June 25, 2013
New Scanning Laser Can Tell What An Object Is Made Of
Brett Smith for redOrbit.com - Your Universe Online
Using commercially-available telecommunications technology, engineers from the University of Michigan have developed a laser capable of detecting a substance’s composition from high up in the Earth’s atmosphere, according to a new report in the journal Optics Letters.
"For the defense and intelligence communities, this could add a new set of eyes," said report co-author Mohammed Islam, an electrical engineering at the University of Michigan.
Most lasers emit of one wavelength, or color, of light. The new system, however, emits a broadband beam of infrared energy that has columns of light across a spectrum of wavelengths. The beam is in the infrared region, making it invisible to human eyes.
The engineers said infrared light contains the "spectral fingerprinting range," or frequencies that represent the vibrations of the molecules within a solid substance. The so-called spectral fingerprint is determined by which wavelengths of light are absorbed or reflected, since various substances interact with infrared light differently.
"A grey structure looks grey in visible light, but in the infrared, you can see not only the shape, but also what's inside it," Islam said.
The US military already uses spectral fingerprinting to identify potential targets, but the technology currently in use needs sunlight, complicating matters on a cloudy day or at night. Similar chemical sensors are also in use, but these tend to only work at close range.
To develop the new system, the Michigan researchers had to develop a relatively powerful broadband laser, Islam explained. The team began with a 5-watt prototype, moved up to a 25.7-watt version, and is currently working with a 50-watt prototype, which is slated to be field tested later this year.
Last year, the team traveled to Wright Patterson Air Force Base in Ohio to field test their smallest prototype. Observers from the Air Force Research Labs, the University of Michigan, and several other groups were there as the engineers placed the experimental laser in a 12-story tower and directed it to targets about one mile away on a runway. The team used scientific cameras and other instruments to record the laser beam quality and signal level.
The engineers say the technology could give an airborne military aircraft the capacity to illuminate an area with the same magnitude as natural sunlight and then scan the target region.
Islam says that the new technology could also improve TSA airport screening technologies that many feel are intrusive or degrading.
"Those are imaging devices looking for bumps where there shouldn't be bumps," Islam said. "They're looking for shapes that are odd or different. But they can't see the chemicals in the shapes. That's why you have to take your shoes off. But our laser can detect the chemical composition."
The engineers said they were able to build the device by applying a patented technique to commercially available telecom fiber optic technology. They added that their laser takes advantage of the fiber’s natural physics to create the light burst.