Fig. 1. (a) Schematic of the proposed metallic nanoslit arrays with a top variable dielectric and a CYTOP substrate. (b) Schematic of the fabrication process for the proposed structure.

Fig. 2. (a) Transmission spectrum of the top-layer silica with normal incidence. Magnetic field distributions of the device region at (b) CM2, (c) SPP-CM, and (d) CM1.

Fig. 3. Comparison of the transmission spectra of (a) different top materials and (b) gain-assisted materials (the inset provides a clear picture of the peak position).

Fig. 4. Transmission spectra for incident angles from 5° to 30°. Different color lines denote distinct incident angles. The inset figure shows the schematic structure of the oblique incidence with variable incident angle α. The wavelength of incident light is 1 μm, and the other parameters remain constant.

Fig. 5. (a) Transmission spectra of the first-order CM of the periodic metal structure with different values of period. (b) Transmission intensities as a function of the corresponding wavelength (λ3) and period.

Fig. 6. Simulated transmission spectra of the designed structure with P = 600  nm, D = 460  nm, and different duty cycle values from 0.05 to 0.15.

Fig. 7. (a) Transmission intensity as a function of wavelength (λ3) and slit depth. (b) Wavelength sensitivity of the resonance peak of CM1 and its FOM as functions of depth. Other parameters: normal incidence, P = 600  nm, W= 30  nm, and d = 200  nm.