The epsilon-mu-near-zero (EMNZ) device realized by a novel structure of air gap ring at microwave frequency

Abstract

Abstract The epsilon-and-mu-near-zero (EMNZ) medium, as a kind of zero-refractive-index material, has broad application perspectives. In general, there are three main methods to realize the EMNZ phenomenon based on conventional metamaterials such as fishnet metamaterials, Dirac-like cone-based metamaterials, and doped ENZ mediums in the full frequency range. However, the above EMNZ metamaterials have complex structures and stringent process requirements, and the development of mature engineering applications outside the laboratory is still a long way off. Herein, a novel, simple and stable air gap ring compatible with the EMNZ medium based on the doping method has been proposed to mitigate the above constraints. The proposed structure is composed of a set of nested metal boxes and an air gap ring formed between the nested metal boxes. By changing the size of the cross-sectional area of the perfect electric conductor (PEC) doped into an ENZ medium to manipulate the air gap ring in the nested metal boxes, the effective magnetic permeability of the whole structure can be adjusted. Finally, the equivalent EMNZ medium characterized by a simple structure can be realized in the microwave band. Thus, the proposed novel air gap ring device exhibits promising potential for broad applications such as frequency selection, impedance regulation, super-coupling, and power splitting.