Broadband Near-Infrared Luminescence in Lead Germanate Glass Triply Doped with Yb3+/Er3+/Tm3

This paper deals with broadband near-infrared luminescence properties of lead germanate glass triply doped with Yb3+/Er3+/Tm3+. Samples were excited at 800 nm and 975 nm. Their emission intensities and lifetimes depend significantly on Er3+ and Tm3+ concentrations. For samples excited at 800 nm, broadband emissions corresponding to the overlapped H-3(4) -> F-3(4) (Tm3+) and I-4(13/2) -> I-4(15/2) (Er3+) transitions centered at 1.45 mu m and 1.5 mu m was identified. Measurements of decay curves confirm reduction of H-3(4) (Tm3+), F-2(5/2) (Yb3+) and I-4(13/2) (Er3+) luminescence lifetimes and the presence of energy-transfer processes. The maximal spectral bandwidth equal to 269 nm for the F-3(4) -> H-3(6) transition of Tm3+ suggests that our glass co-doped with Yb3+/Er3+/Tm3+ is a good candidate for broadband near-infrared emission. The energy transfer from I-4(13/2) (Er3+) to F-3(4) (Tm3+) and cross-relaxation processes are responsible for the enhancement of broadband luminescence near 1.8 mu m attributed to the F-3(4) -> H-3(6) transition of thulium ions in lead germanate glass under excitation of Yb3+ ions at 975 nm.