| 1. |
- Busto, David, et al.
(författare)
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Probing electronic decoherence with high-resolution attosecond photoelectron interferometry
- 2022
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Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 76:7
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: Quantum coherence plays a fundamental role in the study and control of ultrafast dynamics in matter. In the case of photoionization, entanglement of the photoelectron with the ion is a well-known source of decoherence when only one of the particles is measured. Here, we investigate decoherence due to entanglement of the radial and angular degrees of freedom of the photoelectron. We study two-photon ionization via the 2s2p autoionizing state in He using high spectral resolution photoelectron interferometry. Combining experiment and theory, we show that the strong dipole coupling of the 2s2p and 2p2 states results in the entanglement of the angular and radial degrees of freedom. This translates, in angle-integrated measurements, into a dynamic loss of coherence during autoionization. Graphic Abstract: [Figure not available: see fulltext.]. © 2022, The Author(s).
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| 2. |
- Zhong, Jin Hui, et al.
(författare)
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Nonlinear plasmon-exciton coupling enhances sum-frequency generation from a hybrid metal/semiconductor nanostructure
- 2020
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- The integration of metallic plasmonic nanoantennas with quantum emitters can dramatically enhance coherent harmonic generation, often resulting from the coupling of fundamental plasmonic fields to higher-energy, electronic or excitonic transitions of quantum emitters. The ultrafast optical dynamics of such hybrid plasmon–emitter systems have rarely been explored. Here, we study those dynamics by interferometrically probing nonlinear optical emission from individual porous gold nanosponges infiltrated with zinc oxide (ZnO) emitters. Few-femtosecond time-resolved photoelectron emission microscopy reveals multiple long-lived localized plasmonic hot spot modes, at the surface of the randomly disordered nanosponges, that are resonant in a broad spectral range. The locally enhanced plasmonic near-field couples to the ZnO excitons, enhancing sum-frequency generation from individual hot spots and boosting resonant excitonic emission. The quantum pathways of the coupling are uncovered from a two-dimensional spectrum correlating fundamental plasmonic excitations to nonlinearly driven excitonic emissions. Our results offer new opportunities for enhancing and coherently controlling optical nonlinearities by exploiting nonlinear plasmon-quantum emitter coupling.
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| 3. |
- Arnold, Cord L., et al.
(författare)
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A high-repetition rate attosecond pulse source for coincidence spectroscopy
- 2021
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Ingår i: 2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021. - 9781665418768
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Konferensbidrag (refereegranskat)abstract
- The power of attosecond pump-probe spectroscopy combined with advanced detection schemes, such as photoelectron/ion coincidence spectrometers and time-resolved photoelectron emission microscopy (PEEM), can be unleashed by properly accounting for the repetition rate of the source. In this work, we present a high-repetition rate (200 kHz) attosecond pulse source that opens up for exploring phenomena, previously inaccessible to the community using attosecond interferometric and spectroscopy pump-probe techniques [1].
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| 4. |
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| 5. |
- Arnold, Cord L., et al.
(författare)
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Lightning protection by laser
- 2023
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Ingår i: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 17:3, s. 211-212
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Tidskriftsartikel (refereegranskat)
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| 6. |
- Arnold, Cord L., et al.
(författare)
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Spatiotemporal coupling of attosecond pulses
- 2019
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Ingår i: 2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019. - 9781728104690 ; Part F140-CLEO_Europe 2019
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Konferensbidrag (refereegranskat)abstract
- Attosecond pulses in the extreme ultraviolet (XUV) spectral range are today routinely generated via high-order harmonic generation (HHG), when intense ultrashort laser pulses are focused into a gaseous generation medium. The effect is most easily understood in a semi-classical picture [1]. An electron can tunnel ionize from the distorted atomic potential, pick up kinetic energy in the laser field, potentially return to its parent ion and recombine. The excess energy is emitted as XUV photon. The process repeats for every half-cycle of the driving field, resulting in a train of attosecond pulses and in the frequency domain in the well-known, odd-order comb of harmonics. Two main families of electron trajectories leading to the same photon energy can be distinguished into 'short' and 'long', according to their time of travel in the continuum. Due to the complicated nature of the HHG process, attosecond pulses usually cannot be separated into their temporal and spatial profiles, but instead have strong chromatic aberration and are spatio-temporally coupled [2-4].
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| 7. |
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| 8. |
- Balla, Prannay, et al.
(författare)
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Post-compression of picosecond pulses to four optical cycles
- 2020
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Ingår i: High Intensity Lasers and High Field Phenomena, HILAS 2020. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- We report post-compression of 1.2 ps pulses into the few-cycle regime via multi-pass spectral broadening. We achieve compression factors of 40 in single and 93 in a dual stage scheme using a compact setup.
