为解决激光器非线性频率变换时非线性晶体的热效应问题, 解析地研究了激光器谐振腔内多模振荡状态下非线性晶体的温度分布。通过对激光器腔内模特点分析, 得出了谐振腔归一化的多模光束表达式。基于非线性晶体腔内变频工作状态分析, 建立了非线性晶棒热分析模型, 采用一种新的热传导方程求解方法, 得到了非线性晶棒多模变频工作状态下温度场的一般解析表达式。同时分析了激光器腔内基波功率、光斑半径对非线性晶棒温度场分布的影响。研究结果表明, 若腔内多模激光功率为 500W、光束腰半径为 80滋m时, KTP晶棒内最高温升为 126.3益。研究对于减小非线性晶体温升引起的相位失配以及提高激光器谐波转换效率将起理论指导作用。

In order to solve the thermal effect problem of nonlinear optical crystal with nonlinear frequency conversion in laser, thetemperature distribution of nonlinear crystal with intra-cavity multi-mode oscillation was analytically investigated. By analyzing themode characteristics in resonant cavity, the expression of normalized multi-mode light beam in the resonator was obtained. Based onanalysis of the working condition of intra-cavity frequency changing with a nonlinear crystal, a thermal physical model of nonlinearcrystal rod was built, Temperature field general analytical expression of nonlinear crystal in the working state of multi-mode frequencychanging was obtained by a new solution of heat conduction equation. Also analyzing the impact of fundamental wave power and spotradius on temperature field distribution of nonlinear crystal rod. The results show that when the power of multi-mode laser is 500 W,and the spot radius of laser beam is 80滋m, the maximum temperature rise of KTP crystal rod is 126.3益. The research will playainstructive role in decrease of phase mismatching induced by the thermal effect of nonlinear crystal and improvement of the harmonicconversion efficiency of nonlinear crystal.