MEMORY EFFECTS IN PHOTOREFRACTIVE MATERIALS

We have determined that the dynamics of the signal in photorefractive two beam coupling can be described by a memory effect in the writing o f the space charge field. Experimental and computational results confi rm that this time dependence is dependent on the history of interferen ce pattern responsible for the space charge field. From this memory ef fect it is shown that if the input signal has a sinusoidal component m uch smaller than its DC component, the sinusoidal component of the two beam coupled signal is shifted by the response time of the photorefra ctive medium. We have demonstrated, both theoretically and experimenta lly, that for the non-depleting pump this response time is linear with the interaction length.