Continuously Geometrical Tuning to Boost Circular Dichroism in 3D Chiral Metamaterials

Chiral metamaterials possess unique optical chiral responses, and the attainment of remarkable intrinsic chirality typically necessitates the disruption of their mirror symmetry to facilitate cross‐coupling between electric and magnetic dipoles. However, achieving such symmetry breaking in a flexible and controllable manner remains challenging due to the limited range of applications afforded by available methodologies. Here, a method is proposed for fabricating robust three‐dimensional (3D) chiral metamaterials by projecting arbitrary planar chiral metasurfaces onto on‐demand height‐tunable 3D silicon structures, thereby effectively modulating their optical chiral responses through continuously tuning the degree of cross‐coupling between dipoles. Experimental and simulation results demonstrate this approach's ability to precisely control circular dichroism (CD) from a non‐chiral state to various activated and enhanced chirality. Enhancing CD with high precision and continuous control manners can naturally provide an advanced opportunity and platform for the future design and actual applications of chiral optical systems. This work presents a technique for fabricating robust 3D chiral metamaterials by projecting arbitrary planar chiral metasurfaces onto customizable and height‐adjustable 3D silicon structures. By altering the height of the spherical crown silicon substrate, the degree of cross‐coupling between the electric and magnetic dipoles can be regulated, thus allowing the CD response of the structure to be effectively controlled.