Visible luminescence of Tb³⁺ ions doped materials has found various applications in display techniques, visible light communication and medical treatment. Fluoride glasses are commonly used as a host material for gain fiber due to their low-energy phonon distribution. Unfortunately, poor chemical and mechanical properties, fabrication difficulties and expensive cost limit their development and further applications.

Most recently, a research team led by Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, has succeeded in strengthening the absorption of Tb³⁺ ions by introducing Dy³⁺ sensitizer in phosphate glasses. The study was published in Journal of the American Ceramic Society.

In their experiment, Tb³⁺/Dy³⁺ co-doped phosphate glasses were synthesized as a function of Dy³⁺ ions concentration by mature processing techniques. The element distributions, phases, absorption, emission spectra, and fluorescence lifetimes of Tb³⁺ and Dy³⁺ ions, as well as the energy transfer mechanisms were characterized and investigated. Homogeneous element distributions and uniform non-crystalline phases demonstrated a good quality of their phosphate glasses.

They found that large Judd–Ofelt parameters Ω₂ and Ω₄/Ω₆ for Tb³⁺ ions could reach up to 21.60 × 10–20 cm² and 0.73, respectively. Efficient sensitizer of Dy³⁺ for visible emission of Tb³⁺ was demonstrated, and a maximum energy transfer efficiency 55.0% for 4:0.5 ratio of Tb³⁺/Dy³⁺ at 425 nm wavelength for pumping was found.

Moreover, as a long lifetime of fluorescence decay is favorable for more efficient laser operation, a longest lifetime (2.86 ms) of Tb³⁺: ⁵D₄ level in Tb³⁺/Dy³⁺ co-doped doped phosphate glasses was measured, which was much higher than those in other kinds of glasses.

This research may lead to a host material for fiber laser operated at visible wavelength.

This work was supported by National Key R&D Program of China, the National Natural Science Foundation of China and the Natural Science Foundation of Shanghai.

Characterizations of Tb³⁺/Dy³⁺ co-doped phosphate glasses. (Image by SIOM)