| 1. |
- Aladi, M., et al.
(författare)
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Cluster size distributions in gas jets for different nozzle geometries
- 2017
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Ingår i: Journal of Instrumentation. - : Institute of Physics Publishing (IOPP). - 1748-0221. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Amotchkina, Tatiana, et al.
(författare)
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Stress compensation with antireflection coatings for ultrafast laser applications : from theory to practice
- 2014
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Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 22:24, s. 30387-30393
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Bergues, B., et al.
(författare)
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Nonlinear interaction of 100-eV attosecond XUV-pulses with core electrons in Xenon
- 2018
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Ingår i: Optics InfoBase Conference Papers. - : Optica Publishing Group. - 9781557528209
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 4. |
- Bergues, B., et al.
(författare)
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Tabletop nonlinear optics in the 100-eV spectral region
- 2018
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Ingår i: Optica. - : Optical Society of America. - 2334-2536. ; 5:3, s. 237-242
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
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| 6. |
- Björklund Svensson, Jonas, et al.
(författare)
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Low-divergence femtosecond X-ray pulses from a passive plasma lens
- 2021
-
Ingår i: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2481 .- 1745-2473. ; 17:5, s. 639-645
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Tidskriftsartikel (refereegranskat)abstract
- 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. X-ray pulses with low divergences are produced in a laser-wakefield accelerator by focusing electron bunches in a dense passive plasma lens.
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| 7. |
- Buck, A., et al.
(författare)
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Shock-Front Injector for High-Quality Laser-Plasma Acceleration
- 2013
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 110:18
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Tidskriftsartikel (refereegranskat)abstract
- 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.
(författare)
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Sub-cycle dynamics in relativistic nanoplasma acceleration
- 2019
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- 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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| 9. |
- Cardenas, Daniel, et al.
(författare)
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Electron bunch evolution in laser-wakefield acceleration
- 2020
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Ingår i: Physical Review Accelerators and Beams. - : American Physical Society. - 2469-9888. ; 23
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
(författare)
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Collective Deceleration of Laser-Driven Electron Bunches
- 2016
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 117:14
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 11. |
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| 12. |
- de Andres Gonzalez, Aitor, 1992-
(författare)
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Enhancement of few-cycle light fields for relativistic nanophotonics
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Pulses of light that are both ultrashort and ultraintense are often generated using optical parametric amplifiers (OPA). These are capable of driving highly non-linear interactions with matter, which are interesting when studying the fundamental laws of our universe. Furthermore, they are also used in many scientific and industrial applications, such as particle accelerators, inertial-confinement nuclear fusion, and medical diagnostics and treatment. This thesis explores the diagnostic and optimization of pulses of light with extreme properties and utilizes them to drive electron acceleration.The applied light pulses with very short duration (<5 fs) and high peak power (>10 TW) are sensitive to develop spatio-temporal aberrations. These are color-dependent distortions that can significantly degrade the pulse properties, like peak-intensity, and affect their applicability. Furthermore, in most cases they are not easy to correctly diagnose, with current tools failing to provide widely applicable solutions. In this thesis, we describe a new type of spatio-temporal coupling that is especially relevant for optical parametric synthesizers (OPS), systems that coherently combine multiple OPA stages. To do this, we have contributed to the development of two methods for the characterization of such aberrations, the so-called simplified-INSIGHT and HASO multispectral. These enabled us to further improve the structure of our OPS and laser systems.We also explored the applicability of light pulses to drive relativistic electron acceleration in vacuum. To this end, an injection system using nanotips is presented, capable of inserting electrons spatially in the focus and temporally in the most intense light-cycle. This way, vacuum laser accelerated electrons of up to 14 MeV were detected using a tight focusing configuration (f#1) and their properties characterized. Furthermore, we investigated the dependence of the acceleration process when the focusing geometry is relaxed (f#3). This resulted in the unexpected outcome of similar electron energies in both cases, although the intensity was ten times reduced. This indicates that the decrease in accelerating field strength is compensated by longer acceleration lengths, which is not predicted by currently existing analytical models.