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| 9. |
- Balla, Prannay, et al.
(författare)
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Postcompression of picosecond pulses into the few-cycle regime
- 2020
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Ingår i: Optics Letters. - 0146-9592. ; 45:9, s. 2572-2575
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Tidskriftsartikel (refereegranskat)abstract
- In this work,we demonstrate postcompression of 1.2 ps laser pulses to 13 fs via gas-based multipass spectral broadening. Our results yield a single-stage compression factor of about 40 at 200 W in-burst average power and a total compression factor >90 at reduced power. The employed scheme represents a route toward compact few-cycle sources driven by industrial-grade Yb:YAG lasers at high average power.
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| 10. |
- Bengtsson, Samuel N., et al.
(författare)
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Free induction decay in the extreme ultraviolet
- 2015
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Ingår i: Proceedings of Frontiers in Optics 2015, FIO 2015. - 9781943580033
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Konferensbidrag (refereegranskat)abstract
- We present an experimental study of controlled Free Induction Decay (FID) in the extreme ultraviolet regime excited by High-order Harmonics. The control is done by applying a delayed infrared pulse.
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| 11. |
- Berrocal, Edouard, et al.
(författare)
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Two-photon fluorescence laser sheet imaging for high contrast visualization of atomizing sprays
- 2019
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Ingår i: OSA Continuum. - 2578-7519. ; 2:3, s. 983-993
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Tidskriftsartikel (refereegranskat)abstract
- Two-photon excitation laser induced fluorescence (2p-LIF) is used here for imaging an optically dense atomizing spray. The main advantage of the approach is that very little fluorescence interference originating from multiple light scattering is generated. This leads to high image contrast and a faithful description of the imaged fluid structures. While point measurement 2p-LIF imaging is a well-known approach used in life science microscopy, it has, to the best of the authors' knowledge, never been tested for analyzing liquid structures in spray systems. We take advantage of this process, here, at a macroscopic scale (textblackslashsim 5textblackslashtimes 5$5texttimes5 mm field of view) by imaging the central part of a light sheet of 10 mm height. To generate enough 2p-LIF signal at such a scale and with single-shot detection, ultra-short laser pulses of 25 fs, centered at 800 nm wavelength and having 2.5 mJ pulse energy, have been used. The technique is demonstrated by imaging a single spray plume from a 6 hole commercial Gasoline Direct Injection (GDI) system running at 200 bar injection pressure. The proposed approach is very promising for detailed analysis of liquid breakups in optically dense sprays and can be used for other fluid mechanics related applications.
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| 12. |
- Cheng, Yu Chen, et al.
(författare)
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Controlling photoionization using attosecond time-slit interferences
- 2020
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 117:20, s. 10727-10732
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Tidskriftsartikel (refereegranskat)abstract
- When small quantum systems, atoms or molecules, absorb a high-energy photon, electrons are emitted with a well-defined energy and a highly symmetric angular distribution, ruled by energy quantization and parity conservation. These rules are based on approximations and symmetries which may break down when atoms are exposed to ultrashort and intense optical pulses. This raises the question of their universality for the simplest case of the photoelectric effect. Here we investigate photoionization of helium by a sequence of attosecond pulses in the presence of a weak infrared laser field. We continuously control the energy of the photoelectrons and introduce an asymmetry in their emission direction, at variance with the idealized rules mentioned above. This control, made possible by the extreme temporal confinement of the light-matter interaction, opens a road in attosecond science, namely, the manipulation of ultrafast processes with a tailored sequence of attosecond pulses.
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| 13. |
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| 14. |
- Dacasa, Hugo, et al.
(författare)
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Single-shot extreme-ultraviolet wavefront measurements of high-order harmonics
- 2019
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Ingår i: Optics Express. - 1094-4087. ; 27:3, s. 2656-2670
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Tidskriftsartikel (refereegranskat)abstract
- We perform wavefront measurements of high-order harmonics using an extreme-ultraviolet (XUV) Hartmann sensor and study how their spatial properties vary with different generation parameters, such as pressure in the nonlinear medium, fundamental pulse energy and duration as well as beam size. In some conditions, excellent wavefront quality (up to 휆/11) was obtained. The high throughput of the intense XUV beamline at the Lund Laser Centre allows us to perform single-shot measurements of both the full harmonic beam generated in argon and individual harmonics selected by multilayer mirrors. We theoretically analyze the relationship between the spatial properties of the fundamental and those of the generated high-order harmonics, thus gaining insight into the fundamental mechanisms involved in high-order harmonic generation (HHG).
