PhD defense of Farah AL-JAMMAL

Keywords  :  
High voltage, Dielectric barrier discharges (DBDs), Electric field measurement, Electrooptic (EO) measurement, Optical sensor, Helium plasma jet, Terahertz generation

Abstract :
Due to the wide range of applications of discharges and plasmas, their characterizations have been receiving a revival of interest these last couple of years. Among all the relevant characteristics of a plasma, the spatial distribution and the temporal evolution its associated electric field (E-field) is a subject of major interest and one of the more critical parameters to be analyzed.
Firstly, this thesis work concerns the non-invasive vector characterization of the electric field associated to cold plasmas (dielectric barrier discharge, atmospheric plasma jet,..). The other part is devoted to the nonlinear interaction between a cold plasma and an optical pulse wave for the parametric generation of Terahertz (THz) waves. In both cases (plasma generated with a high voltage source and plasma due to air breakdown), we have detected an electric field (of the order of MV/m for plasma analysis and of a few V/m for high frequency generation) either with a pigtailed electro-optical probe (developped at Kapteos), or by using an experimental free space EO bench (developped at IMEP LAHC).
We have carried out a complete polarimetric study of the E-field generated by electrodes or by ionization of a gas like helium. In particular, we have been interested in the
polarization behavior of the observed phenomena. We also studied the possibility to improve the efficiency of the THz generation by adding a helium plasma jet or the gas alone. We have performed a complete characterization of the generated THz signal (in modulus and orientation). The obtained results are perfectly described by a model that we have developed. This model has been experimentally validated by a polarimetric study of the THz pulse using an innovative EO detection.

Jury members :

• Mr. Laurent PECASTAING, Professorr, University of Pau : Reviewer
• Mr. Christophe VOLAT, Professor, University of Quebec : Reviewer
• Mrs Nadège BODIN-COURJAL, Associate professor, University of  Franche-Comte :  Examiner
• Mr. Gwenaël GABORIT, Associate professor (HDR), University of Savoie : Supervisor
• Mr. Maxime BERNIER, Associate professor, University of  Savoie : Co-supervisor
• Mr. Lionel DUVILLARET, Professor, Kapteos CEO : Guest
• Mr. Sylvain ISENI, Researcher CNRS, University of Orleans : Guest