ETH Zurich

Physicists Just Built the World's Smallest Optical Switch - Based on a Single Atom

Be afraid, electrons.

5 FEB 2016

As our need for more data and faster transmissions grows, existing network infrastructure is being put under more strain than ever before. As a result, scientists are working hard to miniaturise these systems and switch from current electron-based computers to super-fast optics-based communications, where data is quite literally sent at the speed of light.

Now scientists working at ETH Zurich in Switzerland have made crucial progress in the design of a modulator - the device that converts electronic signals into optical ones. These devices are currently around 3 cm wide, which means when you have a data centre full of them, they take up a substantial amount of room. But this new modulator is based on an optical switch that uses just one atom.


As Gizmag's Colin Jeffrey reports, that's a level of miniaturisation that's surprised even the scientists themselves - it essentially allows light to pass through a gap that's smaller than the wavelength of light itself. A modulator built around this switch could be some 100,000 times smaller than the devices in use today.

Here's how it works: silver and platinum pads are placed on top of an optical waveguide made of silicon with just an atom's gap between them. Once voltage is applied to the silver pad, a single atom is drawn towards its furthermost point, closing up the gap and creating a circuit between the two pads. When voltage is removed, the atom retracts, and thus the modulator can transmit millions of switch signals every second.

But what about the physics-bending light compression? As the light is beamed across the waveguide, it gets converted into surface plasmon, made up of electrons that oscillate at the frequency of the laser light. These electrons can pass through the single atom gap before being reconverted on the other side. By reconfiguring the design of the modulator, the light is effectively squashed to squeeze through the gap.

"Until recently, even I thought it was impossible for us to undercut this limit," said lead researcher, Jürg Leuthold. "This allows us to create a digital switch, as with a transistor. We have been looking for a solution like this for a long time."

Now the team wants to improve the modulator production process so it's suitable for large-scale use and reliable in operation - at the moment, only one out of every six attempts at fabrication is successful. Eventually, though, this single atom modulator could be helping to shift data around the planet faster than ever before.

The research has been published in Nano Letters.

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