The Essence of Dielectric Waveguides pp 339-357 | Cite as
Ultra Low-Loss Dielectric Waveguides
It is the extraordinary low-loss property of silica in the optical spectrum that enables the development of optical fibers as high capacity/long distance communication links. This low-loss behavior of silica is attained through the elimination of impurities, which are the causes of loss [1]. In the low frequency spectrum, lower than 30 GHz, conducting metals such as silver, copper, gold, and aluminum are generally adequate as structures for low-loss waveguides [2]. However, there remains an important region of the spectrum – from 30 to 3,000 GHz (the millimeter– submillimeter band) – where low-loss waveguides are not available. The main problem here in finding low-loss solids is no longer due to only one of the eliminating impurities, but is due to the presence of intrinsic vibration absorption bands [3]. The use of highly conducting materials is also precluded in this part of the spectrum owing to high skin-depth losses [4, 5]. In this chapter we show that a combination of material and waveguide geometry can circumvent these difficulties. For example, a ribbon-like waveguide structure with an aspect ratio of 10:1, fabricated from ceramic alumina (Coors 998 Alumina), can have an attenuation factor of less than 10 dB km−1 in the millimeter–submillimeter band. The attenuation is more than 100 times smaller than that of a typical ceramic (or other dielectric) circular rod waveguide. The main purpose of this chapter is to show that there may be another option, other than finding the ideal low-loss material, to construct a low-loss waveguide in the millimeter–submillimeter band.
Keywords
Dielectric Constant Relative Dielectric Constant Microstrip Line Dielectric Waveguide Attenuation ConstantReferences
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