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Laser detects roadside bombs

Michigan State University professor Marcos Dantus works with an associate in his laboratory in the Chemistry building.
Michigan State University professor Marcos Dantus works with an associate in his laboratory in the Chemistry building.Kurt Stepnitz

Lab scientists are pitching a new high-tech laser that is able to detect roadside bombs before they explode, potentially thwarting the deadliest weapon in Iraq and Afghanistan.

Roadside bombs, known as improvised explosive devices or IEDs, account for 60 percent of coalition soldiers' deaths, according to NATO figures. Finding a way to improve on — or at least replace — bomb sniffing dogs is therefore a priority abroad and at home. 

Using lasers to do the dirty work is an ongoing effort. This latest approach combines short and long pulses of light to excite and "listen" to the fingerprint of individual molecules, allowing soldiers to pick out explosives in a crowded urban environment.

"We are using an ultrashort pulse that whenever it gets to the molecule at the target, it gives it a kick in a very, very short timescale," Marcos Dantus, who is leading the research at Michigan State University, explained to me on Monday. "The molecule starts vibrating." 

Dantus likened this vibration to an individual ring tone people might put on their cellphones. The longer laser pulse "listens" to this ring tone, allowing soldiers to know if the target is a bomb. 

The technique is so sensitive, he added, that it can distinguish between molecules that have the same chemical formula but a slight different arrangement of atoms. What's more, a laser no more powerful than the ones used during PowerPoint presentations is required for the technique to work. 

This differs from an approach Princeton University engineers unveiled this March that bounces ultraviolet pulses off chemicals in the air, carrying the fingerprint of the molecules.

"Our approach uses 100 times less energy per pulse, can detect much lower concentrations," Dantus noted in a follow-up email exchange. "Our method was designed for solid targets with approximately one -billionth of a gram of an explosive mixed with other compounds." 

The laser bomb sniffing technology is currently undergoing development in the laboratory. It has been shown to work at distances up to about 40 feet, though should be possible at distances of 330 feet. "Beyond that, we need engineers who know how to handle longer distances," Dantus said.

His team is currently seeking funding to bring the technology from the lab out into the field. If secured, Dantus said, it would take about a year to deploy a system that can function, for example, in a mobile unit. 

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A paper on the laser technology appears in the current issue of Applied Physics Letters and is available here. The research is funded, in part, by the U.S. Department of Homeland Security.

John Roach is a contributing writer for