| Summary: | A single crystal of ytterbium-doped “mixed” yttrium–lutetium aluminum garnet with a stoichiometric composition of (Y<sub>0.601</sub>Lu<sub>0.233</sub>Yb<sub>0.166</sub>)<sub>3</sub>Al<sub>5</sub>O<sub>12</sub> was grown by the Czochralski method and its structure, vibronic, spectroscopic, and laser properties were studied. The stimulated-emission cross-section for Yb<sup>3+</sup> ions was maximized to 2.53 × 10<sup>−20</sup> cm<sup>2</sup> at 1031 nm. The emission bandwidth was ~8 nm, and the reabsorption-free luminescence lifetime of the <sup>2</sup>F<sub>5/2</sub> state was 1.063 ms. Pumped at 941 nm, the Yb laser generated a maximum output power of 1.04 W at 1.03 and 1.05 μm with a high slope efficiency of 76.4% and a laser threshold of 76 mW. A continuous wavelength tuning over a range of 51.6 nm (1026.4–1078.0 nm) was also achieved. Power scaling was achieved using a 969 nm diode-pumped microchip cavity. A maximum output power of ~9 W was obtained at 1.05 μm with a slope efficiency of 76% and an almost circular laser beam profile.
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