Fig. 1. Relationship between density of TeO₂-GeO₂-BaO glasses and doping concentration of system. (a) Dy³⁺-doped; (b) Tb³⁺-doped; (c) Tb³⁺/Dy³⁺ codoped

Fig. 2. Transmission spectra of TeO₂-GeO₂-BaO glasses with different doping concentrations. (a) Dy³⁺-doped; (b) Tb³⁺-doped; (c) Tb³⁺/Dy³⁺ codoped

Fig. 3. (a) Excitation and (b) emission spectra of Dy³⁺-doped TeO₂-GeO₂-BaO glasses

Fig. 4. Luminescence decay curves of 577 nm emission from Dy³⁺-doped TeO₂-GeO₂-BaO glasses excited by 351 nm

Fig. 5. (a) Excitation and (b) emission spectra of Tb³⁺-doped TeO₂-GeO₂-BaO glasses

Fig. 6. Luminescence decay curves of 542 nm emission from Tb³⁺-doped TeO₂-GeO₂-BaO glasses excited by 377 nm

Fig. 7. (a),(c) Excitation and (b),(d) emission spectra of Tb³⁺/Dy³⁺ codoped TeO₂-GeO₂-BaO glasses

Fig. 8. Photoluminescence spectra of TeO₂-GeO₂-BaO glasses with different doping concentrations. (a) Dy³⁺-doped; (b) Tb³⁺-doped; (c) Tb³⁺/Dy³⁺ codoped

Fig. 9. (a) Emission spectra and (b) integrated emission intensity of both Dy³⁺ (577 nm) and Tb³⁺ (543 nm) as a function of doping concentrations of Tb₂O₃ of Tb³⁺/Dy³⁺ codoped TeO₂-GeO₂-BaO glasses at 390 nm excitation