Standoff sensing system identifies materials using dual-laser technique

Standoff sensing system identifies materials using dual-laser technique

Identifying chemicals from a distance could take a step forward with the introduction of a two-laser system being developed at the Department of Energy’s Oak Ridge National Laboratory.

In a paper published in the Journal of Physics D: Applied Physics , Dr. Ali Passian and colleagues present a technique that uses a quantum cascade laser to “pump,” or strike, a target, and another laser to monitor the material’s response as a result of temperature-induced changes. “With two lasers, one serves as the pump and the other is the probe,” said 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.”

An infrared pump laser scans a region of interest of the sample and an accompanying probe laser reads out the absorption spectrum of the constituent molecules.

While this approach is similar to radar and lidar sensing techniques in that it uses a return signal to carry information of the molecules to be detected, it differs in a number of ways. It uses photothermal spectroscopy configuration, where the pump and probe beams are nearly parallel, and probe beam reflectometry as the return signal, which minimizes the need for wavelength-dependent expensive infrared components.

This work represents a proof of principle success that Passian and co-author Dr. Rubye Farahi said could lead to advances in standoff detectors with potential applications in quality control, forensics, airport security, medicine and the military. In their paper, the researchers also noted that measurements obtained using their technique may set the stage for hyperspectral imaging – providing high-resolution chemical as well as topographical information.

For more information, see www.ornl.gov/info/press_releases/newsroom.cfm.

Jim Harrison