Methodology for using active infrared spectroscopy in standoff detection of trace explosives

This manuscript describes a mobile stand-off detection and identification of trace amounts of hazardous materials, specifically explosives. The technique utilizes an array of tunable infrared quantum cascade lasers as an illumination source which spans wavelengths from 6 to 11 μm, operated at eye-safe power levels. This spectral range enables excitation of a wide variety of absorption bands present in analytes of interest. The laser is modulated to produce a 50% duty cycle, square wave pulses, and control the frequency of irradiation. The backscatter and photo-thermal signals from samples are measured via an IR focal plane array, which allows for the observation of spatial, temporal, and thermal surface processes. A discussion of how these signals are collected and processed for use in identification of hazardous materials is presented.