针对激光二极管端面泵浦方形Yb∶YAG微片晶体产生的热效应问题, 运用半解析方法计算该晶体的温场分布。根据连续LD端面泵浦方形Yb∶YAG微片晶体的工作特性, 建立符合实际工作情况的热模型, 构造初始条件和边界条件。同时考虑到晶体的热导率是温度的函数, 并结合牛顿法求解热传导方程, 得到晶体温度场的一般解析表达式。定量分析了不同的泵浦功率、超高斯阶次、光斑半径、晶体厚度因素对变热导率方形Yb∶YAG微片晶体温度场的影响。结果表明: 使用泵浦功率为80 W、超高斯阶次为1、光斑半径为400 μm的泵浦光对含方形Yb∶YAG微片晶体质量分数为8.0%、晶体的尺寸为4×3×1 mm3进行泵浦, 将晶体的热导率视为常量和变量时, 泵浦端面获得的最大温升分别为41.25 ℃和52.14 ℃。研究结果对减小全固态Yb∶YAG晶体的热效应问题具有指导意义。

In order to study the thermal effect of Yb∶YAG crystal end-pumped by pulse laser diode(LD),the temperature distribution of crystal was calculated based on semi-analytic method. The crystal thermal model was built under the real work situation and the initial conditions and boundary conditions were established in this research, according to the working characteristic of square Yb∶YAG micro crystal end-pumped continuously by LD. Furthermore, considering the function relation between the coefficient of thermal conductivity and temperature and solving the heat conduction equation with Newton method, the temperature distribution was obtained. Finally, the influences of different factors such as the different pump power, super Gauss order, radius of spot, thickness of crystal on crystal were studied. The research results show that maximum temperature of Yb∶YAG crystal end-pumped surface is 41.25 ℃ and 52.14 ℃,respectively, under the different conditions that thermal-conductivity is constant and non-constant. And in that case, the first order super-Gaussian light was used,with the output power of 80 W and the spot radius of 400 μm, to pump the crystal with the mass fraction of 8% and the size of 4×3×1 mm3. It is very significant to reduce the thermal effect of full solid state Yb∶YAG crystal in this research.