Broadband water window supercontinuum generation with a tailored midinfrared laser pulse in asymmetric molecular gases

Theoretically, we investigate the high-order harmonic generation (HHG) from asymmetric molecules with a phase-stabilized few-cycle midinfrared laser pulse tailored by a much weaker 800-nm laser pulse. The results indicates that the ionization is almost restricted within half an optical cycle of the driving laser pulse and the energy difference between the photons emitted by the ejected electrons in this half optical cycle and its next half optical cycle is significantly enlarged. Then a 270 eV water window supercontinuum is produced in the plateau of the high-order harmonic spectrum, from which an isolated water window 67 attoseconds pulse can be filtered directly. Moreover, this scheme can also be extended to the multi-cycle regime, enabling the generation of a broadband supercontinuum with higher photon energy and an intensity comparable to that of the lower-order harmonics.