An Analytic Expression for the Photorefractive Two Beam Coupling Response Time

Among the most widely used properties of photorefractive materials is their ability to couple energy between two beams overlapping within the medium. This property allows for a weak information carrying beam to be amplified at the expense of a strong pump beam and thus provides a fundamental building block in a variety of applications of practical interest including optical interconnection and computing, image processing and laser hardening. In engineering such optical systems involving a photorefractive amplifier, accurately predicting the speed at which the amplifier will respond becomes a necessary facet of system design. As a result, the temporal response of the photorefractive effect has been the subject of extensive investigation. In the absence of two beam coupling, these investigations have resulted in explicit expressions for the photorefractive response time as a function of various relevant material and environmental parameters. While similar expressions valid when beam coupling is present have not yet been presented, and indeed are the subject of this paper, substantial progress toward their development has been made previously by other workers.