Analysis of a bidirectional metamaterial perfect absorber with band-switchability for multifunctional optical applications

Metamaterial perfect absorbers (MPAs) have been widely studied due to their distinctive tunable electromagnetic properties. Conventional MPAs mostly focus on realizing perfect absorption in a single direction, which leads to their limitations for various practical applications. We propose a bidirectional MPA with the ability of switching the ultra-wideband and dual-narrowband absorption. An inversion algorithm is applied to extract the normalized impedance of the absorber for explaining the physical mechanism. Simulation results clearly manifest that the average absorptivity of 93.8% and 99.5% could be achieved both over an ultra-wide spectral range of 1200 nm and at the specific wavelengths of 589 nm and 1097 nm with polarization independence and angle insensitiveness, which are led by the multiple excitations of different resonance modes induced by the metal–insulator-metal (MIM) Fabry-Perot (F-P) cavities. Our results are desirable for the integration of multiple optical applications such as energy harvesting, thermal emission, perfect cloaking and nanoparticle detecting.