Making Unique Observations in a Very Cluttered World

Monday, 8 September 2014

New Terahertz Night Vision Can See Through Walls and Skin -

New Terahertz Night Vision Can See Through Walls and Skin - 

In the unfiltered world there are no secrets. A wall or cloak blocks observation only by virtue of the limitations of vision, whether it's those of the naked human eye or mechanical seeing devices designed around the parameters of a naked eye. If somehow humans could see light waves at all frequencies (and make sense of it), we could see everything.

We've developed an impressive array of tools with which it's become possible to view the world at different frequencies of light, whether that involves the X-ray wavelengths used in radiography or the millimeter wave scanners (the sort that see through clothing) used now in many airports. While humans evolved to see a certain range of wavelengths for very good reasons—that's where most of the useful information about our physical, terrestrial world can be found—technology has made much more available to us.

As impressive and creepy as a millimeter wave scanner may seem, it's still just scratching the surface. Above these extremely high frequencies is another realm: terahertz radiation. Known also as submillimeter radiation or T-rays, it's possible to probe the invisible world even deeper, going beneath not just clothing but skin, plastics, cardboard, and other opaque materials. Getting at these waves has historically been prohibitively challenging in the engineering sense, but a team of researchers based at the University of Maryland claims to have solved one of the fundamental problems with T-ray detection: temperature.

The UMD team's advance is described in today's edition of Nature Photonics. The problem, more specifically, is that T-ray detectors have needed to be kept at extremely cold temperatures to be used efficiently, as far down as -452 degrees Fahrenheit. Obviously, this makes the technology mostly impractical in its current form, and the result is what's known as the "terahertz gap," a region of the electromagnetic spectrum between microwaves and infrared light waves that lies mostly outside of our technological capabilities. Thus, T-rays are usually measured via proxies.

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