A new method of transferring light into acoustic information on microchips, successful in trials for the first time, could improve data center efficiency, according to researchers from the University of Sydney.

With photonic streams, optical information reaches chips at such a high speed that it is hard to process the data fast enough. While on the one hand, using electronics with faster microprocessors would address the issue of speed, on the other hand, more powerful processors tend to be hotter, use more energy and generate interference. Photonic chips provide a solution to this, granted the data can be slowed in order to become exploitable. 

Researchers have demonstrated that optical information can in fact be transferred onto a chip as an acoustic hypersound wave, a buffer of sorts, slowing to the point where it can be read and processed before being turned back into optical data and relayed to its destination.

University of Sydney doctoral candidate Mr Merklein said: “Building an acoustic buffer inside a chip improves our ability to control information by several orders of magnitude.”

Multiple wavelengths 

Graphic rendering of the "hybrid microchip"
Graphic rendering of the ‘hybrid microchip’ – Youtube/The University of Sydney

The process is as follows: An optical data pulse enters the chip, where it is “depleted” by a write pulse and stored as an acoustic phonon, or sound wave. Then, another write pulse retrieves the acoustic phonon, breaks it down and converts it back into an optical pulse. 

Compared with existing photonic chips, the photon-phonon exchange increased the storage time by approximately 10 nanoseconds.

The study reads: “the opto-acoustic interaction strength is increased by several orders of magnitude by using carefully designed waveguides that guide optical as well as acoustic waves […]”

“The acoustic phonons travel in the waveguide at a velocity that is five orders of magnitude slower than in the optical domain and do not suffer from effects of optical dispersion and other detrimental optical non-linearities during the delay process. Transferring the signal back to the optical domain leads to a delay of the optical signal by approximately the time the signal was encoded as acoustic wave.”

Dr Birgit Stiller, research fellow at the University of Sydney and supervisor of the project, said: “Our system is not limited to a narrow bandwidth. So unlike previous systems this allows us to store and retrieve information at multiple wavelengths simultaneously, vastly increasing the efficiency of the device.”

The chip, of which a prototype was built at the Australian National University’s Laser Physics Centre, is being developed for telecommunications, fiber networks and cloud computing data centers, as these are most vulnerable to overheating, excessive energy consumption and electromagnetic interference.