Measurement of the temporal, spatial, and saturation behavior of stimulated Brillouin scattering

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Abstract
The temporal growth rates, spatial behavior, and saturation characteristics of stimulated Brillouin scattering (SBS) occurring in a CO2 laser–gas jet experiment are investigated experimentally by picosecond Thomson scattering of ruby laser light as well as by intensity and spectral measurements of the backscattered light. Exponential temporal growth of the ion acoustic waves was observed and found to have a growth rate in good agreement with theory. Spatial modulations in the ion‐acoustic‐wave amplitude resulting from plasma inhomogeneities were found to limit the backscattered reflectivity to less than 10%. The ion acoustic waves saturate at a fluctuation amplitude of <20%. Ion trapping is shown to account for the observed saturation as well as temporal modulations in the ion‐acoustic‐wave amplitude and sibebands in the backscattered spectra.