Ali NOUHO ALI "Sub-wavelength electromagnetic confinement and coupling between photonic nano-structures. Calculation of optical forces and torques.

Ali NOUHO ALI Phd Works : "Sub-wavelength electromagnetic confinement and coupling between photonic nano-structures. Calculation of optical forces and torques"

Résumé : This thesis work is a contribution to the numerical modeling of new optical devices based on photonic nano-structures such as photonic crystals, plasmonic nano-antennas or enhanced-transmission metamaterials. The objective is to enhance the light confinement in these structures to further use it as a source of trapping to manipulate resonant or non-resonant metallo-dielectric particles.
The first part is devoted to the modeling of the local electrostatic field generated by the application of a DC voltage across two electrodes, on a nano-structured dielectric acting as an active material in electro-optical modulators. The idea is to enhance the local electrostatic and optical fields in the material to induce a more substantial modification of its local index, thus leading to an amplification of its nonlinear effects. In particular, we have shown that by optimizing the geometrical shape of the electrodes, the local electrostatic field can be further exalted inside the material leading to exacerbate the electro-optical effect by a factor 6.
The second part concerns the modeling of optical forces and moments acting in nanostructures by the Finite Difference Time Domain Method (FDTD). After presenting the principle of modeling of the optical forces and torques, a specific application is considered to study the translational and rotational motions of a dielectric disk placed at the output side of a quarter-wave plate made of metamaterial formed of coaxial apertures with elliptical section engraved in an opaque metal film. On the other hand, we show how an optical tweezer based on Diabolo nano-antennas can be used to sort and arrange dielectric nanoparticles according to their size by tuning the wavelength of the incident beam.
The third and last part is dedicated to the study of optical trapping of metallo-dielectric nano-particles and the coupling between different optical nano-resonators according to the distance separating them and according to their natures. A detailed study is presented to analyze and understand the properties (scattering, absorption, extinction,) of these nano-resonators at the sub-wavelength scale. An application has been processed on the trapping of dielectric nano-particles by an optical nano-tweezers based on a photonic crystal coupled to a Bowtie nano-antenna.

Jury Composition :

Fadi BAIDA, Professeur des Universités, Université Bourgogne - Franche-Comté, Directeur de thèse

Taha BENYATTOU, Directeur de Recherche, Institut des Nanotechnologies de Lyon (INL), Rapporteur

Nordin FELIDJ, Professeur, Univeristé PARIS DIDEROT, Examinateur

Maria-Pilar BERNAL, Directeur de Recherche, FEMTO-ST, Examinateur

Abdoulkader IBRAHIM IDRISS, Maître de Conférences, Université de Djibouti,  CoDirecteur de thèse

Abderrahmane BELKHIR, Professeur, Université de Tizi-Ouzou (Algérie), Rapporteur

Localization : Salle des actes de l'UFR ST - UFR Sciences et Techniques, 16, route de Gray, 25000 BESANCON