Mutual phase conjugation in media with a local response

The mutual phase conjugation of the light beams from two independent sources in media with a local nonlinear response is examined theoretically. The self-conjugation of light in a phase-conjugation mirror with a feedback loop based on this effect is also analyzed. The thresholds for generation of the conjugate beams are derived, as are the phase relations between the conjugate beams. Optical elements which introduce a nonreciprocal phase shift in the interacting beams must be used. The basic principles for constructing phase-conjugation devices which operate on the basis of mutual phase conjugation are worked out.