Optical Properties and Liquid Sensitivity of Au-SiO2-Au Nanobelt Structure

Abstract

Optical properties of the Au-SiO2-Au nanobelt structure with quasiperiodicity along x-axis and fixed Au height, width and different spacer (dielectric) heights were numerically investigated for sensing application of liquids with refractive indices close to the water. Although both propagated surface plasmon mode and localized surface plasmon mode were recorded in the single-layer Au and Au-SiO2-Au nanobelt structure, only the localized surface plasmon mode was recorded in the Au-SiO2 nanobelt structure. The effects of increasing the dielectric layer (between two Au nanobelts) height on the extinction spectrum were observed as blue shift of whole extinction spectrum. It was found that the localized surface plasmon mode shift was negligible while the propagated surface plasmon mode was significantly shifted towards smaller wavelength. The minimum resonance linewidth was calculated as 42 nm at refractive index of 1.377, which is much smaller than that in the single-layer Au and Au-SiO2 nanobelt structures.