Articles de revues : « Lasers attoseconde »

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Dobosz Dufrenoy, Sandrine, Thierry Ruchon, Henri Vincenti, David Bresteau, Pascal Monot, Hugo Marroux, Romain Geneaux, Karol Hricovini et Pascal Salieres. « De l’ultra-rapide à l’ultra-intense : de nouveaux champs d’études ». Photoniques, n^o 118 (2023) : 40–45. http://dx.doi.org/10.1051/photon/202311840.

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Le développement spectaculaire des lasers de puissance ces trente dernières années a ouvert de nouveaux champs d’études : la science attoseconde d’une part, l’optique relativiste d’autre part. Nous illustrons les nouvelles perspectives ouvertes dans divers domaines de la physique, la chimie, la médecine ou la science des matériaux à partir d’études effectuées sur les plateformes ATTOLab et UHI100 du Laboratoire Interactions, Dynamiques et Lasers (LIDYL) du CEA Paris-Saclay.

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Xiao, Yaozong, Chao Feng et Bo Liu. « Generating Isolated Attosecond X-Ray Pulses by Wavefront Control in a Seeded Free-Electron Laser ». Ultrafast Science 2022 (30 juillet 2022) : 1–8. http://dx.doi.org/10.34133/2022/9812478.

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We proposed a simple method based on the seeded free-electron laser (FEL) to generate fully coherent X-ray pulses with durations at dozens of attosecond level. The echo-enabled harmonic generation technique is utilized to generate the fully coherent laser pulse covering the water-window range. A wavefront rotation laser is adopted as the seed to tailor the longitudinal contour of the radiation pulse. Due to the sensitivity of seeded FEL to external lasers, this method can effectively inhibit the bunching of the adjacent regions while preserving an isolated bunching in the middle. Sending such an electron beam into a short undulator, simulation results show that ultrashort X-ray pulses with peak power of GW level and pulse duration as short as 86 attoseconds can be generated. The proposed scheme can make it possible to study the electronic dynamic of the valence electrons of which the time scale is about 100 attoseconds and may open up a new frontier of ultrafast science.

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Li, Siqi, Taran Driver, Philipp Rosenberger, Elio G. Champenois, Joseph Duris, Andre Al-Haddad, Vitali Averbukh et al. « Attosecond coherent electron motion in Auger-Meitner decay ». Science 375, n^o 6578 (21 janvier 2022) : 285–90. http://dx.doi.org/10.1126/science.abj2096.

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In quantum systems, coherent superpositions of electronic states evolve on ultrafast time scales (few femtoseconds to attoseconds; 1 attosecond = 0.001 femtoseconds = 10 −18 seconds), leading to a time-dependent charge density. Here we performed time-resolved measurements using attosecond soft x-ray pulses produced by a free-electron laser, to track the evolution of a coherent core-hole excitation in nitric oxide. Using an additional circularly polarized infrared laser pulse, we created a clock to time-resolve the electron dynamics and demonstrated control of the coherent electron motion by tuning the photon energy of the x-ray pulse. Core-excited states offer a fundamental test bed for studying coherent electron dynamics in highly excited and strongly correlated matter.

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Huang, Yindong, Jing Zhao, Zheng Shu, Yalei Zhu, Jinlei Liu, Wenpu Dong, Xiaowei Wang et al. « Ultrafast Hole Deformation Revealed by Molecular Attosecond Interferometry ». Ultrafast Science 2021 (7 juillet 2021) : 1–12. http://dx.doi.org/10.34133/2021/9837107.

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Understanding the evolution of molecular electronic structures is the key to explore and control photochemical reactions and photobiological processes. Subjected to strong laser fields, electronic holes are formed upon ionization and evolve in the attosecond timescale. It is crucial to probe the electronic dynamics in real time with attosecond-temporal and atomic-spatial precision. Here, we present molecular attosecond interferometry that enables the in situ manipulation of holes in carbon dioxide molecules via the interferometry of the phase-locked electrons (propagating in opposite directions) of a laser-triggered rotational wave packet. The joint measurement on high-harmonic and terahertz spectroscopy (HATS) provides a unique tool for understanding electron dynamics from picoseconds to attoseconds. The optimum phases of two-color pulses for controlling the electron wave packet are precisely determined owing to the robust reference provided with the terahertz pulse generation. It is noteworthy that the contribution of HOMO-1 and HOMO-2 increases reflecting the deformation of the hole as the harmonic order increases. Our method can be applied to study hole dynamics of complex molecules and electron correlations during the strong-field process. The threefold control through molecular alignment, laser polarization, and the two-color pulse phase delay allows the precise manipulation of the transient hole paving the way for new advances in attochemistry.

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Serrano, Javier, José Miguel Pablos-Marín et Carlos Hernández-García. « Machine-learning applied to the simulation of high harmonic generation driven by structured laser beams ». EPJ Web of Conferences 287 (2023) : 13018. http://dx.doi.org/10.1051/epjconf/202328713018.

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High harmonic generation (HHG) is one of the richest processes in strong-field physics. It allows to up-convert laser light from the infrared domain into the extreme-ultraviolet or even soft x-rays, that can be synthesized into laser pulses as short as tens of attoseconds. The exact simulation of such highly non-linear and non-perturbative process requires to couple the laser-driven wavepacket dynamics given by the three-dimensional time-dependent Schrödinger equation (3D-TDSE) with the Maxwell equations to account for macroscopic propagation. Such calculations are extremely demanding, well beyond the state-of-the-art computational capabilities, and approximations, such as the strong field approximation, need to be used. In this work we show that the use of machine learning, in particular deep neural networks, allows to simulate macroscopic HHG within the 3D-TDSE, revealing hidden signatures in the attosecond pulse emission that are neglected in the standard approximations. Our HHG method assisted by artificial intelligence is particularly suited to simulate the generation of soft x-ray structured attosecond pulses.

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Vinbladh, Jimmy, Jan Marcus Dahlström et Eva Lindroth. « Relativistic Two-Photon Matrix Elements for Attosecond Delays ». Atoms 10, n^o 3 (2 août 2022) : 80. http://dx.doi.org/10.3390/atoms10030080.

