Aperiodic order is back in the spotlight. A team at the Institute of Industrial Science, The University of Tokyo has engineered optical structures inspired by the “Smith hat,” a rare geometric tile that solves the decades-old Einstein tiling problem while avoiding any repeating pattern. Their new work goes beyond the mathematics, using light to reveal how this single-shape tiling behaves in ways conventional quasicrystals do not.
The Einstein problem asks whether one monotile can cover a plane without ever forming a periodic arrangement. The Smith hat answers yes: it tiles space aperiodically, yet it is built from an underlying honeycomb lattice. That hidden connection motivated the researchers to test whether the optical consequences might also be unexpectedly structured.
Using electron-beam lithography, the group patterned nanoscale features onto silicon nitride films. When illuminated with laser light, the fabricated aperiodic monotile structures produced diffraction signatures with a distinctly “pinwheel” look—an immediate optical clue that the pattern is chiral.
Chirality is not just a geometric curiosity here. The team reports that the diffraction pattern itself becomes chiral because the aperiodic structure lacks mirror symmetry. In other words, the optical response inherits handedness from the arrangement of the monotile, shifting the usual rules compared with mirror-symmetric quasicrystalline materials.
Even more striking, the observed diffraction pattern depends on the direction and polarization of the incoming light. This means the system’s optical behavior can be reconfigured simply by changing how the laser is presented to the sample, without altering the fabricated structure.
The researchers further show that mirror-image versions of the structure generate corresponding reversals in optical response, demonstrating a symmetry-controlled mechanism linking real-space chirality to far-field diffraction outcomes.
These results suggest a new route for “twisting” photonics: combining quasiperiodic order with chirality could enable devices that manipulate polarization and wavefronts in robust, geometry-encoded ways. Beyond applications, the study highlights how an abstract tiling breakthrough can unlock new physics when translated into engineered optical matter.
The findings were published in Nature Communications under the title “Chiral Diffraction from Aperiodic Monotile Structure,” with DOI 10.1038/s41467-026-75023-7.
Subject of Research: Chiral diffraction from an aperiodic monotile (Smith hat) optical structure
Article Title: Chiral Diffraction from Aperiodic Monotile Structure
News Publication Date: 29-Jul-2026
Web References: https://www.doi.org/10.1038/s41467-026-75023-7
References: 10.1038/s41467-026-75023-7
Image Credits: Institute of Industrial Science, The University of Tokyo
Keywords
Aperiodic monotile, Einstein tiling problem, Smith hat, chiral diffraction, quasicrystals, symmetry, polarization, nanophotonics, laser illumination, optical response
Tags: Aperiodic tiling in optical structureschirality in aperiodic materialsEinstein tiling problemelectron-beam lithography on silicon nitridelaser illumination of aperiodic structuresnanoscale lithography for optical engineeringnon-repeating geometric patternsoptical consequences of aperiodic orderquasicrystalline diffraction patternsSmith hat monotilestructure-handedness in quasicrystalssymmetry breaking in optical diffraction
