Showing papers on "High harmonic generation published in 1984"
TL;DR: In this article, the distortion and harmonic generation in the near field of a finite amplitude sound beam are considered, assuming time-periodic but otherwise arbitrary on-source conditions, and the amplitude and phase of the fundamental and first few harmonics are calculated along the beam axis, and across the beam at various ranges from the source.
Abstract: Distortion and harmonic generation in the nearfield of a finite amplitude sound beam are considered, assuming time‐periodic but otherwise arbitrary on‐source conditions. The basic equations of motion for a lossy fluid are simplified by utilizing the parabolic approximation, and the solution is derived by seeking a Fourier series expansion for the sound pressure. The harmonics are governed by an infinite set of coupled differential equations in the amplitudes, which are truncated and solved numerically. Amplitude and phase of the fundamental and the first few harmonics are calculated along the beam axis, and across the beam at various ranges from the source. Two cases for the source are considered and compared: one with a uniformly excited circular piston, and one with a Gaussian distribution. Various source levels are used, and the calculations are carried out into the shock region. The on‐axis results for the fundamental amplitude are compared with results derived using the linearized solution modified with various taper functions. Apart from a nonlinear tapering of the amplitude along and near the axis, the results are found to be very close to the linearized solution for the fundamental, and for the second harmonic close to what is obtained from a quasilinear theory. The wave profile is calculated at various ranges. An energy equation for each harmonic is obtained, and shown to be equivalent within our approximation to the three‐dimensional version of Westervelt’s energy equation. Recent works on one‐dimensional propagation are reviewed and compared.
267 citations
TL;DR: In this paper, a discussion of second harmonic generation with imperfect phase matching in the high conversion limit is presented, where phase modulation of the fundamental pulse, dispersion, central frequency wavevector mismatch, and fundamental depletion are included.
Abstract: -A discussion of second harmonic generation with imperfect phase matching in the high conversion limit is presented. Phase modulation of the fundamental pulse, dispersion, central frequency wavevector mismatch, and fundamental depletion are included. The results show that even small amounts of phase modulation or central frequency wavevector mismatch can limit harmonic generation and must be considered at high conversion efficiency. Both spatial and temporal phase matching parameters are more restrictive at high conversion efficiency because of the narrowing of the central phase matching peak. If the harmonic conversion process is overdriven, severe distortion of the harmonic and transmitted fundamental pulses can result. Cascade harmonic generation of neodymium laser radiation to 266 nm is presented as an example.
122 citations
TL;DR: In this paper, a detailed investigation of the instabilities in a high-finesse nonlinear ring cavity is presented, where both Ikeda instabilities and bistability are obtained in a rather limited regime of detuning.
Abstract: Instabilities and self-oscillation in systems containing an optical Kerr medium are studied in detail. Nonlinear interactions, both within and without a cavity, are discussed. Instability thresholds and frequencies of self-oscillation are treated as a gain-feedback process. A detailed investigation of the instabilities in a high-finesse nonlinear ring cavity shows that both Ikeda instabilities and bistability are obtained in a rather limited regime of detuning. In most of the detuning range, the system exhibits period-τ oscillations. Counterpropagating waves in a Kerr medium are shown to become unstable above a certain threshold intensity. This results in a system that is equivalent to a Raman-like laser that is being excited in the distributed-feedback structure generated by the two waves. A qualitative description of harmonic generation and period doubling, based on wave-mixing processes, is also presented.
111 citations
TL;DR: In this paper, the results of experiments conducted on a circular jet simultaneously excited by two different acoustic tones were described, showing that by varying the phase between two signals at harmonically related frequencies, control can be exercised on the process of harmonic generation sometimes the process being virtually destroyed.
Abstract: This paper describes the results of experiments conducted on a circular jet simultaneously excited by two different acoustic tones. By varying the phase between two signals at harmonically related frequencies, control can be exercised on the process of harmonic generation sometimes the process being virtually destroyed. This is shown to be so for both harmonic and subharmonic generation, but the latter is more difficult to control.
63 citations
TL;DR: In this paper, the second harmonic of CO2 laser radiation was generated for the first time in ZnGeP2 single crystals under phase-matching conditions when the pump (fundamental-frequency) radiation was tuned within the ranges 9.19 −9.7 and 10.15 −10.8 μ.
Abstract: The second harmonic of CO2 laser radiation was generated for the first time in ZnGeP2 single crystals under phase-matching conditions when the pump (fundamental-frequency) radiation was tuned within the ranges 9.19–9.7 and 10.15–10.8 μ. A study was made of the spectral, angular, and temperature widths of the phase-matching curve, of the dependence of the efficiency of conversion to the second harmonic on the pump wavelength and temperature of a crystal, and of the rate of reduction in the phase-matching angle as a result of heating.
