Stimulated-emission cross-sections of trivalent erbium ions in the cubic sesquioxides Y 2 O 3 , Lu 2 O 3 , and Sc 2 O 3

We report on a detailed revision of the spectroscopic properties of Er 3+ ions in the cubic sesquioxide host crystals R 2 O 3 (R = Y, Lu and Sc). The 4f-4f transition probabilities are calculated by applying a modified Judd-Ofelt theory accounting for configuration interaction based on the measured absorption spectra. The stimulated-emission cross-sections for the 4 I 11/2 → 4 I 13/2 (at ∼2.8 µm) and 4 I 13/2 → 4 I 15/2 (at ∼1.6 µm) transitions of Er 3+ ions are determined and the luminescence dynamics from the 4 I 11/2 and 4 I 13/2 manifolds are studied at different temperatures. It is found that the luminescence lifetime of the 4 I 11/2 state strongly depends on the host-forming R 3+ cation even at low temperatures due to a non-negligible non-radiative multiphonon decay channel. Er:Y 2 O 3 exhibits the lowest phonon energies and consequently the longest 4 I 11/2 luminescence lifetimes. A disagreement between the absorption and emission probabilities for the 4 I 15/2 ↔ 4 I 11/2 transition of Er 3+ ions is observed at room temperature and explained considering the distribution of Er 3+ ions over two non-equivalent crystallographic sites, C 2 and C 3i .