第三类热边界条件对激光晶体热效应的影响

以各向异性半解析热分析理论为基础,研究矩形横截面Nd:YVO4激光晶体在有第三类热边界条件工作时,激光晶体温度场分布和晶体抽运面热形变分布.通过激光晶体工作特点分析,建立符合激光晶体工作状态的热模型.利用各向异性介质热传导方程的半解析求解方法,得出了矩形截面Nd:YVO4晶体的温度场、端面热形变场的通解表达式.研究结果表明:当使用输出功率为15 W半导体激光器端面中心入射Nd:YVO4晶体(晶体掺钕离子质量分数为0.5%)时,在抽运端面中心获得499.5 K最高温度和0.99 μm最大热形变量.和将第三类热边界条件近似为第二类热边界条件的通用做法相比更准确.这种方法可以应用到其它激光晶体热问题研究中,为有效解决激光系统热问题提供了理论依据.

Influence of the Third Thermal Boundary Condition on the Thermal Effect of Laser Crystal

Based on the analytical theory of aeolotropy,thermal distortion and temperature field distributions of Nd : YVO_4 crystal with rectangular section were investigated when the third thermal boundary condition was considerated. By analyzing the working characteristics of the Nd:YVO_4 laser crystal,a thermal model that accords with the working state of the laser crystal was established. Using a kind of new solution to sovle the heat conduction equation of the anisotropic medium, general solution expressions of the temperature field and the thermal distortion field of Nd :YVO_4 crystal with rectangular section were obtained. The results show that a maximum temperature rise of 499. 5K and a maximum thermal distortion of 0. 99 μm can be obtained in the center of the pump face when the Nd : YVO_4 laser crystal is pumped by a Diode Laser with a output power of 15 Watt from the center of end face (the weight percent of neodymium ion doped in the crystal equals 0. 5% ). This method is more accurate compared with those in which the third thermal boundary condition is approximatively regarded as the second thermal boundary condition. And this method can also be applied to the research on the other thermal problems of laser crystal and offer theoretical basis for effectively solving the thermal problems in laser system.