Abstract

Numerous applications have been found for phase-conjugation correction of aberrations due to optical elements, laser amplifiers, and atmospheric propagation. Techniques for phase reversal include stimulated Brillouin scattering (SBS) and four-wave mixing. A limitation on the former method has been the requirement of a high-intensity incident pump beam to initiate the process. Several methods have been proposed^1,2 to lower the threshold power for SBS: (1) refocusing the transmitted beam from the first SBS cell so that the Stokes return from the second focus can "backseed," i.e. raise the noise level from which the process initiates, the first focus; (2) a loop configuration in which the transmitted beam is injected at a small angle with respect to the incident beam and reflected by the acoustic grating of the first focus; and (3) a ring resonator geometry in which a small portion of the transmitted beam is fed back along the path of the incident pump beam. The ring configuration is illustrated in Fig. 1.

© 1991 Optical Society of America