Patent ID: 8604452

Claim:
An EUV light source comprising; a droplet generator producing a stream of target material droplets; a first optical gain medium amplifying light on a first beam path without a seed laser providing a seed laser output to the first beam path, said light on said first beam path having a first linear polarization direction, said first beam path being part of a first optical cavity disposed between a target material irradiation site and a first optics; a second optical gain medium amplifying light on a second beam path without a seed laser providing a seed laser output to the second beam path, said light on said second beam path having a second linear polarization direction orthogonal to said first linear polarization direction, said second beam path being part of a second optical cavity disposed between said target material irradiation site and said first optics; and a beam combiner combining light from said first beam path and said second beam path such that said light, after said combining, interacts with a target material droplet at said target material irradiation site to produce EUV light emitting plasma.