Showing papers on "High harmonic generation published in 1983"
TL;DR: In this paper, a nonlinear theory correct to second order for steps of infinite and finite lengths subjected to single harmonic waves is presented, and boundary value problem for the second-order scattered velocity potential is linearly decomposed into two separate boundary value problems, each having only one inhomogeneous boundary condition.
102 citations
TL;DR: In this article, a Burgers' equation is used to derive an algorithm for calculating harmonic generation by a continuous plane wave of ultrasound propagating in a nonlinear, lossy, non-invariant medium.
Abstract: A form of Burgers’ equation is used to derive an algorithm for calculating harmonic generation by a continuous plane wave of ultrasound propagating in a nonlinear, lossy, nondispersive medium. The algorithm accounts for attenuation that is not quadratically related to the frequency of the wave. Attenuation strongly affects the rate of harmonic production. The effect of variations of the relationship between attenuation and frequency is shown. Biological tissue is an example of a highly lossy medium where the attenuation does not increase with the square of the frequency. Calculations for several types of tissue and biological fluids are presented that show, for certain conditions, finite amplitude distortion is possible.
84 citations
TL;DR: The observation of coherent backscattering of optical second-harmonic generation that is due to excitation of the long-range surface plasmon mode at a silver-quartz interface with a peak-to-background ratio of greater than 2 is seen.
Abstract: The first observation of enhanced optical second-harmonic generation due to excitation of the long-range surface plasmon is reported. When the fundamental mode of this plasmon is excited on both surfaces of a thin silver film bounded by a nonlinear quartz crystal and an index-matched liquid, the harmonic generation is over 2 orders of magnitude larger than that due to a single-boundary surface plasmon. Nonlinear excitation of the harmonic long-range surface-plasmon mode is also observed.
83 citations
TL;DR: In this article, the strongly nonlinear electron response to a time-dependent inhomogeneous force is studied and the equation of the electron motion in Lagrangian variables is derived and conditions on the density scale length and power intensities for wavebreaking are found.
Abstract: It has been observed experimentally that the CO2‐laser Gemini and Helios systems generate very high harmonics with nearly constant efficiency over several harmonics with a cutoff near the local plasma frequency at the upper density shelf. To understand the experimental results, the strongly nonlinear electron response to a time‐dependent inhomogeneous force is studied. The equation of the electron motion in Lagrangian variables is derived and the conditions on the density scale length and power intensities for wavebreaking are found. By transforming the solution back to Eulerian variables, it is shown that the source of a given high harmonic frequency is localized around the density region where the local plasma wave is at that frequency. Using the numerically obtained nonlinear current density we evaluate the intensity of the radiation coming out of the plasma and verify the nearly constant harmonic production efficiency with a sharp decrease at the local plasma wave frequency at the upper shelf density.
55 citations
48 citations
TL;DR: In this article, it was shown that the harmonic generation process minimizes quantum fluctuations of the electromagnetic field in the fundamental as well as in every generated beam, and that the squeezing is dependent on the polarisation properties of both beams.
38 citations
TL;DR: A simple dichroic beam splitter capable of separating extreme-ultraviolet (XUV) radiation from high-powered visible and UV laser beams is demonstrated, applicable to laser-generated XUV radiation sources, including harmonic generation, sum-frequency mixing, and anti-Stokes Raman scattering.
Abstract: A simple dichroic beam splitter capable of separating extreme-ultraviolet (XUV) radiation from high-powered visible and UV laser beams is demonstrated. The device has high XUV reflection efficiency (R approximately 44%) and high damage resistance to intense laser radiation and is therefore applicable to laser-generated XUV radiation sources, including harmonic generation, sum-frequency mixing, and anti-Stokes Raman scattering.
37 citations
TL;DR: In this paper, the free electron laser instability is investigated theoretically for a tenuous relativistic electron beam propagating parallel to a longitudinal wiggler field (B0+δB sin k0z).
