Researchers develop new flat optical ‘metalens’

Posted on 7 Jun 2016 by Michael Cruickshank

A group of researchers at Harvard University have developed a new kind of lens which could revolutionize the field of optics.

An electron microscope image of the surface of the metalens. Image courtesy of the Capasso Lab.
An electron microscope image of the surface of the metalens. Image courtesy of the Capasso Lab.

These new optics, called ‘metalenses’ make use of tiny structures to create high quality lenses vastly smaller than current technology.

Existing lenses make use of relatively large, curved pieces of glass which funnel light into a focus point. The basic technology behind this has not evolved much since the 19th century, and to this day, multiple lenses are still needed to correct for errors.

The new metalenses developed at Harvard and outlined in a new paper in ‘Science’, do not have these drawbacks. As the first fully-functional flat (planar) lenses they have the ability to accurately work within the entire visible spectrum of light.

What’s more, these lenses are on a microscopic scale, measuring just two millimeters across.

The researchers behind this technology believe it could see significant use in consumer electronics into the future.

“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 cameras to displays and cell phones,” said Federico Capasso, Robert L. Wallace and Vinton Hayes, the authors of the paper.

Manufactured like a computer chip

The lens itself uses a thin array of tiny waveguides, known as a metasurface, which bends light as it passes through.

This metasurface is the placed on a wafer of titanium dioxide, a material chosen due to its high refractive index and the fact that it already is used in many different industries.

While the structures used within these lenses are indeed tiny, they are on a similar scale to those found on common silicon computer chips.

The Harvard team believes that using similar mass production techniques, the cost of these metalenses could be made easily affordable.

“In the near future, meta-lenses 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,” the team explains.