Tunable high-channel-count bandstop graphene plasmonic filters based on plasmon induced transparency.

A high-channel-count bandstop graphene plasmonic filter based on ultracompact plasmonic structure is proposed in this paper. It consists of graphene waveguide side-coupled with a series of graphene filtering units. The study shows that the waveguide-resonator system performs a multiple plasmon induced transparency (PIT) phenomenon. By carefully adjusting the Fermi level of the filtering units, any two adjacent transmitted dips which belong to different PIT units can produce coherent coupling superposition enhancement. This property prevents the attenuation of the high-frequency transmission dips of multiple PIT and leads to an excellent bandstop filter with multiple channels. Specifically, the bandwidth and modulation depth of the filters can be flexibly adjusted by tuning the Fermi energy of the graphene waveguide. This ultracompact plasmonic structure contributes to the achievement of frequency division multiplexing systems for optical computing and communications in highly integrated optical circuits.