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arXiv · 2401.15845

Extremely intrinsic chirality in two-dimensional planar waveguide grating induced by quasi-bound states in the continuum

Dandan Zhang·Tingting Liu·Linlin Lei·Weimin Deng·Tongbiao Wang·Qinghua Liao·Wenxing Liu·Shuyuan Xiao·Tianbao Yu
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Abstract

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 ultrahigh 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 $\pi$/2. For an illustration, a planar chiral dielectric dimeric waveguide grating is designed that strong interacts with left circularly polarized (LCP) light while decouples from right circularly polarized (RCP) 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 nearly 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.

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Dandan Zhang, Tingting Liu, Linlin Lei, Weimin Deng, Tongbiao Wang, Qinghua Liao, Wenxing Liu, Shuyuan Xiao, Tianbao Yu. 2024-01-29. Extremely intrinsic chirality in two-dimensional planar waveguide grating induced by quasi-bound states in the continuum. https://doi.org/10.1103/physrevb.109.205403

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