Sub-fs pulse formation in a seeded hydrogenlike plasma-based x-ray laser dressed by an infrared field: Analytical theory and numerical optimization

Abstract

We derive the analytical theory describing the process of subfemtosecond pulse formation from a quasimonochromatic seeding extreme ultraviolet (XUV) radiation, which propagates in the inverted active medium of a hydrogenlike plasma-based x-ray laser dressed by a strong infrared laser field. We discuss the ultimate capabilities and limitations of this process on the basis of the derived analytical solution and extensive numerical studies for the case of the Li^{2+} plasma-based x-ray laser with a carrier wavelength of 13.5 nm. We analyze the role of plasma dispersion and find the optimal conditions for the formation of attosecond pulses with the highest contrast. Under optimal conditions, the influence of amplified spontaneous emission from the active medium is negligible. The peak intensity of the produced XUV pulses can exceed 10^{10}−10^{11}W/cm^{2}, while the duration of pulses varies in the range of 400–600 as.