Luminescence of Yb-doped YAG: Divalent ytterbium ions

•We have identified divalent ytterbium ions in the optical Yb: YAG ceramic.•Electron configuration of the ground state of Yb2+ is 4f136s.•Pulsed cathodoluminescence and transmission spectra of Yb2+ appear at 913-1050 nm.•Yb2+ ions in association with oxygen vacancies generate Re‐F centres.•Re‐F centres are able to absorb at 280, 365, 630 nm.•Re‐F centres are able to emit at 325, 520, 590‐720 590-720 nm.

This study reports the presence of Yb2+ ions with 4f136s electron configuration of the ground state in addition to Yb3+ ions in yttrium aluminium garnet ceramics activated by ytterbium. Pulsed cathodoluminescence and transmission spectra of divalent ytterbium ions appear as narrow lines of s↔s transitions at 913-1050 nm range. These ions in association with oxygen vacancies generate Re-F centres which are able to absorb at 280, 365, 630 nm and emit at 325, 520, 590−720 nm in d↔s transitions of Yb2+ ions; the emission band at 590-720 nm consists of eight narrow lines. The Re-F centeres are manifested most clearly in the ceramic samples obtained directly after vacuum sintering at 1800 °C.