Resonance-based metamaterial in the shallow sub-wavelength regime: negative refractive index and nearly perfect absorption

Thi Trang Pham, Hoang Tung Nguyen, Dac Tuyen Le, Ba Tuan Tong, Thi Giang Trinh, Van Tuong Pham and Dinh Lam Vu

Abstract

The research on magnetic resonances in typical meta-atoms has led to the discovery of electromagnetic metamaterials (MMs). These new materials played a crucial role in achieving extraordinary phenomena as well as promised potential applications. In this paper, we numerically and experimentally investigated two different MM effects: the absorption and the negative refraction, which induced by magnetic resonances in a symmetric structure. The meta-atom sandwich model that includes two parallel flat rings separated by an insulating slab was designed. Firstly, three resonances in sub-wavelength range were demonstrated, revealing the negative permittivity and permeability effects. Notably, negative refractive index (NRI) was gained at the third-gap resonance, resulting from superposition of the rest of the electric resonance and the magnetic one accompanied by multi-plasmon. Moreover, the manipulation of the structural parameters could control the NRI behavior and, interestingly, a nearly perfect absorption peak arises in shallow sub-wavelength regime