Asymptotically exact photonic analogues of chiral symmetric topological tight-binding models

TL;DR

This paper demonstrates that void-channel networks can serve as asymptotically exact photonic analogues of chiral symmetric topological tight-binding models, enabling robust topological edge states in continuum photonic systems.

Contribution

It introduces a method to realize topological photonic models using void-channel networks that asymptotically replicate discrete tight-binding models with short-range interactions.

Findings

Void-channel systems map to discrete models at low frequencies.

Photonic analogues of SSH and square-root semimetals are realized.

Provides a basis for exploring continuum topological photonics.

Abstract

Topological photonic edge states, protected by chiral symmetry, are attractive for guiding wave energy as they can allow for more robust guiding and greater control of light than alternatives; however, for photonics, chiral symmetry is often broken by long-range interactions. We look to overcome this difficulty by exploiting the topology of networks, consisting of voids and narrow connecting channels, formed by the spaces between closely spaced perfect conductors. In the limit of low frequencies and narrow channels, these void-channel systems have a direct mapping to analogous discrete mass-spring systems in an asymptotically rigorous manner and therefore only have short-range interactions. We demonstrate that the photonic analogues of topological tight-binding models that are protected by chiral symmetries, such as the SSH model and square-root semimetals, are reproduced for these void-channel networks with appropriate boundary conditions. We anticipate, moving forward, that this paper provides a basis from which to explore continuum photonic topological systems, in an asymptotically exact manner, through the lens of a simplified tight-binding model.