PHOTOREFRACTIVE GRATINGS IN PLANAR OPTICAL WAVE-GUIDES IN CUBIC-CRYSTALS

The space-charge field of the photorefractive grating in planar wavegu ides in cubic crystals is considered. Analytical expressions are deriv ed from three cases: the initial stage of photorefractive grating form ation, the steady state, and the photorefractive grating formation in waveguides with a short diffusion length and high dark conductivity an d without trap saturation. The orientation dependencies of the wavegui ding two-beam coupling factor for the (110), the (111), and the (100) cuts of the substrate are considered. The overlap factors of the cross distributions of the space-charge field and the light field of the wa veguide modes are calculated for waveguides with a step-shaped profile of the refractive index.