Patent ID: 7885309

Claim:
A laser system comprising: a seed laser oscillator producing an output comprising a laser output light beam of pulses, the seed laser oscillator comprising a first gas discharge excimer or molecular fluorine laser chamber; and a laser amplification stage containing an amplifying gain medium in a second gas discharge excimer or molecular fluorine laser chamber receiving the output of the seed laser oscillator and amplifying the output of the seed laser oscillator to form a laser system output comprising a laser output light beam of pulses, the laser amplification stage comprising: a ring power amplification stage comprising a regenerative closed loop optical cavity defined in part by a partially reflecting optical element through which the seed laser oscillator output light beam is injected into the ring power amplification stage, the ring power amplification stage comprising a beam de-magnification stage and a beam expansion stage within the optical cavity; wherein the beam de-magnification stage is configured to de-magnify the laser beam as the laser beam travels from the partially reflecting optical element toward the amplifying gain medium and the beam expansion stage is configured to expand the laser beam as the laser beam travels from the amplifying gain medium toward the partially reflecting optical element.