LAUSR

In recent years, the field of plasmonics has stimulated intensive research for diverse applications, with electron energy-loss spectroscopy (EELS) based techniques becoming a primary tool for high spatial resolution near-field mapping of plasmonic eigenmodes [1]. However, strong absorption losses limit the performance of metallic plasmonic nanostructures for various nanophotonic applications. A promising strategy to overcome this is to use electric and magnetic Mie-type resonances in dielectric nanoparticles [2]. Compared to metallic plasmonic excitations, these resonances present some key differences [3]: they are driven by displacement currents rather than actual currents (hence their low optical absorption losses); the charge displacement and hence resonant eigenmodes are supported within the volume of the nanoparticle, rather than on the surface; in addition to the excitation of electric modes, the driving of displacement current loops can produce magnetic resonant modes. Until now, sub-wavelength imaging of these resonant modes has been limited to near field optical microscopy, e.g. [4], and a few studies using cathodoluminescence (CL), e.g. [5, 6]. Here, we report on the first EELS studies of resonant eigenmodes in silicon dielectric nanoparticles of varying size and geometry.