Quartz glass (SiO2), silicon single crystal (Si) and molybdenum single crystal (Mo) have been tested for the cavity reflector of an argon excimer laser which supplies intense coherent radiation at 126nm. These mirrors have been used with a combination of a MgF2 output coupler. The laser output energy was found to be limited by damage threshold of the mirrors. The maximum output energy of 50mJ per pulse was obtained with the cavity composed of a Mo reflector and a MgF2coupler. No damage was observed on the Mo mirror surface. The duration of the laser output pulse depends on the argon gas pressure and also the reflectors. The mirror damage is discussed with relation to pulse shortening observed in high power rare-gas excimer lasers of Xe, Kr and Ar.
