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

• Main Authors: Wojciech A. Pisarski, Joanna Pisarska, Radosław Lisiecki, Witold Ryba-Romanowski
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: Materials
• Subjects: lead germanate glasses; rare earth ions; near-infrared luminescence
• Online Access: https://www.mdpi.com/1996-1944/14/11/2901

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 ³H₄ → ³F₄ (Tm³⁺) and ⁴I_13/2 → ⁴I_15/2 (Er³⁺) transitions centered at 1.45 µm and 1.5 µm was identified. Measurements of decay curves confirm reduction of ³H₄ (Tm³⁺), ²F_5/2 (Yb³⁺) and ⁴I_13/2 (Er³⁺) luminescence lifetimes and the presence of energy-transfer processes. The maximal spectral bandwidth equal to 269 nm for the ³F₄ → ³H₆ 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 ⁴I_13/2 (Er³⁺) to ³F₄ (Tm³⁺) and cross-relaxation processes are responsible for the enhancement of broadband luminescence near 1.8 µm attributed to the ³F₄ → ³H₆ transition of thulium ions in lead germanate glass under excitation of Yb³⁺ ions at 975 nm.