Patent ID: 8116348

Claim:
A gas laser device comprising: two substantially parallel electrode plates forming a waveguide operable to focus and reflect a laser resonator beam; excitation means operable to cause a gas discharge; first and second reflecting means facing each other between the electrode plates to form a resonator, respective radii of curvature and a separation of the first and second reflecting means being such that the resonator in the free space plane parallel to the electrode plates is unstable and substantially confocal, and wherein said second reflecting means has a hard edge and has a radius of curvature in the free-space unstable direction that is greater than the radius of curvature of the first reflecting means; and third reflecting means, physically distinct from the first and second reflecting means, directing light through an additional waveguide element to an exit of the gas laser; wherein the additional waveguide element is external to the resonator and located between the third reflecting means and the exit of the gas laser, wherein the third reflecting means is adjacent one end of the resonator and the exit of the gas laser is adjacent an opposite end of the resonator.