Modeling of Au-Nanowire Waveguide for Plasmonic Sensing in Liquids

We theoretically demonstrate a plasmonic nanosensor, using Au-nanowire waveguide to measure the refractive-index changes in aqueous solutions. Based on finite element method simulations, waveguiding properties of Au nanowires for plasmonic sensing in liquids are investigated, with Au nanowire diameter down to 10 nm. A plasmonic nanowire Mach-Zehnder interferometer is proposed to measure the phase shift introduced by the index changes of surroundings. We find that, for a typical Au nanowire with 100-nm diameter, the calculated sensitivity is as high as 5.5π/(μm·RIU), and the sensitivity can be increased by reducing the nanowire diameter. Besides, for reference, we have also investigated Au nanowire plasmonic sensing in other liquids including ethylene glycol and index-matching oil. The nanowire plasmonic sensing scheme proposed here represents a high-sensitivity nanosensor with ultra-small footprint, and may open new opportunities for miniaturized sensing platform based on highly confined 1-D waveguiding plasmons.