Record-breaking Metal Materials May Bring A Revolution In Optical Technology

Traditional lenses—such as those found in spectacles—are bulky and heavy, and can only focus light of a limited wavelength. Researchers at the University of California, Berkeley have developed a new type of ultra-thin metal that uses a set of tiny, connected together like a fishing net to focus light in the visible to infrared bands with record-breaking efficiency.
Unlike traditional lenses, this metal lens is flat and compact, and can be made small enough to accommodate increasingly miniaturized equipment. This development may lead to breakthroughs in solar energy, virtual reality technology, medical imaging, optical information processing, and other applications that rely on optics.
"We have overcome obstacles that are considered basic," said Bubacar Kanter, the lead researcher of the study, an associate professor of electrical engineering and computer science at the University of California, Berkeley and a scientist at the Lawrence Berkeley National Laboratory. "To put it simply, this is the thinnest, most effective, and widest flat lens in the world."

Although many methods for realizing flat lenses have been proposed in the past decade, the emergence of new metals is the first time this combination of properties has been realized. The research team demonstrated the ability of its fishnet colorless metal to capture 70% of incident light with a frequency range from 640 nanometers (red-orange light) to 1200 nanometers (infrared light). In the octave wide wavelength band, the light entering the mesh metal will be focused on a single point on the other side of the lens.
"We are very excited about these results because many applications need to handle multiple wavelengths over a broad spectrum at the same time," Kante said. "This is the case of solar applications. We need to concentrate all colors of light to make efficient solar cells or solar concentrators." Kanter said that the next step is to develop a process that can achieve mass production.

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