Structural characterization, optical and PAL spectroscopy studies of Er3+-doped Ge20Ga5Sb10S65 glasses

Abstract The Ge20Ga5Sb10S65 glasses doped with Er3+ ions (0; 0.1; 0.5; 1.0 mol. %) are investigated with optical, fluorescence and positron annihilation lifetime (PAL) spectroscopies. The optical and fluorescence measurements were performed at room (TR) and liquid nitrogen (TLN) temperatures. Transitions of Er3+ ions from the 4I15/2 ground energy level to their higher levels 4F9/2, 4I9/2, 4I11/2 and 4I13/2 are well observed at both temperatures as absorption peaks at ~660, 810, 985 and 1540 nm, respectively. At TLN temperature, it is also possible to resolve the absorption band at ~550 nm, which corresponds to 4I15/2→4S3/2 transition. The most intense fluorescence emission is observed at ~1 μm and ~1.5 μm wavelengths, which are identified as 4I11/2→4I15/2 and 4I13/2→4I15/2 radiative transitions of Er3+ ions. It is shown by PAL spectroscopy, that the addition of Er causes an increase of positron lifetime in defects τ2 and a decrease in the intensity I2 of the corresponded lifetime component. These changes are explained in terms of positron trapping reduction due to the occupation of positron trapping Ga-based sites in the glass matrix by Er3+ ions.