▎ 摘　　要

Graphene magnetoplasmons, collective excitations of massless Dirac fermions, can be actively tuned by an external magnetic field in addition to electrostatic gating. Their magneto-optic properties are highly determined by the edges of the structure and their interaction. Here, we focus on the fundamental dipolar magnetoplasmon, which has strong optical activity, and report its extinction spectra in graphene circular rings, eccentric rings, and split rings. We find that, as compared to traditional graphene disks, circular rings still sustain symmetrical mode splitting (omega(+) and omega(-)) but with less energy difference Delta omega = (omega(+) - omega(-). Increasing the ratio of inner radius to outer radius, Delta omega will decrease further and eventually vanish at a critical ratio, which can be well described as a function of the only product of cyclotron frequency and relaxation time. In eccentric rings, a small translation of the inner hole will not change the mode splitting and thus the value of Delta omega, but for a larger translation, Aw increases dramatically, with one magnetoplasmonic mode (polarization dependent) getting dark gradually. In split rings, due to symmetry breaking abruptly, even a very tiny split will cause the disappearance of mode splitting. Our findings contribute to a basic understanding of graphene magnetoplasmons which, in turn, can boost the application of graphene magneto-optic devices at terahertz and infrared frequencies.