Light Transmission and Surface-Enhanced Raman Scattering of Quasi-3D Plasmonic Nanostructure Arrays with Deep and Shallow Fabry-Pérot Nanocavities

Light transmission and surface-enhanced Raman scattering (SERS) of quasi-3D plasmonic nanostructure arrays with deep (820 nm) and shallow (80 nm) Fabry-Pérot (FP) nanocavities were investigated experimentally and by means of 3D-finite-difference time-domain (3D-FDTD) simulations. The arrays with deep FP nanocavites exhibited the extraordinary optical transmission and strong SERS effect, whereas weaker light transmission and 6-time to one-order of magnitude lower SERS enhancement factors were observed for those with shallow FP nanocavities. 3D-FDTD simulations revealed that strong electric fields, arising from localized surface plasmons (LSPs), were confined in the vicinity of the rim of top gold nanoholes and the edge of bottom gold nanodiscs for deep FP nanocavity arrays. In contrast, the LSPs of the top gold nanohole film and the bottom gold nanodiscs were coupled and propagated in the photoresist layer, thereby weakening the electric fields of gold nanostructures. The FP resonances occurred outside the wavelength range of the spectrometer used and therefore were not observed for quasi-3D nanostructures with both deep and shallow nanocavities.