<title>Terahertz technology in global homeland security (Invited Paper)</title>

Abstract

The terahertz (1 THz = 10¹² Hz, 3 mm or 33 cm^-1) region of the electromagnetic spectrum is typically defined in the frequency range 100 GHz to 10 THz, corresponding to a wavelength range of 3 mm to 30 microns. Following the development of coherent sources and detectors in the early eighties, there has been growing interest in the role of terahertz technology in global homeland security. The terahertz region offers a huge expanse of unused bandwidth. The ability of terahertz radiation to probe intermolecular interactions, large amplitude vibrations and rotational modes, in addition to showing polarization sensitivity makes terahertz radiation a unique and diverse region of the electromagnetic spectrum. Terahertz radiation is also able to 'see through' common materials, such as clothing, thick smoke and dust, which are often considered as opaque in other regions of the electromagnetic spectrum. This paper reviews the role of terahertz technology in homeland security and associated limitations of this field.