Publications

2018

• Highly scalable femtosecond coherent beam combining system of high power fiber amplifiers
  
  • Heilmann Anke
  , 2018. Future applications of high power ultrafast laser systems require simultaneously high average and peak powers. A technique which has proved to be capable of meeting these demands is coherent beam combining (CBC).In this technique, the beam is spatially split prior to amplification, and coherently recombined in one single beam afterwards. In order to achieve an efficient recombination, the spatial and spectral properties of all beams need to be perfectly matched.For applications such as particle acceleration, the coherent combining of several thousands of fibers needs to be considered. It is thus necessary to investigate highly scalable CBC architectures.The XCAN project aims at a first demonstration of such a scalable setup by coherently combining 61 fiber amplifiers. In order to study the scientific and technical challenges of such a system, a downscaled version consisting of seven fibers has been implemented.The design and characterization of this prototype is the subject of this thesis.As a starting point, numerical simulations have been performed in order to estimate the maximum tolerable mismatches between the spatial and spectral properties of the beams.Based on this modeling work, a seven fiber CBC system has been assembled and characterized. The obtained results are very promising and imply that our setup is well suited for the accommodation of all 61 fibers of the final XCAN demonstrator. (10.70675/fd6d787dz22f4z4c22z84c6zc6a6e7885ffc)
  DOI : 10.70675/fd6d787dz22f4z4c22z84c6zc6a6e7885ffc
• Classical and quantum description of plasma and radiation in strong fields
  
  • Niel Fabien
  , 2018. With the advent of the new generation of petawatt lasers, it will become more and more important in the near future to study strong-field QED. As previously mentioned, it can either serve as a new nonperturbative regime for physics beyond the standard model, allow to understand extreme astro-physics events (such as magnetars), or even become a dominant effect in laser-plasma interaction.However, in all these cases, the system under consideration is not a single particle as usually consid-ered in pure SFQED works, but will be a collection of such particles (either electron/photon beams or pair plasmas etc.). It will therefore be important to understand how the behavior of single particles affect the overall state of the system, and in particular the shape of its electron distribution function and of its radiated spectrum. This is what this work is focused on. The manuscript is organized as fol-lows In chapter 2, we introduce the basis of classical electrodynamics and derive all the results and notations that will be useful in the rest of this thesis. We explain why any accelerated charge radiates an electromagnetic field and compute the spectrum radiated by an ultrarelativistic electron. We show that it follows the well-know synchrotron spectrum. When the energy radiated by the electron is no longer negligible, the emitted radiation will counteract on the trajectory of the particle itself. This is the so-called radiation reaction. We derive the Lorentz-Abraham-Dirac (LAD) equation, that describes the motion of an electron, taking into account radiation reaction (RR). We show that this equation presents unphysical solutions and deduce the Landau-Lifshitz (LL) equation, that we will use to describe RR in the classical regime in the rest of this work. We then consider the solution of the LL equation in simplified fields such as plane-waves or constant uniform magnetic fields. The classical radiation dominated regime (CRDR) is described and the limit of validity of the classical description analyzed. Chapter 3 : when the electron quantum parameter is of the order of unity, emitted photons can have an energy close to that of the emitting electron. In this case, radiation reaction can no longer be treated classically. In this chapter, we present the basis of quantum electrodynamics (QED), which is the framework in which such quantum effects can be computed. We derive the Volkov states that take into account exactly the nonperturbative coupling between the electron and the strong background field. These fields are used in the so-called Furry picture in order to compute the different QED pro-cesses such as the nonlinear Compton scattering or the nonlinear Breit-Wheeler process. The cross-sections for these two processes are then analyzed. Chapter 4 : so far, the description of radiation concerned only single particles. Here we introduce the Vlasov equation that describes the evolution of the function distribution of a set a particles. We then see how to modify this equation in order to take into account classical and quantum RR. The numeri-cal resolution of this equation, together with Maxwell's equations is then described, in particular through the well-known PIC loop. We describe how to modify this classical PIC loop in order to in-clude classical and quantum RR, in particular through the use of a Monte-Carlo module. Chapter 5 : we present the state of the art on RR in our community and a brief introduction to the sec-ond part of this thesis where most of the original results are reported. Chapter 6 : after a brief reminder of the Landau-Lifshitz (LL) equation, which describes radiation re-action (RR) in classical electrodynamics (CED) as a deterministic force in the particle momentum equation, we recall the emission properties of a quantum radiating electron. We then turn our attention to the linear Boltzmann equation which is at the center of the kinetic description of RR explored in this thesis [...] (10.70675/526e8f3bz7b93z449bza261z6ede59baabb8)
  DOI : 10.70675/526e8f3bz7b93z449bza261z6ede59baabb8
• Spectroscopie X de plasmas chauds et denses générés par lasers UHI et XFEL
  
