Optical and spectroscopic properties of Er-doped niobium germanosilicate glasses and glass ceramics

Erbium-doped glasses with the molar composition 40GeO(2)center dot 10SiO(2)center dot 25Nb(2)O(5)center dot 25K(2)O, plus 0.1-4 mol% of ErO1.5, have been prepared by conventional melt quenching technique and their density, refractive index and characteristic temperatures have been determined. Transparent glass ceramics containing 1 and 2 mol% of ErO1.5 were also prepared and their XRD patterns and Raman spectra have been recorded and the crystalline phase K3.8Nb5Ge3O20.4 has been identified. UV/visible absorption spectra of the glasses and glass ceramics have been recorded and the resulting data was used for the Judd-Ofelt analysis, from which the Omega(2), Omega(4) and Omega(6) parameters were determined. Photoluminescence measurements of the glasses, at 154 mu m, showed an increase in intensity with increasing Er3+ concentration and a full width at half maximum ranging from similar to 40 to 47 nm for 0.1% and 4% ErO1.5, respectively. Radiative lifetimes of 4.3 and 5.5 ms were obtained for the 0.4 and 2% ErO1.5 doped glasses, respectively, while the measured lifetimes varied between 4.5 and 3.2 ms for the same compositions. Quantum efficiencies of 86% and 58% were obtained for the 1% and 2% Er-doped glasses, respectively. A quenching concentration of 6.2 x 10(20) ions/cm(3) was obtained for the glasses, corresponding to similar to 3.8 mol% of ErO1.5. The crystallization of the Er-doped samples led to similar intensities of the 1.54 mu m emission band as well as similar full width at half maximum, however a decrease was observed both in the radiative and the measured lifetimes, although quantum efficiencies remained around 85% and 54% for the 1% and 2% Er-doped glass ceramics, respectively. (c) 2010 Elsevier B.V. All rights reserved.