LASER HOT-SPOTS AND THE BREAKDOWN OF LINEAR INSTABILITY THEORY WITH APPLICATION TO STIMULATED BRILLOUIN-SCATTERING

Convective instabilities in the strongly damped regime are shown to exhibit essential nonlinear behavior due to laser hot spots when the average laser intensity [I] approaches a critical threshold value I(c). The onset of this nonlinear regime is formally signaled by the divergence of the average convective amplification [A] as [I] --> I(c). An independent hot spot model of random phase plate optics predicts that [A] approximately 1/(I(c) - [I])2. A saturated hot spot model of nonlinear stimulated Brillouin scattering (SBS) predicts a rapid turn on and saturation of SBS reflectivity with laser intensity and optic f/number.