Broadband Near-Infrared Luminescence in Lead Germanate Glass Triply Doped with Yb(3+)/Er(3+)/Tm(3+)

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