volume | PIER Journals

Abstract

The modulation of topological polarization singularities in momentum space in photonics has attracted much attention due to their relations with bound states in the continuum (BICs), unidirectional guided resonances, and chirality. Current modulation strategies that rely on structural symmetry breaking or phase-change materials are challenging to achieve dynamic and flexible modulation of polarization singularities. Recently, magneto-optical (MO) modulation of light provides a promising theoretical strategy for the dynamic modulation of polarization singularities. However, the dynamics of transverse electric (TE)/transverse magnetic (TM)-mode singularities under varying magnetic fields remain elusive in the MO photonic crystal (PhC) slab. Herein, we systematically investigate the dynamic modulation of topological polarization singularities in the PhC slab based on the MO effect. In-plane (x/y) magnetic fields have no effect on the TE mode of the MO PhC slab. However, the fields induce splitting and separation of vortex polarization singularity (V point) of the TM mode into a pair of circular polarization points (C points), enabling extrinsic chirality without breaking the structural symmetry. A magnetic field along the z direction enables near-unity circular dichroisms (CDs) over a broad angular range when circular polarizations are formed at off-Γ points for the TE and TM modes. Furthermore, by introducing single symmetry breaking (in-plane symmetry breaking for TE, out-of-plane symmetry breaking for TM) with magnetic field tuning, one of the C points can be shifted to the Γ point, resulting in intrinsic chiral quasi-BICs (QBICs) with ultra-high Q-factors and near-unity CDs. This study provides a dynamic and flexible modulation approach for polarization singularities, which enhances light-matter interactions for applications in advanced chiral photonic devices and tunable optoelectronic devices.

1. Berry, Michael V., "The singularities of light: Intensity, phase, polarisation," Light: Science & Applications, Vol. 12, No. 1, 238, 2023.
doi:10.1038/s41377-023-01270-8

2. Liu, Wenzhe, Wei Liu, Lei Shi, and Yuri Kivshar, "Topological polarization singularities in metaphotonics," Nanophotonics, Vol. 10, No. 5, 1469-1486, 2021.
doi:10.1515/nanoph-2020-0654

3. Wang, Feifan, Xuefan Yin, Zixuan Zhang, Zihao Chen, Haoran Wang, Peishen Li, Yuefeng Hu, Xinyi Zhou, and Chao Peng, "Fundamentals and applications of topological polarization singularities," Frontiers in Physics, Vol. 10, 862962, 2022.
doi:10.3389/fphy.2022.862962

4. Hsu, Chia Wei, Bo Zhen, A. Douglas Stone, John D. Joannopoulos, and Marin Soljačić, "Bound states in the continuum," Nature Reviews Materials, Vol. 1, No. 9, 16048, 2016.
doi:10.1038/natrevmats.2016.48

5. Zhen, Bo, Chia Wei Hsu, Ling Lu, A. Douglas Stone, and Marin Soljačić, "Topological nature of optical bound states in the continuum," Physical Review Letters, Vol. 113, No. 25, 257401, 2014.
doi:10.1103/physrevlett.113.257401

6. Liu, Wenzhe, Bo Wang, Yiwen Zhang, Jiajun Wang, Maoxiong Zhao, Fang Guan, Xiaohan Liu, Lei Shi, and Jian Zi, "Circularly polarized states spawning from bound states in the continuum," Physical Review Letters, Vol. 123, No. 11, 116104, 2019.
doi:10.1103/physrevlett.123.116104

7. Zeng, Yixuan, Guangwei Hu, Kaipeng Liu, Zhixiang Tang, and Cheng-Wei Qiu, "Dynamics of topological polarization singularity in momentum space," Physical Review Letters, Vol. 127, No. 17, 176101, 2021.
doi:10.1103/physrevlett.127.176101

8. Yin, Xuefan, Jicheng Jin, Marin Soljačić, Chao Peng, and Bo Zhen, "Observation of topologically enabled unidirectional guided resonances," Nature, Vol. 580, No. 7804, 467-471, 2020.
doi:10.1038/s41586-020-2181-4

9. Yin, Xuefan, Takuya Inoue, Chao Peng, and Susumu Noda, "Topological unidirectional guided resonances emerged from interband coupling," Physical Review Letters, Vol. 130, No. 5, 056401, 2023.
doi:10.1103/physrevlett.130.056401

10. Ni, Xueqi, Yuan Liu, Beicheng Lou, Mingjie Zhang, Evelyn L. Hu, Shanhui Fan, Eric Mazur, and Haoning Tang, "Three-dimensional reconfigurable optical singularities in bilayer photonic crystals," Physical Review Letters, Vol. 132, No. 7, 073804, 2024.
doi:10.1103/physrevlett.132.073804

