Anti-Hermitian plasmon coupling of an array of gold thin-film antennas for controlling light at the nanoscale.

Open quantum systems consisting of coupled bound and continuum states have been studied in a variety of physical systems, particularly within the scope of nuclear, atomic, and molecular physics. In the open systems, the effects of the continuum decay channels are accounted for by indirect non-Hermitian couplings among the quasibound states. Here we explore anti-Hermitian coupling in a plasmonic system for spatially manipulating light on the nanoscale. We show that by utilizing the anti-Hermitian coupling, plasmonic antennas closely packed within only λ/15 separations can be individually excited from the far field, which are otherwise indistinguishable from each other. This opens a new venue for the nanoscale lightwave control, wavelength multiplexing, and spectrum splitting.