Influence of thermal self-interaction on the excitation of stimulated Brillouin scattering in absorbing media

It is found that thermal self-defocusing of the exciting beam near its focal constriction is the main factor that increases the stimulated Brillouin scattering threshold in a field of long laser pulses and reduces the fraction of the Stokes wave reproducing the focused pump beam. The universal dependence of the excess over the stimulated Brillouin scattering threshold and the reproduction fraction on the ratio of the laser pulse energy to the critical energy of thermal self-defocusing is determined.