$\mathcal{PT}$-Symmetry-Induced Wave Confinement and Guiding in Epsilon-Near-Zero Metamaterials

TL;DR

This paper demonstrates that epsilon-near-zero metamaterials with spatially modulated gain and loss can support stable, zero-attenuation interface modes, enabling novel waveguiding mechanisms for optical device applications.

Contribution

It introduces a new waveguiding mechanism in epsilon-near-zero metamaterials based on parity-time symmetry, supported by analytical and realistic material implementation studies.

Findings

Stable interface modes with zero attenuation are achievable in epsilon-near-zero metamaterials.

Waveguiding becomes leaky below a certain gain/loss threshold.

A rod-based metamaterial design effectively realizes the proposed waveguiding mechanism.

Abstract

Inspired by the parity-time symmetry concept, we show that a judicious spatial modulation of gain and loss in epsilon-near-zero metamaterials can induce the propagation of exponentially-bound interface modes characterized by zero attenuation. With specific reference to a bi-layer configuration, via analytical studies and parameterization of the dispersion equation, we show that this waveguiding mechanism can be sustained in the presence of moderate gain/loss levels, and it becomes leaky (i.e., radiative) below a gain/loss threshold. Moreover, we explore a possible rod-based metamaterial implementation, based on realistic material constituents, which captures the essential features of the waveguiding mechanism, in good agreement with our theoretical predictions. Our results may open up new possibilities for the design of optical devices and reconfigurable nanophotonics platforms.