Terahertz Interferometric Imaging Systems (TIIS) for Detection of Weapons and Explosives

We propose to develop a continuous wave terahertz interferometric imaging spectrometer tunable from 0.2 to 3 THz in order to remotely detect, monitor and identify concealed explosives such as C4 and RDX as well as metal weapons. The fully realized systemwill consist of a high brightness THz source illuminating the region of interest and detected by a tunable THz interferometric imaging array. The array will consist of a multiple spaced THz semiconductor heterodyne photomixers driven by a common fiberoptic coupled frequency stabilized tunable optical heterodyne source. In phase I, a wide field of view and high spatial resolution THz imaging array will be designed. A proof of principle array will be constructed using modified commercial THz photomixingmodules driven by a diode laser optical heterodyne source. Initial tests will be made using homodyne photomixing detection. The geometrical array parameters, type of antennas within the array, antenna optics, and optimum high power source will beevaluated to best image at short-range target objects concealed within transparent dielectrics. Photomixing devices will serve both as source and detectors in Phase I. A database of required THz-frequency spectral signatures for target explosives will bedeveloped using existing time-domain THz spectroscopy equipment. A successful Phase II will result in a compact tunable THz remote detection system for concealed explosives and weapons. No such interferometric imaging THz spectrometer is currentlycommercially available. The proposed system will be useful not only in defense applications as a stationary perimeter defense system and outward looking remote surveillance system, but for civilian security applications as well, such as airport screeningfor explosives, biological agents, and other contraband. In addition, the components designed will have commercial applications manufacturing, process control, medical, and environmental diagnostics.