Photoionization-pumped x-ray lasers using ultrashort-pulse excitation.

Recent advances in the production of ultrashort x-ray pulses by using femtosecond laser-produced plasmas coupled with the development of terawatt ultrashort-pulse lasers may make possible ultrashortpulse photoexcited x-ray lasers. I examine the creation of a population inversion on the K-alpha transition of neon at 1.5 nm by using the photoionization scheme first suggested by Duguay and Rentzepis in 1967. It is shown that this laser can be produced by using a pump laser of ~ 10 J in 50 fs, provided that a sufficiently bright laser-produced plasma x-ray source can be created. Recent experimental and theoretical results are discussed that verify the potential feasibility of this scheme.