Publications

2000

• Correction des phases spectrale et temporelle pour les lasers ultra-intenses.
  
  • Salmon Estelle
  , 2000. La production d'impulsions ultra-courtes et ultra-intenses présente un grand intérêt pour l'exploration de la physique de l'interaction laser-matière. Le développement ces dernières années d'oscillateurs engendrant des impulsions de plus en plus courtes combinées à une technique de l'amplification à dérive de fréquence a permis d'obtenir des puissances de quelques centaines de térawatts. La prochaine génération de chaîne de puissance devrait produire des impulsions ayant une puissance de l'ordre de la dizaine de pétawatts. Une telle chaîne pourrait s'implanter sur la Ligne d'Intégration Laser (LIL) au CESTA à Bordeaux. Le dimensionnement du laser PW en étude sur la LIL a montré la nécessité de corriger les phases spectrale et temporelle. L'objectif de la thèse est la correction de la phase spectrale en utilisant un modulateur de phase temporelle pour des impulsions de relativement faible largeur spectrale (quelques nanomètres) centrées autour de 1,053 µm et fortement étirées temporellement. La spécificité des impulsions a nécessité un travail particulier d'adaptation des méthodes de mesure absolue et de modulation de phase spectrale. La maîtrise de la phase spectrale des impulsions permet en effet non seulement la correction des défauts de phase pour comprimer les impulsions à dérive de fréquence mais aussi la mise en forme temporelle de ces impulsions. La mise en place de l'analogie entre les domaines temporel et spatial a permis de bénéficier de tout l'acquis du domaine spatial pour analyser la phase spectrale de l'impulsion. Nous avons aussi formalisé la correspondance de la modulation de la phase entre le domaine temporel et le domaine spectral pour des impulsions fortement étirées, en utilisant le théorème de la phase stationnaire. Nous présentons dans ce manuscrit les résultats expérimentaux de mesures de la phase spectrale et de la correction de la phase spectrale. Une extension à la correction de la phase temporelle est proposée : la correction des effets non linéaires directement dans le domaine temporel (en utilisant le modulateur de phase temporelle). Nous présentons les résultats des simulations numériques de la correction de la phase temporelle permettant d'améliorer les performances d'un facteur trois en puissance sur une installation du type LIL.
• ELP-OA: measuring the wavefront tilt without a natural guide star
  
  • Schöck Matthias
  • Pique Jean-Paul
  • Petit Alain D.
  • Chevrou Patrick
  • Michau Vincent
  • Grynberg Gilbert
  • Migus Arnold
  • Ageorges Nancy
  • Bellanger Véronique
  • Biraben François
  • Deron Ruy
  • Fews Hayden
  • Foy Francoise-Claude
  • Högemann Claudia K.
  • Laubscher Markus
  • Müller Daniel
  • d'Orgeville Céline
  • Peillet Olivier
  • Redfern Mike
  • Foy Renaud
  • Segonds Patricia
  • Soden Richard A. J.
  • Tallon Michel
  • Thiébaut Éric
  • Tokovinin Andrei
  • Vaillant Jérôme
  • Weulersse Jean-Marc
  Proceedings of SPIE, the International Society for Optical Engineering, SPIE, The International Society for Optical Engineering, 2000, 4125, pp.41-52. We describe the current status of the ELP-OA project in which we try to demonstrate in practice that it is possible to measure the tilt of a wave front using only a polychromatic laser guide star and no natural guide star. The first phase of ELP-OA, consisting of feasibility experiments, has recently been completed successfully. This paper provides an overview over the results of this first phase and over the continuation of the ELP-OA project. (10.1117/12.409304)
  DOI : 10.1117/12.409304
• Polychromatic guide star: feasibility study
  
