Correction of polarisation distortions using phase conjugation via stimulated Brillouin scattering

Abstract

A scheme using phase conjugation via stimulated Brillouin scattering in methane gas has been developed for the accurate conjugation of both the polarisation state and the phase of a non-uniformly depolarised laser beam. It incorporates a two-plate tapered light guide with metallic reflecting surfaces which has the property of preserving the linear polarisation of the input light. This scheme has been successfully applied to a Nd:glass amplifier arrangement. The residual birefringence loss of 3% (after a double pass) was found to be independent of pump power to the amplifier even when this was increased to a level sufficient to give a single-pass depolarisation loss of 20%