Metalenses promise potential for a paradigm shift of conventional optical devices. They comprise tiny, antenna-like surface patterns that can focus light to magnify distant objects in the same way as traditional curved glass lenses, but they have the advantage of being flat. The aperture sizes of metalenses are usually bound within hundreds of micrometers by the commonly used fabrication methods, limiting their usage on practical optical devices like telescopes. Researchers have now, for the first time, demonstrated a high-efficiency, single-lens, refractive metalens telescope. Their metalens works in the near-infrared region with nearly diffraction-limited focal spot sizes and a high peak focusing efficiency of 80.84%. Based on the metalens, they built a single-lens telescope and acquired images of the lunar surface, revealing its geographical structures.
“Traditional camera or telescope lenses have a curved surface of varying thickness, where you have a bump in the middle and thinner edges, which causes the lens to be bulky and heavy,” said Dr. Xingjie Ni, a researcher at the Pennsylvania State University.
“Metalenses use nano-structures on the lens instead of curvature to contour light, which allows them to lay flat.”
“That is one of the reasons, modern cellphone camera lenses protrude from the body of the phone: the thickness of the lenses take up space, though they appear flat since they are hidden behind a glass window.”
Metalenses are typically made using electron beam lithography, which involves scanning a focused beam of electrons onto a piece of glass, or other transparent substrate, to create antenna-like patterns point by point.
However, the scanning process of the electron beam limits the size of the lens that can be created, as scanning each point is time-consuming and has low throughput.
To create a bigger lens, Dr. Ni and colleagues adapted a fabrication method known as deep ultraviolet (DUV) photolithography, which is commonly…
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