Abstract

There has been considerable interest recently in the physics and potential applications of self-pumped phase conjugate mirrors using various photorefractive materials. In spite of the intense interest in one particularly appealing device—the internally pumped phase conjugate mirror¹—its operation is not well understood. As an aid in improving our understanding of this device, we have measured the specular reflectivity from the input face of a crystal of BaTiO₃ during self-pumped operation. Measurements were performed (at λ = 5145 Å) as a function of the angle of incidence for both linear polarization states. For the s-polarization state—which does not lead to self-pumped conjugation—we find good agreement with the standard Fresnel reflection relations. However, for the p-polarization state, the specular reflectivity drops from the standard Fresnel reflection value (e.g., ~15% at near-normal incidence) to ~2%—a value less than that for an air-glass interface. The temporal dependence of the drop in the specular reflectivity correlates well with the conjugate-wave build-up time. By angularly dithering the crystal—thereby destroying the photorefractive-induced gratings—the p-polarization reflectivity is restored to its standard value. A phenomenological model involving destructive interference of the specular component² via internally reflected fields gives reasonable agreement with experiment.

© 1986 Optical Society of America