Quasi-bound states in the continuum (q-BICs) are resonant states of suitably tailored nanostructures with long optical lifetimes controlled by symmetry-breaking perturbations. While in planarized ultrathin devices the resulting Fano resonance is limited to linear polarizations, we show here that chiral perturbations extend q-BIC concepts to arbitrary elliptical polarizations. Using geometric phase engineering, we realize metasurfaces with ultrasharp Fano spectral features that can shape the impinging wavefront with near-unity efficiency, while at the same time precisely filtering their spectral content.
Observation of Chiral Bound States in the Continuum in Self-biased Magneto-optical Photonic Crystals
Southern University of Science and Technology（南方科技大学）；University of Electronic Science and Technology of China（电子科技大学）；Chongqing University of Technology（重庆理工大学）；Beijing Institute of Technology, Zhuhai（北京理工大学珠海学院）
Tunable high-$Q$ Janus-to-chiral bound states in the continuum in bilayer PhCs
School of Physics and Optoelectronics, Xiangtan University（湘潭大学物理与光电工程学院）；School of Physics and Electronics, Hunan University（湖南大学物理学院）；State Key Laboratory of Millimeter Waves, Southeast University（东南大学毫米波国家重点实验室）；Science, Mathematics and Technology (SMT) Cluster, Singapore University of Technology and Design（新加坡科技设计大学科学、数学与技术学部）
Chiral exceptional bound states in the continuum: a higher-order singularity for on-chip control of quantum emission
School of Integrated Circuits, Harbin Institute of Technology (Shenzhen)（哈尔滨工业大学（深圳）集成芯片学院）；Key Laboratory of Quantum Materials and Devices of Ministry of Education, School of Physics, Southeast University（东南大学物理学院量子材料与器件教育部重点实验室）；Institute for Quantum Science and Technology, National University of Defense Technology（国防科技大学量子科学与技术研究院）
Chiral lasing via broken parity-time symmetry in bound-state-in-the-continuum metasurfaces
ARC Centre of Excellence for Transformative Meta-Optical Systems (TMOS), Department of Electronic Materials Engineering, Research School of Physics, Australian National University（澳大利亚国立大学变革性超光学系统卓越中心）
Rewritable Chirality of Metasurfaces with Permittivity-Asymmetric Flatband Quasi-Bound States in the Continuum
Hamburg University of Technology（汉堡工业大学）；Ludwig- Maximilians-Universität München（慕尼黑大学）；Universidade Federal de Pernambuco（伯南布哥联邦大学）；National University of Science and Technology ‘MISIS’（国立科技大学 MISIS）；National Research Nuclear University ‘MEPhI’ (Moscow Engineering Physics Institute)（国立核研究大学 MEPhI（莫斯科工程物理学院））
