Researchers have developed innovative flat, optical lenses as part of a collaboration between NASA’s Jet Propulsion Laboratory and the California Institute of Technology. These optical components are capable of manipulating light in ways that are difficult or impossible to achieve with conventional optical devices.
The new lenses aren’t made of glass. Instead, silicon nanopillars are precisely arranged into a honeycomb pattern to create a “metasurface” that can control the paths and properties of passing light waves. Applications of these devices include advanced microscopes, displays, sensors and cameras that can be mass-produced using the same techniques used to manufacture computer microchips.
“These flat lenses will help us make more-compact and robust imaging assemblies,” said Mahmood Bagheri, a microdevices engineer at JPL and co-author of a new Nature Nanotechnology study describing the devices.
“Currently, optical systems are made one component at a time, and the components are often manually assembled,” said Andrei Faraon, an assistant professor of applied physics and materials science at Caltech, and the study’s principal investigator. “But this new technology is very similar to the one used to print semiconductor chips onto silicon wafers, so you could conceivably manufacture millions of systems, such as microscopes or cameras, at a time.”
Seen under a scanning electron microscope, the new metasurfaces resemble a cut forest where only the stumps remain. Each silicon stump, or pillar, has an elliptical cross section, and by carefully varying the diameters of each pillar and rotating them around their axes, the scientists were able to simultaneously manipulate the phase and polarization of passing light.
“If you think of a modern microscope, it has multiple components that have to be carefully assembled inside,” Faraon says. “But with our platform, we can actually make each of these optical components and stack them atop one another very easily using an automated process. Each component is just a millionth of a meter thick, or less than a hundredth of the thickness of a human hair.”