Rate and efficiency of spontaneous emission in metal-clad microcavities

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Abstract
In this article, we report experimental results on the control of spontaneous emission from sources embedded within metal-clad microcavities. The microcavity samples consist of an Eu3+ doped emissive monolayer embedded with a planar dielectric slab, bounded by a silver film on each side. We investigate the effect of both the cavity thickness and the location of the emissive monolayer within the cavity on the spontaneous emission rate of the emitters, observing both enhancement and inhibition. By varying the thickness of one of the silver films we also investigate the role of the reflectivity of the mirrors of the cavity on the control of spontaneous emission. In addition to the emission rate, results are presented on the spatial distribution of the emitted radiation. We find good agreement between our experimental results and those predicted by a classical theory over a large range microcavity structures. This agreement allows us to assess the contribution of the decay mediated by the electromagnetic modes of the cavity and the intrinsic nonradiative decay to the spontaneous emission rate. We then compare the ability of metal-clad and hybrid (one metal mirror and one distributed Bragg reflector) microcavity designs to optimize the efficiency of radiative emission. We show that enhancements, due to the increased confinement of the electromagnetic modes supported by the metal-clad microcavities, can be sufficient to overcome the loss associated with the absorption in the metal layers. We discuss the implication these results may have for device design.