FEM Approach to the Robust Design of a Graphene-Based 3D Structure for THz Devices

In this work, we propose the investigation of the terahertz performance of a graphene-based multilayer metasurface, assessing the reflection and absorption capability of the considered structure in the view of designing a robust passive device for the manipulation of THz radiation. In particular, we develop a Finite Element Method (FEM)-based model of a patterned SiO2/gold/PMMA/graphene/PMMA multilayer device and use it to assess the electromagnetic response in the THz frequency range of the proposed metamaterial. The structure has a SiO2 substrate, patterned with straight grooves and covered by a nanometric thin film of gold. On top of the cavities is a PMMA/graphene/PMMA sandwich layer. By considering an incident wave on the top surface, the absorption enhancement provided by the addition of the graphene layer is assessed. Further, the impact of the patterning layout, i.e. the grooves' height variation, on the THz power transmission, reflection, and absorption of normally incident EM waves is investigated. The FEM model provides the ideal tool for the assessment of the device sensitivity to the design parameters, allowing the design centering in the most robust nominal solution.