Introducing 2D confined propagating plasmons for surface plasmon resonance sensing using arrays of metallic ribbons

Surface plasmon resonance (SPR) detectors using a continuous flat metal surface for bio-sensing have been extensively studied and some configurations have almost achieved the ultimate possible performance for such sensors. In this paper we numerically present a novel method of enhancing the sensitivity of the SPR sensors by exciting surface plasmons that propagate parallel to metallic ribbons. In doing so we retain the advantage of the conventional propagating plasmons for bio-sensing, while the presence of the metallic ribbons give rise to confinement effects which in turn enhance the performance of the detectors. A new propagating plasmon mode, strongly confined to the metal surface, which to our knowledge has not been previously studied in the context of bio-sensing, is studied in this paper. This mode can help reduce the amount of target molecules needed to have a detectable signal by selective localization of the molecules in the positions where we have a strong field enhancement. It also reduces the effect of background refractive index changes thus making the detection of target induced refractive index changes easier, more robust and stable. These points are quantified in terms of sensitivity enhancement factor (SEF) and figure of merit (SFOM).