Optical distortion of heated mirrors in CO2-laser systems

Using the model of an elastic half-space, the behavior of the reflecting mirror surface under the action of CW high-power CO2-laser beams is considered. The temperature and the stress fields on the mirror surface are calculated. The three critical intensity values corresponding to the three regions of the mirror optical distortion are determined. It is shown that, when optical distortion is to be minimized, the elastic deformation is of great importance at laser flux densities two or three orders of magnitude smaller than those necessary to melt the material of the mirror. The magnitude of the mirror surface normal displacement is experimentally determined. The calculations are found to agree with the experimental data.