A Coupled-Dipolar Plasmonic Antenna for Enhanced and Directional Emission from a Single NV Center at the Generalized Kerker Condition

Abstract

Plasmonic antennas are widely used to achieve substantial emission rate enhancement. These antennas suffer from significant absorption losses that preclude the observation of Kerker conditions in such systems. The perfect balancing of the Mie-scattering moments in an antenna at the generalized Kerker condition provides radiation directionality to its far-field scattering pattern and zero absorption losses, a situation not achievable for a plasmonic system. Here, using both theoretical and computational approaches, the superposition of Mie-scattering moments induced by coupling two individual silver (Ag) cylinders in a coupled-dipolar plasmonic antenna is discussed. This results in the balancing of multipolar moments to a large extent with unidirectional scattering and hence the generalized Kerker condition in a plasmonic system. By placing a nanodiamond-based single NV- center in the plasmonic gap-cavity formed between the two Ag cylinders, >300 times Purcell enhancement is achieved with improved emission directionality leading to 80% collection efficiency. The proposed coupled-dipolar plasmonic antenna is well suited for generating bright single photon emissions with a GHz emission rate, which is helpful for quantum photonic applications.