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

Erbium-doped glasses with the molar composition 40GeO 2 ·10SiO 2 ·25Nb 2 O 5 ·25K 2 O, plus 0.1-4mol% of ErO 1.5 , 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 ErO 1.5 were also prepared and their XRD patterns and Raman spectra have been recorded and the crystalline phase K 3.8 Nb 5 Ge 3 O 20.4 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 Ω 2 , Ω 4 and Ω 6 parameters were determined. Photoluminescence measurements of the glasses, at 1.54 μm, showed an increase in intensity with increasing Er 3+ concentration and a full width at half maximum ranging from ~40 to 47 nm for 0.1% and 4% ErO 1.5 , respectively. Radiative lifetimes of 4.3 and 5.5 ms were obtained for the 0.4 and 2% ErO 1.5 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 6.2×10 20 ions/cm 3 was obtained for the glasses, corresponding to ~3.8 mol% of ErO 1.5 . The crystallization of the Er-doped samples led to similar intensities of the 1.54 μm 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.