Optical energy transfer in rare earth doped silica gels

In this work we study the time dependence of the Eu3+ luminescence from the 5D0 state in a silica gel. Sample was doped with a 0.2% Eu/Si molar ratio and fully densified by heat treatment at 1050°C. The 5D0 <=> 7F0 transition shows a different lineshape in absorption and luminescence at temperatures lower than room temperature. This effect is due to efficient energy transfer among Eu3+ ions with different environments. Energy transfer is studied by detecting the resonant and out of resonance decay profile, after selective excitation within the 7F0 -> 5D0 absorption line. The transfer rate is comparable with the radiative decay rate. At low temperature luminescence occurs mainly from the ions in sites having the 5D0 -> 7F0 transition frequency in the low tail of the inhomogeneous line.