Abstract: The free electron laser instability is investigated theoretically for a tenuous relativistic electron beam propagating parallel to a longitudinal wiggler field (B0+δB sin k0z)ez . The stability analysis is based on the linearized Vlasov–Maxwell equations for perturbations about the beam equilibrium f0b =(nb/2πp⊥)δ(p⊥−γbmV⊥) δ(pz−γbmVb). For (ωcb/k0Vb)(δB/B0) of order unity or larger, it is found that the transverse electron orbits experience a strong temporal modulation at harmonics of k0vz≂k0Vb. In the stability analysis, this orbit modulation is manifest by radiation amplification occurring near the simultaneous zeroes of ω=kc and ω−kVb−ωcb=nk0Vb for the general harmonic number n, which corresponds to an upshifted (for n≥1) wavenumber kn=(1−Vb/c)−1(ωcb/c+nk0Vb/c). For (ωcb/k0Vb)(δB/B0) >1, the instability is typically broadband with several harmonics excited. Moreover, depending on beam and field parameters, the characteristic maximum growth rate can be substantial with Im ω/ck0=(3/2)1/2 ×[(V2⊥/4c2)(ω...
30 citations
TL;DR: In this paper, it was shown experimentally and theoretically that only odd harmonics are generated for the ring oscillators with an odd number of stages, and the propagation delay tpd of the nth harmonic oscillation is given byt_{pd} = n \\cdot T/2N whereTis the observed repetition period andNthe number of stage.
Abstract: Harmonic generation is found with 101-stage ring oscillators. Harmonics have not been observed for the usual ring oscillators with a small number of stages. If one mistakes the higher harmonic generation for the fundamental, he obtains a wrong propagation delay which is shorter than the real one. It is shown experimentally and theoretically that only odd harmonics are generated for the ring oscillators with an odd number of stages. The propagation delay tpdof the nth harmonic oscillation is given byt_{pd} = n \\cdot T/2NwhereTis the observed repetition period andNthe number of stages. Computer simulation shows that a ring oscillator with an even number of stages can also oscillate if every inverter is the same, and that the oscillation decays if there is asymmetry in the inverter chain. IfNis large and the effects of the deviations of the transistor parameters cancel one another, the harmonic oscillation that happens to be generated can continue.
25 citations
TL;DR: In this article, the authors theoretically study intensity saturation effects in resonant harmonic generation and multiphoton ionization and derive a set of equations for the density matrix of the gaseous medium and the electromagnetic field within a semiclassical framework.
Abstract: We theoretically study intensity-saturation effects in resonant harmonic generation and multiphoton ionization. A first laser excites a two-photon resonance which is coupled by a second laser to an autoionizing state. Starting from an effective Hamiltonian for the three resonant atomic states, we derive a set of equations for the density matrix of the gaseous medium and the electromagnetic field within a semiclassical framework. We present and discuss analytical and numerical solutions of these equations which show a variety of line profiles depending critically on the intensities of the incident laser pulses.
20 citations
TL;DR: In this article, the diode bias dependence of the rectified signals at 30, 88, and 118 THz (CO2, He−Ne, color center laser) is found to correspond to the dc characteristics in both cases.
Abstract: Different current‐voltage characteristics were found for diodes with Ni and Nb substrates. The diode bias dependence of the rectified signals at 30, 88, and 118 THz (CO2, He‐Ne, color‐center laser) is found to correspond to the dc characteristics in both cases. Harmonic mixing between CO2 and He‐Ne laser, CO2 and color‐center laser respectively, was obtained for one of these characteristics only.
TL;DR: In this paper, the half-integer (3/2ω0, 1/2ó0) harmonics generation under oblique incidence of the pump-wave on the spatially inhomogeneous plasma is theoretically investigated.
Abstract: Half integer (3/2ω0, 1/2ω0) harmonics generation under oblique incidence of the pump-wave on the spatially inhomogeneous plasma is theoretically investigated. Harmonics generation is connected with the two-plasmon convective instability excitation near the quarter-critical density. Harmonics spectra and intensities depend essentially on the pump wave polarization. In particular, significant harmonics spectra broadening arises under the p-polarized pump wave.
30 Nov 1983
TL;DR: In this paper, the authors demonstrate that small, (tunable) integrated optical frequency converters can be fabricated using medium and low power (semiconductor) lasers as pump sources.
Abstract: Nonlinear optical effects as second harmonic and difference frequency generation, parametric amplification and oscillation are studied to achieve efficient frequency conversion in optical waveguide structures. Our experiments with low loss Ti:LiNbO3 optical wave-guides and waveguide resonators are shortly reviewed. The results demonstrate that small, (tunable) integrated optical frequency converters can be fabricated using medium and low power (semiconductor) lasers as pump sources.
