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.
Optical sensors based on a plasmonic multilayer stack, such as metal-insulator-metal (MIM), have attracted considerable attention over the past decades owing to their high resolution and high performance compared to conventional surface plasmon resonance (CSPR) sensors for bulk sensing (BS) applications. In this paper we show that CSPR is better than MIM sensors for thin film sensing, i.e. when a dielectric sensing layer (SL) is deposited on the outermost metal layer of the structure. We demonstrate that the deposition of a thin film SL on the top of the outermost-layer of an optimized multilayer structure, i.e. MIM, strongly decreases the evanescent electric field and the field enhancement at metal-SL interface and decreases the sensor’s sensitivity for MIM versus CSPR. By considering the theoretical and experimental results we demonstrated that CSPR is more suitable than MIM for thin films sensing applications.
In this presentation, we discuss enhancement of photo-orientation of azo-dye in films of polymer by surface enhanced visible absorption (SEVA) of the dye in the vicinity of Gold nanoantennas. The dye undergoes shape and orientation change; i.e. isomerization and reorientation, upon polarized light absorption; and the observation of enhanced photo-orientation by SEVA is done by photo-induced birefringence (PIB) experiments, since the signal detected from PIB experiments is directly proportional to the extinction coefficient of the dye. Both the dye’s absorption and photoorientation are enhanced by the presence of the plasmonic nanoantennas.
The investigation of light-matter interaction has had growing interest in the field of photonics. In particular, metalinsulator-metal (MIM) sensors are of interest owing to their high sensitivity compared to conventional sensor made by a single metal layer. The high resolution and low concentrations detection is a result of the sharp resonance of the surface plasmon polariton waveguide hybrid mode at the Au/water interface supported by MIM structures. In this context, we have implemented experiments and theoretical simulations to estimate the enhancement of the sensitivity of metal-insulatormetal sensors. By changing the refractive index of an aqueous solution of glucose, we found that the use of a metalinsulator-metal stack improves the figure of merit of the sensor 7.5 times compared to that of a conventional surface plasmon resonance sensor.
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