System and Method for Creating and Utilizing Dual Laser Curtains From a Single Laser in an LPP EUV Light Source

A method and apparatus for creating and utilizing dual laser curtains from a single laser source in a laser produced plasma (LPP) extreme ultraviolet (EUV) light system is disclosed. A polarizing beam splitter creates two beams of orthogonal polarization from a single laser, and the beams are used to generate two laser curtains. Sensors detect flashes from droplets of target material as they pass through the curtains. One sensor may detect the position of the droplets relative to a desired trajectory to the irradiation site so that the orientation of a droplet generator may be adjusted to direct subsequent droplets to the irradiation site, as in the prior art. A second sensor may detect each droplet as it passes through a curtain to determine when a source laser should generate a pulse so that the pulse will arrive at the irradiation site at the same time as the droplet, so that a signal may be sent to the source laser to fire at the correct time.