Broadband terahertz absorber with gradient ring resonators based on a discrete spiral topological distribution
Artificial absorbers of electromagnetic energy often use resonant effects to achieve efficient absorption, therefore they often work only in a narrow frequency range. In this work, researchers from China proposed a multi-resonator and multi-layer structure that achieves a broadband absorption. Due to multiple overlapping resonances in the structure, the predicted absorption bandwidth reaches over 80% of the central frequency, where the absorption exceeds 90% of the incident energy. Moreover, the proposed shape of the resonators and their arrangement ensures that the absorber works efficiently with all polarisations of light. The proposed structures are designed for the THz frequency range, and they rely on metallic resonators placed on dielectric substrates.