Tailoring intrinsic chirality in a two-dimensional planar waveguide grating via quasibound states in the continuum

作者：Dandan Zhang, Tingting Liu, Linlin Lei, Wei‐Min Deng, Tongbiao Wang, Qinghua Liao, Wenxing Liu, Shuyuan Xiao, Tianbao Yu · 发表于：Physical review. B./Physical review. B · 年份：2024 · DOI：10.1103/physrevb.109.205403 · 被引用次数：30 · 研究领域：Metamaterials and Metasurfaces Applications、Optical Coatings and Gratings、Orbital Angular Momentum in Optics

The strong chiral light-matter interaction is crucial for various important fields such as chiral optics, quantum optics, and biomedical optics, driving a quest for the extreme intrinsic chirality assisted by ultra-high-quality ($Q$-) factor resonances. In this quest we propose a straightforward method to achieve extreme intrinsic chirality in lossless planar structures by manipulating the quasi-BIC through in-plane perturbation. The temporal coupled-mode theory is employed to derive the conditions necessary for achieving maximal intrinsic chirality. The quasi-BIC should be excited within the transparent spectral range of the structure and couple with $x$- and $y$-polarized waves with the same intensity but a phase difference of $\ensuremath{\pi}/2$. For an illustration, a planar chiral dielectric dimeric waveguide grating is designed that strongly interacts with left circularly polarized light while decoupling from right circularly polarized light through in-plane symmetry engineering. Furthermore, by adjusting the magnitude of the in-plane asymmetry, we can independently manipulate the $Q$ factors of the chiral quasi-BIC while maintaining near unity circular dichroism. Our results provide a simple yet powerful paradigm for achieving extreme intrinsic chirality on an easily manufacturable platform, which may have potential applications in chiral emission, chiral sensing, and enantiomer separation.