Observation of Polarization Topology in Magneto-Optical BICs
Abstract
Polarization topology in momentum space is a fundamental characteristic of photonic bound states in the continuum (BICs), where the winding of far-field polarization defines a quantized topological charge. Although magneto-optical (MO) BICs combine polarization topology with magnetically tunable chirality, experimental characterization remains challenging because time-reversal symmetry (TRS) breaking complicates eigenpolarization extraction. Here, we experimentally resolve the momentum-space polarization topology of an MO BIC by reconstructing its two-dimensional far-field eigenpolarization texture. We extract the resonant output polarization using singular value decomposition of the polarization-resolved angle-resolved reflection matrix without invoking reciprocity. The reconstructed polarization azimuth winds counterclockwise by 2π around the Γ-point singularity, yielding a topological charge of q = +1. Moreover, the polarization handedness can be reversed solely by varying the magnetic-bias strength, while the field direction and the measured topological charge remain unchanged. A non-Hermitian coupled-mode model traces this reversal to hybridization between the BIC mode and a leaky mode. This work establishes experimental access to momentum-space polarization topology in nonreciprocal photonics, opening a route to explore topological singularities and their evolution under active TRS breaking.
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BibTeX
@misc{li2026observation,
title = {{Observation of Polarization Topology in Magneto-Optical BICs}},
author = {Yaqi Li and Mingyu Tong and Fujia Chen and Li Zhang and Rui Zhao and Yuze Hu and Bei Wu and Haiyao Luo and Hongsheng Chen and Yihao Yang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.31498},
eprint = {2610.31498},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.31498},
}
RIS
TY - UNPB
TI - Observation of Polarization Topology in Magneto-Optical BICs
AU - Yaqi Li
AU - Mingyu Tong
AU - Fujia Chen
AU - Li Zhang
AU - Rui Zhao
AU - Yuze Hu
AU - Bei Wu
AU - Haiyao Luo
AU - Hongsheng Chen
AU - Yihao Yang
PY - 2026
DA - 2026/10/22
PB - arXiv
DO - 10.48550/arxiv.2610.31498
UR - https://arxiv.org/abs/2610.31498
AB - Polarization topology in momentum space is a fundamental characteristic of photonic bound states in the continuum (BICs), where the winding of far-field polarization defines a quantized topological charge. Although magneto-optical (MO) BICs combine polarization topology with magnetically tunable chirality, experimental characterization remains challenging because time-reversal symmetry (TRS) breaking complicates eigenpolarization extraction. Here, we experimentally resolve the momentum-space polarization topology of an MO BIC by reconstructing its two-dimensional far-field eigenpolarization texture. We extract the resonant output polarization using singular value decomposition of the polarization-resolved angle-resolved reflection matrix without invoking reciprocity. The reconstructed polarization azimuth winds counterclockwise by 2π around the Γ-point singularity, yielding a topological charge of q = +1. Moreover, the polarization handedness can be reversed solely by varying the magnetic-bias strength, while the field direction and the measured topological charge remain unchanged. A non-Hermitian coupled-mode model traces this reversal to hybridization between the BIC mode and a leaky mode. This work establishes experimental access to momentum-space polarization topology in nonreciprocal photonics, opening a route to explore topological singularities and their evolution under active TRS breaking.
ER -