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| 13. |
- de Andres Gonzalez, Aitor, et al.
(författare)
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Simple measurement technique for spatio-temporal couplings in few-cycle pulses
- 2022
-
Ingår i: The International Conference on Ultrafast Phenomena (UP) 2022. - : Optica Publishing Group (formerly OSA). - 9781557528209
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 14. |
- de Andres Gonzalez, Aitor, et al.
(författare)
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Spatio-spectral couplings in optical parametric amplifiers
- 2023
-
Ingår i: Optics Express. - : Optica Publishing Group. - 1094-4087. ; 31:8, s. 12036-12048
-
Tidskriftsartikel (refereegranskat)abstract
- 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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| 15. |
- de Andres Gonzalez, Aitor, 1992-, et al.
(författare)
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Unforeseen advantage of looser focusing in vacuum laser acceleration
- 2024
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- Acceleration of electrons in vacuum directly by intense laser fields holds great promise for the generation of high-charge, ultrashort, relativistic electron bunches. While the energy gain is expected to be higher with tighter focusing, this does not account for the reduced acceleration range, which is limited by diffraction. Here, we present the results of an experimental investigation that exposed nanotips to relativistic few-cycle laser pulses. We demonstrate the vacuum laser acceleration of electron beams with 100s pC charge and 15 MeV energy. Two different focusing geometries, with normalized vector potential a0 of 9.8 and 3.8, produced comparable overall charge and electron spectra, despite a factor of almost ten difference in peak intensity. Our results are in good agreement with 3D particle-in-cell simulations, which indicate the importance of dephasing.
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| 16. |
- de Andres Gonzalez, Aitor, 1992-, et al.
(författare)
-
Vacuum laser acceleration of electrons injected from nanotips
- 2023
-
Ingår i: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023. - : Institute of Electrical and Electronics Engineers (IEEE). - 9798350345995 - 9798350346008
-
Konferensbidrag (refereegranskat)abstract
- 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].
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| 17. |
- Dombi, Peter, et al.
(författare)
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Conversion of chirp in fiber compression
- 2014
-
Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 39:8, s. 2232-2235
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 18. |
- Fischer, Peter, 1988-
(författare)
-
A sub-5 fs 100 TW optical parametric synthesizer
- 2022
-
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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| 19. |
- Fischer, Peter, et al.
(författare)
-
In situ characterization of phase-matching conditions in non-collinear OPA / OPCPA
- 2022
-
Ingår i: Optica High-brightness Sources and Light-driven Interactions Congress 2022. - : Optica Publishing Group. - 9781957171067
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 20. |
- Fischer, Peter, et al.
(författare)
-
Optimization of Optical Parametric Chirped-pulse Amplification
- 2021
-
Ingår i: 2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021. - : IEEE Lasers and Electro-Optics Society. - 9781665418768
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 21. |
- Fischer, Peter, et al.
(författare)
-
Saturation control of an optical parametric chirped-pulse amplifier
- 2021
-
Ingår i: Optics Express. - 1094-4087. ; 29, s. 4210-4218
-
Tidskriftsartikel (refereegranskat)abstract
- 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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| 22. |
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| 23. |
- Fischer, Peter, et al.
(författare)
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Towards a 100 TW, sub-5-fs Optical Parametric Synthesizer
- 2020
-
Ingår i: <em>OSA High-brightness Sources and Light-driven Interactions Congress 2020 (EUVXRAY, HILAS, MICS)</em>. - : Optical Society of America. - 9781943580736
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 24. |
- Guillaume, E., et al.
(författare)
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Electron Rephasing in a Laser-Wakefield Accelerator
- 2015
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 115:15
-
Tidskriftsartikel (refereegranskat)abstract
- 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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| 25. |
- Götzfried, J., et al.
(författare)
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Physics of High-Charge Electron Beams in Laser-Plasma Wakefields
- 2020
-
Ingår i: Physical Review X. - : American Physical Society. - 2160-3308. ; 10:4
-
Tidskriftsartikel (refereegranskat)abstract
- 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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| 26. |
- Heissler, P., et al.
