Fig. 1. (a) Schematic diagram of the bilayer metallic nanowire grating. (b) The theoretical SPR wavelength λSPR changing with ambient refractive index nA and incident angle θ. (c) AFM image of the fabricated grating structure.

Fig. 2. Simulated reflective spectra of the grating in ambient conditions. (a1) Reflected spectra changing with incident angle θ. (a2) The magnetic field Hy of the resonant peak for λ=452nm and θ=30°. (b1), (b2) Simulated reflected spectra changing with duty ratio f with θ=30° for bilayer and unilayer Al gratings. (c1), (c2) Reflected spectra changing with PR thickness h1 and Al thickness h2 with incident angle θ=30° for bilayer Al grating. Other parameters are the same as that in Fig. 1.

Fig. 3. Simulated reflective spectra under different ambient refractive indices nA. The dashed line is the theoretical λSPR changing with nA. Other structure parameters are the same as that in Fig. 1.

Fig. 4. (a) Snapshot of the measurement setup and the reflected photos with θ=50° of white light in ambient air, deionized water, and 80% sucrose solution, respectively. (b1)–(b3) Measured reflective spectra with ambient air, deionized water, and 80% sucrose solution, respectively. The black dashed lines are the calculated λSPR by Eq. (4). (c) Refractive index nA calculated by Eq. (4). The horizontal lines are the average values.