Single quantum path control by a fundamental chirped pulse combined with a subharmonic control pulse

Highlights: ► HHG spectra and attosecond pulse generation from a model He atom. ► Two-color laser field of a chirped fundamental pulse and a subharmonics control pulse. ► Single quantum path selection by β = 4.55 chirp pulse and the zero-phase 2000 nm control pulse. ► Formation of 337 eV supercontinuum region and generation of 39 as pulse. -- Abstract: In this paper, we study the issue of single quantum path control and its role in attosecond pulse generation. By carrying out the time-dependent Schrödinger equation analysis for the harmonic emission from a single He atom irradiated by the two-color laser field, consisting of a short 800 fundamental chirped pulse and a subharmonic 800–2400 nm control pulse, we find that the most favorable condition for attosecond generation is at the fundamental chirp parameter β = 4.55 together with the zero-phase 2000 nm control pulse, in which the single quantum path (short quantum path) is selected to contribute to the harmonic spectrum exhibiting an ultrabroad supercontinuum of a 337 eV bandwidth. Finally, an isolated attosecond pulse as short as 39 as is thus generated directly.