Nanocavity in a silicon waveguide for ultrasensitive nanoparticle detection

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 10nm diameter gold particles with a density of fewer than 1.25 particles per 0.04μm2. 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.