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Title: Transient effects on stimulated Brillouin scattering

Abstract

We present a detailed comparison of theory and experiment for transient stimulated Brillouin scattering for a pump pulse with Gaussian temporal profile. A new approach for measuring Brillouin linewidths is demonstrated, and an unexplained asymmetry is observed.

Authors:
; ;  [1]
  1. (Molecular Physics Laboratory, SRI International, Menlo Park, California 94025 (United States))
Publication Date:
OSTI Identifier:
7279683
Resource Type:
Journal Article
Resource Relation:
Journal Name: Optics Letters; (United States); Journal Volume: 17:15
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; GADOLINIUM COMPOUNDS; BRILLOUIN EFFECT; GALLIUM OXIDES; FERRITE GARNETS; GAIN; LASER RADIATION; TRANSIENTS; AMPLIFICATION; CHALCOGENIDES; COHERENT SCATTERING; ELECTROMAGNETIC RADIATION; GALLIUM COMPOUNDS; MINERALS; OXIDE MINERALS; OXIDES; OXYGEN COMPOUNDS; RADIATIONS; RARE EARTH COMPOUNDS; SCATTERING; SILICATE MINERALS; 360606* - Other Materials- Physical Properties- (1992-)

Citation Formats

Faris, G.W., Dyer, M.J., and Hickman, A.P. Transient effects on stimulated Brillouin scattering. United States: N. p., 1992. Web. doi:10.1364/OL.17.001049.
Faris, G.W., Dyer, M.J., & Hickman, A.P. Transient effects on stimulated Brillouin scattering. United States. doi:10.1364/OL.17.001049.
Faris, G.W., Dyer, M.J., and Hickman, A.P. 1992. "Transient effects on stimulated Brillouin scattering". United States. doi:10.1364/OL.17.001049.
@article{osti_7279683,
title = {Transient effects on stimulated Brillouin scattering},
author = {Faris, G.W. and Dyer, M.J. and Hickman, A.P.},
abstractNote = {We present a detailed comparison of theory and experiment for transient stimulated Brillouin scattering for a pump pulse with Gaussian temporal profile. A new approach for measuring Brillouin linewidths is demonstrated, and an unexplained asymmetry is observed.},
doi = {10.1364/OL.17.001049},
journal = {Optics Letters; (United States)},
number = ,
volume = 17:15,
place = {United States},
year = 1992,
month = 8
}
  • A theory of the excitation of ultrasound waves arising from photoelastic coupling with light is presented in this article. Using several reasonable approximations, a numerical calculation of the transient stimulated Brillouin scattering process shows that a large amplitude of acoustic wave can be built up during the pulse of pump light, and it may result in damage to optical materials. This model gives a damage threshold value of {approximately}30{endash}50 J/cm{sup 2} when using Gaussian or square nanosecond pulses on optical materials. {copyright} {ital 1997 American Institute of Physics.}
  • The excitation and the relaxation of the plasma waves and ion acoustic waves (IAW), respectively, driven by stimulated Raman (SRS) and Brillouin (SBS) backscatterings have been experimentally investigated with short-pulse lasers. The spectra have been obtained with a 0.3 ps time resolution. It is shown that SRS develops before SBS and suddenly decays around the peak of the pump, as the IAW reaches saturation. On this short time scale, electron kinetic effects play a major role for SRS saturation, contrary to ion dynamics. These results are supported by particle-in-cell simulations.
  • The effects of anisotropic ion-wave damping in stimulated Brillouin scattering, including rescattering, are investigated. Anisotropy is shown to reduce substantially the limiting (infinite plasma) reflection even at modest levels of ..beta..=..nu../sub +//..nu../sub -/, the ratio of the ion-wave-damping rates.
  • The effects of beam smoothing on the stimulated Brillouin and Raman backscattering instabilities (SBBS and SRBS) in a long scale length exploding foil plasma are experimentally investigated using the Nova laser. We observe strongly time-dependent and blueshifted SBS emission and broadband SRS emission in time-resolved spectral measurements of the backscattered light. The results of this paper focus on the SBS scattering, where we find that random phase plate spatial beam smoothing leads to a decrease in the total SBS reflectivity. Adding temporal smoothing to this spatial smoothing leads to an even greater decrease in the total reflectivity, as well asmore » changes in the spectral nature of the backscattered light. Beam smoothing induced changes to the instabilities are limited to plasmas with a peak density below about 0.2{ital n}{sub cr}; beam smoothing causes little change in the backscattered emission for higher densities. We describe the measurements and discuss models that may explain certain aspects of the results. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.« less
  • Two important effects of long wavelength velocity and density perturbations on stimulated Brillouin scattering (SBS) have been identified: (i) nonlinear interaction of the SBS-produced ion acoustic wave with velocity perturbations provides detuning of the SBS interaction, formation of ion acoustic wave satellites and its additional damping; (ii) harmonic generation of long wavelength density perturbations enhances the spectral density of ion acoustic fluctuations over a wide range of wavevectors, including SBS resonant sound waves. The first effect reduces the magnitude of the SBS gain, and the second one enhances the nonthermal noise level for SBS. Long wavelength ion acoustic perturbations reducemore » SBS reflectivity more dramatically than short wavelength harmonics produced by the SBS driven nonlinear sound wave. {copyright} {ital 1996 American Institute of Physics.}« less