Contribution to the development of rare-earth ion-doped silica-based optical fibers

Far from simply guiding light, optical fibers are extremely versatile. Equipped with passive functions such as spectral filtering, they form the basis of a wide range of stress sensors (temperature, pressure, strain, etc.). Doped with rare-earth ions, they acquire luminescent properties that are used in amplifiers and lasers. Among the materials used to silica is the reference glass. Silica-based fibers offer excellent mechanical properties, a high transparency and can be produced on a large scale. However, there are certain characteristics (phonon energy, solubility, etc.) of this glass which can be detrimental to the optical properties of rare earth ions. Since taking up my position as CR2 CNRS in 2002 at LPMC (Nice), my research activities have focused on the design, manufacture and characterization of silica-based optical fibers. In particular, I'm interested in the spectroscopic properties of rare-earth ions. The first project presented concerns the efficiency of emissions from the ³H₄ level of Tm³⁺. This is practically zero, due to the high energy of silica phonons. A material and spectroscopic study, and the implementation of numerical simulations have made these fibers compatible with amplifier applications at around 1.47 μm (for telecommunications S-band) and lasers around 810 nm (telecommunications, medical, etc.). Another project aims to overcome the limitations of silica by encapsulating rare-earth ions in nano-sized particles. An original approach to synthesizing these nanoparticles is proposed, based on phase separation mechanisms that take advantage of the heat treatments applied during the standard manufacturing process for optical fiber preforms (MCVD). This work and the others presented in this manuscript have been carried out within the framework of national and international collaborations. They have also been numerous internships for bachelor's, master's, doctoral and post-doctoral students. The final chapter completes the overview of my activities: research administration, teaching at the University of Nice-Sophia Antipolis, scientific outreach, scientific culture spreading, etc