Providing a high peak power short pulse duration gas discharge laser output pulse comprises a pulse stretcher a laser output pulse optical delay initiating optic diverting a portion of the output laser pulse into an optical delay having an optical delay path and comprising a plurality of confocal resonators in series aligned to deliver an output of the optical delay to the laser output pulse optical delay initiating optic. The plurality of confocal resonators comprises four confocal resonators comprising a twelve pass four mirror arrangement. An apparatus and method may comprise a plurality, e.g., two pulse stretchers in series and may include spatial coherency metrology.