Breakthrough ultrathin lens could lead to phones as thin as a credit card
Flat, distortion-free, and small — very, very small — these lenses stand to revolutionize technology
A revolutionary new lens that’s flat, distortion-free, and so small that 1,500 of them could fit across the width of a human hair, stands the very real possibility of one day being incorporated in technologies that range from cameras to cell phones to fiber-optic communication systems.
Researchers have managed to create an ultrathin flat lens able to focus light without imparting the distortions of conventional lenses.
Details of the breakthrough lens appear in the American Chemical Society’s journal, Nano Letters , under the title “Aberration-Free Ultrathin Flat Lenses and Axicons at Telecom Wavelengths Based on Plasmonic Metasurfaces.”
A much needed update
Today’s lenses, which are used to focus light in everything from eyeglasses to microscopes, use the same technology that dates back to the late 1200s (when spectacles were first introduced to Europe).
They are not thin nor are they flat enough to remove distortions like spherical aberration, astigmatism, and coma, all of which prevent the user from seeing a true, sharp image.
Correcting these distortions requires complex solutions like using multiple lenses. But these present their own problems; with multiple lenses, the user is then increasing weight and also taking up more space.
The new superthin flat lens
At just 60 nanometers thick, the flat lens is basically two dimensional, yet still has a resolving power that approaches the theoretical limits set by the laws of optics.
Researchers from Harvard, Texas A&M, and others abroad were able to create the lens by plating a very thin wafer of silicon with a nanometer-thin layer of gold. After that, they stripped away parts of the gold to leave behind an array of V-shaped structures, all evenly spaced in rows across the surface.
When the group shined a laser on the flat lens, these V-shaped structures acted more or less like nanoantennas that capture the incoming light and hold onto it briefly before releasing it again.
These slightly delays are precisely tuned across the surface of the lens, and change the direction of the light in the same way that a thick glass less would.
Furthermore, the array of nanoantennas, dubbed a “metasurface”, can be tuned for specific wavelengths of light simply by changing the size, angle, and spacing of the antennas.
“Our flat lens opens up a new type of technology,” says principal investigator Federico Capasso, Robert L. Wallace Profe ssor of Applied Physics and Vinton Hayes Senior Research Fellow in a Harvard press release. “We’re presenting a new way of making lenses. Instead of creating phase delays as light propagates through the thickness of the material, you can create an instantaneous phase shift right at the surface of the lens. It’s extremely exciting.”
Outlook
“In the future we can potentially replace all the bulk components in the majority of optical systems with just flat surfaces,” said lead author Francesco Aieta, a visiting graduate student from the Università Politecnica delle Marche in Italy. “It certainly captures the imagination.”
In their paper, the group demonstrates numerous stimulations to show that their designs are applicable to all sorts of high-numerical aperture lenses (like flat microscope objectives).You can read the group’s paper at pubs.acs.org (there is a purchase fee). ■
Story via: phys.org
Advertisement
Learn more about Electronic Products Magazine
