LiNbO3:Fe晶体中光写入平面光波导的导光特性研究

从光折变效应的单中心模型和载流子的光伏迁移机理出发给出了高斯片光在LiNbO3:Fe晶 体中导致的折射率变化分布的解析表达式.利用片光以“三明治”辐照方式在LiNbO3:Fe晶 体中写入了平面光波导结构.用切片干涉法测量了波导区的折射率分布，并对波导进行了简 单的导光测试.根据射线方程以及波导的折射率分布对光写入波导的导光特性进行了模拟计 算分析.研究结果表明，在LiNbO3:Fe晶体中光写入光波导是可行的. 关键词： LiNbO3:Fe晶体 光辐照法 平面光波导 导光特性 高斯片光

Analyses of guiding properties of light-induced planar waveguides in LiNbO3:Fe crystals

To our knowledge, we first deduced the analytic expression of the index changed istribution in LiNbO3:Fe crystal induced by a Gaussian sheet beam considering th e photorefractive one center model and the photovoltaic charge carriers transp or tmechanism. A planar waveguide structure was fabricated by sheet beam illuminat ion employing the sandwich method in LiNbO3:Fe crystal. The index distribu tion i n the waveguide region was measured by using interferometric technique and the g uiding test was also performed. The rationality of the deduced analytic expression was demonstrated by the fitting results of the measured data point. Based on the ray equation, the guiding properties of the light-induced waveguide were analyzed by using numerical simulation. The results show that the interferom etric technique is valid for measuring the index distribution of waveguide with large width, and the guiding properties of the light induced waveguide structures depend on the waveguide width strongly. Using sheet beam with small width, planar waveguide structure with high quality can be fabricated in LiNbO3:Fe cryst al . And the analytic expression of the index change distribution can be employed to predict the guiding properties of the light induced waveguide.