Abstract

Nominally pure congruent LiNbO₃ crystal and LiNbO₃:ZnO ([ZnO] ~ 5.4–6.4 mol % in the melt) crystals of different genesis are studied using photoinduced light scattering, laser conoscopy, and X-ray diffraction (method of moments). The photorefractive properties and optical and structural uniformity are analyzed. It is found that LiNbO₃:ZnO crystals obtained by direct solid phase doping have the best optical and structural uniformity, the lowest photorefractive sensitivity, and a high compositional uniformity along the polar axis. Crystals obtained by homogeneous doping are compositionally uniform, although their optical and structural uniformity is worse than those of LiNbO₃:ZnO crystals obtained by direct solid phase doping. Anomalies of conoscopic patterns are caused by the presence of charged structural defects in LiNbO₃:ZnO crystals and the distortion of the optical indicatrix induced by mechanical stresses and compositional inhomogeneity of the crystals. High temperature annealing in short-circuited state of LiNbO₃:ZnO crystals with high dopant concentration leads to healing of charged defects and improvement of optical characteristics in general. The distribution coefficient for LiNbO₃:ZnO crystals obtained by the homogeneous doping method is significantly higher than that for the crystals obtained by the direct solid phase doping method.

中文翻译：

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不同成因的LiNbO 3：ZnO晶体的结构和光学同质性研究

摘要

使用光诱导光散射，激光显微镜和X射线衍射（矩量法）研究了不同起源的名义上纯的全同LiNbO ₃晶体和LiNbO ₃：ZnO（[ZnO]〜5.4–6.4 mol％）晶体。分析了光折变性质以及光学和结构均匀性。发现通过直接固相掺杂获得的LiNbO ₃：ZnO晶体具有最佳的光学和结构均匀性，最低的光折光敏感性以及沿极轴的高组成均匀性。通过均质掺杂获得的晶体虽然在光学和结构上的均匀性比LiNbO ₃差，但是在成分上是均匀的通过直接固相掺杂获得的：ZnO晶体。锥光图案的异常是由LiNbO ₃：ZnO晶体中带电结构缺陷的存在以及由机械应力和晶体组成不均匀性引起的光学指示物变形引起的。具有高掺杂浓度的LiNbO ₃：ZnO晶体在短路状态下的高温退火通常导致带电缺陷的修复和光学特性的改善。通过均相掺杂方法获得的LiNbO ₃：ZnO晶体的分布系数明显高于通过直接固相掺杂方法获得的晶体的分布系数。