▎ 摘　　要

A highly sensitive plasmonic refractive index biosensor for hemoglobin protein detection in blood is presented in the near-infrared region. The proposed Au split-ring resonator structure with an extra arm is used to increase electric field enhancement intensity in the vicinity of the nanostructure, which excites localized surface plasmon resonances in the metal-dielectric interface and leads to unity absorption. The footprint of the proposed structure is lambda(3)/125 (lambda denoting center wavelength). Through the results from the finite element method (FEM), by variation of the spacer material, and inserting a graphene layer between the spacer and the gold nanostructure, maximum sensitivities of 1804.1 nm/RIU and 2448.45 nm/RIU are achieved, respectively. (C) 2021 Optica Publishing Group