{
  "abstract": "The topological charge of a bound state in the continuum (BIC) can flip when the BIC merges with other polarization singularities or, as recently shown, at band flips. Here, using a coupled-mode analysis, we derive an analytical expression for the topological charge of symmetry-protected BICs in one-dimensional single-layer photonic lattices. The expression captures both merging-induced and band-flip-induced charge flips. We find that, during a band flip, the topological charge of the BIC reverses with the formation of lines of circular polarization that cross at the $Γ$ point. In vertically symmetric lattices, each charge flip occurs simultaneously in the upward and downward radiation channels. Breaking vertical symmetry makes both kinds of charge flips channel-differentiated, creating a parameter interval in which the BIC carries opposite topological charges in the two channels and forms a Janus BIC. We show that Janus BICs also emerge in experimentally accessible one- and two-dimensional silicon-based photonic lattices. Our results link the topological charge of a BIC directly to the band structure and the channel-resolved radiation amplitudes and establish a basis for channel-selective control of polarization singularities.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.37168",
  "author_total": 2,
  "authors": [
    {
      "name": "Sun-Goo Lee"
    },
    {
      "name": "Wook-Jae Lee"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/39q9e8cxekndp.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.37168",
  "fulltext_url": null,
  "id": "39q9e8cxekndp",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.37168",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "physics.optics"
    ],
    [
      "openalex",
      "3107|Topological Materials and Phenomena"
    ]
  ],
  "openalex": "W7224122177",
  "pdf_url": "https://arxiv.org/pdf/2610.37168",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-27",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/39q9e8cxekndp.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:35:50Z",
      "native_id": "2610.37168",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.37168"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.optics",
      "subfield": "optics-photonics"
    }
  ],
  "title": "Channel-Differentiated Topological Charge Flips and Formation of Janus Bound States in the Continuum in Single-Layer Photonic Lattices",
  "title_text": "Channel-Differentiated Topological Charge Flips and Formation of Janus Bound States in the Continuum in Single-Layer Photonic Lattices",
  "type": "preprint",
  "updated_at": "2026-10-30T12:35:50Z",
  "url": "https://research.draconitic.com/paper/39q9e8cxekndp",
  "venue": "arXiv",
  "versions": []
}