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F Labaye, M Gaponenko, V J Wittwer, A Diebold, C Paradis, N Modsching, L Merceron, F Emaury, I J Graumann, C R Phillips, C J Saraceno, C Kränkel, U Keller, T Südmeyer
We demonstrate a compact extreme ultraviolet (XUV) source based on high-harmonic generation (HHG) driven directly inside the cavity of a mode-locked thin-disk laser oscillator. The laser is directly diode-pumped at a power of only 51 W and operates at a wavelength of 1034 nm and a 17.35 MHz repetition rate. We drive HHG in a high-pressure xenon gas jet with an intracavity peak intensity of 2.8×1013  W/cm2 and 320 W of intracavity average power. Despite the high-pressure gas jet, the laser operates at high stability...
December 15, 2017: Optics Letters
M Kübel, Z Dube, A Yu Naumov, M Spanner, G G Paulus, M F Kling, D M Villeneuve, P B Corkum, A Staudte
Ionization of an atom or molecule by a strong laser field produces suboptical cycle wave packets whose control has given rise to attosecond science. The final states of the wave packets depend on ionization and deflection by the laser field, which are convoluted in conventional experiments. Here, we demonstrate a technique enabling efficient electron deflection, separate from the field driving strong-field ionization. Using a midinfrared deflection field permits one to distinguish electron wave packets generated at different field maxima of an intense few-cycle visible laser pulse...
November 3, 2017: Physical Review Letters
Ryoichi Hajima, Ryoji Nagai
We propose a scheme to generate carrier-envelope-phase (CEP) stabilized few-cycle optical pulses from a free-electron laser oscillator. The CEP stabilization is realized by the continuous injection of CEP-stabilized seed pulses from an external laser to the free-electron laser oscillator whose cavity length is perfectly synchronized to the electron bunch repetition. Operated at a midinfrared wavelength, the proposed method is able to drive a photon source based on high harmonic generation (HHG) to explore the generation of isolated attosecond pulses at photon energies above 1 keV with a repetition of >10  MHz...
November 17, 2017: Physical Review Letters
Denitsa Baykusheva, Simon Brennecke, Manfred Lein, Hans Jakob Wörner
High-harmonic spectroscopy driven by circularly polarized laser pulses and their counterrotating second harmonic is a new branch of attosecond science which currently lacks quantitative interpretations. We extend this technique to the midinfrared regime and record detailed high-harmonic spectra of several rare-gas atoms. These results are compared with the solution of the Schrödinger equation in three dimensions and calculations based on the strong-field approximation that incorporate accurate scattering-wave recombination matrix elements...
November 17, 2017: Physical Review Letters
S Beaulieu, A Comby, A Clergerie, J Caillat, D Descamps, N Dudovich, B Fabre, R Géneaux, F Légaré, S Petit, B Pons, G Porat, T Ruchon, R Taïeb, V Blanchet, Y Mairesse
Chiral light-matter interactions have been investigated for two centuries, leading to the discovery of many chiroptical processes used for discrimination of enantiomers. Whereas most chiroptical effects result from a response of bound electrons, photoionization can produce much stronger chiral signals that manifest as asymmetries in the angular distribution of the photoelectrons along the light-propagation axis. We implemented self-referenced attosecond photoelectron interferometry to measure the temporal profile of the forward and backward electron wave packets emitted upon photoionization of camphor by circularly polarized laser pulses...
December 8, 2017: Science
Vladislav V Serov, Anatoli S Kheifets
We solve the time-dependent Schrödinger equation describing a water molecule driven by a superposition of the extreme ultraviolet and IR pulses typical for a reconstruction of attosecond beating by interference of two-photon transitions experiment. This solution is obtained by a combination of the time-dependent coordinate scaling and the density functional theory with self-interaction correction. Results of this solution are used to determine the time delay in photoionization of the water and hydrogen molecules...
