Plasmon induced absorption in a graphene-based nanoribbon waveguide system and its applications in logic gate and sensor

In this article, nanoscale integrated logic gates and a refractive index sensor both based on the tunable plasmon induced absorption (PIA) effect are proposed and investigated by employing a plasmonic waveguide nanostructure. Except for the direct and indirect coupling mechanism which is employed to explain the single PIA effect, the transmission of a three-resonators-coupled waveguide system is deduced theoretically to explain the dual PIA effects. Our calculated results prove that high tunability in wavelength and amplitude of the PIA effect can be achieved by tuning the Fermi levels of the graphene nanoribbons. By taking advantage of the interferometric effect, the logic gates are realized in this ultracompact structure based on the PIA effect in the mid-infrared region. The numerical results reveal that, for the plasmonic logic gate with coupling length of 60 nm, a high extinction ratio (>23.5 dB) can be achieved within a footprint of <0.06 µm2. Moreover, a plasmonic refractive index sensor with sensitivity as high as 1870 nm/RIU is also numerically predicted in this graphene-based waveguide system.