基于推导的倍频晶体匹配角与温度关系的理论分析,揭示了温度对频率转换过程影响的热光物理机制。数值模拟了频率转换过程中二倍频与三倍频晶体的匹配角热敏感性。由于不同晶体材料热敏感性的差异性,实验获得了激光装置中所用晶体材料的匹配角随温度变化的关系曲线。理论分析了不同输入功率密度情况下匹配角失谐对三倍频过程的影响,并在线验证了温度变化导致匹配角失谐,进而引起三倍频转换效率的下降。根据实验获得的晶体匹配角的热敏感性参数,提出利用晶体角度跟随方法进行三倍频转换效率补偿,实现了三倍频能量的稳定输出。

Based on the analytical solution of the dependence of phase matching angle on the crystal temperature, we illustrate the thermo-optic physical mechanism of temperature influence on the frequency conversion. The thermal sensitivity of the doubler and tripler crystals are numerically simulated respectively. Due to such sensitivity discrepancy among various crystals, the phase matching angle curve regarding the crystal temperature variation in our laser facility is obtained in experiment. The influence of PM angular detune on frequency conversion is theoretically analyzed under different input intensities, which is demonstrated by the conversion efficiency decline induced by temperature variation. According to the thermal sensitivity parameter obtained in experiments, we compensate the conversion efficiency with the crystal angle following, resulting in stable output of third harmonic energy.