Numerical investigations in broadside coupled graphene terahertz metamaterials for optimized sensing

Abstract

Engineered subwavelength two-dimensional (planar) materials, also termed as metamaterials/ metasurfaces, derive their properties from the geometry and shape of the constituent resonators and provides large range of potential applications. The metamaterials’ responses revolve around the resonances but the radiative losses in metamaterials are the main cause of concern. In this context, graphene, a single layer of hexagonally arranged carbon atoms, has attracted immense interests due to its excellent electronic and optical properties, such as high electron mobility and dynamically tunable conductivity. It provides low propagation losses and active tuning of resonances through variation in graphene Fermi energy. Planar coupling in graphene metamaterials has been exploited by many researchers but it has its own limitations such as small surface area for effective interactions resulting in reduced near-field interaction. To enhance the light-matter interaction, broadside coupling between the graphene resonators have been exploited in this work. Broadside coupling provides large light-matter interaction area and leads to a strong redistribution of energy inside the cavity formed between the two graphene layers. In this work, we have theoretically investigated the effect of such broadside coupling in bilayer graphene metasurfaces. Broadside coupling in bilayer graphene metamaterials can provide compact, miniaturized, and low loss THz devices to actualize ultrasensitive sensors, modulators, slow light devices, nonlinear cavity, active multiband filters, and several other potential applications.