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The theory of one-photon ionization and two-photon above-threshold ionization is formulated for applications to heavy atoms in attosecond science by using Dirac–Fock formalism. A direct comparison of Wigner–Smith–Eisenbud delays for photoionization is made with delays from the Reconstruction of Attosecond Beating By Interference of Two-photon Transitions (RABBIT) method. Photoionization by an attosecond pulse train, consisting of monochromatic fields in the extreme ultraviolet range, is computed with many-body effects at the level of the relativistic random phase approximation (RRPA). Subsequent absorption and emission processes of infrared laser photons in RABBIT are evaluated by using static ionic potentials as well as asymptotic properties of relativistic Coulomb functions. As expected, light elements, such as argon, show negligible relativistic effects, whereas heavier elements, such a krypton and xenon, exhibit delays that depend on the fine-structure of the ionic target. The relativistic effects are notably close to ionization thresholds and Cooper minima with differences in fine-structure delays predicted to be as large as tens of attoseconds. The separability of relativistic RABBIT delays into a Wigner–Smith–Eisenbud delay and a universal continuum–continuum delay is studied with reasonable separability found for photoelectrons emitted along the laser polarization axis in agreement with prior non-relativistic results.

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Hu, Ronghao, Zheng Gong, Jinqing Yu, Yinren Shou, Meng Lv, Zhengming Sheng, Toshiki Tajima et Xueqing Yan. « Ultrahigh brightness attosecond electron beams from intense X-ray laser driven plasma photocathode ». International Journal of Modern Physics A 34, n^o 34 (10 décembre 2019) : 1943012. http://dx.doi.org/10.1142/s0217751x19430127.

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The emerging intense attosecond X-ray lasers can extend the Laser Wakefield Acceleration mechanism to higher plasma densities in which the acceleration gradients are greatly enhanced. Here we present simulation results of high quality electron acceleration driven by intense attosecond X-ray laser pulses in liquid methane. Ultrahigh brightness electron beams can be generated with 5-dimensional beam brightness over [Formula: see text]. The pulse duration of the electron bunch can be shorter than 20 as. Such unique electron sources can benefit research areas requiring crucial spatial and temporal resolutions.

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Li, Qianni, Xinrong Xu, Yanbo Wu, Debin Zou, Yan Yin et Tongpu Yu. « Generation of single circularly polarized attosecond pulses from near-critical density plasma irradiated by a two-color co-rotating circularly polarized laser ». Optics Express 30, n^o 22 (13 octobre 2022) : 40063. http://dx.doi.org/10.1364/oe.472982.

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In this paper, a new method is proposed to efficiently generate a single intense attosecond pulse with circular polarization (CP) through the interaction of an intense driving laser with a near-critical density plasma target. The driving laser is composed of two co-rotating CP lasers with similar frequencies but different pulse widths. When the matching condition is satisfied, the combined field is modulated to a short intense pulse followed by a weak tail. The resulting laser falling edge becomes steeper than the initial sub-pulses, which induces a quick one-time oscillation of the target surface. Meanwhile, the tail guarantees the energy to be compressed simultaneously in both polarization directions to the same extent, so that a single CP attosecond pulse can be produced efficiently and robustly via our method, which has been confirmed through extensive numerical simulations. In addition, our method makes it possible to generate a single CP attosecond pulse even for multi-cycle pulses that are already available for existing laser systems. This provides a novel way to advance the investigation of chiral-sensitive light-matter interactions in attosecond scales.

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Wikmark, Hampus, Chen Guo, Jan Vogelsang, Peter W. Smorenburg, Hélène Coudert-Alteirac, Jan Lahl, Jasper Peschel et al. « Spatiotemporal coupling of attosecond pulses ». Proceedings of the National Academy of Sciences 116, n^o 11 (1 mars 2019) : 4779–87. http://dx.doi.org/10.1073/pnas.1817626116.

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The shortest light pulses produced to date are of the order of a few tens of attoseconds, with central frequencies in the extreme UV range and bandwidths exceeding tens of electronvolts. They are often produced as a train of pulses separated by half the driving laser period, leading in the frequency domain to a spectrum of high, odd-order harmonics. As light pulses become shorter and more spectrally wide, the widely used approximation consisting of writing the optical waveform as a product of temporal and spatial amplitudes does not apply anymore. Here, we investigate the interplay of temporal and spatial properties of attosecond pulses. We show that the divergence and focus position of the generated harmonics often strongly depend on their frequency, leading to strong chromatic aberrations of the broadband attosecond pulses. Our argument uses a simple analytical model based on Gaussian optics, numerical propagation calculations, and experimental harmonic divergence measurements. This effect needs to be considered for future applications requiring high-quality focusing while retaining the broadband/ultrashort characteristics of the radiation.

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Zhang, Yi, Conglin Zhong, Shaoping Zhu, Xiantu He et Bin Qiao. « Divergence gating towards far-field isolated attosecond pulses ». New Journal of Physics 24, n^o 3 (1 mars 2022) : 033038. http://dx.doi.org/10.1088/1367-2630/ac59ec.

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Abstract Divergence gating, a novel method to generate far-field isolated attosecond pulses (IAPs) through controlling divergences of different pulses, is proposed and realized by relativistic chirped laser–plasma interactions. Utilizing various wavefronts for different cycles of incident chirped lasers, reflected harmonics with minimum divergences are obtained only at the peak cycle when plasma targets are adjusted to proper distances from foci of lasers. Therefore, the corresponding attosecond pulse is isolated in far field due to much slower decay during propagation than others. Confirmed by three-dimensional numerical simulations, millijoule-level sub-50 as IAPs with intensity approaching 1016 W cm−2 (1017–1018 W sr−1) are obtained by our scheme, where low-order harmonics can be preserved.

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Ye, Peng, Lénárd Gulyás Oldal, Tamás Csizmadia, Zoltán Filus, Tímea Grósz, Péter Jójárt, Imre Seres et al. « High-Flux 100 kHz Attosecond Pulse Source Driven by a High-Average Power Annular Laser Beam ». Ultrafast Science 2022 (1 mars 2022) : 1–10. http://dx.doi.org/10.34133/2022/9823783.

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High-repetition rate attosecond pulse sources are indispensable tools for time-resolved studies of electron dynamics, such as coincidence spectroscopy and experiments with high demands on statistics or signal-to-noise ratio, especially in the case of solid and big molecule samples in chemistry and biology. Although with the high-repetition rate lasers, such attosecond pulses in a pump-probe configuration are possible to achieve, until now, only a few such light sources have been demonstrated. Here, by shaping the driving laser to an annular beam, a 100 kHz attosecond pulse train (APT) is reported with the highest energy so far (51 pJ/shot) on target (269 pJ at generation) among the high-repetition rate systems (>10 kHz) in which the attosecond pulses were temporally characterized. The on-target pulse energy is maximized by reducing the losses from the reflections and filtering of the high harmonics, and an unprecedented 19% transmission rate from the generation point to the target position is achieved. At the same time, the probe beam is also annular and low loss of this beam is reached by using another holey mirror to combine with the APT. The advantages of using an annular beam to generate attosecond pulses with a high-average power laser are demonstrated experimentally and theoretically. The effect of nonlinear propagation in the generation medium on the annular-beam generation concept is also analyzed in detail.

