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  • 1. Aladi, M.
    et al.
    Bolla, R.
    Cardenas, D. E.
    Veisz, László
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foldes, I. B.
    Cluster size distributions in gas jets for different nozzle geometries2017Ingår i: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 12, artikel-id C06020Artikel i tidskrift (Refereegranskat)
    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 practice2014Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 22, nr 24, s. 30387-30393Artikel i tidskrift (Refereegranskat)
    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 universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. 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 universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Tabletop nonlinear optics in the 100-eV spectral region2018Ingår i: Optica, ISSN 2334-2536, Vol. 5, nr 3, s. 237-242Artikel i tidskrift (Refereegranskat)
    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 universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, 85748, Garching, Germany.
    Helml, W.
    Guggenmos, A.
    Pervak, V.
    Matyba, Piotr
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Kleineberg, U.
    Marcus, G.
    Kienberger, R.
    Charalambidis, D.
    Tzallas, P.
    Schröder, H.
    Krausz, F.
    Veisz, Laszlo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Towards Attosecond XUV-Pump XUV-Probe Measurements in the 100-eV Region2017Ingår i: 2017 Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), IEEE, 2017Konferensbidrag (Refereegranskat)
  • 5. 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 Acceleration2013Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 110, nr 18, artikel-id 185006Artikel i tidskrift (Refereegranskat)
    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.

  • 6. Cardenas, D. E.
    et al.
    Ostermayr, T. M.
    Di Lucchio, L.
    Hofmann, L.
    Kling, M. F.
    Gibbon, P.
    Schreiber, J.
    Veisz, Laszlo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Sub-cycle dynamics in relativistic nanoplasma acceleration2019Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, artikel-id 7321Artikel i tidskrift (Refereegranskat)
    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.

  • 7. Chou, Shao-wei
    et al.
    Xu, J.
    Khrennikov, K.
    Cardenas, Daniel E.
    Wenz, J.
    Heigoldt, M.
    Hofmann, L.
    Veisz, Laszlo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck Institut für Quantenoptik, 85748 Garching, Germany.
    Karsch, S.
    Collective Deceleration of Laser-Driven Electron Bunches2016Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 117, nr 14, artikel-id 144801Artikel i tidskrift (Refereegranskat)
    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.

  • 8. Dombi, Peter
    et al.
    Rácz, Peter
    Veisz, László
    Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Baum, Peter
    Conversion of chirp in fiber compression2014Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 39, nr 8, s. 2232-2235Artikel i tidskrift (Refereegranskat)
    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.

  • 9. 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 Accelerator2015Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 115, nr 15, artikel-id 155002Artikel i tidskrift (Refereegranskat)
    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%.

  • 10. 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 plasma2015Ingår i: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 118, nr 2, s. 195-201Artikel i tidskrift (Refereegranskat)
    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.

  • 11. 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 universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Pervak, Vladimir
    Krausz, Ferenc
    Major, Zsuzsanna
    Karsch, Stefan
    Towards intense isolated attosecond pulses from relativistic surface high harmonics2019Ingår i: Optica, ISSN 2334-2536, Vol. 6, nr 3, s. 280-287Artikel i tidskrift (Refereegranskat)
    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

  • 12. 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 Regime2015Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 114, nr 19, artikel-id 195003Artikel i tidskrift (Refereegranskat)
    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.

  • 13. 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 physics2014Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 90, nr 1, artikel-id 013822Artikel i tidskrift (Refereegranskat)
    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.

  • 14. 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 radiation2014Ingår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 31, nr 5, s. 926-938Artikel i tidskrift (Refereegranskat)
    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.

  • 15. Kormin, Dmitrii
    et al.
    Borot, Antonin
    Ma, Guangjin
    Dallari, William
    Bergues, Boris
    Aladi, Mark
    Földes, Istvan B.
    Veisz, Laszlo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany.
    Spectral interferometry with waveform-dependent relativistic high-order harmonics from plasma surfaces2018Ingår i: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 9, artikel-id 4992Artikel i tidskrift (Refereegranskat)
    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.

