Optical energy transfers, via stimulated scattering, to a seed beam from a pump beam that has a non-uniform optical intensity distribution are made with an enhanced spatial uniformity of amplification by spatial mixing of the pump beam within the medium where amplification takes place. In a stimulated Brillouin scattering (SBS) phase conjugate mirror (PCM) (2) having an amplifier (4) and a phase conjugating oscillator (6), beam mixing elements (30, 32, 34, 36) are provided on opposite sides of the amplifier (4) to mix both the input and return phase conjugated beams (8) within the amplifier (4), and to restore the beams after they have exited. The preferred mixing mechanism is a plurality of cylindrical lenses (30, 32, 34, 36) that are spaced along the beam path, and/or have unequal focal lengths to produce a series of foci (50, 52) within the amplification medium that are rotated with respect to each other. Amplitude replication as well as high fidelity phase conjugation are enhanced using SBS.
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