PhD Defense of Mr. Thomas BUNEL

BUNEL Thomas, PhLAM Laboratory- UMR8523 - Team Photonic

Titre: Optical frequency comb generation in fiber Fabry-Perot resonators

Jury: A. MUSSOT (PhLAM, supervisor), M. CONFORTI (PhLAM, supervisor), D. MARRIS-MORINI (Paris Saclay, referee), J. FATOME (Université de Bourgogne,  Referee), F. LEO (Université Libre de Bruxelles, member), A. PASQUAZI (Loughborough University UK, member), T. HERR (Universität Hamburg, Allemagne, membre), V. TORRES-COMPANY (Chalmers University of Technology, Suède, member)

Abstract:

This thesis investigates techniques for generating optical frequency combs using fiber Fabry-Perot resonators. An optical frequency comb, composed of discrete and equally spaced lines in the frequency domain, corresponds to a stable pulse train in the time domain. These combs have revolutionized advanced metrology and enabled ultra-precise optical clocks, but generating these signals remains challenging. In the 2010s, a method emerged using continuous-wave lasers to pump passive cavities, leveraging their nonlinear properties to generate other frequencies and frequency combs. Microresonators and fiber ring cavities have been predominantly used. Here, we explore this generation process with Fabry-Perot cavities, made of an optical fiber between two mirrors. These devices, at the intersection of microresonators and fiber ring cavities, are compact and easily integrable into optical systems using standard FC/PC connectors. The study of their nonlinear dynamics, allow the generation of broad and stable combs spanning over 30 THz, with more than 48,000 lines and phase noise below -110 dBc/Hz at 1 kHz. Additionally, fiber-optic telecom technologies enabling spatial multiplexing of light, open the door to multi-comb sources for advanced spectroscopy and imaging applications.