  • Condamine Florian
  , 2018. Cette thèse est centrée sur l'étude de la distribution des états de charges, des populations et des fréquences dans un plasma chaud et dense par l'utilisation de méthodes spectroscopiques X. Ces recherches sont fondamentales dans de nombreux domaines. Les études autour des plasmas fortement couplés, la science de la fusion ou l'astrophysique sont des exemples d'applications. Cette thèse présente un travail expérimental agrémenté de simulations dans un but de confrontation des résultats. Les 2 premières études sont concentrées sur l'étude de l'émission X des états de charge de la couche M du Cuivre dans un plasma chaud et dense. Les expériences sont réalisées avec des régimes lasers différents. La première a lieu sur une installation ns-kJ et la seconde avec un laser UHI. Les résultats de très haute résolution témoignent de manière détaillée de l'impact des électrons chauds sur l'émission X de la cible. Des perspectives sont ouvertes par l'observation de phénomènes sous-estimés par les simulations. La fin de ce travail est consacrée à l'étude de la photo-absorption et de la redistribution de fréquences au sein d'un plasma chaud et dense. Pour la première fois, une cible chauffée par laser a été scannée par seeded XFEL afin de mettre à l'épreuve nos modèles. Les résultats obtenus indiquent une mauvaise compréhension de différents phénomènes et ouvrent de nombreuses perspectives. (10.70675/e2c991c6z1be8z4778zae3fz6c6d45f17638)
  DOI : 10.70675/e2c991c6z1be8z4778zae3fz6c6d45f17638
• Signatures of fluid and kinetic properties in the energy distributions of multicharged Ta ions from nanosecond-laser-heated plasma
  
  • Gobet F.
  • Comet M.
  • Marquès J.-R.
  • Méot V.
  • Raymond X.
  • Versteegen M.
  • Henares J.-L.
  • Morice O.
  Physical Review E, American Physical Society (APS), 2018, 98 (6), pp.063202. The energy distributions of tantalum ions produced in a nanosecond laser-heated plasma at 4×1015W/cm2 are experimentally and theoretically investigated. They are measured far from the target with an electrostatic spectrometer and charge collectors. Shadowgraphy and interferometry are used to characterize the plasma dynamics in the first nanoseconds of the plasma expansion for electron densities ranging from 1018 to 1020cm−3. The experimental data clearly show two components in the energy distributions which depend on the ion charge states. These components are discussed in light of fluid and kinetic descriptions of the expanding plasma. In particular, quantitative comparisons with calculations performed with three-dimensional hydrodynamic (Troll) and 1D3V particle-in cell-codes demonstrate that a double layer created at the plasma-vacuum interface plays a crucial role in the acceleration of the highest-charge-state ions at high energy. (10.1103/PhysRevE.98.063202)
  DOI : 10.1103/PhysRevE.98.063202
• Advanced high resolution x-ray diagnostic for HEDP experiments
  
