Laser can identify substances, could be military tool

A new laser that can see what substances are made of could help military aircraft identify dangers such as weapons arsenals far below them, U.S. scientists say. The laser system emits a broadband beam of infrared light covering a range of frequencies, the echoes of which can be used to detect the vibrations of the molecules that make up a solid substance and illuminate deep information, said Mohammed Islam, a professor of electrical engineering and computer science and biomedical engineering at the University of Michigan. "For the defense and intelligence communities, this could add a new set of eyes," he said. The infrared laser emits what scientists refer to as the "spectral fingerprinting range" of frequencies that show a substance's makeup based on which wavelengths of light are absorbed and which are reflected, the researchers said. By analyzing the reflected infrared light they can tell the chemical composition of the target, they said. "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 in a university release Tuesday. The laser could give an aircraft flying at high altitudes the capacity to illuminate and record images of a large region. Many chemical sensors currently in use work at close range, the researchers said, but few if any can do the job from a long distance.