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• GeO 2 -TiO 2 -BaO-BaF 2 -Ga 2 O 3 system doped with Er3+, Tm3+, Ho3+ were synthesized. • The extremely low IR absorption coefficients were achieved. • Enhanced emission at 1.5 µm, 1.8µm and 2.0 µm by introducing BaF 2 in the composition was observed. • The luminescence lifetime significantly increased in the function BaF 2. • Optimal BaF 2 content in titanate-germanate glass was evaluated. A novel TiO 2 -GeO 2 -BaO-BaF 2 -Ga 2 O 3 glasses doped with rare-earth were synthesized, and the impact of the substitution of BaF 2 for BaO on properties has been investigated by luminescence spectroscopy. The IR absorption coefficient is extremely low, which is attractive for optical fibers emitting NIR radiation. Near-IR luminescence associated to the Er3+:4I 13/2 → 4I 15/2 (FWHM = 108 nm), Tm3+:3F 4 → 3H 6 (FWHM = 244 nm) and Ho3+:5I 7 → 5I 8 (FWHM = 179 nm) transitions are enhanced in the presence of BaF 2. Luminescence lifetimes increase with increasing content of BaF 2 in the glass composition. Fabricated optical materials with relatively high BaF 2 content represent a good starting point for further investigations in the field of glass technology and modern photonics. [ABSTRACT FROM AUTHOR]

[Display omitted] • The physicochemical and optical properties of TiO 2 -modified barium gallo-germanate glasses co-doped with Er3+ and Yb3+ were characterized. • The near-IR luminescence at 1.5 μm (Er3+: 4I 13/2 → 4I 15/2) is enhanced significantly in the TiO 2 -GeO 2 -BaO-Ga 2 O 3 system. • Based on the lifetime values, the energy transfer efficiencies were estimated. • The effect of pair Yb3+/Er3+ was verified by the Stark splitting observed for hypersensitive Er3+:4I 15/2 → 2H 11/2 transition. • XRD analysis confirmed the presence of crystalline phases in the highly Yb3+ and Er3+ co-doped titanate-germanate samples with Yb 2 Ti 2 O 7 and Er 2 Ti 2 O 7 phases. This work combines photoluminescence methods, Raman spectroscopy, and X-ray diffraction (XRD) to expand the knowledge of the effects of pair rare earth ions doping on the physicochemical and near-IR properties of glasses. For this purpose, glass systems based on GeO 2 -BaO-Ga 2 O 3 (GBG) and TiO 2 -GeO 2 -BaO-Ga 2 O 3 (TGBG) doped with Er3+ ions (0.1, 0.25, 0.5 mol%) and Yb3+ ions (0.5, 1.25, 2.5 mol%) were synthesized and analyzed. The near-IR luminescence band corresponding to Er3+:4I 13/2 → 4I 15/2 is narrowed for germanate-based glasses (FWHM = 31 nm), whereas in the presence of TiO 2 is more intense and broadened (FWHM = 65 nm). The energy transfer efficiencies between Yb3+ and Er3+ ions in glass samples have been calculated. Notably, the absorption spectra showed the Stark splitting for the band due to the 4I 15/2 → 2H 11/2 hypersensitive transition. Finally, we find the formation of Er 2 Ti 2 O 7 and Yb 2 Ti 2 O 7 crystalline phases in highly doping titanate-germanate samples. The results provide valuable ideas to evaluate the effect of the rare earths doping procedure on properties of designed glasses for near-IR luminescence applications. [ABSTRACT FROM AUTHOR]