Semiconducting and superconducting nano-devices to control terahertz radiation: emitters, filters, detectors, amplifiers and lenses.

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Practically all electromagnetic radiation is heavily used by humankind. However there is a radiation with one range of frequencies which is still not used. This is so-called terahertz (THz) range and the associated problem is called the terahertz gap. The recent growing interest in THz science and technology is due to its many important applications in physics, astronomy, chemistry, biology and medicine, including THz imaging, spectroscopy, tomography, medical diagnosis, health monitoring, environmental control, as well as chemical and biological identification. The THz gap is difficult to bridge by either electronic or optical devices and it covers temperatures of biological processes and a substantial fraction of the luminosity remnant from the Big Bang due to the red shift falls into the THz gap. The problem exists because there are no practical sources, filters or receivers of electromagnetic radiation with frequencies in the THz range. Why is THz radiation (T rays) so important? T- rays may penetrate bodies but, in contrast with X-rays, leave no damage. The spectrum of T-rays penetration and absorption is frequency and material dependent. In a frequency range of a few THz the penetration depths through aqueous solutions is very limited, while plastic materials are practically transparent. If tunable and powerful sources and receivers of such radiation are produced everything can be scanned continuously. This would then initiate a new stage in medicine (cancer and other diseases could be detected and removed at a very early stage) and in the war against terrorism. Nanostructure-based THz-electronics may give many promising applications, ie in ultra-high bandwidth wireless communication networks, vehicle control, atmospheric pollution monitoring, inter-satellite communication and spectroscopy, to name a few. We anticipate that our proposal will be an important step in removing the technological Terahertz gap''.The focus of our research are THz emitters, filters, detectors, lenses and amplifiers based on metamaterial and semiconductor superlattices (M-SSL) and layered superconductors (LSC) with spatially modulated properties. The SSL can be used as a generator of THz radiation (T-rays). This is based on the phenomenon of Bloch oscillations, which have now been observed in many experiments with SSL. Most importantly the frequency of such electronic oscillations belongs to the THz range. Metamaterial superlattices (MSL) represent a new form of matter discovered recently by John Pendry et al and anticipated by Veselago where electromagnetic radiation of a very broad spectrum may be controlled, generated and trapped. Our preliminary estimations indicate that metamaterials where refractive index and permeability are negative are ideal to be used in the THz devices. Moreover the motion of Josephson vortices in the LSC may also generate T-rays. In a more simple form T-rays arise, when the speed of the Josephson vortices exceeds the THz light speed in superconductors. This will be simply Cherenkov radiation.Thus we propose to build various devices for the use of THz radiation such as THz emitters, filters, detectors, lenses and amplifiers using nonlinear and quantum effects existing in M-SSL and LSC. The first idea is to use unique properties of SSL as a transformer of the microwaves with gigahertz frequencies into radiation with THz frequency and vice versa. We propose to put SSL in a microwave resonator and investigate such a device as a possible source for THz radiation. In the second idea we will design metamaterials(MSL) to trap, to detect and to control THz radiation. In the third idea we will use the LSC which consists of thin superconducting layers separated by very thin insulating layers. There are natural LSC, such as, high temperature superconductors (HTSC) or they can be made artificially from superconducting and insulating materials, like SSL. There is a whole area of LSC engineering