Optical spectroscopy of Pr3+ in M+Bi(XO4)2, M+ = Li or Na and X = W or Mo, locally disordered single crystals

Abstract

NaBi(WO4)(2) (NBW), NaBi(MoO4)(2) (NBMo) and LiBi(MoO4)(2) (LBMo) single crystals grown by the Czochralski technique have been doped up to a praseodymium concentration of [Pr] approximate to 1 x 10(20) Cm-3 in the crystal. 10 K polarized optical absorption and photoluminescence measurements have been used to determine the energy position of 32, 39 and 36 Pr 3, Stark levels in NBW, NBMo and LBMo crystals, respectively. These energy levels were labelled with the appropriate irreducible representations corresponding to a C-2 local symmetry of an average optical centre. Single-electron Hamiltonians including free-ion and crystal field interactions have been used in the fitting of experimental energy levels and in the simulation of the full sequence of the 4f(2) Pr3+ configuration. 300 K absorption spectra of different (2S+1)LjPr(3+) multiplets were determined and used in the context of the Judd-Ofelt theory and for the calculation of the D-1(2)-related emission cross sections of this average Pr3+ centre. Non-radiative electron relaxation from the P-3(0) level feeds the D-1(2) multiplet. This latter level efficiently decays radiatively to the ground H-3(4) multiplet but still there is a significant rate of radiative decay to the D-1(2) --> F-3(3) praseodymium laser channel. For [Pr] greater than or equal to 2 x 10(19) cm(-3), non-radiative electric dipole-dipole Pr pair energy transfer limits the radiative yield.