Radiative Enhancement of Plasmonic Nanopatch Antennas

Efficient light manipulation at subwavelength scale is of great interest for solar energy conversion, optical sensing, and nanophotonic devices. Recently, plasmonic nanopatch antennas (PNAs), which consist of plasmonic nanoparticles and metal films with thin layers of dielectric spacers sandwiched between them, have shown promise for directing and enhancing radiation from the dipole emitters at the PNAs. Herein, we apply finite-difference time-domain simulations to comparatively study the radiative enhancement of a series of PNAs consisting of Ag nanoparticles with different geometries, i.e., nanosquare, nanotriangle, nanorod, and nanodisk. We find that the shape of the Ag nanoparticles influences the resonant wavelength of the plasmonic waveguide modes in the spacers, the enhancement of localized electric field, and multiple aspects of the radiation, including spontaneous emission rate, quantum efficiency, and radiative enhancement factor. Nanodisk-based PNAs exhibit both high quantum efficiency (~0.74) and radiative enhancement factor (>20), while nanotriangle-based PNAs show remarkable spontaneous emission rate enhancement (>2500). Furthermore, we examine the effects of dipole emitter locations on the radiative properties. Our results pave the way towards the rational design of PNAs for the optimal plasmonic enhancement of light emission for targeted applications.