Terahertz Breakthrough Could Increase Short-range Wireless Speeds

Modern technology uses many frequencies of electromagnetic radiation for communication, including radio waves, TV signals, microwaves and visible light. Now, a University of Utah study shows how far-infrared light - the last unexploited part of the electromagnetic spectrum - could be harnessed to build much faster short range wireless communications.

"We found a way to manipulate a form of infrared radiation that is not now used for communications so that, in the future, it may be possible to use it for high-speed, short-range communication between computers and other devices," says Ajay Nahata, an associate professor of electrical and computer engineering.

The new study was conducted by Nahata and principal author Z. Valy Vardeny, a distinguished professor of physics at the University of Utah, along with Tatsunosuke Matsui, a postdoctoral researcher in physics, and Amit Agrawal, a doctoral student in electrical and computer engineering.

To visualize their discovery, imagine shining a flashlight through a kitchen colander, and that holes make up 20 percent of the colander's surface. Only 20 percent of the light will pass through the colander. But when the Utah researchers shined far-infrared radiation through holes punched in a thin steel foil or film, almost all of the radiation passed through the film if the holes were arranged in semi-regular patterns known as "quasicrystal" or "quasicrystal approximates."

Until now, such efficient transmission of far-infrared light was achieved only when crystal patterns were used, but unwanted frequencies also were transmitted. In the new study, the researchers could select the wavelength of far-infrared light transmitted through the holes and, by tilting the films, they could switch the transmission on and off.

That shows high-frequency terahertz signals can be switched on and off to carry data in the digital code of ones and zeroes, and that it someday may be possible to build superfast switches to carry terahertz data at terahertz speeds. That is 1,000 times faster than gigahertz fiber optic lines that carry data as near-infrared and visible light, and 10,000 times faster than microwaves that carry cordless and cell phone conversations.

Talking with Terahertz: An Unexploited Part of the Spectrum

The spectrum of electromagnetic radiation ranges from short to long wavelengths (or from high to low frequency): gamma rays, X-rays, ultraviolet rays, visible light (violet, blue, green, yellow, orange and red), infrared rays (including radiant heat), microwaves, FM radio waves, television, short wave and AM radio.

Near-infrared radiation and some visible light now are used for fiber optic phone and data lines. But terahertz or far-infrared radiation - on the spectrum between microwaves and mid-infrared radiation - is not now used for communication.

"Terahertz is a new region of the spectrum for communications" because the rest of the spectrum is crowded with communication and broadcasting signals, says Nahata.

Vardeny adds: "Industry is starving for more electromagnetic frequencies," yet terahertz frequencies are unexplored. They are too high for electronics and there are technical obstacles in generating, manipulating and detecting terahertz radiation.

For electromagnetic radiation to transmit data, the signal must be turned on and off to rapidly create the binary code of ones and zeroes. Modern optical and electronic switches cannot do that fast enough to handle signals with terahertz frequencies (1,000 billion waves per second), but can handle gigahertz signals (1 billion waves per second).

No one has built terahertz switches, but Nahata says the new study shows it is possible to use terahertz radiation to carry data and thus may be possible to create terahertz-speed switches for superfast wireless communication over short distances, such as between a cellular phone and headsets, a wireless mouse and a computer, and a PDA (personal digital assistant) and a computer."

Posted to the site on 17th April 2007