Spatial subharmonics of moving gratings in photorefractive materials

A simple theory based on a nonlinear differential equation derived from Kukhtarev’s materials equations and the coupled mode analysis of wave equation is developed to describe the spatial subharmonics in the photorefractive moving gratings. The optimum detuning frequency of K/2 spatial subharmonic resonance is calculated and compared with experimental data. It is found that our simple theory describes the experimental data very well.