Tunable unidirectional reflectionless propagation in non-hermitian graphene-based metasurface

Abstract In this paper, we propose an graphene-based non-Hermitian metasurface and numerically investigate a tunable unidirectional reflectionless phenomenon for the THz region. The metasurface is composed of cascaded square graphene patch and its complementary structure separated by a thin dielectric layer. By simply selecting the thickness of the dielectric layer, the backward reflection for our structure is zero, and the corresponding forward reflection is about 35% at 31.15 THz. The coupled mode theory and the non-Hermitian scattering matrix are used to show that unidirectional reflectionless is responsible for the exceptional point. The Fermi energy of the graphene can actively tune the one-way zero reflection frequency. By varying the Fermi energy from 0.56 eV to 0.64 eV, a spectral blue shift of one-way zero reflection from 29.6 THz to 32.2 THz is obtained, maintaining the same structure. We believe that the proposed scheme will provides more flexible opportunities to realize unidirectional invisibility, diode-like device, on-chip sensors and filters.