Topologically enabled ultrahigh-Q chiroptical resonances by merging bound states in the continuum

Ultrahigh-Q chiroptical resonance metasurfaces based on merging bound states in the continuum (BICs) are investigated and numerically demonstrated. The destruction of C-2 symmetry results in the leakage of BICs into quasi-BICs, and a chiral quasi-BIC is obtained by oblique incidence or continuous destruction of the mirror symmetry of the structure. Due to the significant topological properties of merging BICs, the Q factor (over 2x10(5)) of the chiral resonance peak obtained is much higher than that of the previous work. Moreover, the proposed structure is easy to fabricate because no additional out-of-plane asymmetry is introduced. The proposed scheme is of importance in chiral biosensing applications. (C) 2022 Optica Publishing Group

Automated summary

Ultrahigh-Q chiroptical resonance metasurfaces based on merging bound states in the continuum are investigated and numerically demonstrated. The destruction of C-2 symmetry leads to leakage of bound states into quasi-bound states, and a chiral quasi-bound state is obtained by oblique incidence or continuous destruction of the mirror symmetry. The resulting chiral resonance peak has a significantly higher Q factor (over 2x10^5) compared to previous work. The proposed structure is also advantageous in terms of fabrication simplicity, as no additional out-of-plane asymmetry is required. This research holds importance for chiral biosensing applications.