We report on a detailed spectroscopic study of a Tm3+-doped transparent sesquioxide ceramic based on a solid-solution (lutetia – yttria, LuYO3) 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:LuYO3 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 Tm3+ ions were calculated using the Judd-Ofelt theory; the intensity parameters are Ω2 = 2.537, Ω4 = 1.156 and Ω6 = 0.939 [1020 cm2]. For the 3F4 → 3H6 transition, the stimulated-emission cross-section amounts to 0.27 × 10−20 cm2 at 2059nm and the reabsorption-free luminescence lifetime is 3.47 ms (the 3F4 radiative lifetime is 3.85 ± 0.1 ms). The Tm3+ 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.

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Broadband emission properties of Tm3+-doped parent and binary / ternary solid-solution sesquioxide laser ceramics of the system Y2O3-Lu2O3-Sc2O3 were studied with a goal of developing materials capable of generating ultrashort pulses at ~2 μm.