Theoretical investigation of the isolated attosecond pulse generation by restraining the spatial distribution of high-order harmonic emission

Isolated attosecond pulse (IAP) generation is theoretically investigated by using a few-cycle laser pulse from a two-dimensional model of hydrogen molecular ion. The harmonic spectra from two nuclei of hydrogen molecular ion lead to interference. We investigate the spatial distribution in harmonic generation and propose a scheme to restrain the harmonic generation from the nucleus along the positive-x direction, and thus the interference is weaken in spatial. By using a few-cycle 800 nm chirped laser pulse, the harmonics are mainly generated from the nucleus along negative-x direction in the region of 130th to 230th order. The harmonic spectra are smooth and are mainly contributed by the short quantum path near the cutoff region and IAP with a duration of 97 as is generated. The semiclassical of three-step model is also used to illustrate the physical mechanism.