通过深入分析二次谐波转换效率，以周期极化晶体MgO:sPPLT 为研究对象，结合其斯涅耳方程和极化周期随温度的热膨胀关系，得到了基频光正入射时周期极化晶体的最佳匹配温度；当基频光倾斜入射时，极化周期等效变大，最佳匹配温度降低。利用归一化倍频效率图形，可以方便地得到给定晶体长度的温度和波长接收带宽；同时晶体通光长度越长，温度和波长接收带宽越窄。只要更换晶体的斯涅耳方程和极化周期随温度的热膨胀关系，所使用的研究方法可方便地推广到其他周期极化晶体的倍频研究当中。所得到的这些结论对于使用周期极化晶体进行倍频，尤其是连续光纤激光器腔外倍频有一定的指导意义。

Best matching temperature is obtained when the fundamental laser is of normal incidence in periodically poled crystal. The in-depth analysis of second harmonic nonlinear conversion efficiency uses periodically poled crystal MgO∶sPPLT as the research object, and combines the Sellmeier equation and the polar period with temperature thermal expansion relationship. When the fundamental laser tilt is incident, the equivalent polar period becomes larger, and the best matching temperature is reduced. Acceptable temperature and wavelength bandwidth can be obtained conveniently by using the normalized frequency doubling efficiency curves for the given length of frequency doubling crystal. The crystal length becomes longer, and the acceptable temperature and wavelength bandwidth become narrower. As long as the Sellmeier equation and polar period with temperature thermal expansion relationship are known, the method used in this study can be extended to other periodically poled crystals. These conclusions are useful for other periodically poled crystals and guiding continuous wave fiber laser external cavity frequency doubling.