Tunable circular dichroism based on chiral photonic crystals

Chiroptical effects, which include the dichroism of left and right circularly polarized light, can be observed in structures made up of nanoscale chiral elements. We introduce a holistically nondestructive tunable chiral perforated photonic crystal film. The structure exhibits a strong photon spin selection effect at a wavelength of 810 nm, resulting in a significant circular dichroism (CD) value. The origin of the chiral response is explained using linear superposition theory, and the authors also discovered a strong chirality near-field enhancement at 796 and 810 nm, which could be used in molecular chirality sensing and other fields. By adjusting related parameters, the unit structure can greatly impact the reflection spectrum of the CD value. These chiral photonic crystal films may have potential applications as polarization management devices in the future.