为了克服线性模型在描述高功率运转的激光晶体时, 热焦距和热致双折射计算值与实测值不符的缺点, 采用非线性热传导模型, 计算了常用[111]切割方向Nd∶YAG激光晶体的热致双折射椭圆分布以及径向和切向热焦距。进行了平均热焦距数据测量和旋转线偏振光干涉实验, 实验结果与理论分析吻合。结果表明, 非线性模型对Nd∶YAG激光晶体在高功率运转时的描述更符合实际情况, 普适性更强。这一结果对于设计高功率径向或切向偏振固体激光器是有帮助的。

To overcome the shortage of mismatch of the calculated value and the measured value of thermal induced birefringence and thermal focal length when applying linear heat conduction model to describe a laser crystal operating in high power, based on nonlinear heat conduction model analysis, the distribution of the thermal induced birefringence ellipse and the radial or tangential thermal focal length in a Nd∶YAG laser crystal of common [111]-cut were analyzed. The average thermal focal length data and rotated interference pattern of linearly polarized light were measured. The experimental results fit the theoretical analysis. The results show that nonlinear model provides more realistic and more general description for an Nd∶YAG laser crystal in [111]-cut. The result is helpful for the design of radial or tangential polarized high power solid-state lasers.