Polycrystalline Ho: LuAG laser ceramics: Fabrication, microstructure, and optical characterization

Ho:Lu3Al5O12(LuAG) transparent ceramics are potential 2m eye-safe laser materials. Polycrystalline 0.8at.% Ho:LuAG ceramics with high optical quality were successfully fabricated by solid-state reactive sintering of high-purity oxide powders. The microstructure, the optical transmission, the spectrum characteristic, and the laser performance were investigated in this paper. The average grain size of Ho:LuAG ceramics vacuum sintered at 1830 degrees C for 30hour is about 14m. The in-line transmittance of the sample is measured to be 81.7% and 82.0% at 1000 and 2250nm, respectively. The absorption and the emission cross sections are calculated to be 0.88x10(-20)cm(2) at 1906nm and 1.26x10(-20)cm(2) at 2094nm. Using a thulium-doped yttrium-lithium-fluoride (Tm:YLF) laser with the central wavelength of 1907.5nm as the pump source, 2.67W continuous wave (CW) laser operation at 2100.74nm was obtained with a slope efficiency of 26.5%. The beam quality factor M-2 was calculated to be 1.1, which indicated nearly diffraction-limited beam propagation and the laser was the fundamental TEM00 Gaussian mode.