Water window
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Streaking of 43-attosecond soft-X-ray pulses generated by a passively CEP-stable mid-infrared driver Open
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…
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Attosecond science based on high harmonic generation from gases and solids Open
Recent progress in high power ultrafast short-wave and mid-wave infrared lasers has enabled gas-phase high harmonic generation (HHG) in the water window and beyond, as well as the demonstration of HHG in condensed matter. In this Perspecti…
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0.5-keV Soft X-ray attosecond continua Open
Attosecond light pulses in the extreme ultraviolet have drawn a great deal of attention due to their ability to interrogate electronic dynamics in real time. Nevertheless, to follow charge dynamics and excitations in materials, element sel…
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High-flux soft x-ray harmonic generation from ionization-shaped few-cycle laser pulses Open
X-ray harmonics made with long-wavelength lasers reach higher fluxes and photon energies when plasma effects dominate.
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Attosecond streaking in the water window: A new regime of attosecond pulse characterization Open
We report on the first streaking measurement of water-window attosecond pulses generated via highharmonic generation, driven by sub-2-cycle, carrier-to-envelope-phase-stable, 1850-nm laser pulses. Both the central photon energy and the ene…
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Soft X-Ray Second Harmonic Generation as an Interfacial Probe Open
Nonlinear optical processes at soft x-ray wavelengths have remained largely unexplored due to the lack of available light sources with the requisite intensity and coherence. Here we report the observation of soft x-ray second harmonic gene…
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Laboratory water-window x-ray microscopy Open
Soft x-ray microscopy in the water window ) is an emerging and unique tool for 2D and 3D imaging of unstained intact cellular samples in their near-native state with few-10-nm detail. However, present microscopes rely on the hi…
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High efficiency ultrafast water-window harmonic generation for single-shot soft X-ray spectroscopy Open
Fully coherent, soft X-ray attosecond pulses are now available through high-order harmonic generation (HHG); however, the output energy is insufficient for various applications, such as attosecond-scale soft X-ray nonlinear experiments, th…
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Status of the SXFEL Facility Open
The Shanghai soft X-ray Free-Electron Laser facility (SXFEL) is being developed in two steps; the SXFEL test facility (SXFEL-TF), and the SXFEL user facility (SXFEL-UF). The SXFEL-TF is a critical development step towards the construction …
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Water-window soft x-ray high-harmonic generation up to the nitrogen K-edge driven by a kHz, 2.1<i>μ</i>m OPCPA source Open
We report the generation of coherent water-window soft x-ray harmonics in a neon-filled semiinfinite gas cell driven by a femtosecond multi-mJ mid-infrared optical parametric chirped-pulse amplification (OPCPA) system at a 1 kHz repetition…
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27 W 2.1 µm OPCPA system for coherent soft X-ray generation operating at 10 kHz Open
We developed a high power optical parametric chirped-pulse amplification (OPCPA) system at 2.1 µm harnessing a 500 W Yb:YAG thin disk laser as the only pump and signal generation source. The OPCPA system operates at 10 kHz with a single pu…
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Femtosecond Soft-X-ray Absorption Spectroscopy of Liquids with a Water-Window High-Harmonic Source Open
Femtosecond X-ray absorption spectroscopy (XAS) is a powerful method to investigate the dynamical behavior of a system after photoabsorption in real time. So far, the application of this technique has remained limited to large-scale facili…
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Phase-retrieval algorithm for the characterization of broadband single attosecond pulses Open
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 …
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Phase-Matching for Generation of Isolated Attosecond XUV and Soft-X-Ray Pulses with Few-Cycle Drivers Open
Isolated attosecond pulses (IAPs) produced through laser-driven high-harmonic generation (HHG) hold promise for unprecedented insight into physical, chemical, and biological processes via attosecond x-ray diffraction and spectroscopy with …
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Metrology of Time-Domain Soft X-Ray Attosecond Pulses and Reevaluation of Pulse Durations of Three Recent Experiments Open
Attosecond pulses in the soft-X-ray (SXR) to water-window energy region offer\nthe tools for creating and studying target specific localized inner-shell\nelectrons or holes in materials, enable monitoring or controlling charge and\nenergy …
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High reflectance Cr/V multilayer with B_4C barrier layer for water window wavelength region Open
