Gain homogenization apparatus and method for use in stimulated scattering of beams with non-uniform spatial intensity distribution

An amplifier for amplifying an optical seed beam by a pump beam that is characterized by a spatially non-uniform optical intensity distribution, comprising:

• a medium for optical amplification by stimulated scattering,
• focusing means comprising at least a pair of cylindrical lenses located near an input side of said optical amplification medium for coupling said pump beam into said medium, said focusing means establishing a plurality of mutually spaced foci of said pump beam within said medium that are oriented at dissimilar angles and produce a mixing of said pump beam within said amplification medium, and
• means for coupling said seed beam into said medium in a directed propagation to traverse said mixed pump beam and receive a transfer of energy from said pump beam along a length of said optical amplification medium, said focusing means mixing the pump beam so that the integrated amplification imparted to different portions of said seed beam over its traversal of said mixed pump beam is generally spatially independent of the location of said portions across said seed beam, the local Spatial optical amplification pattern imparted to said seed beam differs for different locations along its traversal of said mixed pump beam, integrated gain homogenization is achieved for the amplification of the seed beam independent of the spatial nonuniformities of said pump beam, and the local gain imparted to the seed beam at individual locations along its traversal of said mixed pump beam is nonhomogeneous.

A method of phase conjugating an input optical beam that is characterized by a spatially non-uniform optical intensity, comprising:

• spatially mixing said input beam with a stimulated Brillouin scattering (SBS) amplification medium by passing the beam through at least a pair of cylindrical lenses located near an input side of said SBS medium to achieve a mixed beam with an approximately uniform spatial distribution of integrated optical intensities but a local cross-sectional optical intensity distribution that differs from location to location along a return beam path through said SBS medium,
• phase conjugating said mixed beam,
• directing said phase conjugated beam back through said SBS medium along said return beam path, and
• causing said phase conjugated beam to travel in an opposite direction to said input beam within said SBS medium to effect an integrated amplification of the phase conjugated beam by the input beam that is generally spatially independent of location across said phase conjugated beam, a local amplification of the phase conjugated beam that differs for different locations along the return beam path through said SBS medium, and a uniform gain homogenization.