Engineers recently came up with a new framework of optical lenses that can offer a strong alternative for traditional curved lenses. This can further enhance the possibility for lighter and cheaper cameras that can be embedded in your medical devices as well as smartphones. These new lenses are carved from sheets of a special material called metasurfaces. Every single metasurface lens comes dotted with millions of mini sized cylinders known as silicon nanoposts. These are around 600 nm tall and have several diameters in a range of some hundred nanometers.
These silicon nanoposts permit the metasurfaces to act like lenses by copying the behavior of customary curved lenses. Customarily, these lenses were made from glass and were curved in a manner that light would travel faster via its lean edges as compared to the thick center that focused light rays. A similar effect can be achieved by varying the silicon nanoposts diameter. Light goes faster through those nanoposts that have smaller diameters as compared with nanoposts with larger diameters, in crux, these nanoposts are capable of replicating the final effect of curved lenses despite the fact that all nanoposts are present over a flat surface.
The final trick that was used by these engineers was to stack two distinct metasurface lenses over each other's top and nanopost side-out to form a metasurface of doublet lens. The technique has been used to rectify monochromatic aberrations that take place when a single metasurface is used. The final lens framework grabs and focuses light rays from one angle-of-view that is greater than 60 x 60 degrees and works at a wavelength of 850nm that has around 70 percent focusing efficiency. Researcher Amir Arbabi says, “Metasurfaces like these can be easily mass produced, much the way computer chips are. That means this could be a cheap and easily scalable way to create tiny lenses just a few millimeters in diameter."