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为了减小激光辐照下反射镜镜面的热变形问题,建立了反射镜热变形的有限元分析模型。对不同制冷功率时的镜面热变形进行分析,然后针对吸收功率为50 W、光斑半径为镜体半径1/3时的TEM00模高斯光束对镜体结构进行优化,对优化后的反射镜在不同参数的TEM00模高斯光束和TEM10、TEM11模厄米特-高斯光束辐照下的热变形进行了分析。仿真结果表明,当施加滞后于激光辐照且与吸收功率近似大小的制冷时,有利于减小镜面热变形,且镜体最终会趋于相对稳定的热平衡状态。此外,当镜体背部切去一厚度为1.4 mm、内径为25 mm的环状区域时,热变形峰谷(PV)值仅为0.005μm;同时,优化后的镜体也可在一定程度上减小其他参数激光辐照下的镜面热变形的PV值。对于TEM00模高斯光束和TEM10、TEM11模厄米特-高斯光束,均满足光学系统对热变形的要求。
In order to reduce the thermal deformation of the mirror surface under laser irradiation, a finite element analysis model of the mirror thermal deformation was established. The mirror thermal deformation at different cooling power was analyzed. Then the TEM00 mode Gaussian beam with absorbed power of 50 W and spot radius of 1/3 of the mirror body was optimized for the mirror body structure. The parameters of the TEM00 Gaussian beam and TEM10, TEM11 mode Hermite-Gaussian beam irradiation thermal deformation were analyzed. The simulation results show that the mirror thermal deformation will be reduced when the laser is lagged and absorbed by the laser, and the mirror will eventually reach a relatively stable thermal equilibrium. In addition, the peak value of the thermal deformation peak (PV) is only 0.005 μm when the ring-shaped area with a thickness of 1.4 mm and an inner diameter of 25 mm is cut away from the back of the mirror body. At the same time, the optimized mirror body can also, to a certain extent, Reduce the other parameters of the laser irradiation of the mirror thermal deformation of the PV value. For the TEM00 mode Gaussian beam and the TEM10, TEM11 mode Hermitian-Gaussian beam, all meet the optical system requirements for thermal deformation.