Isolated Attosecond Pulse Generation by Two-Mid-IR Laser Fields

The availability of tunable mid-infrared laser systems capable to deliver high intensity few cycle pulses offers the perspective of generating ultrashort radiation in the extreme UV range through the high-order harmonic generation (HHG) of the fundamental. In particular, such systems make possible the superposition of multiple colors of incommensurable frequencies that gives rise to time gating of HHG, thereby realizing the necessary condition leading to isolated attosecond pulse (IAP) generation. In this paper, the HHG resulting from the superposition of two incommensurable frequencies is analyzed with the aim to find out the conditions that the relative intensity and frequency of the two fields have to fulfill in order to generate isolated attosecond pulses. It is observed that the two fields can be superimposed in parallel and perpendicular polarization, both giving rise to IAP under appropriate conditions.