  • 16. Leshchenko, Vyacheslav E.
    et al.
    Kessel, Alexander
    Jahn, Olga
    Krüger, Mathias
    Münzer, Andreas
    Trushin, Sergei A.
    Veisz, Laszlo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
    Major, Zsuzsanna
    Karsch, Stefan
    On-target temporal characterization of optical pulses at relativistic intensity2019Ingår i: Light: Science & Applications, ISSN 2095-5545, E-ISSN 2047-7538, Vol. 8, artikel-id 96Artikel i tidskrift (Refereegranskat)
    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.

  • 17. Leshchenko, Vyacheslav E.
    et al.
    Kessel, Alexander
    Jahn, Olga
    Krüger, Mathias
    Münzer, Andreas
    Trushin, Sergei A.
    Veisz, Laszlo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany.
    Major, Zsuzsanna
    Karsch, Stefan
    On-target temporal characterization of optical pulses at relativistic intensity2019Ingår i: Light: Science & Applications, ISSN 2095-5545, E-ISSN 2047-7538, Vol. 8, artikel-id 96Artikel i tidskrift (Refereegranskat)
    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.

  • 18. 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 Fibers2015Ingår i: Journal of Lasers, Optics & Photonics, ISSN 2469-410X, Vol. 2, nr 3, artikel-id 1000124Artikel i tidskrift (Refereegranskat)
    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.

  • 19. 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 pulses2015Ingår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 22, nr 3, artikel-id 033105Artikel i tidskrift (Refereegranskat)
    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.

  • 20. Ma, Guangjin
    et al.
    Yu, Wei
    Yu, M. Y.
    Shen, Baifei
    Veisz, Laszlo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany.
    Intense circularly polarized attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses2016Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 24, nr 9, s. 10057-10065Artikel i tidskrift (Refereegranskat)
    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.

  • 21. 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 universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. 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 geometry2017Ingår i: 2017 Conference on Lasers and Electro-Optics Europe &  European Quantum Electronics Conference (CLEO/Europe-EQEC), IEEE, 2017Konferensbidrag (Refereegranskat)
    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.

  • 22. 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 universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Next Generation Driver for Attosecond and Laser-plasma Physics2017Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, artikel-id 5224Artikel i tidskrift (Refereegranskat)
    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.

  • 23.
    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 universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Propagation-enhanced generation of intense high-harmonic continua in the 100-eV spectral region2018Ingår i: Optica, ISSN 2334-2536, Vol. 5, nr 10, s. 1283-1289Artikel i tidskrift (Refereegranskat)
    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.

  • 24. Schwab, M. B.
    et al.
    Sävert, A.
    Jäckel, O.
    Polz, J.
    Schnell, M.
    Rinck, T.
    Veisz, László
    Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Möller, M.
    Hansinger, P.
    Paulus, G. G.
    Kaluza, M. C.
    Few-cycle optical probe-pulse for investigation of relativistic laser-plasma interactions2013Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, nr 19, artikel-id 191118Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The development of a few-cycle optical probe-pulse for the investigation of laser-plasma interactions driven by a Ti:sapphire, 30 Terawatt (TW) laser system is described. The probe is seeded by a fraction of the driving laser's energy and is spectrally broadened via self-phase modulation in a hollow core fiber filled with a rare gas, then temporally compressed to a few optical cycles via chirped mirrors. Shadowgrams of the laser-driven plasma wave created in relativistic electron acceleration experiments are presented with few-fs temporal resolution, which is shown to be independent of post-interaction spectral filtering of the probe-beam.

  • 25.
    Smijesh, N.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zhang, X.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Fischer, Peter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Muschet, Alexander
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Salh, Roushdey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Tajalli, A.
    Morgner, U.
    Veisz, Laszlo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Contrast improvement of sub-4 fs laser pulses using nonlinear elliptical polarization rotation2019Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 44, nr 16, s. 4028-4031Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Temporal-intensity contrast is crucial in intense laser-matter interaction to circumvent the undesirable expansion of steep high-density plasma prior to the interaction with the main pulse. Nonlinear elliptical polarization rotation in an argon filled hollow-core fiber is used here for cleaning pedestals/satellite pulses of a chirped-pulse-amplifier based Ti: Sapphire laser. This source provides similar to 35 mu J energy and sub-4-fs duration, and the process has >50% internal efficiency, more than the most commonly used pulse cleaning methods. Further, the contrast is improved by 3 orders of magnitude when measured after amplifying the pulses to 16 TW using non-collinear optical parametric chirped pulse amplification with a prospect to even further enhancement.

