铌酸钾锂晶体的生长和缺陷

Growth and Defects of Potassium Lithium Niobate Crystals

用电阻加热提拉法生长了一系列较大尺寸 ,组分离子均匀性较好的铌酸钾锂晶体。利用X射线荧光光谱法测量了不同配比的熔体中生长出的晶体组成 ,用同步辐射X射线测量了晶体结构 ,结果表明随晶体组成变化 ,晶体的晶格常数发生了变化。根据晶体组分离子浓度与折射率的关系研究了晶体折射率变化情况 ,结果表明用本方法生长的大尺寸KLN晶体 ,寻常折射率no 在测量误差范围内没有变化 ,非寻常折射率ne 的变化率在 82 0nm仅为1.2 2× 10 -4 /mm ,在 410nm仅为 1.93× 10 -4 /mm。晶体的干涉条纹证明了晶体有良好的光学均匀性。结合晶体生长实验 ,探讨了改进晶体组分离子浓度分布均匀性的方法 ,结果表明采用籽晶和坩锅向相同方向旋转可以改善晶体生长界面处组分离子浓度的波动 ,提高晶体组分离子均匀性。晶体的缺陷研究表明晶体结构完整性较好 ,位错形状与晶体结构相一致 ,密度为 7.5× 10 4 ,[0 0 1]轴是晶体的极化轴。晶体对 890～ 96 0nm波长范围的cw

A series of potassium lithium niobate (KLN) crystals with large size and good homogeity for composional ions have been grown.The crystal structure has been determined using X ray.The results showed that the lattice constants of KLN crystal changed with the crystal composition.The variation of refractive index has been studied by using the relation between the concentration of compositional ions and the refractive index of KLN crystal and the results showed that the n o nearly had no changes in the range of measure errors,and n e changed 1.22×10 -4 /mm (at 820nm) and 1.93×10 -4 /mm (at 410nm).The interference streak of KLN crystal showed that the optical homogeneities of the crystal are good.The method to improve the uniformity of compositional ions has been discussed,the experiment results of crystal growth showed that it might reduce the variational extent of compositional ions in the interface of solid melt,thus improve the uniformity of compositional ions in crystal.The studies of crystal defects have shown that the crystal quality is good,the defect form is coincidence with the structure of the crystal.The defect density is 7.5×10 4.The axis is the pole axis of KLN crystal.The frequency doubling results of the crystal using cw Tisapphire laser in the wavelength range of 890-960nm showed that the crystal had good frequency doubling properties.