Energy transfer mechanisms between Ce3+ and Nd3+ in YAG : Nd, Ce at low temperature

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Abstract
The energy transfer mechanisms between Ce3+ and Nd3+ are studied at low temperature (T = 4.4 K) in Ce codoped YAG : Nd crystals using selective pulsed dye laser excitation to pump into the first Ce3+ absorption band. Both radiative and nonradiative energy transfers are observed. Ce3+ fluorescence decay curves are measured for various Ce3+ concentrations ranging from 0.003 to 0.02 at. % and typical Nd3+ concentrations used in YAG: Nd laser rods (~ 0.73 and 0.88 at. %). Since no diffusion occurs among Ce3+ ions, the Ce3+ decay curves are fitted according to Inokuti-Hirayama's theory. The best agreement is obtained for a average critical distance R 0 ~ 1.1 nm for dipole-dipole as well as quadrupole-dipole couplings. This means that both couplings contribute to nonradiative Ce3+ → Nd3+ energy transfer in YAG : Nd, Ce crystals for the used concentrations