| 摘要 |
A molecular fluorine laser system emitting a narrow bandwidth laser beam and having efficient line-selection of a main line lambd1 of multiple closely-spaced lines around 157 nm includes a discharge chamber filled with a laser gas including molecular fluorine and a buffer gas, a gas handling module for periodically replenishing the molecular fluorine in the discharge chamber for maintaining said gas mixture at a selected composition, multiple electrodes within the discharge chamber and connected to a discharge circuit for energizing the molecular fluorine, and a resonator including the discharge chamber for generating a laser beam around 157 nm. The resonator further includes line-selection optics for selecting a main line lambd1 and suppressing a secondary line lambd2 of said plurality of closely-spaced lines. The line-selection optics include a line-selection package on the opposite of an output coupling side of the chamber and/or a solid element on the outcoupling side of the chamber having an interference maximum at the main line and an interference minimum at the secondary line. A contrast ratio of the main line to the secondary line in the laser beam is at least 100. The laser system further includes an enclosure maintained substantially free of VUV photoabsorbing species wherein the laser beam propagates within the enclosure between the resonator and an application process.
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