Teraherz speed circuits
Terahertz speed circuits get closer
* 18:28 16 April 2008 * NewScientist.com news service * Jeff Hecht
This pattern of holes in a steel sheet can steer and process signals carried by terahertz waves with a frequency around 1000 times faster than today's electronics
This pattern of holes in a steel sheet can steer and process signals carried by terahertz waves with a frequency around 1000 times faster than today's electronics
Tools to direct and combine signals carried by terahertz radiation are bringing super-fast data-processing closer, say US researchers. Their new devices are to high-frequency waves what wires are to electricity.
Terahertz frequencies are the only part of the electromagnetic spectrum not used by humans and are now being explored for higher bandwidth wireless communications or security scanners able to look through clothing.
But engineers at the University of Utah, US, led by Ajay Nahata are more interested in using them to process information.
Today's circuits and devices such as computer chips work at gigahertz frequencies, cycling billions of times a second. "We've demonstrated the first step toward making circuits that use terahertz radiation, and ultimately they might work at terahertz speeds," or trillions of cycles a second, says Nahata.
The light in optical fibre has even higher frequencies. But it travels as photons that do not interfere with one another, making signals that are high quality but hard to process. Terahertz waves can ripple through the electrons of a metal surface, making signals that are easier to work with.
Round the bend
The Utah team built and designed the first waveguides that can steer terahertz signals around corners, and even split and combine them.
Waveguides perform the job that pipes or wires do for electromagnetic waves like light or radio. Electric circuits use wires, but electromagnetic circuits need waveguides.
The terahertz waveguides were made by etching out trails of tiny regular rectangular holes 50 by 500 micrometres in size in stainless steel sheets just under a millimetre thick (see image, right). Each trail can guide terahertz waves about 10 cm across the metal surface.
As well as turning terahertz waves around corners, waveguides can split signals into two using Y-shaped junctions and combine them using X-shaped junctions.
New horizons
It is only just becoming possible to handle terahertz waves, because most simple materials simply cannot interact with them usefully.
Terahertz waveguides developed last year at Rutgers University, New Jersey, US, were not able to guide signals in a plane like the Utah ones do.
That is crucial if circuits that process information using terahertz signals are to be made, says Nahata. Until now flat waveguides have only succeeded in guiding terahertz waves in a straight line.
The new waveguides have similar capabilities to those used to process infrared light in fibre-optic communications, says Daniel Mittleman of Rice University, Houston, US. "No such thing had been available for terahertz," he adds. "It's a very nice demonstration."
Wires and optical waveguides that carry and process light and electricity have made today's computing possible, says Mittleman. "We can hope by analogy that this does the same thing for terahertz," he told New Scientist. "It's an enabling technology, but what it will enable us to do is a harder question."
Nahata is working to improve his waveguides to make them carry signals further. He also plans to build the other components needed for functioning circuits to process data-carrying signals.
A paper on the new waveguides will be published in the journal Optics Express later this month.
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