  • Foy Renaud
  • Pique Jean-Paul
  • Petit Alain D.
  • Chevrou Patrick
  • Michau Vincent
  • Prigent Pascal
  • Grynberg Gilbert
  • Migus Arnold
  • Ageorges Nancy
  • Bellanger Veronique
  • Biraben Francois
  • Deron Ruy
  • Fews Hayden
  • Foy Francoise-Claude
  • Hoegemann Claudia
  • Jagourel Pascal
  • Laubscher Markus
  • Mueller Daniel
  • d'Orgeville Celine
  • Peillet Olivier
  • Redfern Mike
  • Schoeck Matthias
  • Segonds Patricia
  • Soden Richard
  • Tallon Michel
  • Tallon-Bosc Isabelle
  • Thiébaut Éric
  • Tokovinin Andrei A.
  • Vaillant Jerome
  • Weulersse Jean-Marc
  Proceedings of SPIE, the International Society for Optical Engineering, SPIE, The International Society for Optical Engineering, 2000, 4065, pp.312 - 323. Adaptive optics at astronomical telescopes aims at correcting in real time the phase corrugations of incoming wavefronts caused by the turbulent atmosphere, as early proposed by Babcock. Measuring the phase errors requires a bright source located within the isoplanatic patch of the program source. The probability that such a reference source exists is a function of the wavelength, of the required image quality (Strehl ratio), of the turbulence optical properties, and of the direction of the observation. It turns out that the sky coverage is disastrously low in particular in the visible wavelength range where, unfortunately, the gain in spatial resolution brought by adaptive optics is the largest. Foy and Labeyrie have proposed to overcome this difficulty by creating an artificial point source in the sky in the direction of the observation relying on the backscattered light due to a laser beam. This laser guide star (hereinafter referred to as LGS) can be bright enough to allow us to accurately measure the wavefront phase errors, except for two modes which are the piston (not relevant in this case) and the tilt. Pilkington has emphasized that the round trip time of the laser beam to the mesosphere, where the LGS is most often formed, is significantly shorter than the typical tilt coherence time; then the inverse-return-of-light principle causes deflections of the outgoing and the ingoing beams to cancel. The apparent direction of the LGS is independent of the tilt. Therefore the tilt cannot be measured only from the LGS. Until now, the way to overcome this difficulty has been to use a natural guide star to sense the tilt. Although the tilt is sensed through the entire telescope pupil, one cannot use a faint source because $APEX 90% of the variance of the phase error is in the tilt. Therefore, correcting the tilt requires a higher accuracy of the measurements than for higher orders of the wavefront. Hence current adaptive optics devices coupled with a LGS face low sky coverage. Several methods have been proposed to get a partial sky coverage for the tilt. The only one providing us with a full sky coverage is the polychromatic LGS (hereafter referred to as PLGS). We present here a progress report of the R&D; program Etoile Laser Polychromatique et Optique Adaptative (ELP-OA) carried out in France to develop the PLGS concept. After a short recall of the principles of the PLGS, we will review the goal of ELP-OA and the steps to get over to bring it into play. We finally shortly described the effort in Europe to develop the LGS.
• Ultrahigh-intensity laser-produced plasmas as a compact heavy ion injection source
  
  • Krushelnick K.
  • Clark E.L.
  • Allott R.
  • Beg F.N.
  • Danson C.N.
  • Machacek A.
  • Malka Victor
  • Najmudin Z.
  • Neely D.
  • Norreys P.A.
  • Salvati M.R.
  • Santala M.I.K.
  • Tatarakis M.
  • Watts I.
  • Zepf M.
  • Dangor A.E.
  IEEE Transactions on Plasma Science, Institute of Electrical and Electronics Engineers, 2000, 28 (4), pp.1110. (10.1109/27.893296)
  DOI : 10.1109/27.893296
• ELPOA: toward the tilt measurement from a polychromatic laser guide star
  
