| 摘要 |
PROBLEM TO BE SOLVED: To permit highly accurate wavelength control without use of the reference beam by detecting absorption spectra of carbon and oxygen based on an output of wavelength detector and detecting wavelength axis of the detector corresponding to such spectra to make compensating calculation for each position on the wavelength axis. SOLUTION: A narrow band excimer laser is provided with a chamber 1 and a narrow band unit 2 including a wavelength selecting element such as etalon. A wavelength controller 7 controllably drives the wavelength selecting element in a unit 2 with an output of a Czerny-Turner spectroscope 6 to control wavelength of the oscillated laser beam. Thereby, absorption spectra of carbon and oxygen are detected from the spectrum waveform and the wavelength axis of spectrometer is calibrated from the absorption spectra. A point on the wavelength axis corresponding to the target wavelength of the spectrometer 6 is identified by the calculation. Moreover, in the wavelength control 7, the wavelength selecting element is controllably driven so that the center wavelength of calibrated narrow laser beam is matched with the predetermined position on the wavelength axis corresponding to the target wavelength. |
