, similarly to in experiments. As the effect of paramagnetic impurities is strengthened, the peak of the THG intensity disappears. This indicates that time-reversal symmetry breaking due to paramagnetic impurities eliminates the well-defined amplitude mode. The result of our calculation shows that the existence of the amplitude mode can be confirmed through the THG intensity. The result of a semiquantitative calculation is in good agreement with the experimental result, and it also shows that the diamagnetic term is negligible.

  16. Second-harmonic generation scattering directionality predicts tumor cell motility in collagen gels

    Science.gov (United States)

    Burke, Kathleen A.; Dawes, Ryan P.; Cheema, Mehar K.; Van Hove, Amy; Benoit, Danielle S. W.; Perry, Seth W.; Brown, Edward

    2015-05-01

    Second-harmonic generation (SHG) allows for the analysis of tumor collagen structural changes throughout metastatic progression. SHG directionality, measured through the ratio of the forward-propagating to backward-propagating signal (F/B ratio), is affected by collagen fibril diameter, spacing, and disorder of fibril packing within a fiber. As tumors progress, these parameters evolve, producing concurrent changes in F/B. It has been recently shown that the F/B of highly metastatic invasive ductal carcinoma (IDC) breast tumors is significantly different from less metastatic tumors. This suggests a possible relationship between the microstructure of collagen, as measured by the F/B, and the ability of tumor cells to locomote through that collagen. Utilizing in vitro collagen gels of different F/B ratios, we explored the relationship between collagen microstructure and motility of tumor cells in a "clean" environment, free of the myriad cells, and signals found in in vivo. We found a significant relationship between F/B and the total distance traveled by the tumor cell, as well as both the average and maximum velocities of the cells. Consequently, one possible mechanism underlying the observed relationship between tumor F/B and metastatic output in IDC patient samples is a direct influence of collagen structure on tumor cell motility.

  17. Optical second-harmonic generation measurements of porous low-k dielectric materials

    Science.gov (United States)

    Atkin, Joanna; Shaw, Thomas; Laibowitz, Robert; Heinz, Tony

    2009-03-01

    Low-k dielectric materials based on porous carbon-doped oxides, with relative dielectric constants as low as 2.1, are widely used as thin insulating films in the microelectronics industry. Knowledge of these materials' basic electronic properties, such as energy gaps, barrier heights, and trap states, is essential for modeling their electrical leakage and stability characteristics. We use femtosecond laser pulses to probe the dynamics of charge-carrier transfer processes across Si/LKD interfacial barriers by optical second harmonic generation (SHG). Larger electric fields from multiphoton injection can be developed in Si/LKD systems compared to Si/SiO2, indicating a significantly higher density of traps in the LKD. This is consistent with previously reported measurements of trap density by photoinjection techniques^*. We will also discuss results on the dynamics of discharging and on the dependence of charging phenomena on layer thickness. ^*J. M. Atkin, D. Song, T. M. Shaw, E. Cartier, R. B. Laibowitz, and T. F. Heinz, J. Appl. Phys. 103, 094104 (2008).

  18. Quantitative comparison of 3D third harmonic generation and fluorescence microscopy images.

    Science.gov (United States)

    Zhang, Zhiqing; Kuzmin, Nikolay V; Groot, Marie Louise; de Munck, Jan C

    2018-01-01

    Third harmonic generation (THG) microscopy is a label-free imaging technique that shows great potential for rapid pathology of brain tissue during brain tumor surgery. However, the interpretation of THG brain images should be quantitatively linked to images of more standard imaging techniques, which so far has been done qualitatively only. We establish here such a quantitative link between THG images of mouse brain tissue and all-nuclei-highlighted fluorescence images, acquired simultaneously from the same tissue area. For quantitative comparison of a substantial pair of images, we present here a segmentation workflow that is applicable for both THG and fluorescence images, with a precision of 91.3 % and 95.8 % achieved respectively. We find that the correspondence between the main features of the two imaging modalities amounts to 88.9 %, providing quantitative evidence of the interpretation of dark holes as brain cells. Moreover, 80 % bright objects in THG images overlap with nuclei highlighted in the fluorescence images, and they are 2 times smaller than the dark holes, showing that cells of different morphologies can be recognized in THG images. We expect that the described quantitative comparison is applicable to other types of brain tissue and with more specific staining experiments for cell type identification. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Characterization of wavefront errors in mouse cranial bone using second-harmonic generation

    Science.gov (United States)

    Tehrani, Kayvan Forouhesh; Kner, Peter; Mortensen, Luke J.

    2017-03-01

    Optical aberrations significantly affect the resolution and signal-to-noise ratio of deep tissue microscopy. As multiphoton microscopy is applied deeper into tissue, the loss of resolution and signal due to propagation of light in a medium with heterogeneous refractive index becomes more serious. Efforts in imaging through the intact skull of mice cannot typically reach past the bone marrow (˜150 μm of depth) and have limited resolution and penetration depth. Mechanical bone thinning or optical ablation of bone enables deeper imaging, but these methods are highly invasive and may impact tissue biology. Adaptive optics is a promising noninvasive alternative for restoring optical resolution. We characterize the aberrations present in bone using second-harmonic generation imaging of collagen. We simulate light propagation through highly scattering bone and evaluate the effect of aberrations on the point spread function. We then calculate the wavefront and expand it in Zernike orthogonal polynomials to determine the strength of different optical aberrations. We further compare the corrected wavefront and the residual wavefront error, and suggest a correction element with high number of elements or multiconjugate wavefront correction for this highly scattering environment.

  20. Synchronous-digitization for video rate polarization modulated beam scanning second harmonic generation microscopy

    Science.gov (United States)

    Sullivan, Shane Z.; DeWalt, Emma L.; Schmitt, Paul D.; Muir, Ryan D.; Simpson, Garth J.

    2015-03-01

    Fast beam-scanning non-linear optical microscopy, coupled with fast (8 MHz) polarization modulation and analytical modeling have enabled simultaneous nonlinear optical Stokes ellipsometry (NOSE) and linear Stokes ellipsometry imaging at video rate (15 Hz). NOSE enables recovery of the complex-valued Jones tensor that describes the polarization-dependent observables, in contrast to polarimetry, in which the polarization stated of the exciting beam is recorded. Each data acquisition consists of 30 images (10 for each detector, with three detectors operating in parallel), each of which corresponds to polarization-dependent results. Processing of this image set by linear fitting contracts down each set of 10 images to a set of 5 parameters for each detector in second harmonic generation (SHG) and three parameters for the transmittance of the fundamental laser beam. Using these parameters, it is possible to recover the Jones tensor elements of the sample at video rate. Video rate imaging is enabled by performing synchronous digitization (SD), in which a PCIe digital oscilloscope card is synchronized to the laser (the laser is the master clock.) Fast polarization modulation was achieved by modulating an electro-optic modulator synchronously with the laser and digitizer, with a simple sine-wave at 1/10th the period of the laser, producing a repeating pattern of 10 polarization states. This approach was validated using Z-cut quartz, and NOSE microscopy was performed for micro-crystals of naproxen.

  1. Data Acquisition in a High Harmonic Generation Lab and at LCLS

    Energy Technology Data Exchange (ETDEWEB)

    Hirokawa, Takako; /U. Colorado, Boulder /SLAC

    2011-06-22

    In this paper, we examine data acquisition in a high harmonic generation (HHG) lab and preliminary data analysis with the Cyclohexadiene Collaboration at the Linac Coherent Lightsource (LCLS) at SLAC National Accelerator Laboratory. HHG experiments have a large number of parameters that need to be monitored constantly. In particular, the pressure of the target is critical to HHG yield. However, this pressure can fluctuate wildly and without a tool to monitor it, it is difficult to analyze the correlation between HHG yield and the pressure. I used the Arduino microcontroller board and created a complementary MATLAB graphical user interface (GUI), thereby enhancing the ease with which users can acquire time-stamped parameter data. Using the Arduino, it is much easier to match the pressure to the corresponding HHG yield. Collecting data by using the Arduino and the GUI is flexible, user-friendly, and cost-effective. In the future, we hope to be able to control and monitor parts of the lab with the Arduino alone. While more parameter information is needed in the HHG lab, we needed to reduce the amount of data during the cyclohexadiene collaboration. This was achieved by sorting the data into bins and filtering out unnecessary details. This method was highly effective in that it minimized the amount of data without losing any valuable information. This effective preliminary data analysis technique will continue to be used to decrease the size of the collected data.

  2. Selectively Plasmon-Enhanced Second-Harmonic Generation from Monolayer Tungsten Diselenide on Flexible Substrates

    KAUST Repository

    Wang, Zhuo

    2018-01-04

    Monolayer two-dimensional transition metal dichalcogenides (2D TMDCs) exhibit promising characteristics in miniaturized nonlinear optical frequency converters, due to their inversion asymmetry and large second-order nonlinear susceptibility. However, these materials usually have a very short light interaction lengths with the pump laser because they are atomically thin, such that second-harmonic generation (SHG) is generally inefficient. In this paper, we fabricate a judiciously structured 150-nm-thick planar surface consisting of monolayer tungsten diselenide and sub-20-nm-wide gold trenches on flexible substrates, reporting ~7000-fold SHG enhancement without peak broadening or background in the spectra as compared to WSe2 on as-grown sapphire substrates. Our proof-of-concept experiment yields effective second-order nonlinear susceptibility of 2.1 × 104 pm/V. Three orders of magnitude enhancement is maintained with pump wavelength ranging from 800 nm to 900 nm, breaking the limitation of narrow pump wavelength range for cavity-enhanced SHG. In addition, SHG amplitude can be dynamically controlled via selective excitation of the lateral gap plasmon by rotating the laser polarization. Such fully open, flat and ultrathin profile enables a great variety of functional samples with high SHG from one patterned silicon substrate, favoring scalable production of nonlinear converters. The surface accessibility also enables integration with other optical components for information processing in an ultrathin and flexible form.

