级联晶体倍频器件温度适应性扩展研究

Research on Extending Temperature Acceptance Bandwidth of Second Harmonic Generation in Cascaded Crystals

级联晶体能有效扩展倍频器件的温度适用范围。在考虑空气色散的基础上推导出了级联晶体倍频过程中的能量转换效率公式。根据该公式,通过仿真计算出了级联两KTiOPO_4晶体倍频1064nm激光时转换效率随温度变化的特性,并进行了实验验证。实验结果表明:级联晶体中倍频光能量随晶体间距呈余弦分布,空气色散引起的相位失配量为2π的整数倍时,级联晶体的倍频温度特性最佳,最大转换效率可达47.9%,比单个KTP晶体倍频时的最高效率高12.9%,温度半宽度可达78℃,是单个KTP晶体倍频温度半宽度的两倍。提出的理论分析能合理解释级联晶体倍频过程中的实验现象,有助于提高倍频激光的温度稳定性。

Extending temperature acceptance bandwidth in second harmonic generation （SHG） by cascading nonlinear crystals is a simple and efficient method. Based on the dispersion of air, a formula describing how dispersion of air affect the conversion efficiency is derived. Based on the formula, conversion efficiency of SHG of 1064 nm in cascaded KTiOPO4 crystals versus temperature is simulated, and corresponding experiments are conducted. In the experiments, conversion efficient is cosine distribute versus the distance between two cascaded crystals, and when the phase mismatch caused by dispersion of air is integer times of 2π, the maximum conversion efficiency reaches 47.9%, which is 12.9% higher than the maximum conversion efficiency in a single KTP crystal, and the temperature acceptance bandwidth is 78 ℃, which is two times broader than that in a single KTP crystal. The theoretical analysis is in good agreement with the experimental results. The research conclusions are conducive to extending temperature acceptance bandwidth for nonlinear frequency conversion by cascading crystals.