The study of chiral light-matter interactions is one of the most cutting-edge research fields in optics. The artificial chiral plasmonic nanostructures, for example nanohelix and twisted multilayer structures, are widely adopted to enhance the circular dichroism. However, the sign reversal of circular dichroism usually requires the drastic mirror operation for most of the chiral nanostructures proposed so far.

To address this issue, the team of Professors Jiafang Li and Yugui Yao from the School of Physics recently proposed and demonstrated an artificial propeller meta-molecule with twisted blades, which exhibit abnormal optical propeller chirality induced by the phase-controllable chiral surface lattice resonances (SLRs). The chiral SLRs are formed by the coupling of chiral electric quadrupole modes to the diffractive lattice mode. It has been shown that the periodic array of the propeller meta-molecules can form hybridized structures with two chiral centers. As a result, it was revealed that circular dichroism response can be readily reversed by tailoring the interference phase through zooming the length of structural blades, rotating the blades or increasing blades twist height without inverting the geometric chirality. Such observations are all verified by nano-kirigami experiments and published in Nano Lett., 2021, 21: 6828-6834, Adv. Opt. Mater., 2021, 9: 2101191 and APL Photonics, 2022, 7: 056102.

Fig. 1 Geometric designs in changing the sign of circular dichroism.

Fig. 2 Nano-kirigami prepared two nearly identical bi-chiral propeller meta-molecular arrays and observed sign reversal of circular dichroism.