Fig. 1. Multi-dimensional control of radiation directionality and polarization patterns from twisted bi-layer metasurface.

a Twisted bi-layer metasurface and a schematic illustration of the two designs A1 (aligned discs) and D1 (displaced discs) exhibiting, respectively, intrinsically chiral and unidirectional chiral emission pattern in the top half-space as per experimentally measured emission in Fig. 4. Inset: Detailed maps of eigenpolarization and far-field amplitude in the top half-space for the design D1 exhibiting unidirectional chiral resonance. b Three designing parameters applied to the structure unit cell: twist angle $\theta$ between the y-axis and notches of the top and bottom discs, interlayer distance $H$, and lateral displacement ($\Delta X,\Delta Y$). The unit cell is characterized by pitch p, disc radius R, and thickness h, depth $d$ and width $w$ of rectangular notches. c Unit cell (top view) of bi-layer metasurfaces with possible lateral shifts ranging from −150 nm to 150 nm in both directions. d, e Corresponding maps of eigenpolarization and far-field amplitude for the anti-symmetric (lowest) resonant mode. Red and blue colors indicate elliptical polarizations with dominating RCP and LCP components, and black color indicates linear polarization. Filled circles indicate chiral resonances.