Thermal deformation of high absorption chrome plated mirror irradiated by laser

In order to analyze the effect of thermal deformation of the mirror irradiated by laser beam on the beam quality, thermal-static structural coupled model of high absorption chrome plated mirror irradiated by laser beam with the incidence angle of 45° is built. Thermal deformation under different irradiation laser and the influence of mirror thickness on the deformation are analyzed. Then thermal deformation is detected with Hartmann wavefront sensor on free boundary condition. The results show that thermal deformation increases approximately linearly with the increase of the power absorbed at the range of 0.085-0.185 W. When the diameter of the facula increases, the deformation decreases. When mirror's thickness keeps in the range of 1~5 mm, the deformation merely keeps constant. In the initial stage of laser irradiation, the temperature and deformation increase rapidly. After 20 s, the increase of temperature on the mirror becomes slowly. The deformation increases to 0.27 μm in 1 s, and then increase slowly. The deformation will reach balance after 100 s. When the irradiation laser is removed, the mirror will return to the initial state after 120 s. The analysis result shows that the testing error is mainly caused by the error of the diameter of the facula and the incident angle of the laser.