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Showing papers on "High harmonic generation published in 1974"


Journal ArticleDOI
TL;DR: In this article, the authors developed a consistent theory concerning the generation of a second harmonic when an electromagnetic wave is incident on a weakly inhomogeneous isotropic plasma, and studied the dependence of the effect on plasma temperature.
Abstract: The authors have developed a consistent theory concerning the generation of a second harmonic when an electromagnetic wave is incident on a weakly inhomogeneous isotropic plasma, and have studied the dependence of the effect on plasma temperature. They point out the qualitative difference between the mechanisms of second harmonic generation in cases involving low and high temperatures and indicate the oscillatory nature of the intensity of second-harmonic emission. Attention is drawn to the strong enhancement of the effect when the density profile has inflection or extremum points. The influence of changes in density profile due to the high-frequency pressure of the incident wave on the generation of the second harmonic is discussed. The significance of second-harmonic generation in the laser-power heating problem is also discussed.

55 citations


Journal ArticleDOI
TL;DR: In this paper, the authors made spectral measurements of light scattered at various angles from a laser-produced plasma at the frequency ωL, and at the laser frequency 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L and 10L using a mode-locked Nd:glass laser to produce intensities of 1016 W/cm2 at the target.
Abstract: Spectral measurements of light scattered at various angles from a laser‐produced plasma were made at the laser frequency ωL, and at ωL/2, 3ωL/2, 2ωL, 5ωL/2, and 3ωL using a mode‐locked Nd:glass laser to produce intensities of 1016 W/cm2 at the target. Signals were detected at ωL, 3ωL/2, and 2ωL, and their intensities relative to the incident intensity were determined. Upper bounds were set for the intensities at the other frequencies.

46 citations



Journal ArticleDOI
TL;DR: In this paper, the nonlinear interaction of surface acoustic waves propagating in the same direction has been treated from the rigorous theory of thermoelasticity, and exact expressions for nonlinear volume forces and surface stresses were derived under two separate assumptions.
Abstract: The nonlinear interaction of surface acoustic waves propagating in the same direction has been treated from the rigorous theory of thermoelasticity. Exact expressions were derived for the nonlinear volume forces and surface stresses, and the nonlinear cross sections were calculated under two separate assumptions. First, the work done by the nonlinear forces and surface stresses on a normal‐mode surface wave was evaluated and assumed to be totally converted into surface‐wave energy. In the second approach, a linear analytic solution was formulated which simultaneously satisfies the nonlinear wave equation and maintains a stress‐free boundary condition. Numerical values for the strength of second‐harmonic generation were calculated for 24 materials. The characteristics of nonlinear surface‐wave generation were compared with those of nonlinear bulk‐wave generation and significant differences were found. Coupled amplitude equations were derived to treat the case of multiharmonic generation. Finally, a charact...

41 citations


Journal ArticleDOI
TL;DR: In this article, a tunable parametric oscillator operating near 2 μm was used for second-harmonic generation in a GaAs double-heterostructure waveguide in the region of phase matching.
Abstract: Using a tunable parametric oscillator operating near 2 μm, we have observed second‐harmonic generation in a GaAs double‐heterostructure waveguide in the region of phase matching. The harmonic intensity is strongly peaked when the guide propagation constants of the TE (m=0) fundamental and TM (m=2) harmonic are equal. Away from phase matching, the characteristic effects of strong focusing in the plane of the guide are observed. These are the one‐dimensional analogs of the harmonic generation effects observed using two‐dimensional focused laser beams.

33 citations


Journal ArticleDOI
TL;DR: In this article, phase matched second harmonic and nonlinear Cerenkov radiation in a thin-film waveguide structure consisting of an aluminiumoxide film deposited on a quartz substrate was observed.
Abstract: Phase‐matched second harmonic in the thin‐film and nonlinear Cerenkov radiation in the substrate have both been observed in the uv on a cw basis in a thin‐film waveguide structure consisting of an aluminium‐oxide film deposited on a quartz substrate. A sharp resonance in the second‐harmonic output was observed as the fundamental wavelength was tuned through the phase‐matching point. In contrast, the Cerenkov radiation was found to be broadly and continuously tunable and relatively intense.

31 citations


Journal ArticleDOI
01 Jan 1974
TL;DR: In this article, the experimental conditions were that the junction was dc biased in the supercurrent mode, and that the applied rf-power exceeded a certain threshold value depending on the circuit losses.
Abstract: Experiments on a Josephson junction analog showed a parametric excitation of the plasma resonance. The experimental conditions were that the junction was dc biased in the supercurrent mode, and that the applied rf-power exceeded a certain threshold value depending on the circuit losses. The frequency of the applied rf was approximately twice the plasma frequency. The observed half harmonic generation with big amplitude may be understood from a discussion of the stability properties of the Mathieu differential equation.

8 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated ultrasonic harmonic generation in semiconductors and semimetals where deformation potential coupling is the dominant mechanism in the interaction of ultrasound with the free charge carriers.
Abstract: Ultrasonic harmonic generation is investigated in semiconductors and semimetals where deformation potential coupling is the dominant mechanism in the interaction of ultrasound with the free charge carriers. In extrinsic semiconductors, where one type of carrier dominates the interaction, it is found that the harmonic generation due to deformation potential coupling is much weaker than that due to piezoelectric coupling in a typical piezoclectric semiconductor up to frequencies well into the gigahertz regime. When the minority carriers dominate the interaction or in intrinsic semiconductors and semimetals, harmonic generation due to deformation potential coupling can become comparable to that arising from piezoelectric coupling in a typical piezoelectric semiconductor.

7 citations


Journal ArticleDOI
TL;DR: A simple analysis of ultrasonic harmonic generation in materials with a strain dependent dielectric constant shows that nonlinear acoustic effects in such materials are much stronger than in ordinary piezoelectric semiconductors as mentioned in this paper.

