Wavelength measurement apparatus, narrowed-line laser apparatus, and method for manufacturing electronic devices

A narrowed-line laser apparatus comprising:

• a laser oscillator configured to output a pulse laser beam;
• a line-narrowing optical system disposed in the laser oscillator;
• an actuator configured to change a wavelength selected by the line-narrowing optical system;
• a first spectrometer having a first free spectral range and configured to generate a first measured waveform from an interference pattern produced by the pulse laser beam;
• a second spectrometer having a second free spectral range narrower than the first free spectral range and configured to generate a second measured waveform from the interference pattern produced by the pulse laser beam;
• and
• a processor configured to set a target wavelength based on a wavelength instruction value received from an external apparatus, read data on a first measurement range of the first spectrometer, the first measurement range corresponding to a first portion of the first measured waveform excluding a second portion of the first measured waveform, set a second measurement range of the second spectrometer based on the data on the first measurement range, the second measurement range corresponding to a first portion of the second measured waveform excluding a second portion of the second measured waveform and corresponding to a wavelength range narrower than the second free spectral range, read data on the second measurement range, calculate a center wavelength of the pulse laser beam based on the data on the first measurement range and the data on the second measurement range, and control the actuator based on the target wavelength and the center wavelength,
• wherein the processor is configured to
• receive the wavelength instruction value, which changes the target wavelength to a value between a first wavelength and a second wavelength,
• control the laser oscillator in such a way that pre-oscillation is performed at a wavelength between the first and second wavelengths,
• calculate a reference wavelength based on the first measured waveform generated in the pre-oscillation,
• calculate a first amount of change indicating a change in a calculated wavelength calculated based on the data on the first measurement range with respect to the reference wavelength, and
• set the second measurement range based on the first amount of change.