Nonequivalent Yb3+ centres in Y1-xYbxAl3(BO3)4 laser crystals

The absorption spectra of nonlinear laser crystals Y_1-xYb_xAl₃(BO₃)₄ grown from bismuth—lithium—molybdate and potassium—molybdate solution—melts are comparatively studied by high-resolution Fourier spectroscopy. The differences observed in the fine structure of the absorption spectra are correlated with the variations in the solution—melt composition and in the concentrations of bismuth and molybdenum impurities in the crystals. It is shown that the concentration of the molybdenum impurity (the main factor hindering lasing in the UV spectral region) in the single crystals grown from the bismuth—lithium—molybdate solutions is more than an order of magnitude smaller than in the crystals grown using the potassium—molybdate solution—melt. The described method can be used for express analysis of the quality of UV laser crystals and for improving the solution—melt technologies of growth of laser crystals and crystals used for generation of the fourth harmonic of Nd:YAG laser radiation.