Phase conjugation in liquid suspensions of microspheres in the diffusive limit

We examine phase conjugation via degenerate four-wave mixing in liquid suspensions of microspheres in the small-field limit, where saturation effects can be ignored. For these media, electro- strictive forces modulate the microparticle density in such a way that two orthogonal spatial gratings are created. Coherent scattering of the pump radiation from these two gratings gives rise to the formation of a conjugate wave, as well as amplification of the probe wave. We discuss the steady-state and transient characteristics of the probe and conjugate waves in this regime where the dynamics of the microparticles is governed by diffusion.