Bulky microscopes and telephoto lenses might soon become a thing of the past, thanks to a new technological breakthrough from researchers at the Harvard School of Engineering and Applied Sciences.
The team was able to construct a planar metalens made of an ultra-thin array of tiny waveguides that bend light as it passes through. The lens, made of titanium dioxide, focuses any visible wavelength of light and can resolve structures as small as 400 nanometers. The paper describing this technology is published in Science.
“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, senior author of the paper, in a statement. “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.”
Light passing through the metalens is focused by millions of nanostructures. Capasso Lab
To make the lenses easy to produce as well as scalable, the team looked for a material that was readily available in industry and that could still strongly confine light. They selected titanium dioxide, which is an inert non-toxic chemical used in paints and cosmetics.
This is not the only advantage of using a metamaterial. The best optical lenses need to be precisely polished, and even small deviations in the shape of them can drastically reduce their performance. The metalens instead is produced in a single step, which cuts down on the time it takes to produce them.
Scanning electron microscope micrograph of the fabricated metalens. The lens consists of titanium dioxide nanofins on a glass substrate. Scale bar: 2 mm. Capasso Lab
This discovery could lead to a new generation of wearable optics. “Any good imaging system right now is heavy because the thick lenses have to be stacked on top of each other. No one wants to wear a heavy helmet for a couple of hours,” said Mohammadreza Khorasaninejad, lead author of the paper. “This technique reduces weight and volume and shrinks lenses thinner than a sheet of paper. Imagine the possibilities for wearable optics, flexible contact lenses or telescopes in space.”