The Conformal HIE-FDTD Method for Simulating Tunable Graphene-Based Couplers for THz Applications

An improved hybrid implicit-explicit finite-difference time-domain (HIE-FDTD) method is proposed for simulating graphene-based patch couplers at terahertz (THz) for different physical and geometrical parameters, where the Drude model of monolayer graphene and the associated auxiliary differential equation (ADE) technique are implemented. In order to accurately model the curved graphene boundaries, the conformal FDTD method is further hybridized with the HIE-FDTD method, which results in a conformal HIE-FDTD method. Numerical results are presented for S-parameters and field distributions of the coupler, which can be adjusted effectively by changing the chemical potential and layer number of graphene patch or substrate permittivity.