LASER DEVICE AND EXTREME ULTRAVIOLET LIGHT GENERATION SYSTEM

摘要

This laser device may include a master oscillator, a plurality of amplifiers, an optical sensor device that detects light travelling backward in a laser light path, and a control unit. The optical sensor device may include a first optical sensor that detects energy of the light travelling backward in the laser light path, and a second optical sensor that detects power of the light travelling backward in the laser light path. The control unit may determine that return light is generated in the cases where the intensity of an energy detection signal exceeds a first threshold value. The control unit may determine that self oscillation light is generated in the cases where the intensity of a power detection signal exceeds a second threshold value.