The speed of pulses of light are not as fixed you might think — and that’s good news for your weekend movie streaming.
New research published last week in Nature Communications builds on a previous proof of concept that showed it was possible to speed up, slow down and even direct a pulse of light to travel backward. Now the lab of Optics Professor Ayman Abouraddy, Ph.D., is showing the application: faster and more efficient communication over optical fibers.
“It’s been a series of eureka moments,” said Abouraddy, who co-authored the paper with CREOL graduate student Murat Yessenov, post-doctorate researcher Basanta Bhaduri, Ph.D. and Professor Peter Delfyett, Ph.D.. “When it comes to pulsed beams of light, space and time have always been decoupled, but the moment you start intertwining them all of our expectations and intuitions can be circumvented.”
It works like this: pressing “send” on an email sends an electrical pulse of information that is eventually converted to an optical packet of information. Millions of these pulses are traveling through optical fibers at any given time and that dense traffic can bunch up at the optical switches that serve like a traffic light. At peak times, two pulses might reach the switch simultaneously, causing your packet to be discarded, and a message sent back to your device to resend. That’s why your videos buffer or your music streaming sometimes stalls.
Conventional thinking about lasers and light assumed there was no way to change the speed of pulses, but today’s paper, “Free-space optical delay line using space-time wave packets,” proves that two pulses leaving the same starting line don’t have to arrive simultaneously. The delay allows the switch to avoid choosing which packet to allow; instead, it can push packets through in staggered waves.
Challenging established thinking is a hallmark of Abouraddy’s lab. His work remains within the bounds of Einstein’s theory of special relativity, which states that the speed of light is constant. What he’s controlling instead is the group velocity of colored beams. The groundbreaking work now holds huge potential, but it required accepting the significant risk involved in tackling challenging problems.
“We aim at coming up with something new, whether it’s in art or science,” Abouraddy said. “But there are many more pitfalls in coming up with something unique, and most people would rather follow accepted or conventional ideas. Doing something new like this is exhilarating and scary at the same time.”
“As in any new discovery, doubt and frustration were part of the path to it,” he said. “However, the feeling that the outcome of the work may benefit society compensates for it all and motivates me to work even harder.”
The technical aspects of the discovery excite Delfyett.
“Space-time wave packets produce some very unintuitive and exciting results, and expand our knowledge of how light beams can be created,” said Delfyett. “Most importantly, this new knowledge enables us to consider how these light beams can be applied in computer interconnects and optical communications, and create levels of performance that would not be achievable otherwise.”
Abouraddy received his doctorate in electrical engineering from Boston University and worked as a postdoctoral researcher at the Massachusetts Institute of Technology. He joined UCF in 2008.
Delfyett received his B.E.(E.E.) degree from The City College of New York in 1981, the M.S. degree in EE from The University of Rochester in 1983, the M. Phil and Ph.D. degrees from The Graduate School & University Center of the City University of New York in 1987 and 1988, respectively. He joined UCF in 1993.
Yessenov earned his bachelor degree in physics from Nazabayev University, Kazakhstan, and joined Abouraddy’s group in 2017.