Modification of the spontaneous emission rate of Eu³⁺ ions embedded within a dielectric layer above a silver mirror

We investigate the spontaneous emission rate of Eu³⁺ ions in an asymmetric microcavity. The cavity consists of a thin dielectric layer bounded on one side by silver and on the other by air. Samples were constructed using the Langmuir-Blodgett technique, the emitters being incorporated as a single monolayer within the microcavity. This technique allowed both the cavity thickness and the position of the emitters within it to be controlled to one monolayer (≈2.6 nm). Measurements are presented of the spontaneous emission decay rate as a function of both the dielectric layer thickness and the position of the emitters within the layer. We find good agreement between our data and a classical model. The model allows us to investigate the role of the electromagnetic modes of the microcavity in controlling the spontaneous emission decay rate of the emitters. In particular, we are able to evaluate the contribution each of the modes makes to the decay. We discuss the implication these results may have in increasing the photoluminescence efficiency from microcavity based emissive devices.