Extreme ultraviolet laser action in plasmas

Abstract

The development of a laser operating in the extreme ultraviolet or X-ray spectral regions remains an outstanding problem of current technology. Despite the many proposals, no demonstration of significant gain on a transition in this region has yet been reported. The constraints introduced by decreasing wavelength are increasingly severe, demanding high pump power in a system with a relatively short lifetime. In consequence, much attention has been paid to the use of plasma, often generated by high power laser irradiation, as the gain medium. In this paper I briefly outline the various avenues by which laser action in plasmas has been explored, with a view to identifying those which seem at present to offer promise of success. Particular attention is given to the recombination scheme with an emphasis on a recent demonstration of gain.