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

Abstract

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 $I_c$, 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, $I_c\sim {10}^9$ W/c${\mathrm{m}}^2$ for a number of gases, liquids, and solids. The theoretical results agree well with previous experimental results.