Numerical investigation of two-beam coupling in hybrid liquid crystal-photorefractive cells using the finite-difference time-domain method

Photorefractive two-beam coupling is a nonlinear optical phenomenon that finds application in a range of photonic devices. The spatially modulated refractive index due to the space-charge field that arises from the interference pattern generated by crossed laser beams is responsible for two-beam coupling in photorefractive materials. Penetration of this field into the region surrounding the photorefractive results in the reorientation of liquid crystal molecules, providing a mechanism for enhancement of two-beam coupling. We present a numerical investigation of two-beam coupling in organic-inorganic hybrid cells consisting of a liquid crystal layer sandwiched between two photorefractive windows. Finite-difference time-domain calculations of beam propagation in such hybrid cells are carried out using the electric permittivity tensor field derived from the liquid crystal director spatial profile in steady state.