Unidirectional reflectionless propagation of near-infrared light in heterogeneous metamaterials

Compared with homogeneous metamaterials, realizing unidirectional reflectionlessness (UR) is relatively chal-lenging for heterogeneous metamaterials. Herein, we study UR based on the near field phase coupling mode in a silver/gold heterogeneous metamaterial system using the finite-difference time-domain (FDTD) and scattering matrix theory. The results show that unidirectional reflectionless propagation can be effectively controlled by appropriately adjusting the distance (the phase) between the two heterogeneous resonators. At the same time, the unidirectional perfect absorber (UPA) can be obtained near EPs. What's more, the change in the eigenvalue of the scattering matrix can clearly describe the physical mechanisms for the evolution of UR and UPA. In particular, the analytical calculation results are consistent with the numerical simulation conclusions. These results potentially have important implications for achieving nanoscale unidirectional devices.