Tunable THz Switch-Filter Based on Magneto-Plasmonic Graphene Nanodisk

Abstract

We propose and analyze a new multifunctional THz device that can operate as a tunable switch and a tunable filter. The device consists of a circular graphene nanodisk coupled to two nanoribbons oriented at 90° to each other. The graphene elements are placed on a dielectric substrate. The nanodisk is magnetized by a dc magnetic field normal to its plane. The physical principle of the device is based on the propagation of surface plasmon-polariton (SPP) waves in the graphene nanoribbons and excitation of dipole mode in the nanodisk resonator. Numerical simulations show that 0.61 T dc magnetic field provides transmission (regime ON) at the frequency 5.33 THz with the bandwidth (BW) 12.7% and filtering with a Q-factor of 7.8. At the central frequency, the insertion loss (IL) is around -2 dB, and the reflection coefficient is -43 dB. The regime OFF can be achieved by means of switching the dc magnetic field to zero value or by switching the chemical potential of the nanodisk to zero. This results in the ON/OFF ratio better than 20 dB. A small central frequency tuning of the switch by chemical potential is possible with a fixed dc magnetic field.