Optical detection of nano-particle characteristics using coupling to a nano-waveguide

Recently, much research concerning the combination of nano-scale waveguides with nano-crystals and other nano-particles has been reported because of possible applications in the field of quantum information and communication. The most useful and convenient method to verify the nature of such systems is optical detection. However, due to the diffraction limit, optical identification of characteristics such as particle type, particle position, etc., is difficult or impossible. However, if such particles are placed on a waveguide, the coupling of scattered light to the waveguide-guided modes can reveal the information about the particles. Here we consider how illumination with light of arbitrary polarization can reveal the difference between isotropic and non-isotropic nano-particles placed on the surface of an optical nanofiber. Specifically, we measure the polarization response function of gold nano-rods (GNRs) on an optical nanofiber surface and show that it is qualitatively different to that for gold nano-spheres (GNSs). This experimental technique provides a simple new tool for the optical characterization of hybrid nano-optical devices.