New Laser Tuning Technique Promises Better Remote Sensing of Chemical Threats

  • Published
  • By Mary Rodriguez, AFRL/RD
  • Directed Energy Directorate
KIRTLAND AIR FORCE BASE, N.M. --  Whether on the battlefield or the city streets of home, early detection of chemical, biological, radiological, nuclear, and/or high-yield explosives (CBRNE) saves lives. AFRL, in collaboration with the University of New Mexico, devised and demonstrated a novel way of continuously changing, or "tuning," the wavelength of light emitted from a semiconductor laser. This new laser tuning technique could improve the capability to detect trace amounts of potentially hazardous chemicals from a distance. AFRL scientists expect this technology to migrate from early laboratory demonstrations to remote sensing applications, as well as other possible uses, in the next several years.
   
Remote sensing requires a laser with high brightness and a very narrow wavelength range of emission, as well as a means of controlling the wavelength during its transmission through suspect chemical clouds and/or pollution. By varying the wavelength, one can trace the absorption signature of the laser light and look for the presence of a specific gaseous entity. Most simple gases, such as carbon dioxide, and complicated gases, including those used as components of lethal chemical weapons, have strong absorption signatures in the midinfrared wavelength range. Lasers meeting the criteria for remote sensing facilitate analysis of these signatures.

The AFRL/academic team devised an innovative application of the distributed feedback grating concept, wherein the teeth of the grating vary slightly, or "chirp," according to their position on the laser. The chirped distributed feedback grating enables continuous tuning of the laser's emission wavelength based on the laser's physical positioning. This new approach promises to replace the more complicated techniques currently in use for tuning laser wavelengths. Further, the novel tuning method paves the way for much-improved remote sensing schemes offering greater range and accuracy in detecting CBRNE threats.