New terahertz security opportunities based on nanometric technology

Abstract

To identify weapons hidden under the apparel of people walking through entrance gates it is important to use THz illumination of sufficient power levels and fast image detection and processing. Various approaches of THz generation by nanometric dimensions are under studies in connection with semiconductor structures as well as electron beam systems. The issues of a THz camera are discussed. Power-level increases require paralleling many sources such as those of two-laser optical mixing in suitable non-linear materials or those of ballistic resonances in heterostructures of nanometric dimensions. In particular heat-sinking optimization is required so that THz-illuminating sources can be distributed along the frame of the entrance door for efficient employment of imaging facilities. THz detection is then using optical mixing so that phase and amplitude data can be derived by a matrix of pixels for ultrafast imaging. These pixels need to have antennas with low side lobes to avoid ghost images, produced by transverse resonances of the pixel matrix. The THz frequencies employed are initially aimed at narrow-band facilities of 830;GHz to identify metal and dielectric objects. This means that the required antennas for sending and detection can be based on dipole schemes. The ultimate wide-band possibility to identify the chemical compositions of explosive materials needs the wide-band antennas, such as half-spherical Si lenses. © 2013 Springer Science+Business Media Dordrecht.