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  • 1. Aladi, M.
    et al.
    Bolla, R.
    Cardenas, D. E.
    Veisz, László
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Foldes, I. B.
    Cluster size distributions in gas jets for different nozzle geometries2017In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 12, article id C06020Article in journal (Refereed)
    Abstract [en]

    Cluster size distributions were investigated in case of different nozzle geometries in argon and xenon using Rayleigh scattering diagnostics. Different nozzle geometries result in different behaviour, therefore both spatial- and temporal cluster size distributions were studied to obtain a well-characterized cluster target. It is shown that the generally used Hagena scaling can result in a significant deviation from the observed data and the behaviour cannot be described by a single material condensation parameter. The results along with the nanoplasma model applied to the data of previous high harmonic generation experiments allow the independent measurement of cluster size and cluster density.

  • 2. Amotchkina, Tatiana
    et al.
    Trubetskov, Michael K.
    Pervak, Yurij
    Veisz, Laszlo
    Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany.
    Pervak, Vladimir
    Stress compensation with antireflection coatings for ultrafast laser applications: from theory to practice2014In: Optics Express, E-ISSN 1094-4087, Vol. 22, no 24, p. 30387-30393Article in journal (Refereed)
    Abstract [en]

    Each complicated coating, in particular, a dispersive mirror consists of dozens of layers. Thin films layers have mechanical stresses. After summing up stresses from all layers, the resulting stress is high enough to bend even a relatively thick substrate. To avoid this effect we suggest depositing an antireflection coating (AR) at the back-side of the substrate which together with suppression of unwanted reflections from the back side will also compensate this stress. We demonstrate unique, extremely thick and sophisticated AR coating consisting of 71 layers with the total physical thickness of 7.5 µm. This AR coating completely compensates stress from the dispersive mirror coated on the front side and minimizes unwanted reflections.

  • 3. Bergues, B.
    et al.
    Rivas, D. E.
    Weidman, M.
    Muschet, Alexander
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Helml, W.
    Guggenmos, A.
    Pervak, V.
    Kleineberg, U.
    Marcus, G.
    Kienberger, R.
    Charalambidis, D.
    Tzallas, P.
    Schröder, H.
    Krausz, F.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Tabletop nonlinear optics in the 100-eV spectral region2018In: Optica, ISSN 2334-2536, Vol. 5, no 3, p. 237-242Article in journal (Refereed)
    Abstract [en]

    Nonlinear light-matter interactions in the extreme ultraviolet (XUV) are a prerequisite to perform XUV-pump/XUV-probe spectroscopy of core electrons. Such interactions are now routinely investigated at free-electron laser (FEL) facilities. Yet, electron dynamics are often too fast to be captured with the femtosecond resolution of state-of-the-art FELs. Attosecond pulses from laser-driven XUV-sources offer the necessary temporal resolution. However, intense attosecond pulses supporting nonlinear processes have only been available for photon energy below 50 eV, precluding XUV-pump/XUV-probe investigation of typical inner-shell processes. Here, we surpass this limitation by demonstrating two-photon absorption from inner electronic shells of xenon at photon energies around 93 eV and 115 eV. This advance opens the door for attosecond real-time observation of nonlinear electron dynamics deep inside atoms.

  • 4. Bergues, B.
    et al.
    Rivas, D. E.
    Weidman, M.
    Muschet, Alexander
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, 85748, Garching, Germany.
    Helml, W.
    Guggenmos, A.
    Pervak, V.
    Matyba, Piotr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Kleineberg, U.
    Marcus, G.
    Kienberger, R.
    Charalambidis, D.
    Tzallas, P.
    Schröder, H.
    Krausz, F.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Towards Attosecond XUV-Pump XUV-Probe Measurements in the 100-eV Region2017In: 2017 Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), IEEE, 2017Conference paper (Refereed)
  • 5.
    Bergues, B.
    et al.
    Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, Garching, Germany; Physics Department, Ludwig-Maximilians-Universität München, Am Couloumbwall 1, Garching, Germany.
    Rivas, D.E.
    Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, Garching, Germany; Physics Department, Ludwig-Maximilians-Universität München, Am Couloumbwall 1, Garching, Germany.
    Weidman, M.
    Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, Garching, Germany.
    Muschet, Alexander
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, Garching, Germany.
    Helml, W.
    Physics Department, Technische Universität München, James-Frank-Str. 1, Garching, Germany.
    Guggenmos, A.
    Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, Garching, Germany; Physics Department, Ludwig-Maximilians-Universität München, Am Couloumbwall 1, Garching, Germany.
    Pervak, V.
    Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, Garching, Germany; Physics Department, Ludwig-Maximilians-Universität München, Am Couloumbwall 1, Garching, Germany.
    Kleineberg, U.
    Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, Garching, Germany; Physics Department, Ludwig-Maximilians-Universität München, Am Couloumbwall 1, Garching, Germany.
    Marcus, G.
    Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, Garching, Germany; The Hebrew University of Jerusalem, Jerusalem, Israel.
    Kienberger, R.
    Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, Garching, Germany; Physics Department, Technische Universität München, James-Frank-Str. 1, Garching, Germany.
    Charalambidis, D.
    Foundation for Research and Technology-Hellas, Institute of Electronic Structure and Laser, PO Box 1527, Heraklion, Crete, Greece.
    Tzallas, P.
    Foundation for Research and Technology-Hellas, Institute of Electronic Structure and Laser, PO Box 1527, Heraklion, Crete, Greece.
    Schröder, H.
    Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, Garching, Germany.
    Krausz, F.
    Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, Garching, Germany; Physics Department, Ludwig-Maximilians-Universität München, Am Couloumbwall 1, Garching, Germany.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, Garching, Germany.
    Nonlinear interaction of 100-eV attosecond XUV-pulses with core electrons in Xenon2018In: Optics InfoBase Conference Papers, Optica Publishing Group , 2018, article id HM2A.6Conference paper (Refereed)
    Abstract [en]

    We demonstrate multiphoton ionization of inner-shell electrons in Xenon with 100-eV attosecond pulses. This was achieved with a novel XUV source based on high-harmonic generation in the gas phase driven with multi-TW few-cycle laser pulses.

  • 6. Björklund Svensson, Jonas
    et al.
    Guénot, Diego
    Ferri, Julien
    Ekerfelt, Henrik
    Gallardo González, Isabel
    Persson, Anders
    Svendsen, Kristoffer
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lundh, Olle
    Low-divergence femtosecond X-ray pulses from a passive plasma lens2021In: Nature Physics, ISSN 1745-2473, E-ISSN 1745-2481, Vol. 17, no 5, p. 639-645Article in journal (Refereed)
    Abstract [en]

    Electron and X-ray beams originating from compact laser-wakefield accelerators have very small source sizes that are typically on the micrometre scale. Therefore, the beam divergences are relatively high, which makes it difficult to preserve their high quality during transport to applications. To improve on this, tremendous efforts have been invested in controlling the divergence of the electron beams, but no mechanism for generating collimated X-ray beams has yet been demonstrated experimentally. Here we propose and realize a scheme where electron bunches undergoing focusing in a dense, passive plasma lens can emit X-ray pulses with divergences approaching the incoherent limit. Compared with conventional betatron emission, the divergence of this so-called plasma lens radiation is reduced by more than an order of magnitude in solid angle, while maintaining a similar number of emitted photons per electron. This X-ray source offers the possibility of producing brilliant and collimated few-femtosecond X-ray pulses for ultra-fast science, in particular for studies based on X-ray diffraction and absorption spectroscopy.Main

  • 7. Buck, A.
    et al.
    Wenz, J.
    Xu, Jiancai
    Khrennikov, K.
    Schmid, K.
    Heigoldt, M.
    Mikhailova, J. M.
    Geissler, M.
    Shen, B.
    Krausz, F.
    Karsch, S.
    Veisz, László
    Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Shock-Front Injector for High-Quality Laser-Plasma Acceleration2013In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 110, no 18, article id 185006Article in journal (Refereed)
    Abstract [en]

    We report the generation of stable and tunable electron bunches with very low absolute energy spread (ΔE≈5  MeV) accelerated in laser wakefields via injection and trapping at a sharp downward density jump produced by a shock front in a supersonic gas flow. The peak of the highly stable and reproducible electron energy spectrum was tuned over more than 1 order of magnitude, containing a charge of 1–100 pC and a charge per energy interval of more than 10  pC/MeV. Laser-plasma electron acceleration with Ti:sapphire lasers using this novel injection mechanism provides high-quality electron bunches tailored for applications.

