Abstract: An extreme ultra violet light source apparatus by which EUV light can be efficiently obtained uses a driver laser which can realize a desired pulse width with substantially homogeneous intensity. The apparatus generates extreme ultra violet light by applying a laser beam to a target, and includes a chamber in which extreme ultra violet light is generated; a target supply unit which supplies a liquid or solid metal target to a predetermined position within the chamber; a laser beam generating unit which synthesizes pulse laser beams having delays different from one another to generate a single pulse laser beam or a pulse train laser beam having substantially homogeneous intensity, and applies the laser beam to the target supplied by the target supply unit to generate plasma; and a collector mirror which collects the extreme ultra violet light radiated from the plasma and outputs it.

Abstract: For the purpose of providing a discharge excitation type pulse laser apparatus capable of reducing disturbance of the discharge space caused by shock waves, the discharge excitation type pulse laser apparatus according to the present invention is designed for generating a pulsed main discharge by applying a high voltage between main electrodes (14, 15) including a cathode (15) and an anode (14) arranged in opposition to each other, and thereby exciting a laser gas in a discharge space (37) defined between the main electrodes to oscillate laser light (21), and characterized in that no reflector larger than a prescribed size is provided on a surface within a prescribed surface distance (LC) from the discharge space (37), and an insulating cathode insulating member (54) that is inclined such that the cathode (15) side end is highest is arranged on at least one of the upstream and downstream sides of the cathode (15) in close contact with the cathode (15).