High power CO2-laser optics have been investigated with respect to their thermal runaway and thermal distortion characteristics. It is shown that for highest power densities GaAs is the best choice as a transmitting optic while Copper and Molybdenum are best suitable for high reflective optics.
Manfred R Berger,
Herman E. Reedy,
"Optics For High Power CO2-Lasers", Proc. SPIE 0455, Industrial Applications of High Power Lasers, (19 March 1984); doi: 10.1117/12.966206; https://doi.org/10.1117/12.966206