High-efficiency of infrared absorption by using composited metamaterial nanotubes

We develop and compare four designs of metamaterial-based infrared (IR) absorbers, which are composed of a textured Au layer and a bottom Au layer on a Si substrate to form IR absorbers. They are absorbers with concentric circle nanotubes (CCNs), hollow square nanotubes (HSNs), metal-insulator-metal concentric circle nanotubes (MIM-CCNs), and metal-insulator-metal hollow square nanotubes (MIM-HSNs). The design of the absorber with a MIM structure can improve the absorption efficiency and the corresponding quality factor (Q-factor) compared to that without a MIM structure. By using the IR absorber with MIM design, the highest absorption is 100% with a Q-factor of 27 for MIM-CCN and a Q-factor of 32 for MIM-HSN, while the maximum Q-factor is 47 for MIM-CCN and 42.7 for MIM-HSN although the corresponding absorption is 62% for MIM-CCN and 65% for MIM-HSN, which are enhanced 1.5-fold and 1.7-fold compared to those without MIM designs, i.e., CCN and HSN designs, respectively. This creates the possibility for the use of such devices with high-efficiency IR applications.