Control of the high-order harmonics cutoff through the combination of a chirped laser and static electric field

The high-order harmonic generation for a one-dimensional hydrogen atom model in the combination of the chirped laser pulse and static field is theoretically investigated. Here we explore a novel physical mechanism of the significant extension of high-order-harmonic generation cutoff based on three-step model. It is shown that due to the asymmetry of the combined field the cutoff is substantially extended. If appropriate parameters are chosen, the cutoff of high-order harmonic generation can reach I-p+42U(p). Furthermore, an ultrabroad supercontinuum spectrum can be generated. When the phases are properly compensated for, an isolated 10 as pulse can be obtained.