Comparison of E. coli detection in single and bi-metal clad waveguide biosensors

In this paper, we report comparison of non-specific detection of Escherichia coli bacteria in single and bi-metal-cladding waveguide biosensors. In a metal waveguide biosensor, a change in the refractive index of the cover medium results in the shift of the dip in the reflectance spectra at a specific incident angle. The addition of second metal layer increases the magnitude of the shift of the dip in the reflectance spectra. The shift of dip in the reflectance spectra is compared for a single and bi-metal waveguide and analyzed using Fresnel equations. It is also found that the stability of the core medium, i.e., polystyrene layer is of immense importance, degradation of which results in an asymmetrical reflectance dip due to variation in the its thickness.