Visible luminescence of terbium (Tb3+) ion-doped materials has found various applications in display techniques, visible-light communications, and medical treatments. 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 development and further applications of luminescent doped fluoride glasses.
Phosphate glasses instead
Now, a research team from the Shanghai Institute of Optics and Fine Mechanics of the Chinese Academy of Sciences has succeeded in strengthening the absorption of Tb3+ ions by introducing a dysprosium (Dy3+) sensitizer in phosphate glasses.1
In their experiment, Tb3+/Dy3+ co-doped phosphate glasses were synthesized as a function of Dy3+ ion 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 noncrystalline phases showed that the phosphate glasses were high-quality.
The researchers found that the large so-called "Judd-Ofelt" parameters Ω2 and Ω4/Ω6 for Tb3+ ions could reach up to 21.60 × 10-20 cm2 and 0.73, respectively. Efficient sensitizing by Dy3+ for visible emission of Tb3+ was demonstrated, and a maximum energy transfer efficiency 55.0% for a 4:0.5 ratio of Tb3+/Dy3+ at a 425-nm pump wavelength was shown.
Moreover, as a long lifetime of fluorescence decay is favorable for more-efficient laser operation, a long lifetime (2.86 ms) for the Tb3+: 5D4 level in Tb3+/Dy3+ co-doped doped phosphate glasses was measured a lifetime much longerer than those in other kinds of glasses.
This research may lead to a host material for fiber lasers operated at visible wavelengths, say the researchers.
1. Yan Sun et al., Journal of the American Ceramic Society (2020); https://doi.org/10.1111/jace.17391.