Photoluminescence of Pr3+-, Dy3+- and Tm3+-doped transparent nanocrystallized KNbGeO5 glasses

Abstract

In this paper, we present the photoluminescence properties of Pr3+-, Dy3+- and Tm3+-doped potassium–niobium–germanate glasses and glass ceramics. From the x-ray diffraction measurement, the glass structure was established. These glasses have shown strong absorption bands in the near-infrared region. Compared with Pr3+-, Dy3+- and Tm3+-doped glasses, their respective glass ceramics have shown stronger emissions due to the presence of the K3.8Nb5Ge3O20.4 crystalline phase. For Pr3+ -doped glass, two weak emission bands centred at 616 nm(3P0 → 3H6) and 648 nm(3P0 → 3F2) and for glass ceramic strong emission bands centred at 533 nm(3P0 → 3H5), 616 nm(3P0 → 3H6) and 648 nm(3P0 → 3F2) along with weak emissions at 688 nm(3P1 → 3F3), 709 nm(3P0 → 3F3) and 732 nm(3P0 → 3F4) have been observed with 450 nm(3H4 → 3P2) excitation wavelength. Among them, 648 nm(3P0 → 3F2) has shown bright red emission. For the Pr3+ -doped glass and glass ceramic, upconversion emission spectra have also been measured. Bright blue upconversion luminescence was observed under 1D2 level excitation. With regard to Dy3+ : glass, a weak emission band centred at 576 nm(4F9/2 → 6H13/2) and for glass ceramic a blue emission band centred at 485 nm(4F9/2 → 6H15/2) and a bright fluorescent yellow emission at 576 nm(4F9/2 → 6H13/2) have been observed, apart from 4F9/2 → 6H11/2(664 nm) emission transition with an excitation at 389 nm(6H15/2 → 4I13/2, 4F7/2) wavelength. Emission bands of 1G4 → 3F4(650 nm), 3F3 → 3H6(707 nm) and 1G4 → 3H5(774 nm) transitions have been observed for the Tm3+ : glass and glass ceramic, with an excitation at 3H6 → 1G4(473 nm). Among them, the 1G4 → 3F4 transition (650 nm) shows bright red emission. The stimulated emission cross-sections of all the emission bands of Pr3+, Dy3+ and Tm3+ : glasses and glass ceramics have been computed based on their measured full width at half maximum (Δλ) and lifetimes (τm).