Ultrashort terahertz cross-bar switch based on a graphene plasmonic directional coupler

We propose a new vertical graphene plasmonic directional coupler as a terahertz cross-bar switch. The directional coupler is constructed of two pattern-free graphene plasmonic waveguides. The lateral confinement of surface plasmon polaritons is accomplished based on the similar mechanism used in dielectric loaded waveguides. An ultrashort switching length of 360 nm is obtained at the frequency of 30 THz. A switching voltage of 4.96 V and a very high 3dB bandwidth of more than 110 GHz are also calculated. Three-dimensional finite-difference time-domain simulation of the structure is performed and the results are presented.