Ultrahigh spatial resolution imaging of radiative optical states of single gold nanoantennas by scanning tunneling microscope-induced light emission

Modern nanophotonics allows one to engineer the optical modes and localize light at the nanoscale. In this work, we visualize the local density of optical states (LDOS) distribution of the single femtosecond-laser-printed gold nanobump with ultrahigh spatial resolution. Scanning tunneling microscope-induced light emission allows us to achieve LDOS mapping with a spatial resolution of around 15 nm for single nanobumps and their agglomerates with gold plasmonic nanoantennas, having a relatively small diameter. Our experimental and theoretical results show that a plasmonic nanoantenna can be integrated into an optical system to enhance its radiation outcoupling efficiency, while leaving its modal structure mainly unaffected. A deep understanding of the optical modes in nanostructures opens up possibilities for creating new types of optoelectronic components based on inelastically tunneling electrons, providing light emission.