Up- and downconversion luminescence properties of Nd³⁺ Ions Doped in Bi₂O₃-BaO-B₂O₃ glass system

Physical, optical, and luminescence properties of Nd³⁺ ions in bismuth barium borate glass system were studied. The glasses prepared by a melt quenching method were doped at various Nd₂O₃ concentrations in compositions (40-x)B₂O₃: 40Bi ₂O₃: 20BaO: xNd₂O₃ (where x = 0.00, 0.50, 1.00, 1.50, 2.00, and 2.50 in mol%). Luminescence properties of the glasses were studied under two excitations of 585 and 750 nm for downconversion. From both excitations, the results show emission bands in NIR region corresponding to the transitions between ⁴F_3/2 → ⁴I_9/2 (900 nm), ⁴F_3/2 → ⁴I_11/2 (1,060 nm), and ⁴F_3/2→ ⁴I_13/2 (1,345 nm). The luminescence intensity obtained with 585 nm excitation was stronger than 750 nm, with the strongest NIR emission at 1,060 nm. The upconversion emission spectrum exhibits strong fluorescence bands in the UV region at 394 nm (λex=591 nm). The processes are associated with excited state absorption (ESA) from ⁴F_3/2 level to ⁴D_3/2 level and it is the radiative decay from the ⁴D_3/2 to ground levels (⁴D_3/2 → ⁴I_13/2) which are responsible for the emission at 394 nm.