US Patent 10340654 Laser apparatus and extreme ultraviolet light generating system

A laser apparatus includes a light source configured to output excitation light, an optical resonator in which laser medium is excited by the excitation light, the optical resonator being configured to output laser beam, a temperature regulator configured to adjust temperature of the light source to a standard temperature, an optical detector configured to detect output power of the laser beam, and a controller configured to change the standard temperature based on the detected output power of the laser beam.