New laser sensing techno sniffs bombs, pollutants from a distance

Scientists developed a new laser sensing technology that could detect hidden bombs from a distance.

Washington: Scientists have developed a new laser sensing technology that could allow soldiers to detect hidden bombs from a distance.

The Princeton University technology may also help scientists better measure airborne environmental pollutants and greenhouse gasses.

"We are able to send a laser pulse out and get another pulse back from the air itself. The returning beam interacts with the molecules in the air and carries their finger prints," said Richard Miles, the research group leader and co-author on the paper.

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 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.

"In general, when you want to determine if there are contaminants in the air you need to collect a sample of that air and test it. But with remote sensing you don``t need to do that. If there``s a bomb buried on the road ahead of you, you``d like to detect it by sampling the surrounding air, much like bomb-sniffing dogs can do, except from far away. That way you``re out of the blast zone if it explodes," said Miles.

"It``s the same thing with hazardous gases - you don``t want to be there yourself. Greenhouse gases and pollutants are up in the atmosphere, so sampling is difficult," he added.

The findings have been published in the journal Science.