Thermal stability and spectroscopic properties of Er 3+-doped lead fluorogermanate glasses

Abstract

The thermal characterization and spectroscopic properties of Er 3+-doped 0.6 GeO 2 - ( 0.4 - x ) PbO – x PbF 2 glasses were investigated experimentally. With the replacement of PbO by PbF 2 the thermal stability of glasses is improved and the infrared fluorescence intensity at 1530 nm is increased. The Judd–Ofelt intensity parameters, radiative transition rates, and fluorescence lifetimes of the excited 4I 13/2 level of Er 3+ ions were calculated from Judd–Ofelt theory. The asymmetric ligand field around Er 3+ ions resulted from the incorporation of PbF 2 into germanate glasses, broadens the infrared emission spectra at 1530 nm. Upconversion luminescence in the investigated glasses was observed at room temperature under the excitation of 976 nm laser diode. The glass 0.6 GeO 2 – 0.3 PbO – 0.1 PbF 2 exhibits the maximum upconversion emission intensity, while no frequency upconversion luminescence was observed in the 0.6 GeO 2 – 0.4 PbO glass. The quadratic dependence of the green and red emissions on excitation power indicates that two-photon absorption contributes to the visible emission under the 976-nm excitation.