  • Faenov A. Y.
  • Pikuz T. A.
  • Mabey P.
  • Albertazzi Bruno
  • Michel Th.
  • Rigon G.
  • Pikuz S. A.
  • Buzmakov A.
  • Makarov S.
  • Ozaki N.
  • Matsuoka T.
  • Katagiri K.
  • Miyanishi K.
  • Takahashi K.
  • Tanaka K. A.
  • Inubushi Y.
  • Togashi T.
  • Yabuuchi T.
  • Yabashi M.
  • Casner A.
  • Kodama R.
  • Koenig M.
  Scientific Reports, Nature Publishing Group, 2018, 8 (1), pp.16407 (2018). High resolution X-ray imaging is crucial for many high energy density physics (HEDP) experiments. Recently developed techniques to improve resolution have, however, come at the cost of a decreased field of view. In this paper, an innovative experimental detector for X-ray imaging in the context of HEDP experiments with high spatial resolution, as well as a large field of view, is presented. The platform is based on coupling an X-ray backligther source with a Lithium Fluoride detector, characterized by its large dynamic range. A spatial resolution of 2 µm over a field of view greater than 2 mm2 is reported. The platform was benchmarked with both an X-ray free electron laser (XFEL) and an X-ray source produced by a short pulse laser. First, using a non-coherent short pulse laser-produced backlighter, reduced penumbra blurring, as a result of the large size of the X-ray source, is shown. Secondly, we demonstrate phase contrast imaging with a fully coherent monochromatic XFEL beam. Modeling of the absorption and phase contrast transmission of X-ray radiation passing through various targets is presented. (10.1038/s41598-018-34717-9)
  DOI : 10.1038/s41598-018-34717-9
• X-ray Spectroscopy Based Diagnostic of GigaGauss Magnetic Fields during Relativistic Laser-Plasma Interactions
  
  • Dalimier Elisabeth
  • Oks Eugene
  Atoms, MDPI, 2018, 6 (4), pp.60. (10.3390/atoms6040060)
  DOI : 10.3390/atoms6040060
• Erratum: “Setup for meV-resolution inelastic X-ray scattering measurements and X-ray diffraction at the Matter in Extreme Conditions endstation at the Linac Coherent Light Source” [Rev. Sci. Instrum. 89, 10F104 (2018)]
  
  • Mc Bride E.
  • White T.
  • Descamps A.
  • Fletcher L.
  • Appel K.
  • Condamine F.
  • Curry C.
  • Dallari F.
  • Funk S.
  • Galtier E.
  • Gamboa E.
  • Gauthier M.
  • Goede S.
  • Kim J.
  • Lee H.
  • Ofori-Okai B.
  • Oliver M.
  • Rigby A.
  • Schoenwaelder C.
  • Sun P.
  • Tschentscher Th.
  • Witte B.
  • Zastrau U.
  • Gregori G.
  • Nagler B.
  • Hastings J.
  • Glenzer S.
  • Monaco G.
  Review of Scientific Instruments, American Institute of Physics, 2018, 89 (12), pp.129901. (10.1063/1.5084054)
  DOI : 10.1063/1.5084054
• Publisher Correction: Laser-accelerated particle beams for stress testing of materials
  
  • Barberio M.
  • Scisciò M.
  • Vallières S.
  • Cardelli F.
  • Chen S.
  • Famulari G.
  • Gangolf T.
  • Revet G.
  • Schiavi A.
  • Senzacqua M.
  • Antici P.
  Nature Communications, Nature Publishing Group, 2018, 9, pp.1966. The original version of the Supplementary Information associated with this Article contained an error in Supplementary Figure 3, in which all panels, with the exception of the bottom-left ‘Ti’ panel, were blank. The HTML has been updated to include a corrected version of the Supplementary Information. (10.1038/s41467-018-04345-y)
  DOI : 10.1038/s41467-018-04345-y
• Laser-accelerated particle beams for stress testing of materials
  
  • Barberio M.
  • Scisciò M.
  • Vallières S.
  • Cardelli F.
  • Chen S.
  • Famulari G.
  • Gangolf T.
  • Revet G.
  • Schiavi A.
  • Senzacqua M.
  • Antici P.
  Nature Communications, Nature Publishing Group, 2018, 9, pp.372. Laser-driven particle acceleration, obtained by irradiation of a solid target using an ultra-intense (I > 10$^{18}$ W/cm$^2$) short-pulse (duration <1 ps) laser, is a growing field of interest, in particular for its manifold potential applications in different domains. Here, we provide experimental evidence that laser-generated particles, in particular protons, can be used for stress testing materials and are particularly suited for identifying materials to be used in harsh conditions. We show that these laser-generated protons can produce, in a very short time scale, a strong mechanical and thermal damage, that, given the short irradiation time, does not allow for recovery of the material. We confirm this by analyzing changes in the mechanical, optical, electrical, and morphological properties of five materials of interest to be used in harsh conditions. (10.1038/s41467-017-02675-x)
  DOI : 10.1038/s41467-017-02675-x
• Guiding of relativistic electron beams in dense matter by laser-driven magnetostatic fields
  
