An apparatus and method are disclosed for operating a
narrow band short
pulse duration gas
discharge laser output light
pulse beam producing
system, producing a beam comprising
laser output light pulses at a selected pulse repetition rate, which may comprise: a dispersive center
wavelength selection optic selecting at least one center
wavelength for each pulse determined at least in part by the
angle of incidence of the
laser light
pulse beam containing the respective pulse on the dispersive
wavelength selection optic; a tuning mechanism operative to select at least one
angle of incidence of a first spatially defined portion of the
laser light pulse beam containing the respective pulse upon the dispersive center wavelength selection optic; and, the tuning mechanism comprising a variably refractive optical element defining a plurality of refractive angular displacements of the first spatially defined portion of the
laser light pulse beam passing through the variably refractive optical element at one of a plurality of positions of incidence of the
laser light pulse beam on the variably refractive optical element. The variably refractive optical element may comprise: a first generally flat face defining a surface of incidence for the laser light pulse beam; and, a second multifaceted or curved face defining a plurality of generally flat surfaces of exit or a continuously varying surface of exit for the laser
light beam. Other aspects of
pulse parameter metrology and pulse modulation control, including in response to signals from the utilization tool are disclosed, e.g., relating to proper
dose control with differing center wavelength spectra.