Patent ID: 7746913

Claim:
An apparatus comprising: a line narrowed pulsed excimer or molecular fluorine gas discharge laser system comprising: a seed laser oscillator producing an output comprising a seed laser output light beam of pulses comprising: a first gas discharge excimer or molecular fluorine laser chamber; and a line narrowing module within a first oscillator cavity; 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 system output light beam of pulses, comprising: a ring power amplification stage including a beam expander; and a seed injection mechanism comprising: a first partially reflecting optical element through which the seed laser oscillator output light beam is injected into the ring power amplification stage, the partially reflecting optical element transmitting the seed laser output laser pulse beam onto a maximally reflective mirror oriented to reflect the seed laser output beam into the ring power amplification stage; the first partially reflecting optical element comprising a beam splitter; and a second optical element comprising a mirror selected for maximal reflection of the nominal center wavelength of the seed oscillator laser output pulses.