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Gheorghe, M., F. P. G. Stochioiu, D. Manolache, M. R. Dijmărescu et D. Iliescu. « Analysis and development on general structure and characteristics of laser interferometry systems ». IOP Conference Series : Materials Science and Engineering 1268, n^o 1 (1 novembre 2022) : 012010. http://dx.doi.org/10.1088/1757-899x/1268/1/012010.

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The laser interferometry systems have been developed for scientific studies, industrial operations, artworks investigation, etc. They present common generic elements, such as laser, optics, beam, polarization, splitting, interferometry, etc., but also diverse specific components and features,such as He-Ne or femtosecond laser, quantum cascade lasers, non-polarising beam splitter, collimating lens, high reflecting mirror, photodetector, attosecond pulse train, etc., as the case. The paper presents, also, a development on general structure and characteristics of laser interferometry systems. Analytical descriptors are introduced for the main implied entities, as well as some qualitative features referring to measurement object, coordinate system, lasers, laser beams, optics, output beams, detectors, environmental sensors and compensation modules, electronics, process software and computer, assembly, calibration, etc. The conclusions accord attention to further laser interferometry development regarding the interacting processes, analytical modelling, simulation, operational characteristics, etc.

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Johnson, Allan S., Timur Avni, Esben W. Larsen, Dane R. Austin et Jon P. Marangos. « Attosecond soft X-ray high harmonic generation ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 377, n^o 2145 (avril 2019) : 20170468. http://dx.doi.org/10.1098/rsta.2017.0468.

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High harmonic generation (HHG) of an intense laser pulse is a highly nonlinear optical phenomenon that provides the only proven source of tabletop attosecond pulses, and it is the key technology in attosecond science. Recent developments in high-intensity infrared lasers have extended HHG beyond its traditional domain of the XUV spectral range (10–150 eV) into the soft X-ray regime (150 eV to 3 keV), allowing the compactness, stability and sub-femtosecond duration of HHG to be combined with the atomic site specificity and electronic/structural sensitivity of X-ray spectroscopy. HHG in the soft X-ray spectral region has significant differences from HHG in the XUV, which necessitate new approaches to generating and characterizing attosecond pulses. Here, we examine the challenges and opportunities of soft X-ray HHG, and we use simulations to examine the optimal generating conditions for the development of high-flux, attosecond-duration pulses in the soft X-ray spectral range. This article is part of the theme issue ‘Measurement of ultrafast electronic and structural dynamics with X-rays’.

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Feng, Liqiang, Hang Liu et Tianshu Chu. « Attosecond XUV sources generation from polarized gating two-color chirped pulse ». Modern Physics Letters B 29, n^o 21 (10 août 2015) : 1550111. http://dx.doi.org/10.1142/s0217984915501110.

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A promising method to generate the attosecond XUV sources from the high-order harmonic has been theoretically presented by controlling the polarized gating two-color chirped pulse. The results show that with the introduction of the chirps, the harmonic has been remarkably extended. Moreover, the harmonic interferences are very sensitive to the polarization angle between the two lasers. Particularly, when the polarization angle is equal to [Formula: see text], the supercontinuum with a single quantum path contribution is achieved, and a series of isolated attosecond pulses with the duration of 33 as are directly obtained. Further, by testing the influences of other laser parameters on the supercontinuum, we found that this polarized two-color chirped scheme can also be achieved in the multi-cycle pulse region, which is much better for experimental realization.

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Salières, Pascal, Thierry Ruchon et Bertrand Carré. « Les lasers attosecondes ». Photoniques, n^o 48 (septembre 2010) : 40–41. http://dx.doi.org/10.1051/photon/20104840.

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Kennedy, J. P., B. Dromey et M. Yeung. « Isolated ultra-bright attosecond pulses via non-collinear gating ». New Journal of Physics 24, n^o 11 (1 novembre 2022) : 113004. http://dx.doi.org/10.1088/1367-2630/ac9b80.

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Abstract When light with relativistic intensity is incident on a solid target, bright attosecond pulses of extreme ultraviolet and x-ray radiation can be generated in the reflected beam. Unfortunately, the use of multi-cycle laser pulses results in trains of these attosecond pulses. Here we investigate a non-collinear gating scheme applied to surface high-harmonic generation to allow for the extraction of a single intense attosecond pulse from this train. Using 3D and 2D particle in cell (PIC) simulations we demonstrate that it is possible to angularly isolate a single attosecond pulse from the main driving laser pulse using this interaction geometry with intensities I > 1020 W cm−2. This result opens the door to generating bright attosecond pulses from relativistic plasmas without the need to spectrally filter the driving laser pulse.

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Dombi, Péter, et Reinhard Kienberger. « A nobel prize for attosecond physics based on extreme nonlinear optics ». Europhysics News 55, n^o 1 (2024) : 16–21. http://dx.doi.org/10.1051/epn/2024106.

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Nobel Prizes related to lasers are awarded for their application in pioneering research areas, as was the case in 2023. Lasers are closely linked to 13-14 Physics Prizes, involving new discoveries, inventions, or research methods. The list is long, including optical fibers, optical tweezers, frequency combs, femtochemistry research, and research related to trapped particles. Lasers also play a crucial role in detecting gravitational waves and in holography. The 2023 award fits into this powerful series. The Prize and the oeuvre of Pierre Agostini, Ferenc Krausz and Anne L’Huillier shows how state-of-the-art laser technology enabled the emergence of extreme nonlinear optics and attophysics and, in turn, how attosecond science triggered the development of revolutionary light sources that are now used in medical diagnostics research or the semiconductor industry.

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Liu, Y., F. Y. Li, M. Zeng, M. Chen et Z. M. Sheng. « Ultra-intense attosecond pulses emitted from laser wakefields in non-uniform plasmas ». Laser and Particle Beams 31, n^o 2 (2 mai 2013) : 233–38. http://dx.doi.org/10.1017/s0263034613000220.

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AbstractA scheme of generating ultra-intense attosecond pulses in ultra-relativistic laser interaction with under-dense plasmas is proposed. The attosecond pulse emission is caused by an oscillating transverse current sheet formed by an electron density spike composed of trapped electrons in the laser wakefield and the residual transverse momentum of electrons left behind the laser pulse when its front is strongly modulated. As soon as the attosecond pulse emerges, it tends to feed back to further enhance the transverse electron momentum and the transverse current. Consequently, the attosecond pulse is enhanced and developed into a few cycles later until the density spike is depleted out due to the pump laser depletion. To control the formation of the transverse current sheet, a non-uniform plasma slab with an up-ramp density profile in front of a uniform region is adopted, which enables one to obtain attosecond pulses with higher amplitudes than that in a uniform plasma slab.