(författare)
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Multi‑μJ harmonic emission energy from laser‑driven plasma
- 2015
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Ingår i: Applied physics. B, Lasers and optics (Print). - : Springer. - 0946-2171 .- 1432-0649. ; 118:2, s. 195-201
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 27. |
- Horny, Vojtech, 1989, et al.
(författare)
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Generation of single attosecond relativistic electron bunch from intense laser interaction with a nanosphere
- 2021
-
Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 1361-6587 .- 0741-3335. ; 63:12
-
Tidskriftsartikel (refereegranskat)abstract
- 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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| 28. |
- Jahn, Olga, et al.
(författare)
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Towards intense isolated attosecond pulses from relativistic surface high harmonics
- 2019
-
Ingår i: Optica. - : Optical Society of America. - 2334-2536. ; 6:3, s. 280-287
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 29. |
- Khrennikov, K., et al.
(författare)
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Tunable All-Optical Quasimonochromatic Thomson X-Ray Sourcein the Nonlinear Regime
- 2015
-
Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 114:19
-
Tidskriftsartikel (refereegranskat)abstract
- 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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| 30. |
- Kolliopoulos, G., et al.
(författare)
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Revealing quantum path details in high-field physics
- 2014
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 90:1
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 31. |
- Kolliopoulos, G., et al.
(författare)
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Single-shot autocorrelator for extreme-ultraviolet radiation
- 2014
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 31:5, s. 926-938
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 32. |
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| 33. |
- Kormin, Dmitrii, et al.
(författare)
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Spectral interferometry with waveform-dependent relativistic high-order harmonics from plasma surfaces
- 2018
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- 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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| 34. |
- Leshchenko, Vyacheslav E., et al.
(författare)
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On-target temporal characterization of optical pulses at relativistic intensity
- 2019
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Ingår i: Light. - : Nature Publishing Group. - 2095-5545 .- 2047-7538. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- 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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| 35. |
- Leshchenko, V.E., et al.
(författare)
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Relativistic harmonics D-scan for on-target temporal characterization of intense optical pulses
- 2019
-
Ingår i: Ultrafast Optics 2019. - : SPIE. - 9781510635128 ; , s. 209-212
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 36. |
- Liu, Qingcao, et al.
(författare)
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Ionization-Induced Subcycle Metallization of Nanoparticles in Few-Cycle Pulses
- 2020
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Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 7:11, s. 3207-3215
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 37. |
- Lotscher, Lauryna, et al.
(författare)
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Long-term Stability of Nonlinear Pulse Compression using Solid-core Large-mode-area Fibers
- 2015
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Ingår i: Journal of Lasers, Optics & Photonics. - : OMICS International. - 2469-410X. ; 2:3
-
Tidskriftsartikel (refereegranskat)abstract
- 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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| 38. |
- Ma, Guangjin, et al.
(författare)
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Intense circularly polarized attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses
- 2016
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Ingår i: Optics Express. - 1094-4087. ; 24:9, s. 10057-10065
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 39. |
- Ma, Guangjin, et al.
(författare)
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Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses
- 2015
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Ingår i: Physics of Plasmas. - : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 22:3
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 40. |
- Ma, Guangjin, et al.
(författare)
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Isolated attosecond light pulse generation from plasma surfaces at varying laser intensities and incidence angles
- 2022
-
Ingår i: 1st International Conference on UltrafastX 2021. - : SPIE - International Society for Optical Engineering.
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 41. |
- Ma, Guangjin, et al.
(författare)
-
Laser intensity and incidence angle dependent attosecond light pulse generation from relativistic laser plasma surfaces
- 2022
-
Ingår i: Sixth international symposium on laser interaction with matter (LIMIS 2022). - : SPIE - International Society for Optical Engineering.
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 42. |
- Ma, Guangjin, et al.
(författare)
-
Relativistic high-order harmonic generation from laser plasmas using few-cycle laser pulses
- 2018
-
Ingår i: Optics InfoBase Conference Papers. - : Optica Publishing Group. - 9781943580453
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 43. |
- Ma, Guangjin, et al.
