TEMPORAL MEMORY EFFECTS IN PHOTOREFRACTIVE 2-BEAM COUPLING - A STUDY COMPARING N-DOPED AND P-DOPED BATIO3 AT 514-NM AND 830-NM

The photorefractive gain and time response of n-doped and p-doped BaTi O3 were compared in the visible, lambda = 514 nm, and in the infrared, lambda = 830 nm. Two-beam coupling experiments were conducted for bea m ratios between 3600:1, 5000:1, and 8000:1. In both infrared and visi ble it was observed that the measured gains were higher for the p-BaTi O3 by an order of magnitude or more. When the gain was high, a tempora l memory effect was observed, suggesting that the time dependence of t he space-charge field is determined by the history of the modulation d epth. This effect is shown to be consistent with the Kukhtarev equatio ns for a single carrier. Low-gain behavior was observed at all interac tion angles for both crystals in the IR. In the visible the high-gain temporal memory effect is reported for the p-BaTiO3. (C) 1998 Optical Society of America.