The essential features of the photorefractive phenomena in electrooptic oxides are reviewed. Emphasis is laid on the active point defects and their role in determining physical behaviour. The situation is illustrated in some detail for LiNb03, where a great deal of information is available.
F. Agullo-Lopez, F. Agullo-Lopez,
"Point Defects And Photorefractive Phenomena In Electrooptic Oxides", Proc. SPIE 1018, Electro-Optic and Magneto-Optic Materials, (31 January 1989); doi: 10.1117/12.949996; https://doi.org/10.1117/12.949996