Investigation of the sensitivity enhancement of nanoparticle based surface plasmon resonance biosensors using rigorous coupled wave analysis

It is well known that the use of noble metal nanoparticles can considerably enhance the sensitivity of conventional surface plasmon resonance (SPR) biosensors. In our study, we theoretically investigate this sensitivity enhancement effect using rigorous coupled-wave analysis. It is based on the assumption that the enhancement of localized plasmons can be demonstrated by the coupling phenomenon between the periodic noble metal structures and the incident light with an appropriate polarization. It is shown that the rigorous coupled-wave method can be applied to calculating a SPR structure that includes metallic nanoparticles of rectangular-like geometry, where the presence of nanoparticles induces significant changes in the position of reflectivity minimum. The influence of the nanoparticle period on the sensitivity enhancement is also confirmed. In the calculation, Au nanoparticles deposited on an Au film or adsorbed on a SAM layer are modified to regularly patterned one-dimensional nanowires. When the period is less than 300 nm. the calculated sensitivity enhancement of the nanoparticle-based SPR structure is more than ten-fold compared with that of a conventional SPR biosensors configuration.