NEAR DIFFRACTION-LIMITED OUTPUT FROM A 100 NS XECL LASER FITTED WITH A PHASE-UNIFYING-CAVITY

The performance of a long pulse XeCl laser, fitted with a negative bra nch unstable cavity using a phase-unifying (PU) mirror as output coupl er, has been investigated. Laser beams with a divergence close to the diffraction limited value and with a relatively uniform intensity prof ile have been extracted by using an unstable cavity with magnification factor M = 2. It is shown that PU-unstable cavities are quite peculia r tools with respect to hard-edge unstable cavities, mainly for active media having a large cross section and requiring low magnification fa ctors. Indeed, the beam divergence is increased by about 50% by replac ing the phase-unifying mirror with a hard-edge aluminized mirror.