Graphene-based multifunctional three-port THz and long-wave infrared components

Two graphene-based T-shaped multifunctional components for THz and long-wave infrared regions are proposed and analyzed. The first component can serve as a divider, a switch, and a dynamically controllable filter. This T-junction presents a circular graphene resonator and three graphene waveguides with surface plasmon-polariton waves connected frontally to the resonator. The resonator can be adjusted to work with dipole, quadrupole, or hexapole modes. The graphene elements are deposited on a SiO₂ (silica) and Si (silicon) two-layer substrate. The dynamical control and switching of the component are provided by the electrostatic field, which defines the graphene Fermi energy. Numerical simulations show that the first component in the division regime (which is also the ON regime) has a transmission coefficient of -4.3dB at the central frequency for every two output ports, and the FWHM is 9.5%. In the OFF regime, the isolation of the two output ports from the input one is about -30dB. The second component is a T-junction without a resonator, which fulfills the function of the divider-switch in more than an octave frequency band.