The photorefractive properties of LiNbO3 with an emphasis on the contributions from intrinsic defects are examined. After a short background of the photorefraction with the presentation of basic relations, the photoinduced charge transport in photorefractive compositions, mainly in LiNbO3:Fe are discussed. The current concept of the dark conductivity is formulated assuming a concurrence between protons and the electronic conductivity dictated by the Fe concentration. The traditional one-center charge transport scheme based on the electron transfer between the donor Fe2+ and the deep trap Fe3+ is refreshed and the experimental data not fitting this model are listed. A refined two-center scheme based on the assumption of the Nb antisite involvement in the charge transport as a shallow electron trap is discussed and the experimental arguments supporting this model are summarized.
General Introduction to Photorefraction in LiNbO3. (2009). In Springer Series in Materials Science (Vol. 115, pp. 51–74). Springer Verlag. https://doi.org/10.1007/978-3-540-70766-0_3