Electric field enhancement in metal-dielectric metasurface based on periodic nanocavities

A new metasurface focusing light at a nanoscale is presented. The metasurface consists of periodic dielectric nanocavities with a top silver nanolayer. When interacting with the light, the metasurface exhibits plasmon resonances, which lead to the local electric field enhancement. The minima in the calculated and experimental reflectance spectra that indicate the light localisation on the metasurface are obtained. We propose that the metasurface can be an effective SERS substrate for the detection of various proteins, bacteria, viruses and their derivatives.