(color online) Simulated transmittance spectra of the band-pass filter of Fig. 1 with (a) three different outer radii (R₂) of the graphene ring resonator with chemical potential of μ_c = 0.35 eV, and (b) three different chemical potentials (μ_c) of the graphene ring with outer radius of 30 nm. (c) Comparisons of the resonance wavelengths of the first order mode of the graphene ring resonator versus its outer radius obtained by the FDTD method and the analytical resonance Eq. (6) of the ring resonator. The chemical potential of the ring is assumed to be μ_c = 0.35 eV.