▎ 摘　　要

In this paper, a dual-band refractive index sensor is proposed using hollow graphene-based core-shell spherical particles. The double tunable operating bands originate from the presence of dual graphene shells, providing tunable plasmonic resonances. The sensitivity (S) and figure of merit (FOM) of the proposed device in its operating bands are respectively as follows: S-1 = 9.4e+03 nm/RIU, FOM1 = 50.2, S-2 = 8.3e+02 nm/RIU, and FOM2 = 1.01e+02. This excellent performance is provided without any metallic/high index dielectric material. To analyze the proposed sensor, the modified Mie-Lorenz coefficients for a graphene-based core-shell spherical particle are introduced in the fully retarded regime and extreme plasmonic hybridization is discussed by observing the Rabi splitting phenomenon in the extinction cross-section. Later, using small argument approximations of the special functions in the Mie expansion, the associated modified Mie-Lorenz coefficients are simplified for ease of performance optimization.