Doumy, Gilles (2006) Laser-matter interaction at high intensity and high temporal contrast. PhD thesis Service Photons, Atomes et Molécules, CEA SACLAY, Service Photons, Atomes et Molécules, CEA SACLAY, EP/X p.211.

Alternative Locations: http://www.imprimerie.polytechnique.fr/Theses/Files/Doumy.pdf

Abstract

The continuous progress in the development of laser installations has already lead to ultra-short pulses capable of achieving very high focalized intensities (I
1018 W/cm²). At these intensities, matter presents new non-linear behaviours, due to the fact that the electrons are accelerated to relativistic speeds. The experimental access to this interaction regime on solid targets has long been forbidden because of the presence, alongside the femtoseconde pulse, of a pedestal (mainly due to the amplified spontaneous emission (ASE) which occurs in the laser chain) intense enough to modify the state of the target.
In this thesis, we first characterized, both experimentally and theoretically, a device which allows an improvement of the temporal contrast of the pulse: the Plasma Mirror. It consists in adjusting the focusing of the pulse on a dielectric target, so that the pedestal is mainly transmitted, while the main pulse is reflected by the overcritical plasma that it forms at the surface. The implementation of such a device on the UHI 10 laser facility (CEA Saclay – 10 TW – 60 fs) then allowed us to study the interaction between ultra-intense, high contrast pulses with solid targets.
In a first part, we managed to generate and characterize dense plasmas resulting directly from the interaction between the main pulse and very thin foils (100 nm). This characterization was realized by using an XUV source obtained by high order harmonics generation in a rare gas jet.
In a second part, we studied experimentally the phenomenon of high order harmonics generation on solid targets, which is still badly understood, but could potentially lead to a new kind of energetic ultra-short XUV sources.

Table of content

Introduction 9
Bibliographie - 16
1 Le Miroir Plasma, étude et implémentation 17
1.1 Introduction - 17
1.2 Etude de l’effet Miroir Plasma - 21
1.2.1 Description des expériences - 22
1.2.2 Performances du Miroir Plasma - 27
1.2.3 Etude théorique du Miroir Plasma - 38
1.3 Mise en place du dispositif - 56
1.3.1 Discussion sur la mise en place d’un Système Miroir Plasma 60
1.3.2 Installation sur UHI 10 - 63
Bibliographie - 68
2 Diagnostics de plasmas denses 71
2.1 Motivations - 71
2.2 Sondage XUV de plasmas denses - 78
2.2.1 Génération d’harmoniques dans les gaz - 78
2.2.2 Une expérience pionnière - 81
2.3 Expériences sur UHI 10 - 86
2.3.1 Cibles utilisées - 86
2.3.2 Expériences sans Miroir Plasma - 87
2.3.3 Expériences avec Miroir Plasma - 93
2.3.4 Modélisation - Exploitation - 100
2.4 Conclusion - 104
Bibliographie - 106
3 Génération d’harmoniques sur cible solide 111
3.1 Motivations - 111
3.2 Inventaire historique - Etat de l’art - 113
3.3 Modèles théoriques de génération - 115
3.3.1 Miroir oscillant relativiste - 115
3.3.2 Emission par oscillations plasmas électroniques - 122
3.4 Génération d’harmoniques sur UHI 10 - 125
3.4.1 Dispositif expérimental - 125
3.4.2 Résultats - 131
3.4.3 Caractérisation de la source - 136
3.5 Discussion - 140
3.5.1 Interprétation des résultats expérimentaux - 140
3.5.2 Perspectives d’utilisation de la source XUV - 141
Bibliographie - 143
Conclusion 147
A Le contraste temporel 149
A.1 Mesure du contraste temporel - 149
A.2 Sources du piédestal - 151
A.3 Solutions pour l’amélioration du contraste - 153
A.3.1 Injection d’impulsions plus intenses - 154
A.3.2 Cellules de Pockels rapides - 155
A.3.3 Un nouveau type d’amplificateur: l’OPCPA - 155
A.3.4 Le concept ’Double CPA’ - 157
A.3.5 Les méthodes sur faisceau recomprimé - 160
A.4 Conclusion provisoire - 161
Bibliographie - 161
B collisions coulombiennes 163
Bibliographie - 166
C Résolution de l’équation d’Helmholtz 167
D Publications 171
Liste des figures 196
Bibliographie 201

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