Applications Of Raman Beam Cleanup And Phase Conjugation To The Reduction Of Laser Beam Aberrations

We describe the use of Raman beam cleanup for reducing the divergence of laser beams. Distortion-free amplification of a diffraction-limited Stokes beam with a pump beam aberrated to 120 times its diffraction limit is demonstrated. With a power conversion efficiency of 30% the resulting increase in brightness was 5000 times. We also demonstrate the combination of phase conjugation and Raman beam cleanup to remove distortions on the Stokes beam. Results are compared with theory.