  • Bailly-Grandvaux M.
  • Santos J.
  • Bellei C.
  • Forestier-Colleoni P.
  • Fujioka S.
  • Giuffrida L.
  • Honrubia J. J.
  • Batani D.
  • Bouillaud R.
  • Chevrot M.
  • Cross J.
  • Crowston R.
  • Dorard S.
  • Dubois J.
  • Ehret M.
  • Gregori G.
  • Hulin S.
  • Kojima S.
  • Loyez E.
  • Marquès J.
  • Morace A.
  • Nicolai Ph.
  • Roth M.
  • Sakata S.
  • Schaumann G.
  • Serres F.
  • Servel J.
  • Tikhonchuk V.
  • Woolsey N.
  • Zhang Z.
  Nature Communications, Nature Publishing Group, 2018, 9, pp.102. Intense lasers interacting with dense targets accelerate relativistic electron beams, which transport part of the laser energy into the target depth. However, the overall laser-to-target energy coupling efficiency is impaired by the large divergence of the electron beam, intrinsic to the laser–plasma interaction. Here we demonstrate that an efficient guiding of MeV electrons with about 30 MA current in solid matter is obtained by imposing a laser-driven longitudinal magnetostatic field of 600 T. In the magnetized conditions the transported energy density and the peak background electron temperature at the 60-μm-thick target's rear surface rise by about a factor of five, as unfolded from benchmarked simulations. Such an improvement of energy-density flux through dense matter paves the ground for advances in laser-driven intense sources of energetic particles and radiation, driving matter to extreme temperatures, reaching states relevant for planetary or stellar science as yet inaccessible at the laboratory scale and achieving high-gain laser-driven thermonuclear fusion (10.1038/s41467-017-02641-7)
  DOI : 10.1038/s41467-017-02641-7
• Self-generated surface magnetic fields inhibit laser-driven sheath acceleration of high-energy protons
  
  • Nakatsutsumi M.
  • Sentoku Y.
  • Korzhimanov A.
  • Chen S.
  • Buffechoux S.
  • Kon A.
  • Atherton B.
  • Audebert P.
  • Geissel M.
  • Hurd L.
  • Kimmel M.
  • Rambo P.
  • Schollmeier M.
  • Schwarz J.
  • Starodubtsev M.
  • Gremillet L.
  • Kodama R.
  • Fuchs J.
  Nature Communications, Nature Publishing Group, 2018, 9, pp.280. High-intensity lasers interacting with solid foils produce copious numbers of relativistic electrons, which in turn create strong sheath electric fields around the target. The proton beams accelerated in such fields have remarkable properties, enabling ultrafast radiography of plasma phenomena or isochoric heating of dense materials. In view of longer-term multidisciplinary purposes (e.g., spallation neutron sources or cancer therapy), the current challenge is to achieve proton energies well in excess of 100 MeV, which is commonly thought to be possible by raising the on-target laser intensity. Here we present experimental and numerical results demonstrating that magnetostatic fields self-generated on the target surface may pose a fundamental limit to sheath-driven ion acceleration for high enough laser intensities. Those fields can be strong enough (~10$^5$ T at laser intensities ~10$^{21}$ W cm$^{–2}$) to magnetize the sheath electrons and deflect protons off the accelerating region, hence degrading the maximum energy the latter can acquire. (10.1038/s41467-017-02436-w)
  DOI : 10.1038/s41467-017-02436-w
• Some views on the European HEDP-UHI laser and scientific landscape
  
  • Jacquemot S
  , 2018.
• Highly Scalable Coherent Beam Combining of Femtosecond Fiber Chirped-Pulse Amplifiers
  
