Tuneable terahertz frequency-selective absorber based on a graphene/gold bilayer metasurface

In this work, a 0.2 THz electrically tuneable frequency-selective absorber is designed, fabricated, and experimentally tested. The tuneable absorber is achieved through a novel graphene/gold bilayer with a superimposed metamaterial structure. With this approach, a high-quality resonance is provided by the gold, with electrical tuneability from the graphene, in the bilayer. 16 dB of amplitude tuning at the designed 0.2 THz resonance is demonstrated, alongside 95% broadband modulation for only 6V applied bias. Terahertz time domain spectroscopy in reflection geometry is used to experimentally characterize the device, developed through an equivalent circuit model and three-dimensional full wave modelling and simulation in CST Microwave Studio. The design, fabrication and testing method are readily adaptable to other non-tuneable metal metasurfaces to produce a myriad of reconfigurable terahertz devices.