  • 26.
    Tan, Jeryl
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Forget, Nicolas
    Borot, Antonin
    Kaplan, Daniel
    Tournois, Pierre
    Muschet, Alexander
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Veisz, Laszlo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Dispersion control for temporal contrast optimization2018Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 26, nr 19, s. 25003-25012Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate the temporal contrast of the Light Wave Synthesizer 20 (LWS-20): a powerful, few-cycle source based on the optical parametric synthesizer principle. Saturation effects in the RF amplifier driving the acousto-optic programmable dispersive filter (AOPDF) were found to degrade the coherent contrast for non-monotonic group delay corrections. We subsequently present a new dispersion scheme and design a novel transmission grism-based stretcher optimized for LWS-20. The resulting temporal contrast of the amplified, compressed output pulses is improved by 2-4 orders of magnitude compared to the former design.

  • 27. Teichmann, S. M.
    et al.
    Racz, P.
    Ciappina, M. F.
    Perez-Hernandez, J. A.
    Thai, A.
    Fekete, J.
    Elezzabi, A. Y.
    Veisz, László
    Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany.
    Biegert, J.
    Dombi, P.
    Strong-field plasmonic photoemission inthe mid-IR at <1 GW/cm2 intensity2015Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, artikel-id 7584Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigated nonlinear photoemission from plasmonic films with femtosecond, mid-infrared pulses at 3.1 μm wavelength. Transition between regimes of multi-photon-induced and tunneling emission is demonstrated at an unprecedentedly low intensity of <1 GW/cm2. Thereby, strong-field nanophysics can be accessed at extremely low intensities by exploiting nanoscale plasmonic field confinement, enhancement and ponderomotive wavelength scaling at the same time. Results agree well with quantum mechanical modelling. Our scheme demonstrates an alternative paradigm and regime in strong-field physics.

  • 28. Tsatrafyllis, N.
    et al.
    Bergues, B.
    Schroeder, H.
    Veisz, Laszlo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut fur Quantenoptik, D-85748 Garching, Germany .
    Skantzakis, E.
    Gray, D.
    Bodi, B.
    Kuhn, S.
    Tsakiris, G. D.
    Charalambidis, D.
    Tzallas, P.
    The ion microscope as a tool for imaging the ion distribution produced by linear and non-linear processes at the focus of an XUV beam2017Ingår i: 2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), IEEE, 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Summary form only given. We demonstrate a tool for quantitative measurements in the linear and non-linear extreme ultraviolet (XUV) spectral region measuring spatially resolved atomic ionization products at the focus of an XUV beam [1, 2]. The ionizing radiation is a comb of the 11th-15th harmonics of a Ti:Sapphire femtosecond laser beam produced in a Xenon gas jet. The spatial ion distribution at the focus of the harmonics is recorded using an ion microscope detector [2, 3]. Spatially resolved single- and two-photon ionization products of Argon and Helium are observed. From such ion distributions single- and two-photon generalized cross sections have be extracted by a self-calibrating method. This is the first observation of spatially resolved two-XUV-photon ionization at the focus of the XUV radiation which constitutes an important step towards future single-shot temporal characterization of attosecond (asec) pulses [4].

  • 29. Tsatrafyllis, N.
    et al.
    Bergues, B.
    Schroeder, H.
    Veisz, László
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Skantzakis, E.
    Gray, D.
    Bodi, B.
    Kuhn, S.
    Tsakiris, G. D.
    Charalambidis, D.
    Tzallas, P.
    The ion microscope as a tool for quantitative measurements in the extreme ultraviolet2016Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, artikel-id 21556Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate a tool for quantitative measurements in the extreme ultraviolet (EUV) spectral region measuring spatially resolved atomic ionization products at the focus of an EUV beam. The ionizing radiation is a comb of the 11th-15th harmonics of a Ti:Sapphire femtosecond laser beam produced in a Xenon gas jet. The spatial ion distribution at the focus of the harmonics is recorded using an ion microscope. Spatially resolved single-and two-photon ionization products of Argon and Helium are observed. From such ion distributions single-and two-photon generalized cross sections can be extracted by a self-calibrating method. The observation of spatially resolved two-EUV-photon ionization constitutes an initial step towards future single-shot temporal characterization of attosecond pulses.

