A general equivalent circuit model for plasmonic metasurface broadband absorbers

Broadband absorbers show great potential in many scientific and technical applications. For most practical applications, the absorption bandwidth is one of the most substantial metrics. The emerging metasurfaces show strong and versatile capabilities in controlling the absorption, reflection, and propagation of electromagnetic waves. In this paper, we have proposed and investigated broadband metasurface absorbers by introducing a circuit model. Firstly, we have compared the results of the proposed method with the existing simulation results of the circular gold resonators and those of numerical simulation based on the finite element method (FEM). Secondly, we investigated and compared the experimental data of TiN metasurface broadband absorber with those of the proposed circuit model. The results of the circuit model have a good agreement with those of the measured data and the outcomes of the full-wave numerical simulation based on the FEM. In addition to reducing the calculation time, our proposed method requires less memory in comparison to full-wave simulations. The proposed method is simple yet general and can be applied to the design and the simulation of other sub-wavelength structures in the broad frequency range including terahertz (THz) and visible regions.