01 Jan 1983
TL;DR: In this paper, the propagation of two collinear initially sinusoidal ultrasonic waves of different frequencies is shown to generate a new wave having a frequency equal to the difference of the drive frequencies.
Abstract: The propagation of two collinear initially sinusoidal ultrasonic waves of different frequencies is shown to generate a new wave having a frequency equal to the difference of the collinear drive frequencies. The generated wave results from the n onlinearity of the propagation medium and has an amplitude proportional to the acoustic nonlinearity parameter 6. Values of 6 for fused quartz and for three aluminum alloys have been measured using this collinear beammixing phenomenon and compared 6 values o btained using the harmonic generation technique. The 8 value for fused quartz using beamlnixing agrees to within 1.2% of that using harmonic generation while comparative measurements for the aluminum alloy d iffer in the worst case by 9.3%. The greater d ifference for the aluminum alloys is attributed to the greater u ltrasonic a ttenuation in those materials. The overall v ariation in 8 for all samples measured using either technique is of the order 32%. This variation is attributed to differences in microstructure and alloying of the materials .
TL;DR: In this paper, the zero-field and field-induced optical second harmonic generation (SHG) was investigated for the nematic and smectic A phases of various liquid crystals.
Abstract: The zero-field and field-induced optical second harmonic generation (SHG) was investigated for the nematic and smectic A phases of various liquid crystals. The components of the cubic non-linear susceptibility tensor were measured for substances with different molecular structure. The phase-matched SHG was observed for all the compounds investigated. The directions of the phase synchronisms as well as the corresponding non-linear susceptibilities were determined for the ee-o and oe-o interactions. The zero-field phase-matched SHG was observed for the oe-o interaction. It was accounted for by a multipolar mechanism.
TL;DR: In this article, high-power coherent radiation at 263 nm and 219 nm was generated by converting iodine laser pulses (λ = 1.315 μm) into fifth and sixth-harmonic radiation.
TL;DR: In this article, the coupling coefficients for the nonresonant interaction of two high-frequency surface waves propagating along a plasma column bounded by vacuum are derived directly by solving the equations of the one-fluid cold collisionless/collisional plasma model.
Abstract: Coupled-mode equations for the nonresonant interaction of two high-frequency surface waves, propagating along a plasma column bounded by vacuum, are derived directly by solving the equations of the one-fluid cold collisionless/collisional plasma model. The coupling coefficients are obtained in explicit form. The results are verified by analysing the simple case of harmonic generation by a high amplitude wave. The theory is extended to three-wave interaction in loss plasma in the general case of imperfect synchronism.
TL;DR: In this article, a transverse optical klystron was used to produce short intense and highly coherent pulses of light in the 500 A and even the 100 A range. But it is not suitable for high-power applications.
TL;DR: In this paper, the energy modulation and output characteristics of a transverse optical klystron harmonic generator are expressed for an arbitrary form of the two undulators, as a function of their spontaneous spectra.
Abstract: The energy modulation and output characteristics of a "transverse optical klystron" harmonic generator are expressed for an arbitrary form of the two undulators, as a function of their spontaneous spectra.
TL;DR: In this paper, a photovoltaic grating written in LiNbO3 was used to induce the second harmonic induced by photoruminous grating, and phase matching condition was achieved by a suitable choice of the grating period.
Abstract: Optical second harmonic induced by photovoltaic grating written in LiNbO3:Fe was observed Harmonic generation was due to the third-order nonlinear coefficient f3333 linearized in the electric field of the grating The phase matching condition was achieved by a suitable choice of the grating period
TL;DR: The purpose of this letter is to describe the collabration between Lawrence Livermore National Laboratory and the University of Rochester the subject of harmonic generation of laser radiation for inertial confinement fusion researh.
Abstract: The purpose of this letter is to describe the collabration between Lawrence Livermore National Laboratory and the University of Rochester the subject of harmonic generation of laser radiation for inertial confinement fusion researh. (AIP)
TL;DR: In this article, a study of the generation of a giant second harmonic and of the giant Raman scattering of light on a surface separating a solid from an electrolyte is made, and the intensity of the second harmonic is shown to depend on the electrolyte composition, nature of the solvent, and presence of additives in the form of organic compounds.
