Analytical investigation of unidirectional reflectionless phenomenon near the exceptional points in graphene plasmonic system

We propose a two-dimensional array made of a double-layer of vertically separated graphene nanoribbons. The transfer matrix method and coupled mode theory are utilized to quantitatively depict the transfer properties of the system. We present a way to calculate the radiative and the intrinsic loss factors, combined with finite-difference time-domain simulation, conducting the complete analytical analysis of the unidirectional reflectionless phenomenon. By adjusting the Fermi energy and the vertical distance between two graphene nanoribbons, the plasmonic resonances are successfully excited, and the unique phenomena can be realized at the exceptional points. Our research presents the potential in the field of optics and innovative technologies to create advanced optical devices that operate in the mid-infrared range, such as terahertz antennas and reflectors.