Extreme ultra violet light source apparatus

A laser produced plasma type extreme ultraviolet light source apparatus for generating extreme ultraviolet light by applying a laser beam to a target material, said apparatus comprising:na chamber in which extreme ultraviolet light is generated;a target supply unit configured to supply a target material to a predetermined position within said chamber;a laser beam focusing optics configured to focus a laser beam from a driver laser using a laser gas containing a carbon dioxide gas as a laser medium, for applying the laser beam to the target material supplied by said target supply unit to generate plasma;a collector mirror configured to collect the extreme ultraviolet light radiated from the plasma to output the extreme ultraviolet light; anda spectrum purity filter provided in an optical path of the extreme ultraviolet light from said collector mirror, and configured to transmit the extreme ultraviolet light and to reflect the laser beam, said spectrum purity filter including a wire grid polarizer having a pitch not larger than a half of a shortest wavelength of the laser beam from said driver laser.