This webinar presents a new series of nanoscale components based on a reversible transduction between electron and a photon using optical gap antennas. At the core of the device is an atomic-scale tunnel gap whereby optical rectification, inelastic tunneling, and hot carriers can reciprocally mix photons and electrons with ultrafast conversion dynamics. We discuss the peculiarity of the broadband spectrum emitted from the antenna feed by a decaying population of hot electrons. The source can be readily integrated to plasmonic and photonic waveguides. The co-integration of atomic-scale optical functional devices with an electronic transduction offers a disruptive solution to interface photons and electrons at this ultimate length scale.