Forward and back energy transfer between Cu2+ and Yb3+ in Ca1−xCuSi4O10:Ybx crystals

We report on near-infrared photoluminescence studies in Ca1−xCuSi4O10: Ybx (x = 0.00 − 0.10) polycrystals by means of diffuse reflection, photoluminescence, excitation spectra and luminescence decay analysis. The samples show intense absorption bands at 540, 630, 800 nm due to Cu2+: 2B1g→2A1g, 2Eg, 2B2g transitions. Under the excitation, the samples show efficient photoluminescence at 920 nm from Cu2+ and 1007 nm from Yb3+, respectively. With increasing of Yb concentration, the PL intensity of Yb3+ increases obviously, while that of the Cu2+ decreases slightly. A probable energy transfer mechanism can be proposed on the basis of decay curves and temperature-dependent photoluminescence spectra.