Exceptional points in a topological photonic system

TL;DR

This paper demonstrates the emergence of exceptional points in a topological photonic system, revealing new opportunities for robust optical devices with unique properties derived from non-Hermitian physics.

Contribution

It introduces a novel topological photonic architecture that hosts exceptional points, linking topological insulators with non-Hermitian degeneracies.

Findings

Exceptional points cause parity-time symmetry breaking.

Transmission spectra show characteristic dips at exceptional points.

Topological design enables robust, symmetry-breaking optical phenomena.

Abstract

Exceptional points as branch singularities describe peculiar degeneracies of non-Hermitian systems that do not obey energy conservation. This work shows that exceptional points can emerge in a topological photonic system, for example, the topological photonic waveguide coupled with two degenerate counter-propagation topological whispering gallery modes. Such a photonic architecture is designed by crystal-symmetry-protected topological photonic insulators based on air rods in conventional dielectric materials. The relevant exceptional point reveals the breaking of the parity-time symmetry, reflected by the change of the transmission-dip number in the optical transmission spectra of the system. Achieving exceptional points in topological photonic systems possibly opens a new avenue toward robust optical devices with exceptional-point-based unique properties and functionalities.