Saddle point approach for the study of HHG on both fs and as timescales

When a laser pulse is focused to a high intensity in a rare gas jet, high-order harmonics of the driving field are generated. These harmonics serve as a broadband XUV radiation source enabling the production of attosecond pulses. The generation mechanism is a three-step process where an electron is teared off from the atom, accelerated in the laser field, and then recaptured while emitting the excess energy in the form of a high-energy photon. We here study theoretically the spectral and temporal features of HHG driven by short laser pulses with emphasis on the effects of the finite duration of the pulse.