报道了一个低阈值宽调谐、被动调Q、单谐振掺MgO的周期性极化铌酸锂晶体(PPMgLN)光学参量振荡器。利用被动调Q的Nd:YVO₄激光器作为泵浦源,采用外腔结构,在室温下,实现了PPMgLN晶体的准相位匹配光学参量振荡。光参量振荡的阈值仅为0.27 W(单脉冲能量4.5 μJ、脉宽35 ns);在泵浦光为135 W(脉冲能量8.2 μJ、脉宽35 ns),PPMgLN周期为31 μm时,获得了161.9 mW,3.202 μm脉冲激光输出;同时获得了98.5 mW的1.594 μm信号光输出,总的光-光转化效率达到19.3%。通过改变晶体的周期,实现了闲频光3.13~4.19 μm,信号光1.43~1.65 μm的宽带可调谐激光输出。

A wide-tunable,low-threshold,extra-cavity singly resonant optical parametric oscillator(OPO) has been reported,which is based on periodically poled MgO:LiNbO3 (PPMgLN). The OPO system,compact and simple,adopts a passively Q-switched Nd:YVO₄ laser as the pump source and realizes quasi-phase-matched optical parametric oscillation at room temperature. The threshold value of the OPO system is only 0.27 W (single pulse energy of 4.5 μJ,pulse duration of 35 ns) at 1 064 nm. When the pump power is 1.35 W (pulse energy of 8.2 μJ,pulse duration of 35 ns),an idler output power of 161.9 mW at 3.202 μm,and a signal output power of 98.5 mW at 1.594 μm have been achieved,and this corresponds to a whole (idler+signal) optic-optic conversion efficiency of 19.3%. By shifting the PPMgLN crystal,the periods of the domain structure on the PPMgLN wafer can be changed,thus enabling a wide idler spectral tuning range from 3.13 to 4.19 μm,and a wide signal spectral tuning range from 1.65 to 1.43 μm.