Quantum path control of H2+ during a high-order harmonic generation process by adjusting the laser intensity of a terahertz assisted field

Abstract

We investigate high-harmonic generation (HHG) for the molecular ion by solving a two-dimensional time-dependent Schrödinger equation in the combination of a circularly polarized laser pulse and a terahertz (THz) field. The results published recently by Ge et al (Opt. Express 23 8837–44) show that the harmonic intensity can be greatly enhanced when a THz field is added. Our work is an extension of Ge et al’s. We focus on considering the influence of THz field with different peak intensity, which shows that, with the increasing peak intensity of THz field, the cutoff of the harmonics can be remarkably extended, and the harmonic spectrum presents a two-plateau structure. The time-frequency analysis shows that the long trajectory makes a contribution to HHG when the intensity of THz field is low. With the increase of peak intensity of THz field, the long trajectory gradually disappears and the short trajectory makes the main contribution to HHG. We present the classical trajectory of the electron and the temporal evolution of the probability density of the electron wave packet to further understand the electron motion and the physical insight into HHG.