Extended quantitative rescattering model for simulating high-order harmonic streaking spectra by synchronization of an intense IR laser and a time-delayed attosecond XUV pulse

Abstract

We theoretically investigate the modulated high-harmonic generation (HHG) driven by an intense few-cycle infrared (IR) laser field and a weak extreme-ultraviolet (XUV) pulse at a delayed time. We establish an extended quantitative rescattering (EQRS) model to simulate the HHG streaking spectra, with the ideas of correcting the IR ionization and the transition from the ground to continuum states in the strong-field approximation.The EQRS model has an accuracy comparable to that from "exactly" solving the time-dependent Schrödinger equation (TDSE). We reveal that the fringes in the streaking spectra are caused by the interference between the attosecond XUV pulse and harmonics resulting from different recombination pathways under the intense IR laser. We then demonstrate that the XUV pulse can be accurately retrieved by treating the single-atom TDSE results or macroscopic propagation results as the "input" data. This work provides with a tool for efficiently simulating and thoroughly analyzing the XUV-assisted HHG, which could also enhance its capability for tracing the electron dynamics involved in the strong-field phenomena.

Direct reconstruction of isolated XUV or soft x-ray attosecond pulses from high-harmonic generation streaking spectra

“…Different from most retrieval algorithms used for attosecond photoelectron streaking experiments, our method does not rely on the iterative procedure, thus errors in the retrieved results are introduced only by the experimental measurements and the model itself, but not by the convergence of the iterations. Note that, compared to the earlier retrieval method in [55], a significant advance has been made in the present version such that the spectral phase of any form can be directly extracted from the HHG spectra, even for the irregularly behaved phase. We showed that our method can well retrieve the spectral phases (or the temporal intensity profiles) for both isolated XUV and SXR pulses, which have a narrow bandwidth in the XUV and a broad bandwidth in the SXRs, respectively.…”

“…To simulate single-atom HHG streaking spectra under a linearly polarized weak XUV (or SXR) IAP and a strong IR (or MIR) laser, we can employ the previously established EQRS model [55]. This model is an improvement of SFA [56].…”

“…In the above equation, the x 4 (ω, τ ) term is neglected because of its much smaller amplitude. Details of the derivation of EQRS model can be found in [55].…”

“…The wave packet W 2 (ω, τ ) in equation ( 9) is the same in the SFA and EQRS [55], thus equation ( 22) is valid in the EQRS model. Multiplying by e iω j t and then integrating both sides of equation ( 22) with time t, we get…”

“…It can also be realized by other setups, for instance, two gas-jet setup employed by Seres et al [53,54]. In our previous work [55], a simpler approach was introduced to characterize the IAP where the spectral phase can be described by a single parameter only. The parameter was retrieved through iterative procedure.…”