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Deng, Aihua, Yan Li, Yugan Weng, Zhiling Luo, Xitao Yu et Jiaolong Zeng. « Simulation Study on Attosecond Inverse Compton Scattering Source from Laser Wakefield Acceleration with Near-Threshold Ionization Injection ». Applied Sciences 14, n^o 17 (2 septembre 2024) : 7749. http://dx.doi.org/10.3390/app14177749.

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We present the generation of attosecond gamma rays via inverse Compton scattering within the framework of laser wakefield acceleration through 2D Particle-In-Cell simulations. Utilizing the near-threshold ionization injection mechanism, an attosecond micro-bunched electron beam characterized by a comb-like current density profile can be achieved with a linearly polarized laser at an intensity of a0 = 1.5. The micro-bunched beam provides a beam energy of approximately 300 MeV and achieves a minimum relative energy spread of about 1.64% after undergoing 2 mm of acceleration. In the inverse Compton scattering scheme, these attosecond electron micro-bunches interact with the reflected driving laser pulse, resulting in the attosecond gamma-ray radiation exhibiting similar structures. Individual spatial-separated gamma-ray pulses exhibit a length of approximately 260–300 as, with a critical energy of 2.0 ± 0.2 MeV. The separated attosecond gamma-ray source owns a peak brilliance of ~1022 photons s−1 mm−2 mrad−2 0.1% BW. This brilliance is competitive in a laboratory for multi-MeV γ-ray sources with a laser intensity of I = 5 × 1018 W/cm2. Such attosecond gamma-ray radiation offers promising applications requiring ultrashort X-ray/gamma ray sources.

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Su, Xinyang, Ruixue Zhu, Bolin Wang, Yu Bai, Tao Ding, Tianran Sun, Xing Lü, Jiying Peng et Yi Zheng. « Generation of 8–20 μm Mid-Infrared Ultrashort Femtosecond Laser Pulses via Difference Frequency Generation ». Photonics 9, n^o 6 (25 mai 2022) : 372. http://dx.doi.org/10.3390/photonics9060372.

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Mid-infrared (MIR) ultrashort laser pulses have a wide range of applications in the fields of environmental monitoring, laser medicine, food quality control, strong-field physics, attosecond science, and some other aspects. Recent years have seen great developments in MIR laser technologies. Traditional solid-state and fiber lasers focus on the research of the short-wavelength MIR region. However, due to the limitation of the gain medium, they still cannot cover the long-wavelength region from 8 to 20 µm. This paper summarizes the developments of 8–20 μm MIR ultrafast laser generation via difference frequency generation (DFG) and reviews related theoretical models. Finally, the feasibility of MIR power scaling by nonlinear-amplification DFG and methods for measuring the power of DFG-based MIR are analyzed from the author’s perspective.

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Schoenlein, Robert, Thomas Elsaesser, Karsten Holldack, Zhirong Huang, Henry Kapteyn, Margaret Murnane et Michael Woerner. « Recent advances in ultrafast X-ray sources ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 377, n^o 2145 (avril 2019) : 20180384. http://dx.doi.org/10.1098/rsta.2018.0384.

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Over more than a century, X-rays have transformed our understanding of the fundamental structure of matter and have been an indispensable tool for chemistry, physics, biology, materials science and related fields. Recent advances in ultrafast X-ray sources operating in the femtosecond to attosecond regimes have opened an important new frontier in X-ray science. These advances now enable: (i) sensitive probing of structural dynamics in matter on the fundamental timescales of atomic motion, (ii) element-specific probing of electronic structure and charge dynamics on fundamental timescales of electronic motion, and (iii) powerful new approaches for unravelling the coupling between electronic and atomic structural dynamics that underpin the properties and function of matter. Most notable is the recent realization of X-ray free-electron lasers (XFELs) with numerous new XFEL facilities in operation or under development worldwide. Advances in XFELs are complemented by advances in synchrotron-based and table-top laser-plasma X-ray sources now operating in the femtosecond regime, and laser-based high-order harmonic XUV sources operating in the attosecond regime. This article is part of the theme issue ‘Measurement of ultrafast electronic and structural dynamics with X-rays’.

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Glek, P. B., et A. M. Zheltikov. « Subcycle terahertz field waveforms clocked by attosecond high-harmonic pulses from relativistic laser plasmas ». Journal of Applied Physics 131, n^o 10 (14 mars 2022) : 103104. http://dx.doi.org/10.1063/5.0070670.

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A high-intensity ultrashort laser pulse interacting with a thin plasma target is shown to couple to plasma electrons, driving electron oscillations within the plasma and making these electrons bounce back and forth between plasma boundaries. Each time these recirculating electrons traverse the plasma boundary, they emit bright subcycle terahertz (THz) field waveforms via laser-driven coherent transition radiation. As a concurrent process, laser-driven electrons near the front surface of the plasma target are accelerated to relativistic velocities to emit high-order harmonics (HHs), giving rise to attosecond pulses of vacuum-ultraviolet radiation. These attosecond pulses are shown to provide a high-precision clock for subcycle THz field waveforms. We demonstrate that the delay time between HH pulses and THz waveforms can be tuned with an attosecond precision by varying the thickness of the plasma target, thus opening an avenue toward HH-pump–THz-probe studies of ultrafast processes on the attosecond time scale with table-top laser sources.

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Ang-Yang, Yu. « About Efficiency of High-order Harmonic Generation in Attosecond Physics ». International Journal of Clinical Virology 8, n^o 2 (2024) : 045–47. http://dx.doi.org/10.29328/journal.ijcv.1001061.

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For the first time, the interaction between Hydrogen atom and Free-Electron Lasers (FEL) is simulated. The conversion efficiency of High-order Harmonic Generation (HHG) can be enhanced by utilizing a two-color free electron laser with frequency multiplication. It is found that the conversion efficiency of HHG is improved to the largest extent when fourth-fold frequency multiplication is introduced into two-color FEL. The microscopic mechanism of improving the efficiency of HHG is analyzed and discussed.

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Kern, Christian, Michael Zürch et Christian Spielmann. « Limitations of Extreme Nonlinear Ultrafast Nanophotonics ». Nanophotonics 4, n^o 3 (1 janvier 2015) : 303–23. http://dx.doi.org/10.1515/nanoph-2015-0013.

