▎ 摘　　要

We propose and numerically analyze an ultra-compact tunable plasmon ring resonator which is composed of monolayer graphene and a graphene ring. The results, calculated using the finite element method, reveal that the resonant frequency can be tuned over a wide frequency range by a small change of Fermi level in the graphene ring. Both a high quality factor and extinction ratio of the resonant mode can be achieved when the plasmonic waves in the ring and the input waveguide are properly coupled. As applications, this proposed resonator can be used to construct an ultra-compact fast-tunable filter, modulator, switch or directional coupler in the mid-infrared range.