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 ex hibit essential nonlinear behavior due to laser hot spots when the ave rage laser intensity [I] approaches a critical threshold value I(c). T he onset of this nonlinear regime is formally signaled by the divergen ce of the average convective amplification [A] as [I] --> I(c). An ind ependent hot spot model of random phase plate optics predicts that [A] approximately 1/(I(c) - [I])2. A saturated hot spot model of nonlinea r stimulated Brillouin scattering (SBS) predicts a rapid turn on and s aturation of SBS reflectivity with laser intensity and optic f/number.