Faraday effect sensing of single-molecules by graphene-based layered structures

To investigate the sensing properties of the Faraday effect in graphene in terahertz (THz), we consider the modulations of Dirac gaps in graphene when gas molecules are adsorbed to its surface. Here, the effect of the associated bandgap opening in graphene’s spectrum on the sensing properties of the Faraday rotation (FR) in a 1D photonic graphene-based sensor with a microcavity defect channel covered by two graphene layers. Our proposed model introduces an optical contact-free mechanism for detecting low-concentration molecules attached to graphene’s surface. We also show that FR angles could reveal reversal signs for a different amount of surface transfer doping. Finally, the effect of increasing the temperature on the Faraday effect at a certain opening gap in graphene’s spectrum is investigated. Interestingly, stronger FR effect it was observed at higher temperatures. Our results could open the path for development of contact-free sensing applications in THz region.