New scanner technology that was shown off first in May of 2009 dubbed "whole-body imaging" scanners had passengers and privacy advocates up in arms over the fact that the scanners were able to see through clothing and show anatomical details of passengers. The scanners are deployed at 40 airports at a cost of about $170,000 each. The scanners blur the face of the person being scanned and only the scanner operator sees the scans.

Researchers at MIT have developed a new technology that may one day allow scanners in airports to tell if the substance inside a medication vial is an illegal drug or an explosive. The technology uses lasers with a frequency in the terahertz spectrum. Lasers operating in the terahertz range are absorbed by different molecules in different amounts allowing scanners using the lasers to tell the difference between chemicals.

The researchers say that accurately determining the chemical composition of objects requires exposing it to different and continuous ranges of terahertz frequencies. MIT professor Qing Hu and colleagues have published a paper in the latest issue of Nature Photonics that outlines a method for tuning terahertz quantum cascade lasers. This is the most promising type of laser to provide the needed terahertz radiation for scanners. Terahertz radiation is also said to be safer for human exposure than x-ray radiation.

Researchers discovered that terahertz lasers could be tuned by bringing a block of another material close to the laser beam. The blocks change the wavelength of the laser light allowing for different frequencies. A metal block was found to shorten the wavelength of the laser and a silicon block lengthened it. Varying the distance of the blocks to the laser also changed the extent of the frequency shift in the laser.

The researchers have designed and are now building chips that use microelectromechanical devices to bring the silicon and metal blocks close to the laser from different directions to vary the wavelengths from short to long. In experiments, the researchers used a mechanical arm to move the blocks.