The growth of augmented-reality (AR) technology has been hampered by the weight and bulkiness of AR glasses, which prevents prolonged wear. A breakthrough from the Pohang University of Science & Technology (POSTECH) in South Korea is now promising to change that.
image: POSTECH
One of the main hurdles to the commercialisation of AR glasses has been the waveguide. In AR optics, the lens itself also serves as a 'highway of light', guiding virtual images directly to the user’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.
Professor Junsuk Rho and colleagues at POSTECH have eliminated the need for multiple layers by developing an achromatic metagrating that handles all colours in a single glass layer. The key is a array of nanoscale silicon-nitride (Si3N4) pillars whose geometry was finely tuned by a stochastic topology-optimization algorithm to steer light with maximum efficiency.
In experiments, the researchers produced full-colour images using a 500-µm-thick single-layer waveguide—about one-hundredth the diameter of a human hair. They also secured a comfortable 9-mm eyebox, ensuring images remain sharp even if the viewer’s eye shifts slightly.
The new design erases colour blur while outperforming multilayer optics in brightness and color uniformity. Once commercialised, 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.