▎ 摘　　要

A planar plasmonic filter consisting of two graphene ribbons coupled by a graphene ring is constructed on monolayer graphene and investigated using the finite-difference time-domain method. The simulation results reveal that the edge modes indeed enhance the electromagnetic coupling between objects. The structure exhibits perfect band-pass filtering effect tuning and is optimized by means of the gate voltage. The simulation results are confirmed by the resonance theory of the ring. This structure is a real electrically controlled filter operating in the mid-infrared region. Our studies support the fabrication of ultracompact planar devices for optical processing. (C) 2014 The Japan Society of Applied Physics