Fig. 1. Structure diagram and transmission spectrum. (a) Structure diagram of waveguide structure with single T-shaped cavity; (b) transmission spectra of waveguide system with and without T-shaped cavity; (c) Fano resonance spectrum of MIM waveguide coupled T-shaped cavity with single baffle

Fig. 2. Phase diagram. (a) At FRP1; (b) at FRP2

Fig. 3. E_Z field distribution. (a) E_Z field distribution of FRP1 at λ=859 nm; (b) E_Z field distribution at the first transmission dip at λ=901 nm; (c) E_Z field distribution of FRP2 at λ=1080 nm; (d) E_Z field distribution at the second transmission dip at λ=1108 nm

Fig. 4. Quadruple Fano resonance.(a) Structure diagram of waveguide with dual T-shaped cavity; (b) transmission spectrum corresponding to quadruple Fano resonance; (c) transmission spectra at different h₁; (d) transmission spectra at different l₁; (e) transmission spectra at different h₂; (f) transmission spectra at different l₂

Fig. 5. Analysis of sensing characteristics. (a) Transmission spectra of Fano structure for different refractive indices; (b) peak wavelength as a function of refractive index; (c) FOM at different wavelengths