Topological flexible metamaterials with isotropic dual-frequency terahertz-band absorption

Abstract

This study demonstrates an isotropic flexible absorptive metamaterial structure for terahertz wave bands based on topological-optimization design. One rotationally symmetric absorbing element consists of a polarization-sensitive metamaterial cell arranged with a counterclockwise topology. A flexible topological metamaterial absorber is formed from crystalline elements through an infinite periodic arrangement using Floquet’s theorem. This artificial material achieves dual-frequency absorption with peak absorptions of 94% and 99.9% at 0.136 and 0.143 THz, respectively. The independent polarization angle of the two absorption peaks exceeds 45°under an oblique incident-wave process operation and in bending measurement, which indicate polarization isotropy. The equivalent electrical thickness corresponding to the minimum resonance point is close to one-ninth. The proposed ultra-thin flexible artificial material not only possesses perfect conformity with complex surfaces but also achieves larger angle electromagnetic absorption. The study results can present this material a potential candidate for polarized manipulation in electromagnetic stealth and electromagnetic control in the terahertz technology.