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  • 8. Cardenas, D. E.
    et al.
    Ostermayr, T. M.
    Di Lucchio, L.
    Hofmann, L.
    Kling, M. F.
    Gibbon, P.
    Schreiber, J.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Sub-cycle dynamics in relativistic nanoplasma acceleration2019In: Scientific Reports, E-ISSN 2045-2322, Vol. 9, article id 7321Article in journal (Refereed)
    Abstract [en]

    The interaction of light with nanometer-sized solids provides the means of focusing optical radiation to sub-wavelength spatial scales with associated electric field enhancements offering new opportunities for multifaceted applications. We utilize collective effects in nanoplasmas with sub-two-cycle light pulses of extreme intensity to extend the waveform-dependent electron acceleration regime into the relativistic realm, by using 106 times higher intensity than previous works to date. Through irradiation of nanometric tungsten needles, we obtain multi-MeV energy electron bunches, whose energy and direction can be steered by the combined effect of the induced near-field and the laser field. We identified a two-step mechanism for the electron acceleration: (i) ejection within a sub-half-optical-cycle into the near-field from the target at >TVm−1 acceleration fields, and (ii) subsequent acceleration in vacuum by the intense laser field. Our observations raise the prospect of isolating and controlling relativistic attosecond electron bunches, and pave the way for next generation electron and photon sources.

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    supplementary information
  • 9.
    Cardenas, Daniel
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Garching, Germany; Ludwig-Maximilian-Universität München, Am Coulombwall 1, 85748, Garching, Germany.
    Chou, Shao-Wei
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Garching, Germany; Ludwig-Maximilian-Universität München, Am Coulombwall 1, 85748, Garching, Germany; Center for High Energy and High Field Physics, National Central University, Chungli 32001, Taiwan .
    Wallin, Erik
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Xu, J.
    Buck, A.
    Schmid, K.
    Rivas, D.E.
    Shen, B.
    Gonoskov, A.
    Marklund, M.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Electron bunch evolution in laser-wakefield acceleration2020In: Physical Review Accelerators and Beams, E-ISSN 2469-9888, Vol. 23, article id 112803Article in journal (Refereed)
    Abstract [en]

    We report on systematic and high-precision measurements of the evolution of electron beams in a laser-wakefield accelerator (LWFA). Utilizing shock-front injection, a technique providing stable, tunable and high-quality electron bunches, acceleration and deceleration of few-MeV quasimonoenergetic beams were measured with cutting-edge technology sub-5-fs and 8-fs laser pulses. We explain the observations with dephasing, an effect that fundamentally limits the performance of LWFAs. Typical density dependent electron energy evolution with 57–300  μm dephasing length and 6–20 MeV peak energy was observed and is well described by a parabolic fit. This is a promising electron source for time-resolved few-fs electron diffraction.

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  • 10. Chou, Shao-wei
    et al.
    Xu, J.
    Khrennikov, K.
    Cardenas, Daniel E.
    Wenz, J.
    Heigoldt, M.
    Hofmann, L.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck Institut für Quantenoptik, 85748 Garching, Germany.
    Karsch, S.
    Collective Deceleration of Laser-Driven Electron Bunches2016In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 117, no 14, article id 144801Article in journal (Refereed)
    Abstract [en]

    Few-fs electron bunches from laser wakefield acceleration (LWFA) can efficiently drive plasma wakefields (PWFs), as shown by their propagation through underdense plasma in two experiments. A strong and density-insensitive deceleration of the bunches has been observed in 2 mm of 1018 cm−3 density plasma with 5.1 GV=m average gradient, which is attributed to a self-driven PWF. This observation implies that the physics of PWFs, usually relying on large-scale rf accelerators as drivers, can be studied by tabletop LWFA electron sources.

  • 11.
    de Andres, Aitor
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Bhadoria, Shikha
    Marmolejo, Javier
    Muschet, Alexander
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fischer, Peter
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Barzegar, Hamid Reza
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Blackburn, Tom
    Gonoskov, Arkady
    Hanstorp, Dag
    Marklund, Mattias
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Dynamics of vacuum laser accelerated electrons from nanotipsManuscript (preprint) (Other academic)
  • 12.
    de Andres Gonzalez, Aitor
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Bhadoria, Shikha
    Department of Physics, University of Gothenburg, Origovägen 6B, Göteborg, Sweden.
    Marmolejo, Javier
    Department of Physics, University of Gothenburg, Origovägen 6B, Göteborg, Sweden.
    Muschet, Alexander
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fischer, Peter
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gonoskov, Arkady
    Department of Physics, University of Gothenburg, Origovägen 6B, Göteborg, Sweden.
    Hanstorp, Dag
    Department of Physics, University of Gothenburg, Origovägen 6B, Göteborg, Sweden.
    Marklund, Mattias
    Department of Physics, University of Gothenburg, Origovägen 6B, Göteborg, Sweden.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Vacuum laser acceleration of electrons injected from nanotips2023In: 2023 conference on lasers and electro-optics Europe and European quantum electronics conference, CLEO/Europe-EQEC 2023, Institute of Electrical and Electronics Engineers (IEEE), 2023Conference paper (Refereed)
    Abstract [en]

    Vacuum laser acceleration (VLA) is a paradigm that utilizes the strong fields of focused laser light to accelerate electrons in vacuum. Despite its conceptual simplicity and a large existing collection of theoretical studies, realizing VLA in practice has proven remarkably challenging due to the difficulties associated with efficient injection: the electrons to be accelerated must be pre-energized and temporally compressed below an optical half-cycle before timely entering the rapidly oscillating fields of the laser. Therefore, only a handful of experiments have been published up to date, and a knowledge gap remains [1-3].

  • 13.
    de Andres Gonzalez, Aitor
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Jolly, Spencer W.
    Université libre de Bruxelles, Brussels, Belgium.
    Fischer, Peter
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Muschet, Alexander A.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Schnur, Fritz
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Spatio-spectral couplings in optical parametric amplifiers2023In: Optics Express, E-ISSN 1094-4087, Vol. 31, no 8, p. 12036-12048Article in journal (Refereed)
    Abstract [en]

    Optical parametric amplification (OPA) is a powerful tool for the generation of ultrashort light pulses. However, under certain circumstances, it develops spatio-spectral couplings, color dependent aberrations that degrade the pulse properties. In this work, we present a spatio-spectral coupling generated by a non-collimated pump beam and resulting in the change of direction of the amplified signal with respect to the input seed. We experimentally characterize the effect, introduce a theoretical model to explain it as well as reproduce it through numerical simulations. It affects high-gain non-collinear OPA configurations and becomes especially relevant in sequential optical parametric synthesizers. In collinear configuration, however, beyond the direction change, also angular and spatial chirp is produced. We obtain with a synthesizer about 40% decrease in peak intensity in the experiments and local elongation of the pulse duration by more than 25% within the spatial full width at half maximum at the focus. Finally, we present strategies to correct or mitigate the coupling and demonstrate them in two different systems. Our work is important for the development of OPA-based systems as well as few-cycle sequential synthesizers.

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  • 14.
    de Andres Gonzalez, Aitor
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Jolly, Spencer W.
    Opera Photonics Group, Université Libre de Bruxelles, Brussels, Belgium.
    Muschet, Alexander A.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Schnur, Fritz
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Quere, Fabien
    LIDYL, CEA, CNRS, Université Paris-Saclay, CEA Saclay, Gif-sur-Yvette, France.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Simple measurement technique for spatio-temporal couplings in few-cycle pulses2022In: The International Conference on Ultrafast Phenomena (UP) 2022, Optica Publishing Group (formerly OSA) , 2022, article id Tu4A.52Conference paper (Other academic)
    Abstract [en]

    We report on the detection of spatio-temporal couplings in a 700-1000 nm NOPA using an optimized characterization method. The technique is performed during normal focus observation and requires little additional hardware.