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Abstract High-harmonic generation (HHG) has been established as an indispensable tool in optical spectroscopy. This effect arises for instance upon illumination of a noble gas with sub-picosecond laser pulses at focussed intensities significantly greater than 1012W/cm2. HHG provides a coherent light source in the extreme ultraviolet (XUV) spectral region, which is of importance in inner shell photo ionization of many atoms and molecules. Additionally, it intrinsically features light fields with unique temporal properties. Even in its simplest realization, XUV bursts of sub-femtosecond pulse lengths are released. More sophisticated schemes open the path to attosecond physics by offering single pulses of less than 100 attoseconds duration. Resonant optical antennas are important tools for coupling and enhancing electromagnetic fields on scales below their free-space wavelength. In a special application, placing field-enhancing plasmonic nano antennas at the interaction site of an HHG experiment has been claimed to boost local laser field strengths, from insufficient initial intensities to sufficient values. This was achieved with the use of arrays of bow-tie-shaped antennas of ∼ 100nm in length. However, the feasibility of this concept depends on the vulnerability of these nano-antennas to the still intense driving laser light.We show, by looking at a set of exemplary metallic structures, that the threshold fluence Fth of laser-induced damage (LID) is a greatly limiting factor for the proposed and tested schemes along these lines.We present our findings in the context of work done by other groups, giving an assessment of the feasibility and effectiveness of the proposed scheme.

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Xu, Peng, Xianglin Wang, Huabao Cao, Hao Yuan, Liang-Wen Pi, Yishan Wang, Yuxi Fu, Yonglin Bai et Wei Zhao. « Non-Collinear Attosecond Streaking without the Time Delay Scan ». Photonics 10, n^o 3 (20 mars 2023) : 331. http://dx.doi.org/10.3390/photonics10030331.

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Attosecond streaking provides an extremely high temporal resolution for characterizing light pulses and photoionization processes with attosecond (10−18 s) accuracy, which employs a laser as a streaking field to deflect electrons generated by photoionization. The current attosecond streaking requires a time delay scan between the attosecond pulses and streaking field with attosecond accuracy and a femtosecond range, which is difficult to realize real-time measurement. In this study, we theoretically propose a non-collinear attosecond streaking scheme without the time delay scan, enabling real-time and even the potential to perform single-shot attosecond pulse measurement. In the proposal, time-delay information is projected into longitudinal space, both horizontally and vertically, enabling attosecond pulse characterization with temporal-spatial coupling. From our calculation, down to 70 as pulses with pulse front and wavefront tilt are characterized with high accuracy. Our study not only provides a method toward real-time attosecond pulse measurement, but also an approach for attosecond pump-probe experiments without time delay scan.

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Chini, Michael, Steve Gilbertson, Sabih D. Khan et Zenghu Chang. « Characterizing ultrabroadband attosecond lasers ». Optics Express 18, n^o 12 (2 juin 2010) : 13006. http://dx.doi.org/10.1364/oe.18.013006.

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Kumar, Sandeep, Heung-Sik Kang et Dong-Eon Kim. « For the generation of an intense isolated pulse in hard X-ray region using X-ray free electron laser ». Laser and Particle Beams 30, n^o 3 (7 juin 2012) : 397–406. http://dx.doi.org/10.1017/s0263034612000237.

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AbstractFor a real, meaningful pump-probe experiment with attosecond temporal resolution, an intense isolated attosecond pulse is in demand. For that purpose we report the generation of an intense isolated attosecond pulse, especially in X-ray region using a current-enhanced self-amplified spontaneous emission in a free electron laser (FEL). We use a few cycle laser pulse to manipulate the electron-bunch inside a two-period planar wiggler. In our study, we employ the electron beam parameters of Pohang Accelerator Laboratory (PAL)-XFEL. The RF phase effect of accelerator columns on the longitudinal energy distribution profile and current profile of electron-bunch is also studied, aiming that these results can be experimentally realized in PAL-XFEL. We show indeed that the manipulation of electron-energy bunch profile may lead to the generation of an isolated attosecond hard X-ray pulse: 150 attosecond radiation pulse at 0.1 nm wavelength can be generated.

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Hosseinzadeh, Forouq, Vahid Darvishzadeh et Saeed Batebi. « High harmonic generation in organic molecules : a time-dependent density functional theory (TDDFT) approach ». Laser Physics 35, n^o 2 (17 janvier 2025) : 025401. https://doi.org/10.1088/1555-6611/ada754.

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Abstract We explore the fascinating process of high harmonic generation (HHG) in organic molecules, using time-dependent density functional theory to delve into the behaviors of methane, acetylene, benzene, and octane under varying laser conditions. Benzene, with its lower ionization potential and delocalized π-electrons, exhibited the most efficient harmonic generation, driven by the dominance of long electron trajectories that align well with the attosecond pulses produced. By carefully combining harmonics from the plateau region, we were able to generate an eighty attosecond pulse. Our study offers fresh insights into how organic molecules respond to intense laser fields, highlighting benzene’s potential as a prime candidate for creating ultrafast attosecond pulses. Our findings contribute to the broader understanding of HHG in organic systems, which has implications for attosecond science and ultrafast spectroscopy.

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Shi Zhuo, Chang Hong-Xiang, Wang Dong-Liang, Guo Hong-Yu, Dong Zi-Kai, Du Zhi-Hang, Liang Cheng-Bin et al. « High power, high energy four-channel fiber coherent beam combining system ». Acta Physica Sinica 74, n^o 1 (2025) : 0. http://dx.doi.org/10.7498/aps.74.20241476.

