Figure 3. The effect of the slit width on the transmission spectra of long- and short-cavity capped nanoslits with a period of 500 nm in water for normally-incident TM-polarized light.

(a) The transmission spectra of the short-cavity capped gold nanoslits. (b) The calculated Fano resonance spectra for different slit widths using equation (2). (c) The fitting resonant wavelengths and bandwidths of the cavity mode and BW-SPP mode as a function of the slit width. (d) The Fano asymmetrical factor as a function of the slit width. (e) The transmission spectra of the long-cavity capped gold nanoslits for different slit widths. (f) The resonant slope as a function of the slit width for both short- and long-cavity capped structures. The inset depicts the definition of the resonant slope.