The Research Of Terahertz Functional Devices Based On Electromagnetic Metamaterials

During the past 20 years, terahertz technology has gained rapid development, from the original "terahertz gap" to current research hotspot. The development of terahertz high-speed wireless communications, detecting and imaging, medical diagnostics and other applications are at very critical stage and gradually transit to the industrialization. Accordingly, the research of core devices of these application systems has been attached great importance. As is all known, due to the unique frequency range in the whole electromagnetic wave, there is a serious lack of materials and devices in terahertz regime, which makes the construction of terahertz system really difficult. In this thesis, we focused on exploring the utilization of artificial electromagnetic metamaterials to try to build functional devices, demonstrating the methods and processes of how to take advantage of this new-type material to study practical terahertz functional devices.Metamaterial as a new design concept of materials has totally different properties from traditional materials. Through the reasonable control of its permittivty and permeability characteristics, we can build varieties of novel devices, which can be applied in terahertz security monitoring, wireless communication, detection, imaging, spectroscopy analysis and other fields.Firstly, this thesis utilizes metamaterials to build terahertz absorbers. We use LC resonance model to explain absorber’s working mechanism, use simulation software CST Microwave Studio 2011 to design a centralized absorber based on SRR structure, of which frequency point absorbance is up to 90%. In order to get broader bandwidth, double-layer structure is introduced and the absorption bandwidth increases to 100 GHz. To achieve adjustability of the absorber, the introduction of vanadium dioxide "metal-insulator" phase change material is crucial to the absorber, and the utilization of its conductivity changing depending on temperature alters the absorber’s impedance matching characteristics. Comparing the environment of room temperature and a temperature greater than 68℃, the adjustable rate of original single absorber reaches 60%. Vanadium dioxide in the double-layer absorber makes the absorption band broadened sharply, reaching 190 GHz.Secondly, the thesis designs and prepares terahertz band-pass filter based on frequency selective surface. Two types of frequency selective surface, crossover and parallel, are designed by CST Microwave Studio 2011. We prepare the final product by MEMS fabrication method and RF magnetron sputtering, and test samples with the terahertz time-domain spectroscopy(THz-TDS) system, the results demonstrating that samples’ transmission rate is more than 85%, and its 3dB bandwidth has reached more than 48%.Both devices in this thesis are core devices of terahertz application system, on the one hand providing device basis to build a terahertz application system, on the other hand demonstrating the enormous potential of artificial electromagnetic metamaterials in the study of terahertz functional devices development.