Multiple-Band Ultra-Thin Perfect Metamaterial Absorber Using Analogy Split-Ring Resonators

This paper presents a kind of perfect metamaterial absorber that can achieve multiple-band near-perfect absorption. The basic cell of the device is designed by using an analogy split-ring resonator (ASRR), an insulating dielectric sheet, and a continuous metallic board. Three discrete absorption peaks with narrow bandwidths and high absorption rates are obtained. The ratios of the dielectric sheet thickness to the wavelengths of the three absorption peaks are respectively 1/100, 1/59, and 1/43, which are all smaller than prior triple-band absorption devices. With the aid of the field distributions, the mechanism of the device is investigated. Results also demonstrate that the device performance can be controlled by the parameters (in particular of the length) of the ASRR. Based on this, a six-band terahertz metamaterial absorber is designed via simply stacking two different dimensions of ASRRs. We found that the dual-layer structure can exhibit six narrow-band absorption bands, each of which has the absorption of over 90%. The mechanism of the six-band light absorber is caused by the combination of two sets of three different modes of the two layers.