Multi-response nanowire grating-coupled surface plasmon resonance by Finite Element method

Abstract

In this paper, Surface Plasmon Resonance (SPR) has been applied for sensing acetone liquid by changing the refractive index based on nanowire grating. This sensor was proposed and numerically analysed using finite element method. The SPR sensor composed of multi-nanowires distributed in a parallel order at a specific distance. These wires were deposited onto the dielectric material and tested using laser light at wavelengths between 500 nm to 700 nm. Dual SPR dips emerged at two different SPR angles after further tuning the incident angle. The multi SPR dips are angularly wide but spectrally produced very sharp results. SPR sensor results were compared at four different plasmonic materials gold, silver, aluminium and copper using 532 nm wavelength. These plasmonic materials were tested using acetone at 100%, 50%, 10% concentrations. The sensitivity measurements of the sensor have shown that the dual SPR dips can be used effectively to increase the sensitivity of the designed sensor. Both dips were also used to increase the detection sensitivity of different types of liquids. The sensitivity of SPR causes a shift in dip or intensity due to any small change in refractive index. This shift varies according to the material and liquid concentration. The sensitivity of nanowire grating was measured by varying the refractive index with the resonance angle (θ°) at a single wavelength. The highest sensitivity has been discovered for gold which is 290.57°/RIU. This work is adopted for the improvement of the surface plasmon sensor using nanowire technology. The structure is easy and simple and can be applied to different applications.