Cascaded energy transfer and enhanced near-infrared emission in visible-pumped Cr and Nd co-doped Yb:YAG

In this study, the energy transfer mechanism in Cr,Nd,Yb:YAG (yttrium aluminum garnet) materials was investigated. Based on the emission/excitation spectra and the temporal evolutions of the donor and acceptor ions in Cr,Nd:YAG, Nd,Yb:YAG, and Cr,Nd,Yb:YAG materials, the role of the cascaded Cr3+→Nd3+→Yb3+ energy transfer was elucidated in terms of Yb fluorescence enhancement. The quantum yield balance among Cr, Nd, and Yb fluorescences was determined by solving rate equations, which utilized parameters such as the lifetimes of Cr3+, Nd3+, and Yb3+ ions and the energy transfer parameters related to these materials. The quantum yield for Yb fluorescence was determined to be 35–81% at a Yb concentration of 1–7 at%.