Subwavelength High-Q Kerker Supermodes with Unidirectional Radiations

Abstract

We propose and demonstrate subwavelength Kerker supermodes of simultaneous high-Q factors and unidirectional radiation patterns supported by all-dielectric nanoscale resonators. The high-Q quasi-bound supermodes shown recently based on resonance coupling are revisited from another perspective of multipolar expansions, and we discover that the Q-factor enhancement is subtly connected with the processes of multipolar conversions from lower to higher orders, in both negative and positive coupling regimes. We further reveal that, relying on this connection and generalized Kerker effects of interferences among different multipoles, the radiations of the subwavelength high-Q supermodes can be made unidirectional by breaking symmetries of the dielectric resonators, which is of great significance for various nanoscale lasing and sensing related applications.