Study on the Blue-Green Luminescence Properties of Tb3+-doped TeO2-GeO2-BaF2 glasses

Tb³⁺-doped 70TeO₂-10GeO₂-20BaF₂ (mol%) tellurite germanate glasses were synthesized by the melt-quenching method. The host glass was characterized by relatively low maximum phonon energy (820 cm^-1) and high thermal stability (ΔT=123 °C). Based on the absorption spectra, the fluorescence branching ratio (43.67%) of the ⁵D₄→⁷F₅ transition and the spontaneous radiative transition probability (66.14 s^-1) were calculated by Judd-Ofelt analysis. The sample exhibits luminescence peaks at 488 nm and 545 nm in the blue-green spectral region, and the luminescence intensity increases with rising Tb³⁺ concentration. It attained its peak value when the content of Tb₄O₇ is 4 mol%. Moreover, the gain coefficients and emission cross-section were calculated within the blue-green wavelength range. The emission cross-section reached a peak value of 2.28×10^-22 cm², and the gain coefficient attained a maximum of 0.46 cm^-1. In summary, the Tb³⁺-doped tellurite germanate glass possesses excellent physical and spectral properties and holds the potential to serve as a gain dielectric material for fiber lasers in the blue-green band.