Key Advancements from the SILMARILS Program in Chemical Sensing and Hyperspectral Imaging

eThe Intelligence Advanced Research Projects Activity (IARPA) SILMARILS program aims to develop a portable system for real-time standoff detection and identification of trace chemical residues on surfaces using active infrared spectroscopy at a 30-50 meter range. Program goals include compact size, rapid scan rate, high chemical sensitivity and specificity across a broad range of target classes, effective operation in a real-world environment including background clutter, uncontrolled substrates, and temperature, humidity and background light variations, and a system that is Class 1M eye safe with a visually unobservable illumination beam. Towards these goals, a number of advances have been demonstrated in infrared illumination sources and novel spectroscopic approaches that are both enablers for the program and have wider utility to the next-generation spectroscopic community. This paper describes three key program developments from both a technical capability and a future use perspective: 1) high-sensitivity QCL-based hyperspectral imaging that has demonstrated the ability to detect nanogram quantities of target chemicals as well as identify targets at >25m standoff; 2) an extremely broadband (1.5 - 11.5 micron) supercontinuum laser source utilizing a novel cascade of three nonlinear optical fibers coupled to a high-speed rotating-prism Fourier Transform Infrared (FTIR) spectrometer; and 3) a compact, tri-band (Short Wave Infrared (SWIR)/Mid-Wave Infrared (MWIR)/Long Wave Infrared (LWIR) hyperspectral imaging (HSI) sensor employing a spatial interferometric element mounted inside the camera Dewar with a final package size no larger than a conventional panchromatic infrared camera.