Abstract
This study presents the design and optimization of device with 1D nanostructured grating modeled on gold (Au), silver (Ag) and copper (Cu) for sensing a minor variation in refractive index (RI). This small change in the adjacent media to metallic grating is detected quite effectively using the unique characteristic of the surface plasmon polaritons (SPPs). The electric field (E-field) of the SPPs penetrates into the nearby media which is very sensitive to slight change in RI. The grating devices has been simulated by using COMSOL Multiphysics 5.3a with periodicity 700 nm, film thickness 50 nm and optimum slit width 300 nm in correspondence with fundamental plasmonic mode. The 0th order transmission spectra have been extracted from each grating device by illuminating (through the substrate side) with p-polarized light at normal incidence. The change in RI of analyte studied to have a significant effect on the resonance wavelength. The sensitivity has been calculated as 700, 731 and 722 nm/RIU for Au, Ag and Cu grating devices respectively which is remarkable. The stability and quick sensing of Au-device make it suitable for application besides some other deficiencies (e.g. slightly less sensitivity as compared to Ag) which should be compromised. Near field analysis has been performed to apprehend the underlying physics connected with each resonance. The highest value of electric and magnetic fields (E-field and H-field) are obtained in the case of Au grating indicating the most efficient excitation of SPPs. This confirms the reasoning behind the efficient sensitivity of Au grating device and finds applications in medicine.