Rigorous Coupled-Wave Analysis of Surface Plasmon Enhancement from Patterned Immobilization on Nanogratings

Abstract

We numerically evaluate the optical response of a Kretschmann surface plasmon resonance (SPR) biosensor featuring metallic nanogratings and patterned immobilization of surface receptors. Parameters are chosen such that the biosensor is operated near the generated bandgap of the surface plasmon dispersion. In this paper, we demonstrate that the sensitivity can be increased by concentrating the surface receptors and adsorbed analytes on regions where the field intensity is the greatest. Specifically, a surface presenting receptors on the grating mesas is shown to be twice as sensitive as that of a uniformly functionalized corrugated surface. The grating geometries are also studied; it is found that higher aspect ratio features show increased SPR response. The analysis differs from existing studies of enhanced SPR as the sensitivity improvement originating from the concentration and mapping of surface receptors to the plasmon field distribution is studied rather than the absorption or scattering enhancement effect of the nanostructures.