Influence of annealing on microstructures and properties of Yb:Lu₂O₃ transparent ceramics

In this work, 5at.% Yb:Lu2O3 transparent ceramics were air-annealed at different temperatures to eliminate oxygen vacancies for laser performance improvement. The influence of annealing temperature on microstructures, optical quality, and laser performance was investigated comprehensively. The ceramics HIP (Hot isostatic pressing) post-treated at 1750 degrees C and annealed above 1100 degrees C show a significant optical quality decrease due to residual pore expansion, and the ceramic sample annealed at 900 degrees C shows better laser performance than others. The maximum output of 2.88 W was obtained at 1033.3 nm with a slope efficiency of 37.4% under a quasi-continuous wave (QCW) mode. Note that 5at.% Yb:Lu2O3 transparent ceramics HIP post-treated at 1550 degrees C still keep good transparency even when being annealed at 1300 degrees C due to less residual compressed pores. The highest slope efficiency is about 73.8% with a maximum output power of 2.84 W under QCW. Fine-grained and dense Yb:Lu2O3 transparent ceramics could be annealed at higher temperatures to eliminate oxygen vacancies more thoroughly to improve laser performance.