Stimulated Raman and Brillouin Scattering: Parametric-Instability Explanation of Anomalies

The Raman and Brillouin processes have important sharp-threshold parametric instabilities that afford explanations of long-standing anomalies in stimulated-scattering and self-focusing experiments. Below the threshold intensity Ic, the gain is nonexponential and greater than that of previous theories of stimulated scattering, and at the threshold the Stokes intensity increases nearly discontinuously. Typically, Ic~10⁹ W/cm² for a number of gases, liquids, and solids. The theoretical results agree well with previous experimental results.