The conventional line-narrowing methods employed by narrow-band KrF excimer lasers are (1) intracavity etalons and (2) a Littrow grating with beam expansion. They have the following problems in high average power operation: (a) short lifetime of the etalons and large wavelength drift and large line-width change (the etalons method), or (b) low output power and short lifetime of electrodes (the grating method). To solve there problems, a hybrid method consisting of two prism beam expanders, an etalon and a Littrow grating, it proposed. These prism beam expanders decrease the light intensity on the etalon, so that the lifetime of the etalon is increased drastically, the passive wavelength drift is minimized, and the wavelength is adjusted quickly. By employing this system, average power of more than 8 W, line-width of less than 2.5 pm(FWHM), and long-term wavelength stability of less than +-0.5 pm were achieved.

Date Published: 1 July 1991
PDF: 12 pages
Proc. SPIE 1463, Optical/Laser Microlithography IV, (1 July 1991); doi: 10.1117/12.44820

Published in SPIE Proceedings Vol. 1463:
Optical/Laser Microlithography IV
Victor Pol, Editor(s)