Magnetically tunable bound states in the continuum with arbitrary polarization and intrinsic chirality  

作　　者：QING-AN TU HONGXIN ZHOU DONG ZHAO YAN MENG MAOHUA GONG ZHEN GAO 

机构地区：[1]State Key Laboratory of Optical Fiber and Cable Manufacturing Technology,Department of Electronic and Electrical Engineering,Guangdong Key Laboratory of Integrated Optoelectronics Intellisense,Southern University of Science and Technology,Shenzhen 518055,China [2]School of Electrical Engineering and Intelligentization,Dongguan University of Technology,Dongguan 523808,China

出　　处：《Photonics Research》2024年第12期2972-2982,共11页光子学研究(英文版)

基　　金：National Natural Science Foundation of China(62361166627,62375118,12104211,12304484);Guangdong Basic and Applied Basic Research Foundation(2024A1515011371,2024A1515012770);Science,Technology and Innovation Commission of Shenzhen Municipality(20220815111105001,202308073000209);High Level of Special Funds(G03034K004).

摘　　要：Bound states in the continuum(BICs),which are exotic localized eigenstates embedded in the continuum spectrum and exhibit topological polarization singularities in momentum space,have recently attracted great attention in both fundamental and applied physics.Here,based on a magneto-optical(MO)photonic crystal(PhC)slab placed in external magnetic fields with time-reversal symmetry(TRS)breaking,we theoretically propose magnetically tunable BICs with arbitrary polarization covering the entire Poincarésphere and efficient off-Γchiral emission of circularly polarized states(C point).More interestingly,by further breaking the in-plane inversion symmetry of the MO PhC slab to generate a pair of C points spawning from the eliminated BICs and tuning the external magnetic field strength to move one C point to theΓpoint,an at-Γintrinsic chiral BIC exhibits chiral characteristics on both sides of the PhC slab with near-unity circular dichroism exceeding 0.99 and a high-quality factor of 46,000 owing to the preserved out-of-plane mirror symmetry.Moreover,the chirality of the chiral BICs can be inverted by flipping the magnetic bias.Our work opens an unprecedented avenue to explore the unique topological photonics of BICs with broken TRS and promises multiple applications in chiraloptical effects,structured light,and tunable optical devices.

关 键 词：polarization BREAKING TOPOLOGICAL 

分 类 号：O469[理学—凝聚态物理]