TEMPORAL EVOLUTION OF FANNING IN PHOTOREFRACTIVE MATERIALS

We present detailed calculations of the temporal and spatial evolution of beam fanning in photorefractive crystals that is initiated by scat tering from noise. We show that fanning starts from beam coupling betw een the incident radiation and part of the incident radiation scattere d by noise at or near the input plane. We show that scattering within the volume of the crystal has negligible effect on fanning, that absor ption affects the time response but not the spatial pattern of the fan ning, and that the difference between calculations including only phas e-matched terms and those including non-phase-matched terms is negligi ble.