Efficient and Unidirectional Launching of Surface Plasmons from a Hyperbolic Meta‐Antenna

Tunnel nanojunctions associated with inelastic electron tunneling have demonstrated crucial applications in on‐chip photonic and plasmonic circuitries due to their high photon modulation speed, large‐scale integration capability, and working‐wavelengths range tunability. However, because most electrons tunnel through a junction elastically, the external quantum efficiency of a nanojunction‐based plasmonic source tends to be around 10 −4 , severely limiting their applications to date. In this work, an integrated high‐efficiency unidirectional plasmonic source composed of an edge‐to‐edge thickness gradient hyperbolic meta‐antenna is proposed. By engineering the extra wavevector dimension, this study demonstrates a theoretical external quantum efficiency of up to 23% for this system. This is attributed to the large local density of optical states from hyperbolic dispersion and wavevector‐match conditions provided by the optical antennas. Furthermore, this study also demonstrates the tunability of this system across a range of wavelengths from 1300 to 1700 nm. The implementations of these metamaterial‐based tunneling structures enable fast and tunable on‐chip high‐efficiency sources for applications in high‐performance plasmonic circuitries.