Popular Summary: In the rapidly advancing arena of modern telecommunication technology, new concepts or paradigms are being sought for guided and lossless transmission of surface electromagnetic waves at the terahertz and higher frequencies. In this paper of combined theoretical and experimental work, we put forward just such a concept that marries the classical idea of surface electromagnetic waves with some very recent advances in metamaterials research.
Surface electromagnetic waves, first predicted by Arnold Sommerfeld in 1899 in the form of an axial cylindrical wave, are low-frequency electromagnetic waves that are bound to a metallic interface between two different media and travel without radiation loss. They can serve as guided waves that are of vital importance in routing electromagnetic energy from a source to a device or receiver and become especially competitive for integrated telecommunication devices in the frequency range of terahertz. Metamaterials, emerged only recently, are a broad class of materials constructed of individual elements in a bottom-up approach, with the designed-on-demand capability of manipulating or modulating electromagnetic waves propagating in free space. Our concept combines a planar gigahertz or terahertz version of the Goubau transmission line—well known in the radio-frequency transmission technology—with a few coupled metamaterial elements (electric-ring resonators) judiciously placed next to the Goubau line. We have demonstrated that the metamaterial elements can be designed to either absorb or transmit the surface-wave energy in the Goubau line and yield narrow-band resonances with relatively high quality factors. By tuning the coupling between the metamaterial elements, we have also succeeded in achieving a large dynamic range of transmissivity.
Our proof-of-concept demonstration should trigger new developments in ultrahigh-speed data transmission and processing and lead to a place for metamaterials in future high-bandwidth terahertz communications.
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