US 6,154,470 A · Molecular fluorine (F.sub.2) laser with narrow spectral linewidth

Abstract

A molecular fluorine (F.sub.2) laser is provided wherein the gas mixture comprises molecular fluorine for generating a spectral emission including two or three closely spaced lines around 157 nm. An etalon provides line selection such that the output beam only includes one of these lines. The etalon may also serve to outcouple the beam and/or narrow the selected line. Alternatively, a prism provides the line selection and the etalon narrows the selected line. The etalon may be a resonator reflector which also selects a line, while another element outcouples the beam. The etalon plates, preferably uncoated, comprise a material that is transparent at 157 nm, such as CaF.sub.2, MgF.sub.2, LiF.sub.2, BaF.sub.2, SrF.sub.2, quartz and fluorine doped quartz. The etalon plates are separated by spacers comprising a material having a low thermal expansion constant, such as invar, zerodur.RTM., ultra low expansion glass, and quartz. A gas such as helium or a solid such as CaF.sub.2 that does not absorb radiation 157 nm fills the gap between the etalon plates, or the gap is evacuated. The gas mixture preferably further includes neon as a buffer gas. Another etalon may be used for line narrowing. One or more of a highly reflective mirror, a high finesse etalon or a prism with a highly reflective back surface may serve as a highly reflective resonator reflector. Any of one or more etalons, a prism, a brewster plate and a highly or partially reflective mirror may seal the laser discharge chamber.

Claims33

Dependent claims

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;
and
a 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.

1 more element

Dependencies are inferred from the claim text.

Molecular fluorine (F.sub.2) laser with narrow spectral linewidth

Life of this patent

Molecular fluorine (F.sub.2) laser with narrow spectral linewidth

Life of this patent

Abstract

Claims33