Terahertz characterization of graphene thin films on both sides of substrate

Graphene thin films on two sides of quartz substrate are characterized via Terahertz time-domain spectroscopy in this paper. The quartz substrate permittivity is first characterized. The graphene film is then treated as a surface boundary condition between the substrate and air. Using the uniform field approximation, the surface conductivities of graphene films are extracted. Compared to some previous approach, more accurate results in wider frequency range is achieved because of the second layer of graphene film and small substrate loss.