Tm3+ doped Bi2O3–GeO2–Na2O glasses for 1.8 μm fluorescence

53.3BiO1.5–33.3GeO2–13.4NaO0.5 (cation%) glasses with various Tm3+ concentration were prepared by melt-quenching method. These glasses show high density, high refractive index, low phonon energy and good stability against crystallization. Absorption spectra of Tm3+-doped bismuthate glass were measured to obtain the radiative lifetimes by Judd-Ofelt theory. The absorption (4.5 × 10−21 cm2) and emission (6.7 × 10−21 cm2) cross-sections were calculated by Beer–Lambert and McCumber theory. The results show that the Tm3+ (3F4 → 3H6) in these glasses have high spontaneous radiative transition probabilities and large stimulated emission cross-section. Then the fluorescence emission spectra were measured under 808 nm excitation and the maximum emission intensity at 1.8 μm is obtained at 0.9 mol% Tm2O3 in the glasses.