Meta-Atom Coupling Induced Chiral Hotspot in Silicon Nitride Staggered Nanorods Meta-Surface.

Dielectric meta-surfaces have emerged as an effective way for fabricating chiral optical devices, and the chiral meta-surfaces are usually constituted by periodic chiral meta-atom structures. Here, we report a chiral meta-surface consisting of nonchiral silicon nitride rectangular nanorods. The chiral hotspots are generated between the staggered nanorods due to the coupling between the two nearest neighbor nanorod units. 14.6% macroscopic circular dichroism (CD) is achieved experimentally with larger area staggered nanorods. Meanwhile, we demonstrate that the wavelength tuning capability of this design from 696 to 820 nm by simply modulating the overlap length of nanorods. Our work highlights the mechanisms for CD hotspot generation without complex chiral units, which paves a novel way for future on-chip photon-spin selective devices.