Optical Conveyor Belt With Electrically Tunable Graphene Plasmonic Nanorings

In this letter, we propose a plasmonic conveyor belt based on a periodically arranged graphene nanorings (GNRs) with different size, on which the hot spots could be continuously lighted up by electrically tuning the Fermi level of graphene and could be used for the trapping and transporting of nanoparticles even under a uniform Mid-infrared or terahertz light excitation. Graphene nano-structure supports surface plasmon resonance, and its resonance condition is not only related with its size, but also could be adjusted by its Fermi level, as well as the applied gate voltage. In this way, a periodically arranged GNRs with different size can be excited in turn, thus realizing the function of transporting nanoparticles without reconfiguring the light excitation. In light of the rotational symmetry of GNRs, our polarization-independent design approach obviously has more advantages than the ones consisting of the graphene strips. In addition, the feasibility of the particle-separation is demonstrated. As confirmed by the numerical analysis, our design offers an optimized scheme for polarization-independent and electrically tunable plasmonic conveyor belt, which could be used in many on-chip optofluidic applications.