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| 15. |
- Fischer, Peter, 1988-
(författare)
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A sub-5 fs 100 TW optical parametric synthesizer
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- State-of-the-art ultrashort light sources in the visible and near-infrared spectral regions provide direct access to the femtosecond realm, thereby enabling understanding and control of electronic processes within matter. On the other hand, ultra-intense light pulses lead to the emergence of relativistic electron motion and many related phenomena, such as electron & ion acceleration and high-order harmonic generation in plasmas. The generation and amplification techniques for those intense short light pulses were developed over the last 60 years. Nowadays, they are unique scientific research tools and the basis of commercial applications. The driving forces behind many of these new optical technologies are second and third order nonlinear ultrashort processes. Optical parametric chirped pulse amplification (OPCPA) is currently the most interesting of these techniques and promises in particular high single-pass gain, broad gain bandwidth, scalability, good high-dynamic range temporal contrast, and tunability. However, OPCPA comes also with a bundle of challenges. The aim of this thesis, by utilizing the advantages and facing these challenges, is to boost a sub-two cycle optical parametric synthesizer (OPS), a two-color-pumped OPCPA, to an unprecedented parameter regime in respect of energy, intensity, contrast and stability.The presented sub-2-optical cycle OPS – the light wave synthesizer (LWS) - is a worldwide unique system, amplifying a spectral bandwidth in three pairs of OPCPA stages. One pair of these stages sequentially amplifies and coherently combines two complementary spectral ranges to an almost octave spanning bandwidth. The amplified spectrum ranges from 580 nm to 1000 nm, which makes Fourier limited pulses with 4.6 fs possible. The present system is a fundamental reconstruction and extension of a former version of LWS that provided peak powers of up to 16 TW. By carefully redesigning of the former OPCPA stages, implementing a new front end and adding two nominally 2.3 J Nd:YAG amplifiers, harmonic generation setups and a third pair of OPCPA stages, the pulse energy has been raised up to 450-500 mJ while keeping the spectral bandwidth. After compression, this corresponds to about the aspired 100 TW peak power.Focus was also laid on various important parameters for such ultra-short and ultra-intense light pulses, such as the temporal contrast, the carrier-envelope phase (CEP) and energy stability. Analysis and optimization of the 16 TW LWS version operation parameters made it possible to optimize the LWS-100 root mean square energy stabilities down to 0.3-0.5% over 100 s, which is significantly lower than previously reported for the former version. For the first time, the CEP-stability for this full system has been demonstrated. Currently, it is limited by slow drifts, but an active feedback system could suppress this to 400 mrad. The influences on the temporal contrast were investigated and prepulses identified and eliminated. Furthermore, hardware and software control for easy handling and reliable operation have been implemented.The LWS-100 pushes the limits for few-cycle laser technology even further. It enables the generation of intense and isolated attosecond pulses beyond 100 eV photon energy, acceleration of attosecond electron bunches to relativistic energies, measurement of nonlinear processes of inner shell electrons via XUV pump-probe experiments and generation of isolated attosecond pulses on plasma mirrors.
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| 16. |
- Guo, Chen, et al.
(författare)
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Phase control of attosecond pulses in a train
- 2018
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 51:3
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Tidskriftsartikel (refereegranskat)abstract
- Ultrafast processes in matter can be captured and even controlled by using sequences of few-cycle optical pulses, which need to be well characterized, both in amplitude and phase. The same degree of control has not yet been achieved for few-cycle extreme ultraviolet pulses generated by high-order harmonic generation (HHG) in gases, with duration in the attosecond range. Here, we show that by varying the spectral phase and carrier-envelope phase (CEP) of a high-repetition rate laser, using dispersion in glass, we achieve a high degree of control of the relative phase and CEP between consecutive attosecond pulses. The experimental results are supported by a detailed theoretical analysis based upon the semi-classical three-step model for HHG.
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| 17. |
- Guo, Chen, et al.
(författare)
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Single-shot, high-repetition rate carrier-envelope-phase detection of ultrashort laser pulses
- 2023
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Ingår i: Optics Letters. - 0146-9592. ; 48:20, s. 5431-5434
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Tidskriftsartikel (refereegranskat)abstract
- We propose a single-shot, high-repetition rate measurement scheme of the carrier-envelope phase offset of ultrashort laser pulses. The spectral fringes resulting from f-2f nonlinear interferometry, encoding the carrier-envelope-phase, are evaluated completely optically via an optical Fourier transform. For demonstration, the carrier-envelope-phase of a 200 kHz, few-cycle optical parametric chirped-pulse amplification (OPCPA) laser system was measured employing an interferometer as a periodic optical filter. The proposed method shows excellent agreement with simultaneous measurement of the spectral fringes by a fast line-scan camera.
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| 18. |
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| 19. |
- Harth, Anne, et al.
