<title>Effect of In ions on photorefractive properties in Fe:In:LiNbO3 crystals</title>

Abstract

Lithium niobate single crystal has been found to be a versatile material in the field of nonlinear devices due to its excellent electric-optical, dielectric and nonlinear optical properties. When LiNbO₃ device serves as holographic storage media, it is often required a big dynamic range, a big sensitivity and a high photo-damage resistance ability. Although Fe-doped LiNb0₃ in holographic storage is one the most widely investigated crystals and takes on better comprehensive merits, its performance is severely limited by the low photo-damage resistance ability when LiNbO₃ is operated on high laser intensity. Indium is one of the beneficial impurity ions for suppressing photo damage. In this paper, we grown a series of Fe:In:LiNb0₃ crystals with a varying content of In doping by Czochraski technique. On the basis of the ultraviolet-visible absorption spectra measurement and two-wave coupling experiment, the effect of In ions on photorefractive properties is explored and discussed systematically. It is found that the photorefractive properties can be greatly enhanced by In doping in Fe:LiNb0₃. Among the four samples of Fe:In:LiNbO₃ crystals, the Fe:In(2 mol%):LiNbO₃ crystal has the highest photorefractive sensitivity and the largest dynamic range (1.79 cmJ^-1 and 2.10, respectively) and can resist higher intensity laser irradiation. Our analysis indicates that increased photoconductivity is mainly responsible for the excellent photorefractive comprehensive properties. It is believed by the experimental results that Fe:In(2 mol%):LiNbO₃ crystal is a promising holographic storage medium.