On the fluorescence enhancement mechanism of Er³⁺ in germanate glass containing silver particles

The spectral properties of trivalent erbium ions (Er³⁺) are systematically studied in a melt-quenched germanate glass (60~GeO₂-20PbO-10BaO-10K₂O-0.1Ag₂O) containing silver (Ag) particles. Thermal treatment of the material leads to the precipitation of Ag particles as observed by transmission electron microscopy and confirmed by absorption spectrum for the obvious surface plasmon resonance peak of Ag particles. The fluorescence from Er³⁺ in the 10-min-annealed sample with Ag particles is found to be 4.2 times enhancement compared with the unannealed sample excited by 488-nm Ar⁺ laser. A comparison is made between a spectral study performed on the unannealed Er³⁺-doped sample and the one annealed for 20~min. The data of absorption cross section and Judd-Ofelt intensity parameters show the agreement between the two samples no matter whether there are Ag particles, indicating that the introduction of Ag particles by post-heat treatment has no effect on the crystal field environment of Er³⁺ ions. And the fluorescence enhancement is attributed to the surface plasmon oscillations of Ag particles in germanate glass.