First laser emission of Yb0.15:(Lu0.5Y0.5)3Al5O12 ceramics

Achievements and Future Perspectives of the Trivalent Thulium-Ion-Doped Mixed-Sesquioxide Ceramics for Laser Applications

This paper is devoted to reviewing the latest results achieved in solid-state lasers based on thulium-doped mixed-sesquioxide ceramics, i.e., (Lu,Sc,Y)₂O₃. The near- and mid-infrared regions are of interest for many applications, from medicine to remote sensing, as they match molecular fingerprints and cover several atmospheric transparency windows. These matrices are characterized by a strong electron–phonon interaction—which results in a large splitting of the ground state—and by a spectral broadening of the optical transition suitable for developing tunable and short-pulse lasers. In particular, the manuscript reports on the trivalent thulium laser transitions at 1.5, 1.9, and 2.3 µm, along with the thermal and optical characteristics of the (Lu,Sc,Y)₂O₃ ceramics, including the fabrication techniques, spectroscopic and optical properties, and laser performances achieved in different pumping regimes, such as continuous-wave (CW), quasi-CW, and pulsed modes. A comparison of the performance obtained with these mixed-sesquioxide ceramics and with the corresponding crystals is reported.

A Comprehensive Characterization of a 10 at.% Yb:YSAG Laser Ceramic Sample

We report a comprehensive characterization of a 10 at.% Yb³⁺-doped YSAG (Yb:Y₃Sc_xAl_(5−x)O₁₂, x = 1.5) ceramic, including microstructural, spectroscopic and laser properties. Moreover, we illustrate and discuss the fabrication technique. Yb³⁺ in YSAG features a broader absorption and emission band than in traditional YAG, which is advantageous for laser applications (i.e., tunable laser sources, ultrafast pulse generation). Pumping in a quasi continuous wave regime at 936 nm, the ceramic has shown good laser performance as the maximum output power was 6.3 W with a corresponding slope efficiency (η_s) of 67.8%. In continuous wave regime instead, the maximum output power was 5 W with η_s = 52.7%. The laser emission wavelengths in free running were λ_L = 1051 nm and λ_L = 1031 nm, depending on the output coupler transmission. Finally, by a tunable cavity we obtained laser emission spanning from 991.5 to 1073 nm, i.e., 81.5 nm, which is the broadest tuning range ever reported for this material, to the best of our knowledge.

Spectroscopic and laser characterization of Yb0.15:(LuxY1-x)3Al5O12 ceramics with different Lu/Y balance

We report a broad comparative analysis of the spectroscopic and laser properties of solid solution Lutetium-Yttrium Aluminum Garnet (LuYAG, (Lu_xY_1-x)₃Al₅O₁₂) ceramics doped with Yb. The investigation was mainly aimed to assess the impact of the Lu/Y ratio on the Yb optical and laser properties. Therefore we analyzed a set of samples with different Y/Lu balance, namely 25/75, 50/50 and 75/25, with 15% Yb doping. We found that the Yb absorption and emission spectra changed from YAG to LuAG when gradually increasing in Lu content. Regarding the laser emission, remarkable results were achieved with all samples. Maximum output power was 8.2 W, 7.3 W and 8.7 W for Y/Lu balance 25/75, 50/50 and 75/25 respectively, at 1030 nm; the slope efficiency and the optical-to-optical efficiencies approached or exceeded 60% and 50% respectively. The tuning range was investigated using an intracavity ZnSe prism. The broadest tuning range (998 nm to 1063 nm) was obtained with Y/Lu balance 75/25, whereas the emission of the other two samples extended from 1000 nm to 1058 nm. To the best of our knowledge, this is the first comparative analysis of Yb:LuYAG ceramics or crystals as laser host across such a broad range of Y/Lu ratios.