Abstract

Optical damage is a serious problem in highpower operation of short-wavelength lasers. Using a high-power argon excimer laser with a MgF₂ output mirror of 70% transmittance, we are investigating the feasibility of various materials for the cavity mirrors. SiO₂ glass, Si single crystal, and Mo single crystal have great potential in short-wavelength lasers. At 126 nm, the measured reflectivities were 80% for MgF₂/AI of a conventional mirror, 14% for SiO₂, 20% for Si, and 17% for Mo. These values were different from the reflectivities calculated by reported optical constants. The scattering loss due to surface roughness might cause significant degradation in their performance especially in this spectral region. A MgF₂/AI mirror damaged at ~1 MW of the output power, and SiO₂ led to ~5-MW performance but with a slightly damaged surface. Si and Mo allowed the high-power operation more than 3 MW without any surface damage. Since Mo keeps high reflectivity down to 60 nm, it is feasible for the cavity mirror of extreme ultraviolet lasers.

© 1986 Optical Society of America