Narrow-spectrum laser device
A spectral purity range (E95) of a laser beam output from an amplifying laser device ( 300 ) is measured by spectral purity range measuring means. To have the measured spectral purity range (E95) within an allowable range E950±dE95 of a target spectral purity range (E950), discharge timing from a time when discharge is started by an oscillating laser device ( 100 ) to a time when discharge is started by the amplifying laser device ( 300 ) is controlled, and the spectral purity range (E95) is controlled to be stabilized.
1. A narrow-spectrum laser device having an oscillation laser device that outputs a narrow-spectrum seed beam by causing a laser beam to pass through a wavelength dispersion element several times, and an amplification laser device or an amplifying device that amplifies the seed beam by discharging a laser gas within an amplification chamber, and outputs an amplified laser beam, the narrow-spectrum laser device comprising:
spectral purity range measuring means for measuring a spectral purity range of a laser beam output from the amplification laser device or the amplifying device; and
control means for controlling, while maintaining operations of the oscillation laser device, a measured spectral purity range of said laser beam output to be held within an allowable range of a target spectral purity range by retarding a discharge timing from a start of discharge by the oscillation laser device to a start of discharge by the amplification laser device or the amplifying device if the measured spectral purity range of said laser beam output is wider than the target spectral purity range, and by advancing the discharge timing if the measured spectral purity range of said laser beam output is narrower than the target spectral purity.
2. The narrow-spectrum laser device according to claim 1 , wherein the control by the control means is executed within a synchronization allowable range of the allowable range of the target spectral purity range, in which an energy of the laser beam output from the amplification laser device or the amplifying device equals or exceeds an allowable level.
3. The narrow-spectrum laser device according to claim 1 , further comprising pulse stretching means for extending a laser pulse waveform of the seed beam, wherein a synchronization allowable range in which an energy of the laser beam output from the amplification laser device or the amplifying device equals or exceeds an allowable level is enlarged by extending the pulse waveform of the seed beam using the pulse stretching means.