NARROW BAND EXCIMER LASER

摘要

2064207 9014704 PCTABS00002 A narrow-band oscillation excimer laser employing a diffraction grating as a wavelength selecting element, which is particularly suited for a light source of a reduction type projection aligner. The grating used in the narrow-band oscillation excimer laser of the invention is so disposed that the direction of grating lines is nearly perpendicular to the direction of laser discharge. When a beam expander is used to expand laser beam falling on the beam expander is so disposed that the direction of beam expansion is nearly perpendicular to that of discharge of the laser. Further, when an aperture is to be used in the optical resonator, the aperture is placed so that the longitudinal direction may be parallel to the direction of laser discharge. Moreover, the front mirror of the optical resonator is a cylindrical one, whose mechanical axis is in parallel with the direction of laser discharge. This makes it possible to provide a narrow-band oscillation excimer laser having very high efficiency and excellent durability.