通过对角锥棱镜腔实现KTPⅡ类非临界相位匹配光参量振荡的理论分析,发现腔内存在特殊偏振方位角的本征模式,其满足Ⅱ类非临界相位匹配条件。实验上不但实现了该腔的Cr4+:YAG被动调Q内腔式光参量振荡器(OPO)运转,而且得到了优于平-平腔的转换效率,改善了信号光的稳定性。分析了Cr4+:YAG初始透过率和腔内功率密度的关系,实验获得不同Cr4+:YAG初始透过率、抽运能量和信号光能量的关系曲线。通过腔内功率密度的优化,电光效率高达0.25%,设计出结构紧凑、小型高效的工程实用光参量振荡器器件,抽运能量阈值为4.7 J,输出能量为11.8 mJ,脉宽为6.9 ns,发散角为7 mrad,能量稳定性为5%。

The theory of the non-critical phase-matched KTPⅡcrystal placed in corner-cube resonator was discussed. It was found that there existed eigen mode of special polarization azimuth to meet the non-eritical phase-matched condition. Experiment based on Cr4+:YAG passively Q-switched intracavity optical parametric oscillator (OPO) was performed, and the conversion efficiency was higher than that in the plane-parallel resonator. The effects of the transmission of Cr4+:YAG crystal upon the intracavity power density were analyzed, and the relationship of signal-pulse energy versus pump energy with different transmission of Cr4+:YAG crystal was obtained. The performance of OPO laser was much better than that in plane-parallel resonator for the electro-optical efficiency can be up to 0.25%. A compact and efficient OPO was designed, the pump energy threshold was 4.7 J, the pulse energy was 11.8 mJ, the pulse width was 6.9 ns, the beam divergence was 7 mrad and the pulse stability was 5%.