ENERGY-TRANSFER MEASUREMENT AND DETERMINATION OF THE PHASE-SHIFT BETWEEN THE HOLOGRAPHIC GRATING AND THE FRINGE PATTERN IN PHOTOREFRACTIVE MATERIALS

We describe a novel accurate method to measure energy transfer between two beams coupling in photorefractive materials. We have used this me thod to measure the on-line energy-transfer signal in an electrically poled BaTiO3 crystal and to record the growth of the grating responsib le for energy transfer. We also used this technique to determine the p hase shift between the grating that is written in the crystal and the fringe pattern responsible for writing that grating. The phase shift i n our BaTiO3 is found to be 90-degrees, as predicted by the diffusion model.