Australian researchers have engineered optical nanowires with a diameter of 68 nanometres - about 1,000 times thinner than a human hair. It's an important step toward developing photonic chips, which could enable a faster and more sustainable Internet.
Credit: Center for Micro-Photonics of the Swinburne University of Technology/CUDOS
SYDNEY: Using an optimised laser nanofabrication technique, Australian researchers have engineered one of the world's smallest nanowires made from an optical material known as chalcogenide glass.
The research, recently published in the journal Nano Letters, represents a step towards faster and more efficient Internet connectivity via 'photonic chips', which exclusively use light to pass data between computers.
While fibre optic cables are used to transport information using photons - packets of light - over long distances, these same photons have proved difficult to sort when it comes time to ensure the right packet gets to the right address.
Currently the photons are converted into an electronic signal, which modern routers must sort before sending off to the correct recipients. This need for conversion means that there is a speed limit hindering the current system.
Creating a router that could sort the packets of light without needing to convert the signal would not only result in a much faster Internet, but a more sustainable one, by reducing the electricity required to run network equipment.
"It's projected that in the next decade [the Internet] will count for half of the world's energy use," said optical physicist Min Gu, director of the Centre for Micro-Photonics at Swinburne University of Technology in Melbourne. "So making it more efficient will make a huge difference to our carbon footprint."
Optical non-linearity needed
In order to reach these ambitions, researchers need to take advantage of a unique optical property of certain materials called non-linearity.
"Optical non-linearity is a key property that is needed for optical switching, similar to the function provided by an electronic transistor," said Elisa Nicoletti, lead author and material scientist at Swinburne University of Technology.
For the researchers involved in this study, the non-linear material of choice is a particular kind of chalcogenide glass. Normal light can pass through the glass without any effect, just like regular window glass.
But if the incoming light is modified to higher intensities, it alters the properties of the glass so that subsequent light behaves differently. This behaviour can be adapted to provide the kind of switching and routing of signals that an ordinary electronic router currently achieves.
Laser etching for thinner wire
But it's not just the unique properties of the glass that contributes to the importance of the discovery. It's the ability to manufacture nanowires out of the glass at a scale never before seen.
The team fine-tuned a method of laser etching that produced smooth wires with a tiny 68 nanometre diameter - 1,000 times thinner than a human hair.
Scientists have previously been able to make nanowires of this size out of polymers, but these materials don't exhibit the same enabling non-linear properties as chalcogenide glass.
"In order to make the chip small, every component needs to be
extremely small," said Nicoletti. "So we always try to push it that bit further to make our nanostructures as tiny as possible."
'Hero' experiment could herald super-fast Internet
It is estimated that the improvements in speed offered by a purely optical network switching system would surpass 1,000 times the current network speeds. But lightning fast delivery of YouTube videos isn't the only thing that may come from the study.
Benjamin Eggleton is a physicist at the University of Sydney, and director of the Centre for Ultrahigh Bandwidth Devices for Optical Systems (CUDOS), an ARC Centre of Excellence. He calls the research a 'hero experiment'.
"This work establishes the feasibility of creating extremely small wires out of an exciting material, and lays the foundation for the creation of two- and three-dimensional structures with high non-linearity," he said.
In the future, the group is looking to modify the chalcogenide glass to create a novel metamaterial - a material that exhibits properties not found in nature.
Coupled with the ability to manipulate the structures into three-dimensional arrays, this could lead to a number of applications such as optical computers, or even cloaking devices.
