Those in the business of bomb detection have found themselves with some unlikely allies recently. First it was worms that could sniff out explosives, then plants, then sensors using bee venom, and even graphene foam. Now, scientists are using lasers to ferret out the bad guys. Researchers at the Vienna University of Technology have developed a system that could potentially detect the what’s inside a container from over a hundred meters away using lasers.
The sensor works by pointing a laser beam at the sample. When the high energy laser light hits the potential bomb, it excites some of the photons that whatever is inside is made of. When those photons get excited, they emit their own light, which the sensor can read and work backwards from to figure out just what it’s looking at.
The technical term for this technique is Raman-spectroscopy, and until recently it only really worked over short distances. As the laser gets further and further away, it excites less and less photons in its target, which makes the signals weaker. Now, with these highly sensitive sensors, even from just a few excited photons, researchers can figure out just what’s inside a container.
But the really important thing that this new laser technique allows isn’t just seeing bombs from far away – it’s seeing them through the containers they might be in. The wall will scatter the laser beam, taking most of the light away. But a very small portion of the light will penetrate the container, and that small portion will excite what’s inside through the Raman scattering process. When the sensors pick up the scattering – the hard part is to figure out what is coming from the container and what is coming from the contents inside.
To do that, the researchers thought about how the light would move through the container. When the laser beam hits the wall it is extremely concentrated. So the light that comes back only comes from a very small region. But the little bit of light that makes it through the wall is much more diffuse – and thus the scattering it causes spreads to a much larger area.
The project, understandably, attracted attention from all kinds of groups interested in security, from the Spanish Guardia Civil, the Austrian Military and several private companies. But the researchers don’t limit the technology to simply foiling the bad guys. According to the university’s press release, they see it as applicable any time access to your research subject is hard to come by, from glaciers to Mars.
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Photo Credit: Vienna University of Technology