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Electro-optical device provides solution to faster computing

04 Dec 2019

Developed by Advanced Nanoscale Engineering research group at the University of Oxford.

What is claimed to be "the first ever integrated nanoscale device that can be programmed with either photons or electrons" has been developed by scientists in Harish Bhaskaran's Advanced Nanoscale Engineering research group at the University of Oxford.

In collaboration with researchers at the universities of Münster and Exeter, the scientists have created an electro-optical device which, they say, "bridges the fields of optical and electronic computing; t his provides an elegant solution to achieving faster and more energy efficient memories and processors."

The group, whose latest work has been published in Science Advances, comment, "Computing at the speed of light has been an enticing but elusive prospect, but with this development it's now in tangible proximity. Using light to encode as well as transfer information enables these processes to occur at the ultimate speed limit — that of light."

While as of recently, using light for certain processes has been experimentally demonstrated, a compact device to interface with the electronic architecture of traditional computers has been lacking. The incompatibility of electrical and light-based computing fundamentally stems from the different interaction volumes that electrons and photons operate in. Electrical chips need to be small to operate efficiently, whereas optical chips need to be large, as the wavelength of light is larger than that of electrons.

Light compression

To overcome this problem, the scientists came up with a solution to confine light into nanoscopic dimensions. They created a design that allows them to compress light into a nano-sized volume through what is known as surface plasmon polariton. The dramatic size reduction in conjunction with the significantly increased energy density is what has allowed them to bridge the apparent incompatibility of photons and electrons for data storage and computation.

More specifically, it was shown that by sending either electrical or optical signals, the state of a photo- and electro-sensitive material was transformed between two different states of molecular order.

Furthermore, the state of this phase-transforming material was read out by either light or electronics thereby making the device the first electro-optical nanoscale memory cell with non-volatile characteristics. "This is a very promising path forward in computation and especially in fields where high processing efficiency is needed," said Nikolaos Farmakidis, graduate student and co-first author.

Co-author Nathan Youngblood cemented, "This naturally includes artificial intelligence applications where in many occasions the needs for high-performance, low-power computing far exceeds our current capabilities. It is believed that interfacing light-based photonic computing with its electrical counterpart is the key to the next chapter in CMOS technologies."

'A plethora of novel devices and platforms'

The Science Advances paper's key conclusions are as follow:

"We have demonstrated a nonvolatile nanoscale electro-optic device that enables both electrical and optical programming and readout using the synergetic combination of PCMs and nanoplasmonics. This is an unprecedented demonstration of an integrated, reversible, and nonvolatile phase-change memory cell that fully bridges the gap between electro-optic mixed-mode operations.

"This was enabled by using a plasmonic design that simultaneously reduces the footprint of the device, enhances light-matter interaction, and reduces the separation between electrical contacts, creating a compact and highly sensitive device. Our approach also enables a direct comparison of both optical and electrical read and write operations in a single device, demonstrating the relative merits and limitations of both.

"The nonvolatile nature of our platform provides an exciting outlook in the development of switchable and reconfigurable metadevices by means of optical or electrical stimuli, enabling novel approaches to switchable metamaterial-based optical components."

The developers concluded, "We anticipate that a plethora of novel devices and platforms should arise in the coming years, which will capitalize on the bridge between the electrical and photonic domains [that we have demonstrated]. These devices potentially herald true device-level integration of hybrid optoelectronic computing platforms with in-memory computing and multilevel data storage, which is readily applicable to this work."

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