11. Zheng, Bao Jie, Wei Jie Shi, Hui Yuan Dong, Yong Tao Li, Jia Qi Li, Zheng-Gao Dong, and Jin Wang, "Dynamical control of topological unidirectional guided resonances via external magnetic field," Physical Review Research, Vol. 7, No. 1, 013091, 2025.
doi:10.1103/physrevresearch.7.013091

12. Huang, Lujun and Andrey E. Miroshnichenko, "Evolution of topological polarization singularity in a photonic crystal slab," Laser & Photonics Reviews, Vol. 19, No. 18, e00555, 2025.
doi:10.1002/lpor.202500555

13. Kang, Meng, Shunping Zhang, Meng Xiao, and Hongxing Xu, "Merging bound states in the continuum at off-high symmetry points," Physical Review Letters, Vol. 126, No. 11, 117402, 2021.
doi:10.1103/physrevlett.126.117402

14. Jin, Jicheng, Xuefan Yin, Liangfu Ni, Marin Soljačić, Bo Zhen, and Chao Peng, "Topologically enabled ultrahigh-Q guided resonances robust to out-of-plane scattering," Nature, Vol. 574, No. 7779, 501-504, 2019.
doi:10.1038/s41586-019-1664-7

15. Kang, Meng, Li Mao, Shunping Zhang, Meng Xiao, Hongxing Xu, and Che Ting Chan, "Merging bound states in the continuum by harnessing higher-order topological charges," Light: Science & Applications, Vol. 11, No. 1, 228, 2022.
doi:10.1038/s41377-022-00923-4

16. Ye, Weimin, Yang Gao, and Jianlong Liu, "Singular points of polarizations in the momentum space of photonic crystal slabs," Physical Review Letters, Vol. 124, No. 15, 153904, 2020.
doi:10.1103/physrevlett.124.153904

17. Chen, Zihao, Xuefan Yin, Jicheng Jin, Zhao Zheng, Zixuan Zhang, Feifan Wang, Li He, Bo Zhen, and Chao Peng, "Observation of miniaturized bound states in the continuum with ultra-high quality factors," Science Bulletin, Vol. 67, No. 4, 359-366, 2022.
doi:10.1016/j.scib.2021.10.020

18. Liang, Yao, Kirill Koshelev, Fengchun Zhang, Han Lin, Shirong Lin, Jiayang Wu, Baohua Jia, and Yuri Kivshar, "Bound states in the continuum in anisotropic plasmonic metasurfaces," Nano Letters, Vol. 20, No. 9, 6351-6356, 2020.
doi:10.1021/acs.nanolett.0c01752

19. Liang, Yao, Din Ping Tsai, and Yuri Kivshar, "From local to nonlocal high-Q plasmonic metasurfaces," Physical Review Letters, Vol. 133, No. 5, 053801, 2024.
doi:10.1103/PhysRevLett.133.053801

20. Doeleman, Hugo M., Francesco Monticone, Wouter den Hollander, Andrea Alù, and A. Femius Koenderink, "Experimental observation of a polarization vortex at an optical bound state in the continuum," Nature Photonics, Vol. 12, No. 7, 397-401, 2018.
doi:10.1038/s41566-018-0177-5

21. Hsu, Chia Wei, Bo Zhen, Jeongwon Lee, Song-Liang Chua, Steven G. Johnson, John D. Joannopoulos, and Marin Soljačić, "Observation of trapped light within the radiation continuum," Nature, Vol. 499, No. 7457, 188-191, 2013.
doi:10.1038/nature12289

22. Gorkunov, Maxim V., Alexander A. Antonov, and Yuri S. Kivshar, "Metasurfaces with maximum chirality empowered by bound states in the continuum," Physical Review Letters, Vol. 125, No. 9, 093903, 2020.
doi:10.1103/physrevlett.125.093903

23. Shi, Tan, Zi-Lan Deng, Guangzhou Geng, Xianzhi Zeng, Yixuan Zeng, Guangwei Hu, Adam Overvig, Junjie Li, Cheng-Wei Qiu, Andrea Alù, Yuri S. Kivshar, and Xiangping Li, "Planar chiral metasurfaces with maximal and tunable chiroptical response driven by bound states in the continuum," Nature Communications, Vol. 13, No. 1, 4111, 2022.
doi:10.1038/s41467-022-31877-1

24. Chen, Yang, Huachun Deng, Xinbo Sha, Weijin Chen, Ruize Wang, Yu-Hang Chen, Dong Wu, Jiaru Chu, Yuri S. Kivshar, Shumin Xiao, and Cheng-Wei Qiu, "Observation of intrinsic chiral bound states in the continuum," Nature, Vol. 613, No. 7944, 474-478, 2023.
doi:10.1038/s41586-022-05467-6

25. Kodigala, Ashok, Thomas Lepetit, Qing Gu, Babak Bahari, Yeshaiahu Fainman, and Boubacar Kanté, "Lasing action from photonic bound states in continuum," Nature, Vol. 541, No. 7636, 196-199, 2017.
doi:10.1038/nature20799

