Proc. SPIE. 6212, Terahertz for Military and Security Applications IV
KEYWORDS: Defense and security, Digital signal processing, Imaging systems, Chemical species, Molecules, Terahertz radiation, Picosecond phenomena, Information security, Molecular electronics, Amplitude modulation
An implementation and review of our recently proposed scenarios [1-13] for processing and transfer of information is presented. We will show how computing using molecular potentials and vibronics communications can be adapted to upgrade present charge-current approaches, which are already in the limits of their technical and perhaps physical limits because their immense heat dissipation problems. It has long been recognized the many advantages and potential payoffs that the development of THz based applications could bring to the military and security areas. We focus our implementation in the development of THz sensing and imaging for a wide range of military and security applications as systems operating at these frequencies have shown to have high sensitivity and selectivity when applied to the analysis of molecules. These are properties that are highly desirable in the design of sensing tools for the detection, identification and characterization of chemical and biological agents; and in the design of monitoring tools for the detection of these substances, both in closed and, with less selectivity, in open environments. Many materials of interest for security applications including explosives, and chemical and biological agents have characteristic THz fingerprints which set them apart from non-hazardous materials, thus allowing their identification. As molecular electronics techniques become available , they could sharply improve our present detection and sensing techniques.
We proposed two scenarios for signal encoding and transmission in molecular circuits that can be used for standoff detection of biological and chemical agents: one is based on the characteristic vibrational behavior of molecules and clusters and the other is based on their molecular electrostatic potentials. It is proposed that these two scenarios can be used for molecular signal processing and transfer in molecular sensors; theoretical demonstrations using state of the art and precise computational techniques are presented for these two paradigms. The molecular electrostatic potential in the neighborhood of a molecule has very well defined zones of positive and negative potential that can be manipulated to encode information. On the other hand, vibrational modes of long molecules can be used to transfer signals between distances not accessible by standard fabrication techniques. In additions, the development of molecular amplifiers allows us to transfer signals through the nano- micro interface needed to pass the information to the macroscopic world. These scenarios allow extremely lower energies, higher speeds, and higher integration densities than in any other technology. Thus, the use of these two low-power consumption and extremely large bandwidth approaches allow us to operate at the THz range, the natural operation frequency of biological and chemical species. A review of our search for other scenarios for coding, processing and transport of information for sensing detection are provided.
Several problems, almost impossible to defeat, among them, heat removal, addressing small devices, and fuzziness at atomistic scales confronts standard CMOS electronics. What we are concluding after intensive research is that the material is not the major problem but the way how we encode information is what can allow us to continue the steady exponential grow in computational power know as the Moore's law. Although molecules and nanoclusters are the alternative for scaling down devices, we need to develop scenarios for information coding and transfer in molecular circuits able to operate at integration densities and speeds orders of magnitude higher than in present integrated circuits. A simple scaling down using the same scenarios being used in today's microelectronics devices does not offer much hope at the atomistic and nanoscopic levels. We proposed two scenarios: One is based on the characteristic vibrational behavior of molecules and clusters and the other is based on their molecular electrostatic potentials. It is proposed that these two scenarios can be used for molecular signal processing and transfer in molecular circuits; theoretical demonstrations using computational techniques are presented for these two paradigms. The molecular electrostatic potential in the neighborhood of a molecule has very well defined zones of positive and negative potential that can be manipulated to encode information and vibrational modes of long molecules can allow us to transfer signals. Both scenarios allow very lower energies, higher speeds, and higher integration densities than in any other technology. A review of our search for other scenarios for coding, processing and transport of information is provided.
We review dynamic simulations on a molecular device named "nanocell" proposed for THz signal processing. In this preliminary study we conclude that signals applied to nanosized gold clusters interconnecting single molecules can modulate vibrational modes in the THz spectrum of the internal coordinates defining molecular bonds. Intensities involved in natural vibrational modes, which are experimentally recoverable in spectroscopy measurements. We can recover components due to couplings between local modes, and thus we provide a computational simulation of the possibility of using molecular vibrational modes for molecular electronics. The vibration of atoms can encode information that reflects local variations of electrical dipole and polarizability.