Enhanced up-conversion and 2.7 µm luminescence of Er³⁺/Yb³⁺ co-doped yttrium lanthanum oxide transparent ceramics pumped at 980 nm

The optical properties of Er³⁺ ions in Er³⁺/Yb³⁺ co-doped yttrium lanthanum oxide transparent ceramics prepared by conventional ceramic processing have been investigated as a function of the rare-earth doping content. Absorption spectra, mid-infrared, near-infrared and up-conversion luminescence spectra and decay curves have been measured exciting at 980 nm. Large absorption cross-section of Yb³⁺ ion (1.6 × 10^–20 cm²) and the enhanced mid-infrared, near-infrared and red up-conversion luminescence demonstrate that Yb³⁺ ion is a promising sensitizer to efficiently activate Er³⁺ ion for 2.7 µm emission. Large Judd–Ofelt parameter Ω₂ and spectroscopic quality factor value around 5.73 × 10^–20 cm² and 6.22 respectively have been obtained, as well as higher emission cross-section for 2.7 µm emission (2.18 × 10^–20 cm²). These results indicate that the Yb³⁺/Er³⁺:(Y_0.9La_0.1)₂O₃ transparent ceramic is a predominant host material for MIR lasers and infrared-to-visible up-converters.