Selected Mode Mixing and Interference Visualized within a Single Optical Nanoantenna

Abstract

Interference-based directional antennas typically consist of multiple dipoles with properly set distances and phases, which cause constructive interferences toward certain directions in radiation or reception. For nano-optical antennas, the directionality can be realized by superposition of multiple eigenmodes in a single structure. Such mode mixing creates locally strong field enhancement, which should be properly controlled for energy conversion or sensing applications. However, experimental verification of the nano-optical field, or especially the hot-spots, created by interference of selected eigenmodes is not trivial. We here visualize how optical fields are distributed when multiple modes interfere within a silver disk nanoantenna. We use angle- and polarization-resolved cathodoluminescence based on scanning transmission electron microscopy to select specific modes and visualize the field distribution at the nanoscale. The interfered field distribution significantly changes depending on the detectio...