Reduced resonance line-width and enhanced figure of merit in Ag/Si/SiO2 nanopillar array sensors

Ag/Si/SiO2 nanopillar array sensors are presented to reduce the line-width and enhance the figure of merit (FOM). In Ag/Si/SiO2 nanopillar arrays, each Ag nanopillar is on top of each Si nanopillar, and each Si nanopillar is on top of each SiO2 nanopillar, which sits on quartz substrates. The simulated results show that the line-width can be as small as 7 nm, 2.4 times narrower than that of the periodic arrays of Ag nanopillars on SiO2 nanopillars, which sit on quartz substrates. This can be attributed to the reduced line-width of the plasmonic lattice resonance (PLR), which is due to the coupling between the localized surface plasmon quadrupole polarization of Ag nanopillars and the diffraction of the periodic arrays. The period of the arrays, the diameter of Ag nanopillars, the thickness of Ag nanopillars, Si nanopillars and SiO2 nanopillars have important effects on the PLR. Benefiting from the narrower line-width, the FOM is enhanced. This provides a possible way to improve the application of plasmonic array sensors.