Observation of Optical Bistability in Two-Dimensional VolumeRefractive Index Grating Thermally Fixed in LiNbO3:Fe Crystal

Experimental observation of optical bistability in a nonlinear two-dimensional volume refractive index grating is reported. The index grating in LiNbO₃:0.1 wt.% Fe photorefractive single crystal was fabricated by using hologram recording and subsequent thermal fixing techniques. Due to the thermal fixing, the stored 2D volume index grating shows no optical erasure during readout. An explanation of the nonlinear phenomena is also given in terms of the intensity-enhanced bulk photovoltaic effects in LiNbO₃:Fe material.