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 10 nm diameter gold particles with a density of fewer than 1.25 particles per 0.04 mum(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. (C) 2004 American Institute of Physics.