Optical suitability of window materials for CO(2) lasers

An experimental technique is reported for the measurements of the absorption coefficients of the candidate window materials for the CO(2) lasers. This technique is capable of measuring optical losses ~0.05% per transit. The optical suitability of Ge, GaAs, CdTe, ZnSe, NaCl, and KCI for the windows of the CO(2) lasers is investigated. Since these materials have varying mechanical properties, the thickness of a window is so chosen that it does not fracture or introduce significant optical distortion in the laser beam when subjected to a pressure of 1 atm across it. Surprisingly, from optical considerations, the ZnSe emerges as the best window material, although KCl has lower absorption coefficient, and Ge and GaAs are mechanically stronger.