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Objective: Ultrafast fiber laser sources with mJ-level pulse energy and kilo-watt average power are of particular importance for various science fields such as attosecond lasers. Nowadays, several attosecond laser large scale facilities are under construction, including ELI-ALPS in Europe, SECUF in China, NeXUS in America and ALFA in Japan, to name a few. High performance femtosecond driven lasers are crucial for attosecond lasers and various ultrafast laser facilities. Fiber lasers have large surface-to-volume ratio for efficient cooling, and are suitable for high average power amplification. However, due to small mode area of fibers, detrimental nonlinear optical effects such as self-phase modulation, four wave mixing, and stimulated Raman scattering limit the peak power of pulse to hundreds of MW, corresponding to pulse energy of hundreds of μJ for femtosecond pulses in large mode area rod-type fibers. In addition, the average power of fiber lasers is limited by transverse mode instability, which decreases the stability and quality of beams above certain threshold. In rod type fibers, the threshold is around 250 W. Neither average power or pulse energy emitted by single fiber meets the demand of attosecond laser generation.<br>Methods: Further scaling of average power and pulse energy can be realized by coherent beam combining, which involves splitting pulses offered by an frontend laser and recombining them after amplification. It is essential for coherent beam combining to maintain the coherence of pulse replicas, which usually involves high speed photodiode detectors, piezo-driven mirrors, and other electronics forming a feedback system to actively control the phase of all replicas. We present a high-energy, high-power ultrafast fiber laser system employing filled-aperture coherent combination of four ytterbium-doped rod-type fiber amplifiers. The phase control is achieved using stochastic parallel gradient descent method. The frontend includes a passively mode-locked Yb-fiber oscillator, a stretcher, a pulse picker, and three fiber pre-amplifiers, which delivers 1-MHz stretched pulses centered at 1032-nm with 700-ps duration and 20-W average power. The pulse is split to four replicas by polarization beam-splitter and half-wave plate pairs, and the replicas pass through delay lines formed by piezo-driven mirrors before amplification. The pulse replicas are equally split and amplified to ensure the same accumulated nonlinear phase, and are combined by thin film polarizer and half-wave plate pairs. Small part of combined pulse is split and collected by a photodiode detector after filtered spectrally and spatially as signal for phase control. The combined pulse is compressed by a double-pass diffraction grating pair compressor including two 1739 l/mm gratings. Results and Discussions: At 1-MHz repetition rate, our 4-channel Yb-fiber coherent beam combining system generated a combined average power of 753-W with 87% combining efficiency. Utilizing tunable pulse stretcher together with compressor produces 0.67-mJ, 242-fs near transform-limited pulses with 89% compressing efficiency. The compressed pulse is centered at 1032-nm, and the spectrum width is 8.8-nm. The root-mean-square of average power is below 1% over 30-minute measurement, while the residual phase error is less than λ/23, indicating excellent stability at different time scales. The beam quality factor of the 0.67-mJ compressed pulses is 1.17×1.11. At 500-kHz, we obtained 1.07-mJ, 247-fs pulses with average power of 534-W, with similar efficiency, long-term stability and beam quality. The residual phase error decreases to less than λ/29, illustrating a better short-term stability. Further power and energy scaling can be achieved by increasing the number of channels. By adding delay and pointing stabilization system which are under development, it is possible to generate 1-kW, 2-mJ pulses using 8-channel CBC system.<br>Conclusions: In this paper, we implemented a 4-channel coherent beam combining system based on SPGD method, and obtained compressed 673-W, 673-µJ, 242-fs pulses at 1-MHz and 534-W, 1.07-mJ, 247-fs pulses at 500-kHz. Both power and energy can be further improved by increasing the channel number, and the delay and pointing stabilization system is also under construction. By adding coherent pulse stacking amplification technique, coherent beam combining system is supposed to generate up to 100-mJ pulse energy, which constitutes an enabling source for applications such as laser wake-field acceleration.

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Guo, Zhiyuan. « Research on the ultrafast laser in microscopy ». Theoretical and Natural Science 13, n^o 1 (30 novembre 2023) : 226–31. http://dx.doi.org/10.54254/2753-8818/13/20240851.

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Ultrafast laser technology has been making a huge difference in different areas, such as material processing, laser surgery, and military usage. In parallel with the development of ultrafast lasers, microscopy also greatly promotes modern science, even though there are still some shortcomings, and one of them is that it is hard to obtain information about dynamic samples. However, this shortcoming can be solved by using ultrafast laser technology. This review will introduce the concept of ultrafast laser technology and electron microscopy, while several limitations of conventional electron microscopy will be mentioned. This paper also introduces two advanced technology in ultrafast microscopy. Nowadays, by taking advantage of ultrafast laser technology, the dynamic sample can be observed with highly improved temporal resolutions, which are basically restricted by the duration of pulses, but the ultrafast laser technology makes the duration even reach the range of attoseconds. However, there are some limitations, such as aberration, still hamper the development of high spatial resolution in microscopy. It is hoped that the ultrafast microscopy will break through the bottleneck of traditional microscopy in the future.

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Teng Hao, 滕浩, 钟诗阳 Zhong Shiyang, 贺新奎 He Xinkui, 赵昆 Zhao Kun, 运晨霞 Yun Chenxia, 董朔 Dong Shuo et 魏志义 Wei Zhiyi. « 阿秒激光束线及应用研究平台（特邀） ». Acta Optica Sinica 44, n^o 17 (2024) : 1732016. http://dx.doi.org/10.3788/aos241424.

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Li, Yizhang, Qingyu Yang et Youwei Tian. « Crescent-shaped spatial distribution : radiation properties concerning beam waist from the cross collision of a tightly focused laser pulse and a relativistic electron ». Laser Physics 34, n^o 6 (16 mai 2024) : 065401. http://dx.doi.org/10.1088/1555-6611/ad485d.

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Abstract The radiation properties of the cross collision between a single electron and an intense laser pulse are researched by numerical simulation methods. Under the condition of tightly-focused laser, the electron trajectories, spatiotemporal distribution and spectrum are compared with that under non-tightly focused lasers. The results show that the torsion effect on the electron during the oscillation process is more notable after the tightly focused laser interacts with electron. The radiation it generates is asymmetric in space, and its time distribution is nearly unimodal and can be regarded as a single attosecond pulse. In frequency domain, the spectrum appears to be a supercontinuum. With the increase of beam waist radius, the symmetry of the spatial distribution enhances and time distribution also exhibits a three-peak structure that is symmetrical about the main peak. Furthermore, the spectrum changes from a supercontinuum to a multimodal distribution. The analysis turns out that tightly focused laser is more realistic compared to non-tightly focused laser or even plane wave, which benefits the design of high-quality x-rays in practical application.

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Teng, Hao, Xin-Kui He, Kun Zhao et Zhi-Yi Wei. « Attosecond laser station ». Chinese Physics B 27, n^o 7 (juillet 2018) : 074203. http://dx.doi.org/10.1088/1674-1056/27/7/074203.

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Hellemans, Alexander. « Attosecond Laser Pulses ». Scientific American 290, n^o 5 (mai 2004) : 38. http://dx.doi.org/10.1038/scientificamerican0504-38b.

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Varró, S., et Gy Farkas. « Attosecond electron pulses from interference of above-threshold de Broglie waves ». Laser and Particle Beams 26, n^o 1 (mars 2008) : 9–20. http://dx.doi.org/10.1017/s0263034608000037.

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AbstractIt is shown that the above-threshold electron de Broglie waves, generated by an intense laser pulse at a metal surface are interfering to yield attosecond electron pulses. This interference of the de Broglie waves is an analog on of the superposition of high harmonics generated from rare gas atoms, resulting in trains of attosecond light pulses. Our model is based on the Floquet analysis of the inelastic electron scattering on the oscillating double-layer potential, generated by the incoming laser field of long duration at the metal surface. Owing to the inherent kinematic dispersion, the propagation of attosecond de Broglie waves in vacuum is very different from that of attosecond light pulses, which propagate without changing shape. The clean attosecond structure of the current at the immediate vicinity of the metal surface is largely degraded due to the propagation, but it partially recovers at certain distances from the surface. Accordingly, above the metal surface, there exist “collapse bands,” where the electron current is erratic or noise-like, and there exist “revival layers,” where the electron current consist of ultrashort pulses of about 250 attosecond durations in the parameter range we considered. The maximum value of the current densities of such ultrashort electron pulses has been estimated to be on order of couple of tenth of mA/cm2. The attosecond structure of the electron photocurrent can perhaps be used for monitoring ultrafast relaxation processes in single atoms or in condensed matter.

