New colourful metalens opens up possibilities for AR and VR

2 Jan 2018

Image: Mark Agnor/Shutterstock

By harnessing all the colours of the rainbow on to a single lens, a team of researchers could create whole new avenues of discovery for AR and VR.

For years now, scientists working in the field of optics have been working to replace the bulky, curved lens with something known as a metalens: a flat surface that uses nanostructures to focus light.

What has held the technology back, however, is the limited spectrum of light that it can focus well – but that is set to change following a recent breakthrough from the Harvard John A Paulson School of Engineering and Applied Sciences (SEAS).

In a paper published to Nature Nanotechnology, a team of researchers revealed that it developed the first single lens that can focus the entire visible spectrum of light – including white light – in the same spot and in high resolution.

Until now, this achievement has only been done using standard curved lenses stacked on top of one another.

No more stacking

What makes focusing the entire spectrum of light so challenging is that each wavelength moves through materials at different speeds.

So, for example, red wavelengths will move through glass faster than blue, meaning that the two colours reach the same location at different speeds, resulting in image distortions.

That is why devices up until now have had to stack up lenses to accommodate for this, resulting in extra weight.

Dramatically reduces thickness of lens

The single metalens developed by the Harvard team uses arrays of titanium dioxide nanofins to equally focus wavelengths of light and eliminate distortion, referred to as chromatic aberration.

With units of paired nanofins, the metalens is able to control the speed of different wavelengths of light simultaneously.

“By combining two nanofins into one element, we can tune the speed of light in the nanostructured material, to ensure that all wavelengths in the visible are focused in the same spot, using a single metalens,” said Wei Ting Chen, first author on the paper.

“This dramatically reduces thickness and design complexity compared to composite standard achromatic lenses.”

The next step for the team is to scale up the thickness of the lens to a diameter of 1cm, which would open it up to a range of new, powerful applications, including augmented reality and virtual reality.

Speaking with last month, Leap Motion CEO Michael Buckwald said that the immersive technology will have its ‘iPhone moment’ soon, whereby it will become commonplace.

Colm Gorey was a senior journalist with Silicon Republic