Chirality encoding in resonant metasurfaces governed by lattice symmetries.

Chiral metasurfaces provide invaluable tools for controlling structured light required for biosensing, photochemistry, holography, and quantum photonics. Here we suggest and realize a universal strategy for engineering chiral response of resonant metasurfaces via the interplay of meta-atom geometry and lattice arrangements within all five possible planar Bravais symmetries. By introducing chiral gradient metasurfaces, we illustrate how our approach allows producing a predictable chiral response tunable by simple parameter variations. We highlight that the symmetry-controlled chiral response provides an additional degree of freedom in optical signal processing, and showcase this with simultaneous mid-IR image encoding in two fundamental quantities, transmission and circular dichroism. Our proposed concept represents a universal toolkit for on-demand design and control of chiral metastructures that has potential for numerous applications in life sciences, quantum optics and more.