Patent ID: 8476609

Claim:
An extreme ultraviolet light source device for generating extreme ultraviolet light, the device comprising: a target material supply unit for supplying target material into a chamber; a laser oscillator for outputting a pulse laser beam; at least two amplifiers for amplifying the laser beam that is output from the laser oscillator; a focusing optical system for irradiating the laser beam after the amplification onto the target material by focusing the laser beam, which is amplified by the amplifier and is output, to a predetermined position in the chamber; and a saturable absorber device, disposed on an optical path between the laser oscillator and the predetermined position, for absorbing at least a laser beam having a light intensity not greater than a predetermined value and suppressing laser beam transmission, the saturable absorber device comprising: a saturable absorber cell having a main body unit that has a flow space where the saturable absorber flows, an inlet for letting the saturable absorber enter the flow space, an outlet for letting the saturable absorber out from the flow space, a window constituted by diamonds for passing the output laser beam from the laser oscillator to the flow space, a mirror disposed in the flow space to reflect the laser beam traveling through the window, and a cooling mechanism configured to cool the mirror.