Narrow band laser with etalon based output coupler
AssigneeCymer, Inc.
InventorAlexander I. Ershov
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Abstract
A line narrowed laser having a grating based line narrowing module, etalon-based line narrowing output coupler and a technique for tuning the laser. The etalon based output coupler is adjusted to preferentially reflect light at or near the spectral maximum produced by the grating. Substantial improvement in line narrowing results from the amplification in the laser resonance chamber of light at or near the grating spectral maximum which is preferentially reflected by the etalon based output coupler. Several preferred methods are disclosed for tuning the etalon based output coupler to match the wavelength selected by the grating based line narrowing module.
Claims8
A process for tuning a narrow band gas discharge laser defining a gain medium and equipped with tunable grating based line narrowing module and a tunable etalon based output coupler, said process comprising the steps of:
- A. operating the laser;
- B. adjusting said tunable grating to reflect back into said gain medium light at a first narrow range of wavelength;
- C. adjusting said tunable etalon based output coupler to reflect back into said gain medium light at a second narrow range of wavelengths;
- D. measuring the spectral characteristics of a beam produced by a laser;
- E. tuning said tunable grating based line narrowing module and said tunable output coupler to produce desired beam spectral characteristics.
Dependencies are inferred from the claim text.