37 citations
TL;DR: Second harmonic generation in inclusion complexes between dimethyl β-cyclodextrin and nitroaniline derivatives having a non-centrosymmetric crystal structure was studied in this paper.
Abstract: Second harmonic generation in inclusion complexes between dimethyl β-cyclodextrin and nitroaniline derivatives having a non-centrosymmetric crystal structure occurs.
35 citations
TL;DR: This paper compares the collimated intensity of the harmonic produced by the roughness-induced plasmon coupling with that produced by specular reflection from the metal surface and predicts that the former intensity is predicted to exceed the latter by as much as 2 orders of magnitude.
Abstract: In this paper, we compute the second harmonic radiation generated at a roughened metal surface which is describable in terms of randomly distributed height and spacing roughness variables. The roughness of the surface allows incident radiation to be coupled to a surface-plasmon mode in the metal at frequency ω that beats with the fundamental field at the same frequency to produce a 2ω field of frequency which radiates from the metal in a narrowly defined direction. Given appropriate rough surface parameters, the latter radiation can in principle serve as a well-collimated coherent source of radiation at the second harmonic frequency. We compare the collimated intensity of the harmonic produced by the roughness-induced plasmon coupling with that produced by specular reflection from the metal surface. The former intensity is predicted to exceed the latter by as much as 2 orders of magnitude.
30 citations
TL;DR: In this article, the propagation of surface acoustic waves in a nonlinear isotropic elastic material is investigated and the effects of heat conduction and viscous internal damping, both assumed small, are included.
Abstract: The propagation of surface acoustic waves in a nonlinear isotropic elastic material is investigated. The effects of heat conduction and viscous internal damping, both assumed small, are included. The method of multiple scales is used to investigate the slow modulation of a wave of arbitrary initial profile and a coupled system of integrodifferential equations is obtained for the variation of the different harmonic constituents. Explicit numerical solutions are obtained for the generation of higher harmonics by an initially sinusoidal wave and for the parametric amplification of a weak signal by a pump wave of twice the frequency.
27 citations
TL;DR: In this article, a hybrid of degenerate parametric downconversion and harmonic generation was shown to squeeze free from sub-poissonian photon statistics, but with the advantage that a coherent reference light beam is available for homodyning.
25 citations
TL;DR: In this paper, the second harmonic radiation in reflection from crystalline GaAs irradiated with 20ps, 530nm laser pulses has been measured for incident laser fluences far exceeding the threshold fluence Fth for permanent reflectivity changes.
Abstract: The emission of second harmonic radiation in reflection from crystalline GaAs irradiated with 20‐ps, 530‐nm laser pulses has been measured for incident laser fluences far exceeding the threshold fluence Fth for permanent reflectivity changes. The results are consistent with the occurrence of surface melting during the laser pulse. Detailed analysis of the second harmonic signals reveals an upper limit of 2 ps for the structural transition associated with the melting of the surface.
24 citations
TL;DR: In this article, a toroidal ACT•1 plasma was examined using electrostatic plate antennas. The harmonic generation, consistent with sheath rectification, is sufficiently strong that the nonlinearly generated harmonic modes themselves decay parametrically.
Abstract: Harmonic generation and parametric decay are examined in a toroidal ACT‐1 plasma using electrostatic plate antennas. The harmonic generation, which is consistent with sheath rectification, is sufficiently strong that the nonlinearly generated harmonic modes themselves decay parametrically. Resonant and nonresonant parametric decay of the second harmonic are observed and compared with uniform pump theory. Resonant decay of lower‐hybrid waves into lower‐hybrid waves and slow ion‐cyclotron waves is seen for the first time. Surprisingly, the decay processes are nonlinearly saturated, indicating absolute instability.
TL;DR: In this paper, the problem of magnetic field generation by a non-uniform laser beam is reconsidered, accounting for relativistic nonlinearities as well as the ponderomotive force.
Abstract: The problem of magnetic field generation by a non-uniform laser beam is reconsidered. Accounting for the relativistic nonlinearities as well as the ponderomotive force, the authors calculate the magnetic field profile generated by a high power laser beam.
TL;DR: In this article, the authors report the observation of enhanced optical second-harmonic generation in transmission that is due to excitation of the fundamental long-range surface-plasmon mode on both surfaces of a thin silver film bounded by a nonlinear X-cut quartz crystal and an index-matched liquid.
Abstract: We report the observation of enhanced optical second-harmonic generation in transmission that is due to excitation of the fundamental long-range surface-plasmon mode on both surfaces of a thin silver film bounded by a nonlinear X-cut quartz crystal and an index-matched liquid. The coherent harmonic generation that is observed leaving the polished side face of the nonlinear crystal is 3 orders of magnitude larger than that generated from a Z-cut quartz crystal in a Maker experiment.
