报道了采用1064 nm激光抽运PPMgLN晶体准相位匹配(QPM)技术实现高效率2.7 μm激光输出的实验结果, 理论计算了PPMgLN晶体准相位匹配周期调谐曲线, 得出PPMgLN晶体周期为31.3 μm时可获得中红外波长2.7 μm激光输出。PPMgLN晶体(MgO掺杂摩尔分数为5%)单谐振光参量振荡(OPO)技术采用e→e＋e相位匹配, 消除了光束之间的走离效应并利用了PPMgLN晶体的最大非线性系数d33(27.4 pm/V)。在1064 nm激光抽运功率为26 W, 声光Q开关工作频率为7 kHz的条件下, 获得平均功率为4.7 W, 波长为2.72 μm激光输出, 斜率效率超过21％, 对应闲频光波长1.75 μm激光输出功率约9 W。2.7 μm激光水平方向和垂直方向光束质量M2因子分别为2.05和1.84。

Experimental results of high-efficiency 2.7-μm laser is demonstrated on quasi-phase-matched single-resonated optical parametric oscillator (OPO) in PPMgLN (5% MgO-doping) pumped by 1064-nm laser. Theoretical analyses of PPMgLN grating period tuning are presented. When grating period is 31.3 μm, a PPMgLN OPO could get output at wavelength of 2.7 μm. The pump beam polarization matches the e→e＋e interaction in PPMgLN, thus maximal nonlinear coefficient d33 (27.4 pm/V) is effective and walk-off of beams can be avoided. When pump power is 26 W with repetition rate of 7 kHz, an average output power of 4.7 W at wavelength of 2.72 μm is obtained with slope efficiency of more than 21%, and 9 W at the corresponding idler wavelength of 1.75 μm. The M2 factors of 2.7-μm laser are 2.05 and 1.84 in parallel and perpendicular directions, respectively.