November 28, 2017: Journal of Chemical Physics
Zhou Wang, Hyunwook Park, Yu Hang Lai, Junliang Xu, Cosmin I Blaga, Fengyuan Yang, Pierre Agostini, Louis F DiMauro
High-harmonic generation from gases produces attosecond bursts and enables high-harmonic spectroscopy to explore electron dynamics in atoms and molecules. Recently, high-harmonic generation from solids has been reported, resulting in novel phenomena and unique control of the emission, absent in gas-phase media. Here we investigate high harmonics from semiconductors with controllable induced photo-carrier densities, as well as the driving wavelengths. We demonstrate that the dominant generation mechanism can be identified by monitoring the variation of the harmonic spectra with the carrier density...
November 22, 2017: Nature Communications
Daeheum Cho, Jeremy R Rouxel, Markus Kowalewski, Jin Yong Lee, Shaul Mukamel
With the advancement of high quality X-ray sources, it is now possible to create a molecular movie by following the electronic dynamics in real-time and real-space through time resolved X-ray diffraction. Here, we employ real-time time-dependent density functional theory (RT-TDDFT) to simulate the electronic dynamics after an impulse core or valence ionization in the glycine-phenylalanine (GF) dipeptide. The simulation yields the time-evolving dipole moment, the charge density, and the time-resolved X-ray diffraction signals...
November 15, 2017: Journal of Chemical Theory and Computation
Nickolai Zhavoronkov, Mikhail Ivanov
Attosecond (1  as=10(-18)  s) pulses produced through high harmonic generation (HHG) are a basis for studies of electron dynamics during light-matter interaction on an electron's natural time scale. Extensively exploited HHG technology has, however, a few unsolved problems, where producing of circularly polarized or chiral attosecond pulses belongs to them. We have demonstrated experimentally a way to control the ellipticity of attosecond pulse trains produced via HHG in two-color, bi-circular laser fields...
November 15, 2017: Optics Letters
Doron Azoury, Michael Krüger, Gal Orenstein, Henrik R Larsson, Sebastian Bauch, Barry D Bruner, Nirit Dudovich
Single-photon ionization is one of the most fundamental light matter interactions in nature, serving as a universal probe of the quantum state of matter. By probing the emitted electron, one can decode the full dynamics of the interaction. When photo-ionization is evolving in the presence of a strong laser field, the fundamental properties of the mechanism can be signicantly altered. Here we demonstrate how the liberated electron can perform a self-probing measurement of such interaction with attosecond precision...
November 13, 2017: Nature Communications
Calley N Eads, Dmytro Bandak, Mahesh R Neupane, Dennis Nordlund, Oliver L A Monti
Strong quantum confinement effects lead to striking new physics in two-dimensional materials such as graphene or transition metal dichalcogenides. While spectroscopic fingerprints of such quantum confinement have been demonstrated widely, the consequences for carrier dynamics are at present less clear, particularly on ultrafast timescales. This is important for tailoring, probing, and understanding spin and electron dynamics in layered and two-dimensional materials even in cases where the desired bandgap engineering has been achieved...
November 8, 2017: Nature Communications
Kazuo Takatsuka
In light of the rapid progress of ultrafast chemical dynamics driven by the pulse lasers having width as short as several tens of attoseconds, we herein develop a theory of nonadiabatic electron wavepacket dynamics in condensed phases, with which to directly track the dynamics of electronic-state mixing such as electron transfer in liquid solvents. Toward this goal, we combine a theory of path-branching representation for nonadiabatic electron wavepacket dynamics in vacuum {a mixed quantum-classical representation, Yonehara and Takatsuka [J...
November 7, 2017: Journal of Chemical Physics
M Isinger, R J Squibb, D Busto, S Zhong, A Harth, D Kroon, S Nandi, C L Arnold, M Miranda, J M Dahlström, E Lindroth, R Feifel, M Gisselbrecht, A L'Huillier
Ultrafast processes in matter, such as the electron emission after light absorption, can now be studied using ultrashort light pulses of attosecond duration (10(-18) seconds) in the extreme ultraviolet spectral range. The lack of spectral resolution due to the use of short light pulses has raised issues in the interpretation of the experimental results and the comparison with theoretical calculations. We determine photoionization time delays in neon atoms over a 40-electron volt energy range with an interferometric technique combining high temporal and spectral resolution...
November 17, 2017: Science
Thomas Gaumnitz, Arohi Jain, Yoann Pertot, Martin Huppert, Inga Jordan, Fernando Ardana-Lamas, Hans Jakob Wörner
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...
