Ultrahigh-contrast plasmonic mode conversion in coupled graphene waveguides by manipulating the graphene chemical potential and the gyration

Abstract

We investigate ultrahigh-contrast plasmonic mode conversion in a coupled graphene waveguide structure with manipulated gyration and graphene chemical potential by using both analytic theory and numeric simulations. The ultrahigh contrast is supported by a magnetic resonance at the expense of high sensitivity on the design and material parameters and the operation frequency. The analytical study reveals that the ultrahigh contrast mode conversion can be preserved by adjusting the gyration and the chemical potential in the deviation of structural and material parameter values due to imperfect fabrication and harsh environment and for tuning its operation frequency over a broadband frequency range. We derive explicit analytical results for the resonance gyration and chemical potential that answer to those questions how to manipulate the gyration and the chemical potential according to the design and material parameters and the operation frequency. Numerical simulations demonstrate the robust and broadband tunable plasmonic mode conversion preserves the contrast higher than 103 (99.9%) for different design and material parameter values over a one-octave-spanning broadband frequency range. In practice, the chemical potential and the gyration can be manipulated by controlling the gate voltage of the graphene and the external magnetic field, respectively. Our findings can be of great importance in the design of high-integration nanophotonic circuits and for probing of ultrafast magnetization dynamics. Published by the American Physical Society 2024