Volume 12, Number 1, 2003
A major breakthrough in terahertz nanotechnology could have practical applications in medical imaging, hazardous materials detection and even rescue operations, researchers in the College of Engineering say.
The research team has discovered a way to harness the power of the terahertz frequencies in a palm-sized device using a semiconductor nanostructure, according to James Kolodzey, professor of electrical and computer engineering.
Terahertz, which Kolodzey calls the "final frontier" in the study of electromagnetic waves, lies between microwaves and infrared light in the frequency spectrum. It is 1,000 times higher in frequency than microwaves, which are used in cell phones and ovens, and it is 100-1,000 times lower than visible light.
The key feature of the new device is its size, Kolodzey says.
"This may revolutionize terahertz technology by making it accessible," he says. "The device is the size of a cell phone, perhaps with a side pack for cooling. It can be portable. Previous terahertz systems were definitely not portable."
Not much is known about the terahertz frequencies, he says, and the group's research is both in basic science and in practical applications.
It is known that the frequencies are strongly absorbed by the atmosphere, which makes terahertz a poor medium for long-distance communication through the air, which is how the microwave frequencies are used. However, Kolodzey says, terahertz is of great value at closer ranges.
For instance, it can be used to detect such chemical compounds as pollutants, he says.
Also, it is sensitive to molecules and, to the researchers' surprise, can pass through solid materials and so can be used in imaging and scanning. In that way, it is similar to X-rays, except that it is not believed to be at all harmful to humans, Kolodzey says.
The ability to scan through solid materials is a new terahertz operating principle that has not been explored, he says. To date, the UD researchers have scanned a paper clip through a silicon wafer and have looked at the interior of an egg by scanning through the shell.
Kolodzey says he is excited about the potential uses for the new nanotechnology, particularly in the medical field, where it could be used to scan for such diseases as cancer, the cells of which have a vibrant terahertz signature.
"With cancer, early diagnosis is important," Kolodzey says. "This could help identify cancer very quickly, using a hand-held device. If you catch it early, it gives doctors more of an edge. And, this really highlights the cancer."
It also could provide dentists a tool in addition to X-rays and has applications in the field by providing rescuers with a device that could detect victims trapped under tons of rubble. Emergency and environmental personnel might use it to detect hazardous materials at a distance.
All this, Kolodzey notes, might be possible in a hand-held device, rather than a room-sized piece of machinery. "Our goal is to make it usable and affordable," he says.
The devices are based on a silicon germanium semiconductor, Kolodzey says, adding that UD is one of the primary centers in the world for the study of this medium.
The semiconductor is used to select energy bands that relate to terahertz, and filters are added to control the frequency more precisely--"at our will, not nature's," Kolodzey says. A waveguide is used to corral and distribute the signal in the manner of a laser pointer.
Kolodzey presented the research group's findings during the 11th International Symposium on Nanostructures, held June 23-28 in St. Petersburg, Russia. He also has spoken at two recent events sponsored by the Institute of Electrical and Electronics Engineers.
The research is funded by the National Science Foundation, the Defense Advanced Research Projects Agency and the U.S. Air Force.
--Neil Thomas, AS '76