Gas discharge laser line narrowing module

A line narrowed gas discharge laser system and method of operating same is disclosed which may comprise a dispersive center wavelength selective element; a beam expander comprising a plurality of refractive elements; a refractive element positioning mechanism positioning at least one of the refractive elements to modify an angle of incidence of a laser light beam on the dispersive center wavelength selection element; each of the dispersive center wavelength selection element and the beam expander being aligned with each other and with a housing containing at least the dispersive center wavelength selection element; a housing positioning mechanism positioning the housing with respect to an optical axis of the gas discharge laser system. The dispersive element may comprise a grating and the beam expander may comprise a plurality of prisms. The housing may contain the dispersive center wavelength selective element and the beam expander. The housing positioning element may comprise a position locking mechanism.