Phase conjugation in multistage stimulated Brillouin scattering

Phase conjugation of radiation in multistage stimulated Brillouin scattering is proposed and implemented. Five reflections with a high (~ 0.95) conjugation parameter for each reflection were achieved experimentally using a three-stage hypersound phase-conjugation system. It was found that as the number of reflections was increased, the pulse developed a spiky time structure. Various systems have been proposed, including a system for obtaining laser beams having their frequency shifted relative to the input radiation by several Stokes shifts and a hypersound four-wave mixing system using reference waves with a large frequency mismatch and various polarization configurations. A system for generating laser beams consisting of two components with parallel wave vectors at frequencies differing by an even number of Stokes shifts was also suggested.