Showing papers on "High harmonic generation published in 1978"
TL;DR: In this article, a second-harmonic signal at a flat unbonded interface between two solids has been observed, caused by passage of a longitudinal acoustic wave across the interface.
Abstract: The generation of a second‐harmonic signal at a flat unbonded interface between two solids has been observed. This signal is caused by passage of a longitudinal acoustic wave across the interface. The harmonic amplitude depends upon the pressure applied normal to the interface and is largest close to zero pressure, as expected theoretically. The effect has also been used to detect the presence of microcracks on the surface of Al 2024, developed during fatigue.
308 citations
TL;DR: In this article, the third-order polarizabilities were measured in the gas phase using dc electric field induced optical second harmonic generation and were found to be positive in each case.
Abstract: Third‐order polarizabilities are measured in the gas phase using dc electric‐field induced optical second‐ harmonic generation and are found to be positive in each case.
80 citations
TL;DR: In this paper, a second-harmonic signal at a flat unbonded interface between two solids has been observed, caused by passage of a longitudinal acoustic wave across the interface.
Abstract: The generation of a second‐harmonic signal at a flat unbonded interface between two solids has been observed. This signal is caused by passage of a longitudinal acoustic wave across the interface. The harmonic amplitude depends upon the pressure applied normal to the interface and is largest close to zero pressure, as expected theoretically. The effect has also been used to detect the presence of microcracks on the surface of Al 2024, and Al 7075, developed during fatigue with an acoustic Rayleigh wave propagating along the fatigued surface. An alteration of the harmonic amplitude of the alloy has been observed after 5% of the expended fatigue lifetime, corresponding to the formation of microcracks on the alloy surface. The harmonic signal is observed to become progressively stronger as the microcracks propagate with additional fatigue loading. The results are especially encouraging in regard to future use of the technique to measure the remaining fatigue life of a component long before large cracks, detectable with other NDT techniques, develop prior to component failure.
33 citations
TL;DR: In this article, the non-phase matched harmonic generation of surface plasmons has been analyzed using total field solutions which satisfy the nonlinear current driven Maxwell's Equations and electromagnetic boundary conditions.
21 citations
TL;DR: In this paper, the spectrum of the light reflected or refracted at the fundamental laser frequency and its harmonics in CO2 laser-target interaction experiments were studied and the origin of these harmonics was interpreted in terms of instabilities, such as the parametric decay and the 2 plasmons instability, in laser-plasma interaction.
Abstract: 2014 We have studied the spectrum of the light reflected or refracted at the fundamental laser frequency and its harmonics in CO2 laser-target interaction experiments. At the fundamental frequency the spectrum shows a red component which is interpreted as due to Brillouin backscattering; it represents only a small fraction of the backscattered light. The harmonics 2 03C9 and 3/2 03C9 have been observed and their spectrum investigated. The origin of these harmonics is interpreted in term of instabilities, such as the parametric decay and the 2 plasmons instability, in laser-plasma interaction. These harmonics permit us, to determine the local electron temperature and density scale length. LE JOURNAL DE PHYSIQUE LETTRES TOME 39, 1 er JUIN 1978
13 citations
TL;DR: In this article, the saturation of fifth harmonic generation by picosecond laser pulses was investigated experimentally, and it was shown that the saturation was achieved by a focused beam in metal vapour.
Abstract: Fifth order non-linear processes produced by a focused beam in metal vapour have been investigated experimentally. Evidence of saturation of fifth harmonic generation by picosecond laser pulses is reported.
9 citations
TL;DR: In this article, a wave at a particular frequency, which is approximately 0.8 times the Brunt-Vaisala frequency, may play an outstanding role in second-harmonic generation of acoustic gravity waves.
Abstract: We have found that a wave at a particular frequency, which is approximately 0.8 times the Brunt-Vaisala frequency, may play an outstanding role in second-harmonic generation of acoustic gravity waves.
9 citations
8 citations
TL;DR: In this article, the optimum conditions for the third harmonic generation of iodine laser radiation in alkali vapor systems are investigated theoretically, and it is shown that for input intensities above 10 9 W/cm 2 5th order contributions have to be considered.
7 citations
TL;DR: In this paper, the propagation of a second harmonic surface wave in a gas discharge plasma is investigated experimentally, and the results are compared with those obtained for surface waves excited directly.
3 citations
01 Jan 1978
TL;DR: In this paper, the theoretical conversion efficiency for many of these processes is very high, often in the range of pump depletion under conditions typically encountered in experiments, but the measured conversion levels often fall significantly below the theoretical ones, and the variation of conversion efficiency with vapor pressure or pump power may deviate from the simple forms predicted by theory.
Abstract: Optical frequency conversion in atomic and molecular vapors through third, fifth and seventh order nonlinearities has proven to be an important source of coherent radiation in the vacuum ultraviolet (VUV) and extreme ultraviolet (XUV). If only the frequency conversion process is considered, the theoretical conversion efficiency for many of these processes is very high, often in the range of pump depletion under conditions typically encountered in experiments. Measured conversion levels, on the other hand, often fall significantly below the theoretical ones, and the variation of conversion efficiency with vapor pressure or pump power may deviate from the simple forms predicted by theory. Such behavior indicates that additional nonlinear effects are playing a significant role in limiting the conversion efficiency that can be realized in the laboratory.
TL;DR: In this article, the second harmonic of unpolarized laser radiation was generated in a new type of nonlinear converter which performed vector phase matching of orthogonally polarized waves of the fundamental frequency with parallel ray vectors.
Abstract: A method for intracavity generation of the second harmonic of unpolarized laser radiation was devised and tested experimentally. The harmonic was generated in a new type of nonlinear converter which performed vector phase matching of orthogonally polarized waves of the fundamental frequency with parallel ray vectors. This converter was capable of spatial separation of the fundamental and second-harmonic radiation and of increasing considerably the harmonic generation efficiency.
TL;DR: In this paper, a theoretical investigation is made of unsteady quasiresonant optical third-harmonic generation in a gaseous nonlinear medium pumped by amplitude-modulated pulses of constant collimated radiation.
Abstract: A theoretical investigation is made of unsteady quasiresonant optical third-harmonic generation in a gaseous nonlinear medium pumped by amplitude-modulated pulses of constant collimated radiation. It is shown that two effective unsteadiness mechanisms exist: "wave" unsteadiness, associated with the difference between the propagation velocities of the pump and harmonic waves, and "local" unsteadiness caused by the finite relaxation time of the appropriate nonlinear component of the polarization of the medium. In spectral terms these correspond to the resonant dispersion of the phase matching and the dispersion of the nonlinear polarizability of the medium, respectively. The output pulse profile is determined and the influence of the main parameters on its profile is analyzed. The stimulated emission spectrum is also studied for conditions when the pump field is a steady-state random Gaussian process.