Luminescence of borogermanate glasses activated by Er3+ and Yb3+ ions

Glasses of the 25Ln2O3–25B2O3–50GeO2 composition (mol%) where Ln = (1 − x − y) La, xEr, yYb, with an addition of Al2O3 have been obtained and their luminescent characteristics examined. Probabilities of spontaneous emission, peak sections of the induced radiation and quantum yields of luminescence corresponding to the 2F5/2 → 2F7/2 transition of Yb3+ ions and the 4I13/2 → 4I15/2 transition of Er3+ ions have been defined. Quantum yield of Yb3+ luminescence for glasses with low Yb2O3 concentration reaches values closed to 100%. The luminescence spectrum of Er3+ ions exhibits a broad peak at about 1530 nm with effective width more than 80 nm when excited by irradiation at λ = 977 nm. Spontaneous emission probability and peak stimulated radiation section for Er3+ luminescence band 4I13/2 → 4I15/2 were determined to be equal to 175 s−1 and 4.9 × 10−21 cm2 respectively. Effective quenching of both rare-earth activators by oscillations with ν ≈ 2630 and 2270 cm−1 was found. These oscillators, most likely, represent OH-groups connected by a hydrogen bond with non-bridging oxygen atoms in the borogermanate matrix.