Effect of ultra-shallow metallic gratings on sensitivity enhancement of Goos-Hanchen shift in SPR-based sensors

International audience; Metallic gratings have flexible and powerful modulation effects on electromagnetic waves. Reflection and transmission spectra of metallic gratings may become extremely narrow or ultra wide depending on the grating parameters. In this paper, a surface plasmon resonance-based sensing system comprising of a metallic grating coupled with a prism configuration was proposed. The effects of all parameters of the sensing system on the Goos-Hadnchen shift and sensitivity were studied in detail, and the results showed that ultra-shallow metallic gratings with large duty cycles, with no other materials involved, are more beneficial. In addition, a set of optimum parameters was obtained at the incident wavelength. Compared with the conventional SPR-based gold sensing chip, strongly coupled surface plasmon resonance around the grating enlarges the penetration depth, and enhances both Goos-Hadnchen shift and the corresponding sensitivity by 5.6 times, with increasing refractive indices of the analyte solutions. These results indicate that the proposed ultra-shallow metal grating-based sensing structure is in favor of detecting ultralow concentrations of biomolecules in the analyte solutions.