Make way for T-Ray

As microprocessor manufacturers shrink their chips ever closer to the atomic level to wring the last bit of performance gains from traditional fabrication techniques, researchers are looking for other novel ways to produce faster computers. Quantum computing? Photonics? Massively multicore? Investigators at the University of Utah, with funding from the National Science Foundation, are investigating another, relatively unknown, option: terahertz radiation computing.

Ajay Nahata, a University of Utah professor of electrical and computer engineering, has led an effort to create waveguides that will be able to carry terahertz frequency signals from one location to another. Nahata's work could eventually be used to construct terahertz-speed microchips.

Chips today operate in gigahertz frequencies, meaning they encode data on electrical pulses generated at least a billion times a second.

The faster the frequency, the more computations can be done per second. Already though, chip manufacturers are finding that above 4 GHz, they run into show-stopping heat and leakage issues.

Terahertz computing could provide clock speeds of anywhere from 300 GHz to 3,000 GHz, which would hasten computations considerably. Creating a waveguide that can contain such wavelengths is a first step in this direction.

'We've engineered a structure into metal film that can transport terahertz radiation from one point to another,' Nahata said.

The trick is that instead of encoding information with electrons, terahertz computing would deploy plasmons, which are electromagnetic waves, or quasi-particles, that are bound between the electrons on a metal and a dielectric, such as air. Such signals are nicknamed T-Rays.

Nahata's waveguide can split signals and bend them around curves. They are made from stainless steel foil sheets with patterns of perforations. For this work, they used four inches of foil that was one inch wide and 625 microns thick. The metal was cut with rectangular holes, 500 microns by 50 microns. Terahertz radiation was fed into the stainless steel waveguides using femtosecond lasers. For this experiment, the researchers chose the wavelengths of about 0.3 THz, or 300 GHz.

Nahata said terahertz computing remains a decade or more away. Although the waveguides can carry signals, more research is needed into building circuitry that can encode, filter, manipulate and process such waves. 'At gigahertz frequencies, people know how to make wires, modulators, switches ' this is why you have a Pentium processor that works. But once you go to terahertz frequencies, we don't know how to do any of this,' Nahata said. 'This is really an unexplored area of the electromagnetic spectrum.'

About the Author

Joab Jackson is the senior technology editor for Government Computer News.

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