SERS-active substrate based on gap surface plasmon polaritons.

We numerically investigate the optical field enhancement supported by gap surface plasmon polaritons (GSPPs). The optical field enhancement at the edge of the nanostructures originates not only from localized surface plasmon (LSP) resonance but also from multiple scattering and coupling of GSPPs in the spacer region between two metal plates. By calculating field enhancement, we predict surface-enhanced Raman scattering (SERS) enhancement factors (EFs) of up to 10(11) for equilateral triangular nanostructures. The SERS EFs as a function of the geometry and dimension of the nanostructures are obtained by simulation. The effect of the surrounding medium on the SERS EFs is also investigated. Coupled with easy fabrication, those nanostructures are expected to find important applications in optical sensing as a SERS-active substrate.