Highly sensitive and stable probe refractometer based on configurable plasmonic resonance with nano-modified fiber core

A dispersion model is developed to provide a generic tool for configuring plasmonic resonance spectral characteristics.The customized design of the resonance curve aiming at specific detection requirements can be achieved.According to the model,a probe-type nano-modified fiber optic configurable plasmonic resonance(NMF-CPR)sensor with tip hot spot enhancement is demonstrated for the measurement of the refractive index in the range of 1.3332-1.3432 corresponding to the low-concentration biomarker solution.The new-type sensing structure avoids excessive broadening and redshift of the resonance dip,which provides more possibilities for the surface modification of other functional nanomaterials.The tip hot spots in nanogaps between the Au layer and Au nanostars(AuNSs),the tip electric field enhancement of AuNSs,and the high carrier mobility of the WSe_(2)layer synergistically and significantly enhance the sensitivity of the sensor.Ex-perimental results show that the sensitivity and the figure of merit of the tip hot spot enhanced fiber NMF-CPR sensor can achieve up to 2995.70 nm/RIU and 25.04 RIU^(−1),respectively,which are 1.68 times and 1.29 times higher than those of the conventional fiber plasmonic resonance sensor.The results achieve good agreements with numerical simulations,demonstrate a better level compared to similar reported studies,and verify the correctness of the dispersion model.The detection resolution of the sensor reaches up to 2.00×10^(−5)RIU,which is obviously higher than that of the conventional side-polished fiber plasmonic resonance sensor.This indicates a high detection accuracy of the sensor.The dense Au layer effectively prevents the intermediate nanomaterials from shedding and chemical degradation,which enables the sensor with high stability.Furthermore,the terminal reflective sensing structure can be used as a practical probe and can allow a more convenient operation.

Performance improvement approaches for optical fiber SPR sensors and their sensing applications

Optical fiber surface plasmon resonance(SPR) sensors point toward promising application potential in the fields of biomarker detection,food allergen screening,and environmental monitoring due to their unique advantages.This review outlines approaches in improving the fiber SPR sensing performance,e.g.,sensitivity,detection accuracy,reliability,cross-sensitivity,selectivity,convenience and efficiency,and corresponding sensing applications.The sensing principles of SPR sensors,especially the performance indicators and their influencing factors,have been introduced.Current technologies for improving the fiber SPR performance and their application scenarios are then reviewed from the aspects of fiber substrate,intrinsic layer(metal layer),and surface nanomaterial modification.Reasonable design of the substrate can strengthen the evanescent electromagnetic field and realize the multi-parameter sensing,and can introduce the in situ sensing self-compensation,which allows corrections for errors induced by temperature fluctuation,non-specific binding,and external disturbances.The change of the intrinsic layer can adjust the column number,the penetration depth,and the propagation distance of surface plasmon polaritons.This can thereby promote the capability of sensors to detect the large-size analytes and can reduce the full width at half-maximum of SPR curves.The modification of various-dimensionality nanomaterials on the sensor surfaces can heighten the overlap integral of the electromagnetic field intensity in the analyte region and can strengthen interactions between plasmons and excitons as well as interactions between analyte molecules and metal surfaces.Moreover,future directions of fiber SPR sensors are prospected based on the important and challenging problems in the development of fiber SPR sensors.