Dual-Band Metamaterial Absorbers in the Visible and Near-Infrared Regions

Metamaterial absorbers have attracted much attention due to their unique ability to achieve nearly perfect absorption in compact structures. Most of the reported metamaterial absorbers exhibit only one absorption band in a specific frequency range, but absorbers with two or more absorption bands in the visible and near-infrared regions are desired in many applications. Here, we propose and demonstrate a dual-band metamaterial absorber comprising an aluminum film, a silica spacer, and a periodic array of aluminum nanodiscs. The two absorption bands in the visible and near-infrared range are, respectively, attributed to the excitation of a propagating surface plasmon polariton and a localized magnetic polariton in the proposed nanostructure. Large area and high coverage samples of the designed structure were fabricated using a simple and cost-effective colloidal lithography nanofabrication method. We show that the positions of the absorption bands can be separately adjusted by changing the diameter or the lattice constant of the aluminum nanodiscs on the top of the metamaterial absorbers. Our design of compact and efficient absorbers would find great utility in a variety of applications including filters, sensors, solar cells, thermal emitters, and imaging devices.