Many of these past applications are sound concepts; they have not blossomed into commercial businesses for a variety of reasons.
The deployment of millimeter-wavelength/terahertz technologies in aviation security applications has to be made with a full appreciation of multiple past failed attempts and the realistic promise that newer work and concepts offer. It can be said that the past millimeter-wavelength/terahertz business case suffered from a “chicken-and-egg” problem. Promising applications depend on low cost and the availability of hardware; low cost and available hardware depend, in turn, on investments associated with applications. It can also be said that this “crossover spectral region” where the radiation is neither optical nor electronic1 has created special challenges for the design engineer attempting to build hardware. Neither a compelling application nor a compelling breakthrough design concept has emerged to change the paradigm. Therefore, the committee is left with assessing the hardware and applications in an incremental or evolutionary sense, building on the current commercial progress.
First, there is no evidence for a current compelling application in the millimeter-wavelength/terahertz spectral region. There does seem to be new promise for a number of industrial or medical applications that are useful. Based on recent developments one can cite the following:
Nondestructive inspection through dielectrics using TTDS pulse techniques,
Medical use through skin or thin tissue for nonintrusive inspection, and
Millimeter-wave imaging of people to detect contraband underneath clothing.
The committee notes that the imaging of people using millimeter-wave techniques is not really a compelling application, since x-ray techniques can also be used. The millimeter-wave techniques have one stand-out advantage. This radiation is non-ionizing and does not cause tissue damage, which trumps x-ray techniques if an individual is to be inspected repeatedly in a venue such as a prison. If one credits public perception as an important consideration (and this has certainly been the case in some screening applications), millimeter-wave trumps x-ray inspection for the general public. Still, the intrusive inspection of people may require extensive public relations campaigns for either technique to succeed. This may be a less prominent issue for government applications. Otherwise, cost and performance determine the usage.
A clear-cut case can be made for a millimeter-wave portal used for scanning people. Several businesses, Millitech, MilliVision, QinetiQ, SafeView, and Trex Enterprises, are building hardware and creating the production environment essential to successful portal performance, reliability, supportability, and cost reduction. Venture-capital investment is attracted by the business diversity of such a portal, which can operate to detect drugs and guns carried by people, for purposes of transportation security, security of government buildings, security of ports, customs, requirements of prisons, security of commercial buildings, and so on. Applications have been developed that use millimeter-wave imaging for the fitting of clothing as well as for the detection of the removal of contraband, such as computer hardware from industrial sites. All of these business opportunities are enhanced by the increasing global terrorist threat and the