Soliton metacrystals: topology and chirality

TL;DR

This paper introduces soliton-based metacrystals with unique topological and chiral properties, demonstrating their band structure, topological phases, and edge states, with potential applications across radio to terahertz frequencies.

Contribution

It presents the first demonstration of soliton metacrystals acting as electromagnetic metamaterials with topological and chiral features, using a novel periodic soliton array in microresonators.

Findings

Topological phases confirmed by Zak phase steps

Existence of phononic edge states in defected metacrystals

Spectral butterfly pattern indicating spatio-temporal chirality

Abstract

Designing metamaterials with the required band structure, topology and chirality using nano-fabrication technology revolutionises modern science and impacts daily life. The approach of this work is, however, different. We take a periodic sequence, i.e., metacrystal, of the dissipative optical solitons rotating in a single ring microresonator and demonstrate its properties as of the electromagnetic metamaterial acting in the radio to terahertz frequency range. The metacrystal unit cell consists of the bound pair of solitons, and the distance between them is used as a control parameter. We are reporting the soliton metacrystal band structure and its topological properties. The latter is confirmed by the existence of the $\pi$ steps experienced by the crystal phonons' geometrical (Zak) phase. Furthermore, we found the phononic edge states in the metacrystals with defects made by removing several solitons. Optical frequency combs corresponding to the soliton metacrystals reveal the spectral butterfly pattern serving as a signature of the spatio-temporal chirality and bearing a resemblance to the butterfly wings illustrating natural occurrences of chirality.