Amar Nath Ghosh : "Design, modelling, and experiments of mid-infrared supercontinuum generation in soft-glass photonic crystal fibers"

Travaux de thèse d'Amar Nath Ghosh : "Design, modelling, and experiments of mid-infrared supercontinuum generation in soft-glass photonic crystal fibers"

Abstract : This doctoral thesis, funded within the framework of a European Marie-Curie H2020 SUPUVIR project, focuses on the design and fabrication of new photonic crystal fibers from infrared soft glasses making it possible to produce a wide emission spectrum in the mid-infrared (IR) wavelength region through generation of supercontinuum (SC). Applications of mid-IR SC sources cover infrared spectroscopy, optical detection of chemical and molecular species, materials processing, and biomedical imaging. An alternative to conventional thermal light sources, mid-IR sources have broad spectral bandwidth like a lamp or Globar and high brightness, which is more than 20 times of the sun focussed in a small spot similar to a laser. Several optical fibers with different photonic structures and different soft glasses have been produced and studied. In collaboration with the Institute of Electronic Materials Technology in Warsaw, heavy metal-oxide glass (PBG81) microstructured fibers were first developed and with these fibers we demonstrated the efficient generation of SC from 0.89 to 2.5 µm, limited by the absorption of the glass. Then, in partnership with the University of Rennes and the Technical University of Denmark, we fabricated microstructured fibers based on chalcogenide glasses (As38Se62) with polarization-maintaining property. These fibers have made it possible to generate a linearly polarized 3.1 to 6 µm supercontinuum. SC bandwidth was further extended between 1 µm and 7.4 µm in taper fibers produced from Ge10As22Se68 glass. The laser power handling capacities of these chalcogenide fibers were also analyzed. Finally, we have developed a compact mid-IR SC system using a fiber cascade comprising of silica, fluoride, and chalcogenide fiber, pumped by a fiber laser at 1.55 µm, and making it possible to extend the emission range from 2 to 10 µm. This research work thus constitutes an important step towards the development of stable and compact fiber SC sources for various applications in the mid-infrared.

Jury composition :

Marc Hanna: Chargé de recherche, CNRS, Laboratoire Charles Fabry, Institut d’optique, Paris
Camille-Sophie Brés: Associate Professor, EPFL, Lausanne
Ryszard Buczynski: Professor, University of Warsaw, Poland
Johann Troles: Professor, University of Rennes 1, Institut des Sciences chimiques de Rennes, Rennes
Thibaut Sylvestre: Directeur de recherche, CNRS, Institut FEMTO-ST, Université de Bourgogne Franche-Comté
Maxime Jacquot: Professeur, Institut FEMTO-ST, Université de Bourgogne Franche-Comté
John Dudley: Professeur, Institut FEMTO-ST, Université de Bourgogne Franche-Comté

Localization : 15B Avenue des Montboucons 25000 BESANCON - Meeting room 007