Ho-doped yttrium aluminum perovskite Ho:YAP (Ho:YAlO3) is a promising material for the construction of high-power lasers, operating in 2.1 µm spectral region. We present the dependencies of key spectroscopic properties on Ho-doping concentration and on Ho:YAP crystal orientation. Three Ho:YAP crystals with various Ho-doping concentrations were grown by Czochralski method: 0.26 at.% Ho/Y, 0.45 at.% Ho/Y, 1.05 at.% Ho/Y. The uncoated samples were prepared in the form of polished wafers 2.8 mm thick with diameter up to 45 mm and in the form of an oriented cuboid (6 x 7 x 8mm). The detailed polarization resolved absorption spectra were measured with a high resolution in the range from 300 up to 6500 nm. The polarization resolved emission spectra were investigated in the range from 500 up to 3500 nm. The 5I7 upper-laser-level lifetime was measured using a confocal method. From the obtained data, the absorption cross-sections in all investigated spectral ranges were determined and the Judd-Ofelt analysis was performed. It was found that the Ho-doping concentration significantly influenced mainly the upper 5I7 laser level lifetime, which drops from 5.8 ms for the lowest doping to 4.7 ms for the highest tested Ho-doping. Using the oriented Ho:YAP cuboid (1.05 at.% Ho/Y), laser emission reaching the quantum limit under Tm-fibre excitation (1939 nm) was reached. By an appropriate choice of the Ho:YAP crystal orientation and reflectance of the laser output coupler, it was possible to achieve laser action at wavelengths of 2083, 2102, 2118, and 2130 nm, or to generate laser radiation at several wavelengths simultaneously.
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