On the optical absorption and photoluminescence of Er-doped Ge–S–Ga glasses

We have studied the absorption and photoluminescence (PL) of (GeS2)80(Ga2S3)20 glasses doped with 0.17, 0.35 and 1.05 at.% Er. The sharp bands centered at around 660, 810, 980 and 1540 nm in the absorption spectra can be associated with intra 4f-shell transitions in Er3+ ions from 4I15/2 level to 4F9/2, 4I9/2, 4I11/2 and 4I13/2 levels, respectively. It has been observed that the absorption edge shifts towards lower energies with increasing Er concentration. A decrease in the absorption coefficient in the range of weak absorption, as well as the host luminescence in more heavily doped samples has been established, which may be associated with less native defects in the glassy structure. The role of excitation wavelength (λex) on the PL emission band at 1540 nm using different Er3+-doping level has been evaluated. It has been found that the total PL band remains almost the same under direct excitation of Er3+ ions (at λex = 644, 770 and 982 nm), while it becomes narrower under the host excitation (at λex = 532 nm).