(författare)
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Compact 200 kHz HHG source driven by a few-cycle OPCPA
- 2018
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Ingår i: Journal of Optics (United Kingdom). - : IOP Publishing. - 2040-8978 .- 2040-8986. ; 20:1
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Tidskriftsartikel (refereegranskat)abstract
- We present efficient high-order harmonic generation (HHG) based on a high-repetition rate, few-cycle, near infrared (NIR), carrier-envelope phase stable, optical parametric chirped pulse amplifier (OPCPA), emitting 6 fs pulses with 9 μJ pulse energy. In krypton, we reach conversion efficiencies from the NIR to the extreme ultraviolet (XUV) radiation pulse energy on the order of ∼10-6 with less than 3 μJ driving pulse energy. This is achieved by optimizing the OPCPA for a spatially and temporally clean pulse and by a specially designed high-pressure gas target. In the future, the high efficiency of the HHG source will be beneficial for high-repetition rate two-colour (NIR-XUV) pump-probe experiments, where the available pulse energy from the laser has to be distributed economically between pump and probe pulses.
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| 20. |
- Jarnac, Amelie, et al.
(författare)
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Compression of TW class laser pulses in a planar hollow waveguide for applications in strong-field physics
- 2014
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Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060. ; 68:12
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate pulse post-compression of a TW class chirped pulse amplification laser employing a gas-filled planar hollow waveguide. A waveguide throughput of 80% is achieved for 50 mJ input pulse energy. Good focusability is found and after compression with chirped mirrors a pulse duration of sub-15 fs is measured in the beam center. Whereas a total energy efficiency of approximate to 70% should be achievable, our post-compressor currently delivers 20 mJ output pulse energy (approximate to 40% efficiency), mostly limited by apertures of chirped mirrors and vacuum windows. The viability of the planar hollow waveguide compression scheme for applications in strong-field physics is demonstrated by generating high-order harmonics in a pulsed Ar gas cell.
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| 21. |
- Jimenez-Galan, A., et al.
(författare)
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Phase Measurement of a Fano Resonance Using Tunable Attosecond Pulses
- 2015
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 635, s. 092137-092137
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Konferensbidrag (refereegranskat)abstract
- We study photoionization of argon atoms close to the 3s(2)3p(6) -> 3s(1)3p(6)4p Fano resonance using an attosecond pulse train and a weak infrared probe field. An interferometric technique combined with tunable attosecond pulses allows us to determine the phase of the photoionization amplitude as a function of photon energy. We interpret the experimental results using an analytical two-photon model based on the Fano formalism and obtain quantitative agreement.
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| 22. |
- Jusko, Christoph, et al.
(författare)
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Spatio-temporal characterization of a femtosecond filament along its length
- 2020
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Ingår i: High Intensity Lasers and High Field Phenomena, HILAS 2020. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- We present an experimental method capable of characterizing spatio-temporal dynamics of a femtosecond filament v ia F ourier t ransform i nterferometry, p roviding a three-dimensional reconstruction of the driving pulse, while scanning along the entire length of the filament.
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| 23. |
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| 24. |
- Kotur, Marija, et al.
(författare)
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Spectral phase measurement of a Fano resonance using tunable attosecond pulses
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Electron dynamics induced by resonant absorption of light is of fundamental importance in nature and has been the subject of countless studies in many scientific areas. Above the ionization threshold of atomic or molecular systems, the presence of discrete states leads to autoionization, which is an interference between two quantum paths: direct ionization and excitation of the discrete state coupled to the continuum. Traditionally studied with synchrotron radiation, the probability for autoionization exhibits a universal Fano intensity profile as a function of excitation energy. However, without additional phase information, the full temporal dynamics cannot be recovered. Here we use tunable attosecond pulses combined with weak infrared radiation in an interferometric setup to measure not only the intensity but also the phase variation of the photoionization amplitude across an autoionization resonance in argon. The phase variation can be used as a fingerprint of the interactions between the discrete state and the ionization continua, indicating a new route towards monitoring electron correlations in time.
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| 25. |
- Kühn, Sergei, et al.
(författare)
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The ELI-ALPS facility : The next generation of attosecond sources
- 2017
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 50:13
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Forskningsöversikt (refereegranskat)abstract
- This review presents the technological infrastructure that will be available at the Extreme Light Infrastructure Attosecond Light Pulse Source (ELI-ALPS) international facility. ELI-ALPS will offer to the international scientific community ultrashort pulses in the femtosecond and attosecond domain for time-resolved investigations with unprecedented levels of high quality characteristics. The laser sources and the attosecond beamlines available at the facility will make attosecond technology accessible for scientists lacking access to these novel tools. Time-resolved investigation of systems of increasing complexity is envisaged using the end stations that will be provided at the facility.
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