PARAMETRIC 4-WAVE PROCESSES IN PHOTOREFRACTIVE CRYSTALS

A theory of polarization-dependent four-wave processes is developed fo r photorefractive nonlinear media. It includes the classification of p ossible elementary nonlinear processes, an analysis of their polarizat ion and geometric properties, and a unified technique for the calculat ion of wave amplitudes. The theory is applied to the description of di fferent types of conical scattering in BaTiO3 and LiNbO3 crystals. Eff ects of crystal anisotropy, angular and frequency detunings for intera cting waves are taken into account. A good agreement between theory an d experiment is demonstrated. Applications of the theory to treatment of a number of important photorefractive effects are considered.