Strongly modifiable decay and angle-dependent light intensity for an atom near active plasmonic structures: A macroscopic QED study

Tunable plasmonic structures provide the possibility to actively modify the radiation from atoms through electromagnetic coupling. In this paper, we investigate the decay and radiation behavior of an atom near a dielectric nanosphere with conductive surface within the framework of macroscopic quantum electrodynamics. The electromagnetic fields including the losses in the materials can be taken as fundamental excitations which interact with the atom through a transition dipole. Both weak and strong coupling regimes have been investigated. The decay rate and the angle-dependent light intensities indeed strongly depend on the parameters of the system, i.e., the position and orientation of the dipole, the geometric size, and the surface conductivity, providing the opportunity of artificial control over these quantities. Generalizing the formalism in this paper to other systems, like metamaterials, is straightforward, which we believe may pave a way for future active quantum nanophotonic devices.