为了无损表征周期性极化晶体的畴结构，用严格耦合波分析法分析了周期性极化铌酸锂晶体的周期和占空比.以波长为532 nm，功率为20 mW的连续激光器为光源， TE偏振光垂直入射周期性极化的铌酸锂晶体表面，同时对晶体施加电压以改变其正负畴间的折射率差，通过光电探测器检测各衍射级的衍射效率.使用最小二乘法将光电探测器记录的实验数据与严格耦合波分析模拟的结果进行优化拟合，反演出晶体的周期和占空比.测试结果表明，该方法能准确地测试周期性极化铌酸锂晶体的周期和占空比，其周期的测试准确度为0.05 μm，占空比的测试准确度为0.05.比布喇格衍射公式计算的晶体周期准确度提高一个数量级.

In order to nondestructively measure the domain structure of periodically polarized crystal, the rigorous coupled-wave analysis was used to analysis the period and duty cycle of the microstructure. A laser with a wavelength of 532 nm and power of 20 mW was used as the light source. The beam with TE polarization is vertically incident on the periodically poled lithium niobate crystal surface, at the same time the voltage is applied to the crystal to increase the refractive index difference between the positive and negative domains. The power of each diffraction orders is detected by a photo detector . The period and duty cycle of the periodically poled lithium niobate crystal can be got by using the least squares method to fit the simulation results of the rigorous coupled-wave analysis and the experimental data. The experimental accuracy of the period and the duty cycle is 0.05 μm and 0.05 respectively. Compared with the period calculated by the Prague diffraction formula, the precision is improved by an order of magnitude.