Comparison between the efficiencies of stimulated Brillouin scattering in opposite directions in a field of complex-conjugate pump beams

An analysis is made of stimulated Brillouin scattering in opposite directions when a nonlinear medium is illuminated from opposite sides by two collimated pump beams having their wavefronts reversed with respect to each other. It is shown experimentally that the scattering efficiencies in both directions are the same only when the wave mismatch is negligible. As the wave mismatch is increased, the scattering efficiency in the direction of propagation of the higherpower pump beam decreases compared with the scattering in the opposite direction. The results are used to predict the operation of four-wave hypersonic reversing mirrors with a wave mismatch.