Conjugate wave phase unstability at stimulated scattering

An experimental determination of the phase fluctuations of the conjugated wave during Stimulated Brillouin Scattering (SBS) is reported, along with measurements of the spectral width. Cross-beating of two Stokes waves generated in optically isolated liquids were converted into current fluctuations, which showed only phase instabilities. SBS was caused by a beam from a single mode Nd-glass laser being split and directed with mirrors to pass through cells filled with carbon tetrachloride or acetone, and Brillouin waves were backscattered to the photodetectors. SBS occurred in the saturation regime with Stabilized Stokes light with the temperature of the liquids maintained close to constant. The spectral lines were assumed Gaussian in distribution, and line width of the Gaussian spectral density of the photocurrent fluctuations was determined. The instability duration was found to be the reciprocal value of the spontaneous scattering linewidth.