5 citations


Proceedings ArticleDOI
01 Jan 1974

3 citations




Journal ArticleDOI
TL;DR: In this article, a naphthalene crystal has been used to produce Raman laser action at 1·961 eV and the power of this laser is of the order of 60 MW.
Abstract: A naphthalene crystal has been used to produce Raman laser action at 1·961 eV. The power of this laser is of the order of 60 MW. The radiation which corresponds to the first-order Stokes emission (FOSE) has been used for the second harmonic generation (SHG) in a KDP crystal at 3840 + using a simple experimental arrangement. A full moon pattern is observed when the beam is collimated whereas a half-moon shape of the second harmonic has been recorded for a focused laser beam.


Book ChapterDOI
Stephen C. Wallace1
01 Jan 1974
TL;DR: In this article, the authors discuss recent experimental work and relevant basic physical principles of both vacuum ultra-violet lasers and harmonic generation into the vacuum ultraviolet, utilizing visible wavelength lasers.
Abstract: Remarkable progress has been made in the past few years in the development of sources of coherent light in the vacuum ultraviolet spectral region. This review will discuss recent experimental work and relevant basic physical principles of both vacuum ultra-violet lasers and harmonic generation into the vacuum ultraviolet, utilizing visible wavelength lasers. In exciting electronic transitions which would be made to lase in the vacuum ultra-violet, two problems immediately arise. The first is the severe frequency dependence of the pumping power required to attain significant inversion densities, and hence optical gain at these short wavelengths. For example, with a Doppler broadened line, simple considerations based on the Schawlow-Townes equations show that the pump power necessary to achieve some arbitrary gain scales as ν4. The second difficulty has been more of an operational problem, that of finding a pumping source capable of efficiently exciting electronic levels above 7 eV.

Journal ArticleDOI
TL;DR: In this article, a high-resistivity silicon semiconductor coupled to acoustic surface waves propagating on a YZ lithium niobate substrate is used to convert an optical image into an electrical signal.
Abstract: Conversion of an optical image into an electrical signal is obtained by means of a harmonic generation process. The device consists of a high‐resistivity silicon semiconductor coupled to acoustic surface waves propagating on a YZ lithium niobate substrate.

Journal ArticleDOI
J. Noolandi1
TL;DR: In this article, the effect of the input shear wave with a dynamical strain created by the structural phase transition was analyzed in terms of the interaction of the shear waves with a dynamic strain.
Abstract: In reference to an experiment by L.R. Testardi on V/sub 3/Si, the large effect is interpreted in terms of the interaction of the input shear wave with a dynamical strain created by the structural phase transition. 9 refs.

Journal ArticleDOI
TL;DR: In this paper, the authors extended the work of previous authors on harmonic generation by means of an ideal three-terminal deviec controlling the flow of either a.c. or d.c through a resistive one-port is extended to the consideration of the practical situation of a biased dovice generating high-order harmonic power from both input and output.
Abstract: The work of previous authors on harmonic generation by means of an ideal three–terminal deviec controlling the flow of either a.c. or d.c. through a resistive one–port IS extended to the consideration of the practical situation of a biased dovice generating high–order harmonic power from both a.c. input and d.c, supply. The two possible circuit configurations, shunt and series, are analysed and predictions made of optimum efficiency and terminating conditions. Good agreement is demonstrated between theoretical results and the measured performance of a typical circuit realization using an FET.

Journal ArticleDOI
TL;DR: Pulse broadening and harmonic generation by a photoconductor light detector under the usual experimental conditions are shown to be noticeable even for a fast detector with a perfectly linear light power-conductance characteristic as mentioned in this paper.
Abstract: Pulse broadening and harmonic generation by a photoconductor light detector under the usual experimental conditions are shown to be noticeable even for a fast detector with a perfectly linear light power-conductance characteristic.


Journal ArticleDOI
TL;DR: Theoretical study of plasma nonlinearity effects that cannot be described by modified linear theory, such as those effects that arise only when a source of disturbances in a plasma reaches a certain threshold amplitude, is investigated in this article.
Abstract: Theoretical study of plasma nonlinearity effects that cannot be described by modified linear theory, such, for example, as those effects that arise only when a source of disturbances in a plasma reaches a certain threshold amplitude. In particular, the possibility of fractional harmonic generation, independently of the requirements of the plasma wave decay, is investigated.

Journal ArticleDOI
TL;DR: Using a parabolic approximation for the propagation index of the electric field around the existing minimum of the upper hybrid curve, a closed and finite expression for the value of the peak energy radiated to infinity from the second harmonic generation in the hybrid layer is given and compared with the ST tokamak experiment.
Abstract: Using a parabolic approximation for the propagation index of the electric field around the existing minimum of the upper hybrid curve, a closed and finite expression for the value of the peak energy radiated to infinity from the second harmonic generation in the hybrid layer is given and compared with the ST tokamak experiment. This calculation shows reasonable agreement with the observed value, indicating that in this case the peak is probably due to the second harmonic generation.


Proceedings ArticleDOI
01 Mar 1974
TL;DR: An extensive literature exists concerning the phenomena that occur when laser radiation interacts with solids or fluids as discussed by the authors, and the nature of the interaction depends greatly on the optical, mechanical, and thermal properties of these materials.
Abstract: An extensive literature exists concerning the phenomena that occur when laser radiation interacts with solids or fluids. The nature of the interaction depends greatly on the optical, mechanical, and thermal properties of these materials. There can be such things as plasma generation if the radiation is absorbed in short distances or nonlinear optical behavior leading to "filamenting, " "banana peeling, " or harmonic generation in the more transparent materials (Ref. 1, 2).© (1974) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.