Experimental Observation of Ultrafast THz Absorption Modulation in a Graphene-Based Metasurface

Graphene, a two-dimensional material made of carbon atoms arranged in a honeycomb lattice, has attracted enormous attention since its experimental realization in 2004 due to its unique mechanical, thermal, electrical and optical properties. Particularly in the THz spectrum, graphene predominantly exhibits a Drude-like response due to its easily generated and controlled free carriers and therefore is considered a suitable platform for dynamically tunable metasurface components. Such an example, are the so called thin film absorbers that are structures capable of absorbing all power of incident electromagnetic waves. They are used as non-reflective covering layers for shielding against electromagnetic radiation and minimization of backscattering from electromagnetic large structures. Within the concept of metasurfaces, thin film absorbers, are usually implemented by placing a lossy material on the top of a perfectly conducting metallic plate. Recently, an electrostatic gate-tunable perfect absorber based on a monolayer graphene over a grounded dielectric was demonstrated experimentally in the low THz regime. Nevertheless, the dynamic control of the absorption properties of such devices in an ultrafast way still remains a challenge.