Finite-element-method study of the thermal distortions of deformable mirrors for laser systems

In order to analyze thermal distortions of the deformed mirror for laser systems, the finite element model of a 417-element deformable mirror was built. The deformation, temperature rising and high-order aberrations were calculated after applying the laser irradiation to the mirror. Based on the results, we found the distortions became larger and larger while the absorption of multilayers increasing. When the mirror thickness is 1 mm, the deformation and temperature rising were 0.370 μm and 6.68 ℃ respectively. The PV decreased from 0.370 μm to 0.256 μm when the mirror got thicker from 1 mm to 3 mm, and the corresponding removed low-order Zernike coefficient residual error was reduced from 0.285 μm to 0.145 μm. The high-order aberrations of the deformed mirror were little when the mirror surface thickness was 3 mm. The results have practical engineering application for the design of deformable mirrors for laser systems.