3D microstructuring of refractory nanocrystals by IR ultrafast lasers in oxide glasses for high Temperature photonic applications – REFRACTEMP

A wide range of industrial applications require high temperature environment (typ. > 800°C), including engine/propulsors in aeronautic/space sectors, or reactive chambers (metallurgy, laser additive manufacturing, nuclear reactors). Inside these environments, the use of glass-based optical components, including temperature/pressure sensors (e.g., Bragg gratings and Rayleigh backscattering sensors) enable shaping flexibility (fibers, bulks), low intrusiveness, lightness, and multiplexing ability. To date, the approach is based on commercial silica or lightly doped silica glass fiber materials initially developed for optical telecommunications. The latter are functionalized through laser irradiation to imprint a permanent structural change while preserving their intrinsic glass nature. To overcome the current limitations imposed by this conventional approach, this project proposes a disruptive methodology based on 1) the development and use of glass bulks and fibers dedicated to high temperature applications, and 2) the photo-precipitation of refractory nanocrystals (e.g., YAG, Al2O3, ZrO2 or eutectic mixtures of these compounds currently used in aerospace), as opposed to a simple refractive index variation. This novel approach requires non-conventional methods, for glass synthesis (Molten-Core method for fibers, aerodynamic levitation for bulk samples), and the use of ultrafast lasers enabling the photo-precipitation in 3D of nanocrystals with finely controlled and tuned characteristics (size, composition, spatial orientation). This approach will be tested by designing temperature sensor prototypes dedicated to exhaust gas chamber measurements and based on specifications provided by an industrial partner.