Compensation for phase distortions in nonlinear media by phase conjugation.

The ability of nonlinear optical phase-conjugate mirrors (PCM's) to correct for linear refractive-index inhomogeneities has been demonstrated both theoretically1'2 and experimentally.2 Propagation media often possess intensity-dependent indices of refraction that cause severe propagation distortion, such as thermal blooming and self-focusing. These distortions are often manifested in high-intensity atmospheric propagation of laser beams, thermally induced lensing within intracavity laser gain media, or high-intensity transmission through optical fibers. In this Letter we extend the distortion-correction proof of Yarivl'2 to media with intensity-dependent indices of refraction.3 A typical geometry is sketched in Fig. 1. We consider a monochromatic electromagnetic field at radian frequency w, which propagates essentially in the +z direction and is given by