| 摘要 |
PROBLEM TO BE SOLVED: To provide an excimer laser device capable of oscillating at an accurate and stable center wavelength, irrespective of the environmental change. SOLUTION: An etalon (33C) is irradiated with a stable reference light (39) of a known wavelength and a laser beam (11) to measure the center wavelength (λeX) of the laser beam (11), based on the location of bright stripes (34C, 35C) of resultant interference fringes, and the center wavelength (λex) is controlled in a wavelength control method. This wavelength control method comprises a step of selecting the etalon (33C) so that only one first- or higher-degree bright stripe of the reference light (39) appears as an image between the image forming positions (34C) of bright stripes formed at an upper and lower limit center wavelengths (λex2,λex1) of the laser beam (11), and controlling the center wavelengths (λex) of the laser beam (11) so as to align the image forming position of the first- or higher-degree bright stripe of the reference light (39) with that of the bright stripe (34C) of the laser beam (11).
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