Tunable localized surface plasmon graphene metasurface for multiband superabsorption and terahertz sensing

We propose a plasmon induced tunable metasurface for multiband superabsorption and terahertz sensing. It consists of a graphene sheet that facilitates perfect absorption where the graphene pattern at the top layer creates an enhanced evanescent wave that facilitates the metasurface to work as a sensor. The modelling and numerical analysis are carried out using Finite Element Method (FEM) based software, CST microwave studio where a genetic algorithm (GA) is used to optimize the geometric parameters, and metasurface tunability is achieved via an external gate voltage on the graphene. By exploiting graphene's tunable properties we demonstrate a multiband superabsorption spectra having a maximum absorption of 99.7% in a frequency range of 0.1-2.0 THz that also maintain unique optical performance over a wide incidence angle. Further results show how the superabsorber can be used as a sensor, where the resonance frequency shifts with the refractive index of the surrounding environment. (C) 2019 Elsevier Ltd. All rights reserved.