Topological Band Gaps Enlarged in Epsilon-Near-Zero Magneto-Optical Photonic Crystals

Tianji Liu, Nobukiyo Kobayashi, Kenji Ikeda, Yasutomo Ota, Satoshi Iwamoto

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


Topological photonics provides exciting and emerging opportunities for the manipulation of light. As the photonic analogue of quantum Hall edge states, chiral edge modes, arising at the interface between two photonic topological structures with different Chern numbers, hold great promise for robust transport of light against disorders and defects. However, for magneto-optical material-based topological photonic crystals, the transport performance of chiral edge modes is strongly dependent on the topological gap sizes, which are usually very narrow at optical frequencies due to the lack of magneto-optical materials with strong nonreciprocal responses. Here, we numerically demonstrated that the introduction of an epsilon-near-zero effect to magneto-optical photonic crystals could remarkably enlarge topological gap sizes due to the boosted magneto-optical response. Eigenmode calculation resul show that the boosted magneto-optical response correlates to the enhanced nonreciprocal power flows in magnetized photon crystals with an epsilon-near-zero diagonal permittivity. The enlarged topological band gap leads to the broadband and well-confine chiral edge modes propagating along the magnetized boundary between two oppositely magnetized photonic crystals. Mo importantly, such mode propagation shows strong robustness against sharp bends and large defects. In principle, our proposal for t enlargement of topological photonic band gaps could also be valid in photonic crystal slabs or even three-dimensional photon crystals. Our results not only suggest the possibility to improve the transport performance of one-way modes in magneto-optic photonic crystals but also enrich the physical understanding of the epsilon-near-zero effect-based topological photonics.

Original languageEnglish
Pages (from-to)1621-1626
Number of pages6
JournalACS Photonics
Issue number5
Publication statusPublished - 2022 May 18


  • chiral edge modes
  • epsilon-near-zero effect
  • magneto-optical effect
  • one-way waveguide
  • topological band gap

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering
  • Biotechnology


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