Spectroscopy and efficient laser operation around 2.8 μm of Er:(Lu,Sc)2O3 sesquioxide ceramics

Highlights: • Transparent "mixed" 7 at.% Er:(Lu,Sc)2O3 sesquioxide ceramic. • Fabrication by hot isostatic pressing at 1750 °C / 200 MPa in argon atmosphere. • The stimulated-emission cross-section for Er³⁺ ions is 1.30 × 10^-20 cm² at 2719 nm. • The ceramic exhibits a significant inhomogeneous broadening of the spectral bands. • The ceramic laser generated 342 mW at 2.71&2.85 μm with a slope efficiency of 41.7 %. A transparent "mixed" 7 at.% Er:(Lu,Sc)₂O₃ sesquioxide ceramic was fabricated by hot isostatic pressing of commercial sesquioxide powders at 1750 °C/200 MPa in argon atmosphere. It exhibited a cubic bixbyite-type structure (a = 10.198 Å), a mean grain size of 5.7 μm and high low-signal transmission of 79.1 % in the near-IR. The spectroscopic properties of Er³⁺ ions were studied. For the ⁴I_11/2 → ⁴I_13/2 transition, the stimulated-emission cross-section σ_SE is 1.30 × 10⁻²⁰ cm² at 2719 nm, the corresponding luminescence branching ratio B(JJ') is 19.9 % and the radiative lifetime of the ⁴I_11/2 state is 4.80 ms, as determined using a Judd-Ofelt theory accounting for intermediate configuration interaction. The crystal-field splitting of Er³⁺ multiplets was studied at 12 K. The ceramic exhibits a significant inhomogeneous broadening of spectral bands. An Er:(Lu,Sc)₂O₃ ceramic laser generated 342 mW at 2.71 and 2.85 μm with a high slope efficiency of 41.7 % (exceeding the Stokes limit) and a laser threshold of 125 mW.