对连续波光参量振荡器(OPO)的最优转换效率进行了实验研究。选用氧化镁掺杂的周期性极化铌酸锂晶体作为光参量振荡器的非线性晶体，通过匹配抽运光功率和输出镜反射率控制腔内的信号光光强，实验验证了OPO腔内存在最优信号光光强，能够使光参量振荡器的转换效率最优化。在此基础上，在2.9 μm波段实现了8 W的闲频光输出，输出效率达到19.5%。在无外加线宽限制器件的情况下，输出线宽小于0.68 nm。

Optimal conversion efficiency of a continuous-wave optical parametric oscillator (OPO) is investigated experimentally. The nonlinear crystal of OPO is a magnesia-doped periodic polarization lithium niobate crystal. As the power density inside the OPO cavity is associated with the reflectivity of the cavity mirrors, different cavity mirrors are used. Experimental results show that the best intensity inside the cavity exists to obtain the best conversion efficiency. By the coupling of the pump power and the OPO cavity, 8 W idler output at 2.9 μm with the efficiency of 19.5% is achieved. The spectral width of the 2.9 μm laser is less than 0.68 nm without any additional bandwidth control elements.