To develop the high reflectance mirror for the short wavelength range of the water window region (λ=2.42-2.73 nm), Cr/V multilayers with B4C barrier layers are studied. The grazing incidence x-ray reflectometry results show that the multil…
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Isolated broadband attosecond pulse generation with near- and mid-infrared driver pulses via time-gated phase matching Open
We present a theoretical analysis of the time-gated phase matching (ionization gating) mechanism in high-order harmonic generation for the isolation of attosecond pulses at near-infrared and mid-infrared driver wavelengths, for both few-cy…
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Bright attosecond soft X-ray pulse trains by transient phase-matching in two-color high-order harmonic generation Open
We study two-color high-order harmonic generation in Neon with 790 nm and 1300 nm driving laser fields and observe an extreme-ultraviolet continuum that extends to photon energies of 160 eV. Using a 6-mm-long, high pressure gas cell, we op…
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Fabrication and characterization of free-standing, high-line-density transmission gratings for the vacuum UV to soft X-ray range Open
We present state-of-the-art high resolution transmission gratings, applicable for spectroscopy in the vacuum ultraviolet (VUV) and the soft X-ray (SRX) wavelength range, fabricated with a novel process using ultraviolet based nano imprint …
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Resonance enhanced high-order harmonic generation in H2+ by two sequential laser pulses Open
We investigate high-order harmonic generation in H2+ by using two sequential laser pulses, which consist of a 800-nm pump pulse and a time-delayed 1600-nm probe pulse. Based on the solution of the time-dependent Schrödinger equation, we de…
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Extension of water-window harmonic cutoff by laser defocusing-assisted phase matching Open
We extend a recently demonstrated scheme [Optica4, 976 (2017)OPTIC82334-253610.1364/OPTICA.4.000976] to overcome the limit of conventional harmonic cutoff for different pulse durations, laser wavelengths, and gas targets. By tuning the tru…
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Quantitative ptychographic bio-imaging in the water window Open
Coherent X-ray ptychography is a tool for highly dose efficient lensless nano-imaging of biological samples. We have used partially coherent soft X-ray synchrotron radiation to obtain a quantitative image of a laterally extended, dried, an…
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High Reflectance Nanoscale V/Sc Multilayer for Soft X-ray Water Window Region Open
V/Sc multilayer is experimentally demonstrated for the first time as a high reflectance mirror for the soft X-ray water window region. It primarily works at above the Sc-L edge (λ = 3.11 nm) under near normal incidence while a second peak …
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Attosecond soft X-ray high harmonic generation Open
High harmonic generation (HHG) of an intense laser pulse is a highly nonlinear optical phenomenon that provides the only proven source of tabletop attosecond pulses, and it is the key technology in attosecond science. Recent developments i…
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Quasi-supercontinuum source in the extreme ultraviolet using multiple frequency combs from high-harmonic generation Open
A quasi-supercontinuum source in the extreme ultraviolet (XUV) is demonstrated using a table-top femtosecond laser and a tunable optical parametric amplifier (OPA) as a driver for high-harmonic generation (HHG). The harmonic radiation, whi…
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Short-Period Multilayer X-ray Mirrors for “Water” and “Carbon Windows” Wavelengths Open
This review paper summarizes and provides an overview of our recent studies related to two types of short-period multilayer X-ray mirrors, W/B4C and Co/C. It deals with the experimental observation of the layer intermixing effects and how …
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Robust enhancement of high harmonic generation via attosecond control of ionization Open
High-harmonic generation (HHG) is a powerful tool to generate coherent attosecond light pulses in the extreme ultraviolet. However, the low conversion efficiency of HHG at the single atom level poses a significant practical limitation for …
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FLASH2: Operation, beamlines, and photon diagnostics Open
FLASH2, a major extension of the soft X-ray free-electron laser FLASH at DESY, turns FLASH into a multi-user FEL facility. A new undulator line is located in a separate accelerator tunnel and driven additionally by the FLASH linear acceler…
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Water window ptychographic imaging with characterized coherent X-rays Open
A ptychographical coherent diffractive imaging experiment in the water window with focused soft X-rays at 500 eV is reported. An X-ray beam with high degree of coherence was selected for ptychography at the P04 beamline of PETRA III synchr…
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Facile formulation of a long-wavelength cyanine for optical imaging in the second near-infrared window Open
A dozen commercial NIR-II dyes are screened for simple formulation and one is applied for in vivo optical imaging in mice.