Laser apparatus and extreme ultraviolet light source apparatus

An extreme ultraviolet light source apparatus comprising:

• a laser apparatus having:
• a master oscillator including a plurality of semiconductor lasers each of which outputs one or more longitudinal-mode laser lights;
• an amplifier with a molecular gas as an amplifying medium amplifying a longitudinal ode laser light of which wavelength is included in one of amplifiable lines;
• at least one pair of high-reflective mirrors arranged so as to sandwich an amplifiable region of the amplifier in order to make the longitudinal-mode laser lights outputted from the master oscillator shuttle in the amplifiable region more than once;
• a plurality of Peltier elements each of which is configured for contacting corresponding one of the semiconductor lasers;
• and
• a controller configured for controlling at least one of the Peltier elements at a temperature different from a temperature of another Peltier element so that at least a part of wavelength of the longitudinal-mode laser light outputted from each semiconductor laser is included in one of the amplifiable lines, the laser apparatus being used as a driver laser, wherein
• the laser apparatus irradiates a target material with a laser light for generating plasma, and the extreme ultraviolet light emitted from the plasma is focused by an EUV collector mirror and outputted from the ultraviolet light source apparatus.