Metalenses — flat surfaces that use nanostructures to focus light — are used in everything from microscopy to sensors, cameras, and displays. But so far, most of the lenses have been about the size of a piece of glitter. While lenses this size work well for some applications, a larger lens is needed for low-light conditions.
An all-glass, centimeter-scale metalens in the visible spectrum was developed that can be manufactured using conventional chip fabrication methods. The technology paves the way for wafer-level cameras for cellphones where the CMOS chip and the metalenses can be directly stacked on top of each other with easy optical alignment because they are both flat. In the future, the same company can make both the chip and the lenses because both can be made using lithography.
Previously, mass-production of centimeter-scale metalenses at visible wavelengths could not be achieved using electron-beam lithography or i-line stepper lithography. To mass-produce a centimeter-scale metalens, the researchers used a technique called deep-ultraviolet (DUV) projection lithography, which is commonly used to pattern very fine lines and shapes in silicon chips. The technique can produce many metalenses per chip, each made of millions of nanoscale elements with a single shot of exposure, like taking a photograph.
The researchers eliminated the time-consuming deposition processes that were required for previous metalenses by etching the nanostructure pattern directly onto a glass surface. It is the first mass-producible, all-glass, centimeter-scale meta-lens in the visible spectrum. While this lens is chromatic, meaning all the different colors of light don't focus at the same spot, the researchers are working on large-diameter achromatic metalenses.