Fig. 1. (a) Three dimensional schematic diagram of the composite structure of Au nano cone and Au nano film; (b) A top-down view of the structure, and the red foursquare lattice is the calculation unit

Fig. 2. Reflection spectra of composite structure of gold nano cone and gold film. The bottom radius, the height and the period of the gold nano cone are 140 nm, 200 nm, 800 nm, and the background refractive index is 1.30

Fig. 3. Electric field distributions of the composite structure at two modes resonance wavelengths. The bottom radius, the height and the period of gold nano cone are 140 nm, 200 nm and 800 nm. The background refractive index is 1.30. (a) and (d) are the electric field distribution on the x-z plane; (b) and (e) are the electric field distribution on the lower surface of the SiO₂ spacer and the interface of the Au film; (c) and (f) are the electric field distribution on the surface above the analyte and the SiO₂ spacer; (a), (b) and (c) are mode 1, (d), (e) and (f) are mode 2

Fig. 4. The background refractive index is 1.30, the reflection spectra of the composite structure under different parameters. (a) D 800 nm, R 140 nm, and H changes from 200 nm to 240 nm; (b) D 800 nm, H 200 nm, and R changes from 100 nm to 180 nm; (c) H 200 nm, R 140 nm, and D changes from 700 nm to 900 nm; (d) Simulation and theoretical values of mode 1 resonance wavelength at various period

Fig. 5. Reflection spectrum of the composite structure under different refractive index of analyte. The radius of Au nano cone is 140 nm, the height is 200 nm, and the period is 800 nm

Fig. 6. Relationship curves of reflection spectrum resonance wavelength of the composite structure with refractive index change under different refractive index of object to be measured. The bottom radius of gold nano cone is 140 nm, the height is 200 nm, and the period is 800 nm