Multi-path remote-excited surface plasmon resonance of a hollow gold nanosheet studied using FDTD simulations

Abstract

Multi-path remote-excited surface-enhanced Raman scattering (SERS) could be achieved in a two-dimensional hollow gold nanosheet (HGNS) structure. This structure typically contains one hollow and regular cavity located concentrically in the middle of a gold nanosheet (GNS), which forms such as Triangle-Triangle (T-T) or Hexagon-Hexagon (HH) HGNS. As for T-T HGNSs, if we focused the exciting incident laser on one vertex of the outer-solid-triangle (OST) or inner-hollow-triangle (IHT), the localized surface plasmon resonance (LSPR) could be achieved on other remote vertexes. Because of this hollow cavity (e.g. IHT in T-T HGNSs), the maximum quad-path remote-excited SERS system could be developed. The optical property of equilateral triangular and solid GNS (SGNS) is comparatively simple and symmetric. However, after a hollow triangle cavity is formed within GNS, it can be used to modulate LSPR and bring in a new coupling effect between OST and IHT. FDTD simulations have shown that a red-shift of LSPR peak with the increase of IHT size were observed. Compared with single-path-excitation, the remote signal of LSPR scattering at wavelength around 0.76 μm can be enhanced, under the optimum coupling polarization, by over 228 %, 597 % and 1155 % for dual-, triple- and quad-path-excitation respectively. At given LSPR peak (e.g. around 1.061 μm), this enhancement can be doubled once again at least. Furthermore, a remarkable polarization-dependent anisotropic property in T-T HGNS was observed owing to strong OST-IHT couplings, which exhibits great potential application in remote SERS, remote sensing and optical waveguide switch.