  • 15. Dombi, Peter
    et al.
    Rácz, Peter
    Veisz, László
    Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Baum, Peter
    Conversion of chirp in fiber compression2014In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 39, no 8, p. 2232-2235Article in journal (Refereed)
    Abstract [en]

    Focusing positively chirped femtosecond pulses into nonlinear fibers provides significant spectral broadening and compression at higher pulse energies than achievable conventionally because self-focusing and damage are avoided. Here, we investigate the transfer of input to output chirp in such an arrangement. Our measurements show that the group delay dispersion of the output pulse, originating from the nonlinearities, is considerably reduced as compared to the initial value, by about a factor of 10. The mechanism of chirp reduction is understood by an interplay of self-phase modulation with initial chirp within the fiber. A simple model calculation based on this picture yields satisfactory agreement with the observations and predicts significant chirp reduction for input pulses up to the μJ regime. In practice, the reduction of chirp observed here allows for compressing the spectrally broadened intense pulses by ultrabroadband dispersive multilayer mirrors of quite moderate dispersion.

  • 16.
    Fischer, Peter
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    de Andres Gonzalez, Aitor
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    In situ characterization of phase-matching conditions in non-collinear OPA / OPCPA2022In: Optica High-brightness Sources and Light-driven Interactions Congress 2022, Optica Publishing Group , 2022, article id HW6B.3Conference paper (Refereed)
    Abstract [en]

    Optimization and simulation of non-collinear ultra-broadband optical parametric chirped pulse amplification setups rely on exact knowledge of the phase matching conditions. We present a method for their accurate retrieval by deterministic angular jitter and Monte-Carlo simulations.

  • 17.
    Fischer, Peter
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Muschet, Alexander
    Umeå University, Faculty of Science and Technology, Department of Physics.
    de Andres Gonzalez, Aitor
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Schnur, Fritz
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Salh, Roushdey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sub-two-cycle 100 TW optical parametric synthesizerManuscript (preprint) (Other academic)
  • 18.
    Fischer, Peter
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Muschet, Alexander
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lang, Tino
    Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.
    Salh, Roushdey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Optimization of Optical Parametric Chirped-pulse Amplification2021In: 2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021, IEEE Lasers and Electro-Optics Society, 2021, article id cg_6_2Conference paper (Refereed)
    Abstract [en]

    Optical parametric chirped-pulse amplification (OPCPA) [1] is an established light amplification technique with many beneficial properties, like high single pass gain, scalability, large spectral bandwidth, tunability and good conversion efficiency. Different methods have been proposed for optimization of conversion [2] - [4] mainly altering the pump or the crystal properties. However, seed manipulation to increase the OPCPA conversion efficiency has been only described in a general spatiotemporal field optimization theory so far [5]. Here, we show numerical and experimental results of a novel method to improve the gain saturation in an ultra-broadband OPCPA, hence conversion efficiency, by applying an adaptive spectral filter function to the seed pulses.

  • 19.
    Fischer, Peter
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Muschet, Alexander
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lang, Tino
    Salh, Roushdey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany.
    Saturation control of an optical parametric chirped-pulse amplifier2021In: Optics Express, E-ISSN 1094-4087, Vol. 29, p. 4210-4218Article in journal (Refereed)
    Abstract [en]

    Optical parametric chirped-pulse amplification (OPCPA) is a light amplification technique that provides the combination of broad spectral gain bandwidth and large energy, directly supporting few-cycle pulses with multi-terawatt (TW) peak powers. Saturation in an OPCPA increases the stability and conversion efficiency of the system. However, distinct spectral components experience different gain and do not saturate under the same conditions, which reduces performance. Here, we describe a simple and robust approach to control the saturation for all spectral components. The demonstrated optimal saturation increases the overall gain, conversion efficiency and spectral bandwidth. We experimentally obtain an improvement of the pulse energy by more than 18%. This technique is easily implemented in any existing OPCPA system with a pulse shaper to maximize its output.

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  • 20.
    Fischer, Peter
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nagy, Gergely
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Muschet, Alexander
    Umeå University, Faculty of Science and Technology, Department of Physics.
    de Andres Gonzalez, Aitor
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Salh, Roushdey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Towards a 100 TW, sub-5-fs Optical Parametric Synthesizer2020In: OSA High-brightness Sources and Light-driven Interactions Congress 2020 (EUVXRAY, HILAS, MICS): Methods for Pushing High Average Power Laser Frontiers (HM2B) / [ed] L. Assoufid, P. Naulleau, M. Couprie, T. Ishikawa, J. Rocca, C. Haefner, G. Sansone, T. Metzger, F. Quéré, M. Ebrahim-Zadeh, A. Helmy, F. Laurell, and G. Leo, Optical Society of America, 2020Conference paper (Refereed)
    Abstract [en]

    We report on details of a peak-power upgrade of a sub-5-fs Optical Parametric Synthesizer towards 100TW. System design, pump pulse delaying and relay imaging system arepresented. A tailored second and third harmonic generation reaches conversion efficiencies of 80% and 60% with 80ps pump pulses.

  • 21. Guillaume, E.
    et al.
    Döpp, A.
    Thaury, C.
    Ta Phuoc, K.
    Lifschitz, A.
    Grittani, G.
    Goddet, J.-P.
    Tafzi, A.
    Chou, S.-W.
    Veisz, László
    Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Malka, V.
    Electron Rephasing in a Laser-Wakefield Accelerator2015In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 115, no 15, article id 155002Article in journal (Refereed)
    Abstract [en]

    An important limit for energy gain in laser-plasma wakefield accelerators is the dephasing length, after which the electron beam reaches the decelerating region of the wakefield and starts to decelerate. Here, we propose to manipulate the phase of the electron beam in the wakefield, in order to bring the beam back into the accelerating region, hence increasing the final beam energy. This rephasing is operated by placing an upward density step in the beam path. In a first experiment, we demonstrate the principle of this technique using a large energy spread electron beam. Then, we show that it can be used to increase the energy of monoenergetic electron beams by more than 50%.

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  • 22. Götzfried, J.
    et al.
    Döpp, A.
    Gilljohann, M. F.
    Foerster, F. M.
    Ding, H.
    Schindler, S.
    Schilling, G.
    Buck, A.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Karsch, S.
    Physics of High-Charge Electron Beams in Laser-Plasma Wakefields2020In: Physical Review X, E-ISSN 2160-3308, Vol. 10, no 4, article id 041015Article in journal (Refereed)
    Abstract [en]

    Laser wakefield acceleration (LWFA) and its particle-driven counterpart, particle or plasma wakefield acceleration (PWFA), are commonly treated as separate, though related, branches of high-gradient plasma-based acceleration. However, novel proposed schemes are increasingly residing at the interface of both concepts where the understanding of their interplay becomes crucial. Here, we present a comprehensive study of this regime, which we may term laser-plasma wakefields. Using datasets of hundreds of shots, we demonstrate the influence of beam loading on the spectral shape of electron bunches. Similar results are obtained using both 100-TW-class and few-cycle lasers, highlighting the scale invariance of the involved physical processes. Furthermore, we probe the interplay of dual electron bunches in the same or in two subsequent plasma periods under the influence of beam loading. We show that, with decreasing laser intensity, beam loading transitions to a beam-dominated regime, where the first bunch acts as the main driver of the wakefield. This transition is evidenced experimentally by a varying acceleration of a low-energy witness beam with respect to the charge of a high-energy drive beam in a spatially separate gas target. Our results also present an important step in the development of LWFA using controlled injection in a shock front. The electron beams in this study reach record performance in terms of laser-to-beam energy transfer efficiency (up to 10%), spectral charge density (regularly exceeding 10  pC MeV−1), and angular charge density (beyond 300  pC μsr−1 at 220 MeV). We provide an experimental scaling for the accelerated charge per terawatt (TW) of laser power, which approaches 2 nC at 300 TW. With the expanding availability of petawatt-class (PW) lasers, these beam parameters will become widely accessible. Thus, the physics of laser-plasma wakefields is expected to become increasingly relevant, as it provides new paths toward low-emittance beam generation for future plasma-based colliders or light sources.

