Photopumping of XUV lasers by XFEL radiation
Within the next few years X-ray free-electron lasers (XFELs) now under construction are expected to generate highly collimated XUV pulses with 1013 photons and a duration of 100 fs. Focusing this radiation to a spot some 10 [mu]m in diameter generates intensities of up to 1016 W/cm2. Such pump intensities make feasible the investigation of photopumped XUV lasers using this radiation. We present simulations taking into account two different mechanisms generating the gain: (1) photoionization with subsequent three-body recombination, which takes advantage of the monochromaticity of the pump radiation to generate very cold electrons; (2) inner-shell ionization in which transient inversion is obtained by generating a hole in an otherwise completely filled shell. The simulations show that under appropriate conditions both mechanisms generate very high gain. However, a number of further issues must be considered, such as the propagation of the pump pulse in the medium to be pumped.(Received November 1 2003)
(Accepted February 17 2004)
Key Words: Photopumping; X-ray free-electron laser; X-ray laser.
c1 Address correspondence and reprint requests to: Ernst Fill, Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching, Germany. E-mail: email@example.com
1 On leave from the Institute of Applied Physics and Computational Mathematics. P.O. Box 8009-12 Beijing, 100088, China.