Multiple-pass interferometric device

An apparatus for measuring a spectral distribution of a narrow-band laser beam generated by a line-narrowed excimer laser or a molecular fluorine laser system, comprising:

• a tunable interferometric device disposed along an optical path of an output beam of the laser system, such that the beam traverses the tunable interferometric device on a first pass and is tuned over one of a plurality of free spectral ranges;
• a retro-reflector disposed after the tunable interferometric device along said optical path for retro-reflecting the beam back through the tunable interferometric device on a second pass;
• and
• a detector for measuring an intensity of the beam tuned to said one of a plurality of free spectral ranges after the second pass through the interferometric device, and
• wherein spectral information is determined by measuring the intensity of the beam at each of the plurality of free spectral ranges.

An apparatus for measuring a spectral distribution of a narrow-band laser beam generated by a line-narrowed excimer laser or a molecular fluorine laser system, comprising:

• an interferometric device disposed along an optical path of an output beam of the laser system such that the beam traverses the interferometric device on a first pass;
• a retro-reflector disposed after the interferometric device along said optical path for retro-reflecting the beam back through the interferometric device on a second pass;
• a detector for detecting an intensity of the beam after the second pass through the interferometric device;
• and
• a light guidance cable for directing the beam towards the interferometric device;
• wherein the interferometric device is tunable such that beam traversing the interferometric device is tuned over one of a plurality of free spectral ranges of the interferometric device, and the spectral distribution is determined by examining each of the plurality of free spectral ranges.

An apparatus for measuring a spectral distribution of a narrow-band laser beam generated by a line-narrowed excimer laser or a molecular fluorine laser system, comprising:

• a pressure-tunable interferometric device disposed along an optical path of an output beam of the laser system such that the beam traverses the interferometric device on a first pass, the pressure-tunable interferometric device being tunable to any of a plurality of free spectral ranges;
• a retro-reflector disposed after the interferometric device along said optical path for retro-reflecting the beam back through the interferometric device on a second pass;
• a detector for detecting an intensity of the beam over one of said plurality of free spectral ranges after the second pass through the interferometric device, and
• wherein the beam makes a third interferometric pass prior to being incident upon the detector, and the spectral distribution can be measured by detecting an intensity of the beam at each of said plurality of free spectral ranges.

An apparatus for measuring a spectral distribution of a narrow-band laser beam generated by a line-narrowed excimer laser or a molecular fluorine laser system, comprising:

• an interferometric device disposed along an optical path of an output beam of the laser system such that the beam traverses the interferometric device on a first pass;
• a retro-reflector disposed after the interferometric device along said optical path for retro-reflecting the beam back through the interferometric device on a second pass;
• and
• a detector for detecting an intensity of the beam after the second pass through the interferometric device, and
• wherein spectral information is determined by the detector making a plurality of measurements of the intensity of the beam, each measurement being made when the interferometric device is tuned to a free spectral range of the interferometric device.