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Beetar, John E., M. Nrisimhamurty, Tran-Chau Truong, Garima C. Nagar, Yangyang Liu, Jonathan Nesper, Omar Suarez et al. « Multioctave supercontinuum generation and frequency conversion based on rotational nonlinearity ». Science Advances 6, n^o 34 (août 2020) : eabb5375. http://dx.doi.org/10.1126/sciadv.abb5375.

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The field of attosecond science was first enabled by nonlinear compression of intense laser pulses to a duration below two optical cycles. Twenty years later, creating such short pulses still requires state-of-the-art few-cycle laser amplifiers to most efficiently exploit “instantaneous” optical nonlinearities in noble gases for spectral broadening and parametric frequency conversion. Here, we show that nonlinear compression can be much more efficient when driven in molecular gases by pulses substantially longer than a few cycles because of enhanced optical nonlinearity associated with rotational alignment. We use 80-cycle pulses from an industrial-grade laser amplifier to simultaneously drive molecular alignment and supercontinuum generation in a gas-filled capillary, producing more than two octaves of coherent bandwidth and achieving >45-fold compression to a duration of 1.6 cycles. As the enhanced nonlinearity is linked to rotational motion, the dynamics can be exploited for long-wavelength frequency conversion and compressing picosecond lasers.

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Luttmann, Martin, David Bresteau et Thierry Ruchon. « Pump-Probe Delay Controlled by Laser-dressed Ionization with Isolated Attosecond Pulses ». EPJ Web of Conferences 255 (2021) : 13004. http://dx.doi.org/10.1051/epjconf/202125513004.

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In a recent work [1], we demonstrated how laser-dressed ionization can be harnessed to control with attosecond accuracy the time delay between an extreme-ultraviolet (XUV) attosecond pulse train and an infrared (IR) femtosecond pulse. In this case, the comb-like photoelectron spectrum obtained by ionizing a gas target with the two superimposed beams exhibits peaks oscillating with the delay. Two of them can be found to oscillate in phase quadrature, allowing an optimal measurement and stabilization of the delay over a large range. Here we expand this technique to isolated attosecond pulses, by taking advantage of the delay-modulation of attosecond streaking traces. Although the photoelectron spectrum contains no peaks in that case, it is possible to reconstruct the pump-probe delay by simply monitoring the mean energy of the spectrum and the amplitude at this energy. In general, we find that active delay stabilization based on laser-dressed ionization is possible as long as the XUV pulses are chirped.

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Wang, Xinyu, Yuanyuan Qiu, Yue Qiao, Fuming Guo, Jun Wang, Gao Chen, Jigen Chen et Yujun Yang. « The Study on the Propagation of a Driving Laser Through Gas Target Using a Neural Network : Interaction of Intense Laser with Atoms ». Symmetry 16, n^o 12 (17 décembre 2024) : 1670. https://doi.org/10.3390/sym16121670.

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High-order harmonic generation is one of the ways to generate attosecond ultra-short pulses. In order to accurately simulate the high-order harmonic emission, it is necessary to perform fast and accurate calculations on the interaction between the atoms and strong laser fields. The accurate profile of the laser field is obtained from the propagation through the gas target. Under the conditions of longer wavelength driving lasers and higher gas densities, the calculation of the laser field becomes more challenging. In this paper, we utilize the driving laser electric field information obtained from numerically solving the three-dimensional Maxwell’s equations as data for machine learning, enabling the prediction of the propagation process of intense laser fields using an artificial neural network. It is found that the simulation based on frequency domain can improve the accuracy of electric field by two orders of magnitude compared with the simulation directly from time domain. On this basis, the feasibility of the transfer learning scheme for laser field prediction is further studied. This study lays a foundation for the rapid and accurate simulation of the interaction between intense laser and matter by using an artificial neural network scheme.

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Zhou, Chuliang, Ye Tian, Yushan Zeng, Zhinan Zeng et Ruxin Li. « Bright High-Harmonic Generation through Coherent Synchrotron Emission Based on the Polarization Gating Scheme ». Laser and Particle Beams 2022 (14 février 2022) : 1–10. http://dx.doi.org/10.1155/2022/6948110.

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Relativistic surface high harmonics, combined with the use of polarization gating, present a promising route towards intense single attosecond pulses. However, they impose stringent requirements on ultra-high laser contrast and are restricted by large intensity losses in real experiments. Here, we numerically demonstrate that by setting an optimal time delay in the polarization gating scheme, the intensity of the generated single attosecond pulses can become approximately 100 times stronger than that with nonoptimal time delay in the coherent synchrotron emission process. When a petawatt-class driving laser irradiates a solid target, an ultra-dense electron nanobunch and a strong space-charge sheath develop, and the accumulated electrostatic energy is only released in half of the laser cycle when this electron nanobunch moves backward. This process results in the emission of intense high harmonics. Our study provides a reliable method for developing bright attosecond extreme ultraviolet pulses.

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Karmakar, A., et A. Pukhov. « Collimated attosecond GeV electron bunches from ionization of high-Z material by radially polarized ultra-relativistic laser pulses ». Laser and Particle Beams 25, n^o 3 (5 juillet 2007) : 371–77. http://dx.doi.org/10.1017/s0263034607000249.

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Three dimensional Particle-in-Cell (3D-PIC) simulations of electron acceleration in vacuum with radially polarized ultra-intense laser beams have been performed. It is shown that single-cycle laser pulses efficiently accelerate a single attosecond electron bunch to GeV energies. When multi-cycle laser pulses are used, one has to employ ionization of high-Z materials to inject electrons in the accelerating phase at the laser pulse maximum. In this case, a train of highly collimated attosecond electron bunches with a quasi-monoenergetic spectra is produced. A comparison with electron acceleration by Gaussian laser pulses has been done. It is shown that the radially polarized laser pulses are superior both in the maximum energy gain and in the quality of the produced electron beams.

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Bandrauk, André D., et Hong Shon Nguyen. « Attosecond molecular spectroscopy The one-electron H2+ system ». Canadian Journal of Chemistry 82, n^o 6 (1 juin 2004) : 831–36. http://dx.doi.org/10.1139/v04-080.

