# Negative refraction in time-varying, strongly-coupled plasmonic antenna-ENZ systems

## TL;DR

This paper demonstrates a novel time-varying metasurface combining plasmonic nano-antennas with ENZ materials, enabling efficient negative refraction and phase conjugation at the nanoscale through strong coupling and nonlinear effects.

## Contribution

It introduces a strongly coupled plasmonic-ENZ system that enhances nonlinear optical processes and enables negative refraction with high efficiency at the nanoscale.

## Key findings

- Achieved ~30% Rabi splitting of plasmonic and ENZ modes.
- Generated phase conjugate and negative refracted beams with high efficiency.
- Demonstrated a simple route to implement ENZ physics at the nanoscale.

## Abstract

Time-varying metasurfaces are emerging as a powerful instrument for the dynamical control of the electromagnetic properties of a propagating wave. Here we demonstrate an efficient time-varying metasurface based on plasmonic nano-antennas strongly coupled to an epsilon-near-zero (ENZ) deeply sub-wavelength film. The plasmonic resonance of the metal resonators strongly interacts with the optical ENZ modes, providing a Rabi level spitting of ~30%. Optical pumping at frequency {\omega} induces a nonlinear polarisation oscillating at 2{\omega} responsible for an efficient generation of a phase conjugate and a negative refracted beam with a conversion efficiency that is more than four orders of magnitude greater compared to the bare ENZ film. The introduction of a strongly coupled plasmonic system therefore provides a simple and effective route towards the implementation of ENZ physics at the nanoscale