通过1064 nm激光抽运KTP晶体内腔光参量振荡(OPO)技术获得了近衍射极限的2.68 μm激光输出,对实验结果开展了详细的分析。抽运源为声光调Q Nd:YAG激光器,光参量振荡器谐振腔采用双谐振结构,将两块相同的KTP晶体光轴相向放置以补偿走离效应,KTP晶体按φ=0°,θ=62°切割以获得波长2.7 μm激光输出,采用Ⅱ类相位匹配(o→o+e)以利用较大的非线性系数。在808 nm激光二极管抽运功率为330 W,声光Q开关工作频率为7 kHz的条件下,获得平均功率7.6 W,波长2.68 μm激光输出,光束质量因子M2小于1.6,对应信号光1.765 μm激光输出功率约14 W。

Near diffraction limit 2.68 μm laser is obtained by intracavity KTP optical parametric oscillation (OPO) pumped by a 1064 nm laser.The experimental results are analyzed in detail.The pump source is an acousto-optical Q-switched Nd:YAG laser,and the OPO is doubly resonated.Two identical KTP crystals are placed with opposite optical axis to compensate the walk-off effect.The crystals are cut as φ=0°,θ=62° to generate 2.7 μm laser.To utilize the large effective nonlinear coefficient,the phase-matching is based on typeⅡ (o→o+e).When the pump power of the 808 nm laser diode is 330 W with a repetition rate of 7 kHz,an average output power of 7.6 W at 2.68 μm is obtained.The output power of the corresponding signal laser of 1.765 μm is about 14 W and the beam quality factor M2 of 2.68 μm laser is less than 1.6.