REFLECTION OF LIGHT FROM A DISORDERED MEDIUM BACKED BY A PHASE-CONJUGATING MIRROR

This is a theoretical study of the interplay of optical phase conjugat ion and multiple scattering. We calculate the intensity of light refle cted by a phase-conjugating mirror when it is placed behind a disorder ed medium. We compare the results of a fully phase-coherent theory wit h those from the theory of radiative transfer. Both methods are equiva lent if the dwell time tau(dwell) of a photon in the disordered medium is much larger than the inverse of the frequency shift 2 Delta omega acquired at the phase-conjugating mirror. When tau(dwell)Delta omega l ess than or similar to 1, in contrast, phase coherence drastically aff ects the reflected intensity. In particular, a minimum in the dependen ce of the reflectance on the disorder strength disappears when Delta o mega is reduced below 1/tau(dwell). The analogies and differences with Andreev reflection of electrons at the interface between a normal met al and a superconductor are discussed. [S1050-2947(97)06611-0].