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Theses

Développement et caractérisation des lasers XUV
créés par laser femtoseconde

Abstract : Coherent soft x-ray sources have an important potential for scientific, medical and industrial applications. The development of high intensity laser systems allowed the realization of new coherent and fast soft x-ray sources like high order harmonic generation and soft x-ray lasers. These sources are compact, cheaper than traditional sources such as synchrotrons, and are thus interesting.

This thesis presents the study of a new soft x-ray laser pumped by a femtoseconde laser beam working at 10 Hz. The circularly polarized ultra intense laser is longitudinally focused in a cell filled with xenon or krypton, to obtain the amplification of two lasing lines at 41.8 nm and 32.8 nm in Pd-like xenon and Ni-like krypton respectively. We carry out an experimental and numerical study of the source to understand the importance of different parameters such as the laser intensity and polarization, the gas pressure and the cell length. We have also spatially and temporally characterized the soft x-ray laser beam. To compensate the refraction of the driving laser we have investigated guiding techniques consisting in creating a plasma channel by electric discharge or using the multiple reflections of the driving laser on the internal walls of the dielectric tubes of sapphire or glass. A spectacular improvement of the source performances has been observed in both cases.

Finally, we present a preliminary study on a different x-ray scheme: the innershell photo pumping of neutral atoms. We have developed an optical system, which should create the appropriate conditions for the realisation of short wavelength x-ray amplifier.
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Contributor : Islam Bettaibi <>
Submitted on : Monday, October 15, 2007 - 12:03:18 PM
Last modification on : Wednesday, July 3, 2019 - 10:48:02 AM
Long-term archiving on: : Monday, September 24, 2012 - 1:25:21 PM

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Islam Bettaibi. Développement et caractérisation des lasers XUV
créés par laser femtoseconde. Physique Atomique [physics.atom-ph]. Ecole Polytechnique X, 2005. Français. ⟨tel-00179321⟩

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