Spectroscopy and diode-pumped laser operation of transparent Tm:Lu<sub>3</sub>Al<sub>5</sub>O<sub>12</sub> ceramics produced by solid-state sintering
Fangxin Yue, Pavel Loiko, Mengting Chen, Josep María Serres, Yicheng Wang, Jiang Li, Liza Basyrova, Е. Б. Дунина, А. А. Корниенко, Liudmila Fomicheva, Shibo Dai, Zhenqiang Chen, Jı Eun Bae, Tae Gwan Park, Fabıan Rotermund, Venkatesan Jambunathan, Antonio Lucianetti, Tomáš Mocek, Magdalena Aguiló, Francesc Dı́az, Uwe Griebner, Valentin Petrov, Xavier Mateos
Abstract
A transparent Tm:Lu 3 Al 5 O 12 ceramic is fabricated by solid-state reactive sintering at 1830 °C for 30 h using commercial α -Al 2 O 3 and Lu 2 O 3 /Tm 2 O 3 powders and sintering aids - MgO and TEOS. The ceramic belongs to the cubic system and exhibits a close-packed structure (mean grain size: 21 µm). The in-line transmission at ∼1 µm 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 2.37×10 −21 cm 2 at 1749nm and the radiative lifetime of the 3 F 4 state is about 10 ms. The modified Judd-Ofelt theory accounting for configuration interaction is applied to determine the transition probabilities of Tm 3+ , yielding the intensity parameters Ω 2 = 2.507, Ω 4 = 1.236, Ω 6 = 1.340 [10 −20 cm 2 ] and α = 0.196×10 −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:Lu 3 Al 5 O 12 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 µm.