Info Technology World Wide

Part Two, Number 5

Technological applications in the tech area of "T-Rays".

5. T-Rays: With the human eye responsive to only a narrow slice of the electromagnetic spectrum, people have long sought ways to see beyond the limits of visible light. X-rays illuminate the ghostly shadows of bones, ultraviolet light makes certain chemicals shine, and near-infrared radiation provides night vision. Now researchers are working to open a new part of the spectrum: terahertz radiation, or t-rays. Potentially such rays will easily penetrate many common materials without the medical risks of x-rays, and t-rays promise to transform fields like airport security and medical imaging, revealing not only the shape but also the composition of hidden objects, from explosives to cancers.

In the late 1990s, researchers were examining t-rays as an alternative to dental x-rays. The idea was that t-rays, operating in the deep-infrared region just before wavelengths stretch into microwaves, would be able to spot decay without harmful ionizing radiation. In tests, the researchers fired powerful but extremely short pulses of laser light at a semiconductor chip, producing terahertz radiation (so called because it has frequencies of trillions of waves per second). Passing through gaps or different thicknesses of material changes the rays' flight time, so by measuring how long each t-ray took to pass through an extracted tooth and reach a detector, the researchers were able to assemble a 3-D picture of the tooth.

Security seems another natural application of t-rays because different chemical structures absorb them differently; so, t-rays could be used to identify hidden materials. Efforts are being made to develop a scanner that could be used alongside metal detectors. Such a scanner might do things like look at razor blades in coat pockets or plastic explosives in shirt pockets. A library of spectral fingerprints of different materials is being developed now by some researchers.

T-ray systems might also be useful for identifying skin cancers or, with further development, breast cancers. They could show the shape of tumors and help doctors excise diseased tissue more accurately. Because tumors tend to retain more water, they show up very brightly in terahertz images. It's possible that t-rays will provide important gaps between x-ray, MRI, and the naked eyes of physicians.