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  • 23. Heissler, P.
    et al.
    Barna, A.
    Mikhailova, J. M.
    Ma, Guangjin
    Khrennikov, K.
    Karsch, S.
    Veisz, László
    Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Földes, I. B.
    Tsakiris, G. D.
    Multi‑μJ harmonic emission energy from laser‑driven plasma2015In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 118, no 2, p. 195-201Article in journal (Refereed)
    Abstract [en]

    We report on simultaneous efficiency and divergence measurements for harmonics from solid targets generated by the relativistic oscillating mirror mechanism. For a value of the normalized vector potential of aL≃1.5aL≃1.5, we demonstrate the generation of 30 μJ high-harmonic radiation in a 17±317±3 mrad divergence cone. This corresponds to a conversion efficiency of ≳≳ 10−4 in the 17–80 nm range into a well-confined beam. Presuming phase-locked harmonics, our results predict unprecedented levels of average power for a single attosecond pulse in the generated pulse train. Results of PIC simulations raise the prospect of attaining efficiencies of a few percent at higher laser intensities.

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  • 24.
    Horný, Vojtěch
    et al.
    Department of Physics, Chalmers University of Technology, Fysikgarden 1, Göteborg, Sweden; LULI, CNRS, Ecole Polytechnique, CEA, Université Paris-Saclay, UPMC Université Paris 06, Sorbonne Université, Palaiseau cedex, France.
    Veisz, László
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Generation of single attosecond relativistic electron bunch from intense laser interaction with a nanosphere2021In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 63, no 12, article id 125025Article in journal (Refereed)
    Abstract [en]

    Ultrahigh-intensity laser-plasma physics provides unique light and particle beams as well as novel physical phenomena. A recently available regime is based on the interaction between a relativistic intensity few-cycle laser pulse and a sub-wavelength-sized mass-limited plasma target. Here, we investigate the generation of electron bunches under these extreme conditions by means of particle-in-cell simulations. In a first step, up to all electrons are expelled from the nanodroplet and gain relativistic energy from time-dependent local field enhancement at the surface. After this ejection, the electrons are further accelerated as they copropagate with the laser pulse. As a result, a few, or under specific conditions isolated, pC-class relativistic attosecond electron bunches are generated with laser pulse parameters feasible at state-of-the-art laser facilities. This is particularly interesting for some applications, such as generation of attosecond x-ray pulses via Thomson backscattering.

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  • 25. Jahn, Olga
    et al.
    Leshchenko, Vyacheslav E.
    Tzallas, Paraskevas
    Kassel, Alexander
    Krueger, Mathias
    Muenzer, Andreas
    Trushin, Sergei A.
    Tsakiris, George D.
    Kahaly, Subhendu
    Kormin, Dmitrii
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Pervak, Vladimir
    Krausz, Ferenc
    Major, Zsuzsanna
    Karsch, Stefan
    Towards intense isolated attosecond pulses from relativistic surface high harmonics2019In: Optica, ISSN 2334-2536, Vol. 6, no 3, p. 280-287Article in journal (Refereed)
    Abstract [en]

    Relativistic surface high harmonics have been considered a unique source for the generation of intense isolated attosecond pulses in the extreme ultra-violet and x-ray spectral ranges. Their practical realization, however, is still a challenging task and requires identification of optimum experimental conditions and parameters. Here, we present measurements and particle-in-cell simulations to determine the optimum values for the most important parameters. In particular, we investigate the dependence of harmonics efficiency, divergence, and beam quality on the pre-plasma scale length as well as identify the optimum conditions for generation of isolated attosecond pulses by measuring the dependence of the harmonics spectrum on the carrier - envelope phase of the driving infrared field. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

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  • 26. Khrennikov, K.
    et al.
    Wenz, J.
    Buck, A.
    Xu, Jiancai
    Heigoldt, M.
    Veisz, Laszlo
    MPI für Quantenoptik, Garching, Germany.
    Karsch, S.
    Tunable All-Optical Quasimonochromatic Thomson X-Ray Sourcein the Nonlinear Regime2015In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 114, no 19, article id 195003Article in journal (Refereed)
    Abstract [en]

    We present an all-laser-driven, energy-tunable, and quasimonochromatic x-ray source based on Thomson scattering from laser-wakefield-accelerated electrons. One part of the laser beam was used to drive a few-fs bunch of quasimonoenergetic electrons, while the remainder was backscattered off the bunch at weakly relativistic intensity. When the electron energy was tuned from 17–50 MeV, narrow x-ray spectra peaking at 5–42 keV were recorded with high resolution, revealing nonlinear features. We present a large set of measurements showing the stability and practicality of our source.

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  • 27. Kolliopoulos, G.
    et al.
    Bergues, B.
    Schröder, H.
    Carpeggiani, P. A.
    Veisz, Laszlo
    Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Tsakiris, G. D.
    Charalambidis, D.
    Tzallas, P.
    Revealing quantum path details in high-field physics2014In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 90, no 1, article id 013822Article in journal (Refereed)
    Abstract [en]

    The fundamental mechanism underlying harmonic emission in the strong-field regime is governed by tunnel ionization of the atom, followed by the motion of the electron wave packet in the continuum, and finally by its recollision with the atomic core. Due to the quantum nature of the process, the properties of the electron wave packet strongly correlate with those of the emitted radiation. Here, by spatially resolving the interference pattern generated by overlapping the harmonic radiation emitted by different interfering electron quantum paths, we have succeeded in unravelling the intricacies associated with the recollision process. This has been achieved by mapping the spatial extreme-ultraviolet (EUV)-intensity distribution onto a spatial ion distribution, produced in the EUV focal area through the linear and nonlinear processes of atoms. By in situ manipulation of the intensity-dependent motion of the electron wave packets, we have been able to directly measure the difference between the harmonic emission times and electron path lengths resulting from different electron trajectories. Due to the high degree of accuracy that the present approach provides, we have been able to demonstrate the quantum nature of the recollision process. This is done by quantitatively correlating the photoemission time and the electron quantum path-length differences, taking into account the energy-momentum transfer from the driving laser field into the system. This information paves the way for electron-photon correlation studies at the attosecond time scale, while it puts the recollision process from the semiclassical prospective into a full quantum-mechanical context.

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  • 28. Kolliopoulos, G.
    et al.
    Tzallas, P.
    Bergues, B.
    Carpeggiani, P. A.
    Heissler, P.
    Schröder, H.
    Veisz, László
    Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Charalambidis, D.
    Tsakiris, G. D.
    Single-shot autocorrelator for extreme-ultraviolet radiation2014In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 31, no 5, p. 926-938Article in journal (Refereed)
    Abstract [en]

    A novel single-shot second-order autocorrelation scheme for extreme-ultraviolet radiation (XUV) is proposed. It is based on an ion-imaging technique, which provides spatial information of ionization products in the focal volume of the XUV beam. Using simple analytical and detailed numerical modeling, an evaluation toward selecting an optimum configuration has been performed. The implementation of the concept to characterize attosecond pulses is discussed, and the proposed setups are assessed.

  • 29. Kormin, Dmitrii
    et al.
    Borot, Antonin
    Ma, Guangjin
    Dallari, William
    Bergues, Boris
    Aladi, Mark
    Földes, Istvan B.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany.
    Spectral interferometry with waveform-dependent relativistic high-order harmonics from plasma surfaces2018In: Nature Communications, E-ISSN 2041-1723, Vol. 9, article id 4992Article in journal (Refereed)
    Abstract [en]

    The interaction of ultra-intense laser pulses with matter opened the way to generate the shortest light pulses available nowadays in the attosecond regime. Ionized solid surfaces, also called plasma mirrors, are promising tools to enhance the potential of attosecond sources in terms of photon energy, photon number and duration especially at relativistic laser intensities. Although the production of isolated attosecond pulses and the understanding of the underlying interactions represent a fundamental step towards the realization of such sources, these are challenging and have not yet been demonstrated. Here, we present laser-waveform-dependent high-order harmonic radiation in the extreme ultraviolet spectral range supporting well-isolated attosecond pulses, and utilize spectral interferometry to understand its relativistic generation mechanism. This unique interpretation of the measured spectra provides access to unrevealed temporal and spatial properties such as spectral phase difference between attosecond pulses and field-driven plasma surface motion during the process.

