Précipitation photo-induite de nanocristaux dans une nouvelle génération de fibres optiques dédiées aux environnements à haute température

Fs-Laser Induced precipitation of nanocrystals in next generation of optical fibers dedicated to High Temperature Environments

• Auteur / Autrice : Semen Stopkin
• Direction : Matthieu Lancry, Tobias Habisreuther
• Type : Projet de thèse
• Discipline(s) : Chimie
• Date : Inscription en doctorat le 01/10/2025
• Etablissement(s) : université Paris-Saclay
• Ecole(s) doctorale(s) : École doctorale Sciences chimiques : molécules, matériaux, instrumentation et biosystèmes
• Partenaire(s) de recherche : Laboratoire : Institut de Chimie Moléculaire et des Matériaux d'Orsay
• Partenaire(s) de recherche : Equipe de recherche : Synthèse, Propriétés & Modélisation des Matériaux
• Partenaire(s) de recherche : Référent : Faculté des sciences d'Orsay

Mots clés

Mots clés libres

Laser femtoseconde

Verres aluminosilicatés

Fibres optiques

Science des matériaux

Chimie des solides

Capteurs

Solide state chemistry

Optical sensors

Silicate glasses

Materials science

Femtosecond laser

Optical fibers

Résumé

High temperatures (typically above 800°C) are common in a wide range of technological fields, such as turbine engines in trains, aircraft, and space vehicles, as well as in manufacturing processes (e.g., 3D laser additive manufacturing of metal or ceramic parts, the steel and glass industries), nuclear reactors (for future reactor instrumentation and tokamaks), photonics (for continuous wave (CW) kW-level fiber lasers), structural health monitoring, and fire alarm systems. As a result, there is a growing need for functionalized oxide glass-based photonic devices that can withstand such high-temperature (HT) environments, offering significant advantages over conventional thermocouples, such as compactness, high sensitivity, and resistance to corrosive conditions. To develop glass-based HT photonic devices (e.g., Bragg gratings or waveguides), the glass must be functionalized, which typically involves stable refractive index modulation. Femtosecond laser direct writing (FLDW) is the most suitable tool for this purpose, as it enables nonlinear light absorption, generating extreme field intensities (10-100s TW/cm²) along with high pressures and temperatures (hundreds of GPa and thousands of °C) in a confined volume of just tens of µm³. These conditions induce unique, oriented material transformations in 3D, driven by thermal, mechanical, and optical forces, such as chemical species migration, oxide dissociation, and nanocrystallization. Currently, porous nanostructures in silica or Ge-doped silicate glasses (Types II and III) demonstrate the best performance but lose stability as they fully erasure around 1265°C for 30 minutes or 1050°C for one month in pure silica. A paradigm shift is therefore required to achieve stable operation in the 1000–1500°C range. In 2024, our consortium demonstrated that fs-laser-induced nanocrystallization (3:2 Mullite, t-ZrO₂) in Al₂O₃-SiO₂ and ZrO₂-Al₂O₃-SiO₂ bulk glasses resulted in a positive index contrast (Δn ~10⁻³) that remained thermally stable up to 1600°C for 30 minutes. This world-record thermal stability for fs-laser-induced structures in glass is the result of a newly discovered regime, Type Ic (where 'c' stands for crystallization), where permanent chemical migration and crystallization make this possible. Building on this proof-of-concept, the current PhD project aims to further explore and master this new regime.