Proceedings Article | 5 May 2012
Proc. SPIE. 8358, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XIII
KEYWORDS: Standoff detection, Explosives detection, LIDAR, Spectroscopy, Luminescence, Photons, Raman spectroscopy, Explosives, Pulsed laser operation, Prototyping
This paper assesses the potential of detecting explosives (RDX, TNT, PETN, HMX, HMTD, Urea Nitrate) from a
distance with a spectroscopic lidar system. For the study, the temporal and spectral resolutions of laser induced
fluorescence lidar prototypes were enhanced. The integrated breadboards used easily available Nd:YAG laser
wavelengths (266 nm, 355 nm, and 532 nm) to remotely detect the Raman signatures induced in traces of explosives
deposited on surfaces. The spectroscopic lidar setup allows for time resolved measurements with high temporal
resolution. Raman spectra are observable, even in the presence of fluorescence. Experiments with low average laser
power (tens of mWs) have shown the unambiguous capability to detect and identify explosives at distances ranging up to
20 m. Thanks to the combination of UV wavelength for higher Raman cross-sections and efficient gated detection the
355 nm prototype yielded the best compromise. Excitation at 266 nm was expected to yield a better Raman response and
was investigated. Less than optimal laser parameters, detection efficiency and strong fluorescence reduced the signal to
noise ratio of the 266 nm signals with respect to those at 355 nm and 532 nm showing the importance of optimizing
system parameters for high sensitivity detection. Besides the description of the prototypes and an early assessment of
their performances, recommendations are also proposed to improve the instrument, leading to an efficient remote sensor
for explosives.
