Fabrication, assessment, and application of confined structures in photonic glasses

Sol-gel route is employed to prepare three nanostructured systems, namely core-shell Er³⁺-activated silica particles, Er³⁺-activated silica inverse opal; and spherical microresonators coated by Er³⁺-activated silica-hafnia film. Fabrication protocol, morphology, and spectroscopic assessment are presented. All the structures exhibit high compositional homogeneity leading to a significant ⁴I_13/2 luminescence quantum yield. In the case of inverse opals a quantum efficiency of about 90% was estimated by lifetime measurements. The spherical microresonators was considered for whispering gallery mode analysis showing that the fluorescence spectra are quasi independent on the thermal effect linked to injected power.