Streaking of 43-attosecond soft-X-ray pulses generated by a passively CEP-stable mid-infrared driver

Abstract

Attosecond metrology has so far largely remained limited to titanium:sapphire lasers combined with an active stabilization of the carrier-envelope phase (CEP). These sources limit the achievable photon energy to ∼100 eV which is too low to access X-ray absorption edges of most second- and third-row elements which are central to chemistry, biology and material science. Therefore, intense efforts are underway to extend attosecond metrology to the soft-X-ray (SXR) domain using mid-infrared (mid-IR) drivers. Here, we introduce and experimentally demonstrate a method that solves the long-standing problem of the complete temporal characterization of ultra-broadband (≫10 eV) attosecond pulses. We generalize the recently proposed Volkov-transform generalized projection algorithm (VTGPA) to the case of multiple overlapping photoelectron spectra and demonstrate its application to isolated attosecond pulses. This new approach overcomes all key limitations of previous attosecond-pulse reconstruction methods, in particular the central-momentum approximation (CMA), and it incorporates the physical, complex-valued and energy-dependent photoionization matrix elements. These properties make our approach general and particularly suitable for attosecond supercontinua of arbitrary bandwidth. We apply this method to attosecond SXR pulses generated from a two-cycle mid-IR driver, covering a bandwidth of ∼100 eV and reaching photon energies up to 180 eV. We extract an SXR pulse duration of (43±1) as from our streaking measurements, defining a new world record. Our results prove that the popular and broadly available scheme of post-compressing the output of white-light-seeded optical parametric amplifiers is adequate to produce high-contrast isolated attosecond pulses covering the L-edges of silicon, phosphorous and sulfur. Our new reconstruction method and experimental results open the path to the production and characterization of attosecond pulses lasting less than one atomic unit of time (24 as) and covering X-ray absorption edges of most light elements.

Charge migration and charge transfer in molecular systems

“…Shortly after the Nobel Prize was awarded to Zewail in 1999 for the development of femtochemistry, the first experiments with attosecond laser pulses were reported, 5,6 marking the beginning of attosecond science. The shortest pulse duration reported to date amounts to only 43 attoseconds 276 . Whereas femtosecond time-resolved experiments are widely applied to study charge-transfer problems, as also shown in this review, this area has only recently moved into the focus of attosecond spectroscopy.…”

Collinear setup for delay control in two-color attosecond measurements

“…Ultrashort laser sources are unique technological tools to resolve in time laser-matter dynamics on ultrafast timescales [1]. Nowadays, the highest temporal resolution of pump-probe experiments lies in the attosecond (1 as = 10 −18 s) domain and it is provided by the availability of ultrashort extreme ultraviolet (XUV) and x-ray pulses delivered either by high-order harmonic generation (HHG) in gases [2][3][4] or by Free-Electron Lasers [5,6]. HHG-based XUV attosecond pulses are routinely used in time-resolved pump-probe spectroscopic techniques to initiate dynamics, which are then probed by a second pulse at a later time.…”

Absorption of ultrashort electromagnetic pulses in plasma with inhomogeneous distribution of density and temperature

“…[1,2] Such successes necessitate both theoretical and experimental studies of processes of USP interaction with various objects. [1,2] Such successes necessitate both theoretical and experimental studies of processes of USP interaction with various objects.…”

“…The progress in development of the technique of generation of ultrashort electromagnetic pulses (USP) has resulted in creation of sources that can form pulses of femtosecond and attosecond duration. [1,2] Such successes necessitate both theoretical and experimental studies of processes of USP interaction with various objects. [3][4][5] One of the promising objects of USP interaction with a substance is plasma.…”