Patent ID: 7643528

Claim:
An apparatus comprising: a pulsed gas discharge laser lithography light source comprising: a seed laser portion providing a seed laser output light beam of seed pulses; an amplifier portion receiving the seed laser output light beam and amplifying the optical intensity of each seed pulse to provide a high power laser system output light beam of output pulses; a pulse stretcher increasing the number of peaks in the output pulse and decreasing the average peak intensity of each of the output pulses by passing the output pulses through a pair of optical delay paths in series; the pulse stretcher comprising: a first beam splitter operatively connected with the first delay path and a second pulse stretcher operatively connected with the second delay path; a first optical delay path tower containing the first beam splitter; a second optical delay path tower containing the second beam splitter; one of the first and second optical delay paths comprising: a plurality of mirrors defining the respective optical delay path including mirrors located in the first tower and in the second tower; the other of the first and second optical delay paths comprising: a plurality of mirrors defining the respective optical delay path including mirrors only in one of the first tower and the second tower.