  • Foy Renaud
  • Pique J. P.
  • Petit Alain D.
  • Chevrou Patrick
  • Michau Vincent
  • Grynberg Gilbert
  • Migus Arnold
  • Ageorges Nancy
  • Bellanger Veronique
  • Biraben Francois
  • Deron Ruy
  • Fews Hayden
  • Foy Francoise-Claude
  • Hoegemann Claudia
  • Laubscher Markus
  • Mueller Daniel
  • d'Orgeville Celine
  • Peillet Olivier
  • Redfern Mike
  • Schoeck Matthias
  • Segonds Patricia
  • Soden Richard
  • Tallon Michel
  • Thiébaut Éric
  • Tokovinin Andrei A.
  • Vaillant Jerome
  • Weulersse Jean-Marc
  Proceedings of SPIE, the International Society for Optical Engineering, SPIE, The International Society for Optical Engineering, 2000, 4007, pp.284-295. Adaptive optics at astronomical telescopes aims at correcting in real time the phase corrugations of incoming wavefronts caused by the turbulent atmosphere, as early proposed by Babcock. Measuring the phase errors requires a bright source, which is located within the isoplanatic patch of the program source. The probability that such a reference source exists is a function of the wavelength of the observation, of the required image quality (Strehl ratio), of the turbulence optical properties, and of the direction of the observation. Several papers have addressed the problem of the sky coverage as a function of these parameters (see e.g.: Le Louarn et al). It turns out that the sky coverage is disastrously low in particular in the short (visible) wavelength range where, unfortunately, the gain in spatial resolution brought by adaptive optics is the largest. Foy and Labeyrie have proposed to overcome this difficulty by creating an artificial point source in the sky in the direction of the observation relying on the backscattered light due to a laser beam. This laser guide star (hereafter referred to as LGS) can be bright enough to allow us to accurately measure the wavefront phase errors, except for two modes which are the piston (which is not relevant in this case) and the tilt. Pilkington has emphasized that the round trip time of the laser beam to the mesosphere, where the LGS is most often formed, is significantly shorter than the typical tilt coherence time; then the inverse-return- of-light principle causes deflections of the outgoing and the ingoing beams to cancel. The apparent direction of the LGS is independent of the tilt. Therefore the tilt cannot be measured only from the LGS. Until now, the way to overcome this difficulty has been to use a natural guide star to sense the tilt. Although the tilt is sensed through the entire telescope pupil, one cannot use a faint source because approximately equals 90% of the variance of the phase error is in the tilt. Therefore, correcting the tilt requires a higher accuracy of the measurements than for higher orders of the wavefront. Hence current adaptive optics devices coupled with a LGS face low sky coverage. Several methods have been proposed to get a partial or total sky coverage for the tilt, such as the dual adaptive optics concept, the elongation perspective method, or the polychromatic LGS (hereafter referred to as PLGS). We present here a progress report of the R&D; program Etoile Laser Polychromatique et Optique Adaptative (ELP-OA) carried out in France to develop the PLGS concept. After a short recall of the principles of the PLGS, we will review the goal of ELP-OA and the steps to get over to bring it into play. (10.1117/12.390401)
  DOI : 10.1117/12.390401
• Spectral line shapes using the dicenter approach for dense, hot plasmas: hydrogen and helium-like lines
  
  • Sauvan P
  • Leboucher-Dalimier E
  • Angelo P
  • Derfoul H
  • Ceccotti T
  • Poquerusse A
  • Calisti Annette
  • Talin B
  Journal of Quantitative Spectroscopy and Radiative Transfer, Elsevier, 2000, 65 (1-3), pp.511-525. This paper reports on the spectral line shape of hydrogen and helium-like lines relevant to the quasi-static dicenter model. This treatment is justified for hot dense, moderate Z plasmas. The code IDEFIX developed for the quasi-static dicenter model involves a self-consistent description of the interactions and of the radiative properties. Strong dependence of the transition energies and of the dipole moments on the interionic separation are pointed out and novel density-dependent spectroscopic features such as asymmetries, satellite-like features, molecular transitions are exhibited. The theoretical spectra presented here are discussed in connection with experimental results where these exist. (C) 2000 Published by Elsevier Science Ltd. All rights reserved. (10.1016/S0022-4073(99)00093-X)
  DOI : 10.1016/S0022-4073(99)00093-X
• Etude expérimentale de la propagation et du dépôt d'énergie d'électrons rapides dans une cible solide ou comprimée par choc laser: application à l'allumeur rapide.
  
