Optical limiters using photorefractive nonlinearities

The ability of photorefractive crystals such as barium titanate and strontium barium niobate to record spatially phase shifted real time holograms with high diffraction efficiency is the basis of many new optical devices involving coherent amplification. Some examples are unidirectional ring resonators, passive phase conjugate mirrors and coherent image amplifiers. 1 While in the past, most attention has been paid to gain and beam amplification in these devices, we pay attention here to the beams which are deamplified, as a means of developing optical limiters.