Enhancement of photoluminescence intensity of erbium doped silica containing Ge nanocrystals: distance dependent interactions.

Photo-physical processes in Er-doped silica glass matrix containing Ge nanocrystals prepared by the sol-gel method are presented in this article. Strong photoluminescence at 1.54 μm, important for fiber optics telecommunication systems, is observed from the different sol-gel derived glasses at room temperature. We demonstrate that Ge nanocrystals act as strong sensitizers for Er(3+) ions emission and the effective Er excitation cross section increases by almost four orders of magnitude with respect to the one without Ge nanocrystals. Rate equations are considered to demonstrate the sensitization of erbium luminescence by Ge nanocrystals. Analyzing the erbium effective excitation cross section, extracted from the flux dependent rise and decay times, a Dexter type of short range energy transfer from a Ge nanocrystal to erbium ion is established.