Optically fixed photorefractive correlator

An optically fixed photorefractive correlator is presented, where two-centre non-volatile holographic recording is employed to write and fix the matched filter in doubly doped LiNbO₃ crystals. This correlator shows good correlation characteristics and insensitivity to the writing beam during readout. It can be used in cases requiring stability and not requiring modification for a long period, and it is refreshed optically when new information needs to be registered.