Clément EUSTACHE : "Bloch surface wave fiber sensors"

Abstract : The in-situ detection and analysis of small physical, chemical, or biological quantities in hard-to-reach environments is significantly impacting numerous scientific, medical, and industrial fields. Despite being a leading miniaturized solution for this challenge, the "Lab-on-tip" concepts, usually confined at the fiber core, face limitations in detection resolution. My thesis aims to explore a new generation of "Lab-on-tip" systems, based on a core-to-core optical interconnection at the fiber tip, either between various cores of an individual multicore fiber or two standard single-core fibers. This innovative approach leverages nano-optical platforms based on Bloch surface waves. Bloch surface waves are evanescent electromagnetic modes that propagate over millimeter distances on the top surface of a one-dimensional photonic crystal. These waves ensure core-to-core optical interconnection and the probing of their environment. The fiber modes and the Bloch surface waves are coupled by milling subwavelength diffraction gratings above each core, on top of the photonic crystal. We have developed three nano-optical platforms: two at the end of four-core fibers and another on the end-face of a ferrule combining two standard single-mode fibers. Our experiments demonstrated core-to-core coupling that can be controlled by the polarization of the incident light, enabling agile detection and demultiplexing functions. These platforms have been tested as refractometers for detecting volatile organic compounds, showcasing their potential as sensors. Our fiber-integrated architectures allows for light excitation and detection signals to travel through different channels within optical fibers, simplifying the detection process and optimizing signal-to-noise ratio. These fiber-integrated nano-optical platforms hold promise for a wide array of applications, including sensing, optical trapping and manipulation, and information processing.

Jury Composition :

• M. Antoine MOREAU, Maître de conférences, Université Clermont Auvergne, Reporter
• M. Yves JOURLIN, Professeur, Université de Saint-Étienne, Reporter
• Mme Aude L. LEREU, Directeur de recherche, Université d'Aix-Marseille, Reviewer
• M. Jean-Baptiste SANCHEZ, Professeur, Université de Bourgogne Franche-Comté, Reviewer
• M. Nicolas MARTIN, Professeur, Université de Bourgogne Franche-Comté, Reviewer
• M. Thierry GROSJEAN, Directeur de recherche, Université Bourgogne Franche-Comté, PhD Director

Localisation : Amphithéâtre Jean-Jacques Gagnepain Institut FEMTO-ST 15B Avenue des Montboucons 25000 BESANCON