Abstract: Single crystals of different ytterbium-doped yttrium alumium tetraborate (Yb:YAl₃(BO₃)₄,Yb:YAB)
were grown by the flux method. The absorption and fluorescence spectra of Yb³⁺:YAl₃(BO₃)₄ crystals were measured. In the absorption
spectra, there is only one absorption band at 976nm, which is suitable for InGaAs diode laser pumping. In the fluorescence spectra, there is one
fluorescence peak at 1.03μm. The thermal expansion presents strong anisotropic character, and the thermal expansion of c-direction is about 3.5
times than that of a-direction. The relationship between thermal properties and crystal structure was discussed. 4.3W output power at 1040nm can be obtained
when pumped by 11W fibre-coupled laser diode at 977nm, and the slope efficiency is 48%; At the same experiment condition, 1.1W cw green output can be achieved,
with a diode-to-green optical conversion efficiency of 10%.

Key words: laser crystal, self frequency-doubling, spectrum property