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Numerical solutions of the time-dependent Schrödinger equation for a 1-D model non-BornOppenheimer H2+ are used to illustrate the nonlinear, nonperturbative response of molecules to intense (I ≥ 1013 W/cm2), ultrashort (t < 10 fs) laser pulses. Molecular high-order harmonic generation (MHOHG) is shown to be an example of such response, and the resulting nonlinear photon emission spectrum is shown to lead to the synthesis of single attosecond (1018 s) pulses. Application of such ultrashort pulses to the H2+ system results in localized electron wave packets whose motion can be detected by asymmetry in the photoelectron spectrum generated by a subsequent probe attosecond pulse, thus leading to measurement of electron motion in molecules on an attosecond time scale. Key words: attosecond spectroscopy, attosecond photoionization.

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Liu, Jiansheng, Changquan Xia, Li Liu, Ruxin Li et Zhizhan Xu. « Nonlinear Thomson backscattering of intense laser pulses by electrons trapped in plasma-vacuum boundary ». Laser and Particle Beams 27, n^o 3 (19 juin 2009) : 365–70. http://dx.doi.org/10.1017/s0263034609000287.

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AbstractWe present the idea of intensified attosecond X-ray generation based on nonlinear Thomson backscattering of an intense laser pulse by electrons trapped in plasma-vacuum boundary. Two frequency up-conversions due to the relativistic Doppler effect and longitudinal γ-spike effect are analyzed, respectively, where γ is the relativistic factor of the plasma surface. Relativistic resonance heating conditions should be used as a criterion for the experimental design to obtain efficient high-order harmonics and energetic electrons' generation at relatively low laser intensities. Shaping the laser field by proposing a detuned second-harmonic can generate a single attosecond pulse without spectral filtering.

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Ueda, Kiyoshi. « Science at X-ray Free Electron Lasers ». Applied Sciences 11, n^o 22 (11 novembre 2021) : 10622. http://dx.doi.org/10.3390/app112210622.

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Shim, Chi Hyun, Ki Moon Nam, Yong Woon Parc et Dong Eon Kim. « Isolated terawatt sub-attosecond high-energy x-ray pulse generated by an x-ray free-electron laser ». APL Photonics 7, n^o 5 (1 mai 2022) : 056105. http://dx.doi.org/10.1063/5.0067074.

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The endless quest for dynamics in natural phenomena has resulted in the generation and application of attosecond pulses to trace electron dynamics in atomic and molecular systems. The next challenge is to generate powerful pulses on the zeptosecond time scale, which is currently inaccessible. Through a simulation study, a new type of x-ray source that can generate an isolated terawatt sub-attosecond pulse at high-energy x rays by combining attosecond pulse technology with free-electron laser technology is proposed. The successful generation of a sub-attosecond pulse necessitates the consideration of nanometer-wide current-spikes, the sub-attosecond pulse amplification, and pulse duration and background noise control. The underlying interaction mechanism between a sub-attosecond pulse and a current-spike is closely investigated using the simulation results. The proposed method is expected to produce an isolated ∼700 zs pulse with a peak output of 2.9 TW at a photon energy of 247.5 keV.

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Hellemans, Alexander. « Attosecond lasers come of age ». Physics World 17, n^o 2 (février 2004) : 10. http://dx.doi.org/10.1088/2058-7058/17/2/17.

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KIM, Kyung Taec. « Measurement of a Photoionization Delay Using Attosecond Pulses ». Physics and High Technology 32, n^o 12 (29 décembre 2023) : 7–10. http://dx.doi.org/10.3938/phit.32.033.

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The Nobel Prize in Physics for 2023 was awarded to three distinguished scientists: Pierre Agostini, Ferenc Krausz, and Anne L’Huillier. This recognition honors their significant contributions in the field of experimental methods, specifically for generating attosecond pulses of light to study electron dynamics in matter. Anne L’Huillier and her research team made a groundbreaking discovery by utilizing a long-wavelength laser driver to achieve high harmonic generation. Pierre Agostini’s team accomplished the first-time measurement of the temporal profile of attosecond pulse trains, while Ferenc Krausz’s team successfully produced and measured an isolated attosecond pulse. These achievements have greatly advanced attosecond science, enabling the investigation of ultrafast electron dynamics in matter with unprecedented temporal resolution.

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Berrah, Nora. « A perspective for investigating photo-induced molecular dynamics from within with femtosecond free electron lasers ». Physical Chemistry Chemical Physics 19, n^o 30 (2017) : 19536–44. http://dx.doi.org/10.1039/c7cp01996c.

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Photo-induced molecular dynamics can now be investigated using free electron lasers (FELs) whose attributes are unprecedented brightness, few femtosecond pulses duration and in the near future few hundreds of attosecond pulse duration.

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Martín-Hernández, Rodrigo, Luis Plaja et Carlos Hernández-García. « Fourier-limited attosecond pulse generation with magnetically pumped high-order harmonic generation ». EPJ Web of Conferences 266 (2022) : 08006. http://dx.doi.org/10.1051/epjconf/202226608006.

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After more than two decades of attosecond physics, the generation and control of the shortest laser pulses available remains as a complex task. One of the main limitations of reducing the temporal duration of attosecond pulses emitted from high-order harmonic generation (HHG) is the attochirp. In this contribution, we demonstrate that HHG assisted by strong fast oscillating magnetic fields enables the generation of Fourierlimited attosecond pulses in the water window. In short, the magnetic field generates a nanowire-like structure, which transversally confines the electronic wavefunction in the HHG process. We demonstrate that the resulting HHG spectrum extends well beyond the semiclassical cutoff frequency, and most interestingly, it is emitted in the form of few-cycle, Fourier-limited, attosecond pulses.

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Maroju, Praveen Kumar, Cesare Grazioli, Michele Di Fraia, Matteo Moioli, Dominik Ertel, Hamed Ahmadi, Oksana Plekan et al. « Complex Attosecond Waveform Synthesis at FEL FERMI ». Applied Sciences 11, n^o 21 (20 octobre 2021) : 9791. http://dx.doi.org/10.3390/app11219791.

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Free-electron lasers (FELs) can produce radiation in the short wavelength range extending from the extreme ultraviolet (XUV) to the X-rays with a few to a few tens of femtoseconds pulse duration. These facilities have enabled significant breakthroughs in the field of atomic, molecular, and optical physics, implementing different schemes based on two-color photoionization mechanisms. In this article, we present the generation of attosecond pulse trains (APTs) at the seeded FEL FERMI using the beating of multiple phase-locked harmonics. We demonstrate the complex attosecond waveform shaping of the generated APTs, exploiting the ability to manipulate independently the amplitudes and the phases of the harmonics. The described generalized attosecond waveform synthesis technique with an arbitrary number of phase-locked harmonics will allow the generation of sub-100 as pulses with programmable electric fields.

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Cho, Adrian, et Daniel Clery. « Sculptors of short light pulses win physics Nobel ». Science 382, n^o 6666 (6 octobre 2023) : 23. http://dx.doi.org/10.1126/science.adl1812.

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