  • Heilmann Anke
  • Le Dortz Jérémy
  • Daniault Louis
  • Fsaifes Ihsan
  • Bellanger Séverine
  • Bourderionnet Jérôme
  • Larat Christian
  • Lallier Eric
  • Antier Marie
  • Durand Eric
  • Simon-Boisson Christophe
  • Brignon Arnaud
  • Chanteloup Jean-Christophe
  , 2018. We report on the coherent beam combining of seven fiber chirped-pulse amplifiers using a highly scalable architecture. A combining efficiency of 48% is obtained in linear regime, yielding 71 W pump-limited average power after compression, with a phase noise between two fibers as low as λ/38 RMS. The experiment is operated at high B-integral, with only little impact on the combining efficiency as well as on the temporal and spatial properties of the combined beam.
• Thermally-induced-anisotropy issues in oriented cubic laser crystals, the cryogenically cooled Yb:CaF2 case
  
  • Genevrier Kevin
  • Papadopoulos Dimitris
  • Besbes Mondher
  • Camy Patrice
  • Doualan Jean-Louis
  • Moncorgé Richard
  • Georges Patrick
  • Druon Frédéric
  Applied Physics B - Laser and Optics, Springer Verlag, 2018, 124 (11). (10.1007/s00340-018-7077-8)
  DOI : 10.1007/s00340-018-7077-8
• Uphill acceleration in a spatially modulated electrostatic field particle accelerator
  
  • Almansa I.
  • Burton D.
  • Cairns R. A.
  • Marini S.
  • Peter E.
  • Rizzato F.
  • Russman F.
  Physics of Plasmas, American Institute of Physics, 2018, 25 (11), pp.113107. (10.1063/1.5049711)
  DOI : 10.1063/1.5049711
• Two-channel high-resolution quasi-monochromatic X-ray imager for Al and Ti plasma
  
  • Do A.
  • Briat M.
  • Baton S.
  • Krumrey M.
  • Lecherbourg L.
  • Loupias B.
  • Perez F.
  • Renaudin P.
  • Rubbelynck C.
  • Troussel Ph.
  Review of Scientific Instruments, American Institute of Physics, 2018, 89 (11), pp.113702. High-resolution, high-sensitivity X-ray imaging is a real challenge in high-energy density plasma experiments. We present an improved design of the Fresnel ultra high-resolution imager instrument. Using an Ultra-High-Intensity (UHI) laser to generate hot and dense plasma in a small volume of an Al-Ti mixed target provides simultaneous imaging of both Al and Ti X-ray emission. Specifically, the Al Heβ (or Lyβ) and the Ti Heα lines are imaged with a resolution of (2.7 ± 0.3) μm and (5.5 ± 0.3) μm, respectively. It features two transmission Fresnel phase zone plates fabricated on the same substrate, each associated with a multilayer mirror for spectral selection. Their spatial resolution has been measured on the PTB synchrotron radiation facility laboratory at BESSY II and on the EQUINOX laser facility. Results obtained on an UHI experiment highlight the difference of emission zone sizes between Al and Ti lines and the versatility of this instrument. (10.1063/1.5042069)
  DOI : 10.1063/1.5042069
• Efficient Modeling of Laser Wakefield Acceleration Through the PIC Code Smilei in CILEX Project
  
  • Massimo Francesco
  • Beck Arnaud
  • Derouillat Julien
  • Grech Mickael
  • Pérez Frédéric
  • Specka Arnd
  • Zemzemi Imen
  , 2019, pp.MOPAG02. The design of plasma acceleration facilities requires considerable simulation effort for each part of the machine, from the plasma injector and/or accelerator stage(s), to the beam transport stage, from which the accelerated beams will be brought to the users or possibly to another plasma stage. The urgent issues and challenges in simulation of multi-stage acceleration with the Apollon laser of CILEX facility will be addressed. To simulate the beam injection in the second plasma stage, additional physical models have been introduced and tested in the open source Particle in Cell collaborative code Smilei. The efficient initialisation of arbitrary relativistic particle beam distributions through a Python interface allowing code coupling and the self consistent initialisation of their electromagnetic fields will be presented. The comparison between a full PIC simulation and a simulation with a recently developed envelope model, which allows to drastically reduce the computational time, will be also shown for a test case of laser wakefield acceleration of an externally injected electron beam. (10.18429/JACoW-ICAP2018-MOPAG02)
  DOI : 10.18429/JACoW-ICAP2018-MOPAG02
• Absolute calibration of microchannel plate detector for carbon ions up to 250 MeV
  
