Optical properties of Er-doped Gax(Ge0.3Se0.7)100−x glasses

Optical properties of Gax(Ge0.3Se0.7)100−x glasses doped with Er2S3 have been investigated as a function of Ga and Er concentrations. The increase of Ga concentration from 0 to 13 at.% has decreased the optical gap Eg03 (corresponding to an absorption coefficient 103 cm−1) from 2.35 to 2.13 eV. The Urbach tail energy width has been observed to increase only slightly with Ga addition, and it is in the range 70–80 meV. Three absorption lines of Er3+ ions corresponding to 4I15/2 → 4I13/2, 4I15/2 → 4I11/2 and 4I15/2 → 4I9/2 transitions have been observed at 1538, 984 and 806 nm. In some samples with low content of Ga the line at 660 nm corresponding to transition 4I15/2 → 4F9/2 has been observed. The efficiency of absorption at 1538 nm (calculated as the ratio of integral 4I15/2 → 4I13/2 absorption per atomic concentration of embedded Er) showed a strong dependence on the Ga concentration (CGa). At CGa > 9 at.% this value was the highest and did not depend on Er concentration. The estimation of Judd–Ofelt parameters gave the values of Ω2 = (13 ± 2) × 10−20 cm2, Ω4 = (3.4 ± 0.2) × 10−20 cm2 and Ω6 = (1.3 ± 0.1) × 10−20 cm2, which are in good agreement with data published in literature for other chalcogenide glasses.