Derivation of a semi-analytical method for designing tunable metamaterial absorbers

Metamaterial perfect absorbers (MPAs) are usually designed through two main procedures in combination with an optimization method: numerical simulation and circuit modeling. In this article, we propose a new semi analytical method to design the MPAs. A double-layer micro-strip resonator absorber with a broad bandwidth is designed and analyzed carefully using full-wave numerical simulation combined with a genetic algorithm. The mechanism of the absorption is analyzed carefully, and it is shown that the broadband absorption is caused by the coupling between surface plasmon and Fabry-Perot (FP) resonances in different modes. Also, the role of the localized surface plasmon in coupling FP resonances through subwavelength slits is clarified based on the special shape of the micro-strip resonators. Using the obtained results, a new semi-analytical method is proposed for designing MPAs. This new method is a combination of a theoretical method derived based on the analyzed absorber mechanism and a local search genetic algorithm. The generalization of this method is investigated for different dielectrics, metals, resonator layer numbers, and in different objective frequency ranges. Results show that the method can be used in designing both broadband and multiband absorbers. Also, the method is used to design absorbers using square resonators. These resonators are polarization insensitive and support the same resonances as the micro-strips. The designed micro-strip and square resonator absorbers show favorable performance for both TE and TM polarization. We also showed this method and the proposed theoretical formulas can shorten the design process of the absorbers.

Automated summary

In this article, a new semi-analytical method is proposed to design metamaterial perfect absorbers (MPAs) that can be used for designing both broadband and multiband absorbers. The method is based on the analysis of the absorption mechanism and a local search genetic algorithm, and it shows favorable performance for both TE and TM polarization.