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  • 30. Kormin, Dmitrii
    et al.
    Ma, Guangjin
    Foeldes, Istvan
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Germany.
    Decryption of harmonics: how spectral interferometry reveals the structure of XUV pulse trains2019In: 2019 conference on lasers and electro-optics Europe & European quantum electronics conference (CLEO/europe-eqec), Institute of Electrical and Electronics Engineers (IEEE), 2019, article id 8872842Conference paper (Refereed)
  • 31.
    Leshchenko, V.E.
    et al.
    Max-Planck-Institut für Quantenoptik, Garching, Germany; Department für Physik, Ludwig-Maximilians-Universität München, Garching, Germany; Department of Physics, Ohio State University, OH, Columbus, United States.
    Kessel, A.
    Max-Planck-Institut für Quantenoptik, Garching, Germany; Department für Physik, Ludwig-Maximilians-Universität München, Garching, Germany.
    Jahn, O.
    Max-Planck-Institut für Quantenoptik, Garching, Germany; Department für Physik, Ludwig-Maximilians-Universität München, Garching, Germany.
    Krüger, M.
    Max-Planck-Institut für Quantenoptik, Garching, Germany; Department für Physik, Ludwig-Maximilians-Universität München, Garching, Germany.
    Münzer, A.
    Max-Planck-Institut für Quantenoptik, Garching, Germany; Department für Physik, Ludwig-Maximilians-Universität München, Garching, Germany.
    Trushin, S.A.
    Max-Planck-Institut für Quantenoptik, Garching, Germany; Department für Physik, Ludwig-Maximilians-Universität München, Garching, Germany.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Major, Zs
    Max-Planck-Institut für Quantenoptik, Garching, Germany; Department für Physik, Ludwig-Maximilians-Universität München, Garching, Germany; GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstraße 1, Darmstadt, Germany; Helmholtz-Institut Jena,, Fröbelstieg 3, Jena, Germany.
    Karsch, S.
    Max-Planck-Institut für Quantenoptik, Garching, Germany; Department für Physik, Ludwig-Maximilians-Universität München, Garching, Germany.
    Relativistic harmonics D-scan for on-target temporal characterization of intense optical pulses2019In: Ultrafast Optics 2019: Abstract Book, SPIE , 2019, p. 209-212Conference paper (Refereed)
    Abstract [en]

    Accurate knowledge of the on-target pulse intensity is one of key prerequisites for the correct interpretation of high-field experiments due to their high sensitivity to the exact value of the pulse peak intensity caused by the nonlinearity of underlying processes. There are three parameters determining the peak intensity: pulse energy, spatial and temporal energy distribution. While the detection of pulse energy and spatial profile are well established, the unambiguous temporal characterization of intense optical pulses remains a challenge especially at relativistic intensities and a few-cycle pulse duration. We report on the progress in the temporal characterization of intense laser pulses and present the relativistic surface second harmonic generation dispersion scan (RSSHG-D-scan) – a new approach allowing direct on-target temporal characterization of high-energy few-cycle optical pulses at up to relativistic intensities.

  • 32. Leshchenko, Vyacheslav E.
    et al.
    Kessel, Alexander
    Jahn, Olga
    Krüger, Mathias
    Münzer, Andreas
    Trushin, Sergei A.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany.
    Major, Zsuzsanna
    Karsch, Stefan
    On-target temporal characterization of optical pulses at relativistic intensity2019In: Light: Science & Applications, ISSN 2095-5545, E-ISSN 2047-7538, Vol. 8, article id 96Article in journal (Refereed)
    Abstract [en]

    High-field experiments are very sensitive to the exact value of the peak intensity of an optical pulse due to the nonlinearity of the underlying processes. Therefore, precise knowledge of the pulse intensity, which is mainly limited by the accuracy of the temporal characterization, is a key prerequisite for the correct interpretation of experimental data. While the detection of energy and spatial profile is well established, the unambiguous temporal characterization of intense optical pulses, another important parameter required for intensity evaluation, remains a challenge, especially at relativistic intensities and a few-cycle pulse duration. Here, we report on the progress in the temporal characterization of intense laser pulses and present the relativistic surface second harmonic generation dispersion scan (RSSHG-D-scan)—a new approach allowing direct on-target temporal characterization of high-energy, few-cycle optical pulses at relativistic intensity.

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  • 33. Leshchenko, Vyacheslav E.
    et al.
    Kessel, Alexander
    Jahn, Olga
    Krüger, Mathias
    Münzer, Andreas
    Trushin, Sergei A.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
    Major, Zsuzsanna
    Karsch, Stefan
    On-target temporal characterization of optical pulses at relativistic intensity2019In: Light: Science & Applications, ISSN 2095-5545, E-ISSN 2047-7538, Vol. 8, article id 96Article in journal (Refereed)
    Abstract [en]

    High-field experiments are very sensitive to the exact value of the peak intensity of an optical pulse due to the nonlinearity of the underlying processes. Therefore, precise knowledge of the pulse intensity, which is mainly limited by the accuracy of the temporal characterization, is a key prerequisite for the correct interpretation of experimental data. While the detection of energy and spatial profile is well established, the unambiguous temporal characterization of intense optical pulses, another important parameter required for intensity evaluation, remains a challenge, especially at relativistic intensities and a few-cycle pulse duration. Here, we report on the progress in the temporal characterization of intense laser pulses and present the relativistic surface second harmonic generation dispersion scan (RSSHG-D-scan)-a new approach allowing direct on-target temporal characterization of high-energy, few-cycle optical pulses at relativistic intensity.

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  • 34. Liu, Qingcao
    et al.
    Seiffert, Lennart
    Süssmann, Frederik
    Zherebtsov, Sergey
    Passig, Johannes
    Kessel, Alexander
    Trushin, Sergei A.
    Kling, Nora G.
    Ben-Itzhak, Itzik
    Mondes, Valerie
    Graf, Christina
    Rühl, Eckart
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Karsch, Stefan
    Rodriguez-Fernandez, Jessica
    Stockman, Mark, I
    Tiggesbaeumker, Josef
    Meiwes-Broer, Karl-Heinz
    Fennel, Thomas
    Kling, Matthias F.
    Ionization-Induced Subcycle Metallization of Nanoparticles in Few-Cycle Pulses2020In: ACS Photonics, E-ISSN 2330-4022, Vol. 7, no 11, p. 3207-3215Article in journal (Refereed)
    Abstract [en]

    Strong-field laser-matter interactions in nanoscale targets offer unique avenues for the generation and detailed characterization of matter under extreme conditions. Field-driven, subcycle ionization-induced metallization of nanoscale solids in intense laser fields has been predicted (Peltz et al. Time-Resolved X-ray Imaging of Anisotropic Nanoplasma Expansion. Phys. Rev. Lett. 2014, 113, 133401), but its observation was hampered by a lack of a smoking gun. Here, we report the ultrafast metallization of isolated dielectric and semiconducting nanoparticles under intense few-cycle laser pulses. The highest-energy electron emission is found to be a decisive proof that shows a characteristic cutoff modification to a metallic limit for intensities high enough to ignite carrier avalanching in the volume of the particles. Semiclassical Mean-field Mie Monte-Carlo transport simulations reveal the underlying dynamics and explain the observed evolution by near-field driven electron backscattering from the metallizing target.

