Fabrication of high‐efficiency Yb:Y2O3 laser ceramics without photodarkening

Abstract High‐efficiency Yb:Y 2 O 3 laser ceramics were fabricated using the vacuum‐sintering plus hot isostatic pressing (HIP) without sintering additives. High‐purity well‐dispersed nanocrystalline Yb:Y 2 O 3 powder was synthesized using a modified co‐precipitation method in‐house. The green bodies were first vacuum sintered at a temperature as low as 1430°C and then HIPed at 1450°C. Finally, the samples were air annealed at 800°C for 10 h. Although no sintering aids were used, full density of the samples with excellent optical homogeneity and an inline transmission of 80% at 400 nm could be obtained. Moreover, photodarkening phenomenon was not detected in the ceramics. Preliminary laser experiment with the fabricated ceramics in a two‐mirror cavity has demonstrated 32 W continuous‐wave (CW) output at ∼1077 nm with an optical‐to‐optical conversion efficiency of 58.2%. To the best of our knowledge, this is so far the highest CW output power and optical‐to‐optical conversion efficiency achieved with the Yb 3+ ‐doped sesquioxide ceramics in a simple two‐mirror cavity.