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

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 (T-R) and liquid nitrogen (T-LN) temperatures. Transitions of Er3+ ions from the I-4(15/2) ground energy level to their higher levels F-4(9/2), I-4(9/2), I-4(11/2) and I-4(13/2) are well observed at both temperatures as absorption peaks at similar to 660, 810, 985 and 1540 nm, respectively. At TLN temperature, it is also possible to resolve the absorption band at similar to 550 nm, which corresponds to I-4(15/2)-> S-4(3/2) transition. The most intense fluorescence emission is observed at similar to 1 mu m and similar to 1.5 mu m wavelengths, which are identified as I-4(11/2)-> I-4(15/2) and I-4(13/2)-> I-4(15/2) radiative transitions of Er3+ ions. It is shown by PAL spectroscopy, that the addition of Er causes an increase of positron lifetime in defects tau(2) and a decrease in the intensity I-2 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.