  • 30. Tzallas, P.
    et al.
    Bergues, B.
    Rompotis, D.
    Tsatrafyllis, N.
    Chatziathanassiou, S.
    Muschet, Alexander
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Veisz, László
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Schröeder, H.
    Charalambidis, D.
    Time gated ion microscopy of light-atom interactions2018Ingår i: Journal of Optics, ISSN 2040-8978, E-ISSN 2040-8986, Vol. 20, nr 2, artikel-id 024018Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The development of ultra-short intense laser sources in the visible and extreme ultraviolet (XUV) spectral range has led to fascinating studies in laser-matter interactions and attosecond science. In the majority of these studies, the system under investigation interacts with a focused light beam, which ionizes the system. The ionization products are usually measured by devices, which spatiotemporally integrate the ionization signal originating from the entire focal area, discarding in this way valuable information about the ionization dynamics that take place in the interaction volume. Here, we review a recently developed approach in measuring the spatially resolved photoionization yields resulting from the interaction of infrared (IR)/XUV ultra-short light pulses in gas phase media. We show how this approach enables (a) the in situ focus diagnostic, (b) quantitative studies of linear and non-linear ionization processes in the IR/XUV regime, (c) single-shot XUV-pump-XUV-probe studies and (d) single-shot 2nd-order XUV autocorrelation measurements.

  • 31. Wenz, J.
    et al.
    Döpp, A.
    Khrennikov, K.
    Schindler, S.
    Gilljohann, M. F.
    Ding, H.
    Götzfried, J.
    Buck, A.
    Xu, J.
    Heigoldt, M.
    Helml, W.
    Veisz, Laszlo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Max-Planck-Institut für Quantenoptik, Garching, Germany.
    Karsch, S.
    Dual-energy electron beams from a compact laser-driven accelerator2019Ingår i: Nature Photonics, ISSN 1749-4885, E-ISSN 1749-4893, Vol. 13, s. 263-269Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ultrafast pump–probe experiments open the possibility to track fundamental material behaviour, such as changes in electronic configuration, in real time. To date, most of these experiments are performed using an electron or a high-energy photon beam that is synchronized to an infrared laser pulse. Entirely new opportunities can be explored if not only a single, but multiple synchronized, ultrashort, high-energy beams are used. However, this requires advanced radiation sources that are capable of producing dual-energy electron beams, for example. Here, we demonstrate simultaneous generation of twin-electron beams from a single compact laser wakefield accelerator. The energy of each beam can be individually adjusted over a wide range and our analysis shows that the bunch lengths and their delay inherently amount to femtoseconds. Our proof-of-concept results demonstrate an elegant way to perform multi-beam experiments in the future on a laboratory scale.

  • 32. Xu, J.
    et al.
    Buck, A.
    Chou, S. -W
    Schmid, K.
    Shen, B.
    Tajima, T.
    Kaluza, M. C.
    Veisz, László
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Dynamics of electron injection in a laser-wakefield accelerator2017Ingår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 24, nr 8, artikel-id 083106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The detailed temporal evolution of the laser-wakefield acceleration process with controlled injection, producing reproducible high-quality electron bunches, has been investigated. The localized injection of electrons into the wakefield has been realized in a simple way-called shock-front injection-utilizing a sharp drop in plasma density. Both experimental and numerical results reveal the electron injection and acceleration process as well as the electron bunch's temporal properties. The possibility to visualize the plasma wave gives invaluable spatially resolved information about the local background electron density, which in turn allows for an efficient suppression of electron self-injection before the controlled process of injection at the sharp density jump. Upper limits for the electron bunch duration of 6.6 fs FWHM, or 2.8 fs (r. m. s.) were found. These results indicate that shock-front injection not only provides stable and tunable, but also few-femtosecond short electron pulses for applications such as ultrashort radiation sources, time-resolved electron diffraction or for the seeding of further acceleration stages. Published by AIP Publishing.

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