Polarized laser spectroscopy and crystal-field analysis of Er3+ doped CaGdAlO4

A single Er3+ centre in CaGdAlO4:Er3+ has been identified to have C-4v symmetry from polarized laser selective excitation. This is consistent with isovalent substitution of the Er3+ ions for host crystal Gd3+ ions. Using both optical and infrared absorption and polarized laser excited fluorescence, 59 crystal-field energy levels and their wavefunction symmetries have been identified and used to perform comprehensive single electron crystal-field analyses for the Er3+ ion centre. For excitation of the F-4(9/2) multiplet, blue and green upconversion fluorescence is observed. Self-absorption dips recorded in upconversion excitation spectra are indicative of the presence of radiative energy transfer processes.