Eye-safe Standoff Chemical Threat Detection Using Deep Ultra-Violet Raman Spectroscopy and LiDAR Imaging

摘要

Foreign and homegrown terrorism, illegal drug manufacture and environmental contamination, have lead to anincreased need for rapid, portable and standoff chemical threat (explosives, narcotics, toxic industrial chemicals, etc.)detection technology. Analytical techniques; like High-Performance Liquid Chromatography (HPLC), GasChromatography-Mass Spectrometry (GC-MS), and Ion-Mobility Spectrometry (IMS), are industry standards due theirunmatched combination of sensitivity and selectivity. However, samples must be handled by and handler and for analysis,putting the user at risk if samples are of a potentially threatening nature. Vibrational spectroscopic techniques are uniquelysuited to this application as they offer chemical identification capabilities as well as the ability to be collected at standoffdistances, as emitted or scattered photons are collected at some distance from the sample.Here we report on chemical threat detection instrumentation methods which employs deep ultra-violet (DUV)Raman spectroscopy and Light Detection And Ranging (LiDAR) imaging. UV Raman spectra were measured using anovel experimental configuration. This configuration allows many of the difficulties associated with UV excitation andhigh-power pulsed laser sources to be mitigated. Large sample areas are imaged into the detection system allowing highpower excitation sources to be used while simultaneously avoiding sample degradation and multi-photon absorptioneffects. Such large detection areas allow large numbers of molecular scatters to be probed even with minimal penetrationdepth. Alignment issues between sample and collection optics are also simplified.