Abstract
In this work we propose a novel procedure for the characterization of attosecond pulses. The method relies on the conversion of the attosecond pulse into electron wave-packets through photoionization of atoms in the presence of a weak IR field. It allows for the unique determination of the spectral phase making up the pulses by accurately taking into account the atomic physics of the photoionization process. The phases are evaluated by optimizing the fit of a perturbation theory calculation to the experimental result. The method has been called iPROOF (improved Phase Retrieval by Omega Oscillation Filtering) as it bears a similarity to the PROOF technique [Chini et al. Opt. Express 18, 13006 (2010)]. The procedure has been demonstrated for the characterization of an attosecond pulse train composed of odd and even harmonics. We observe a large phase shift between consecutive odd and even harmonics. The resulting attosecond pulse train has a complex structure not resembling a single attosecond pulse once per IR period, which is the case for zero phase. Finally, the retrieval procedure can be applied to the characterization of single attosecond pulses as well.
Highlights
The recent development of x- or extreme-ultraviolet (XUV-EUV) light pulses on an attosecond timescale has opened up new avenues for experimentalists to probe temporal aspects of electron dynamics in atoms, molecules and condensed matter [1, 2]
In order to find an iterative solution for these phases in a reasonable amount of time, the simulated temporal modulation is generated from an approximate analytical model of the conversion process, rather than from the “exact” calculation based on numerical solution of the time-dependent Schrodinger equation (TDSE)
We demonstrate a new retrieval procedure which allows the determination of the spectral phases of the harmonics making up attosecond pulse train composed of both even and odd harmonics
Summary
The recent development of x- or extreme-ultraviolet (XUV-EUV) light pulses on an attosecond timescale has opened up new avenues for experimentalists to probe temporal aspects of electron dynamics in atoms, molecules and condensed matter [1, 2] Both Single Attosecond Pulses (SAPs) and Attosecond Pulse Trains (APTs) have already shown to be very promising tools for the temporal characterization of various atomic processes, such as the delay times in Auger decay [3], tunneling [4, 5], and photoionization [6,7,8,9]. The precision of the phase measurement is directly related to the accuracy of the simplified theoretical description of the laser-assisted photoionization process used in the retrieval procedure
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