  3. First and second harmonic generation of the XAl{sub 2}Se{sub 4} (X=Zn,Cd,Hg) defect chalcopyrite compounds

    Energy Technology Data Exchange (ETDEWEB)

    Ouahrani, Tarik, E-mail: tarik_ouahrani@yahoo.fr [Laboratoire de Physique Theorique, Universite de Tlemcen, B.P.230,13000 Tlemcen (Algeria); Ecole Preparatoire en Sciences et Techniques, Depertement de Physique EPST-T, Tlemcen 13000 (Algeria); Khenata, R. [Laboratoire de Physique Quantique et de Modelisation Mathematique (LPQ3M), Universite de Mascara, 29000 Mascara (Algeria); Lasri, B. [Laboratoire de Physique Theorique, Universite de Tlemcen, B.P.230,13000 Tlemcen (Algeria); Universite Dr Tahar Moulay de Saida, B.P. 138, Cite el Nasr, Saida 20000 (Algeria); Reshak, Ali H. [School of Complex systems, FFPW- South Bohemia University, Nove Hrady 37333 (Czech Republic); School of Material Engineering, Malaysia University of Perlis, P.O Box 77, d/a Pejabat Pos Besar, 01007 Kangar, Perlis (Malaysia); Bouhemadou, A. [Department of Physics, Faculty of Sciences, University of Setif, 19000 Setif (Algeria); Bin-Omran, S. [Department of Physics and Astronomy, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia)

    2012-09-15

    The chemical bonding of the ZnAl{sub 2}Se{sub 4}, CdAl{sub 2}Se{sub 4} and HgAl{sub 2}Se{sub 4} defect chalcopyrites has been studied in the framework of the quantum theory of atoms in molecules (AIM). The GW quasi-particle approximation is used to correct the DFT-underestimation of energy gap, and as a consequence the linear and nonlinear optical properties are significantly enhanced. The second harmonic generation (SHG) displays certain dependence with the ionicity degree decrease through the dependency of the SHG on the band gap. The occurrence of the AIM saddle point is characterized and some clarifying features in relationship with the density topology are exposed, which enable to understand the relation with the second harmonic generation effect.

  4. Energy exchange properties during second-harmonic generation in finite one-dimensional photonic band-gap structures with deep gratings

    Science.gov (United States)

    D'Aguanno, Giuseppe; Centini, Marco; Scalora, Michael; Sibilia, Concita; Bertolotti, Mario; Bloemer, Mark J.; Bowden, Charles M.

    2003-01-01

    We study second-harmonic generation in finite, one-dimensional, photonic band-gap structures with large index contrast in the regime of pump depletion and global phase-matching conditions. We report a number of surprising results: above a certain input intensity, field dynamics resemble a multiwave mixing process, where backward and forward components compete for the available energy; the pump field is mostly reflected, revealing a type of optical limiting behavior; and second-harmonic generation becomes balanced in both directions, showing unusual saturation effects with increasing pump intensity. This dynamics was unexpected, and it is bound to influence the way one goes about thinking and designing nonlinear frequency conversion devices in a practical way.

  5. High-harmonic generation and parametric amplification in the soft X-rays from extended electron trajectories

    Science.gov (United States)

    Seres, J.; Seres, E.; Landgraf, B.; Ecker, B.; Aurand, B.; Kuehl, T.; Spielmann, C.

    2014-01-01

    We report, for the first time, the generation of high-order harmonics in a spectral range between 200 eV and 1 keV with an unusual spectral property: only every 4th (4i + 1, i∈ℵ) harmonic line appears, whereas the usual high-harmonic spectra consist of every odd (2i + 1) harmonic. We attribute this unique property to the quantum path interference of two extended electron trajectories that experience multiple re-scattering. In the well-established theory, electrons emitted via tunnel ionisation are accelerated by a laser field, return to the ion and recombine. The acceleration typically lasts for less than one optical cycle, and the electrons radiate in the extreme ultraviolet range at recombination. In contrast, for extended trajectories, electrons are accelerated over two or more optical cycles. Here, we demonstrate that two sets of trajectories dominate and provide substantial contributions to the generated soft X-ray radiation because they fulfil the resonance condition for X-ray parametric amplification. PMID:24577220

  6. Quasi-supercontinuum source in the extreme ultraviolet using multiple frequency combs from high-harmonic generation.

    Science.gov (United States)

    Wünsche, Martin; Fuchs, Silvio; Aull, Stefan; Nathanael, Jan; Möller, Max; Rödel, Christian; Paulus, Gerhard G

    2017-03-20

    A quasi-supercontinuum source in the extreme ultraviolet (XUV) is demonstrated using a table-top femtosecond laser and a tunable optical parametric amplifier (OPA) as a driver for high-harmonic generation (HHG). The harmonic radiation, which is usually a comb of odd multiples of the fundamental frequency, is generated by near-infrared (NIR) laser pulses from the OPA. A quasi-continuous XUV spectrum in the range of 30 to 100 eV is realized by averaging over multiple harmonic comb spectra with slightly different fundamental frequencies and thus different spectral spacing between the individual harmonics. The driving laser wavelength is swept automatically during an averaging time period. With a total photon flux of 4×109 photons/s in the range of 30 eV to 100 eV and 1×107photons/s in the range of 100 eV to 200 eV, the resulting quasi-supercontinuum XUV source is suited for applications such as XUV coherence tomography (XCT) or near-edge absorption fine structure spectroscopy (NEXAFS).

  7. Measurements of nonlinear harmonic generation at the Advanced Photon Source's SASE FEL

    CERN Document Server

    Biedron, S G; Borland, M; Dejus, Roger J; Den Hartog, P K; Erdmann, M; Fawley, W M; Freund, H P; Gluskin, E; Huang, Z; Kim, K J; Lewellen, J W; Li, Y; Lumpkin, Alex H; Milton, S V; Moog, E; Nassiri, A; Sajaev, Vadim; Wiemerslage, G; Yang, B X

    2002-01-01

    SASE saturation was recently achieved at the Advanced Photon Source's SASE FEL in the low-energy undulator test line at 530 nm and 385 nm. The electron beam microbunching becomes more and more prominent until saturation is achieved. This bunching causes nonlinear harmonic emission that extends the usefulness of a SASE system in achieving shorter FEL wavelengths for the same electron beam energy. We have investigated the intensity of the fundamental and second harmonic undulator radiation as a function of distance along the undulator line and present the experimental results and compare them to numerical simulations. In addition, we have measured the single-shot second harmonic spectra as well as the simultaneous fundamental and second harmonic spectra and present the experimental results.

  8. Resonant third harmonic generation of KrF laser in Ar gas

    Energy Technology Data Exchange (ETDEWEB)

    Rakowski, R. [Department of Experimental Physics, University of Szeged, 6720 Szeged, Dóm tér 9 (Hungary); Institute of Optoelectronics, Military University of Technology, Gen. S. Kaliskiego 2, 00–908 Warsaw (Poland); Barna, A. [Department of Experimental Physics, University of Szeged, 6720 Szeged, Dóm tér 9 (Hungary); Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, EURATOM Association HAS, 1121 Budapest, XII. Konkoly Thege Miklós út 29-33 (Hungary); Suta, T.; Földes, I. B. [Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, EURATOM Association HAS, 1121 Budapest, XII. Konkoly Thege Miklós út 29-33 (Hungary); Bohus, J.; Szatmári, S. [Department of Experimental Physics, University of Szeged, 6720 Szeged, Dóm tér 9 (Hungary); Mikołajczyk, J.; Bartnik, A.; Fiedorowicz, H. [Institute of Optoelectronics, Military University of Technology, Gen. S. Kaliskiego 2, 00–908 Warsaw (Poland); Verona, C. [Department of Mechanical Engineering, University “Tor Vergata”, Via Orazio Raimondo, 18–00173, Rome (Italy); Verona Rinati, G. [Department of Industrial Engineering, University “Tor Vergata”, Via Orazio Raimondo, 18–00173, Rome (Italy); Margarone, D. [Institute of Physics ASCR, v.v.i. (FZU), ELI-Beamlines Project, 182 21 Prague (Czech Republic); Nowak, T. [Institute of Nuclear Physics, PAN, E. Radzikowskiego 152, 31–342 Cracow (Poland); and others

    2014-12-15

    Investigations of emission of harmonics from argon gas jet irradiated by 700 fs, 5 mJ pulses from a KrF laser are presented. Harmonics conversion was optimized by varying the experimental geometry and the nozzle size. For the collection of the harmonic radiation silicon and solar-blind diamond semiconductor detectors equipped with charge preamplifiers were applied. The possibility of using a single-crystal CVD diamond detector for separate measurement of the 3rd harmonic in the presence of a strong pumping radiation was explored. Our experiments show that the earlier suggested 0.7% conversion efficiency can really be obtained, but only in the case when phase matching is optimized with an elongated gas target length corresponding to the length of coherence.

