Self-Seeded Raman Shifter for Single-Band Operation of a XeF Laser

Xenon fluoride is the best excimer laser for atmospheric propagation, since its wavelength is the least absorbed in the atmosphere. To date, all efficient xenon fluoride lasers have their energy divided between 2 bands, 351 and 353 micrometer. One can increase the laser efficiency by heating the XeF to 425 degrees Kelvin, but this spreads the energy more evenly between the two bands. The 2-nm bandwidth is too large for coherent imaging techniques that DoD is trying to apply. By Raman shifting the 351 to the 353 band. Science Research Laboratory will collapse the bandwidth and make the coherence length the long enough for the most exacting imaging techniques while maintaining the high efficiency. Phase I will identify appropriate Raman media and Phase II will demonstrate the bandwidth collapse. In Phase III, Science Research Laboratory will retrofit existing XeF lasers to apply them to lithography.