| CPC H01S 3/094096 (2013.01) [H01S 3/1024 (2013.01); H01S 3/104 (2013.01)] | 20 Claims |

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1. A line narrowing gas laser device, comprising:
an actuator configured to change a center wavelength of pulse laser light; and
a processor configured to control the actuator,
the processor reading parameters including a number of irradiation pulses of pulse laser light to be radiated to one location of an irradiation receiving object, a shortest wavelength, and a longest wavelength;
setting a first pattern with which the center wavelength is changed to approach the longest wavelength from the shortest wavelength and a second pattern with which the center wavelength is changed to approach the shortest wavelength from the longest wavelength such that at least one of the first pattern and the second pattern is different between a case in which the number of irradiation pulses is an even number and a case in which the number of irradiation pulses is an odd number; and
controlling the actuator so that the first pattern and the second pattern are alternately performed.
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