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Realization of a three-dimensional photonic topological insulator

Authors :
Hongsheng Chen
Zhaoju Yang
Mengjia He
Yihao Yang
Ranjan Singh
Baile Zhang
Haoran Xue
Yidong Chong
Li Zhang
Zhen Gao
School of Physical and Mathematical Sciences
Centre for Disruptive Photonic Technologies
The Photonics Institute
Source :
Nature. 565:622-626
Publication Year :
2019
Publisher :
Springer Science and Business Media LLC, 2019.

Abstract

Confining photons in a finite volume is highly desirable in modern photonic devices, such as waveguides, lasers and cavities. Decades ago, this motivated the study and application of photonic crystals, which have a photonic bandgap that forbids light propagation in all directions1–3. Recently, inspired by the discoveries of topological insulators4,5, the confinement of photons with topological protection has been demonstrated in two-dimensional (2D) photonic structures known as photonic topological insulators6–8, with promising applications in topological lasers9,10 and robust optical delay lines11. However, a fully three-dimensional (3D) topological photonic bandgap has not been achieved. Here we experimentally demonstrate a 3D photonic topological insulator with an extremely wide (more than 25 per cent bandwidth) 3D topological bandgap. The composite material (metallic patterns on printed circuit boards) consists of split-ring resonators (classical electromagnetic artificial atoms) with strong magneto-electric coupling and behaves like a ‘weak’ topological insulator (that is, with an even number of surface Dirac cones), or a stack of 2D quantum spin Hall insulators. Using direct field measurements, we map out both the gapped bulk band structure and the Dirac-like dispersion of the photonic surface states, and demonstrate robust photonic propagation along a non-planar surface. Our work extends the family of 3D topological insulators from fermions to bosons and paves the way for applications in topological photonic cavities, circuits and lasers in 3D geometries. A three-dimensional photonic topological insulator is presented, made of split-ring resonators with strong magneto-electric coupling, which has an extremely wide topological bandgap, forbidding light propagation.

Details

ISSN :
14764687 and 00280836
Volume :
565
Database :
OpenAIRE
Journal :
Nature
Accession number :
edsair.doi.dedup.....389e78f4c504d637c77dd6130cf3e5c8
Full Text :
https://doi.org/10.1038/s41586-018-0829-0