Highly efficient lasing and thermal properties of Tm:Y₂O₃ and Tm:(Y,Sc)₂O₃ ceramics

We report on thermal, spectroscopic, and laser properties of transparent 5 at.% Tm³⁺-doped yttria and "mixed" yttria-scandia ceramics fabricated by vacuum sintering at 1750°C using nanoparticles produced by laser ablation. The solid-solution (Tm_0.05Y_0.698Sc_0.252)₂O₃ ceramic features a broadband emission extending up to 2.3 µm (gain bandwidth, 167 nm) and high thermal conductivity of 4.48 W m^-1 K^-1. A Tm:Y₂O₃ ceramic laser generated 812 mW at 2.05 µm with a slope efficiency η of 70.2%. For the Tm:(Y,Sc)₂O₃ ceramic, the output power was 523 mW at 2.09 µm with η = 44.7%. These results represent record-high slope efficiencies for any parent or "mixed" Tm³⁺-doped sesquioxide ceramics.