Band Inversion Flips the Winding of Bound States in the Continuum
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arXiv
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| Main Authors: | , , , , , , , , , , , , |
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| Format: | Preprint |
| Published: |
2022
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| _version_ | 1866918491212218368 |
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| author | Bouteyre, Paul Nguyen, Dung Xuan Malgrey, Loïc Yuan, Zhiyi Gachon, Guillaume Benyattou, Taha Letartre, Xavier Viktorovitch, Pierre Callard, Ségolène Hu, Guangwei Fan, Shanhui Ferrier, Lydie Nguyen, Hai Son |
| author_facet | Bouteyre, Paul Nguyen, Dung Xuan Malgrey, Loïc Yuan, Zhiyi Gachon, Guillaume Benyattou, Taha Letartre, Xavier Viktorovitch, Pierre Callard, Ségolène Hu, Guangwei Fan, Shanhui Ferrier, Lydie Nguyen, Hai Son |
| contents | Bound states in the continuum (BICs) in photonic slabs and metasurfaces appear as polarization singularities in momentum space, characterized by an integer winding number. This winding is widely treated as a robust topological label, preserved under smooth deformations of the structure. Here we show that this robustness fails under band inversion. Using a general two-band theory of open periodic photonic structures, we prove that a band inversion at a band-edge BIC reverses the local far-field polarization map and flips the BIC winding, $w_{\rm BIC}\to -w_{\rm BIC}$, \emph{without} any defect dynamics in momentum space. We verify the prediction in a tunable subwavelength grating, where polarization tomography directly images the reversal, and confirm it numerically in multiband rectangular and triangular photonic lattices. Band inversion thus emerges as a key mechanism governing polarization-singularity topology in non-Hermitian photonic band structures. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2211_09884 |
| institution | arXiv |
| publishDate | 2022 |
| record_format | arxiv |
| spellingShingle | Band Inversion Flips the Winding of Bound States in the Continuum Bouteyre, Paul Nguyen, Dung Xuan Malgrey, Loïc Yuan, Zhiyi Gachon, Guillaume Benyattou, Taha Letartre, Xavier Viktorovitch, Pierre Callard, Ségolène Hu, Guangwei Fan, Shanhui Ferrier, Lydie Nguyen, Hai Son Optics Bound states in the continuum (BICs) in photonic slabs and metasurfaces appear as polarization singularities in momentum space, characterized by an integer winding number. This winding is widely treated as a robust topological label, preserved under smooth deformations of the structure. Here we show that this robustness fails under band inversion. Using a general two-band theory of open periodic photonic structures, we prove that a band inversion at a band-edge BIC reverses the local far-field polarization map and flips the BIC winding, $w_{\rm BIC}\to -w_{\rm BIC}$, \emph{without} any defect dynamics in momentum space. We verify the prediction in a tunable subwavelength grating, where polarization tomography directly images the reversal, and confirm it numerically in multiband rectangular and triangular photonic lattices. Band inversion thus emerges as a key mechanism governing polarization-singularity topology in non-Hermitian photonic band structures. |
| title | Band Inversion Flips the Winding of Bound States in the Continuum |
| topic | Optics |
| url | https://arxiv.org/abs/2211.09884 |