2017/10/24 by Thomas Gaumnitz, Arohi Jain, Yoann Pertot +4 · 557 citations
Physics and Astronomy · #Advanced Fiber Laser Technologies #Attosecond #Diffraction #Infrared #Laser #Laser-Matter Interactions and Applications #Laser-Plasma Interactions and Diagnostics #Materials science #Optics #Physics #Ptychography #Soft X-rays #Streaking #Ultrashort pulse #Water window #X-ray
paper · doi:10.1364/oe.25.027506
published in Optics Express 25(22), 27506 (Optica Publishing Group)
openalex publication_date 2017/10/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
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.