Influence of thermal distortion in mirrors on the propagation of high power lasers

摘要

The root-mean-square (RMS) phase distortion and the strehl ratio in the far-field influenced by the thermal distortion of mirrors in the propagation of high power lasers were calculated. Calculations with different CO_2 laser beam intensity distribution indicate that compare with stable cavity whose output is Gaussian, unstable cavity's beam quality influenced by the thermal deformation depends on the slope of the intensity distribution, that is, contents of H_2O, and the obscuration. Among the mirror materials such as SiO_2, BeO, CaF_2 and Si, CaF_2 provides the steadiest thermal character in the high power laser irradiance. When the SiO_2 mirror is cooled, the RMS phase aberration brought by the thermal deformation would be less. For a high power mirror, cooled by the water is more efficacious than cooled by the wind.