Design of gold-silica core-shell nanostructures doped with rare earth ions for luminescence exaltation in the context of specialty optical fibers.
This work is part of the Fenoptic ANR project, which aims at taking advantage of the plasmonic properties of metallic nanoparticles incorporated into optical fibers. Optical signals attenuation occurring for long distances propagation is usually overcome by re-amplification. Optical amplification is based on rare earth ions stimulated emission. This work aims at improving the amplification process in optical fibers by efficiently coupling lanthanide ions with metallic nanoparticles to enhance their luminescence properties. Original multilayer nanostructures made of a gold core coated with sol-gel silica shells, either pure or doped with lanthanide ions, were specifically designed by soft chemistry. The size and shape of the gold nanoparticles, along with the thickness and doping rate of the silica shells, were finely controlled. Stable core-shell suspensions were thus obtained. Optical reference nanostructures were also prepared by gold core dissolution. These nanostructures are then incorporated into sol-gel silica matrices with high optical quality to study their photoluminescence intensities and lifetime decay profiles. Strong europium (III) luminescence quenching is observed for a 2 nm spacer between the gold nanospheres and the lanthanide ions. This extinction slightly decreases as the coupling distance increases, but still occurs for a 28 nm buffer layer thickness. Incorporation of the nanostructures into optical fibers silica cores was evaluated for a high-temperature process patented by Draka. Some preliminary trials were also conducted on a semi-industrial sol-gel process.