  • 35. Lotscher, Lauryna
    et al.
    Vamos, Lenard
    Veisz, László
    Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Apolonski, Alexander
    Long-term Stability of Nonlinear Pulse Compression using Solid-core Large-mode-area Fibers2015In: Journal of Lasers, Optics & Photonics, ISSN 2469-410X, Vol. 2, no 3, article id 1000124Article in journal (Refereed)
    Abstract [en]

    Long-term stability of a laser system is crucially important for applications such as ultrafast laser spectroscopy. Unfortunately, this topic received little attention in novel pulse compression schemes. Through the ultra-stable beam pointing of the 50 kHz laser system, the long-term stability of nonlinear pulse compression (NPC) was measured for up to 17 hours at different peak powers in a fiber core. The required spectral broadening was achieved in largemode- area photonic-crystal-fibers with linearly and circularly polarized light. The optimal parameters of a NPC system operating close to the fundamental limit of the critical self-focusing peak power were found. A further compression to sub-10 fs pulses in a second fiber stage is also discussed.

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  • 36. Ma, Guangjin
    et al.
    Chen, Jingbiao
    He, Jin
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Isolated attosecond light pulse generation from plasma surfaces at varying laser intensities and incidence angles2022In: 1st International Conference on UltrafastX 2021: Proceedings, SPIE - International Society for Optical Engineering, 2022, Vol. 12291, article id 1229104Conference paper (Refereed)
    Abstract [en]

    Harmonics from relativistic laser driven plasma surfaces is a prospective high energy attosecond light source infuture XUV pump-probe experiments. Among all the schemes, the most ecient and direct way to realize anisolated attosecond pulse is through using a few-cycle laser as the driving pulse. The two goodness criteria: thelaser to harmonics energy conversion eciency and the \purity" of an isolated attosecond pulse are generallydetermined by a combination of interaction parameters. Through using particle-in-cell simulations and relativisticelectron dynamics model analyses, we explain how these two criteria are a ected by the laser intensity, incidenceangle, carrier-envelope phase, and the plasma scale length. We found that, there exist an optimal plasma scalelength and an optimal incidence angle to eciently generate harmonics and intense attosecond light pulses.When other parameters are  xed, using a moderately intense relativistic laser or using a large incidence anglecould result in a higher isolation degree as well as a broader range of controlling parameters to realize an isolatedattosecond light pulse.

  • 37. Ma, Guangjin
    et al.
    Chen, Jingbiao
    He, Jin
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Laser intensity and incidence angle dependent attosecond light pulse generation from relativistic laser plasma surfaces2022In: Sixth international symposium on laser interaction with matter (LIMIS 2022): Proceedings, SPIE - International Society for Optical Engineering, 2022, Vol. 12459, article id 124590KConference paper (Refereed)
    Abstract [en]

    Relativistic high-order harmonics from a few-cycle laser driven plasma surface is a very promising source of anintense and isolated attosecond light pulse. The laser to harmonics conversion efficiency and the “purity” ofan isolated attosecond light pulse are generally determined by a combination of interaction parameters, suchas laser intensities, incidence angles, pulse durations, carrier-envelope phases and plasma scale lengths. Wehad already previously investigated the effect of a three-parameter combination of the laser pulse duration,the carrier-envelope phase and the plasma scale length. To complement our previous work, the parametricdependence of the other two three-parameter combinations: the carrier-envelope phase, the plasma scale length,either combined with the laser intensity or the incidence angle, were systematically investigated through onedimensional particle-in-cell simulations. We found that, although the impact of parameter combinations onattosecond pulse generations is generally complicated, there exist however an optimal plasma scale length and anoptimal incidence angle to efficiently generate high-order harmonics and intense attosecond light pulses. Whenother parameters are fixed, a moderately intense relativistic laser is more advantageous to realize an isolatedattosecond light pulse in a broad controlling parameters range. And a larger incidence angle favors a higherisolation degree as well as a broader range of controlling parameters towards the generation of intense isolatedattosecond light pulses. In order to interpret these simulation results, we have modeled the correspondingrelativistic electron dynamics, using which the underlying physics are discussed.

  • 38. Ma, Guangjin
    et al.
    Dallari, William
    Borot, Antonin
    Krausz, Ferenc
    Yu, Wei
    Tsakiris, George D.
    Veisz, László
    Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses2015In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 22, no 3, article id 033105Article in journal (Refereed)
    Abstract [en]

    We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ∼100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach.

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  • 39.
    Ma, Guangjin
    et al.
    Shenzhen SoC Key Laboratory, Peking University Shenzhen Institute, PKU-HKUST Shenzhen-Hong Kong Institution, Shenzhen, China; Center for Free-Electron Laser Science, DESY, Notkestraße 85, Hamburg, Germany.
    Kormin, Dmitrii
    Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, Garching, Germany; Ludwig-Maximilians-Universität München, Am Coulombwall 1, Garching, Germany.
    Borot, Antonin
    Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, Garching, Germany.
    Dallari, William
    Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, Garching, Germany.
    Bergues, Boris
    Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, Garching, Germany; Ludwig-Maximilians-Universität München, Am Coulombwall 1, Garching, Germany.
    Aladi, Márk
    Wigner Research Centre for Physics, Hungarian Academy of Sciences, Budapest, Hungary.
    Földes, István B.
    Wigner Research Centre for Physics, Hungarian Academy of Sciences, Budapest, Hungary.
    He, Jin
    Shenzhen SoC Key Laboratory, Peking University Shenzhen Institute, PKU-HKUST Shenzhen-Hong Kong Institution, Shenzhen, China.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, Garching, Germany.
    Waveform-dependent relativistic high-order harmonics and field-driven plasma surface dynamics2019In: Ultrafast Optics 2019: Abstract Book, SPIE , 2019, p. 106-110Conference paper (Refereed)
    Abstract [en]

    Attosecond XUV-pump XUV-probe experiments demand high brightness attosecond light source benefitting from state-of-the-art ultrashort ultraintense laser technology. Current most promising route towards high energy attosecond light source is through relativistic high-order harmonic generation from plasma surfaces. In this paper, we investigate waveform-dependent relativistic high-order harmonic generation from plasma surfaces, and use spectral interferometry to understand its generation process. The unique interpretation has allowed access to unrevealed temporal structure of the generated few-pulse attotrain with evidence supporting a well-isolated attosecond pulse. It also provides a way to measure field-driven plasma surface motion in its generation process.

  • 40.
    Ma, Guangjin
    et al.
    School of Electronics Engineering and Computer Science, Peking University, Beijing, China; Shenzhen SoC Key Laboratory, PKU-HKUST Shenzhen-Hong Kong Institution, Shenzhen, China.
    Kormin, Dmitrii
    Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Li, Chunlai
    Shenzhen SoC Key Laboratory, PKU-HKUST Shenzhen-Hong Kong Institution, Shenzhen, China.
    Zhou, Zhiping
    School of Electronics Engineering and Computer Science, Peking University, Beijing, China.
    He, Jin
    School of Electronics Engineering and Computer Science, Peking University, Beijing, China; Shenzhen SoC Key Laboratory, PKU-HKUST Shenzhen-Hong Kong Institution, Shenzhen, China.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Relativistic high-order harmonic generation from laser plasmas using few-cycle laser pulses2018In: Optics InfoBase Conference Papers, Optica Publishing Group , 2018, article id Th3B.2Conference paper (Refereed)
    Abstract [en]

    We investigate relativistic high-order harmonic generation from intense few-cycle laser and plasma interactions via particle-in-cell simulations. Differences of spectral and temporal structures in XUV beam resulted from few-cycle and non-few-cycle driver pulses are compared.

  • 41. Ma, Guangjin
    et al.
    Yu, Wei
    Yu, M. Y.
    Shen, Baifei
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany.
    Intense circularly polarized attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses2016In: Optics Express, E-ISSN 1094-4087, Vol. 24, no 9, p. 10057-10065Article in journal (Refereed)
    Abstract [en]

    We have investigated the polarization of attosecond light pulses generated from relativistic few-cycle laser pulse interaction with the surface of overdense plasmas using particle-in-cell simulation. Under suitable conditions, a desired polarization state of the generated attosecond pulse can be achieved by controlling the polarization of the incident laser. In particular, an elliptically polarized laser pulse of suitable ellipticity can generate an almost circularly polarized attosecond pulse without compromising the harmonic generation efficiency. The process is thus applicable as a new tabletop circularly-polarized XUV radiation source for probing attosecond phenomena with high temporal resolution.

