A comparative study of multi- and mono-layer structures for bulk and thin film plasmonic sensing

Surface plasmon resonance (SPR) optical sensors have attracted considerable attention, finding diverse applications, particularly in the fields of biomedicine and chemistry. While single metal layer based SPR sensors are commonly used, their resolution is limited by broad resonances. Consequently, researchers have dedicated efforts to achieve sharper resonances and heightened sensitivity. In this study, we investigate the use of multilayer structures for bulk sensing and elucidate how they contribute to improving sensor sensitivity. Additionally, we explore thin film sensing, conducting a thorough comparative analysis of monolayer and multilayer structures. Our findings reveal that thin film sensing based on monolayer structures outperforms multilayer stacks. This superiority is linked to the reduced sensitivity observed in the latter, stemming from the compromised coupling between Surface Plasmon Polariton (SPP) modes within the multilayer structure upon the application of the sensing layer. This research not only advances our understanding of SPR sensors but also highlights the potential of tailored multilayer structures in optimizing sensor performance.