Dr. Ali Passian and colleagues of the Department of Energy’s Oak Ridge National Laboratory (ORNL) have been working on a two-laser system for the identification of chemicals and biological agents from a distance.
Published recently in the Journal of Physics D: Applied Physics, the researchers introduce a technique that uses a quantum cascade laser to “pump,” or strike, a target, and another laser to observe the material’s response as a product of temperature-induced changes. This information permits the rapid identification of chemicals and biological agents.
“With two lasers, one serves as the pump and the other is the probe,” said Dr. Passian, a member of ORNL’s Measurement Science and Systems Engineering Division. “The novel aspect to our approach is that the second laser extracts information and allows us to do this without resorting to a weak return signal. Similar to radar and lidar sensing techniques, this technique uses a return signal to carry information of the molecules to be detected, yet differs in a number of ways.
“First is the use of photothermal spectroscopy configuration where the pump and probe beams are nearly parallel,” Passian said. “We use probe beam reflectometry as the return signal in standoff applications, thereby minimizing the need for wavelength-dependent expensive infrared components such as cameras, telescopes and detectors.”
Dr. Passian and co-author Dr. Rubye Farahi of the ORNL – Nanoscale Science and Devices group said this proof of principal success could lead to advances in standoff detectors with potential applications in hyperspectral imaging, quality control, forensics, airport security, medicine and the military.