Plasmonic–Diffractive Hybrid Sensors Based on a Gold Nanoprism Array

In order to improve the performance of localized surface plasmon resonance (LSPR) sensors, lattice plasmons of plasmonic nanoparticle (NP) arrays are often used. The lattice plasmon sensors based on coupling between LSPR of each NP and diffraction of the NP array generally have a higher ability to detect local refractive index changes than conventional LSPR sensors based on random NP ensembles. However, the surface selectivity of the lattice plasmon sensors is lower than that of the LSPR sensors because the local electric field of the former extends far from the particle array surface. In this work, we develop a novel plasmonic–diffractive hybrid sensor that can simultaneously determine both local and bulk refractive indices from two output signals, namely, extinction dip and peak, the wavelengths of which are differently dependent on those indices. The hybrid sensor can evaluate the refractive index changes in the immediate vicinity of the sensor surface by canceling the difference in the bulk refractive index between the sample and standard solutions.