Spectroscopy of solid-solution transparent sesquioxide laser ceramic Tm:LuYO 3

We report on a detailed spectroscopic study of a Tm 3+ -doped transparent sesquioxide ceramic based on a solid-solution (lutetia – yttria, LuYO 3 ) composition. The ceramic was fabricated using commercial oxide powders by hot isostatic pressing at 1600°C for 3 h at 190 MPa argon pressure. The most intense Raman peak in Tm:LuYO 3 at 385.4 cm -1 takes an intermediate position between those for the parent compounds and is notably broadened (linewidth: 12.8 cm -1 ). The transition intensities of Tm 3+ ions were calculated using the Judd-Ofelt theory; the intensity parameters are Ω 2 = 2.537, Ω 4 = 1.156 and Ω 6 = 0.939 [10 20 cm 2 ]. For the 3 F 4 → 3 H 6 transition, the stimulated-emission cross-section amounts to 0.27 × 10 −20 cm 2 at 2059nm and the reabsorption-free luminescence lifetime is 3.47 ms (the 3 F 4 radiative lifetime is 3.85 ± 0.1 ms). The Tm 3+ ions in the ceramic exhibit long-wave multiphonon-assisted emission extending up to at least 2.35 µm; a phonon sideband at 2.23 µm is observed and explained by coupling between electronic transitions and the dominant Raman mode of the sesquioxides. Low temperature (12 K) spectroscopy reveals a significant inhomogeneous spectral broadening confirming formation of a substitutional solid-solution. The mixed ceramic is promising for ultrashort pulse generation at >2 µm.