  • 42. Major, B.
    et al.
    Rivas, D. E.
    Bergues, B.
    Weidman, M.
    Muschet, A.
    Schröder, H.
    Korös, Cs. P.
    Balogh, E.
    Kovacs, K.
    Tosa, V.
    Krausz, F.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching, Germany .
    Varju, K.
    Investigation of high harmonic generation using a high-power, 5-fs laser in a loose-focusing geometry2017In: 2017 Conference on Lasers and Electro-Optics Europe &  European Quantum Electronics Conference (CLEO/Europe-EQEC), IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    Summary form only given. Since its first observation almost three decades ago high-order harmonic generation (HHG) in gases became a reliable source of extreme ultraviolet (XUV) pulses, which gave the possibility to study electronic processes on their natural timescale [1, 2]. While the main building blocks of the experimental setups for gas HHG are the same in almost all cases, the focusing or medium geometry varies from realization to realization based on, for example, the available laser power [3, 4].In this work we study HHG in a loose focusing geometry by focusing a ~50-mm diameter (FWHM) beam with a mirror of 16-m focal length (f-number ~320). The main subject of this analysis is to compare low pressure - long interaction length (few millibars and tens of centimeters) with high pressure - short medium (hundreds of millibars and a few millimeters) scenarios and understand the underlying reasons for the observed XUV radiation parameters. The experiments are carried out with on target 35 mJ, sub-5 fs, 740 nm central wavelength pulses provided by an optical parametric synthesizer [5], producing high-energy pulses at the 100 eV spectral region [6]. The theoretical analysis is performed by simulation code based on a three-dimensional nonadiabatic model [7,8]. The good agreement between the experimental and simulation data (see Fig. 1) allows us to use the theoretical findings to gain better insight on the exact phase-matching processes providing the observed features. This detailed description is used to draw general conclusions of the high-harmonic generation process.

  • 43.
    Muschet, Alexander A.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    de Andres, Aitor
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fischer, Peter
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Salh, Roushdey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Utilizing the temporal superresolution approach in an optical parametric synthesizer to generate multi-TW sub-4-fs light pulses2022In: Optics Express, E-ISSN 1094-4087, Vol. 30, no 3, p. 4374-4380Article in journal (Refereed)
    Abstract [en]

    The Fourier-transform limit achieved by a linear spectral phase is the typical optimum by the generation of ultrashort light pulses. It provides the highest possible intensity, however, not the shortest full width at half maximum of the pulse duration, which is relevant for many experiments. The approach for achieving shorter pulses than the original Fourier limit is termed temporal superresolution. We demonstrate this approach by shaping the spectral phase of light from an optical parametric chirped pulse amplifier and generate sub-Fourier limited pulses. We also realize it in a simpler way by controlling only the amplitude of the spectrum, producing a shorter Fourier-limited duration. Furthermore, we apply this technique to an optical parametric synthesizer and generate multi-TW sub-4-fs light pulses. This light source is a promising tool for generating intense and isolated attosecond light and electron pulses.

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  • 44.
    Muschet, Alexander A.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    de Andres Gonzalez, Aitor
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Smijesh, Nadarajan
    Umeå University, Faculty of Science and Technology, Department of Physics. Ultrafast Optics Group, School of Pure and Applied Physics, Mahatma Gandhi University, Kerala, India.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    An easy technique for focus characterization and optimization of XUV and soft X-ray pulses2022In: Applied Sciences, E-ISSN 2076-3417, Vol. 12, no 11, article id 5652Article in journal (Refereed)
    Abstract [en]

    For many applications of extreme ultraviolet (XUV) and X-ray pulses, a small focus size is crucial to reach the required intensity or spatial resolution. In this article, we present a simple way to characterize an XUV focus with a resolution of 1.85 µm. Furthermore, this technique was applied for the measurement and optimization of the focus of an ellipsoidal mirror for photon energies ranging from 18 to 150 eV generated by high-order harmonics. We envisage a broad range of applications of this approach with sub-micrometer resolution from high-harmonic sources via synchrotrons to free-electron lasers.

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  • 45.
    Muschet, Alexander
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    de Andres Gonzalez, Aitor
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fischer, Peter
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Salh, Roushdey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Veisz, László
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Generation of Multi-TW sub-4-fs Light Pulses via Temporal Superresolution in an Optical Parametric Synthesizer2022In: High Intensity Lasers and High Field Phenomena: Conference Proceedings 2022, Optica Publishing Group , 2022, article id HTh5B.1Conference paper (Refereed)
    Abstract [en]

    The spectral phase and amplitude of a multi-TW laser with a Fourier transform limit of 4.6 fs was optimized to obtain 3.9 fs pulses with >5TW, providing the most energetic sub-4-fs pulses in the world.

  • 46. Nagy, Tamas
    et al.
    Simon, peter
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    High-energy few-cycle pulses: post-compression techniques2021In: Advances in Physics: X, ISSN 2374-6149, Vol. 6, no 1, article id 1845795Article in journal (Refereed)
    Abstract [en]

    Contemporary ultrafast science requires reliable sources of high-energy few-cycle light pulses. Currently two methods are capable of generating such pulses: post compression of short laser pulses and optical parametric chirped-pulse amplification (OPCPA). Here we give a comprehensive overview on the post-compression technology based on optical Kerr-effect or ionization, with particular emphasis on energy and power scaling. Relevant types of post compression techniques are discussed including free propagation in bulk materials, multiple-plate continuum generation, multi-pass cells, filaments, photonic-crystal fibers, hollow-core fibers and self-compression techniques. We provide a short theoretical overview of the physics as well as an in-depth description of existing experimental realizations of post compression, especially those that can provide few-cycle pulse duration with mJ-scale pulse energy. The achieved experimental performances of these methods are compared in terms of important figures of merit such as pulse energy, pulse duration, peak power and average power. We give some perspectives at the end to emphasize the expected future trends of this technology.

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  • 47.
    Nana Koya, Alemayehu
    et al.
    GPL Photonics Laboratory, State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, China; Department of Physics, College of Natural and Computational Sciences, Wolaita Sodo University, Wolaita Sodo, Ethiopia.
    Romanelli, Marco
    Department of Chemical Sciences, University of Padova, Padova, Italy.
    Kuttruff, Joel
    Department of Physics, University of Konstanz, Konstanz, Germany.
    Henriksson, Nils
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stefancu, Andrei
    Nanoinstitut München, Fakultät für Physik, Ludwig-Maximilians-Universität München, München, Germany.
    Grinblat, Gustavo
    Departamento de Física, FCEN, IFIBA-CONICET, Universidad de Buenos Aires, Buenos Aires, Argentina.
    de Andres, Aitor
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Schnur, Fritz
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Vanzan, Mirko
    Department of Chemical Sciences, University of Padova, Padova, Italy.
    Marsili, Margherita
    Department of Chemical Sciences, University of Padova, Padova, Italy; Department of Physics and Astronomy, University of Bologna, Bologna, Italy.
    Rahaman, Mahfujur
    Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
    Viejo Rodríguez, Alba
    Department of Physics and Materials Science, University of Luxembourg, Luxembourg, Luxembourg.
    Tapani, Tilaike
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lin, Haifeng
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Dalga Dana, Bereket
    Department of Physics, College of Natural and Computational Sciences, Jinka University, Jinka, Ethiopia.
    Lin, Jingquan
    School of Science, Changchun University of Science and Technology, Changchun, China.
    Barbillon, Grégory
    EPF-Ecole d'Ingénieurs, Cachan, France.
    Proietti Zaccaria, Remo
    Istituto Italiano di Tecnologia, Genova, Italy.
    Brida, Daniele
    Department of Physics and Materials Science, University of Luxembourg, Luxembourg, Luxembourg.
    Jariwala, Deep
    Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
    Veisz, László
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Cortes, Emiliano
    Nanoinstitut München, Fakultät für Physik, Ludwig-Maximilians-Universität München, München, Germany.
    Corni, Stefano
    Department of Chemical Sciences, University of Padova, Padova, Italy; CNR-NANO Istituto Nanoscience, Modena, Italy.
    Garoli, Denis
    Istituto Italiano di Tecnologia, Genova, Italy.
    Maccaferri, Nicolò
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Physics and Materials Science, University of Luxembourg, Luxembourg, Luxembourg.
    Advances in ultrafast plasmonics2023In: Applied Physics Reviews, E-ISSN 1931-9401, Vol. 10, no 2, article id 021318Article, review/survey (Refereed)
    Abstract [en]

