Armin Agharazy Dormeny
Published: 2020
Total Pages: 0
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In the last two decades, the unusual optical and physical properties of novel metallic nanostructures (such as gold, silver, and aluminum) has been the subject of intense research efforts. Surface plasmon resonance and localized surface plasmon resonance are two of the unique phenomena in novel metals which can be used to create different kinds of sensitive sensors and biosensors. In this work, a refractive index sensor based on surface plasmon resonance is designed and analytically investigated by a finite element method via COMSOL Multiphysics to detect chemicals. The intensity, spectral width and sensitivity of the plasmonic signals are highly affected by the shape, size, and configuration of the metallic nanostructures. Patterning the planar metallic thin film with cavities or protrusion can result in obtaining a tunable sensitivity for the sensor. The architecture of the nanohole/nanowire arrays leads to a nanostructure having multiple plasmonics properties. The simulation results show that the co-excitation of surface plasmon resonance and localized surface plasmon resonance modes can enhance the sensitivity of the SPR-based sensors significantly. To obtain this result, several cut lines through the metallic thin film were considered and the variation of the electric field intensity along those cut lines is studied. To determine the SPR and LSPR modes, the penetration depth of the plasmon field is characterized at metal/dielectric interfaces. After investigation of three models for the metallic layer (planar thin film, nanohole patterned thin film, and protrusive thin film), it was concluded that the device made of 20 nm cylindrical nanowire supported by a 40 nm thin film can result in the best performance parameters (in terms of sensitivity, absorption, and accuracy). Eight substances with refractive indices ranging from 1.333 to 1.38 were used to obtain the calibration data of the optimum sensor. The linear characteristic of the calibration curve shows that the sensor is able to detect unknown materials as a function of resonance wavelength. This study is proposing a new way to show the duality nature of patterned thin films to support both propagating and localized surface plasmon modes.