Femtosecond soft x-ray lasing in dense collisionaly-pumped plasma

Abstract

We report the first experimental measurement of a strong pulse shortening of a seeded plasma-based soft x-ray laser at high electron densities. As a consequence of the gain gating caused by subsequent collisional ionization, the duration drops from 1.4 ps to an unprecedented value of 520 fs RMS when the electron density increases from 4 to 7.6×1019cm-3. These measurements, performed with an original single-shot method, are in good agreement with results from 3D Maxwell-Bloch simulations.