15 Aug 1984
TL;DR: The results of damage threshold measurements made at LLNL using ultraviolet wavelength laser pulses are reviewed in this article, where measurements were made with pulses from a krypton fluoride laser with wavelength of 248 nm and pulse duration of 20 ns and with Nd-glass laser pulses converted to the third harmonic wavelength of 355 nm with duration of 0.6 ns.
Abstract: The results of damage threshold measurements made at LLNL using ultraviolet wavelength laser pulses are reviewed. Measurements were made with pulses from a krypton fluoride laser with wavelength of 248 nm and pulse duration of 20 ns and with Nd-glass laser pulses converted to the third harmonic wavelength of 355 nm with duration of 0.6 ns. Measurements are presented for transparent window materials, crystals for harmonic generation, single layer dielectric films of oxide and fluoride materials and multilayer high reflectivity and antireflective coatings.
TL;DR: In this article, a technique for evaluating combinations of third-order elastic constants of samples which cannot be grown large enough to allow one to make the infinite plane-wave approximation is presented.
Abstract: Harmonic generation of 30‐MHz ultrasonic waves in small solid samples is analyzed to establish a technique for evaluating combinations of third‐order elastic constants of samples which cannot be grown large enough to allow one to make the infinite plane‐wave approximation. Results are reported for CsCdF3 and KZnF3.
TL;DR: In this paper, the properties of microwave Fabry-Perot and ring resonators with second-order dispersive nonlinearity are analyzed and a new mechanism is found leading to multistability, which is quantitatively attributed to well defined soliton modes propagating in the resonator.
Abstract: Nonlinear optical cavities are known to exhibit bistability and multistability. In this letter the properties of microwave Fabry–Perot and ring resonators with second‐order dispersive nonlinearity are analyzed. Experimental results such as multiple‐valued output versus input characteristics, resonance curves, and waveforms are described. On the basis of harmonic and subharmonic generation a new mechanism is found leading to multistability, which is quantitatively attributed to well‐defined soliton modes propagating in the resonator.
TL;DR: In this article, a whole view on the harmonic generation in organ pipes is presented, which consists of three main processes: excitory source spectrum generation by the jet, filtration by inharmonic normal modes of the passive system, and radiation from the pipe ends.
Abstract: A whole view on the harmonic generation in organ pipes is presented. It consists ofelementary processes:(a) excitory source spectrum generation by the jet, (b) filtrationby the inharmonic normal modes of the passive system, and (c) radiation from the pipeends. Lateral jet velocity distribution is responsible for the source spectrum. Filtrationand radiation emphasize the resultant source spectrum. Harmonic generationmechanism is classified into the unsaturated and saturatea regimes, and formulated onthe basis of current-and pressure-drive models. Theoretical consideration deduced:(1) Contribution of the pressure-drive to the harmonic generation is not significant.(2) Harmonic structure and its development in the unsaturated regime are defined bythe matrix of the jet offset and the vector of the jet deflection amplitude.(3) A decisivefactor determining the harmonic structure in the fully saturated regime is the time interval ratio of the jet switching action.
TL;DR: In this paper, a high amplitude electromagnetic wave propagating through a collisional plasma heats the electrons, modulates their collision frequency and generates a third harmonic electromagnetic wave, which is then used for power conversion.
Abstract: A high amplitude electromagnetic wave propagating through a collisional plasma heats the electrons, modulates their collision frequency and generates a third harmonic electromagnetic wave. In the steady state the oscillatory component of electron temperature is electron to ion mass ratio times smaller than the nonoscillatory part. Consequently the harmonic generation efficiency even at very high powers is very small (≲10−5%). In a pulsed operation, when the duration of the pulse is much shorter than the energy relaxation time, the ratio of oscillatory to nonoscillatory components of electron temperature could attain values of the order of unity at high powers and power conversion efficiency of the order of 1% can be obtained.
Proceedings Article•
18 Jun 1984
TL;DR: In this paper, the inorganic nonlinear optical crystal possessing planar ring structure β-BaB2O4 was the first to be found in a planar setting.1
Abstract: β-BaB2O4 was the inorganic nonlinear optical crystal possessing planar ring structure found first in our institute.1 Its space group is R3 with unit cell dimensions a = b = 12.532 A, c = 12.717 A, and 6 formula units in a hexagonal cell.2
19 Jun 1984
TL;DR: In this paper, high spectral brightness excimer lasers have been used to produce extreme ultraviolet radiation (XUV) either by harmonic generation mechanisms or direct multiquantum excitation of appropriate gain media.