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

    Science.gov (United States)

    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.

  10. Highlighting the harmonic regime generated by electric locomotives equipped with DC motors

    Science.gov (United States)

    Baciu, I.; Cunţan, C. D.

    2018-01-01

    The paper presents the results of measurements made using the C.A. 8334 power quality analyzer on an electric locomotive equipped with DC motors. We carried out determinations of the current-voltage regime using a locomotive motor. The harmonic regime of the other motors being identical to the analysed one, we could easily deduce the effects caused by the entire locomotive. The data measured with the analyzer were firstly transferred into a computer system using the Qualistar software, followed by data processing in Excel, enabling therefore a graphical representation of the characteristic parameters of power quality. Based on the acquired data, we determined the power factor, as well as the active, reactive and apparent power. The measurements revealed high values of the current harmonics, fact that required some measures to be taken for reducing the values of these harmonics. For this, we ran a simulation using the PSCAD/EMTDC software, by introducing LC filters in tune with the harmonic frequencies. The result was a significant reduction in the harmonic regime, either in the harmonics values or the power factor and reactive power.

  11. Nonlinear optics from an ab initio approach by means of the dynamical Berry phase: Application to second- and third-harmonic generation in semiconductors

    Science.gov (United States)

    Attaccalite, C.; Grüning, M.

    2013-12-01

    We present an ab initio real-time-based computational approach to study nonlinear optical properties in condensed matter systems that is especially suitable for crystalline solids and periodic nanostructures. The equations of motion and the coupling of the electrons with the external electric field are derived from the Berry-phase formulation of the dynamical polarization [Souza , Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.69.085106 69, 085106 (2004)]. Many-body effects are introduced by adding single-particle operators to the independent-particle Hamiltonian. We add a Hartree operator to account for crystal local effects and a scissor operator to correct the independent particle band structure for quasiparticle effects. We also discuss the possibility of accurately treating excitonic effects by adding a screened Hartree-Fock self-energy operator. The approach is validated by calculating the second-harmonic generation of SiC and AlAs bulk semiconductors: an excellent agreement is obtained with existing ab initio calculations from response theory in frequency domain [Luppi , Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.82.235201 82, 235201 (2010)]. We finally show applications to the second-harmonic generation of CdTe and the third-harmonic generation of Si.

  12. Design Practices in Harmonic Analysis Studies Applied to Industrial Electrical Power Systems

    Directory of Open Access Journals (Sweden)

    S. F. Mekhamer

    2013-08-01

    Full Text Available Power system harmonics may cause several problems, such as malfunctions of electrical equipment, premature equipment failures and plant shutdowns. Accordingly, mitigation of these harmonics is considered an important target especially for industrial applications where any short downtime period may lead to great economic losses. Harmonic analysis studies are necessary to analyze the current and voltage harmonic levels and check if these levels comply with the contractual or international standard limits. If the studies reveal that the preset limits are exceeded, then a suitable harmonic mitigation technique should be installed. Harmonic analysis studies in the industrial electrical systems are discussed in many references. However, a comprehensive procedure for the steps required to perform a harmonic study is rarely found in the literature even though it is strongly needed for design engineers. This paper provides a comprehensive procedure for the steps required to perform a harmonic study in the form of a flowchart, based on industrial research and experience. Hence, this paper may be considered as a helpful guide for design engineers and consultants of the industrial sector.

  13. [Structural analysis of normal corneas and diseased corneas by applying second harmonic generation].

    Science.gov (United States)

    Morishige, Naoyuki

    2011-11-01

    We have established a second harmonic generation (SHG) microscopy system for imaging of the human cornea with a mode-locked femtosecond laser and a laser confocal microscope. This SHG microscopy system has allowed us to scan corneal tissue noninvasively ex vivo and to obtain three-dimensional images of corneal collagen lamellae. Such three-dimensional imaging of the normal anterior cornea revealed that collagen lamellae at the anterior stroma are inter-woven and adhere to Bowman membrane with these adherent lamellae being designated "sutural lamellae." Sutural lamellae adhere to Bowman membrane at an angle of approximately 19 degrees, whereas the angle of lamellae in the mid-stroma relative to Bowman membrane is smaller. We hypothesize that the structural unit consisting of both Bowman membrane and the sutural lamellae contributes to the rigidity and anterior curvature of the cornea. SHG imaging of keratoconic corneas revealed an either abnormal or a total lack of structure of the sutural lamellae, suggesting that this abnormality might be related to that of the corneal anterior curvature in such corneas. Furthermore, SHG imaging of corneas affected by stromal edema showed that the structure of the sutural lamellae was maintained, although abnormal collagen signals both above and below Bowman membrane were detected in corneas affected by clinical stromal edema for more than 12 months. SHG imaging of the structure of collagen lamellae in normal and diseased corneas thus has the potential to provide insight both into the mechanism for maintenance of corneal curvature as well as into the pathophysiology of corneal diseases.

  14. Abnormalities of stromal structure in the bullous keratopathy cornea identified by second harmonic generation imaging microscopy.

    Science.gov (United States)

    Morishige, Naoyuki; Yamada, Norihiro; Zhang, Xu; Morita, Yukiko; Yamada, Naoyuki; Kimura, Kazuhiro; Takahara, Atsushi; Sonoda, Koh-Hei

    2012-07-27

    To identify structural alterations in collagen lamellae and the transdifferentiation of keratocytes into myofibroblasts in the corneal stroma of bullous keratopathy (BK) patients and to examine the relation of such changes to the duration of stromal edema or the underlying cause of BK. Six normal human corneas and 16 BK corneas were subjected to second harmonic generation (SHG) imaging microscopy to allow three-dimensional (3-D) reconstruction of collagen lamellae. Expression of α-smooth muscle actin (αSMA) was examined by immunofluorescence analysis and conventional laser confocal microscopy. Collagen lamellae were interwoven at the anterior stroma and uniformly aligned at the posterior stroma, whereas αSMA was not detected throughout the entire stroma of the normal cornea. Nine (56%) and 7 (44%) of the 16 BK corneas showed abnormal collagen structure at the anterior and posterior stroma, respectively. Expression of αSMA was detected in the anterior or posterior stroma of 7 (44%) and 6 (38%) of the 16 BK corneas, respectively. Disorganization of collagen lamellae and myofibroblastic transdifferentiation were detected only in corneas with a duration of stromal edema of at least 12 months. Corneas with BK as a result of birth injury showed abnormal collagen structure at the posterior stroma, whereas those with BK resulting from laser iridotomy did not. Changes in the structure of the entire stroma were detected in BK corneas with a duration of stromal edema of at least 12 months, suggesting that such changes may be progressive. In addition, the underlying cause of BK may influence structural changes at the posterior stroma.

  15. Detection of subepithelial fibrosis associated with corneal stromal edema by second harmonic generation imaging microscopy.

    Science.gov (United States)

    Morishige, Naoyuki; Yamada, Naoyuki; Teranishi, Shinichiro; Chikama, Tai-ichiro; Nishida, Teruo; Takahara, Atsushi

    2009-07-01

    Human corneas with or without stromal edema were examined by second harmonic generation (SHG) imaging microscopy to characterize stromal collagen organization. Tissue buttons from 31 corneas with stromal edema and 8 normal corneas were fixed, and 3-mm(2) blocks were cut and stained with phalloidin, to visualize the cytoskeleton. The blocks were examined by SHG imaging with a laser confocal microscope and a mode-locked titanium:sapphire femtosecond laser. Samples were scanned to a depth of 150 microm from the surface of Bowman's layer, and SHG forward- and backscatter signals were collected. Phalloidin staining was detected by conventional laser confocal microscopy. The three-dimensional structure of the anterior segment of the cornea was reconstructed from stacked SHG images. Three-dimensional reconstruction of SHG signals showed adherence of interwoven collagen lamellae in the anterior stroma to Bowman's layer in both normal and edematous corneas. Abnormal SHG signals at the level of Bowman's layer were observed in edematous corneas; three-dimensional images revealed that these signals were actually localized above Bowman's layer and were indicative of subepithelial fibrosis. Phalloidin staining showed transdifferentiation of stromal cells into fibroblastic cells in edematous corneas. The incidence of subepithelial fibrosis or of fibroblastic cells increased beginning 12 months after the onset of clinical stromal edema. SHG imaging of the anterior segment of edematous corneas revealed a normal appearance of interwoven collagen lamellae in the anterior stroma. The development of subepithelial fibrosis beginning 12 months after the onset of edema suggests that stromal edema may be a progressive disease.

