Sensitizing effect of Yb3+ on near-infrared fluorescence emission of Cr4+-doped calcium aluminate glasses

We have demonstrated that an efficient energy transfer takes place from Yb3+ to Cr4+ in calcium aluminate glasses. Yb3+ improves excitation efficiency at around 980 nm, enhancing emission intensity of Cr4+ fluorescence at 1.2-1.6 mu m. Nonradiative energy transfer via electric dipole-dipole interaction between ytterbium and chromium ions was found to be dominant over radiative Yb3+ --> Cr4+ energy transfer. A diffusion-limited energy transfer mechanism well explains the decay behavior of Yb3+/Cr4+-codoped glasses. This codoping scheme may be applicable to other Cr4+-containing crystals and glasses.