  • Pisani Francesca
  , 2000. Dans le schéma de l'allumeur rapide, dernière avancée dans le domaine de la fusion par confinement inertiel, on envisage de découpler la phase de compression de la phase de chauffage du combustible nucléaire. Cette dernière serait atteinte à l'aide d'une source extérieure constituée par un faisceau d'électrons très énergétiques créé avec un laser ultra-intense. L'étude des mécanismes de transfert d'énergie de ces électrons au combustible comprimé représente le but principal de ce travail de thèse. Nous nous proposons en particulier de mettre en évidence et d'étudier le rôle joué par les effets électriques et collisionnels de la propagation du faisceau d'électrons rapides dans un milieu aux propriétés proches du combustible comprimé. Nous avons pour cela effectué deux campagnes d'expériences, l'une avec l'installation laser VULCAN du RAL (Angleterre) et l'autre sur la nouvelle installation laser 100 TW du laboratoire LULI (France). Lors de la première expérience, nous avons obtenu les premiers résultats sur la propagation d'électrons rapides dans un matériau dense et chaud. Le caractère novateur de ce travail expérimental tient en particulier à l'utilisation de la technique de génération de hautes pressions par choc laser, ce qui a permis la création d'un plasma fortement corrélé et dégénéré. Le rôle des effets électriques et magnétiques, liés à la charge d'espace créée par le faisceau d'électrons rapides, a été approfondi lors de la deuxième campagne d'expérience, au cours de laquelle nous avons étudié la propagation des électrons dans des matériaux ayant des caractéristiques électriques différentes (isolant ou conducteur). L'analyse des résultats montre que seule la prise en compte simultanée des deux mécanismes de la propagation (collisionnels et électriques) permet un traitement correct et complet du dépôt d'énergie. La nécessité de prendre en compte les modifications apportées à la matière par le passage même des électrons, et notamment le chauffage induit, a été également mise en évidence.
• Experimental evidence of the effect of heat flux on Thomson scattering off ion acoustic waves
  
  • Amiranoff François
  • Baton S. D.
  • Hüller S.
  • Malka Victor
  • Modena A.
  • Mounaix Ph.
  • Galloudec N. Renard-Le
  • Rousseaux C.
  • Salvati M.
  Physical Review E : Statistical, Nonlinear, and Soft Matter Physics [2001-2015], American Physical Society, 2000, 61 (2), pp.1949. Thomson self-scattering measurements are performed in a preionized helium gas jet plasma at different locations along the laser propagation direction. A systematic and important variation of the intensity ratio between the blue and the red ion spectral components is observed, depending on whether the location of the probed region is in front of or behind the focal plane. A simple theoretical calculation of Thomson scattering shows that this behavior can be qualitatively understood in terms of a deformation of the electron distribution function due to the return current correlated with the classical thermal heat flux (10.1103/PhysRevE.61.1949)
  DOI : 10.1103/PhysRevE.61.1949
• Interaction of an ultra-intense laser pulse with a nonuniform preformed plasma
  
  • Faure Jérôme
  • Malka Victor
  • Marquès J.-R.
  • Amiranoff François
  • Courtois Christian
  • Najmudin Z.
  • Krushelnick K.
  • Salvati M.
  • Dangor A. E.
  • Solodov A.
  • Mora P.
  • Adam J.-C.
  • Héron A.
  Physics of Plasmas, American Institute of Physics, 2000, 7 (7), pp.3009. The propagation of an ultra-intense laser pulse in a preformed plasma channel was investigated experimentally. Different regimes of propagation were observed when the pulse duration was varied. For a long pulse and powers lower than the critical power for self-focusing,PL/PC<1 (I0=2×1017W/cm2), the laser pulse was guided by the preformed plasma channel over three Rayleigh lengths (4 mm) and a longitudinal plasma wave was generated by envelope self-modulation of the pulse. For a short pulse and PL/PC≫1, the interaction was dominated by self-focusing and Raman instabilities. Numerical simulations were run for the latter case, giving results comparable to the experiment. The simulations were also used to investigate the dynamics of the instabilities at high power. They showed that strong Raman side scattering first occurs at the beginning of the interaction and is then followed by self-focusing and envelope self-modulation. (10.1063/1.874153)
  DOI : 10.1063/1.874153
• Strong self-focusing in quasi-stationary laser plasmas
  
