Strong Optical Transmission Through Double-Layer Coaxial Gold Tapered Nanoslit Array

By using the finite difference time domain method, we studied theoretically the transmission spectrum characteristics and plasmonic coupling on the double-layer coaxial gold tapered nanoslit array. The transmission spectra blue shifted with the increase in the tapered slit width or the decrease in the thickness of gold film. Based on the simulated field distribution, the resonance peaks located at nearby lambda = 0.3488 mu m were characterized as surface plasmon resonance, the peaks located at nearby lambda = 1.46 mu m were contributed to the localized waveguide resonance, and the peaks located at nearby lambda = 0.6274 mu m were formed by SPR and localized waveguide resonance. The intensities of SPR peaks increased continually and the localized waveguide peaks blue shifted with the decrease in the distances between two layers. The nano-focusing of this structure was also discussed.