October 7, 2014
CLEMSON — Two Clemson University researchers have developed a new technology that could enable gadgets ranging from computers to cell phones to run faster by transmitting information with light instead of electrical current.
In their recent breakthrough, Ramakrishna Podila and Apparao Rao have overcome one of the biggest challenges in creating affordable light-based gadgets. They said they discovered an all-carbon based optical diode that transmits light in one direction.
It’s a critical advance because diodes are the basic building blocks for all gadgets.
With optical diodes, light-based gadgets would be able to more quickly perform the logic operations that make it possible to do all the things that make devices useful, whether it’s telling time or updating a Facebook status.
“This could open doors to the next generation of high-speed gadgets,” said Podila, an assistant research professor of physics.
Information in electronics is typically conveyed by transmitting electrons over tiny distances through copper wires laid on top of silicon chips. The idea of using light in computing has been around for decades, but developing the logic components that are affordable has been a challenge.
One of the biggest hurdles has been figuring out how to transmit light in one direction, while prohibiting light from the other direction, said Rao who is the R. A. Bowen professor of physics at Clemson.
“It sounds easy, but it’s scientifically very difficult,” he said.
Podila and Rao are advancing the technology with graphene, a pure carbon sheet that is remarkably strong even though it is only an atom thick.
The graphene sheet is placed on fullerene film, which is also made of carbon.
“The graphene-fullerene sandwich structure acquires an unusual optical property–it turns into a one-way street for light,” Podila said.
Light can pass through the sandwich structure only when it comes from the graphene side. Light cannot be transmitted when comes from the fullerene side.
“The graphene-fullerene sandwich structure is key for allowing one-way transmission of light,” Rao said “Our technology creates optical diodes in an easy and scalable fashion, and that leads to affordability.”
The team did its work at the Clemson Nanomaterials Center in collaboration with the Raman Research Institute and the Sri Sathya Sai Institute for Higher Learning, India.
Their findings were published in a Nano Letters article (Nano Letters, 13, 5771) with Podila serving as a corresponding author.
“Ours is an extremely simple device,” Podila said. “It is also compact and has the potential for large bandwidth, which makes it cost-effective for large-scale integration in photonic circuits.”
The next step in the research is to modify graphene with various substances known as dopants, Rao said.
“We’ll try doping graphene with nitrogen, or maybe boron,” he said. “We’ll try different elements that are in the neighborhood of carbon in the periodic table and see how to improve the device’s performance.”
It will likely take another phase of research and 10 or more years to make the technology widely available in off-the-shelf products, Rao said.
“We’re looking for industry partners to take this research to the next level,” he said.
Mark Leising, chair of Clemson’s Department of Physics and Astronomy, said the work that Podila, Rao and their team are doing is on the cutting edge of nanotechnology.
“Their research could improve the speed and security of data processing, and ease Internet traffic,” Leising said.
“It is heartening to see three international teams come together under Clemson’s lead to make this discovery. It’s happening right here at Clemson’s Physics and Astronomy Department and it could have meaningful, tangible effects around the globe.”