26. Huang, Can, Chen Zhang, Shumin Xiao, Yuhan Wang, Yubin Fan, Yilin Liu, Nan Zhang, Geyang Qu, Hongjun Ji, Jiecai Han, et al., "Ultrafast control of vortex microlasers," Science, Vol. 367, No. 6481, 1018-1021, 2020.
doi:10.1126/science.aba4597

27. Ha, Son Tung, Yuan Hsing Fu, Naresh Kumar Emani, Zhenying Pan, Reuben M. Bakker, Ramón Paniagua-Domínguez, and Arseniy I. Kuznetsov, "Directional lasing in resonant semiconductor nanoantenna arrays," Nature Nanotechnology, Vol. 13, No. 11, 1042-1047, 2018.
doi:10.1038/s41565-018-0245-5

28. Chen, Ang, Wenzhe Liu, Yiwen Zhang, Bo Wang, Xiaohan Liu, Lei Shi, Ling Lu, and Jian Zi, "Observing vortex polarization singularities at optical band degeneracies," Physical Review B, Vol. 99, No. 18, 180101, 2019.
doi:10.1103/physrevb.99.180101

29. Liu, Zhuojun, Yi Xu, Ye Lin, Jin Xiang, Tianhua Feng, Qitao Cao, Juntao Li, Sheng Lan, and Jin Liu, "High-Q quasibound states in the continuum for nonlinear metasurfaces," Physical Review Letters, Vol. 123, No. 25, 253901, 2019.
doi:10.1103/PhysRevLett.123.253901

30. Wang, Bo, Wenzhe Liu, Maoxiong Zhao, Jiajun Wang, Yiwen Zhang, Ang Chen, Fang Guan, Xiaohan Liu, Lei Shi, and Jian Zi, "Generating optical vortex beams by momentum-space polarization vortices centred at bound states in the continuum," Nature Photonics, Vol. 14, No. 10, 623-628, 2020.
doi:10.1038/s41566-020-0658-1

31. Yoda, Taiki and Masaya Notomi, "Generation and annihilation of topologically protected bound states in the continuum and circularly polarized states by symmetry breaking," Physical Review Letters, Vol. 125, No. 5, 053902, 2020.
doi:10.1103/physrevlett.125.053902

32. Zhou, Huanyu, Xueqi Ni, Beicheng Lou, Shanhui Fan, Yuan Cao, and Haoning Tang, "Control of chirality and directionality of nonlinear metasurface light source via moiré engineering," Physical Review Letters, Vol. 134, No. 4, 043801, 2025.
doi:10.1103/PhysRevLett.134.043801

33. He, Haoxuan, Lulu Wang, Hong Duan, Xia Yan, Ying Zhang, Shengyun Luo, Yingfei Yi, and Chaobiao Zhou, "Topological polarization singularity modulation in the phase change material metasurfaces," IEEE Photonics Technology Letters, Vol. 37, No. 14, 805-808, 2025.
doi:10.1109/lpt.2025.3565577

34. Yao, Enxu, Zhaoxian Su, Yu Bi, Yongtian Wang, and Lingling Huang, "Tunable quasi-bound states in the continuum in magneto-optical metasurfaces," Journal of Physics D: Applied Physics, Vol. 57, No. 37, 375104, 2024.
doi:10.1088/1361-6463/ad5215

35. Lv, Wenjing, Haoye Qin, Zengping Su, Chengzhi Zhang, Jiongpeng Huang, Yuzhi Shi, Bo Li, Patrice Genevet, and Qinghua Song, "Robust generation of intrinsic C points with magneto-optical bound states in the continuum," Science Advances, Vol. 10, No. 46, eads0157, 2024.
doi:10.1126/sciadv.ads0157

36. Tu, Qing-An, Hongxin Zhou, Dong Zhao, Yan Meng, Maohua Gong, and Zhen Gao, "Magnetically tunable bound states in the continuum with arbitrary polarization and intrinsic chirality," Photonics Research, Vol. 12, No. 12, 2972-2982, 2024.
doi:10.1364/prj.539830

37. Zhao, Chen, Shaohua Dong, Qing Zhang, Yixuan Zeng, Guangwei Hu, and Yongzhe Zhang, "Magnetic modulation of topological polarization singularities in momentum space," Optics Letters, Vol. 47, No. 11, 2754-2757, 2022.
doi:10.1364/ol.458285

38. Zhao, Xingqi, Jiajun Wang, Wenzhe Liu, Zhiyuan Che, Xinhao Wang, C. T. Chan, Lei Shi, and Jian Zi, "Spin-orbit-locking chiral bound states in the continuum," Physical Review Letters, Vol. 133, No. 3, 036201, 2024.
doi:10.1103/physrevlett.133.036201

