Compact Femtosecond Pulse Approach to Explosives Detection Combining InN-Based Time Domain Terahertz Spectroscopy and Laser-Induced Breakdown Spectroscopy

Report No. ARL-TN-329
Authors: Michael Wraback; Anand Sampath; Dimitra Stratis-Cullum
Date/Pages: August 2008; 18 pages
Abstract: The feasibility of attaining improved explosives detection and identification using complementary InN-based time-domain terahertz spectroscopy (TDTS) and laser-induced breakdown spectroscopy (LIBS) techniques employing 1550-nm femtosecond (fs) pulse technology has been investigated. The use of very low-energy, ultra-short, near-infrared laser pulses for both TDTS and LIBS has been demonstrated. Novel approaches exploiting polarization fields in wurtzite nitride semiconductors such as InN and GaN led to an enhancement of THz generation by more than a factor of 3 relative to more conventional sources fabricated from these materials. These results could lead to improved THz sources at fs fiber laser wavelengths of interest, with further advances in material quality. Threshold LIBS pulse energies used in this investigation are the lowest reported to date, and gated detection is not required, potentially leading to an overall simpler and inexpensive system more amenable to field use. Finally, the use of low pulse energies in these studies currently available from more compact mode-locked fiber laser systems indicates potential for incorporation in field-deployable explosives-detection platforms.
Distribution: Approved for public release
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Last Update / Reviewed: August 1, 2008