平均功率普克尔盒热效应数值模拟及应力双折射补偿

Simulation of thermo-effects in average-power Pockels cell and stress-induced birefringence compensation

高能重复频率运转条件下,用作激光隔离、多程放大控制的关键单元普克尔盒遇到了通光口径限制与热效应的双重挑战。在分析电光晶体由于光吸收引起的温度场应变场的基础上,给出电光开关应用于平均功率激光系统中时,透射激光的波前畸变及退偏损耗。当入射激光为50 J\10 Hz,光束口径为60 mm×60 mm,填充因子为0.8时,波前畸变峰谷值为0.22λ,最大退偏损耗为3.7%。最后针对纵向电光效应等离子体电光开关,提出了热应力双折射补偿的方案。结果显示:补偿后的电光开关消除了热引起的退偏损耗,同时驱动电压为传统纵向电光效应半波电压的一半,降低了输出高电压脉冲电光开关驱动电源的设计难度。

For high-energy and repetition-rate laser system application, Pockels cell, which is used for isolation or multipass amplifying and controlling, encounters the challenges of both aperture limitation and thermo-effects. Based on analyzing the temperature and strain distribution in electro-optic crystal, wavefront distortion and depolarization loss were studied for average power application. When the incident laser is 50 J, 10 Hz, 60 mm±60 mm clear aperture, with fill factor of 0.8, the peak-valley value was 0.22 λ, and the maximum depolarization loss reached 3.7%. Additionally, compensation schemes were proposed to compensate for stress-induced birefringence in longitudinal DKDP optical switch. The results show that the depolarization loss, induced by thermo-stress birefringence, is completely removed by use of the compensation scheme. The slaving voltage is reduced to one-half of the half-wave voltage for longitudinal electro-optic effect. Therefore, the design difficulty of optic switch＇s power supplies, whose output voltage is high, will be lowered.