Photoluminescence study of Er-doped zinc–sodium–antimonite glasses

Abstract

Bulk samples of Er-doped zinc–sodium–antimonite glasses have been investigated by transmission and photoluminescence (PL) spectroscopy. Two series of compositions, (Sb2O3)90−x(Na2O)10(ZnO)x and (Sb2O3)80−x(Na2O)20(ZnO)x, doped with 0.25mol% Er2O3, have been chosen for this study. Transmission spectra exhibit sharp absorption bands centred at 450, 489, 521, 545, 652, 795, 975 and 1530nm, which correspond to absorption of Er3+ ions and they are attributed to the optical transitions from the ground state 4I15/2 to the excited states 4F5/2, 4F7/2, 2H11/2, 4S3/2, 4F9/2, 4I9/2, 4I11/2 and 4I13/2, respectively. The optical gap has been found to vary from 3.09 to 3.15eV with a tendency to decrease at higher Na2O and/or ZnO contents. Four extrinsic bands due to OH−, Si–O, CO2, and (CO3)2− carbonate group vibrations have been identified in the infrared region. Emission spectra are overwhelmed by narrow 4f–4f emission bands. Fine structure of emission bands at 980 and 1530nm, corresponding to radiative transitions from two lowest excited states of Er3+ ions to the ground state manifold have been investigated at room temperature and at 4K. A schematic energy diagram of Stark levels splitting for the three lowest manifolds 4I11/2, 4I13/2 and 4I15/2 has been deduced and the nature of temperature broadening of 4f–4f PL bands has been discussed.