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.