Investigation of distortions of the laser pulse profile in multipass amplifiers with a stimulated-Brillouin-scattering mirror

A simple qualitative model of beams focused stimulated Brillouin scattering (SBS), capable of providing a sufficiently accurate description of the Stokes pulse profile, was developed. The characteristics of deformation of a laser pulse during amplification in two-pass and four-pass amplifiers with an SBS mirror were investigated theoretically and experimentally for fully overlapping pulses. The influence of pumping and spontaneous emission was ignored. Approximate formulas were derived for determination of the duration of an output pulse and of its leading edge. The parameters required for the most effective control of the output pulse profile were determined.