Excimer laser cavities generally are
somewhat under a meter long. The standard stable resonator generates
a fairly large, divergent beam because of the high gain of excimers.
Optional unstable resonator optics give smaller and more uniform
beams, but those qualities may come at the cost of reduced output
power. Another possible configuration is the master oscillator—power
amplifier (MOPA) arrangement shown in Fig. 13.2 (often called