  • Malka Victor
  • Galloudec N. Renard-Le
  • Hüller S.
  • Pesme D.
  • Amiranoff François
  • Baton S. D.
  • Modena A.
  • Mounaix Ph.
  • Rousseaux C.
  • Salvati M.
  Physics of Plasmas, American Institute of Physics, 2000, 7 (10), pp.4259. Collective Thomson scattering imaging has been used to study the propagation and self-focusing processes taking place during the interaction of a nanosecond laser beam with a preionized gas-jet plasma. The experiments have been carried out with a laser beam power PL exceeding greatly the critical power for ponderomotive self-focusingPc. It has been found that the position of the ion acoustic waves excited by stimulated Brillouin scattering depends only weakly on the initial focal position of the interactionlaser beam. These results, together with theoretical and numerical modeling, demonstrate that in such a regime (PL/Pc≫1)self-focusing is the dominant mechanism governing the localization of the interaction processes. (10.1063/1.1290594)
  DOI : 10.1063/1.1290594
• Arbitrary dispersion control of ultrashort optical pulses using acoustic waves
  
  • Verluise Frédéric
  • Laude Vincent
  • Huignard Jean-Pierre
  • Tournois Pierre
  • Migus Arnold
  Journal of the Optical Society of America B, Optical Society of America, 2000, 17, pp.138-145.
• Interaction of ultraintense laser pulses with an underdense, preformed plasma channel
  
  • Malka Victor
  • Faure Jérôme
  • Marques J.R.
  • Amiranoff François
  • Courtois Christian
  • Najmudin Z.
  • Krushelnick K.
  • Salvati M.R.
  • Dangor A.E.
  IEEE Transactions on Plasma Science, Institute of Electrical and Electronics Engineers, 2000, 28 (4), pp.1078. We report on experimental results regarding the propagation of ultraintense laser pulses in a preformed plasma channel. In this experiment, the long (4-mm) fully ionized plasma channel created by the amplified spontaneous emission (ASE) was measured by interferometry before and after the propagation of the short laser pulse. Forward spectra show a cascade of Raman satellites, which merge with one another when the laser power was increased up to critical power for relativistic self-focusing Pc. The number of filaments measured by interferometry increases when the laser power increases. High conversion efficiency (≈10%) of second harmonic generation was observed in the interaction (10.1109/27.893292)
  DOI : 10.1109/27.893292
• Ultrafast laser-based thermal X-ray sources
  
  • Kieffer J. C.
  • Chien C. Y.
  • Dorchies F.
  • Forget Philippe
  • Gallant P.
  • Jiang Z. M.
  • Pépin H.
  Comptes Rendus de l'Academie des Sciences. Série IV, Physique, Astronomie, Elsevier, 2000, 1 (3), pp.297-303. no abstract
• Extending plasma accelerators: Guiding with capillary tubes
  
  • Cros B.
  • Courtois Cédric
  • Malka G.
  • Matthieussent G.
  • Marques J. R.
  • Dorchies F.
  • Amiranoff François
  • Rebibo S.
  • Hamoniaux G.
  • Blanchot N.
  • Miquel J. L.
  IEEE Transactions on Plasma Science, Institute of Electrical and Electronics Engineers, 2000, 28 (4), pp.1071-1077. no abstract
• Diagnosis of peak laser intensity from high-energy ion measurements during intense laser interactions with underdense plasmas
  
