Opt Lett. 2023 Feb 15;48(4):916-919. doi: 10.1364/OL.482857.
Although toroidal dipole (TD) resonance is a highly localized mode with a high quality (Q) factor, in most chiral structures the TD resonance is much weaker than the electric or magnetic dipole resonances and contributes little to the chiral response. In this Letter, we theoretically propose a chiral all-dielectric TD metasurface that possesses giant optical chirality with a certain degree of incident-angle robustness induced by a strong TD resonance. Interestingly, the symmetry of the system can be broken simultaneously at oblique incidence to produce chiral quasi-bound states in the continuum. The nearly unchanged high-Q TD resonance within a certain range of incident angles can avoid the problem of a reduced image quality caused by the incident-angle sensitivity, as demonstrated by the polarization-multiplexed-field image displays. The giant chirality with a certain degree of incident-angle robustness induced by the TD mode would be useful in some applications, including high-quality optical imaging, high-performance asymmetric transmission, and sensing.
虽然环形偶极子（TD）共振是一种具有高 Q 因子的高度局域模式，但在大多数手性结构中，TD 共振比电偶极子或磁偶极子共振弱得多，对手性响应的贡献很小。在这封信件中，我们理论上提出了一种具有巨大光学手性的手性全介质 TD 超表面，它具有由强 TD 共振引起的一定程度的入射角稳健性。有趣的是，在斜入射时，系统的对称性可以同时被打破，从而产生连续的手性准束缚态。在一定入射角范围内，几乎不变的高 Q TD 共振可以避免由于入射角灵敏度导致的图像质量下降的问题，这一点通过偏振复用场图像显示得到了验证。由 TD 模式引起的具有一定入射角稳健性的巨大手性将在手性应用中非常有用，包括高质量的光学成像、高性能的非对称传输和传感。
