Unidirectional propagation of electrically driven surface plasmon polaritons: a numerical study

Electrically excited surface plasmon polaritons (SPPs) created, for instance, through the energy loss from inelastic electron tunneling, have received great interest recently because of their potential for facilitating the integration of on-chip information processing elements. Consequently, finding a convenient method of realizing the propagation control of such a kind of SPPs becomes a valuable research topic. Optical antennas array, with a relatively large footprint, are commonly used for steering SPPs. In this paper, with the aid of two plasmonic strip-type antennas that are placed next to each other, we present a feasible method of propagation control of electrically driven SPPs in a scanning tunneling microscope (STM) system. Results show that STM-induced SPPs propagate along a preferred direction due to the in-plane SPP interference effects, which can be easily engineered by the widths of the antennas. This result is very useful for compact plasmonic circuits design.