Optical Chirality Enhancement in Hollow Silicon Disk by Dipolar Interference

Optical chirality enhancement is highly demanded for enantioselective interaction of circularly polarized light with chiral molecules. The chirality enhancement in the coaxial air hole of a hollow silicon disk depends on three aspects, namely, the enhancements of electric and magnetic fields and a factor determined by the phases of their field components. In the spectral regime of dipole resonances, maximum chirality enhancement with sign consistency and uniform spatial distribution in the air hole can be obtained in association with both magnetic dipole resonance and anapole. Due to dipolar interference, the chirality is nulled at their coincidence, around which the sign of chirality is reversed. Maximum chirality with both positive and negative signs can be found between magnetic dipole resonance and anapole in the vicinity of their coincidence. This situation is maintained under size scaling so that the operation wavelength can be broadly tuned. The optical chirality can be further improved by merely adjusting the hole radius, by which the optimal spatially averaged optical chirality enhancement factor can reach 39 and -23. The simple strategy for optimizing Mie resonators presented in this work may benefit the design of Mie resonator-based achiral metasurfaces for chirality detection application.

Automated summary

The study found that maximum chirality enhancement can be achieved by adjusting the magnetic dipole resonance and anapole in coaxial air holes, and the chirality can be reversed in the vicinity of these points. Further improvement in optical chirality can be achieved by adjusting the hole radius, with the optimal enhancement factor reaching 39 and -23.