Weak response measurements of photosensitive media

A high-sensitivity interferometric method to measure parameters of volume d iffraction gratings written in photosensitive media is proposed. The method is bused on measuring the transient energy transfer among phase-modulated coherent beams that results from their own diffraction with dynamic grating s in the medium. It is theoretically shown that there is a simple mathemati cal dependence between the amplitudes of the output beams intensity modulat ion and the grating parameters. The method was applied to measure the photo response of polymer films containing bacteriorhodopsin.