Energy-transfer measurement and determination of the phase shift between the holographic grating and the fringe pattern in photorefractive materials

Abstract

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