High-order harmonic generation in orthogonal IR and XUV pulses: XUV-initiated channel separation and polarization control

Abstract

Single-atom high-order harmonic generation (HHG) induced by an intense linearly polarized infrared (IR) field and assisted by a perturbative extreme ultraviolet (XUV) short pulse with linear polarization is analyzed in perpendicular geometry. It is shown that for the case of the initial $p$ state, the two independent projections of the laser-induced dipole are formed by two independent physical channels, which are responsible for IR-induced HHG and XUV-initiated HHG. This property of the laser-induced dipole is utilized for polarization control of the generated radiation. An alternative scheme for studying XUV-initiated HHG is proposed.