BaGa4Se7(硒镓钡，简称BGSe)与KTiOAsO4(砷酸氧钛钾，简称KTA)均可在1.06 μm激光泵浦下产生中红外激光。首先仿真计算出两种非线性晶体的相位匹配曲线，结果显示：切割角为(56.3°, 0°)的BGSe晶体在I类相位匹配条件下和切割角为(90°, 0°)的KTA在II-A类相位匹配条件下均可产生~3.5 μm的闲频光。然后理论计算出BGSe (56.3°, 0°, I类)的有效非线性系数为-11.9 pm/V，KTA(90°, 0°，II-A类)的有效非线性系数为-3.2 pm/V；在其他条件相同的情况下，15 mm长BGSe (56.3°, 0°, I类) 的OPO振荡阈值是20 mm长KTA (90°, 0°, II-A类) OPO振荡阈值的35.11%。最后通过实验验证BGSe (56.3°, 0°, I类, 15 mm) 的振荡阈值小于KTA(90°, 0°, II-A类, 20 mm)，输出的中红外激光能量大于KTA。因此，BGSe是一种极具应用前景的中红外非线性晶体。

Both BaGa4Se7 (BGSe) and KTiAsO4 (KTA) can generate mid-infrared lasers pumped by 1.06 μm laser. Firstly, the phase matching curves of two kinds of non-linear crystals were simulated and calculated. The results show that BGSe with cutting angles of (56.3°, 0°) and KTA with cutting angle of (90°, 0°) can generate idle frequency light of ~3.5 micron under phase matching conditions of type I and type II-A, respectively. Then through theoretical calculation, the effective non-linear coefficients of BGSe (56.3°, 0°, type-I) is ?11.9 pm/V, and that of KTA (90°, 0°, type II-A) is ?3.2 pm/V. The OPO oscillation threshold of 15 mm long BGSe (56.3°, 0°, type-I) is 35.11% of that of 20 mm long KTA (90°, 0°, type II-A). Then, the experimental results show that the oscillation threshold of BGSe-OPO (56.3°, 0°, type-I, 15 mm) is smaller than that of KTA-OPO (90°, 0°, type-II-A, 20 mm). The output energy of BGSe (56.3°, 0°, type-I) is larger than that of KTA (90°, 0°, type II-A). Therefore, BGSe is a promising mid-infrared non-linear crystal.