Sensitivity enhancement of SPR based refractive index sensor in VIS-NIR region by using ZnS and PVP

Abstract

A highly sensitive optical sensor is presented. This sensor is having multilayer structure that is designed and optimized theoretically by using Zinc Sulfide (ZnS) and Polyvinylpyrrolidone (PVP). The optical sensor proposed here is based on Surface Plasmon Resonance (SPR) technique by using Kretschmann configuration. This SPR sensor is designed with BK-7 prism which is coated with silver (Ag), overlayers ZnS and PVP in sequence. Silver is the plasmonic metal, PVP and ZnS are polymer and dielectric respectively and they perform the interaction with analyte and sensitivity enhancement however ZnS contributes more to enhance the sensitivity. For the characterization of multilayer Ag/ZnS/PVP structure of optical sensor, spectral interrogation mode is used. The surface plasmon resonance wavelength was calculated for each concentration. It shifts linearly towards higher wavelength with the increasing concentration of the analytes from 1.33 to 1.35 refractive index when interact with sensing surface. The sensitivity of the sensor is found to be 8537.06 nm/RIU throughout. The spectral range of proposed sensor is Visible-Near Infra Red (VIS-NIR) region from 600 to 1050 nm. The detection accuracy (DA) decreases with increasing concentration of analytes. Figure of merit (FOM) is also having same nature as DA. The sensitivity of the proposed sensor is quite high in comparison to other sensors. The proposed sensor will be useful to sense the chemical and biological compounds within its detection range (from 1.33 to 1.35 refractive index) in VIS-NIR region from experimental point of view.