A new instrument able to detect chemical residues from a distance overcomes a number of problems that have plagued laser-based detectors of the past, according to Marissa Morales of Oak Ridge National Laboratory's Measurement Science and Systems Engineering Division. Using a tunable mid-infrared quantum cascade laser and an infrared camera, Morales and colleagues were able to identify as little as 5 micrograms per square centimeter of an explosive residue on a stainless steel surface. The ORNL system avoids safety problems associated with high-power lasers and approaches that require the laser to methodically scan a large area, a slow process. ORNL's technique also avoids problems of interference in the infrared region from background material.
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