Dual-band unidirectional reflectionlessness at exceptional points in a plasmonic waveguide system based on near-field coupling between two resonators.

Dual-band unidirectional reflectionlessness at exceptional points is investigated theoretically in a non-Hermitian plasmonic waveguide system, based on near-field coupling by using only two resonators. The system consists of a metal-insulator-metal waveguide end-coupled to two nanohole resonators. The reflectivity for the forward (backward) direction is ∼0 (∼0) at frequency 205.20 THz (194.56 THz), while for the backward (forward) direction it is ∼0.76 (∼0.78). Moreover, the quality factors of the dual-band unidirectional reflectionlessness for forward and backward directions can reach ∼132 and ∼137, respectively.