Frequency upconversion properties of Ag: TeO2-ZnO nanocomposites codoped with Yb3+ and Tm3+ ions

Yb3+-Tm3+ codoped tellurite glasses containing silver nanoparticles (NPs) were synthesized and characterized using transmission electron microscopy and optical techniques. The samples' composition and the nucleation of NPs were investigated using electron diffraction and energy dispersive spectroscopy. For the optical experiments, the samples were excited using a diode laser operating at 980 nm, in resonance with the Yb3+ transition F-2(7/2) -> F-2(5/2). Photoluminescence (PL) bands corresponding to Tm3+ transitions were observed at 480, 650, and 800 nm due to the Yb3+ -> Tm3+ energy transfer. PL enhancement was achieved by heat-treatment of the samples at 325 degrees C during different time intervals. The growth of the PL bands correlates with the increase of the silver NPs concentration. The relevant mechanisms contributing for the PL characteristics are discussed.