Hybrid Epsilon-Near-Zero Modes of Photonic Gap Antennas

TL;DR

This paper introduces hybrid epsilon-near-zero (ENZ) modes in photonic gap antennas, demonstrating giant field enhancements, high emission rates, and unidirectional radiation, advancing antenna design for light concentration and emission control.

Contribution

It reveals the emergence of hybrid ENZ modes in dielectric antennas, combining strong coupling and resulting in significant field and emission enhancements, analyzed via quasinormal mode theory.

Findings

Hybrid ENZ modes exhibit giant electric field enhancements.

Far-field spontaneous emission rate is significantly increased.

Antennas achieve nearly perfect unidirectional emission.

Abstract

We demonstrate that in photonic gap antennas composed of an epsilon-near-zero (ENZ) layer embedded within a high-index dielectric, hybrid modes emerge from the strong coupling between the ENZ thin film and the photonic modes of the dielectric antenna. These hybrid modes show giant electric field enhancements, large enhancements of the far-field spontaneous emission rate and a unidirectional radiation response. We analyze both parent and hybrid modes using quasinormal mode theory and find that the hybridization can be well understood using a coupled oscillator model. Under plane wave illumination, hybrid ENZ antennas can concentrate light with an electric field amplitude $\sim$100 times higher than that of the incident wave, which places them on par with the best plasmonic antennas. In addition, the far-field spontaneous emission rate of a dipole embedded at the antenna hotspot reaches up to $\sim$2300 that in free space, with nearly perfect unidirectional emission.