Plasmonic refractive index sensor of a hexagonal close-packed gold nanodisk array coupled with a gold thin film

The study proposes an innovative surface plasmon refractive index sensor based on a hexagonal close-packed gold nanodisk array coupled with a gold thin film. The composite structure comprises a SiO 2 substrate, an Au thin film, a SiO 2 spacer layer, and a hexagonal close-packed Au nanodisk array. The study used the finite-difference time-domain method to investigate the surface plasmons excitation characteristics, optical field distribution, and refractive index sensing properties of the composite structure. The composite structure excited three surface plasmon resonance (SPR) modes in a liquid environment. The study investigated the influence of structural parameters on the three SPR modes. The sensing performance of the composite structure was studied in gas environments (n=1.00−1.10) and liquid environments (n=1.33−1.40). The maximum sensitivity ( S ) and the maximum figure of merit (FOM) could reach 1297 nm/RIU and 260RIU −1 in gas environments, and 1291 nm/RIU and 208RIU −1 in liquid environments. The sensor has the advantages of high sensitivity, a high FOM, a simple structure, and easy processing. This study obtains excellent sensing performance by changing the arrangement of Au nanoparticles, providing a reference for designing surface plasmon refractive index sensors based on the coupling structure of a metal nanoarray and a metal thin film. The sensor can be used in a broad range of biochemical detection applications, such as detection of hemoglobin concentration and temperature sensing.