  16. Second-harmonic generation reveals a relationship between metastatic potential and collagen fiber structure

    Science.gov (United States)

    Burke, Kathleen A.; Dawes, Ryan P.; Cheema, Mehar K.; Perry, Seth; Brown, Edward

    2014-02-01

    Second Harmonic Generation (SHG) of collagen signals allows for the analysis of collagen structural changes throughout metastatic progression. The directionality of coherent SHG signals, measured through the ratio of the forward-propagating to backward propagating signal (F/B ratio), is affected by fibril diameter, spacing, and order versus disorder of fibril packing within a fiber. As tumors interact with their microenvironment and metastasize, it causes changes in these parameters, and concurrent changes in the F/B ratio. Specifically, the F/B ratio of breast tumors that are highly metastatic to the lymph nodes is significantly higher than those in tumors with restricted lymph node involvement. We utilized in vitro analysis of tumor cell motility through collagen gels of different microstructures, and hence different F/B ratios, to explore the relationship between collagen microstructures and metastatic capabilities of the tumor. By manipulating environmental factors of fibrillogenesis and biochemical factors of fiber composition we created methods of varying the average F/B ratio of the gel, with significant changes in fiber structure occurring as a result of alterations in incubation temperature and increasing type III collagen presence. A migration assay was performed using simultaneous SHG and fluorescent imaging to measure average penetration depth of human tumor cells into the gels of significantly different F/B ratios, with preliminary data demonstrating that cells penetrate deeper into gels of higher F/B ratio caused by lower type III collagen concentration. Determining the role of collagen structure in tumor cell motility will aid in the future prediction metastatic capabilities of a primary tumor.

  17. Polarization Second Harmonic Generation Discriminates Between Fresh and Aged Starch-Based Adhesives Used in Cultural Heritage.

    Science.gov (United States)

    Psilodimitrakopoulos, Sotiris; Gavgiotaki, Evaggelia; Melessanaki, Kristallia; Tsafas, Vassilis; Filippidis, George

    2016-10-01

    In this work, we report that polarization second harmonic generation (PSHG) microscopy, commonly used in biomedical imaging, can quantitatively discriminate naturally aged from fresh starch-based glues used for conservation or restoration of paintings, works of art on paper, and books. Several samples of fresh and aged (7 years) flour and starch pastes were investigated by use of PSHG. In these types of adhesives, widely used in cultural heritage conservation, second harmonic generation (SHG) contrast originates primarily from the starch granules. It was found that in aged glues, the starch SHG effective orientation (SHG angle, θ) shifts to significantly higher values in comparison to the fresh granules. This shift is attributed to the different degree of granule hydration between fresh and aged adhesives. Thus noninvasive high-resolution nonlinear scattering can be employed to detect and quantify the degree of deterioration of restoration adhesives and to provide guidance toward future conservation treatments.

  18. Phase matching of high order harmonic generation using dynamic phase modulation caused by a non-collinear modulation pulse

    Science.gov (United States)

    Cohen, Oren; Kapteyn, Henry C.; Mumane, Margaret M.

    2010-02-16

    Phase matching high harmonic generation (HHG) uses a single, long duration non-collinear modulating pulse intersecting the driving pulse. A femtosecond driving pulse is focused into an HHG medium (such as a noble gas) to cause high-harmonic generation (HHG), for example in the X-ray region of the spectrum, via electrons separating from and recombining with gas atoms. A non-collinear pulse intersects the driving pulse within the gas, and modulates the field seen by the electrons while separated from their atoms. The modulating pulse is low power and long duration, and its frequency and amplitude is chosen to improve HHG phase matching by increasing the areas of constructive interference between the driving pulse and the HHG, relative to the areas of destructive interference.

  19. A quantitative S-Matrix approach to high-order harmonic generation from multiphoton to tunneling regimes.

    Science.gov (United States)

    Plaja, L; Pérez-Hernández, J A

    2007-04-02

    We present a S-matrix description of the process of high order harmonic generation during the interaction of atoms with strong electromagnetic fields. In contrast with the state-of-the-art approaches, our model does not employ the stationary phase approximation and accounts as well for the continuum-continuum transitions. Therefore we are able to reproduce quantitatively the higher frequency part of the spectrum for arbitrary pulse shapes, and for intensities corresponding to multiphoton, tunnel and soft over-the barrier ionization regimes. In addition this model can be implemented very efficiently in a Personal Computer to calculate the harmonic generation for the atom interacting with an eight-cycle pulse at lambda =800 nm in, roughly, ten minutes (a reduction of two orders of magnitude from the typical time requirements of the exact integration).

  20. Pseudospectral Maxwell solvers for an accurate modeling of Doppler harmonic generation on plasma mirrors with particle-in-cell codes

    Science.gov (United States)

    Blaclard, G.; Vincenti, H.; Lehe, R.; Vay, J. L.

    2017-09-01

    With the advent of petawatt class lasers, the very large laser intensities attainable on target should enable the production of intense high-order Doppler harmonics from relativistic laser-plasma mirror interactions. At present, the modeling of these harmonics with particle-in-cell (PIC) codes is extremely challenging as it implies an accurate description of tens to hundreds of harmonic orders on a broad range of angles. In particular, we show here that due to the numerical dispersion of waves they induce in vacuum, standard finite difference time domain (FDTD) Maxwell solvers employed in most PIC codes can induce a spurious angular deviation of harmonic beams potentially degrading simulation results. This effect was extensively studied and a simple toy model based on the Snell-Descartes law was developed that allows us to finely predict the angular deviation of harmonics depending on the spatiotemporal resolution and the Maxwell solver used in the simulations. Our model demonstrates that the mitigation of this numerical artifact with FDTD solvers mandates very high spatiotemporal resolution preventing realistic three-dimensional (3D) simulations even on the largest computers available at the time of writing. We finally show that nondispersive pseudospectral analytical time domain solvers can considerably reduce the spatiotemporal resolution required to mitigate this spurious deviation and should enable in the near future 3D accurate modeling on supercomputers in a realistic time to solution.

  1. Third-harmonic generation and multi-photon excitation fluorescence imaging microscopy techniques for online art conservation diagnosis.

    Science.gov (United States)

    Gualda, Emilio J; Filippidis, George; Melessanaki, Kristalia; Fotakis, Costas

    2009-03-01

    We present an appropriate methodology and results for using third-harmonic generation (THG) modality for nondestructive high resolution imaging measurements of varnished structures in model painted artifacts. Detection takes place in the reflection mode, demonstrating the ability of the technique to be applied to the evaluation of original artworks. Furthermore, multi-photon excitation fluorescence images were obtained, providing complementary information related to the identification of the chemical composition of the artifacts.

  2. Comparison between length and velocity gauges in quantum simulations of high-order harmonic generation

    DEFF Research Database (Denmark)

    Han, Yong-Chang; Madsen, Lars Bojer

    2010-01-01

    We solve the time-dependent Schrödinger equation for atomic hydrogen in an intense field using spherical coordinates with a radial grid and a spherical harmonic basis for the angular part. We present the high-order harmonic spectra based on three different forms, the dipole, dipole velocity......, and acceleration forms, and two gauges, the length and velocity gauges. The relationships among the harmonic phases obtained from the Fourier transform of the three forms are discussed in detail. Although quantum mechanics is gauge invariant and the length and velocity gauges should give identical results, the two...... gauges present different computation efficiencies, which reflects the different behavior in terms of characteristics of the physical couplings acting in the two gauges. In order to obtain convergence, more angular momentum states are required in the length gauge, while more grid points are required...

  3. Quasi-phase matching of soft X-ray light from high-order harmonic generation using waveguide structures

    Science.gov (United States)

    Gibson, Emily Abbott

    Ultrafast laser technology has made it possible to achieve extremely high field intensities, above 1018 W/cm2, or alternatively, light pulses with extremely short time durations corresponding to only a few femtoseconds (10-15 s). In this high intensity regime, the laser field energy is comparable to the binding energy of an electron to an atom. One result of this highly non-perturbative atom-light interaction is the process of high-order harmonic generation (HHG). In HHG, the strong laser field first ionizes the atom. The subsequent motion of the free electron is controlled by the oscillating laser field, and the electron can reach kinetic energies many times that of the original binding energy to the atom. The high energy electron can then recollide with its parent ion, releasing a high energy photon. This process occurs for many atoms driven coherently by the same laser field, resulting in a coherent, laser-like beam of ultrafast light spanning the ultraviolet to soft X-ray regions of the spectrum. In this thesis, I will present two major breakthroughs in the field of high harmonic generation. First, I will discuss work on quasi-phase matching of high harmonic generation, which has allowed increased conversion efficiency of high harmonic light up to the water window region of the soft X-ray spectrum (˜300 eV) for the first time.[31] This spectral region is significant because at these photon energies, water is transparent while carbon strongly absorbs, making it a useful light source for very high resolution contrast microscopy on biological samples. Since the resolution is on order of the wavelength of the light (˜4 nm for 300 eV), detailed structures of cells and DNA can be viewed. A table-top source of light in the water window soft X-ray region would greatly benefit biological and medical research. Second, I will present work on the generation of very high harmonic orders from ions. This work is the first to show that harmonic emission from ions is of

  4. A Comparative Study of the Use of Harmonic Scalpel versus ...

    African Journals Online (AJOL)

    2017-05-18

    May 18, 2017 ... Breast cancer is the most site‑specific cancer in women.[1] For patients who present late, radical ... The clinical information such as age of the patient, age of menarche, age of menopause, parity of the patient, .... Incidence of hypertension in harmonic scalpel group was 12% and electrocautery group was.

  5. Measuring the effect of a Western diet on liver tissue architecture by FLIM autofluorescence and harmonic generation microscopy.

