Analysis of a Bowtie Nanoantenna for the Enhancement of Spontaneous Emission

eA 2-D metallic bowtie nanoantenna, consisting of two nearby metallic nanotriangles and containing a molecule within the gap, is studied for the enhancement of a single emitter's spontaneous emission. For simplicity, a transverse-magnetic model is used for simulation and a set of new surface integral equations is developed for the calculation. The process of spontaneous emission is simply divided into two stages: the first stage is the excitation of the emitter irradiated by an incident plane wave and the second is the emission of the excited emitter. For the latter, the excited emitter is modeled as an electric dipole to interact with the nanoantenna. The results show that a metallic bowtie nanoantenna behaves as a nanolens as well as a polarizer to provide a strong local electric field with a polarization parallel to the axis of the bowtie in the gap for the emitter's excitation, and its quantum yield exhibits a function of a low-pass filter as well as an orientizer for the emitter's emission.