    In the past 20 years, we have reached a broad understanding of many light-driven phenomena in nanoscale systems. The temporal dynamics of the excited states are instead quite challenging to explore, and, at the same time, crucial to study for understanding the origin of fundamental physical and chemical processes. In this review, we examine the current state and prospects of ultrafast phenomena driven by plasmons both from a fundamental and applied point of view. This research area is referred to as ultrafast plasmonics and represents an outstanding playground to tailor and control fast optical and electronic processes at the nanoscale, such as ultrafast optical switching, single photon emission, and strong coupling interactions to tailor photochemical reactions. Here, we provide an overview of the field and describe the methodologies to monitor and control nanoscale phenomena with plasmons at ultrafast timescales in terms of both modeling and experimental characterization. Various directions are showcased, among others recent advances in ultrafast plasmon-driven chemistry and multi-functional plasmonics, in which charge, spin, and lattice degrees of freedom are exploited to provide active control of the optical and electronic properties of nanoscale materials. As the focus shifts to the development of practical devices, such as all-optical transistors, we also emphasize new materials and applications in ultrafast plasmonics and highlight recent development in the relativistic realm. The latter is a promising research field with potential applications in fusion research or particle and light sources providing properties such as attosecond duration.

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  • 48. Panova, Elena
    et al.
    Volokitin, Valentin
    Efimenko, Evgeny
    Ferri, Julien
    Blackburn, Thomas
    Marklund, Mattias
    Muschet, Alexander
    Umeå University, Faculty of Science and Technology, Department of Physics.
    de Andres Gonzalez, Aitor
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fischer, Peter
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Meyerov, Iosif
    Gonoskov, Arkady
    Optimized Computation of Tight Focusing of Short Pulses Using Mapping to Periodic Space2021In: Applied Sciences, E-ISSN 2076-3417, Vol. 11, no 3, article id 956Article in journal (Refereed)
    Abstract [en]

    When a pulsed, few-cycle electromagnetic wave is focused by optics with f-number smaller than two, the frequency components it contains are focused to different regions of space, building up a complex electromagnetic field structure. Accurate numerical computation of this structure is essential for many applications such as the analysis, diagnostics, and control of high-intensity laser-matter interactions. However, straightforward use of finite-difference methods can impose unacceptably high demands on computational resources, owing to the necessity of resolving far-field and near-field zones at sufficiently high resolution to overcome numerical dispersion effects. Here, we present a procedure for fast computation of tight focusing by mapping a spherically curved far-field region to periodic space, where the field can be advanced by a dispersion-free spectral solver. In many cases of interest, the mapping reduces both run time and memory requirements by a factor of order 10, making it possible to carry out simulations on a desktop machine or a single node of a supercomputer. We provide an open-source C++ implementation with Python bindings and demonstrate its use for a desktop machine, where the routine provides the opportunity to use the resolution sufficient for handling the pulses with spectra spanning over several octaves. The described approach can facilitate the stability analysis of theoretical proposals, the studies based on statistical inferences, as well as the overall development and analysis of experiments with tightly-focused short laser pulses.

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  • 49. Rivas, D. E.
    et al.
    Borot, A.
    Cardenas, D. E.
    Marcus, G.
    Gu, X.
    Herrmann, D.
    Xu, J.
    Tan, J.
    Kormin, D.
    Ma, G.
    Dallari, W.
    Tsakiris, G. D.
    Foldes, I. B.
    Chou, S. -w.
    Weidman, M.
    Bergues, B.
    Wittmann, T.
    Schroeder, H.
    Tzallas, P.
    Charalambidis, D.
    Razskazovskaya, O.
    Pervak, V.
    Krausz, F.
    Veisz, László
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Next Generation Driver for Attosecond and Laser-plasma Physics2017In: Scientific Reports, E-ISSN 2045-2322, Vol. 7, article id 5224Article in journal (Refereed)
    Abstract [en]

    The observation and manipulation of electron dynamics in matter call for attosecond light pulses, routinely available from high-order harmonic generation driven by few-femtosecond lasers. However, the energy limitation of these lasers supports only weak sources and correspondingly linear attosecond studies. Here we report on an optical parametric synthesizer designed for nonlinear attosecond optics and relativistic laser-plasma physics. This synthesizer uniquely combines ultra-relativistic focused intensities of about 10(20)W/cm(2) with a pulse duration of sub-two carrier-wave cycles. The coherent combination of two sequentially amplified and complementary spectral ranges yields sub-5-fs pulses with multi-TW peak power. The application of this source allows the generation of a broad spectral continuum at 100-eV photon energy in gases as well as high-order harmonics in relativistic plasmas. Unprecedented spatio-temporal confinement of light now permits the investigation of electric-field-driven electron phenomena in the relativistic regime and ultimately the rise of next-generation intense isolated attosecond sources.

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  • 50.
    Rivas, Daniel
    et al.
    Max-Planck-Institut fur Quantenoptik, Garching, Germany.
    Major, Balazs
    Department of Optics and Quantum Electronics, University of Szeged, Szeged, Hungary.
    Weidman, Matthew
    Max-Planck-Institut fur Quantenoptik, Garching, Germany.
    Helml, Wofram
    Fakultat fur Physik, Ludwig-Maximilians-Universitat Munchen, Garching, Germany; Physics Department, Technische Universität München, Garching, Germany.
    Marcus, Gilad
    Max-Planck-Institut fur Quantenoptik, Garching, Germany; Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel .
    Kienberger, Reinhard
    Max-Planck-Institut fur Quantenoptik, Garching, Germany; Physics Department, Technische Universität München, Garching, Germany.
    Charalambidis, Dimitris
    ELI-ALPS, ELI-HU Non-Profit Ltd., Szeged, Hungary; FORTH-IESL, Heraklion, Crete, Greece; Department of Physics, University of Crete, Heraklion, Crete, Greece.
    Tzallas, Paris
    ELI-ALPS, ELI-HU Non-Profit Ltd., Hungary; FORTH-IESL, Heraklion, Crete, Greece.
    Balogh, Emeric
    Department of Optics and Quantum Electronics, University of Szeged, Szeged, Hungary.
    Kovacs, Katalin
    National Institute for R&D of Isotopic and Molecular Technologies, Cluj-Napoca, Romania.
    Tosa, Valer
    National Institute for R&D of Isotopic and Molecular Technologies, Cluj-Napoca, Romania.
    Bergues, Boris
    Max-Planck-Institut fur Quantenoptik, Garching, Germany; Fakultät für Physik, Ludwig-Maximilians-Universität München, Garching, Germany.
    Varju, Katalin
    Department of Optics and Quantum Electronics, University of Szeged, Szeged, Hungary; ELI-ALPS, ELI-HU Non-Profit Ltd., Szeged, Hungary.
    Veisz, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Physics. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Propagation-enhanced generation of intense high-harmonic continua in the 100-eV spectral region2018In: Optica, ISSN 2334-2536, Vol. 5, no 10, p. 1283-1289Article in journal (Refereed)
    Abstract [en]

    The study of core electron dynamics through nonlinear spectroscopy requires intense isolated attosecond extremeultraviolet or even X-ray pulses. A robust way to produce these pulses is high-harmonic generation (HHG) in agas medium. However, the energy upscaling of the process depends on a very demanding next-generation laser technologythat provides multi-terawatt (TW) laser pulses with few-optical-cycle duration and controlled electric field.Here, we revisit the HHG process driven by 16-TW sub-two-cycle laser pulses to reach high intensity in the 100-eVspectral region and beyond. We show that the combination of above barrier-suppression intensity with a long generationmedium significantly enhances the isolation of attosecond pulses compared to lower intensities and/or shortermedia and this way reduces the pulse duration as well as field-stability requirements on the laser driver. This novelregime facilitates the real-time observation of electron dynamics at the attosecond timescale in atoms, molecules, andsolids.

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