Dispersion Characteristics in Disk-on-Pillar Array Nanostructures for Surface-Enhanced Raman Spectroscopy

In this paper, we analyze periodic disk-on-pillar nanoarrays as a platform for surface-enhanced Raman spectroscopy measurements. The nanostructure is a two-dimensional grating of silicon pillars covered by thin layers of silica and silver. The system supports both localized surface plasmons and surface plasmon polaritons. We investigate the dispersion characteristics of the nanoarray and present the relevant field distribution for each plasmon mode. The interaction between localized and propagating modes can be tuned to synergistically enhance the electric field, which results in larger surface-enhanced Raman signals. We find that utilizing this effect can generate Raman enhancements that are approximately 1000 times larger than that of an isolated pillar under the same excitation conditions.