The near-infrared band luminescence in silver NPs embedded tellurite glass doped with Er3+/Tm3+/Yb3+ ions

Metallic silver nanoparticles (Ag NPs) with various concentrations were embedded into Er3+/Tm3+/Yb3+ tri-doped tellurite glasses prepared using melt-quenching and heat-treated techniques. Heat-treatment at temperature above the glass transition temperature induced the nucleation and growth of near-spherical shape silver NPs confirmed by the transmission electron microscopy (TEM) images, and the average diameter of silver NPs was about 10 nm. The thermal stability, structural and optical properties of the prepared glasses were characterized by the differential scanning calorimeter (DSC) curves, X-ray diffraction (XRD) patterns, absorption spectra, luminescence spectra and fluorescence decay curves. The DSC curves displayed that the prepared glasses possess good thermal stability with ∆T larger than 138 °C while the XRD patterns indicated the amorphous structural nature. Under the excitation of 980 nm LD, the luminescence spectra exhibited two intense near-infrared band fluorescence at 1.81 and 1.53 μm in the wavelength range of 1400-2200 nm, which are originated from the Tm3+:3F4 → 3H6 and Er3+:4I13/2 → 4I15/2 transitions respectively. With the embedding of 0.5 mol % amount of silver NPs, the 1.81 μm band fluorescence of Tm3+ increased significantly by about 70%, mainly due to the local electric field enhanced effect induced by silver NPs on the basis of energy transfers from Er3+ to Tm3+ ions, and the energy transfer efficiency, micro-coefficient and critical radius were calculated to elucidate the interaction mechanism between Er3+ and Tm3+ ions. Additionally, the intensity parameters Ωt(t = 2, 4, 6) and radiative properties of Tm3+ such as the transition probabilities, radiative lifetimes and branching ratios were calculated from the measured absorption spectra based on Judd-Ofelt theory. The present results indicate that the Er3+/Tm3+/Yb3+ tri-doped tellurite glass with an appropriate amount of silver NPs is a promising luminescent material applied for the near-infrared band solid-state lasers and fiber amplifiers.