THz RADAR systems provide the ability to enhance optical imagers in a variety of important detection tasks. THz systems have a small enough wavelength to provide image resolution on the order of millimeters, and THz radiation penetrates many materials, such as clothing, wall board, wood, etc., that are opaque to optical and infrared imagers. In addition to their beneficial imaging properties, spectroscopic systems in the THz regime provide the ability to fingerprint molecules based on their absorption features. The team has developed a compact scanning THz radar that will be used to identify materials by considering precision non-imaging THz spectroscopy in the laboratory. The team will also investigate the utility in the environment. The proposed work is aimed at applying high resolution Terahertz spectroscopy techniques to standoff imaging problems. The union of high resolution THz spectroscopy and imaging technology can readily be applied to many important societal needs. For example this technology could be used to quickly inspect mail for chemical or biological agents, look for traces of E-coli in food processing plants, or to check the relative concentration of therapeutic isomers versus non clinical compositions in drugs. The proposed technology also has real potential to help physicians diagnose skin cancer in its earliest stages. On the education front, this proposed effort will involve two graduate students and an undergraduate student, as well as a Masters student.
This was the first year of a 3-year effort to modify an existing radar system that operates between 350 GHz and 1 THz. The existing radar (called HAZAL) creates a 3-dimensional image of a volume within 50 meters of the radar. HAZAL transmits a chirp pulse, then uses a coherent interferometer to relate distance to frequency difference. Each pulse of the radar gives a depth profile in a particular direction, and HAZAL is equipped with a 2-dimensional scanning mirror assembly that allows the full 3-D volume to be built up. Of particular interest in this project is the fact that many explosive compounds and precursors (including TNT, RDX, and others) have resonant absorption features in this frequency range. The hypothesis is that by performing imaging spectroscopy, the presence of such explosive compounds can be detected. This is a capability that cannot be accomplished with other imaging technologies such as LIDAR (can only see the first surface), millimeter wave imagers (no resonant information), or passive imaging (no material data). The source of the funding for this project was the National Consortium for MASINT Research. In this first year of the effort, we demonstrated the ability to perform first-surface spectroscopy in the 820 – 830 GHz range. We also performed spectroscopy of RDX at 1.49 THz and 1.9 THz using borrowed hardware from the Subarctic Terahertz Observatory, a radio astronomy instrument also under development in our laboratory. In the second and third years of this effort (funded through other mechanisms) we will work to demonstrate full 3-dimensional, THz imaging spectroscopy.
