Polarization selection rules for the allowed optical transitions in europium-terbium double activated calcium tungstate phosphor

Abstract

The paper is devoted to the problem of the optical anisotropy of the rare-earth ions occupying low-symmetry positions in crystals. The crystal field multiplets arising from LSJ terms of Eu3+ and Tb3+ ions in the crystal field of calcium rungstate scheelite (CaWO4) are analyzed (S-4 Point symmetry). The selection rules, in particular, polarization rules for the allowed electric dipole optical transitions in the electronic shells of the Eu3+ and Tb3+ in CaWO4 host lattice are discussed. Special attention is paid to the study of the angular (polarization) dependence of the two-photon absorption that seems to be. an effective tool for the understanding of the complicated optical pattern, The peculiarities of the anisotropy of the two-photon absorption prove to be specific for each allowed dipole transition in S4 symmetry center. (C) 2004 Elsevier Ltd. All rights reserved.