Probing light propagation at nanostructures

Efficient nanofocusing of light might be achieved through metallic nanoantenna structures, such as nanoparticle arrays, slot waveguides or tapered plasmonic waveguides. To address the flow and confinement of light in such structures we probe locally the optical field and its phase development with our heterodyning near field microscope. The detailed nanometric field amplitude and phase maps allow retrieving all spatial frequencies and map out the dispersion. Moreover, we can disentangle all propagating and evanescent waves, and point out any sub-wavelength field confinement.