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Univ. Paris-Saclay
Laser-matter interaction

IRAMIS's research activities on laser-matter interaction concern both physical and chemical matters. Research programs range from simple atomic and molecular systems, to complex molecular and biomolecular systems, up to solids and plasmas.

IRAMIS is an important player in the "laser Pole" of the University Paris Saclay: it coordinates the ATTOLAB facility, aimed at interdisciplinary study of ultrafast dynamics at femtosecond and attosecond time scales, in systems vapor, condensed matter and plasma. It also hosts the Interdisciplinary Center for Extreme Light (Equipex CILEX, including the APOLLO 10 PW laser), for the study of material behavior in the unexplored ultra-relativistic interaction regime.

 
#2514 - Màj : 10/10/2018
 

While the pulse durations of infrared lasers are reaching the fundamental limitation imposed by the duration of the optical cycle (a few femtoseconds), High-order Harmonic Generation has recently opened a new field by accessing the attosecond regime (1as = 10-18 s).

HHG spectra are made of lines corresponding to the odd multiples of the fundamental laser frequency, and can cover a very broad spectral range, from visible light to soft X-rays. If these harmonics are phase locked, then the corresponding temporal profile is a train of attosecond pulses separated by half the laser period, whose duration decreases as the number of combined harmonics increases. The first experimental demonstration of attosecond pulses was performed in 2001 by the attophysics group in collaboration with the Laboratoire d’Optique Appliquée (Palaiseau) and FOM institute (The Netherlands) using the RABBITT technique [1]. We measured a train of 250 as pulses, corresponding to the superposition of five consecutive harmonics. In 2003 we extended this study by measuring the relative phases of the high harmonics over a broad spectral range [2]. This uncovered for the first time the presence of an intrinsic chirp of the attosecond emission.

Currently our activity is aiming at further developing these attosecond sources and at exploring the new physics they make accessible (see below). In-house theoretical studies provide support on these topics, using and developing 3D propagation codes in combination with Strong Field Approximation microscopic response. Further support is provided through external collaborations with theoretical groups in, e.g. Paris (LCPMR), or Madrid (UAM). 

[1] P.-M. Paul et al., Observation of a train of attosecond pulses from high harmonic generation, Science, 292, 1689 (2001).
[2] Y. Mairesse et al.  Attosecond synchronization of high-harmonic soft X-rays, Science, 302, 1540 (2003)

Au LIDYL, les simulations numériques permettent de modéliser l'interaction de la lumière avec la matière en particulier sous l'effet d'impulsions laser de très haute intensité et extrêmement brèves (domaine attoseconde (10-18 s). Les simulations de plasma denses ou dilués, en particulier à la surface d'un solide, ou encore l'interaction de plusieurs impulsions successives (miroir plasma) demandent des réaliser des calculs intensifs ultrapuissants, sur des machines pouvant effectuer des milliards de calculs par seconde.

Cette thématique couvre les activités suivantes au sein du LIDYL :

  • Calcul exascale
  • Développement algorithmique et modélisation
  • Frugalité numérique
  • Intelligence artificielle

La matière sous toutes ses formes est quantifiée. Atomes, molécules des molécules simples aux macromolécules biologiques, présentent des spectres lumineux caractéristiques, en absorption ou en émission, que l'on peut identifier par spectroscopie. Les sources lasers et plus particulièrement les sources impulsionnelles permettent aujourd'hui de nouveaux développements de tous les types de spectroscopies.

C'est par ces techniques que plusieurs équipes du LIDYL abordent des sujets de recherche très actuels :

  • Caractérisation de produits de fission
  • Dosimétrie par fluorescence
  • Nouvelles approches pour la radiothérapie (Radiothérapie 2.0)
  • Physico-chimie multi-échelle de la radiolyse

 

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