    Science.gov (United States)

    Ranjit, Suman; Dvornikov, Alexander; Dobrinskikh, Evgenia; Wang, Xiaoxin; Luo, Yuhuan; Levi, Moshe; Gratton, Enrico

    2017-07-01

    The phasor approach to auto-fluorescence lifetime imaging was used to identify and characterize a long lifetime species (LLS) (~7.8 ns) in livers of mice fed with a Western diet. The size of the areas containing this LLS species depends on the type of diet and the size distribution shows Western diet has much larger LLS sizes. Combination of third harmonic generation images with FLIM identified the LLS species with fat droplets and the droplet size distribution was estimated. Second harmonic generation microscopy combined with phasor FLIM shows that there is an increase in fibrosis with a Western diet. A new decomposition in three components of the phasor plot shows that a Western diet is correlated with a higher fraction of free NADH, signifying more reducing condition and more glycolytic condition. Multiparametric analysis of phasor distribution shows that from the distribution of phasor points, a Western diet fed versus a low fat diet fed samples of mice livers can be separated. The phasor approach for the analysis of FLIM images of autofluorescence in liver specimens can result in discovery of new fluorescent species and then these new fluorescent species can help assess tissue architecture. Finally integrating FLIM and second and third harmonic analysis provides a measure of the advancement of fibrosis as an effect of diet.

  6. Second-Harmonic Generation and Shielding Effects on Alkali Clusters on Ultrathin Organic Films

    DEFF Research Database (Denmark)

    Balzer, F.; Rubahn, Horst-Günter

    2001-01-01

    We demonstrate the nonlinear optical activity of large Na and K clusters, grown on Au metal film-supported alkane thiol monolayers of different chain lengths. Both the total optical second-harmonic signal intensity as well as its dependence on the angle of incidence depend on the surface coverage...

  7. Voltage Unbalance and Harmonic Compensation in Microgrids by Cooperation of Distributed Generators and Active Power Filters

    DEFF Research Database (Denmark)

    Hashempour, Mohammad M.; Savaghebi, Mehdi; Quintero, Juan Carlos Vasquez

    2016-01-01

    , selective virtual impedance and voltage/current regulators. Based on the secondary control, at first voltage harmonic compensation and voltage unbalance compensation of point of common coupling (PCC), that might includes sensitive loads, is carried out by DGs. Voltage compensation of PCC by DGs may cause...

  8. Interference Effects in the Optical Second Harmonic Generation from Ultrathin Alkali Films

    DEFF Research Database (Denmark)

    Balzer, Frank; Rubahn, Horst-Günter

    2000-01-01

    Interference effects are shown to strongly modulate the transmission second harmonic signal (fundamental wavelength 1067 nm) from rough alkali island films grown on insulating substrates if one varies the angle of incidence. Depending on growth conditions and substrate thickness, the measured...... accurate values of the ratios of the relevant nonlinear optical coefficients....

  9. Laser-induced bound-state phases in high-order harmonic generation

    DEFF Research Database (Denmark)

    Etches, Adam; B. Gaarde, Mette; Bojer Madsen, Lars

    2012-01-01

    We present single-molecule and macroscopic calculations showing that laser-induced Stark shifts contribute significantly to the phase of high-order harmonics from polar molecules. This is important for orbital tomography, where phases of field-free dipole matrix elements are needed in order...

  10. Stromal alterations in ovarian cancers via wavelength dependent Second Harmonic Generation microscopy and optical scattering.

    Science.gov (United States)

    Tilbury, Karissa B; Campbell, Kirby R; Eliceiri, Kevin W; Salih, Sana M; Patankar, Manish; Campagnola, Paul J

    2017-02-06

    Ovarian cancer remains the most deadly gynecological cancer with a poor aggregate survival rate; however, the specific rates are highly dependent on the stage of the disease upon diagnosis. Current screening and imaging tools are insufficient to detect early lesions and are not capable of differentiating the subtypes of ovarian cancer that may benefit from specific treatments. As an alternative to current screening and imaging tools, we utilized wavelength dependent collagen-specific Second Harmonic Generation (SHG) imaging microscopy and optical scattering measurements to probe the structural differences in the extracellular matrix (ECM) of normal stroma, benign tumors, endometrioid tumors, and low and high-grade serous tumors. The SHG signatures of the emission directionality and conversion efficiency as well as the optical scattering are related to the organization of collagen on the sub-micron size scale and encode structural information. The wavelength dependence of these readouts adds additional characterization of the size and distribution of collagen fibrils/fibers relative to the interrogating wavelengths. We found a strong wavelength dependence of these metrics that are related to significant structural differences in the collagen organization and are consistent with the dualistic classification of type I and II serous tumors. Moreover, type I endometrioid tumors have strongly differing ECM architecture than the serous malignancies. The SHG metrics and optical scattering measurements were used to form a linear discriminant model to classify the tissues, and we obtained high accuracy (>90%) between high-grade serous tumors from the other tissue types. High-grade serous tumors account for ~70% of ovarian cancers, and this delineation has potential clinical applications in terms of supplementing histological analysis, understanding the etiology, as well as development of an in vivo screening tool. SHG and optical scattering measurements provide sub

  11. Real time selective harmonic minimization for multilevel inverters using genetic algorithm and artifical neural network angle generation

    Energy Technology Data Exchange (ETDEWEB)

    Filho, Faete J [ORNL; Tolbert, Leon M [ORNL; Ozpineci, Burak [ORNL

    2012-01-01

    The work developed here proposes a methodology for calculating switching angles for varying DC sources in a multilevel cascaded H-bridges converter. In this approach the required fundamental is achieved, the lower harmonics are minimized, and the system can be implemented in real time with low memory requirements. Genetic algorithm (GA) is the stochastic search method to find the solution for the set of equations where the input voltages are the known variables and the switching angles are the unknown variables. With the dataset generated by GA, an artificial neural network (ANN) is trained to store the solutions without excessive memory storage requirements. This trained ANN then senses the voltage of each cell and produces the switching angles in order to regulate the fundamental at 120 V and eliminate or minimize the low order harmonics while operating in real time.

  12. Theory of optical second-harmonic generation from a sphere of centrosymmetric material: small-particle limit

    Science.gov (United States)

    Dadap, Jerry I.; Shan, Jie; Heinz, Tony F.

    2004-07-01

    The electromagnetic theory of optical second-harmonic generation from small spherical particles comprised of centrosymmetric material is presented. The interfacial region where the inversion symmetry is broken provides a source of the nonlinearity. This response is described by a general surface nonlinear susceptibility tensor for an isotropic interface. In addition, the appropriate weak bulk terms for an isotropic centrosymmetric medium are introduced. The linear optical response of the sphere and the surrounding region is assumed to be isotropic, but otherwise arbitrary. The analysis is carried out to leading order in the ratio of (a/λ), the particle radius to the wavelength of the incident light, and can be considered as the Rayleigh limit for second-harmonic generation from a sphere. Emission from the sphere arises from both induced electric dipole and electric quadrupole moments at the second-harmonic frequency. The former requires a nonlocal excitation mechanism in which the phase variation of the pump beam across the sphere is considered, while the latter is present for a local-excitation mechanism. The locally excited electric dipole term, analogous to the source for linear Rayleigh scattering, is absent for the nonlinear case because of the overall inversion symmetry of the problem. The second-harmonic field is found to scale as (a/λ)3 and to be completely determined by two effective nonlinear susceptibility coefficients formed as a prescribed combination of the surface and bulk nonlinearities. Characteristic angular and polarization selection rules resulting from the mechanism of the radiation process are presented. Various experimental aspects of the problem are examined, including the expected signal strengths and methods of determining the nonlinear susceptibilities. The spectral characteristics associated with the geometry of a small sphere are also discussed, and distinctive localized plasmon resonances are identified.

  13. Assessment of foetal exposure to the homogeneous magnetic field harmonic spectrum generated by electricity transmission and distribution networks.

    Science.gov (United States)

    Fiocchi, Serena; Liorni, Ilaria; Parazzini, Marta; Ravazzani, Paolo

    2015-04-01

    During the last decades studies addressing the effects of exposure to Extremely Low Frequency Electromagnetic Fields (ELF-EMF) have pointed out a possible link between those fields emitted by power lines and childhood leukaemia. They have also stressed the importance of also including in the assessment the contribution of frequency components, namely harmonics, other than the fundamental one. Based on the spectrum of supply voltage networks allowed by the European standard for electricity quality assessment, in this study the exposure of high-resolution three-dimensional models of foetuses to the whole harmonic content of a uniform magnetic field with a fundamental frequency of 50 Hz, was assessed. The results show that the main contribution in terms of induced electric fields to the foetal exposure is given by the fundamental frequency component. The harmonic components add some contributions to the overall level of electric fields, however, due to the extremely low permitted amplitude of the harmonic components with respect to the fundamental, their amplitudes are low. The level of the induced electric field is also much lower than the limits suggested by the guidelines for general public exposure, when the amplitude of the incident magnetic field is set at the maximum permitted level.

