Nanocavity in a silicon waveguide for ultrasensitive nanoparticle detection

Abstract

We demonstrate the use of a micron-size planar silicon photonic device for the detection of ultralow concentrations of metal nanoparticles. The high detection sensitivity is achieved by using a strong light confining structure that enhances the effective extinction cross section of metal nanoparticles. We demonstrate the detection of $10\mathrm{nm}$ diameter gold particles with a density of fewer than 1.25 particles per $0.04\mu {\mathrm{m}}^2$ . Using such a device one could detect the presence of single metal nanoparticles specifically bound to various analytes, enabling ultrasensitive detection of analytes including DNA, RNA, proteins, and antigens.