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Contrôle et métrologie de la génération d'harmoniques sur miroir plasma

Abstract : When an ultra intense femtosecond laser with high contrast is focused on a solid target, the laser field at focus is sufficient enough to completely ionize the target surface during the rising edge of the laser pulse and form a plasma. This dense plasma entirely reflects the incident beam in the specular direction: this is a so-called plasma mirror. As the interaction between the laser and the plasma mirror is highly non-linear, it thus leads to the high harmonic generation (HHG) in the reflected beam. In the temporal domain, this harmonic spectrum is associated to a train of attosecond pulses.The aim of my PhD were to experimentally control this HHG and to measure the properties of the harmonics. We first studied the optimization of the harmonic signal, and then the spatial characterization of the harmonic beam in the far-field (harmonic divergence). These characterizations are not only important to develop an intense XUV/attosecond light source, but also to get a better understanding of the laser-matter interaction at very high intensity. We have thus been able to get crucial information of the electrons and ions dynamics of the plasma, showing that the harmonics can also be used as a diagnostic of the laser-plasma interaction.We then developed a new general approach for optically-controlled spatial structuring of overdense plasmas generated at the surface of initially plain solid targets. We demonstrate it experimentally by creating sinusoidal plasma gratings of adjustable spatial periodicity and depth, and study the interaction of these transient structures with an ultraintense laser pulse to establish their usability atrelativistically high intensities. We then show how these gratings can be used as a `spatial ruler' to determine the source size of the high-order harmonic beams produced at the surface of an overdense plasma. These results open new directions both for the metrology of laser-plasma interactions andthe emerging field of ultrahigh intensity plasmonics.
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https://tel.archives-ouvertes.fr/tel-01093180
Contributor : Sylvain Monchocé <>
Submitted on : Friday, January 16, 2015 - 2:59:32 PM
Last modification on : Friday, March 5, 2021 - 3:00:35 PM

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S. Monchocé. Contrôle et métrologie de la génération d'harmoniques sur miroir plasma. Physique [physics]. Université Paris Sud XI, 2014. Français. ⟨tel-01093180⟩

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