Control of Far-Field Coupling in Bipartite Nanodisk Arrays

The optical response of a pair of nanostructures is shaped by the interactions between their localized electromagnetic modes. These are significant only at subwavelength distances and are hence governed by near-field coupling, which limits the range and tunability of emergent phenomena. In contrast, periodic arrays support extended modes known as lattice resonances. When two identical arrays are combined into a bipartite configuration, their lattice resonances interact through far-field coupling, exhibiting nonmonotonic behavior where both the strength and the sign of the interaction depend on their relative positioning. Exploiting this effect, we demonstrate that the optical response of bipartite arrays of silver nanodisks can be precisely engineered by adjusting their relative displacement. To that end, we analyze four different configurations supporting super- and subradiant lattice resonances, noninteracting coexisting modes, and out-of-plane polarized resonances. These findings highlight the rich physics of lattice resonance interactions and offer a versatile approach to designing advanced nanophotonic devices.