October 30, 2017: Optics Express
Johannes Passig, Sergey Zherebtsov, Robert Irsig, Mathias Arbeiter, Christian Peltz, Sebastian Göde, Slawomir Skruszewicz, Karl-Heinz Meiwes-Broer, Josef Tiggesbäumker, Matthias F Kling, Thomas Fennel
In the strong-field photoemission from atoms, molecules, and surfaces, the fastest electrons emerge from tunneling and subsequent field-driven recollision, followed by elastic backscattering. This rescattering picture is central to attosecond science and enables control of the electron's trajectory via the sub-cycle evolution of the laser electric field. Here we reveal a so far unexplored route for waveform-controlled electron acceleration emerging from forward rescattering in resonant plasmonic systems. We studied plasmon-enhanced photoemission from silver clusters and found that the directional acceleration can be controlled up to high kinetic energy with the relative phase of a two-color laser field...
October 30, 2017: Nature Communications
M C E Galbraith, S Scheit, N V Golubev, G Reitsma, N Zhavoronkov, V Despré, F Lépine, A I Kuleff, M J J Vrakking, O Kornilov, H Köppel, J Mikosch
Observing the crucial first few femtoseconds of photochemical reactions requires tools typically not available in the femtochemistry toolkit. Such dynamics are now within reach with the instruments provided by attosecond science. Here, we apply experimental and theoretical methods to assess the ultrafast nonadiabatic vibronic processes in a prototypical complex system-the excited benzene cation. We use few-femtosecond duration extreme ultraviolet and visible/near-infrared laser pulses to prepare and probe excited cationic states and observe two relaxation timescales of 11 ± 3 fs and 110 ± 20 fs...
October 18, 2017: Nature Communications
Xin Tang, Shujing Chen, Chengyou Lin, Yingchun Ding
In this paper, we present a design method of broadband reflective circular polarizer (BRCP) in the extreme ultraviolet (EUV) region. By using this method, we designed three BRCPs with a 6, 12 and 18 eV bandwidth, respectively. Then, we investigated the performances of designed BRCPs in theory. The results indicated that the reflected lights of these BRCPs all showed a nearly 100% circular polarization degree and considerable circular reflection in their design band. In addition, we also studied the origin of high circular polarization degree by analyzing the phase shift and the reflectivity ratio between s- and p-polarized lights induced by the reflection of BRCPs...
September 18, 2017: Optics Express
Han-Zhen Li, Tong-Pu Yu, Li-Xiang Hu, Yan Yin, De-Bin Zou, Jian-Xun Liu, Wei-Quan Wang, Shun Hu, Fu-Qiu Shao
We propose a novel scheme to generate ultra-bright ultra-short γ-ray flashes and high-energy-density attosecond positron bunches by using multi-dimensional particle-in-cell simulations with quantum electrodynamics effects incorporated. By irradiating a 10 PW laser pulse with an intensity of 10(23) W/cm(2) onto a micro-wire target, surface electrons are dragged-out of the micro-wire and are effectively accelerated to several GeV energies by the laser ponderomotive force, forming relativistic attosecond electron bunches...
September 4, 2017: Optics Express
Jin-Bin Li, Xiao Zhang, Sheng-Jun Yue, Hong-Mei Wu, Bi-Tao Hu, Hong-Chuan Du
We theoretically investigate high-order harmonic generation (HHG) from solids in two-color fields. It is found that under the premise of maintaining the same amplitude, the intensity of the second plateau can be enhanced by two to three orders in a proper two-color field compared with the result in the monochromatic field with the same frequency as the driving pulse of the two-color field. This can be attributed to the fact that most excited electrons can be driven to the top of the first conduction band due to the larger vector potential of the two-color fields, which leads to the higher electron population of upper conduction bands...
August 7, 2017: Optics Express
Jie Li, Xiaoming Ren, Yanchun Yin, Kun Zhao, Andrew Chew, Yan Cheng, Eric Cunningham, Yang Wang, Shuyuan Hu, Yi Wu, Michael Chini, Zenghu Chang
Nature Communications 8:186 doi: 10.1038/s41467-017-00321-0 (2017); Article published online: 4 August 2017.
October 2, 2017: Nature Communications
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