Visible luminescence of Pr³⁺ ions doped materials, has found various applications in medical treatment, visible light communication, and display techniques. Unfortunately, Pr³⁺ ions doped oxide glass fibers suffer from photo-darkening under blue laser pumping, which affects their visible laser performance.

Most recently, a research team led by Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, has succeeded in suppressing the photo-darkening of Pr³⁺ ions by introducing Ce³⁺ ions in silicate glasses. The study was published in Journal of the American Ceramic Society on Jan. 7, 2022.

In their experiment, Pr³⁺/Ce³⁺ co-doped silicate glass fiber was synthesized as a function of Ce³⁺ ions concentration by mature processing techniques. The absorption, emission spectra, and fluorescence lifetimes of Pr³⁺, as well as the energy transfer mechanisms, were characterized and investigated.

They found that the photodarkening effect of Pr³⁺ in silicate fibers is efficiently inhibited by energy transfer with Ce³⁺ ions. The visible emission intensity of Pr³⁺/Ce³⁺ co-doped silicate glass fiber is maintained at 93.3% of the initial value after the radiation of the 486 nm laser for 30 min.

Moreover, the hole centers and the electron centers are trapped by Ce⁴⁺ and Ce³⁺ ions respectively, which strengthens the radiation resistance of glass fibers.
This research may lead to a host material for fiber laser operated at visible wavelength.

Energy transfer between Pr³⁺ and Ce³⁺ in silicate glasses. (Image by SIOM)