Spectroscopic investigation and crystal field modelling of Dy 3+ and Er 3+ energy levels in yttrium aluminium

High resolution (0.04 cm −1 ) absorption spectra of Dy 3+ -doped YAl3(BO3)4 (YAB) single crystals were measured by Fourier transform spectroscopy in the spectral (2000–23 000 cm −1 )a nd temperature (9–300 K) ranges. Samples with nominal 1 and 4% Dy/ Ym olar ratios were studied. Dy 3+ transitions from the 6 H15/2 ground state to the 6 H13/2, 6 H11/2, 6 H9/2 + 6 F11/2, 6 H7/2 + 6 F9/2, 6 H5/2, 6 F7/2, 6 F5/2, 6 F3/2 ,a nd 4 F9/2 excited states were analysed. A small (∼3. 3c m −1 ) splitting between the first two sublevels of the 6 H15/2 ground manifold was detected. The experimentally determined energy levels were fitted with a single-ion Hamiltonian and the crystal-field parameters were obtained. The same procedure was applied to analyse the previously published high resolution spectra of YAB:Er 3+ ,l eading to a reliable unified picture for the two dopants.