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The final single-color lens is developed on a plate and resembles silicon chips before they’re put into larger circuits. Credit: ©2024 Konishi et al. CC-BY-ND
Researchers have developed a groundbreaking method to produce Fresnel zone plates — paper-thin optical lenses — using standard semiconductor manufacturing techniques.
These lenses, though less efficient at present, hold the promise of revolutionizing industries from astronomy to consumer electronics with their potential for mass production and application-specific design.
Redefining Optical Device Manufacturing
Paper-thin optical lenses, simple enough for mass production using microchip manufacturing methods, could pave the way for a new generation of compact optical devices. Researchers from the University of Tokyo and JSR Corp. have fabricated and tested flat lenses known as Fresnel zone plates (FZPs) using common semiconductor manufacturing equipment, specifically the i-line stepper. This marks the first time such lenses have been produced with this approach. While these flat lenses currently lack the efficiency of conventional lenses, they hold significant potential to revolutionize optics across industries like astronomy, healthcare, and consumer electronics.
Although flat lenses, such as metalenses, already exist, they are expensive, complex, and limited in availability. Manufacturers, driven by the need for higher quality, better performance, and lower costs, are exploring alternative technologies with the help of academic researchers. FZPs have emerged as a promising solution, especially for applications where space is at a premium. For the first time, researchers successfully produced sample lenses through a simple and efficient process using standard industry machinery.
An industry standard optical precision test shows the resolution of the FZP test lenses. The white scale bar is 5 micrometers. Credit: ©2024 Konishi et al. CC-BY-ND
Breakthrough in Lens Production Technology
“We developed a simple and mass-producible method for FZPs using a common semiconductor lithography system, or stepper,” said Associate Professor Kuniaki Konishi from the Institute for Photon Science and Technology. “This is due to a special type of photoresist or mask called a color resist, which was originally designed for use as color filters. By simply coating, exposing, and developing this material, we produced lenses capable of focusing visible light down to only 1.1 microns, around 100 times thinner than a human hair.”
The current drawback with the new FZPs is that they only have a light-gathering efficiency of 7%, meaning they produce excessively noisy images. But already the team is working on ways to increase this fourfold by changing the way they use the color resists. However, this would require a greater degree of control over the color resists’ physical properties than was afforded the researchers at the time of this study, though the ability to do this does exist.
The process of lithography, on which the researchers’ method is based, is a little like developing a pre-digital chemical photograph. Credit: ©2024 Konishi et al. CC-BY-ND
Future Prospects and Environmental Benefits
“In addition to efficiently fabricating FZPs, we also devised simulations which are confirmed to match our experiments very tightly. What this means is, we could tailor designs to match specific applications in different fields, such as medicine, before committing to production,” said Konishi. “Furthermore, we envisage environmental and economic benefits too, as unlike traditional manufacturing methods, the FZP production process eliminates the need for toxic etching chemicals and significantly reduces energy consumption.”
So, it might be a while before FZPs help you capture moments in high visual fidelity with your ultrathin smartphone, but this, or technology inspired by it, will likely come along soon.
Reference: “Optical Fresnel zone plate flat lenses made entirely of colored photoresist through an i-line stepper” by Ryohei Yamada, Hiroyuki Kishida, Tomohiro Takami, Itti Rittaporn, Mizuho Matoba, Haruyuki Sakurai and Kuniaki Konishi, 16 January 2025, Light: Science & Applications.
DOI: 10.1038/s41377-024-01725-6
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