Nanostructured substrates for surface plasmon resonance sensors

Surface Plasmon Resonance (SPR) sensors are usually based on continuous thin metallic films and coupling of propagative plasmon (PP) modes using high index prism or grating. The quantitative monitoring of the surface evolution is performed by measuring either shift in angular or spectral dip position, or by reflectivity variation in the slope of the angulo-spectral coupling curve. Such sensors are studied in many laboratories and used in a growing number of commercial devices. It appears however that these systems are reaching their limits in terms of sensitivity [1]. In the field of plasmonic sensing, many other works are devoted to the study of metallic nanoparticles. We anticipate that using nanostructured substrates for exciting coupled localized plasmon (CLP) or quasi propagating plasmon (QPP) will allow to further increase the sensors capabilities, in particular in terms of sensitivity. Samples were realized using either e-beam or deep-UV lithography based techniques. Experimental characterizations were conducted using lab-made angulo-spectral SPR Imaging systems [2]. Using RCWA simulations, we have calculated the plasmonics responses, in term of angulo-spectral reflectivity, of nanostructures. A novel narrow groove plasmonic nano-grating sensing configuration exhibits the highest potential [3].