Nd3+→ Cr4+ energy transfer in co-doped Nd,Cr:Y3Al5O12 garnet transparent ceramics

Herein, we quantitatively analyze the Nd³⁺ → Cr⁴⁺ energy transfer efficiency in the co-doped transparent ceramic YAG host and determine that it can be maintained at less than a 20 % loss of Nd³⁺ excited states when the Cr⁴⁺ absorption coefficient at 1064 nm is less than 1.0 cm⁻¹. Furthermore, we conclude that the energy transfer mechanism can be fully accounted for on the basis of classic Förster-Dexter theory, as the transfer efficiency deduced from the emission kinetics is consistent with that independently determined from the spectroscopic properties of Cr⁴⁺ absorption and Nd³⁺ emission. Systematic studies of trends for Cr³⁺ → Cr⁴⁺ conversion are reported as a function of the oxygen annealing temperature, initial Cr³⁺ concentration, and incorporation of divalent (Mg²⁺ and Ca²⁺) charge compensators. Lastly, no effect of energy migration among the Nd³⁺ ions was observed.