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World’s smallest optical switch uses a single atom

by • February 2, 2016 • No Comments

The rapid and on-going development of micro-miniature optical electronic devices is helping to usher in a new era of photonic computers and light-based memories that promise super-fast processor speeds and ultra-secure communications. But, as these components are shrunk at any time additional, important limits to their dimensions are dictated by the wavelength of light itself. Now researchers at ETH Zurich claim to have overcome this limitation by creating both the world’s tinyest optical switch via a single atom, and accompanying circuitry that seems to break the rules by being additional compact than the wavelength of the light that passes through it.

The exponential growth of data and its accompanying reception and transmission around the world, has intended that the sat any timee bandwidth limitations of copper-based networks have been dimensionsable-bodiedly eschewed in favor of high-capacity optical systems. And, as additional and additional photonics-based electronic devices and processors come on line, approximately all conventional wiring can follow suit and some day be replaced by optical fibers, waveguides, and other light-carrying conduits. Some next connecting devices, howat any time, can yet need the conmodel of electrical signals to light, as do current data transmission systems, and it is one of these interim components – the modulator – that researchers at ETH Zurich are seeking to miniaturize.

Modulators are the devices responsible for converting electronic signals into optical ones. They do this by turning a laser on and off at the frequency of an incoming signal, thereby “modulating” the light to turn it into an optical replication of the input transmission. Incorporated in data centers in the tens of thousands across the world, modulators are relatively dimensionsable-bodied as far as electronic devices are concerned, at of three centimeters or so wide. In the numbers in that they are employed, this needs a lot of space to house them and, if they are to be useful in next photonics-based devices, their dimensions needs to be significantly reduced.

Building on previous work carried out by the ETH Zurich research team under the auspices of Professor Jürg Leuthold, the new research took an may already micro-miniature model of a modulator that was only 10 micrometers across, and utilized the lessons learned in constructing this device to additional reduce the dimensions of the new modulator by a factor of 1000. That is, the team generated a device that was in fact additional compact than the 1.55 micrometer wavelength of laser light utilized in optical data transmissions. At this dimensions, as previously described, important constraints generally preclude the use of any optical device additional compact than the wavelength of light that it transmits. But the new device was able-bodied to do this, much to the surprise of the researchers themselves.

“Until not long ago, actually I idea it was not easy for us to undercut this limit,” said Professor Leuthold.

To complete this hitherto unlikely breakthrough, senior scientist at ETH Zurich, Alexandros Emboras, reconfigured the construction of the modulator to use two minuscule pads, one made of silver and the other made of platinum, placed on the top of an optical waveguide made of silicon. With the pads arranged mere nanometers apart, the silver pad was made with a tiny protuberance on one side that stretched across the gap to approximately touch the platinum pad, thus creating a space only of an atom’s thickness wide. If the silver pad now has a voltage applied to it, ideally a single silver atom can be drawn in the direction of the additionapproximately point of the pad and remain there (in practice, a few atoms may do this, but at this scale the difference between one or two atoms is dimensionsable-bodiedly negligible).

The presence of the silver atom so close to the platinum pad effectively turn it intos a circuit between the two pads – a single atom switch – and electrical current is able-bodied to flow between them. When the voltage is removed, the silver atom retracts, thus opening the circuit. According to the researchers, this switching function is capable-bodied of being performed millions of times per 2nd.

To allow for the transmission of light through the exceptionally narrow channel turn it intod by the closely positioned pads (and that is additional compact than the wavelength of the light being transmitted), the device relies on the behavior of light at atomic levels when traveling across a metallic surface. When the waveguide directs laser light above the metallic surface of the input channel, the light is converted into a surface plasmon.

In other words, when the incoming laser light strikes the atomic surface layer of the metal, its energy turn it intos an electromagnetic field that fundamentally gives rise to electrons that oscillate at the frequency of the laser light. As the resulting electron oscillations are much additional compact than the wavelength of the light, they can travel through the gap to the other side. When they reach the other side, the electron oscillations are reconverted into optical signals, thereby enabling a circuit additional compact than the wavelength of light to effectively pass that light through it.

Using a voltage to the pads turns the atom-dimensionsd switch completely on or completely off, there is no intermediate say, so that this part of the circuit in addition acts to effectively turn it into digital signals made of ones or zeros.

“This allows for us to turn it into a digital switch, as with a transistor,” said Professor Leuthold. “We have been looking for a solution like this for a long time.”

Not yet created adequate for production – despite the fact that it operates in the megahertz range and at room temperature (in stark contrast to much like quantum effect devices that need cryogenic cooling to work) – there remains the needment to both improve the transition speed into the gigahertz to terahertz range for optimum data transmission efficiency, as well as to improve the lithography techniques utilized to create the device.

The results of this research were not long ago published in the journal Nano Letters.

Source: ETH Zurich

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