Laser Gun Could Detect Roadside Bombs

July 07, 2008 --While bombs get more complicated, identifying them is still pretty simple: someone, or increasingly something, has to get close to it.

Soon bomb squads could safely tell if a suspicious package is an explosive, and from up to 100 meters (328 feet) away, using a laser system developed by researchers at Oak Ridge National Laboratory in Tennessee.

"There are a number of ways to look for explosives," said Oak Ridge National Laboratory researcher Larry Senesac. "But its a lot nicer if you don't have to walk up to a bomb to find out what it is."

Eventually the same technology that could save soldiers from roadside bombs could also spare civilians from food poisoning, say the researchers.

The system is based on on a series of quantum cascade, solid state lasers. Each laser sends out a pulse of light in specific infrared frequencies.

When the lasers hit an object coated with residue from explosives, the light scatters. Some of it bounces back and is picked up by quartz crystals, which act like tuning forks, changing the electromagnetic waves into acoustic waves.

By determining which quartz crystals are activated, and running that specific activation signature through a computer with the chemical signatures of known explosive agents, the system can determine which type of explosive was used.

"This is the first device of its kind," said Charles Van Neste, also of Oak Ridge National Laboratory and the lead author on the paper, which appears in Applied Physics Letters 92.

Other laser-based chemical detection systems exist, but they use powerful lasers that work over a mile away and are dangerous to bystanders.

The new system is so sensitive it can even pick up traces of TNT and other explosives floating in the air. In a different setting, the same system could be programmed pick up signatures associated with spoiled food.