基于非线性光学的频率变换理论,采用双块磷酸氧钛钾(KTP)晶体外腔正交倍频的方式产生二次谐波以提高基频光的倍频转换效率。用长度分别为6 mm,8 mm,15 mm的三块KTP晶体进行实验,比较了双块KTP晶体正交和平行串接以及单块KTP晶体的倍频特性,得到几组倍频转换效率随基频光功率密度变化的曲线。实验结果表明,采用双块KTP晶体倍频的倍频激光器能够有效地提高绿光激光器的动态范围且在520～750 MW/cm2,双块KTP晶体正交串接倍频比长度是两块晶体之和的单块长KTP晶体的倍频转换效率高近30%。

Two KTP crystals outside the cavity are used to generate the second harmonic wave with quadrature arrangement based on nonlinear optical frequency transform theory to increase the harmonic conversion efficiency. Three pieces of KTP crystal with length in 6 mm, 8 mm, 15 mm are respectively used in experiments. The results of a scheme of two-piece KTP crystal orthogonal or parallel tandem with monolithic KTP are compared and several groups of harmonic conversion efficiency with fundamental power density are obtained. The result shows that two-piece KTP tandem laser has high dynamic range and it is superior to monolithic ones. Two-piece KTP orthogonal tandem has nearly 30% higher conversion efficiency than monolithic one with the same length from 520～750 MW/cm2.