Abstract: High spectral brightness excimer lasers have been used to produce extreme ultraviolet radiation (XUV) either by harmonic generation mechanisms or direct multiquantum excitation of appropriate gain media with recent results indicating that the latter method is superior for the generation of short-wavelength radiation.
TL;DR: Electro-optically tuned harmonic generation using Type I KDP inside a plasma-electrode discharge cell and a recently developed transparent plasma electrode to produce a large-aperture switch for multipass laser systems is demonstrated.
Abstract: We have demonstrated electro-optically tuned second-harmonic generation using Type I KDP inside a plasma-electrode discharge cell. An axial voltage of +/-52 kV is required to switch a 1.064-microm beam by conversion to 0.53/microm, in agreement with theory. Electro-optically tuned harmonic generation may be combined with a recently developed transparent plasma electrode to produce a large-aperture switch for multipass laser systems.
TL;DR: In this article, symmetry-forbidden second harmonic generation was studied in the region of phase transition in K2SeO4 and (NH4)2BeF4 and the experimental results were explained under assumption that the unipolar domain-like structure with C2v symmetry appears in the incommensurate phase.
Abstract: Second harmonic generation was studied in the region of phase transition in K2SeO4 and (NH4)2BeF4. Symmetry-forbidden harmonic generation was observed in the incommensurate phases near Tc. The experimental results are explained under assumption that the unipolar domain-like structure with C2v symmetry appears in the incommensurate phase.
TL;DR: In this paper, a ferrite microwave harmonic generator is presented in the form of a rectangular cavity resonator, which is attached to one wall and fills out the whole cross-section of the resonator which has a variable length.
TL;DR: In this paper, the origins of anisotropic second harmonic generation observed in reflection from (111 and (100) faces of crystal Ge and Si were investigated and it was concluded that induced plasmas have no role in the effect and that the mechanism for the nonlinearity is associated with quiescent surface dipolar or bulk quadrupolar effects.
Abstract: We have performed experimental and theoretical studies of the origins of anisotropic second harmonic generation observed in reflection from (111) and (100) faces of crystal Ge and Si. Results, using 25 psec and 20 nsec 1.06 and 0.53 µm pump beams allow us to conclude that induced plasmas have no role in the effect and that the mechanism for the nonlinearity is associated with quiescent surface dipolar or bulk quadrupolar effects. Dispersion in the anisotropic behaviour is presented and the application of anisotropic harmonic generation to structural determinations of Si and Ge during laser annealing will be discussed.
TL;DR: The first clear observation of laser emission in the xuv (below 1040 A) is only a year old as mentioned in this paper, and the selection of lasers emitting in the vuv (wavelengths below 2000 A) was very limited.
Abstract: Coherent sources of vacuum‐ultraviolet and extreme‐ultraviolet radiation are hard to come by. The selection of lasers emitting in the vuv (wavelengths below 2000 A) is very limited, and the first clear observation of laser emission in the xuv (below 1040 A) is only a year old (PHYSICS TODAY, November 1983, page 19).
Journal Article•
TL;DR: In this article, an investigation was made of intracavity generation of the second harmonic in a YAG:Nd3+ laser with active mode locking and it was found that a suitable selection of its parameters could reduce considerably the duration of the harmonic pulses while retaining a fairly high conversion efficiency.
Abstract: An investigation was made of intracavity generation of the second harmonic in a YAG:Nd3+ laser with active mode locking. Quasiperiodic dependences of the second harmonic energy on the phase mismatch in a nonlinear crystal and on the position of this crystal in the resonator were determined experimentally and theoretically. It was found that a laser with intracavity second harmonic generation was a self-consistent system and a suitable selection of its parameters could reduce considerably the duration of the harmonic pulses while retaining a fairly high conversion efficiency.
TL;DR: In this paper, the theoretical extreme value of photon antibunching, characterized by the normalized variance of integrated intensity, is − 1/2, while its practical value in real experiments is about −1/3 for both coherent and chaotic input radiation.
Abstract: Two-photon absorption is treated from the point of view of quantum theory in this paper. Both rigorous and approximate solutions are presented. It is shown that the theoretical extreme value of photon antibunching, characterized by the normalized variance of integrated intensity, is − 1/2, while its practical value in real experiments is about −1/3 for both coherent and chaotic input radiation. In the case of the chaotic input radiation, fully coherent radiation can be obtained in this process. Possibilities for experimental realization of two-photon absorption by means of multiple second harmonic generation in thin nonlinear plates, with the generated second harmonic radiation filtered out, are discussed and some values of nonlinear plate thickness, number of light transits and mean intensity of input radiation are estimated. From the standpoint of the possibilities of detection of statistical properties of the resulting light, classical light fluctuation filtering seems to be more practical than the quantum counterpart.