US Patent 8624209 Controlling spatial properties in an excimer ring amplifier

A deep ultraviolet light source includes a master oscillator producing a seed light beam; a regenerative ring amplifier receiving the seed light beam from the master oscillator and outputting an output light beam, the regenerative ring amplifier including a set of optical components that define a plane of a closed ring; and a divergence control device within the master oscillator or between the master oscillator and the regenerative ring amplifier and configured to reduce a divergence of the output light beam along a normal direction, the normal direction being perpendicular to the plane of the ring.