Flat Lens Can Revolutionize Optical Technology

Even though current lens technology has progressed, it is still difficult to create thin, compact lenses. Cameras and telescopes use curved lenses that are stacked over each other, with the highest products being huge.

For the first time, Harvard John A. Paulson School of Engineering and Applied Sciences researchers have created the first flat lens working efficiently in the 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. "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."

Earlier, it was not easy to use a single flat lens to correct for efficient chromatic spread over the visible spectrum of light. It hence eliminated the integration of flat lenses into the field of optics. It is possible that the new lens can solve the issue.

"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.

By using titanium dioxide to create a nanoscale array of nanostructures, the team can create the core of the lens. It also has a high numerical aperture, with the means of focus light on areas much 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.

The technology may be harnessed in wearable optics, such as virtual reality. Current wearable technologies are heavy owing to the requirement for thick lenses that are stacked upon each other, but the flat lens would be able to avoid the 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.