Metallo-dielectric hybrid antenna for high Purcell factor and radiation efficiency.

Based on multisphere Green's function, we investigate the interaction between a dipole source and a hybrid nanoantenna. The parameter of radiation enhancement factor is introduced to characterize spontaneous emission enhancement and radiation efficiency simultaneously. We revisit the emission of silver dimers in the context of radiation enhancement factor. Then the hybrid of metallic nanoparticles (MNPs) and dielectric nanoparticles are designed for strong enhancement as well as high efficiency. Purcell factor over 2000 and radiation efficiency over 50% are achieved by the hybrid antenna. And Purcell factor above 900 with over 57% radiation efficiency is also reached for broadband operation. Such metallo-dielectric hybrid antenna may find potential applications in bright single photon sources and Raman spectroscopy.