Influence of Modifier Cations on the Spectroscopic Properties of Dy3+ Doped Telluroborate Glasses for White Light Applications

Tuning the fluorescence of Dy3+ via the structure of borophosphate glasses

The optical characteristics of Dy³⁺-doped phosphate and borophosphate glasses with different divalent network modifiers prepared by melt-quenching are studied. The glass sets (A) with a molar composition of 40MO-60P₂O₅ and (B) with a molar composition of 40MO-20B₂O₃-40 P₂O₅ are investigated, both with M = (Zn²⁺, Mg²⁺, Ca²⁺, Sr²⁺, or Ba²⁺) and all doped with 0.1 mol% Dy₂O₃. Raman and fluorescence spectroscopy are used to analyse the structure and optical characteristics of these glasses. Four typical Dy³⁺ emission bands in the yellow (572 nm), blue (483 nm) and red (633 and 752 nm) regions of the spectrum are observed in both sets. The fluorescence lifetimes in each glass set are correlated to the network modifier's ionic field strength. The Mg²⁺ and Zn²⁺ containing glasses have the longest fluorescence lifetimes. The yellow to blue emission intensity ratio of the respective bands can be used to indicate a symmetric environment around Dy³⁺ ions and varies with the ionic field strength of the modifier cations: a higher ionic field strength leads to a higher yellow to blue ratio, which in turn indicates a higher asymmetrical local coordination environment of Dy³⁺ ions in the glassy host network.

Spectroscopy and energy transfer in lead borate glasses doubly doped with Tm3+ and Dy3+ ions

Lead borate glasses singly and doubly doped with Tm³⁺ and Dy³⁺ were prepared by traditional melt-quenching technique. The emission spectra of rare earths in studied glass systems were registered under different excitation wavelengths. The observed emission bands are located in the visible spectral region. They correspond to ¹D₂→³F₄ (blue) and ¹G₄→³H₆ (blue) transitions of Tm³⁺ as well as ⁴F_9/2→⁶H_15/2 (blue), ⁴F_9/2→⁶H_13/2 (yellow) and ⁴F_9/2→⁶H_11/2 (red) transitions of Dy³⁺. Moreover, the energy transfer process from Tm³⁺ to Dy³⁺ was observed. The luminescence bands originating to characteristic transitions of thulium and dysprosium ions are present on emission spectra under direct excitation of Tm³⁺. Luminescence lifetimes for the excited states of Tm³⁺ and Dy³⁺ ions in lead borate glass were also determined based on decay measurements. The luminescence intensities and lifetimes depend significantly on the relative concentrations of the optically active dopants.