Eeect of the Speckle Self-focusing on the Stationary Sbs Reeectivity from a Randomized Laser Beam in an Inhomogeneous Plasma Typeset Using Revt E X 1

The eeect of laser light self-focusing (SF) in speckles on stimulated Brillouin scattering (SBS) in an inhomogeneous plasma is studied. It is found that below but near critical power SF dramatically enhances the SBS reeectivity from an individual speckle, while above the critical power the pump power depletion due to SBS prevents strong SF and limits the maximum laser intensity in a speckle. The parameters that control the SBS/SF interplay are the ratio of plasma inhomogeneity scale length to the speckle length and the product of the plasma density and the speckle cross-section. The consequences of the SF eeect on the averaged SBS reeectivity of the randomized laser beam are revealed and their manifestations in recent SBS experiments with preformed plasmas are discussed.