Silicon nanocluster sensitization of erbium ions under low-energy optical excitation

The sensitizing action of amorphous silicon nanoclusters on erbium ions in thin silica films has been studied under low-energy (long wavelength) optical excitation. Profound differences in fast visible and infrared emission dynamics have been found with respect to the high-energy (short wavelength) case. These findings point out to a strong dependence of the energy transfer process on the optical excitation energy. Total inhibition of energy transfer to erbium states higher than the first excited state (I-4(13/2)) has been demonstrated for excitation energy below 1.82 eV (excitation wavelength longer than 680 nm). Direct excitation of erbium ions to the first excited state (I-4(13/2)) has been confirmed to be the dominant energy transfer mechanism over the whole spectral range of optical excitation used (540 nm-680 nm). (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4712626]