Fig. 1. IET based plasmon nanoantennas. (a) Schematic diagram of the generation of surface plasmons and photons by IET in a plasmonic tunneling junction; (b) electroluminescence (open circles) and scattering spectra (solid lines) for different antenna geometries and a non-resonant wire several micrometers long, the left column shows electron micrographs of the corresponding structures^[36]; (c) spectral intensity of the emitted light for all four devices at Vb = 2.5 V (open circles) in comparison with the optical transmission enhancement (solid lines), the left column shows the corresponding images of light emitted from the devices^[37]; (d) schematic diagram of tunnel junction structure composed of edge-to-edge assembled single-crystal silver cubes^[38]; (e) simulated (green shaded) and experimental (red and black squares) EQE for various sizes of Ag nanobar-based tunnel junctions, and the insets are corresponding SEM images of the samples^[38]; (f) dependence of EQE of an resonant IET-enabled plasmonic source on the applied bias^[39]; (g) schematic diagram of an electrically-driven Au nanorod array^[40]; (h) photograph of an electrically-driven Au nanorod array with an applied bias of 2.5 V^[40]

Fig. 2. Guided wave mode excitation based on IET. (a) Schematic diagram of the device for tunnel junction formation between STM tip and gold nanowires^[42]; (b) photon emission map superimposed to the SEM image of a Au nanowire excited by a STM tip at its left end, inset shows the intensity map along the nanowire^[42]; (c) schematic diagram of the integration of silver nanowires and metal-insulator-graphene tunnel junctions^[44]; (d) superposition of the luminescence image and bright field image of the metal-insulator-graphene tunnel junction with an applied bias of 2.2 V, with white dashed lines indicating the outline of the graphene layer^[44]; (e) superposition of luminescent images and SEM images of the coupling structure between tunnel junctions and semiconductor nanowires with an applied bias of 2.5 V, with white dashed lines indicating the outline of the graphene layer^[44]; (f) schematic diagram of a luminescent tunnel junction inside a hybrid plasmon cavity coupling emitted light to a waveguide^[48]; (g) transverse magnetic mode emission spectrum of a 2 μm long light emitting tunnel junctions device^[48]

Fig. 3. Plasmonic tunnel junctions for plasmon/photon-electron conversion. (a) Field enhancement (left axis) as a function of gap distance (top axis) for five devices measured a number of times, inset shows a SEM image of the nanogap^[50]; (b) structure of an on-chip electronic-plasmonic transducer consisting of two tunnel junctions connected to a plasmonic waveguide^[43]; (c) time trace of the response current density varying with the input signal at different detection biases^[43]; (d) schematic illustration of an optical wireless transducing link^[55]; (e) the relationships between the transduced current and the applied bias for three distant optical antennas^[55]; (f) instantaneous tunneling current (red line) and accumulated electronic charge per pulse (black line), the inset shows a SEM image of an optical bowtie antenna with electric contacts^[56]; (g) experimental setup of the optical pulses driven electron tunneling in a STM^[58]