Generation of high-intensity KeV isolated attosecond pulse via multi-color inhomogeneous beams superposition

Abstract

A potential scheme to obtain the high-intensity KeV isolated attosecond pulses (IAPs) from the high-order harmonic generation (HHG) has been proposed and studied via the superposition of the multi-color inhomogeneous laser beams. The scheme can be separated into three steps. Firstly, with the superposition of two-color mid-infrared field and a few-cycle infrared field at the proper delay time and the carrier envelope phase, the optimal HHG spectrum can be found. Secondly, with the help of the positive inhomogeneous effect in space, the harmonic emission peaks (HEPs) from the positive half-cycle can be well selected. Secondly, by properly adding a unipolar pulse with the positive peak, the harmonic cutoff can be extended to the KeV region and the harmonic plateau is only contributed by the single HEP. Thirdly, with the introduction of the UV pulse, the signal of the harmonic plateau can be enhanced by at least 500 dB due to the UV-resonance-enhancement-ionization. Finally, through the Fourier transformation of some selected harmonics, the sub-35 as IAPs in the KeV region can be obtained.