From smartphones and TVs to credit cards, technologies that manipulate light are deeply embedded in our daily lives. However, conventional holographic technologies have faced limitations, particularly in displaying multiple images on a single screen and maintaining high-resolution image quality. Researchers at Pohang University of Science and Technology developed a metasurface technology that can display up to 36 high-resolution images on a surface thinner than a human hair. The research team fabricated nanometer-scale pillars using silicon nitride, a material known for its robustness and excellent optical transparency. These pillars, referred to as meta-atoms, allow for fine control of light on the metasurface. Schematic of the single-cell "metahologram" implementing spin and wavelength multiplexing. Courtesy of Pohang University of Science and Technology. This technology can project entirely different images depending on both the wavelength and polarization direction of light. For example, left-circularly polarized red light may reveal an image of an apple, while right-circularly polarized red light may produce an image of a car. Using this technique, the researchers were able to encode 36 images at 20-nm intervals within the visible spectrum, and eight images spanning from the visible to the near-infrared region, all on a single metasurface. The team addressed previous issues of image crosstalk and background noise by incorporating a noise suppression algorithm, which resulted in clearer images and minimal interference between channels. “This is the first demonstration of multiplexing spin and wavelength information through a single phase-optimization process while achieving low noise and high image fidelity,” said research team leader professor Junsuk Rho. “Given its scalability and commercial viability, this technology holds strong potential for a wide range of applications, including high-capacity optical data storage, secure encryption systems, and multi-image display technologies.” This research was published in Advanced Science (www.doi.org/10.1002/advs.202504634).