Multi-band Terahertz Imaging System Design
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J15.3.1
Multi-band Terahertz Imaging System Design Liviu POPA-SIMIL Los Alamos, NM 87544 E-mail: [email protected]
ABSTRACT, Developing visualization devices in far infrared reveals tremendous advantages and focused the research of space agencies, defense and security as well many other private companies oriented to science. The THz wave emitters and receivers are less developed, compared to its neighboring bands (microwave and optical). During the past decade, THz waves have been used to characterize the composition and properties of solid, liquid and gas phase materials to identify their molecular structures. At the base of this development stays the possibility of achieving microstructures from conductive or super-conductive materials able to select by resonant criteria the emerging photons and drive into specialized detection devices. The problem to be solved is the ratio S/N because the energy of a single 1THz photon is 4.1 meV equivalent to a 47K temperature. A group of such highly selective micro-antenna can be grouped into a unit cell - called elementary multi-band detector. The development of resonant structures for frequency selectivity and directivity reasons coupled with the electrical field amplification and detection in low noise quantum transistors. Such an electronic system might be integrated in a modular structure and by multiplicity to create spatial sensors and phased arrays. INTRODUCTION Modern detection and imaging technologies is a valuable asset for a very large range of applications from medicine, security, defense and space. The terahertz domain is one of the less covered due to difficulties of producing generators – illumination sources –as well in handling the detection systems. At the lower frequency, in GHz domain, microwave equipment get a tremendous development, and I will emphasis on SAR (Synthetic Aperture Radar) [1] and GPR (Ground Penetrating Radar). At the other end of the THz domain at frequencies at about 300 THz λ=1µm, is the Infra Red Domain [2]. The thermo-vision results are widely known, and as a new remote sensing development the multi-spectral thermal imager is now equipping observation satellites increasing the power of the remote sensing. In this domain the molecular and lattice spectra have characteristic lines – most of materials have eigen-frequencies dependent on material type [3], material treatment (thermo chemical, hardening, etc.) grains size and orientation. At these frequencies materials are presenting absorption and transmission bands [4, 5] which are different from the visible and radar spectrum by pattern being specific to the class of phenomena taking place at the molecular and cluster level.[6]. The terahertz visualization and detection has defense [7] and security [8, 9] applications many private companies focused their science activities [10] in this domain. The THz wave emitters and receivers are less developed, compared to its neighboring bands (microwave and optical)., THz waves presents advantages for detecting the properties of solid, liquid and ga
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