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A transparent "mixed" 7 at.% Er:(Lu,Sc)(2)O-3 sesquioxide ceramic was fabricated by hot isostatic pressing of commercial sesquioxide powders at 1750 degrees C/200 MPa in argon atmosphere. It exhibited a cubic bixbyite-type structure (a = 10.198 angstrom), a mean grain size of 5.7 um and high low-signal transmission of 79.1 % in the near- IR. The spectroscopic properties of Er3+ ions were studied. For the I-4(11/2) -> I-4(13/2) transition, the stimulated-emission cross-section sigma(SE) is 1.30 x 10(-20) cm(2) at 2719 nm, the corresponding luminescence branching ratio B (JJ') is 19.9 % and the radiative lifetime of the I-4(11/2) state is 4.80 ms, as determined using a Judd-Ofelt theory accounting for intermediate configuration interaction. The crystal-field splitting of Er3+ multiplets was studied at 12 K. The ceramic exhibits a significant inhomogeneous broadening of spectral bands. An Er:(Lu,Sc)(2)O-3 ceramic laser generated 342 mW at 2.71 and 2.85 mu m with a high slope efficiency of 41.7 % (exceeding the Stokes limit) and a laser threshold of 125 mW.

We report on the development of a novel laser crystal with broadband emission properties at similar to 2 mu m - a Tm3+, Li+-codoped calcium tantalum gallium garnet (Tm:CLTGG). The crystal is grown by the Czochralski method. Its structure (cubic, sp. gr . la (3) over bard, a = 12.5158(0) angstrom) is refined by the Rietveld method. Tm:CLTGG exhibits a relatively high thermal conductivity of 4.33 Wm(-1) K-1. Raman spectroscopy confirms a weak concentration of vacancies due to the charge compensation provided by Li+ codoping. The transition probabilities of Tm3+ ions are determined using the modified Judd-Ofelt theory yielding the intensity parameters Omega(2) = 5.185, Omega(4) = 0.650, Omega(6) = 1.068 [10(-20) cm(2)] and alpha = 0.171 [10(-4) cm]. The crystal-field splitting of the Tm3+ multiplets is revealed at 10 K. The first diode-pumped Tm:CLTGG laser generates 1.08 W at similar to 2 mu m with a slope efficiency of 23.8%. The Tm3+ ions in CLTGG exhibit significant inhomogeneous spectral broadening due to the structure disorder (a random distribution of Ta5+ and Ga3+ cations over octahedral and tetrahedral lattice sites) leading to smooth and broad gain profiles (bandwidth: 130 nm) extending well above 2 mu m and rendering Tm:CLTGG suitable for femtosecond pulse generation. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

A transparent Tm:Lu3Al5O12 ceramic is fabricated by solid-state reactive sintering at 1830 degrees C for 30 h using commercial alpha-Al2O3 and Lu2O3/Tm2O3 powders and sintering aids - MgO and TEOS. The ceramic belongs to the cubic system and exhibits a close-packed structure (mean grain size: 21 mu m). The in-line transmission at similar to 1 mu m is 82.6%, close to the theoretical limit. The spectroscopic properties of the ceramic are studied in detail. The maximum stimulated-emission cross-section is 2.37x10(-21) cm(2) at 1749nm and the radiative lifetime of the F-3(4) state is about 10 ms. The modified Judd-Ofelt theory accounting for configuration interaction is applied to determine the transition probabilities of Tm3+, yielding the intensity parameters Omega(2) =2.507, Omega(4) = 1.236, Omega(6) = 1.340 [10(-20) cm(2)] and alpha = 0.196x10(-4) cm. The effect of excited configurations on lower-lying interconnected states with the same J quantum number is discussed. First laser operation is achieved under diode-pumping at 792 nm. A 4 at.% Tm:Lu3Al5O12 ceramic laser generated 3.12 W at 2022-2035nm with a slope efficiency of 60.2%. The ceramic is promising for multi-watt lasers at >2 mu m. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement