为解决激光二极管(LD)端面抽运激光介质产生的热效应问题,建立了端面绝热、周边恒温、界面热流连续的YAG-Nd:YAG复合晶体棒热分析模型。利用特征函数法和常数变异法得到了超高斯光束端面抽运YAG-Nd:YAG复合晶体棒温度场的一般解析表达式。同时定量分析了超高斯抽运光光斑尺寸,光束阶次,YAG晶体长度对YAG-Nd:YAG复合晶体棒温度场的影响。研究结果表明,若LD输出功率为50 W,光学耦合器传输效率为82%,4阶超高斯光束端面抽运YAG-Nd:YAG复合晶体棒时,复合晶体棒内最大温升为132.7 ℃,其中YAG晶体长为1.5 mm,Nd:YAG晶体长5 mm,钕离子掺杂质量分数为1.0 %。研究结果为减小激光晶体热效应、合理设计激光器热稳腔提供了依据。

In order to solve thermal effect of laser medium end-pumped by laser diode (LD),a thermal analysis model of YAG-Nd:YAG composite crystal rod with adiabatic end faces,fixed boundary temperature and consecutive heat flow interface was established. A general analytical temperature field expression of YAG-Nd:YAG composite crystal rod end-pumped by super-Gaussian beam was obtained by the methods of eigen-function and constant variation. Meanwhile,some factors,such as the super-Gaussian beam with different spot radius,different orders and the length of YAG crystal,which influenced the temperature distribution of YAG-Nd:YAG composite crystal rod,were quantitatively analyzed. The results showed that when the output power of LD was 50 W,the transmission efficiency of optical focusing coupler was 82%,the maximal temperature rise of the YAG-Nd:YAG composite crystal rod,in which the length of YAG crystal is 1.5 mm,the length of Nd:YAG crystal is 5 mm and the neodymium ion doped concentration in the crystal is 1.0% (mass fraction),end-pumped by the forth super-Gaussian beam was 132.7 ℃. The results would provide a theoretical basis for reducing the thermal effect of laser crystal and reasonably designing thermally stabilized cavity of solid-state laser.