Gas discharge laser, especially excimer laser, for producing low divergence radiation has stable resonator with output coupling mirror surface parallelity better than 5 seconds of arc

摘要

The gas discharge laser has a stable resonator (10) whose output coupling mirror (14) surface parallelity is better than 5 seconds of arc. The output coupling mirror surface parallelity can be better than 5 seconds or better than 1 second. One surface of the output coupling mirror is provided with a coating whose degree of reflection is at least 6 per cent.