New terahertz laser tech could detect bombs

A team of researchers from MIT and Princeton have built a new system for detecting chemicals used in explosive. The system is based on laser-powered terahertz spectroscopy – the measurement of electromagnetic radiation between the frequencies of microwaves and infrared. The possibility to detect bombs by using radiation has long been realised, but until now terahertz systems were too cumbersome and power-hungry to prove a viable detection mechanism.

This new system solves the problem. It uses a small quantum cascade laser – about the size of a computer microchip – which can detect terahertz signatures in a split second. The device uses the laser to produce a so-called frequency comb – “a spectrum made up of a series of equally spaced frequencies,” UPI reports. With this variety of frequencies, the device can create a unique “terahertz-absorption profile” with a handful of measurements.

One of the issues until now was that cascade lasers must be kept at very low temperature to operate. This required bulky cooling systems that made widespread use prohibitive. Because the new system uses a very small and very low-energy quantum cascade laser, the cooling system required for it is much smaller as well.

“We used to consume 10 watts, but my laser turns on only 1 percent of the time, which significantly reduces the refrigeration constraints,” said Yang Yang, a PhD candidate in electrical engineering and computer science at MIT and one of the lead authors on the paper describing the development. “So we can use compact-sized cooling.”

Still, it will probably be a few years until this breakthrough finds its way to security checkpoints at your local airport. This is a “great first step” towards practical applications, said Princeton’s Gerard Wysocki, but the importance of this development cannot be overstated nonetheless. In the not too far future, it could find real application in bomb detection, as well as help doctors and scientists find traces of materials that they previously could not.