Luminescent properties and energy transfer processes of co-doped Yb-Er poly-crystalline YAG matrix

A poly-crystalline YAG matrix was obtained through the precipitation method; this matrix was single and co-doped with ytterbium and erbium ions, i.e., Yb:YAG, Er:YAG and Yb,Er:YAG. It is found that the measured luminescent properties are similar to those reported for a mono-crystal YAG matrix. In addition, by studying the energy transfer processes in co-doped samples, it is shown that at high erbium concentrations the red emission is enhanced through an up-conversion process that takes place from the 4I13/2 to the 4F9/2 state of erbium ions. This enhanced red emission becomes comparable in intensity to the observed green emission and occurs by pumping at 800 nm through a back energy transfer process.