An LPP EUV light source is disclosed having an optic positioned in the plasma chamber for reflecting EUV light generated therein and a laser input window. For this aspect, the EUV light source may be configured to expose the optic to a gaseous etchant pressure for optic cleaning while the window is exposed to a lower gaseous etchant pressure to avoid window coating deterioration. In another aspect, an EUV light source may comprise a target material positionable along a beam path to participate in a first interaction with light on the beam path; an optical amplifier; and at least one optic directing photons scattered from the first interaction into the optical amplifier to produce a laser beam on the beam path for a subsequent interaction with the target material to produce an EUV light emitting plasma.
