Energy-Momentum Cathodoluminescence Imaging of Anisotropic Directionality in Elliptical Aluminium Plasmonic Bullseye Antennas

We show that geometric eccentricity can be used to strongly tailor the angular radiation profiles of aluminium plasmonic bullseye antennas. High-resolution energy/momentum maps are recorded using a novel cathodoluminescence Fourier imaging technique. The angular profiles for elliptical bullseyes (ellipticity e = 0, 0.6, 0.8) are well described by a 2D dipole scattering model in which the phase and amplitude of the scattering from the bullseye grooves dictates the angular profile at a given energy. We show that geometric eccentricity is an important parameter to control the radiation profile of bullseye antennas. The new energy-momentum cathodoluminescence imaging technique can be used to map the optical properties of a wide range of dispersive and anisotropic systems, paving the way for a broad range of studies on complex nanophotonic systems.