Harvard scientists develop metalens to focus all visible spectrum of light in one point

Source:Xinhua Published: 2018/1/3 14:59:05

Scientists at the Harvard University have successfully developed a ground-breaking single metalens that can focus the entire visible spectrum of light in the same spot and in high resolution.

The related research is published in the latest version of the online journal Nature Nanotechnology.

Unlike traditional optical devices that focus all the visible spectrum of light by using bulky, multiple curved lenses stacked together, the metalenses that have a simple, flat surface use nanostructures to focus all the combined colors of light.

Normally, each wavelength of light moves through materials at different speeds at a different time, which creates image distortions known as chromatic aberrations.

The Harvard researchers used arrays of titanium dioxide nanofins to equally focus wavelengths of light and eliminate chromatic aberration.

They produced units of paired nanofins that controlled the speed of different wavelengths of light simultaneously.

The paired nanofins control the refractive index on the metasurface and are tuned to create different time delays for the light to pass through different fins, so that all wavelengths can reach the focal spot at the same time.

The landmark creation dramatically reduces thickness and design complexity compared to composite standard achromatic lenses.

"Metalenses have advantages over traditional lenses," says Federico Capasso, senior author of the research, who is also a professor of the Harvard John A. Paulson School of Engineering and Applied Sciences.

"Metalenses are thin, easy to fabricate and cost effective," he said.

The researchers are working to scale up the lens to about one centimeter in diameter, which will make it possible to apply the single metalens technology to future commercial possibilities such as virtual and augmented reality, a promising and profitable prospect in future games industry and other industrial sectors.

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