High resolution etalon-grating spectrometer

A narrow band ultraviolet laser system comprising:

• A) a narrow band excimer laser having a wavelength control mechanism capable of scanning output wavelength over a range of at least several picometers,
• B) a pressure containment,
• C) an etalon optical unit contained in said pressure containment configured to monitor a beam of narrow band ultraviolet light and to produce interference fringes, said etalon optical unit comprising:
• 1) a diffuser positioned to diffuse said light into a very large number of directions to produce a diffuse beam;
• 2) an etalon positioned in the path of said diffuse beam;
• 3) a first slit aperature;
• and
• 4) a lens unit positioned to collect light passing through said etalon and to focus a portion of the passing light through said first slit aperture,
• D) a grating unit comprising:
• 1) a collimating optical unit positioned to collect light passing through said first slit aperture,
• 2) a grating positioned in an approximately Littrow configuration to reflect said collimated light back through said collimating optical unit so that spectral components of reflected light are focused by said collimating optical unit at positions dependent on wavelength of said spectral components,
• 3) a second slit aperture,
• 4) a mirror positioned to reflect through said second slit aperture a portion of said light passing back through said collimating optic,
• 6) a light monitor positioned to monitor light passing through said second slit aperture, and
• E) a gas contained in said pressure containment and a regulation means for controlling gas pressure in said pressure containment, and
• wherein said first and said second slit apertures are both positioned to pass a very narrow band of light having approximately the same narrow wavelength range so as to permit bandwidth measurements and wherein wavelength scanning is accomplished by changing the pressure in said pressure containment.