A plasmonic bandpass filter based on graphene is proposed and numerically investigated using the finite-difference time-domain method. The proposed filter has a very simple structure, including two graphene nanoribbon waveguides laterally coupled to a graphene ribbon resonator. The transmission efficiency can be tuned by altering the coupling distance between the ribbons. At the same time, the variation of the transmission spectra is investigated by tuning the size of the graphene resonant ribbon. Notably, due to the unique electronic tunability of graphene, the transmission spectra can be freely tuned in a broad frequency range by choosing the chemical potential, which exhibits more flexible tunability than that used in conventional metallic devices. Attributed to the standing wave distribution of different modes excited in the graphene resonant ribbon, the proposed filter can be used for the plasmonic device with the capability of band selection or power splitting by locating the output waveguide ports in the suitable positions.

We investigate the plasmonic analog of electromagnetically induced transparency (EIT) using two adjacent graphene-based Fabry-Perot (F-P) resonators side coupling to a nanoribbon waveguide. By the coupling mode theory in time and F-P resonant model, the destructive interference from the coupling of the two F-P resonators results in the EIT-like optical response. The induced peak and width of the transparency window can be dynamically manipulated by varying the coupling distance of the two resonators, and the transparent window is easily shifted by tuning the resonator length or the chemical potential of the graphene nanoribbon. In order to verify the characteristics of slow light, the group index profile is analyzed at different coupling distances. The proposed graphene-based EIT-like system could open up new opportunities for potential applications in plasmonic slow light and optical information buffering devices.

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We propose and numerically analyze a Bragg reflector composed of periodically arranged graphene nanoribbon waveguides with different widths. Because of the unique property of the graphene edge mode, the effective index contrast used for the reflector can be obtained by designing graphene nanoribbons with different widths without changing the dielectric substrate structure. Good band stop filtering characteristics are shown at the band gap of the transmission spectrum by numerical simulation. The performance of the proposed Bragg reflector is analyzed in terms of different parameters, such as the chemical potential, the number of periods, and the size of the unit cell. The proposed Bragg reflector will be expected to have important potential applications in the highly integrated SPP-based photonic devices.

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