LiNbO_3晶体中光折变光栅各向异性衍射的定量研究

Quantitative Study on Anisotropic Diffraction of Photorefractive Gratings in LiNbO_3 Crystals

对LiNbO3晶体中光折变光栅的各向异性衍射进行了定量研究。基于有效电光系数非零和布拉格相位匹配条件,对在LiNbO3晶体中各向异性衍射的衍射效率与光束偏振态和写入几何的关系进行了较为详细的理论计算和分析,根据建立的数学模型进行了数值计算,发现光轴垂直于写入平面时,写入的光栅可发生显著的各向异性衍射。实验测量与理论计算结果基本符合。

The anisotropic diffraction property of photorefractive gratings has been studied quantitatively. The dependence of the efficiency of anisotropic diffraction in LiNbO3 crystals on the beam polarization and recording configuration is theoretically calculated based on two constrains for remarkable anisotropic diffraction, the phase matching and non-zero effective electro-optic coefficients. Then numerical calculations have been conducted based on the theoretical model. It is found that the anisotropic diffraction efficiency is remarkable and easy to be observed in transmission gratings written by two extraordinary beams with the crystal axis perpendicular to the plane of writing beams. The results of experimental measurements of the readout angle for observing anisotropic diffraction agreed well with the theoretical calculations. Some experimental results of anisotropic diffraction efficiency also agreed with the theoretical calculations.