Based on the mass fraction of 65% deuterated DKDP crystals, the fourth harmonic conversion of 1053 nm laser is realized under the condition of noncritical phase matching (NCPM). The experimentally measured crystal temperature is 29.4 ℃ and the acceptance angle width of the crystals under the NCPM condition is around 55 mrad. Effects of the deuterated amount and the temperature of the DKDP crystals in the process of NCPM on the fourth harmonic conversion are theoretically analyzed. The relationship between the deuterated amount and temperature and the changing of the fourth harmonic conversion efficiency versus the double frequency light intensity are numerically simulated. These results provide a theoretical basis for the application of fourth harmonic laser in the high power laser system.

利用质量分数为65%的掺氘DKDP晶体实现了1053 nm激光在非临界相位匹配(NCPM)条件下的四次谐波转换，实验测得NCPM条件下晶体温度为29.4 ℃、晶体接收角宽约为55 mrad。理论分析了NCPM过程中DKDP晶体掺氘量和温度对四次谐波转换的影响，数值模拟了四次谐波转换过程中晶体掺氘量和温度的关系以及四倍频转换效率随倍频光强的变化，这些结果为四倍频光在高功率激光系统中的应用提供了理论依据。

从理论上计算了由于光束倾斜入射产生的棱镜起偏系统角谱宽度的压缩效应，计算结果表明，入射光束相对于棱镜入射面的入射角越大对角谱宽度的压缩就越明显，不同材料的基底折射率的差别对角谱宽度的压缩影响不大。通过举例从膜系设计的角度进一步论证了这一结论。还指明在实际系统中可以保持入射光束的相对角度不变的情况下，通过改变棱镜的形状来达到倾斜入射的目的从而实现角谱宽度的压缩。对如何设计出高性能的宽角宽光谱偏振分束镜具有重大的指导意义。

本文从单色平面波无吸收损耗三频耦合波方程,小信号近似出发,计算了KDP、ADP、BBO、LiIO_3和LiNbO_3等晶体(1.064μm激光倍频、三倍频、四倍频)的光谱和角度接收半宽Δλ_A、Δθ_(FW),从而为选择宽频带激光频率转换所用的晶体及匹配类型提供了依据。给出了宽频带锁模激光倍频方程,并得出窄频带下二次谐波加强因子(2N~3+N)/3,表明边带和频作用对锁模激光脉冲具有更大的贡献。