Wide range refractive index sensor based on a coupled structure of Au nanocubes and Au film

We report a plasmonic refractive index sensor with a wide measurement range based on periodic gold nanocubes coupled with a gold film. The theoretical sensing range is 1.0–1.8. The structure consists of two-dimensional gratings composed of periodic nanocubes that both excite local surface plasmon resonance and stimulate propagating surface plasmon resonance. The strong resonance of the multiple surface plasmons is suitable for use in refractive index sensing and effectively reduces the full width at half maximum of the resonance peak. The sensing performance of each resonant mode in the reflected spectrum is discussed in detail. The highest sensitivity and figure of merit of the proposed sensor are 1002 nm per refractive index units (RIU) and 417 RIU−1, respectively. The proposed sensor will be useful for bio-chemical sensing applications such as measuring changes in the refractive index of gases or liquids.