Research Progress on Photorefraction of Lithium Niobate Crystal Doped with High Valence Ion

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Lithium niobate (LiNbO 3 , LN) is an artificial crystal with excellent physical properties, such as acousto-optic, electro-optic, piezoelectric, and photorefractive performance.It is not only seen as "optical silicon", but also suggests that humans are entering the era of "Lithium Niobate Valley".Its excellent optoelectronic properties have a wide potential application in emerging fields, such as artificial intelligence and photoelectric hybrid module.Photorefraction was found and proved to be an important property of LN crystal.With development of optoelectronic devices based on LN to micro-and nano-scale, photorefractive effect has gradually appeared.Single crystal LN is the basic material for preparing various devices taking advantage of lithium niobate on insulator (LNOI).The 无 机 材 料 学 报 第 40 卷 photorefractive properties can be adjusted by doping appropriate impurity ions.Compared with normal ions (valence < +5 (valence of niobium ions)), incorporation of high-valence ions (valence ≥ +5) can be more beneficial to improve photorefractive performances of LN crystals in recent years.This paper summarizes research progress of high-valence ion-doped LN crystals of which doping with V, Mo, U, and Bi ions can effectively adjust their photorefractive properties, suitable for designing micro-ring resonators, optically programmable photonic components, nonlinear photonic devices, and other micro-and nano-scale devices.Finally, based on above advances in high-valence ion doped LN, further research may achieve unprecedented improvements in four aspects: high-quality and big-size crystal growth, photorefractive mechanism, ion doping with lone-pair electrons, and novel optoelectronic devices.