The roadside bombs are considered a big problem due to the death or injury of a huge number of the soldiers and civilians, in Iraq and Afghanistan.
Michigan State University researchers have reached a new development using laser in that regard. The new development can check a large area and detect explosives.
Marcos Dantus, chemistry professor and founder of BioPhotonic Solutions, led the team and has published the results in the current issue of Applied Physics Letters.
Since IEDs can be found in populated areas, the methods to detect these weapons must be nondestructive. They also must be able to distinguish explosives from vast arrays of similar compounds that can be found in urban environments. Dantus’ latest laser can make these distinctions even for quantities as small as a fraction of a billionth of a gram.
The laser beam combines short pulses that kick the molecules and make them vibrate, as well as long pulses that are used to “listen” and identify the different “chords.” The chords include different vibrational frequencies that uniquely identify every molecule, much like a fingerprint. The high-sensitivity laser can work in tandem with cameras and allows users to scan questionable areas from a safe distance.
While the Princeton University engineers have reached earlier this year another solution for remote detecting the explosives.
The technique differs from previous remote laser-sensing methods in that the returning beam is not just a reflection or scattering of the outgoing beam but an entirely new laser beam generated by oxygen atoms whose electrons have been “excited” to high energy levels. This “air laser” is a much more powerful tool than previously existed for remote measurements of trace amounts of chemicals in the air.
Miles collaborated with three other researchers: Arthur Dogariu, the lead author on the paper, and James Michael of Princeton, and Marlan Scully, a professor with joint appointments at Princeton and Texas A&M University. The new laser sensing method uses an ultraviolet laser pulse that is focused on a tiny patch of air, similar to the way a magnifying glass focuses sunlight into a hot spot. Within this hot spot – a cylinder-shaped region just 1 millimeter long – oxygen atoms become “excited” as their electrons get pumped up to high energy levels.
When the pulse ends, the electrons fall back down and emit infrared light. Some of this light travels along the length of the excited cylinder region and, as it does so, it stimulates more electrons to fall, amplifying and organizing the light into a coherent laser beam aimed right back at the original laser.
Researchers plan to use a sensor to receive the returning beam and determine what contaminants it encountered on the way back.