Control of debris production of laser plasma sources with high-average XUV power

摘要

Recent investigations on methods to eliminate the contamination of high power laser plasma sources are reviewed. The use of separate methods such as a buffer gas environment or thin tape targets suppresses the debris yield drastically up to a factor of 10$+3$/. A combination of this with other effective as well as practically convenient methods (use of debris angular characteristics, a rotating shutter, or thin UV filters) provides a truly contamination-free XUV source. As an example of a novel high power source we describe the performance of a 1.5 J KrF laser designed to drive a laser plasma XUV source. The laser was used to generate narrowband XUV radiation at 18 nm. A conversion efficiency of $GREQ 1.4% in a bandwidth of 6% was measured, demonstrating the feasibility of laser plasma sources for applications such as XUV projection lithography, requiring high average power.