Phase-retrieval algorithm for the characterization of broadband single attosecond pulses

Abstract

Recent progress in high-order harmonic generation with few-cycle mid-infrared wavelength lasers has pushed light pulses into the water window region and beyond. These pulses have the bandwidth to support single attosecond pulses down to a few tens of attoseconds. However, the present available techniques for attosecond pulse measurement are not applicable to such pulses. Here we report a phase-retrieval method using the standard photoelectron streaking technique where an attosecond pulse is converted into its electron replica through photoionization of atoms in the presence of a time-delayed infrared laser. The iterative algorithm allows accurate reconstruction of the spectral phase of light pulses, from the extreme-ultraviolet (XUV) to soft X-rays, with pulse durations from hundreds down to a few tens of attoseconds. At the same time, the streaking laser fields, including short pulses that span a few octaves, can also be accurately retrieved. Such well-characterized single attosecond pulses in the XUV to the soft X-ray region are required for time-resolved probing of inner-shell electronic dynamics of matter at their own timescale of a few tens of attoseconds.

Quantifying Decoherence in Attosecond Metrology

“…Moreover, with the current trend to decrease the duration of attosecond sources and, thus, to broaden the XUV spectrum, attosecond photoionization experiments will naturally involve more and more electronic shells, making routine the creation of multichannel EWPs. In this context, an important improvement will be to adapt Mixed FROG to account for the exact influence of the laser field on broadband EWPs as has been done in the fully coherent case [8,9].…”

“…This conceptual shift has not yet been introduced in attosecond metrology. The conventional scenario underlying present measurement techniques is fully coherent: in reconstruction of attosecond beatings by interference of two-photon transitions (RABBIT) [1], attosecond streaking [2,3], frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG CRAB) [4][5][6], and phase retrieval by omega oscillation filtering (PROOF) [7], and, in most other techniques [8,9], the recovered information is the temporal (or, equivalently, spectral) amplitude and phase of an attosecond extreme-ultraviolet (XUV) waveform. Generally, the XUV pulse is first converted into an electron wave packet (EWP) via photoionization in the presence of a laser pulse with a controlled delay [10,11].…”

Attosecond Light Sources in the Water Window

“…Keathley et al recently proposed a technique named Volkov transform generalized projection algorithm that does not require Fourier transform and only apply least squared minimization algorithm in the frequency domain, therefore circumvents the needs for CMA [61]. Very recently, Zhao et al also proposed a phase retrieval algorithm that does not require CMA and is applicable to broadband soft x-ray attosecond pulses [62]. This technique expands the unknowns -phase of the attosecond pulse and IR field-in terms of B spline functions and uses genetic algorithm to retrieve the coefficients of the B spline functions and therefore retrieves the phase of the attosecond pulse.…”

Method for spectral phase retrieval of single attosecond pulses utilizing the autocorrelation of photoelectron streaking spectra

“…For broadband pulses, the central momentum approximation is no longer applicable. Three methods have been proposed beyond the FROG-CRAB: PROOF [11], PROBP [12], and VTGPA [13]. All of these algorithms are based on iterative methods.…”