  • Mcilvenny A.
  • Doria D.
  • Romagnani L.
  • Ahmed H.
  • Martin P.
  • Williamson S.D.R.
  • Ditter E.J.
  • Ettlinger O.
  • Hicks G.S.
  • Mckenna P.
  • Najmudin Z.
  • Neely D.
  • Kar S.
  • Borghesi M.
  , 2019, 14 (04), pp.C04002. A 375TW 40fs pulse was used at the ASTRA GEMINI facility located at the Rutherford Appleton Laboratory U.K. for investigating novel ion acceleration regimes employing ultrathin foil targets. An online detection system consisting of a Thomson Parabola Spectrometer (TPS)—Microchannel Plate (MCP) was used to determine maximum energies and spectra per species. The response of the MCP was calibrated for absolute particle (carbon) number per steradian using CR-39 up to 21 MeV/nucleon. This calibration provides a useful reference for a widely used diagnostic arrangement. (10.1088/1748-0221/14/04/C04002)
  DOI : 10.1088/1748-0221/14/04/C04002
• Characterization of a two-channel, high resolution hard x-ray microscope using Fresnel zone plates for laser-plasma interaction experiments
  
  • Do A.
  • Briat M.
  • Chaleil A.
  • Rubbelynck C.
  • Lebugle M.
  • David C.
  • Troussel P.
  Review of Scientific Instruments, American Institute of Physics, 2018, 89 (10), pp.10G122. (10.1063/1.5039326)
  DOI : 10.1063/1.5039326
• X-ray backlighter requirements for refraction-based electron density diagnostics through Talbot-Lau deflectometry
  
  • Valdivia M.
  • Veloso F.
  • Stutman D.
  • Stoeckl C.
  • Mileham C.
  • Begishev I.
  • Theobald W.
  • Vescovi M.
  • Useche W.
  • Regan S.
  • Albertazzi Bruno
  • Rigon G.
  • Mabey P.
  • Michel T.
  • Pikuz S.
  • Koenig M.
  • Casner A.
  Review of Scientific Instruments, American Institute of Physics, 2018, 89 (10), pp.10G127. (10.1063/1.5039342)
  DOI : 10.1063/1.5039342
• Mise en phase active de fibres laser en régime femtoseconde par méthode interférométrique
  
  • Le Dortz Jérémy
  , 2018. Les sources lasers femtosecondes sont utilisées dans grand nombre d’applications (industrielles, médicales, de recherche fondamentale) avec un besoin croissant d’impulsions très énergétiques à haut taux de répétition. Bien que la technologie Ti:Saphir fournisse des impulsions PetaWatt, son taux de répétition s’avère limité. Une alternative est l’utilisation de la technologie fibrée. Cependant, l’énergie extractible d’une seule fibre est intrinsèquement limitée.Une solution prometteuse est alors de réaliser une combinaison de fibres (jusqu’à plus de 10 000 fibres pour l’accélération de particules). La combinaison de fibres par méthode interférométrique (avec un record de 64 fibres combinées en régime continu) a prouvé qu’elle était un excellent candidat pour la combinaison d’un grand nombre de fibres.La collaboration XCAN entre l’Ecole Polytechnique et Thales, vise à réaliser un démonstrateur de combinaison cohérente de 61 fibres amplifiées en régime femtoseconde. Les travaux menés au cours de cette thèse s’inscrivent dans ce projet.Dans un premier temps, afin d’étudier les points durs inhérents au régime femtoseconde tout en s’affranchissant des difficultés liées à l’amplification, la méthode interférométique en régime femtoseconde a été étudiée sur un démonstrateur passif, c’est-à-dire sans amplification, de 19 fibres. Une fois la méthode de mise en phase validée celle-ci a pu être testée avec succès sur le démonstrateur avec amplification du projet XCAN.Nous présentons également les travaux menés afin d’augmenter un paramètre clé des systèmes de combinaison de faisceaux à savoir : l’efficacité de combinaison du système laser. Pour cela, nous avons réalisé une mise en forme de faisceaux issus des fibres de la tête optique. Cette mise en forme, gaussien vers super-gaussien, est réalisée à l’aide de deux réseaux de lames de phase dont nous présenterons le calcul des profils asphériques. Afin de valider expérimentalement nos simulations et après réalisation des lames de phase nous avons pu tester celles-ci sur le démonstrateur passif, démontrant une augmentation de 14 %.Les travaux présentés dans ce manuscrit présentent ainsi les premiers par vers la réalisation d’une nouvelle architecture laser massivement parallèle, capable de délivrer à la fois une haute puissance crête et une haute puissance moyenne. (10.70675/324f9234zddb9z449cz9b05z5043caae3671)
  DOI : 10.70675/324f9234zddb9z449cz9b05z5043caae3671
• Spatiotemporal study on a PW laser : Theoretical models, measurement methods and experimental results
  
