高平均功率电光开关晶体热畸变分析

Thermal distortions of electro-optic crystal for high average power laser systems

深入分析了方板构型的电光开关晶体在高功率载荷条件下的热畸变行为,讨论了光强分布对热效应的影响。以KDP晶体为例,分别计算了激光束光强为高斯分布和均匀分布时晶体的温升、相应的热应力分布、波前畸变以及热退偏。结果表明,光强的分布形式对波前畸变和热退偏的影响是不同的。相对于光强均匀分布的激光束,高斯光束减缓了光斑边沿处的温度梯度,产生的热应力较小,因此可以减弱热退偏效应;另一方面,在光束口径范围内,高斯光束产生了附加的温度分布非均匀性,因而波前畸变会大一些。

Thermally induced birefringence and optical distortion in electro-optic slab switches were analyzed, and the influence of distribution of intensity on thermal effects was discussed. The distribution of temperature increment, thermal stress, optical distortion and depolarization were calculated in the case of different intensity profiles （Gaussian and uniform） with KDP crystal as an example. The results indicate that the influence of nonuniformity of a light beam is significant on optical distortion and depolarization. For Gaussian light beams the depolarization is considerably lower because they mitigate the temperature gradients on the edge of the light beam, while the optical distortion is considerably larger against the spatially uniform light beam because Gaussian light beams have larger nonuniformity of temperature inside the clear aperture.