Isolated short attosecond pulse generated using a two-color laser and a high-order pulse

Abstract

An efficient method to generate an isolated short attosecond pulse is investigated theoretically. A broadband extreme ultraviolet supercontinuum harmonics can be generated when a model He${}^{+}$ ion is exposed to the combination of an intense few-cycle laser pulse and a low-frequency field. By properly adding a $27$th harmonics pulse to resonantly excite the He${}^{+}$ ion, the intensity of the high-order harmonic generation (HHG) plateau is enhanced by $3\ensuremath{-}4$ orders of magnitude. As a result, an isolated $24$-as pulse with a bandwidth of $138$ eV can be obtained directly from the supercontinuum around the cutoff of HHG.