New THz Technologies and Applications in Applications in Support of Safety and Security

Abstract

Recent incidents have prompted changes to the methods employed for security screening at airports and border security check-points. At cargo screening facilities and major border check-points, where thousands of containers need to be screened rapidly, it is a challenging task to effectively screen each container. As a result, there is an increasing focus on new technologies that can be applied for security screening in a stand-off mode, either to simplify or speed up the screening process, or to provide additional functionality. Terahertz (THz) technology is a promising and emerging technology and has been considered in various forms. Additionally in the battlefield, one of the major threat vectors is improvised explosive devices (IEDs) used in different forms such as vehicle borne IEDs (VBIEDs) or strapped to humans at inconspicuous locations. THz imaging systems can be used to image such threat vectors, since such materials have characteristic THz spectra. The use of THz illumination of sufficient power levels and fast image detection and processing, has shown that non-metallic weaponry can be imaged when concealed beneath clothing. Some of the barrier and potential confusing materials have smooth spectra with relatively low attenuation. However, use of the THz frequencies, initially aimed at narrow-band at 830 GHz along with optical mixing can be used to identify metal and dielectric objects. The ultimate possibility to identify the chemical compositions of explosive materials and mixed chemical compositions needs the wide-band antennas. Potential use of THz imaging in active and passive imaging systems for detection of chemical and biological agents and remote monitoring of signals is described. Selected applications of THz for stand-off detection are described by using nanomaterials to generate and detect response signal, and also to demonstrate that the THz spectra of several common chemicals, explosive compounds, and pharmaceuticals are distinct for ease of identification.