Patent ID: 10283927

Abstract:
The line narrowed laser apparatus configured to perform a plurality of burst oscillations including a first burst oscillation and a second burst oscillation next to the first burst oscillation to output a pulse laser beam. The line narrowed laser apparatus comprises a laser resonator, a chamber provided in the laser resonator, a pair of electrodes provided in the chamber, an electric power source configured to apply a pulsed voltage to the pair of electrodes, a wavelength-selecting element provided in the laser resonator, a spectral width varying unit provided in the laser resonator, a wavelength variable unit configured to change a selected wavelength selected by the wavelength-selecting element, and a controller. The controller is configured to control the wavelength variable unit based on an amount of control of the spectral width varying unit in a period from a time of ending the first burst oscillation to a time of starting the second burst oscillation.