Modulated-laser source induction system for remote detection of infrared emissions of high explosives using laser-induced thermal emission

Nataly J. Galán-Freyle, Leonardo C. Pacheco-Londoño, Amanda M. Figueroa-Navedo, William Ortiz-Rivera, John R. Castro-Suarez, Samuel P. Hernández-Rivera
2020 Optical Engineering: The Journal of SPIE  
In a homeland security setting, the ability to detect explosives at a distance is a top security priority. Consequently, the development of remote, non-contact detection systems continues to represent a path forward. In this vein, a remote detection system for excitation of infrared emissions using a CO 2 laser for generating Laser-Induced Thermal Emission (LITE) is a possible 2 solution. However, a LITE system using a CO 2 laser has certain limitations, such as the requirement of careful
more » ... ent, interference by the CO 2 signal during detection, and the power density loss due to the increase of the laser image at the sample plane with the detection distance. In this study, a remote chopped-laser induction system for LITE detection using a CO 2 laser source coupled to a focusing telescope was built to solve some of these limitations. Samples of fixed surface concentration (500 g/cm 2 ) of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) were used for the remote detection experiments at the distance ranging between 4 and 8 m. This system was capable of thermally exciting and capturing the thermal emissions (TEs) at different times in a cyclic manner by a Fourier Transform Infrared (FTIR) spectrometer coupled to a goldcoated reflection optics telescope (FTIR-GT). This was done using a wheel blocking the capture of TE by the FTIR-GT chopper while heating the sample with the CO 2 laser. As the wheel moved, it blocked the CO 2 laser and allowed the spectroscopic system to capture the TEs of RDX. Different periods (or frequencies) of wheel spin and FTIR-GT integration times were evaluated to find dependence with observation distance of the maximum intensity detection, minimum S/N ratio, CO 2 laser spot size increase, and the induced temperature increment (T).
doi:10.1117/1.oe.59.9.092008 fatcat:nim2f4iysvgqbmfmjp3xsbbhv4