Modern table-top x-ray plasma lasers produce high energy pulses (up to several mJ) but of rather long picosecond duration. It limits their application for dynamical imaging of fast processes in nanostructures and micromolecules, including the processes induced by the laser radiation. Recently the possibility of an efficient transformation of a picosecond X-ray pulse into a train of subfs pulses in resonant absorber with a transition frequency modulated by an IR field has been shown . Here we suggest two new approaches for generation of the intense attosecond pulses by the X-ray plasma lasers in the soft x-ray range: (i) seeding of the x-ray plasma based laser with a train of attosecond pulses produced via high-harmonic (HH) generation, and (ii) generation of the attosecond pulses directly by the x-ray laser. Both approaches can be achieved via interaction of the x-ray plasma laser radiation or the high-harmonic radiation, accordingly, with the resonant medium modulated by a moderately strong IR or visible laser field similar to . However, contrary to , the case of the multicomponent incident radiation, as well as the case of two stage amplifier, allowing for generation of attosecond pulses in the absence of any seeding radiation are studied.
In particular, the possibility to amplify about 100 times an incident train of attosecond pulses (produced via HHG) with a pulse duration down to 150 as and a carrier wavelength 3.38nm (in a “water window” range) is shown