  • Ranc L.
  • Zou J. P.
  • Le Blanc C.
  • Radier C
  • Simon Boisson C.
  • Druon Frédéric
  • Papadopoulos Dimitrios
  , 2018.
• XCAN: a highly scalable femtosecond coherent amplification network
  
  • Heilmann Anke
  • Le Dortz² Jérémy
  • Daniault Louis
  • Fsaifes Ihsan
  • Bellanger Séverine
  • Antier Marie
  • Bourderionnet Jérôme
  • Durand Eric
  • Simon-Boisson³ Christophe
  • Larat Christian
  • Lallier Eric
  • Brignon Arnaud
  • Chanteloup Jean-Christophe
  , 2018. For the last decade, Coherent Beam Combining (CBC) has proven to be a successful method for increasing the output peak and average powers of femtosecond fiber amplifiers [1]. Within the framework of the XCAN project, we aim at the demonstration of the scalability of such laser systems by coherently combining 61 fiber amplifiers. Therefore, we use a highly scalable approach relying on a tiled-aperture geometry along with an interferometric phase measurement and control which can theoretically handle the coherent combination of up to 10 000 beams [2]. After very promising results obtained with 19 passive fibers [3], we present the first results obtained using seven active fibers. Figure 1: (a) Experimentally obtained far field. (b) Combined beam with corresponding M²-values. (c) Measured temporal profile of the combined beam. (d) Corresponding spectrum. The seven beams are arranged in a hexagonal array in the near field, collimated by a microlens array, and the combined beam is found in the far field. Based on a characterization of our experimental fiber array, the maximum efficiency is calculated to be η = 0.56. By filtering the central lobe, we obtain an experimental efficiency of η = 0.48 (fig. 1a,1b), which corresponds to 86 % of the theoretical value stated above. The measured M² of 1.15 on each axis proves a good quality of the combined beam. Finally, the beam is temporally compressed to 244 fs with a time-bandwidth product of 0.55, close to the simulated Fourier transform limit of 0.48 (fig. 1c,1d). The average power of the output beam is measured to be 71 W, corresponding to a compression efficiency of 0.86. The next steps will include the reduction of the pulse repetition rate and the resulting increase in peak power. Finally, the number of beams will be increased to 61 and the spatial and spectral characteristics of the combined beam will be studied.
• Femtosecond coherent beam combining of seven fiber amplifiers in tiled-aperture configuration
  
  • Chanteloup Jean-Christophe
  • Le Dortz Jérémy
  • Simon-Boisson Christophe
  • Durand Eric
  • Heilmann Anke
  • Antier Marie
  • Bourderionnet Jérôme
  • Larat Christian
  • Fsaifes Ihsan
  • Daniault Louis
  • Bellanger Séverine
  • Lallier Eric
  • Brignon Arnaud
  , 2014, 20, pp.182 - 187.
• Ultrafast gating for the generation of optically synchronized OPCPA Pump pulses
  
  • Delen Xavier
  • Louis de Canonville Cyprien
  • Druon Frédéric
  • Georges Patrick
  • Papadopoulos Dimitrios
  , 2018.