For the very first time, researchers at the University of Sydney have achieved a dramatic slowing of digital information carried as light waves, by transferring the data into sound waves in an integrated circuit.
The lead researcher on the project, Dr. Birgit Stiller, says the idea of taking advantage of different velocities of light waves and sound waves was a fascinating one, and motivated them to pursue the project.
"Our group has a strong background in light-sound interactions. About 10 years ago, there was a first proof of principle of this approach in optical fiber, and we further explored this by showing the entire information of an optical wave can be transferred to the acoustic domain and back. We furthermore were able to integrate it on a tiny photonic chip designed such that the optical and acoustic waves strongly interact with each other," Dr. Stiller told Sputnik.
Transferring information from the optical to acoustic domain and back again inside a chip is critical for the development of "photonic integrated circuits" — microchips using light instead of electrons to manage data.
Dr Birgit Stiller from CUDOS presenting Postdeadline paper at the OSA photonics and Fiber congress in sydney pic.twitter.com/IYQqqu8dkn
— Benjamin Eggleton (@ProfBenEggleton) September 7, 2016
These chips are being developed for use in telecommunications, optical fiber networks and cloud computing data centers — environments in which devices are susceptible to electromagnetic interference, produce too much heat or use too much energy.
"We hoped to realize the coherent transfer of light to sound and back on a tiny photonic chip, with all the advantages that it brings. That's what we were aiming for and ultimately achieved," Dr. Stiller added.
The information in the University team's chip in acoustic form travels at a velocity five orders of magnitude slower than the optical domain, an effect Dr. Stiller likened to the difference between thunder and lightning. This delay allows for the data to be briefly stored and managed inside the chip for processing, retrieval and further transmission as light waves.
Energy Consumption
Fiber optics and the associated photonic information — data delivered by light — have huge advantages over electronic information. Bandwidth is increased, data travels at the speed of light and there is no heat associated with electronic resistance. Photons, unlike electrons, are also immune to interference from electromagnetic radiation.
There is bound to be strong commercial interest in the group's findings — data centers, such as those offered by Google or Microsoft, currently suffer from high energy consumption coupled with much heat production. The use of photonic chips — bypassing electronics — is one solution to this problem being pursued by large companies such as IBM and Intel.
However, Dr. Stiller's vision is to replace electronic interconnects between different processors and computing machines with photonic "wires" — Dr. Stiller explained light transmission will be used instead of electronic connections.
Light is an excellent carrier of information and useful for taking data over long distances between continents through fibre-optic cables — however, she explains the speed of light can also become a "nuisance" in case of synchronization and therefore an optical solution for a short-term "parking" of memory is needed.
"Our approach is a solution for a light memory that is entirely controlled by light pulses. Therefore, all advantages of the photonics domain are preserved," Dr. Stiller said.
The team's system is not limited to a narrow bandwidth — thus, unlike previous systems, information can be stored and retrieved at multiple wavelengths simultaneously, vastly increasing the efficiency of the device."
The team's work is an important step forward in the field of optical information processing, a concept that fulfils all requirements for current and future generation optical communication systems. However, their approach remains very much still on a research level. Dr. Stiller notes the next step is to engineer the system further, and make it ready for a prototype in the next years.
"As we are interested in fundamental research, we are looking for unexpected results, however we need to try to explain and model theoretically everything that we observe. Therefore, in our publication we try to give a rigorous explanation of our experimental results," she concluded.
