Multi-band near-perfect absorption via the resonance excitation of dark meta-molecules

Abstract

We numerically study a multi-band absorption based on electromagnetic-induced-transparency effect of metamaterial. By exploiting the coupling between bright and dark plasmonic modes of cut-wire triplet, which consists of a vertical wire and two horizontal wires, a dual-band absorption is realized at 243 and 266 THz. Then, the absorber structure is improved by adding two new horizontal wires which play role as second dark meta-molecules. Due to the dark-dark coupling, another absorption band arises so that a triple-band absorption is created at 240, 250 and 264 THz. The role of interaction between dark meta-molecules in triple-band absorption is investigated, revealing a specific non-monotonic characteristic of the second absorption peak. Finally, the influence of incident angle of EM wave on multi-band absorbers shows that the absorption of lowest frequency peak is robust while those of higher frequency peaks are strongly weaken with increasing of the incident angle. (C) 2015 Elsevier B.V. All rights reserved.