Patent ID: 6154470
Filing Date: 2000-11-28
Classification: H01S

Abstract:
An F.sub.2 -laser, comprising:a discharge chamber filled with a gas mixture including molecular fluorine generating a spectral emission including a plurality of closely spaced lines in a wavelength range between 157 nm and 158 nm, said plurality of closely-spaced lines including a primary line centered around a wavelength of 157.62 nm and a secondary line centered around a wavelength of 157.52 nm;a pair of electrodes coupled with a power supply circuit producing a pulsed discharge to energize said molecular fluorine; anda resonator including a prism and a first etalon, said prism being arranged at a particular orientation for dispersing the plurality of closely spaced lines including the primary and secondary lines such that only the primary line centered around 157.62 nm remains within an acceptance angle of the resonator and any other line(s) including the secondary line centered around 157.52 nm are dispersed outside of the acceptance angle of the resonator such that only the primary line at 157.62 nm is amplified among said plurality of closely-spaced lines, said first etalon being arranged for maximum reflectivity of a central portion of the primary line around 157.62 nm and for relatively low reflectivity of outer portions of the primary line to substantially suppress said outer portions, thereby narrowing the primary line such that said F.sub.2 -laser emits a single wavelength laser beam having a narrow spectral linewidth that is less than the linewidth of the 157.62 line of a free-running F.sub.2 laser to provide a narrow band VUV laser beam.