Up-conversion mechanisms in Pr3+-doped Bi4Ge3O12 crystal

We investigated the up-conversion mechanisms leading to RGB emission in a p r(3+) : Bi4Ge3O12(BGO) crystal excited to the D-1(2) level. Sequential two- photon excitation process (STEP) was found to be the dominant mechanism to populate the fluorescing P-3(0) and P-3(1) levels, also with a minor contri bution of energy transfer up-conversion (ETU). Furthermore, the initial sta te of the excited state absorption (ESA) in the STEP was proven To be the H -3(6) level with a dual-wavelengths excitation experiment. This excitation scheme provides significant enhancement of fluorescence intensity compared with the single-wavelength excitation. (C) 2000 Elsevier Science B.V. All r ights reserved.