Abstract: A study is made of the generation of a giant second harmonic and of the giant Raman scattering of light on a surface separating a solid from an electrolyte. The intensity of the giant second harmonic is shown to depend on the electrolyte composition, nature of the solvent, and presence of additives in the form of organic compounds. An electric field in a double layer may alter the nonlinear optical susceptibilities of the components of the double layer. Generation of a giant second harmonic may provide a convenient method for telemonitoring of the surfaces of metals and semiconductors (for example, for the determination of the zero charge potential) in technological processes. The gain of the second harmonic generation process is (3–5)×104, which is of the same order as the gain of the giant Raman scattering, (5–10)×104, which depends reversibly on the electrode potential , suggesting a common mechanism of these phenomena: an increase in the local field near projections of the surface of a metal.
TL;DR: In this paper, the process of recrystallization of the surface of GaAs during pulsed laser annealing was investigated using generation (by reflection from the surface) of the second harmonic of mode-locked radiation from another laser.
Abstract: The process of recrystallization of the surface of GaAs during pulsed laser annealing was investigated using generation (by reflection from the surface) of the second harmonic of mode-locked radiation from another laser. The recrystallization time did not exceed 30–40 nsec. The results were accounted for by the melting theory of laser annealing.
Journal Article•
TL;DR: In this article, the emission intensity of a pump beam was found to depend on the harmonic index in a power-law fashion, in agreement with experiment, and the generation of higher harmonics of the pump beam by a mechanism involving a breaking of an electron wave was analyzed.
Abstract: The generation of higher harmonics of a pump beam by a mechanism involving a breaking of an electron wave is analyzed. The emission intensity is found to depend on the harmonic index in a power-law fashion, in agreement with experiment.
TL;DR: In this paper, a direct numerical solution of reduced equations is used to study theoretically second harmonic generation in nonlinear crystals in the case of strong energy exchange, and it is shown that transformation of single-mode radiation in crystals with critical phase matching is not very inferior in respect of the conversion efficiency to that in crystal with 90° phase matching, and that displacement of an extraordinary wave relative to an ordinary one prevents the reverse energy conversion.
Abstract: A direct numerical solution of reduced equations is used to study theoretically second harmonic generation in nonlinear crystals in the case of strong energy exchange. An allowance is made for the aperture effects and for diffraction. It is shown that transformation of single-mode radiation in crystals with critical phase matching is not very inferior in respect of the conversion efficiency to that in crystals with 90° phase matching, and that displacement of an extraordinary wave relative to an ordinary one prevents the reverse energy conversion. It is shown that in the case of a strong energy exchange in crystals with critical phase matching the efficiency of second harmonic generation decreases strongly even in the presence of slight spatial distortions in a transverse cross section of the fundamental-frequency beam.
TL;DR: The performance of an intracavity mode-locked and frequency-doubled Nd:YAG laser has been analyzed using a method that takes into account the transverse spatial variation of both the gain and the laser mode.
Abstract: The performance of an intracavity mode-locked and frequency-doubled Nd:YAG laser has been analyzed using a method that takes into account the transverse spatial variation of both the gain and the laser mode. The technique leads to a simple numerical procedure that determines the second harmonic power and pulse width in terms of the parameters that characterize the various spatial distributions.
TL;DR: In this article, a generalized version of the linear acceleration mechanism for emission of radiation is presented, which facilitates harmonic generation and includes the effects due to the relaxation of the dipole-approximation.
Abstract: A generalized version of the linear (or parallel) acceleration mechanism for emission of radiation is presented. This facilitates harmonic generation and includes the effects due to the relaxation of the dipole-approximation. The results are applied to the solar radio bursts of type III and IIIb.
01 Mar 1983
TL;DR: In this paper, the nonlinearity in the currentvoltage characteristics of a ballistic diode was studied for a GaAs sample of thickness 1 µm at 77 K under collision-free condition.
Abstract: Harmonics produced by the nonlinearity in the current-voltage characteristics of a ballistic diode are studied for a GaAs sample of thickness 1 µm at 77 K under collision-free condition Harmonic generation is found to be maximum at zero bias, the value for the second-harmonic current being 50 percent for a signal amplitude of 02 V