A research team led by Professor Junsuk Rho and Dr. Seokwoo Kim from POSTECH has uncovered hidden repeating patterns within what seem to be disordered nanostructures. This discovery could lead to faster and more accurate methods for analyzing and designing advanced optical materials known as metasurfaces. The findings were published in the journal Nature Communications. Metasurfaces are ultra-thin materials composed of nanostructures—structures smaller than the wavelength of light—that can precisely control how light behaves, such as its direction and color. However, designing these surfaces has been a challenge because their nanostructures vary in size, shape, and orientation. This variation breaks the regular, repeating pattern of the surface, making it difficult to predict how light will interact with the material. Creating a single metasurface can involve over a billion nanostructures, which makes traditional computer simulations extremely slow and resource-intensive. As a result, researchers have often used simplified models or relied on large-scale simulations that are computationally expensive. The research team explored the idea that even seemingly complex structures might contain a hidden repeating order. They drew inspiration from Moiré patterns, which are large-scale interference patterns that form when two regular patterns are slightly misaligned. The team applied this concept to metasurfaces, viewing the basic structure and the variations used to control light as two overlapping patterns. Through mathematical analysis, they found that under certain conditions, a large-scale repeating pattern emerges, even in structures that appear random. This means that instead of analyzing each of the billions of nanostructures individually, researchers can focus on a small repeating unit of just tens of nanostructures, drastically reducing the complexity of the calculations. Using this new framework, the team built metasurface devices and confirmed that light was redirected as predicted. The method also allowed them to distinguish between the intended light paths and unwanted scattering, enabling faster and more accurate analysis. Because the principle is based on wave physics, the approach could apply to other systems involving sound, electrons, or mechanical vibrations. This discovery is expected to greatly accelerate the development of advanced optical technologies, including components for augmented and virtual reality and high-performance lenses.