Abstract
We derive the analytical theory describing the process of sub-femtosecond pulse formation from a quasi-monochromatic seeding extreme ultraviolet (XUV) radiation, which propagates in active medium of a hydrogen-like 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 Li2+ plasma-based X-ray laser with a carrier wavelength 13.5nm. We analyze the role of plasma dispersion and find the optimal conditions for the formation of attosecond pulses with the highest contrast. Under the 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.
Highlights
Intense attosecond pulses of coherent extreme ultraviolet (XUV)/x-ray field provide a unique combination of high spatial and temporal resolution desirable for the applications in dynamical, element-specific imaging in biochemistry and material science.There are three conventional types of sources of ultrashort coherent XUV/x-ray pulses: high harmonic generation (HHG) sources, x-ray free-electron lasers (XFELs), and plasma-based x-ray lasers
We derived an analytical solution describing the process of attosecond pulse formation in inverted active medium of hydrogenlike plasma-based x-ray laser, modulated by an IR laser filed and seeded with the quasimonochromatic XUV radiation
On the basis of the derived solution we studied the qualitative dependencies of characteristics of the produced pulses on the parameters of the active medium and the modulating field for the case of the Li2+ hydrogenlike plasma-based x-ray laser
Summary
Intense attosecond pulses of coherent extreme ultraviolet (XUV)/x-ray field provide a unique combination of high spatial and temporal resolution desirable for the applications in dynamical, element-specific imaging in biochemistry and material science (see reviews on plasma-based x-ray lasers [1,2,3,4] and attosecond physics [5,6,7,8,9]). A method has been proposed for the transformation of a picosecond seeding XUV or x-ray radiation into a train of attosecond pulses via the modulation of an active medium of a hydrogenlike plasma-based x-ray amplifier by a strong optical laser field [22]. If the plasma is dense for the modulating optical field and the generation of sidebands is suppressed, an active medium of an x-ray laser might be used for the amplification of attosecond pulse trains produced via the HHG process preserving the duration and shape of attosecond pulses [23]. We verify the results of the linearized analytical theory taking into account the nonlinearities of the system and determine more precisely the optimal conditions for the sub-fs pulse formation feasible experimentally for the case of an active medium of Li2+ hydrogenlike plasma-based x-ray amplifier.
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