39. Yang, Bo, Wanhua Zheng, and Anjin Liu, "Magnetically tunable ultra-high Q-factor intrinsic chirality based on merging bound states in the continuum," Optics Express, Vol. 33, No. 16, 34960-34973, 2025.
doi:10.1364/oe.570814

40. Zhang, Yiwen, Ang Chen, Wenzhe Liu, Chia Wei Hsu, Bo Wang, Fang Guan, Xiaohan Liu, Lei Shi, Ling Lu, and Jian Zi, "Observation of polarization vortices in momentum space," Physical Review Letters, Vol. 120, No. 18, 186103, 2018.
doi:10.1103/physrevlett.120.186103

41. Wu, Jiaju, Jingguang Chen, Xin Qi, Zhiwei Guo, Jiajun Wang, Feng Wu, Yong Sun, Yunhui Li, Haitao Jiang, Lei Shi, Jian Zi, and Hong Chen, "Observation of accurately designed bound states in the continuum in momentum space," Photonics Research, Vol. 12, No. 4, 638-647, 2024.
doi:10.1364/prj.515969

42. Haider, Taskeya, "A review of magneto-optic effects and its application," International Journal of Electromagnetics and Applications, Vol. 7, No. 1, 17-24, 2017.
doi:10.5923/j.ijea.20170701.03

43. Buschow, K. H. J., Handbook of Magnetic Materials, Vol. 15, Elsevier, 2003.

44. Jesenska, Eva, Tomohiko Yoshida, Kenji Shinozaki, Takayuki Ishibashi, Lukas Beran, Martin Zahradnik, Roman Antos, Miroslav Kučera, and Martin Veis, "Optical and magneto-optical properties of Bi substituted yttrium iron garnets prepared by metal organic decomposition," Optical Materials Express, Vol. 6, No. 6, 1986-1997, 2016.
doi:10.1364/ome.6.001986

45. Rizal, Conrad, Hiromasa Shimizu, and Jorge Ricardo Mejía-Salazar, "Magneto-optics effects: New trends and future prospects for technological developments," Magnetochemistry, Vol. 8, No. 9, 94, 2022.
doi:10.3390/magnetochemistry8090094

46. Yang, Weihao, Qing Liu, Hanbin Wang, Yiqin Chen, Run Yang, Shuang Xia, Yi Luo, Longjiang Deng, Jun Qin, Huigao Duan, and Lei Bi, "Observation of optical gyromagnetic properties in a magneto-plasmonic metamaterial," Nature Communications, Vol. 13, No. 1, 1719, 2022.
doi:10.1038/s41467-022-29452-9

47. Wang, Zheng and Shanhui Fan, "Magneto-optical defects in two-dimensional photonic crystals," Applied Physics B, Vol. 81, No. 2, 369-375, 2005.
doi:10.1007/s00340-005-1846-x

48. Zhang, Keqian and Dejie Li, Electromagnetic Theory for Microwaves and Optoelectronics, Springer, 1998.
doi:10.1007/978-3-662-03553-5

49. Li, Junqing, Zhixu Wu, Dandan Zhang, Yong Sun, Wenxing Liu, and Tianbao Yu, "Nonreciprocal toroidal dipole resonance and one-way quasi-bound state in the continuum," Optics Letters, Vol. 49, No. 5, 1313-1316, 2024.
doi:10.1364/ol.516427

50. Li, Min, Guangwei Hu, Xuan Chen, Cheng-Wei Qiu, Hongsheng Chen, and Zuojia Wang, "Topologically reconfigurable magnetic polaritons," Science Advances, Vol. 8, No. 50, eadd6660, 2022.
doi:10.1126/sciadv.add6660

51. Li, Shiyu, Chaobiao Zhou, Tingting Liu, and Shuyuan Xiao, "Symmetry-protected bound states in the continuum supported by all-dielectric metasurfaces," Physical Review A, Vol. 100, No. 6, 063803, 2019.
doi:10.1103/physreva.100.063803

52. Zhao, Wen Kui, Sheng Yi Wang, Yu Hang Jing, Hua Ge, Qiu Wang, Yong Quan Zeng, Bo Wen Jia, and Ning Xu, "Giant structurally modulated intrinsic chirality of quasi-bound states in continuum," Optics Letters, Vol. 50, No. 5, 1649-1652, 2025.
doi:10.1364/ol.549705

53. Zhang, Yanyu, Qianju Song, Bin Hou, and Zao Yi, "Steerable intrinsic chirality mediated by toroidal dipole bound states in the continuum in an active metasurface," Optics Letters, Vol. 50, No. 9, 2868-2871, 2025.
doi:10.1364/ol.558495

Dr. Bo Yang

Dr. Wanhua Zheng

Professor Anjin Liu