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Propagation d'impulsions Térawatts femtosecondes dans l'atmosphère et applications.

Abstract : When ultrasshort and high-power laser pulses propagate across the atmosphere, self-guided filaments of 100 $\mu m$ radius are formed. They result from a balance between Kerr self-focusing and defocusing by the plasma generated by multiphoton ionisation.\\
During my thesis, we showed that the white light spectrum generated in filament spans from the the infrared (4,5 $\mu m$) to the ultraviolet (230 nm) to thanks to Third Harmonic Generation and self-phase modulation. We charaterized the propagation under different conditions (rain, smog, turbulence) to developp different atmospheric applications.
In particular, we demostrated multi-parameters LIDAR for relative humidity as well as atmospheric pollution remote sensing.\\
Furthermore, it is possible to detect and to identify biological aerosols or solid targets (LIBS) at remote distances, by non-linear processes induced {\it{in situ}} by the high intensity delivered by filaments.
Moreover, we demonstrated that guiding and triggering high-voltage discharge thanks to a femsecond high-powered pulse is possible even under a rain with an efficiency comparable to that observed in dry air. We also impoved the efficiency of a two pulses configurations (a femtosecond pulse and a subsequent nanosecond pulse). These results raise hope that lightning could be triggered and guided by laser pulses in the future.
Mots-clés : filaments LIBS LIDAR
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https://tel.archives-ouvertes.fr/tel-00011589
Contributor : Guillaume Méjean <>
Submitted on : Sunday, February 12, 2006 - 7:49:24 PM
Last modification on : Thursday, October 15, 2020 - 9:00:22 AM
Long-term archiving on: : Saturday, April 3, 2010 - 10:21:37 PM

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Guillaume Méjean. Propagation d'impulsions Térawatts femtosecondes dans l'atmosphère et applications.. Physique Atomique [physics.atom-ph]. Université Claude Bernard - Lyon I, 2005. Français. ⟨tel-00011589⟩

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