  • Krushelnick K.
  • Clark E.
  • Najmudin Z.
  • Salvati M.
  • Santala M.I.K.
  • Tatarakis M.
  • Dangor A.E.
  • Malka Victor
  • Neely D.
  • Allott R.
  • Danson C.
  Laser and Particle Beams, Cambridge University Press (CUP), 2000, 18 (4), pp.595. Experiments were performed using high-power laser pulses (greater than 50 TW) focused into underdense helium, neon, or deuterium plasmas (ne [less-than-or-equal] 5 × 1019 cm−3). Ions having energies greater than 300 keV were measured to be produced primarily at 90° to the axis of laser propagation. Ion energies greater than 6 MeV were recorded from interactions with neon. Spatially resolved pinhole images of the ion emission were also obtained and were used to estimate the intensity of the focused radiation in the interaction region. (10.1017/S0263034600184034)
  DOI : 10.1017/S0263034600184034
• Characterization of neutral density profile in a wide range of pressure of cylindrical pulsed gas jets
  
  • Malka Victor
  • Coulaud C.
  • Geindre J. P.
  • Lopez V.
  • Najmudin Z.
  • Neely D.
  • Amiranoff François
  Review of Scientific Instruments, American Institute of Physics, 2000, 71 (6), pp.2329. The neutral density profile of cylindrical gas jets is measured with a Mach–Zehnder interferometer under a wide range of backing pressures. The sensitivity of this diagnostic together with the mathematical treatment of the data allows us to measure neutral densities for argon gas as low as 1017cm−3 for a 5 mm diam gas jet. (10.1063/1.1150619)
  DOI : 10.1063/1.1150619
• Characterization of a subpicosecond x-ray streak camera for ultrashort laser-produced plasmas experiments
  
  • Gallant P.
  • Forget Philippe
  • Dorchies F.
  • Jiang Z.
  • Kieffer J. C.
  • Jaanimagi P. A.
  • Rebuffie J. C.
  • Goulmy C.
  • Pelletier J. F.
  • Sutton M.
  Review of Scientific Instruments, American Institute of Physics, 2000, 71 (10), pp.3627-3633. no abstract
• Investigation of a channeling high-intensity laser beam in underdense plasmas
  
  • Najmudin Z.
  • Dangor A.E.
  • Modena A.
  • Salvati M.R.
  • Clayton C.E.
  • Danson C.N.
  • Gordon D.
  • Joshi C.J.
  • Marsh K.A.
  • Malka Victor
  • Muggli P.
  • Neely D.
  • Walsh F.N.
  IEEE Transactions on Plasma Science, Institute of Electrical and Electronics Engineers, 2000, 28 (4), pp.1057. The interaction of an intense short pulse laser (>5×10 18 Wcm-2) with underdense plasma was extensively studied. The beam is found to be highly susceptible to the forward Raman scattering instability. At sufficiently high growth rates, this can lead to wavebreaking with the resultant production of a high flux of accelerated electrons (>1011 for E>2 MeV). Some electrons are found to be accelerated well above the dephasing energy, up to 94 MeV. Self-scattered images intimate the presence of high-intensity channels that extend more than 3.5 mm or 12 Rayleigh lengths. These filaments do not follow the axis of laser propagation, but are seen to be emitted within an f4 cone centered around this axis. Spectra of the self-scattered light show that the main contribution of the scattering is not from light captured within these filaments. But there is evidence for self-phase modulation from effects such as ionization and relativistic self-focusing. However, no clear correlation is observed between channel length and the number or energies of accelerated electrons. Evidence for high intensities within the channels is given by small-angle Thomson scattering of the plasma wave generated therein, with this method, the intensity is found to be of the order of 1018 Wcm-2 greater than 12 Rayleigh lengths from focus (10.1109/27.893290)
  DOI : 10.1109/27.893290
• Spectroscopy of solid density plasmas generated by irradiation of thin foils by a fs laser
  
  • Gallant P.
  • Jiang Z.
  • Chien C. Y.
  • Forget Philippe
  • Dorchies F.
  • Kieffer J. C.
  • Pépin H.
  • Peyrusse O.
  • Mourou G.
  • Krol A.
  Journal of Quantitative Spectroscopy and Radiative Transfer, Elsevier, 2000, 65 (1-3), pp.243-252. no abstract