报道了采用自行研制的全光纤主振荡功率放大(MOPA)结构1064 nm单频Yb光纤激光器抽运掺氧化镁的周期性极化铌酸锂(PPMgLN)晶体实现3.81 μm输出的中红外连续波(cw)单谐振光学参变振荡器(OPO)。单谐振OPO通过e→e+e相位匹配，基于50 mm长，28.5~31.5 μm多周期的PPMgLN晶体(MgO掺杂摩尔分数为5%)，选用其中29.5 μm的周期，采用了两镜线性腔结构。在30 ℃的工作温度下，通过49 W的线偏振激光抽运，获得了最大功率4.25 W，波长为3.81 μm的闲频光输出，抽运阈值为5 W，其对应量子转换效率为31.1%。实验还通过改变PPMgLN晶体的工作温度21~170 ℃，获得了中红外波长3. 65~3.82 μm激光输出，测量了相应OPO的输出光谱。通过对比实验所测得中红外光输出波长与两组不同的理论计算结果，发现当晶体工作温度大于110 ℃后，实验测量结果与理论计算结果有一定的偏差，这和实验中晶体在高温区控温精度有一定的关系。

A continuous-wave (cw) singly resonant optical parametric oscillator (OPO) with the wavelength of 3.81 μm is obtained by pumping the periodically poled MgOLiNbO3 (PPMgLN) crystal with a homemade Yb single-mode fiber laser at 1064 nm. The laser uses the all optical master oscillator power amplifier (MOPA) structure. The cw singly resonant OPO used the e→e+e phase matching in crystal. The PPMgLN is 50 mm long and the period is from 28.5 μm to 31.5 μm. The cavity is formed of two mirror linear strusture. Pumped by the 49 W linear polarized ligth field at 30 ℃, the idler light 3.81 μm is obtained. It′s maximan power can reach 4.25 W. The threshold value of the pumping laser power is 5 W, corresponding to the output efficiency of 31.1%. When the temperature of the PPMgLN is changed from 21 ℃ to 170 ℃, the wavelength of the output laser changes from 3.65 μm to 3.82 μm. And the corresponding spectrum of OPO is measured. The experiment results are different from the theoretical results when the temperature of the PPMgLN exceeds 110 ℃.