This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: AR and VR glasses once seen only in science fiction may soon be realized not as bulky stacks of lenses but as a single eyeglass-like optical element. That future is now closer to reality.
A research team at Pohang University of Science and Technology (POSTECH) has developed technologies for producing sharp full-color images using metalenses and published the findings in Nature Communications. The achievement is drawing attention because it addresses two major challenges for commercializing metalenses: high optical performance and scalable manufacturing. A metalens is an ultrathin lens made of densely arranged nanoscale structures that control the path of light as intended.
Unlike conventional optics, which often require multiple stacked glass lenses, a metalens can perform similar functions in a single flat optical element, making it a key component for lightweight, compact devices such as AR and VR glasses. The challenge lies in achieving achromatic performance, which means focusing red, green and blue light at the same point without color blur. Realizing this performance using low-refractive-index materials, which are inexpensive and suitable for mass production, has been extremely challenging.
The research team solved this issue by controlling the height of nanoscale pillars known as meta-atoms, which form the metalens. While previous approaches mainly controlled light by adjusting the lateral width of meta-atoms, the team added height as a new design parameter. Just as buildings with the same footprint can create different cityscapes by varying their number of floors, meta-atoms built to different heights can precisely focus RGB light at the desired focal point.
In the first study, the team directly fabricated complex three-dimensional nanopillars using two-photon lithography, a high-precision 3D printing technique. They built a database of various nanopillar designs and used an inverse-design approach to automatically select the most suitable structure for each position on the metalens. As a result, they realized a full-color achromatic metalens using relatively low-cost, low-refractive-index materials and confirmed sharp color imaging in experiments that integrated the metalens with an OLED display.
The second study focused on mass production. The team fabricated a height-encoded nano-template using grayscale electron-beam lithography and applied it to nanoimprint lithography, a stamping-like replication process. Conventional nanoimprint methods are generally suited for repeatedly printing patterns with the same height, but this new technology enables structures with different heights to be replicated at once, improving both optical performance and production scalability.
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