  14. Assessment of Foetal Exposure to the Homogeneous Magnetic Field Harmonic Spectrum Generated by Electricity Transmission and Distribution Networks

    Directory of Open Access Journals (Sweden)

    Serena Fiocchi

    2015-04-01

    Full Text Available During the last decades studies addressing the effects of exposure to Extremely Low Frequency Electromagnetic Fields (ELF-EMF have pointed out a possible link between those fields emitted by power lines and childhood leukaemia. They have also stressed the importance of also including in the assessment the contribution of frequency components, namely harmonics, other than the fundamental one. Based on the spectrum of supply voltage networks allowed by the European standard for electricity quality assessment, in this study the exposure of high-resolution three-dimensional models of foetuses to the whole harmonic content of a uniform magnetic field with a fundamental frequency of 50 Hz, was assessed. The results show that the main contribution in terms of induced electric fields to the foetal exposure is given by the fundamental frequency component. The harmonic components add some contributions to the overall level of electric fields, however, due to the extremely low permitted amplitude of the harmonic components with respect to the fundamental, their amplitudes are low. The level of the induced electric field is also much lower than the limits suggested by the guidelines for general public exposure, when the amplitude of the incident magnetic field is set at the maximum permitted level.

  15. Label-free imaging immune cells and collagen in atherosclerosis with two-photon and second harmonic generation microscopy

    Directory of Open Access Journals (Sweden)

    Chunqiang Li

    2016-01-01

    Full Text Available Atherosclerosis has been recognized as a chronic inflammation disease, in which many types of cells participate in this process, including lymphocytes, macrophages, dendritic cells (DCs, mast cells, vascular smooth muscle cells (SMCs. Developments in imaging technology provide the capability to observe cellular and tissue components and their interactions. The knowledge of the functions of immune cells and their interactions with other cell and tissue components will facilitate our discovery of biomarkers in atherosclerosis and prediction of the risk factor of rupture-prone plaques. Nonlinear optical microscopy based on two-photon excited autofluorescence and second harmonic generation (SHG were developed to image mast cells, SMCs and collagen in plaque ex vivo using endogenous optical signals. Mast cells were imaged with two-photon tryptophan autofluorescence, SMCs were imaged with two-photon NADH autofluorescence, and collagen were imaged with SHG. This development paves the way for further study of mast cell degranulation, and the effects of mast cell derived mediators such as induced synthesis and activation of matrix metalloproteinases (MMPs which participate in the degradation of collagen.

  16. Control of threshold enhancements in harmonic generation by atoms in a two-color laser field with orthogonal polarizations

    Science.gov (United States)

    Starace, Anthony F.; Frolov, M. V.; Manakov, N. L.; Sarantseva, T. S.; Silaev, A. A.; Vvedenskii, N. V.

    2017-04-01

    Threshold phenomena (or channel-closing effects) are analyzed in high-order harmonic generation (HHG) by atoms in a two-color laser field with orthogonal linearly polarized components of a fundamental field and its second harmonic. We show that the threshold behavior of HHG rates for the case of a weak second harmonic component is sensitive to the parity of a closing multiphoton ionization channel and the spatial symmetry of the initial bound state of the target atom, while for the case of comparable intensities of both components, suppression of threshold phenomena is observed as the relative phase between the components of a two-color field varies. A quantum orbit analysis as well as phenomenological considerations in terms of Baz' theory of threshold phenomena are presented in order to describe and explain the major features of threshold phenomena in HHG by a two-color field. Work supported in part by NSF Grant No. PHYS-1505492 (AFS), by Russian Science Foundation Grant No. 15-12-10033 (MVF, TSS, AAS, NVV), and by the Ministry of Education & Science of the Russian Federation Project No. 1019 (NLM).

  17. HARMONIC DRIVE SELECTION

    Directory of Open Access Journals (Sweden)

    Piotr FOLĘGA

    2014-03-01

    Full Text Available The variety of types and sizes currently in production harmonic drive is a problem in their rational choice. Properly selected harmonic drive must meet certain requirements during operation, and achieve the anticipated service life. The paper discusses the problems associated with the selection of the harmonic drive. It also presents the algorithm correct choice of harmonic drive. The main objective of this study was to develop a computer program that allows the correct choice of harmonic drive by developed algorithm.

  18. Harmonics Monitoring Survey on LED Lamps

    OpenAIRE

    Abdelrahman Ahmed Akila; Kamelia Youssef; Ibrahim Yassin

    2017-01-01

    Light Emitting Diode (LED) lamps are being increasingly used in many applications. These LED lamps operate using a driver, which is a switching device. Hence, LED lamps will be a source of harmonics in the power system. These harmonics if not well treated, may cause severe performance and operational problems. In this paper, harmonics (amplitude and phase angles) generated by both LED lamps and conventional fluorescent lamps will be studied practically. Then they will be analyzed and evaluate...

  19. X-ray Production by Cascading Stages of a High-Gain Harmonic Generation Free-Electron Laser II: Special Topics

    Energy Technology Data Exchange (ETDEWEB)

    Wu, J

    2004-09-01

    In this paper, we study the tolerance of a new approach to produce coherent x-ray by cascading several stages of a High-Gain Harmonic Generation (HGHG) Free-Electron Laser (FEL). Being a harmonic generation process, a small noise in the initial fundamental signal will lead to a significant noise-to-signal (NTS) ratio in the final harmonic, so the noise issue is studied in this paper. We study two sources of noise: the incoherent undulator radiation, which is a noise with respect to the seed laser; and the noise of the seed laser itself. In reality, the electron beam longitudinal current profile is not uniform. Since the electron beam is the amplification medium for the FEL, this non- uniformity will induce phase error in the FEL. Therefore, this effect is studied. Phase error due to the wakefield and electron beam self-field is also studied. Synchrotronization of the electron beam and the seed laser is an important issue determining the success of the HGHG. We study the timing jitter induced frequency jitter in this paper. We also show that an HGHG FEL poses a less stringent requirement on the emittance than a SASE FEL does, due to a Natural Emittance Effect Reduction (NEER) mechanism. This NEER mechanism suggests a new operation mode, i.e., the HGHG FEL could adopt a high current, though unavoidable, a high emittance electron beam. Study in this paper shows that, production of hard x-rays with good longitudinal coherence by cascading stages of a HGHG FEL is promising. However, technical improvement is demanded.

  20. 1.5 W green light generation by single-pass second harmonic generation of a single-frequency tapered diode laser

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin; Andersen, Peter E.; Sumpf, Bernd

    2009-01-01

    More than 1.5 W of green light at 531 nm is generated by singlepass second harmonic generation in periodically poled MgO:LiNbO3. The pump laser is a high power tapered laser with a distributed Bragg reflector etched in the ridge section of the laser to provide wavelength selectivity. The output...... power of the single-frequency tapered laser is 9.3 W in continuous wave operation. A conversion efficiency of 18.5 % was achieved in the experiments....

  1. Resonance widths in open microwave cavities studied by harmonic inversion.

    Science.gov (United States)

    Kuhl, U; Höhmann, R; Main, J; Stöckmann, H-J

    2008-06-27

    From the measurement of a reflection spectrum of an open microwave cavity, the poles of the scattering matrix in the complex plane have been determined. The resonances have been extracted by means of the harmonic inversion method. By this, it became possible to resolve the resonances in a regime where the linewidths exceed the mean level spacing up to a factor of 10, a value inaccessible in experiments up to now. The obtained experimental distributions of linewidths were found to be in perfect agreement with predictions from random matrix theory when wall absorption and fluctuations caused by couplings to additional channels are considered.

  2. Resonance widths in open microwave cavities studied by harmonic inversion

    OpenAIRE

    Kuhl, U.; Hoehmann, R.; Main, J; Stoeckmann, H. -J.

    2007-01-01

    From the measurement of a reflection spectrum of an open microwave cavity the poles of the scattering matrix in the complex plane have been determined. The resonances have been extracted by means of the harmonic inversion method. By this it became possible to resolve the resonances in a regime where the line widths exceed the mean level spacing up to a factor of 10, a value inaccessible in experiments up to now. The obtained experimental distributions of line widths were found to be in perfec...

  3. Harmonic generation enhancement due to interaction of few-cycle light pulses in nonlinear dielectric coating on a mirror

    Science.gov (United States)

    Buyanovskaya, Elizaveta M.; Kniazev, Mikhail A.; Kozlov, Sergei A.; Sukhorukov, Andrey A.

    2017-11-01

    We theoretically investigate reflection of a few-cycle light pulse from a mirror with nonlinear dielectric coating. We employ a nonlinear equation that describes spatiotemporal evolution of a few-cycle light pulse with a broad spectrum that lies in the transparency range of nonlinear dielectric media. This model is formulated directly for the electric field without slowly varying amplitude approximation. Analytical and numerical analysis shows that counter-propagating wave interactions in thin films can strongly enhance or suppress third harmonic generation of the central frequency, whereas this effect is neglected in the framework of slowly varying amplitude approximation.

  4. Efficient second harmonic generation in beta-barium borate by a diffraction-limited copper vapor laser.

    Science.gov (United States)

    Pini, R; Salimbeni, R; Toci, G; Vannini, M

    1992-05-20

    The diffraction-limited beam of a copper vapor laser employing a self-filtering unstable resonator was used to induce second harmonic generation in a nonlinear crystal of beta-barium borate. Despite the moderate emission characteristics of our small-scale laser device (1.5-W average power, 25-kW peak power at 511 nm), we obtained average and peak power conversion efficiencies of approximately 20 and 30%, respectively, which improved on the previously reported results by a factor of 2.

