ZnGeP2 OPO产生4.3 μm波段窄线宽激光实验研究

为了设计4.3 μm波段大功率窄线宽中红外激光器，开展了2.7 μm激光抽运ZnGeP2晶体光参量振荡(Optical Parametric Oscillation, OPO)技术产生4.3 μm波段窄线宽激光实验研究，对实验结果开展了详细的分析。抽运源为1064 nm抽运的KTiOPO4 OPO激光器输出的2.7 μm波段参量激光，KTiOPO4 OPO采用单谐振结构，将两块相同的KTiOPO4晶体光轴相向放置以补偿走离效应，KTiOPO4晶体按Φ=0°、θ=62°切割以获得波长2.7 μm波段激光输出，采用Ⅱ(B)类相位匹配（o→o+e）以利用较大的非线性系数。ZnGeP2 OPO采用单谐振结构，采用Ⅱ(B)类相位匹配（o→o+e）以获得窄线宽输出，ZnGeP2晶体按Φ=0°、θ=68°切割以获得波长4.3 μm波段激光输出。在抽运光波长2.7 μm，脉冲能量为7.5 mJ，脉宽8.6 ns的条件下，获得脉冲能量2.12 mJ，线宽30 nm，脉宽8.7 ns的4.26 μm激光输出，光-光转换效率约为28.3%，斜效率约为32.6%，水平和垂直方向的光束质量M2分别为6.2和13.5。
In order to design high-power narrow line width 4.3 μm laser, the narrow line width 4.3 μm laser was obtained by ZnGeP2 OPO (optical parametric oscillation) pumped by a 2.7 μm laser. Experimental results were analyzed in detail. The pump source was a 2.7 μm KTiOPO4 OPO laser pumped by a 1064 nm Nd:YAG laser, and the KTiOPO4 OPO was singly resonated. Two identical KTiOPO4 crystals were placed with opposite optical axis to compensate the walk off effect. The KTiOPO4 crystals were cut asΦ=0°,θ=62° to generate 2.7 μm wave band laser. To utilize the large effective nonlinear coefficient, the phase matching was based on type Ⅱ(B) (o→o+e). The ZnGeP2 OPO was singly resonated too. To output narrow line width laser, the phase matching is based on typeⅡ(B) (o→o+e).The ZnGeP2 crystal was cut as Φ=0°,θ=68° to generate 4.3 μm laser. The energy of the 2.7 μm laser is 7.5 mJ with a pulse of 8.6 ns and line-width 12 nm.The pulse energy of 2.12 mJ at 4.26 μm with an optical-optical conversion efficiency of 28.3% and a slop efficiency of 32.6% is obtained, and the pulse width is 8.7 ns, the line-width is 30 nm. The beam qualities M2 of horizontal and vertical directions are 6.2 and 13.5, respectively.