Modified spontaneous emission in erbium-doped SiO2 spherical colloids

Spherical SiO2 colloids with two different diameters (175 nm, 340 nm) were doped with erbium at different concentrations. The spheres show sharply pea ked photoluminescence centered at 1.535 mum, due to intra-4f transitions in Er3+. From measurements of the Er decay rate for different Er concentratio ns the decay rate of isolated Er ions (i.e., in absence of concentration qu enching) was determined for the two colloid diameters. The data were compar ed to spontaneous emission rates derived from calculations of the local opt ical density of states in the colloids. The calculation predicts a large di fference in the spontaneous emission rate for both colloid sizes (61 vs 40 s(-1)), in perfect agreement with the measured data. (C) 2001 American Inst itute of Physics.