graphene-based directional coupler for THz region

Abstract

In this work, we investigated theoretically a directional coupler based on graphene for THz region. The principle of operation of the device consists in the propagation of surface plasma polaritons (SPP) wave in graphene nano-tapes separated by a certain distance. The graphene waveguides are deposited on dielectric substrate. Using finite element method, we analyze the four-port with surface plasmon polariton (SPP) waves in graphene waveguides. This device can be used to design plasmonic devices such as couplers, power dividers, switches, ultracompact interferometers, among others. Numerical simulations demonstrate that the division of the signal between two output ports of the coupler is -3.8dB and the isolation of the fourth port is better than -20dB in the frequency band of 14%. The central frequency of the directional coupling can be adjusted by the Fermi energy of graphene through the electrostatic gating, and it allows one to control dynamically the device responses.