  5. Time-dependent complete-active-space self-consistent-field method for atoms: Application to high-harmonic generation

    CERN Document Server

    Sato, Takeshi; Brezinova, Iva; Lackner, Fabian; Nagele, Stefan; Burgdorfer, Joachim

    2016-01-01

    We present the numerical implementation of the time-dependent complete-active-space self-consistent-field (TD-CASSCF) method [Phys. Rev. A, 88, 023402 (2013)] for atoms driven by a strong linearly polarized laser pulse. The present implementation treats the problem in its full dimensionality and introduces a gauge-invariant frozen-core approximation, an efficient evaluation of the Coulomb mean field scaling linearly with the number of basis functions, and a split-operator method specifically designed for stable propagation of stiff spatial derivative operators. We apply this method to high-harmonic generation in helium, beryllium, and neon and explore the role of electron correlations.

  6. Study of 2ω and 3/2ω harmonics in ultrashort high-intensity laser ...

    Indian Academy of Sciences (India)

    is produced by electron plasma wave coupling at the critical density surface of the plasma. The other mechanism of generation of 2ω is when the intense laser field drives a relativistic oscillation of plasma surface, which causes a periodic phase modulation of the reflected light and, hence, the emission of harmonics of the ...

  7. Optimization and phase matching of fiber-laser-driven high-order harmonic generation at high repetition rate.

    Science.gov (United States)

    Cabasse, Amélie; Machinet, Guillaume; Dubrouil, Antoine; Cormier, Eric; Constant, Eric

    2012-11-15

    High-repetition-rate sources are very attractive for high-order harmonic generation (HHG). However, due to their pulse characteristics (low energy, long duration), those systems require a tight focusing geometry to achieve the necessary intensity to generate harmonics. In this Letter, we investigate theoretically and experimentally the optimization of HHG in this geometry, to maximize the extreme UV (XUV) photon flux and improve the conversion efficiency. We analyze the influence of atomic gas media (Ar, Kr, or Xe), gas pressure, and interaction geometries (a gas jet and a finite and a semi-infinite gas cell). Numerical simulations allow us to define optimal conditions for HHG in this tight focusing regime and to observe the signature of on-axis phase matching. These conditions are implemented experimentally using a high-repetition-rate Yb-doped fiber laser system. We achieve optimization of emission with a recorded XUV photon flux of 4.5×10(12) photons/s generated in Xe at 100 kHz repetition rate.

  8. Quantification of collagen fiber organization in biological tissues at cellular and molecular scales using second-harmonic generation imaging

    Science.gov (United States)

    Ambekar Ramachandra Rao, Raghu

    Collagen is the most abundant structural protein found in the human body, and is responsible for providing structure and function to tissues. Collagen molecules organize naturally into structures called fibers on the scale of the wavelength of light and lack inversion symmetry, thus allowing for the process of second harmonic generation (SHG) when exposed to intense incident light. We have developed two quantitative techniques: Fourier transform-second-harmonic generation (FT-SHG) imaging and generalized chi2 second-harmonic generation (chi2-SHG) imaging. In order to show that FT-SHG imaging can be used as a valuable diagnostic tool for real-world biological problems, we first investigate collagenase-induced injury in horse tendons. Clear differences in collagen fiber organization between normal and injured tendon are quantified. In particular, we observe that the regularly oriented organization of collagen fibers in normal tendons is disrupted in injured tendons leading to a more random organization. We also observe that FT-SHG microscopy is more sensitive in assessing tendon injury compared to the conventional polarized light microscopy. The second study includes quantifying collagen fibers in cortical bone using FT-SHG imaging and comparing it with scanning electron microscopy (SEM). Further, as an example study, we show how FT-SHG imaging could be used to quantify changes in bone structure as a function of age. Some initial work and future directions for extending FT-SHG to 3D are also discussed. The second technique, chi2-SHG imaging, takes advantage of the coherent nature of SHG and utilizes polarization to extract the second-order susceptibility (d elements) which provides information on molecular organization, i.e., it provides access to sub-diffractional changes "optically". We use chi2-SHG in combination with FT-SHG imaging to investigate a couple of biological problems. First, we quantify differences in collagen fiber organization between cornea and

  9. Generation of bright circularly-polarized extreme ultraviolet high harmonics for magnetic circular dichroism spectroscopy

    CERN Document Server

    Kfir, Ofer; Turgut, Emrah; Knut, Ronny; Zusin, Dmitriy; Popmintchev, Dimitar; Popmintchev, Tenio; Nembach, Hans; Shaw, Justin M; Fleicher, Avner; Kapteyn, Henry; Murnane, Margaret; Cohen, Oren

    2014-01-01

    Circularly-polarized extreme UV and X-ray radiation provides valuable access to the structural, electronic and magnetic properties of materials. To date, such experiments have been possible only using large-scale free-electron lasers or synchrotrons. Here we demonstrate the first bright extreme UV circularly-polarized high harmonics and use this new light source for magnetic circular dichroism measurements at the M-shell absorption edges of cobalt. This work paves the way towards element-specific imaging and spectroscopy of multiple elements simultaneously in magnetic and other chiral media with very high spatio-temporal resolution, all on a tabletop.

  10. Reactive power compensation considering high harmonics generation from internal and external nonlinear load

    Science.gov (United States)

    Skamyin, A. N.; Belsky, A. A.

    2017-10-01

    The paper deals with reactive power compensation by means of condenser batteries with harmonic distortions in voltage and current, resulting from internal and external nonlinear load regarding the connection point shared by consumers. The paper presents the dependencies of the capacitor’s overloading factor from the required reactive power for compensating. These relations can help to determine in which capacity area of the capacitor banks its operation is ensured without overload. The paper also presents algorithm for selecting parameters of condenser batteries which leads to minimization of the capacitors overload and maximization of the network power factor.

  11. Ultrafast Optical Modulation of Second- and Third-Harmonic Generation from Cut-Disk-Based Metasurfaces

    KAUST Repository

    Sartorello, Giovanni

    2016-06-06

    We design and fabricate a metasurface composed of gold cut-disk resonators that exhibits a strong coherent nonlinear response. We experimentally demonstrate all-optical modulation of both second- and third-harmonic signals on a subpicosecond time scale. Pump-probe experiments and numerical models show that the observed effects are due to the ultrafast response of the electronic excitations in the metal under external illumination. These effects pave the way for the development of novel active nonlinear metasurfaces with controllable and switchable coherent nonlinear response. © 2016 American Chemical Society.

  12. Optical absorption, piezoelectric effect and second harmonic generation studies of single crystal AgGaGe{sub 3}Se{sub 7.6}Te{sub 0.4} solid solution

    Energy Technology Data Exchange (ETDEWEB)

    Myronchuk, G.L.; Krymus, A.S.; Piasecki, M. [Institute of Physics, J. Dlugosz University, Czestochowa (Poland); Eastern European National University, Physics Department, Lutsk (Ukraine); Lakshminarayana, G. [Universiti Putra Malaysia, Wireless and Photonic Networks Research Centre, Faculty of Engineering, Serdang, Selangor (Malaysia); Kityk, I.V. [Czestochowa University of Technology, Faculty of Electrical Engineering, Czestochowa (Poland); Eastern European National University, Physics Department, Lutsk (Ukraine); Parasyuk, O.V. [Eastern European National University, Department of Chemistry, Lutsk (Ukraine); Rudysh, M.Ya.; Shchepanskyi, P.A. [Institute of Physics, J. Dlugosz University, Czestochowa (Poland); Ivan Franko National University of Lviv, Physics Department, Lviv (Ukraine)

    2017-03-15

    Spectral features of absorption were studied for novel AgGaGe{sub 3}Se{sub 7.6}Te{sub 0.4} solid-state alloys at different temperatures. The synthesized crystals structure parameters are obtained by the X-ray Rietveld refinement method. During increasing temperature from 100 up to 300 K, the energy gap of AgGaGe{sub 3}Se{sub 7.6}Te{sub 0.4} decreases linearly from 2.05 up to 1.94 eV at a rate 5.7 x 10{sup -4} eV/K. The magnitudes of piezoelectric coefficients are significantly changed and demonstrate substantial anisotropy. At room temperature, these values are equal to 5.2 pm/V (d{sub 11}), 31.5 pm/V (d{sub 22}) and 35.5 pm/V (d{sub 33}). It is crucial that with an increasing temperature the piezoelectric efficiencies are increased. We have explored temperature and laser-induced changes of piezoelectric coefficients. (orig.)

  13. Efficient second harmonic generation in low-loss planar GaN waveguides.

    Science.gov (United States)

    Gromovyi, Maksym; Brault, Julien; Courville, Aimeric; Rennesson, Stéphanie; Semond, Fabrice; Feuillet, Guy; Baldi, Pascal; Boucaud, Philippe; Duboz, Jean-Yves; De Micheli, Marc P

    2017-09-18

    We demonstrate low-loss GaN/AlGaN planar waveguides grown by molecular beam epitaxy on sapphire substrates. By using a proper AlGaN cladding layer and reducing surface roughness we reach modal phase matching between a TM0 pump at 1260nm and a TM2 second harmonic at 630nm. A maximal power conversion of 2% is realized with an efficiency of 0.15%·W(-1)cm(-2). We provide a modelling that demonstrates broadband features of GaN/AlGaN platform by showing second harmonic wavelengths tunability from the visible up to the near-infrared spectral region. We discuss drawbacks of modal phase matching and propose a novel solution which allows a drastic improvement of modal overlaps with the help of a planar polarity inversion. This new approach is compatible with low propagation losses and may allow as high as 100%·W(-1)cm(-2) conversion efficiencies in the future.

