Cross-polarization two-beam coupling in optically active photorefractive media

We present a theoretical description of the coupling of energy and polarization between two beams in an optically active photorefractive medium. We apply this analysis to the problem of cross-polarization two-beam coupling and determine the dependence of the cross-polarization coupling gain on the input polarization states of the interacting beams and the properties of the coupling medium. In particular, we show that by a proper choice of the input polarization states, the cross-polarization gain seen in typical optically active photorefractive materials may be increased by more than 2 orders of magnitude over that previously observed. As a test of our theoretical treatment, we also apply it to standard two-beam coupling in Bi12SiO20 and obtain close numerical agreement with earlier experimental results in this material.