Extremely asymmetric absorption and reflection near the exceptional point for three-dimensional metamaterial

Abstract

In recent years, particular physical phenomena enabled by non-Hermitian metamaterial systems have attracted significant research interests. In this paper, a non-Hermitian three-dimensional metamaterial near the exceptional point (EP) is proposed to demonstrate extremely asymmetric absorption and reflection. Unlike its conventional counterparts, this proposed metamaterial is constructed with a loss-assisted design. Localized losses are introduced into the structure by combining our technique of graphene-based resistive inks with conventional printed circuit board process. Extremely asymmetric absorption and reflection near the EP are experimentally observed by tuning the loss between split ring resonators in the meta-atoms. Simultaneously, by linking the equivalent circuit model (ECM) with the quantum model, an equivalent non-Hermitian transmission matrix is constructed. We show that tuning the structure parameters of the ECM produces a metamaterial system with EP response. Our system can be used in the design of unidirectional metamaterial absorbers. Our work contributes to future works on the manipulation of EP to develop precision sensing and other applications in the 3D metamaterial platform.