Volume 12, Number 3, 2004
Dennis Prather's work can be thought of as trying to see "beyond the dark," with the goal of facilitating such activities as flying a military mission through a sandstorm or dense clouds.
The associate professor in the Department of Electrical and Computer Engineering is conducting research on imaging in the millimeter-wave (MMW) part of the spectrum. The wavelength of the energy that we can see with our eyes is quite small, Prather says, and it scatters extensively in turbulent media like fog, sand, mist and clouds.
"What we're doing is trying to find imaging technologies that yield higher wavelengths, which won't be obscured by these types of media," he says.
"The Navy has made an instrument that can see in this range, but it weighs 600 pounds and measures 4 feet by 4 feet by 4 feet. Our charter is to have it weigh less than 4 pounds and fit inside a shoebox. Ultimately, we'd like to be able to place it in an unmanned air vehicle that can fly in murky media so it's not visible itself but has the capability to 'see.'"
Visible light is in the micron scale, and Prather's goal is to improve this to the millimeter scale, which is 1,000 times larger. Such a capability, for example, would allow a helicopter pilot to land in the sand or navigate through thick cloud cover.
"If an MMW system is used, the waves are much larger than the sand particles, which minimizes the extent to which they scatter off the blowing sand and allows one to image directly through it," Prather says. "In addition, MMWs are not absorbed by clouds, as is the case for visible and infrared waves. For these reasons, MMW imaging allows for the ability to see through the natural obscurants that currently plague aerial missions."
To remind him of just what he is trying to achieve, he has one of the Navy's technically capable but vastly oversized instruments sitting in his lab. The agency has awarded Prather and his research team $900,000 per year for three years to build a multimillion-dollar facility for characterization and testing of the future miniature version of the device.
"What we're doing is 'nano-photonics,' or developing optical devices on the nanometer scale," Prather says. "Nano-photonics will enable us to convert millimeter-scale waves into an optical signal that can be seen and interpreted by the human eye. The smaller the device, the more efficient the conversion process is."
Prather's research group has a strong track record for developing optical devices that are as tiny as 10,000 times smaller than a human hair. He initiated the current project last summer and says he still is amassing and fine-tuning the equipment needed to outfit his lab for the work.
"We have a working demo that images at 50 gigahertz," he says, "but our goal is 100."
In addition to the Navy funding to support the research effort, W.L. Gore & Associates has donated more than $500,000 worth of equipment and expressed a willingness to collaborate.
"Their interest lies in the underlying technology, as they make the instrumentation to test the devices," Prather says. "Gore has a major interest in having access to the facility to test their own devices and thereby improve their products. They're coming at it from a slightly different perspective but relying on the same tools."
The project has a high profile, due to its importance to the U.S. Department of Defense, according to Prather.
"The facilities we're putting in don't exist anywhere else in the United States," he says. "Even Gore, which sells the technology, doesn't have this type of infrastructure. When we have it all set up, we'll have a facility that covers an enormous range of capabilities."
But, creating such a capability is not a simple task, Prather says. He describes the process as "kind of like trying to design a pair of eyeglasses for the first time."
Miniaturization brings both enhanced capabilities and increased challenges. "When devices get small, the electromagnetic fields become very intense," Prather says. "We're trying to exploit that intensity."
In addition to the large wooden crate containing the Navy's existing optical analyzer, the lab contains shelf after shelf of computers.
"What we're doing is taking a huge problem, dividing it up into a lot of smaller ones and sending each one to a different computer," Prather says. "Once the information is processed, we'll put it all back together to solve the problem."
Prather joined the College of Engineering faculty in 1997, after earning his doctoral degree in computational electromagnetics from the University of Maryland. He is a member of the nanoelectronics, electromagnetics and photonics research group.
He has received numerous awards, including the College's 2000-01 Outstanding Junior Faculty of Engineering Award, the National Science Foundation Career Award, the Office of Naval Research Young Investigator Award and the W.J. Kastner Technical Achievement Award.
--Diane Kukich, AS '73, '84M