Dual-Band Reconfigurable Refractive Index Sensing Using All-Graphene Core-Shell Spherical Nanoparticles

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, FOM
₁
= 50.2,
S
₂
= 8.3e+02 nm/RIU, and FOM
₂
= 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.