Alignment-Free Bilayer Moiré Metasurfaces with Tunable Twist Angles

We prepared moiré metasurfaces comprising a stack of nanoantenna layers, where the first and second layers are twisted to each other. Consequently, chirality appears even though each layer is achiral. The fabrication of such an out-of-plane anisotropic nanostructure is not straightforward even with nanolithographic techniques. The present method utilizes a nanoantenna sticker, which is a periodic array of nanoparticles embedded in a flexible polymer. The sticker is self-adhesive and survives multiple peel-off and stick-on processes. By placing the sticker onto another nanoparticle array on a substrate with a specific twist angle in between, the moiré metasurface can be easily prepared. We examined the circular dichroism and found that it is tunable by the twist angle and the interlayer distance and that it is independent of the lateral displacement of the layers. Such an alignment-free stacking process is appealing for exploring chirality and moiré-related photonics, e.g., flat-band engineering and photon localization.