报道了一种采用复合腔进行腔内和频的500.9 nm激光器。激光器由两个子谐振腔组成。在两个子谐振腔中，分别利用两个激光二极管抽运Nd:YAG 晶体和Nd:YVO4晶体，并分别选择946 nm波长与1064 nm波长振荡进行和频。采用双端复合Nd:YAG晶体以减小高功率下激光晶体的热透镜效应，并结合热效应对高功率抽运下谐振腔进行优化设计，实现了腔内两个波长较好的模式匹配。在两个子腔的交叠部分，利用KTP晶体Ⅱ类临界相位匹配进行腔内和频，得到和频激光输出。当Nd:YAG与Nd:YVO4晶体上抽运功率分别为10.6 W和17.8 W时，获得了730 mW的500.9 nm青绿光激光输出，光-光转换效率为2.6%。实验结果和分析表明，利用复合腔和频是获得500.9 nm激光输出的有效方法。

A continous-wave (CW) 500.9 nm laser using intracavity sum-frequency mixing in a doubly resonant configuration is reported. The laser has two sub-cavities. A Nd:YAG crystal and a Nd:YVO4 crystal are pumped by two laser diodes respectively in two sub-cavities. In the two cavities wavelengths of 946 nm from Nd:YAG and 1064 nm from Nd:YVO4 are chosen to be mixed into 500.9 nm laser. A composite Nd:YAG crystal is used to deduce the thermal lens effect under high power pumping, and cavity design is optimized considering the thermal lens effects. Better matching of the modes for the two wavelengths is obtained. In the overlapping of the cavities, sum-frequency mixing is generated with a type-Ⅱ critical phase matching KTP crystal. An output power of 730 mW at 500.9 nm is obtained at the incident pump power of 17.8 W for the Nd:YAG crystal and 10.6 W for the Nd:YVO4 crystal. The analyses and experiment show that the doubly resonant intracavity sum-frequency mixing is a useful method to obtain 500.9 nm laser efficiently.