Youssef GHANDAOUI PhD defense

Glasses and Ceramics - (V&C) team

Abstract
The development of safe and sustainable materials for photonic integration has motivated the exploration of arsenic-free chalcogenide glasses as alternatives to conventional As-based systems. In this work, Ge-Bi-S, Ge-Bi-Sb-S, and Ge-Bi-Se compositions were investigated at various levels, such as bulks syntheses, thin films integrations and waveguides fabrications. Bulk sulfide glasses of different compositions were synthesized by melt-quenching and characterized using structural (XRD, neutron diffraction, EXAFS), thermal, and optical analyses, revealing tunable bandgaps, refractive indices, and nonlinear coefficients directly linked to composition and local bonding environments.
RF co-sputtering was used to fabricate thin films, which served for ridge waveguides processing, through optimized nanofabrication processes, where systematic studies of etching, sidewall roughness, and scattering losses were studied in detail. Optical characterizations revealed broadband infrared transparency and strong Kerr nonlinearities, while density highlighted their potential for efficient Brillouin interactions. A key milestone of this research is the first on-chip observation of stimulated Brillouin scattering in arsenic-free Ge-Sb-Se waveguides, thus confirming the use of arsenic-free materials for nonlinear photonics. Serving as a coherent framework for environmentally responsible chalcogenide platforms, this research combines materials chemistry, advanced characterization, and integrated photonics toward compact, efficient, durable devices for near- and mid-infrared application.
Jury
Julien Lumeau, Directeur de Recherche CNRS, Institut Fresnel, Aix-Marseille Université / Reporter
Sébastien Cueff, Chargé de Recherche CNRS, INL, Université de Lyon / Reporter
Véronique Bardinal, Directrice de Recherches, CNRS, LAAS, Université de Toulouse / Examiner
Angéline Poulon, Maitresse de conférences, ICMCB, Université de Bordeaux / Examiner
Virginie Nazabal, Directrice de Recherche CNRS, ISCR, Université de Rennes / Supervisor
Joël Charrier, Professeur des Universités, Institut Foton, Université de Rennes / Co-supervisor
Lucas Deniel, Maitre de conférences, Institut Foton, Université de Rennes / Co-supervisor
Invited
Mehdi Alouini, Professeur des Universités, Institut Foton - IETR, Université de Rennes / invited
Stanislav Pechev, Ingénieur de Recherches, CNRS, ICMCB, Université de Bordeaux / invited

Contacts
Virginie Nazabal, virginie.nazabal@univ-rennes.fr
Joël Charrier, joel.charrier@univ-rennes.fr
Lucas Deniel, lucas.deniel@univ-rennes.fr
Youssef Ghandaoui, youssef.ghandaoui@univ-rennes.fr