(författare)
-
Waveform-dependent relativistic high-order harmonics and field-driven plasma surface dynamics
- 2019
-
Ingår i: Ultrafast Optics 2019. - : SPIE. - 9781510635128 ; , s. 106-110
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 44. |
- Major, B., et al.
(författare)
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Investigation of high harmonic generation using a high-power, 5-fs laser in a loose-focusing geometry
- 2017
-
Ingår i: 2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC). - : IEEE. - 9781509067367
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 45. |
- Muschet, Alexander A., 1990-, et al.
(författare)
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An easy technique for focus characterization and optimization of XUV and soft X-ray pulses
- 2022
-
Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 12:11
-
Tidskriftsartikel (refereegranskat)abstract
- 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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| 46. |
- Muschet, Alexander A., 1990-, et al.
(författare)
-
Utilizing the temporal superresolution approach in an optical parametric synthesizer to generate multi-TW sub-4-fs light pulses
- 2022
-
Ingår i: Optics Express. - : The Optical Society. - 1094-4087. ; 30:3, s. 4374-4380
-
Tidskriftsartikel (refereegranskat)abstract
- 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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| 47. |
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| 48. |
- Muschet, Alexander, 1990-
(författare)
-
Non-linear attosecond physics at 100 eV
- 2021
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Non-linear interactions between light and matter have nowadays a broad range of applications. They are used for frequency doubling in simple laser pointers as well as for a variety of purposes in complex laser systems like the one presented in this thesis. For the study of ultrafast phenomena, those non-linear interactions are crucial to trigger and observe events at the fastest timescale, which is currently the attosecond regime (10-15 – 10-18 s). As the duration of a single optical cycle of a visible light wave is longer than this timescale, these investigations necessitate the application of XUV and X-ray pulses. However, the generation of isolated attosecond light pulses sufficiently intense to initiate non-linear interactions with matter is restricted to photon energies below 50 eV. The aim of this thesis is to establish a new light source, which pushes this boundary further and thereby enables the observation of up to now unrevealed electron dynamics.The presented new light source provides attosecond pulses with approximately hundred times more pulse energy than typical systems (up to 55 nJ in the spectral range from approximately 65 eV to 140 eV). This facilitates non-linear measurements at these photon energies. The achieved high energy stability (5 %) of this light source allows precise and time efficient measurements. These parameters are obtained via energy-upscaling of high-harmonic generation in gas medium. For the generation of well isolated attosecond pulses a unique laser, like the Light Wave Synthesizer 20, is necessary. This laser uses optical parametric synthesis to produce the most intense sub-5 fs, sub two-cycle laser pulses in the world (80 mJ, 4.5 fs).Furthermore, an optimal focus of the XUV pulses is crucial to provide the necessary intensity for non-linear interactions. Therefore, different methods for focusing the XUV pulses are investigated. Moreover, the construction and characterization of a robust split and delay stage is presented, which is essential for time resolved measurements.The detection of the non-linear interaction is realized via a spatially resolved ion time-of-flight detector, the ion microscope. This allows for a quantitative measurement of different ionization states. With the combination of this detector and the new light source the non-linear generation of Xe4+ and Xe5+ at photon energies around 100 eV is demonstrated. This enables the determination of the two-photon ionization cross-sections, which could up to now only be measured with much longer pulses at large scientific infrastructures. This paves the way towards time-resolved XUV pump – XUV probe measurements at 100 eV.
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| 49. |
- Nagy, Tamas, et al.
(författare)
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High-energy few-cycle pulses: post-compression techniques
- 2021
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Ingår i: Advances in Physics: X. - : Taylor & Francis. - 2374-6149. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- 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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| 50. |
- Nana Koya, Alemayehu, et al.
(författare)
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Advances in ultrafast plasmonics
- 2023
-
Ingår i: Applied Physics Reviews. - : American Institute of Physics (AIP). - 1931-9401. ; 10:2
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Forskningsöversikt (refereegranskat)abstract
- 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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