MODULATION DEPENDENCE OF THE PHOTOREFRACTIVE RESPONSE WITH MOVING GRATINGS - NUMERICAL-ANALYSIS AND EXPERIMENT

The photorefractive response with moving gratings is investigated both numerically and experimentally under varied fringe-velocity and modulation-depth (m = 0.002 to m = 1) conditions. The numerical analysis employs a finite-difference technique to model photorefractive grating dynamics. The magnitude and the phase of the space-charge field are presented in detail as functions of modulation depth, fringe velocity, and crystal parameters. Energy transfer and diffraction efficiency are found to exhibit different response characteristics with modulation and fringe velocity. Numerical results for two-wave mixing are generalized through analytical expressions that approximate the numerical solutions. Illustrative experimental results are presented for Bi12SiO20.