Korea’s POSTECH develops sub-millimeter waveguide to shrink AR glasses

12 May 2025

Researchers significantly reduce thickness and weight using a single-layer waveguide.

Augmented-reality technology is finding its way into everyday life, from education and healthcare to gaming and entertainment. However, the core AR device remains bulky and heavy, making prolonged wear uncomfortable. A breakthrough by researchers at Pohang University of Science and Technology (POSTECH), Korea, is promising to change that.

One of the main hurdles to the commercialization of AR glasses has been the waveguide. In AR optics, the lens itself also serves as a light channel, guiding virtual images directly to the observer’s eye. Due to chromatic dispersion, conventional designs have required separate waveguide layers for red, green, and blue light – three to six stacked glass sheets – inevitably increasing both weight and thickness of devices.

Professor Junsuk Rho and colleagues at POSTECH have eliminated the need for multiple layers by developing an achromatic metagrating that handles all colors in a single glass layer. The key is a array of nanoscale silicon-nitride (Si₃N₄) pillars whose geometry is finely tuned by a stochastic topology-optimization algorithm to steer light with maximum efficiency.

The achievement is described in Nature Nanotechnology.

Vivid full-color images

In experiments, the researchers have produced vivid full-color images using a 500-µm-thick single-layer waveguide. They also secured a comfortable 9-mm eyebox , ensuring images remain sharp even if the viewer’s eye shifts slightly. POSTECH explains that an eyebox is “the spatial region where an AR/VR display yields a clear image; larger eyeboxes provide consistent image quality across more viewing positions”.

The new design erases color blur while outperforming multilayer optics in brightness and color uniformity. Once commercialized, this technology could make AR glasses as thin and light as ordinary eyewear, reducing wearer fatigue and trimming manufacturing costs thanks to a simpler process. The era of truly everyday AR is a step closer.

“This work marks a key milestone for next-generation AR displays,” said Prof. Rho. “Coupled with scalable, large-area fabrication, it brings commercialization within reach.”

The study, authored by Junsuk Rho (corresponding author, POSTECH), Seokwoo Kim, Joohoon Kim, and Seokil Moon, was carried out by POSTECH’s Departments of Mechanical, Chemical and Electrical Engineering and the Graduate School of Interdisciplinary Bioscience & Bioengineering, in collaboration with the Visual Team at Samsung Research.