Diffraction efficiency of photorefractive index gratings

Abstract

We discuss the diffraction properties of refractive index gratings with arbitrary phase shift in photorefractive media. The rederiving results indicate that Kukhtarev's equation for the diffraction efficiency can describe two real experimental situations, i.e. the photorefractive grating written by two coherent beams is read soon after by one of the writing beams as the reading beam in the non-simultaneous writing-reading process, and is simultaneously read by an incoherent weak reading beam in the simultaneous writing-reading process. An analytical expression for the diffraction efficiency is obtained in the simultaneous writing-reading process for the general case of arbitrary spatial phase shift between index grating and fringe pattern, and a reading beam intensity comparable with that of the writing beams.