Narrow resonance and ultrahigh sensitivity plasmonic waveguide refractive index sensor

Abstract

A surface plasmon resonance optical refractive index sensor (for aqueous medium) with high angular and spectral sensitivities S, very small full width at half maxima (FWHM) w (narrow resonance), and very high quality factor, χ = S/w, is proposed, which operates in both angular and spectral interrogation modes. The structure consists of a prism and a composite plasmonic waveguide consisting of a high-index dielectic layer and a thin metal (Ag) film, separated by a low-index layer. Above the metal film, the medium is analyte. It is shown that even with a prism of low index, the proposed sensor offers very small FWHM of reflection spectra, which improves the sensor performance. Numerically, an angular sensitivity of 168°RIU−1 and a quality factor χ = 1680 can be achieved for the proposed configuration. Spectral sensitivity comes out to be 6000 nm RIU−1.