基于热传导方程和热弹方程,利用有限元分析方法,就光斑尺寸远大于或接近于基底材料热扩散长度的情况以及反射镜在固定或自由的边界条件下,分别计算了硅和石英两种基底材料多层膜红外连续激光反射镜的最大温升、最大形变及最大热应力,并探讨了它们随光斑尺寸的变化规律.结果表明:在自由边界条件下,反射镜表面的最大轴向位移与光斑半径之间近似为线性关系;而在固定边界条件下,反射镜的最大热应力与光斑半径之间近似为线性关系;反射镜的夹持状态对最大轴向位移及最大热应力的影响随着光斑尺寸的增加而增强;在相同的入射激光光源及相同的边界条件下,硅镜具有较低的温升值或较高的抗热损伤阈值,而石英镜具有较好的抗热畸变特性.

Based on the thermal conduction equations and thermal-elastic equations, while the laser speckle radius on the reflectors are much larger than or almost approximate to the thermal diffusion lengths of the substrate materials, and while the reflectors boundaries are constrained or unconstrained, the maximum temperature rise, thermal distortion and thermal stress of silicon- or silica-based multi-layered infrared CW laser reflectors are calculated by a finite element analysis method. And the dependences of these parameters on the laser speckle radius is discussed. The results indicate that the ultimate axial displacements on the surfaces of the reflectors are approximately linear with the incidence beams radius while the reflectors have unconstrained boundarties, but the ultimate thermal stress in the reflectors are approximately linear with the radius for constrained boundaries. The influences of the reflector tackling states on these two parameters increase while the beam radius increases. Irradiated by the same laser sources and under the same boundary conditions , thesilicon reflectors have lower temperature rise or higher thermal damage threshold but higher thermal distortion ratio than the silica ones.