Although current lens technology has advanced considerably over the years, creating thin, compact lenses is still difficult. It is for this reason that cameras and telescopes utilize curved lenses stacked upon one another and the highest products are so big and long.
Now, researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences have created the first flat lens that works with high efficiency in the entire visible spectrum of light, from red to blue.
The unique lens, which could be the optical revolution needed to advance the field, can resolve nanoscale features with distances between them that are smaller than the wavelength of light.
"This technology is potentially revolutionary because it works in the visible spectrum, which means it has the capacity to replace lenses in all kinds of devices, from microscopes to camera, to displays and cell phones," said Federico Capasso of Harvard and senior author of the study. "In the near future, metalenses will be manufactured on a large scale at a small fraction of the cost of conventional lenses, using the foundries that mass produce microprocessors and memory chips."
Previously, using a single flat lenses to correct for chromatic spread over the visible spectrum of light was impossible to do in an efficient manner, making the integration of flat lenses into the field of optics unlikely. However, the new lens looks to solve this problem.
"The Capasso group's metalens developments enable the integration of broadband imaging systems in a very compact form, allowing for next generations of optical sub-systems addressing effectively stringent weight, size, power and cost issues, such as the ones required for high performance AR/VR wearable displays," said Bernard Kress of Microsoft, who was not part of the research.
The team utilized titanium dioxide in order to create a nanoscale array of nanostructures to form the core of the lens. In addition, the lens possesses a high numerical aperture, meaning that it can effectively focus light onto locations that are smaller than its wavelength.
"The more tightly you can focus light, the smaller your focal spot can be, which potentially enhances the resolution of the image," said Mohammadreza Khorasaninejad, a member of the Capasso lab and first author of the paper.
One of the many potential applications of the new technology is in wearable optics such as virtual reality. Whereas current wearable technologies are typically bulky due to the need for thick lenses stacked upon one another, the new flat lens would eliminate this heaviness.
"This technique reduces weight and volume and shrinks lenses thinner than a sheet of paper," Khorasaninejad said. "Imagine the possibilities for wearable optics, flexible contact lenses or telescopes in space."
The findings were published in the June 3 issue of the journal Science.