  14. Combining harmonic generation and laser chirping to achieve high spectral density in Compton sources

    Directory of Open Access Journals (Sweden)

    Balša Terzić

    2016-04-01

    Full Text Available Recently various laser-chirping schemes have been investigated with the goal of reducing or eliminating ponderomotive line broadening in Compton or Thomson scattering occurring at high laser intensities. As a next level of detail in the spectrum calculations, we have calculated the line smoothing and broadening expected due to incident beam energy spread within a one-dimensional plane wave model for the incident laser pulse, both for compensated (chirped and unchirped cases. The scattered compensated distributions are treatable analytically within three models for the envelope of the incident laser pulses: Gaussian, Lorentzian, or hyperbolic secant. We use the new results to demonstrate that the laser chirping in Compton sources at high laser intensities: (i enables the use of higher order harmonics, thereby reducing the required electron beam energies; and (ii increases the photon yield in a small frequency band beyond that possible with the fundamental without chirping. This combination of chirping and higher harmonics can lead to substantial savings in the design, construction and operational costs of the new Compton sources. This is of particular importance to the widely popular laser-plasma accelerator based Compton sources, as the improvement in their beam quality enters the regime where chirping is most effective.

  15. Mode pair selection of circumferential guided waves for cumulative second-harmonic generation in a circular tube.

    Science.gov (United States)

    Li, Mingliang; Deng, Mingxi; Gao, Guangjian; Xiang, Yanxun

    2018-01-01

    The appropriate mode pairs of primary and double-frequency circumferential guided waves (CGWs) have been investigated and selected for generation of the cumulative second harmonics, which are applicable for quantitative assessment of damage/degradation in a circular tube. The selection criteria follow the requirements: the higher efficiency of cumulative second-harmonic generation (SHG) of primary CGW propagation, and the larger response sensitivity of cumulative SHG to material damage/degradation [characterized by variation in the third-order elastic (TOE) constants]. The acoustic nonlinearity parameter β of CGW propagation and the change rate of normalized β versus the TOE constants of tube material are, respectively, used to describe the efficiency of SHG and its response sensitivity to damage/degradation. Based on the selection criteria proposed, all the possible mode pairs of primary and double-frequency CGWs satisfying the phase velocity matching have been numerically examined. It has been found that there are indeed some mode pairs of CGW propagation with the larger values both of β and the change rate of normalized β versus the TOE constants. The CGW mode pairs found in this paper are of practical significance for quantitative assessment of damage/degradation in the circular tube. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Noise Analysis of Second-Harmonic Generation in Undoped and MgO-Doped Periodically Poled Lithium Niobate

    Directory of Open Access Journals (Sweden)

    Yong Wang

    2008-01-01

    Full Text Available Noise characteristics of second-harmonic generation (SHG in periodically poled lithium niobate (PPLN using the quasiphase matching (QPM technique are analyzed experimentally. In the experiment, a0.78 μm second-harmonic (SH wave was generated when a 1.56 μm fundamental wave passed through a PPLN crystal (bulk or waveguide. The time-domain and frequency-domain noise characteristics of the fundamental and SH waves were analyzed. By using the pump-probe method, the noise characteristics of SHG were further analyzed when a visible light (532 nm and an infrared light (1090 nm copropagated with the fundamental light, respectively. The noise characterizations were also investigated at different temperatures. It is found that for the bulk and waveguide PPLN crystals, the SH wave has a higher relative noise level than the corresponding fundamental wave. For the same fundamental wave, the SH wave has lower noise in a bulk crystal than in a waveguide, and in MgO-doped PPLN than in undoped PPLN. The 532 nm irradiation can lead to higher noise in PPLN than the 1090 nm irradiation. In addition, increasing temperature of device can alleviate the problem of noise in conjunction with the photorefractive effect incurred by the irradiation light. This is more significant in undoped PPLN than in MgO-doped one.

  17. Second harmonic generation in gallium phosphide microdisks on silicon: from strict \\bar{4} to random quasi-phase matching

    Science.gov (United States)

    Guillemé, P.; Dumeige, Y.; Stodolna, J.; Vallet, M.; Rohel, T.; Létoublon, A.; Cornet, C.; Ponchet, A.; Durand, O.; Léger, Y.

    2017-06-01

    The convergence of nonlinear optical devices and silicon photonics is a key milestone for the practical development of photonic integrated circuits. The associated technological issues often stem from material incompatibility. This is the case of second order nonlinear processes in monolithically integrated III-V semiconductor devices on silicon, where structural defects called antiphase domains strongly impact the optical properties of the material. We theoretically investigate the influence of antiphase domains on second harmonic generation in III-V whispering gallery mode microresonators on silicon and focus on the effects of the antiphase domains’ mean size (i.e. the correlation length of the distribution). We demonstrate that the domain distributions can have opposite effects depending on the nonlinear process under consideration: while antiphase domains negatively impact second harmonic generation under \\bar{4} quasi-phase matching conditions (independent of the correlation length), large conversion efficiencies can arise far from \\bar{4}-quasi-phase matching provided that the APD correlation length remains within an appropriate range, and is still compatible with the spontaneous emergence of such defects in the usual III-V on Si epilayers. Such a build-up can be explained by the occurrence of random quasi-phase matching in the system.

  18. Enhancement in the structure quality of ZnO nanorods by diluted Co dopants: Analyses via optical second harmonic generation

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chung-Wei; Hsiao, Chih-Hung [Institute of Microelectronics and Department of Electrical Engineering, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Chang, Shoou-Jinn [Institute of Microelectronics and Department of Electrical Engineering, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701, Taiwan (China); Brahma, Sanjaya; Chang, Feng Ming [Department of Physics, National Cheng Kung University, Tainan 701, Taiwan (China); Wang, Peng Han [Department of Photonics, National Cheng Kung University, Tainan 701, Taiwan (China); Lo, Kuang-Yao, E-mail: kuanglo@mail.ncku.edu.tw [Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701, Taiwan (China); Department of Physics, National Cheng Kung University, Tainan 701, Taiwan (China)

    2015-02-28

    We report a systematic study about the effect of cobalt concentration in the growth solution over the crystallization, growth, and optical properties of hydrothermally synthesized Zn{sub 1−x}Co{sub x}O [0 ≤ x ≤ 0.40, x is the weight (wt.) % of Co in the growth solution] nanorods. Dilute Co concentration of 1 wt. % in the growth solution enhances the bulk crystal quality of ZnO nanorods, and high wt. % leads to distortion in the ZnO lattice that depresses the crystallization, growth as well as the surface structure quality of ZnO. Although, Co concentration in the growth solution varies from 1 to 40 wt. %, the real doping concentration is limited to 0.28 at. % that is due to the low growth temperature of 80 °C. The enhancement in the crystal quality of ZnO nanorods at dilute Co concentration in the solution is due to the strain relaxation that is significantly higher for ZnO nanorods prepared without, and with high wt. % of Co in the growth solution. Second harmonic generation is used to investigate the net dipole distribution from these coatings, which provides detailed information about bulk and surface structure quality of ZnO nanorods at the same time. High quality ZnO nanorods are fabricated by a low-temperature (80 °C) hydrothermal synthesis method, and no post synthesis treatment is needed for further crystallization. Therefore, this method is advantageous for the growth of high quality ZnO coatings on plastic substrates that may lead toward its application in flexible electronics.

  19. Precise, motion-free polarization control in Second Harmonic Generation microscopy using a liquid crystal modulator in the infinity space.

    Science.gov (United States)

    Lien, Chi-Hsiang; Tilbury, Karissa; Chen, Shean-Jen; Campagnola, Paul J

    2013-01-01

    Second Harmonic Generation (SHG) microscopy coupled with polarization analysis has great potential for use in tissue characterization, as molecular and supramolecular structural details can be extracted. Such measurements are difficult to perform quickly and accurately. Here we present a new method that uses a liquid crystal modulator (LCM) located in the infinity space of a SHG laser scanning microscope that allows the generation of any desired linear or circular polarization state. As the device contains no moving parts, polarization can be rotated accurately and faster than by manual or motorized control. The performance in terms of polarization purity was validated using Stokes vector polarimetry, and found to have minimal residual polarization ellipticity. SHG polarization imaging characteristics were validated against well-characterized specimens having cylindrical and/or linear symmetries. The LCM has a small footprint and can be implemented easily in any standard microscope and is cost effective relative to other technologies.

  20. Parameter Analysis For A High-Gain Harmonic Generation FEL By Numerical Calculation Based On 1D Theory

    CERN Document Server

    Li, Yuhui; Zhang, Shancai

    2004-01-01

    The high-gain harmonic generation (HGHG) free-electron laser (FEL) is an important candidate for a fourth-generation light source. Lots of theoretical work has been performed. Recently a further 1D theory about HGHG FEL has been developed. It considers the effects of different parameters for the whole process. An initial program based on this theory has been made. In this paper, a brief comparison of the results from this 1D program and from TDA (3D code) is discussed. It also analyses the parameters for Shanghai deep ultra violate free-electron laser source (SDUV-FEL), including electron beam energy spread, seed laser power, strength of dispersion section etc.