Terahertz spectrum scanning is potentially ideal for finding bombs due to the sheer range of materials it can detect, but it's not exactly practical for luggage checks when you need both a suitcase-sized machine and up to half an hour to conduct a scan. MIT researchers have a better way, though: they've developed a quantum cascade laser system that should make terahertz detection a reality. Since the laser's single, tiny frequency comb only consumes power for very brief periods, you can fit it into a part the size of a chip without a gigantic cooling unit -- perfect for airport scanners. It takes as few as 100 microseconds to identify a substance, too, so you wouldn't have to wait (longer than usual, anyway) while agents scan your bags.
As is often the case with breakthroughs like this, you probably won't see quantum cascade lasers at security gates any time soon. Princeton's Gerard Wysocki describes this as a "great first step" toward terahertz detection rather than the end goal. All the same, it's not hard to see where things are going. The technology is most immediately relevant for security scanners, where spotting an exotic explosive could save lives, but it could also help doctors and scientists find traces of materials that might otherwise go unnoticed.