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consumes on the order of 1nJ/bit (the device itself only consumes 670pJ/bit) or active
transmission using a laser diode and steerable mirrors. 12
For optical data communication the following are considered: nano optoelectronics,
diffractive optical elements, optoelectronic transducers and photonic components.
Nanostructured optoelectronic components include quantum wells, quantum dot lasers as
well as photonic crystals. Already, two-dimensional photonic crystals can be routinely
manufactured with high precision. At present, efforts are being intensified to develop
three dimensional photonic crystals, which would open up new possibilities in optical data
communication (light could be guided and branched in defined directions) and offer, in
principle, the potential of purely optical circuits (optical computing).
Infrared sensors are an alternative approach for optical data communication. The
miniaturization and further improvement of infrared sensors are based on, among other
things, the application of two (quantum well), one (quantum wire) or zero-dimensional
(quantum dot) nanostructures. With the help of quantum well or quantum dot structures
the detection characteristics of infrared sensors can be adjusted selectively to the
relevant spectral region (band gap engineering).
2.5 Conclusions
The topicality of civil security stimulates the support of technological advances by
authorities as well as companies which see interesting market opportunities. Indeed, new
detection devices are not only developed to replace or enhance currents ones, but to
embed systems in public places in order to limit accidents as well as terrorist attacks.
This requires cheaper devices that are easy to use, and able to detect a variety of agents
quickly and with a high degree of accuracy.
To achieve this requires nanotechnology advances. Nanotechnologies have applications in
several imaging devices (X-ray, infrared, THz detection), but it is in the range of
biological and chemical detection that they are the most advanced. Biotechnology
advances using nanoparticles and quantum dots as bio-detectors, have allowed rapid
progress in security applications. Rapid progress has also been made in the field of
chemical detection based on carbon nanotubes. Finally, nanotechnology offers the
possibility of multiplexing, or performing analyses on a number of different targets on the
same sensor in an array form. This application may be more of a mid- to long-term
prospect, but will highly facilitate detection and accelerate results.
The most impressive advance allowed for by nanotechnology development is the
possibility of autonomous sensor networks. These networks will be able to not only
capture data but process information, transmit it, and communicate with others sensors
in potentially hostile environments. The extremely small size of these devices, in addition
to a very low price, could make them next generation of sensor for civil security. Indeed
they have the potential to limit the requirement for human intervention in dangerous
places.
12 http://www-bsac.eecs.berkeley.edu/archive/users/warneke-brett/pubs/cbnp_workshop-summary.html
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