Research On The Theory And Process Of Metamaterial Terahertz Absorber

Metamaterial is a kind of novelly aritificial electromagnetic material whose structure is generally composed of periodic array cell, and the electromagnetic property of it is strongly depend on the designed structure. Terahertz(THz) wave have some advantages such as the good security, the high content of spectral information, the strong penetrability and the wide bandwidth. Thus, it has many potential applications, such as communication, biomedicine, substance identification and national defense, et al. With the rapidly development of the micro-nano machining process and the THz technology, the research on the metamaterial THz absorber based on the micro-nano machining process becomes one of the research focus in the field of THz functional devices.Firstly, based on the time domain finite integral method, this thesis designs a novel THz broadband absorber with sandwich structure, and analysis the principle of electromagnetic absorption of the metamaterial absorber in detail, as well as the situation of the different parameters influence the absorption curve. The simulation results show that the bandwidth achieves 1.2 THz for the absorption beyond 80%. It’s full width at half maximum(FWHM) is 1.6 THz, and the maximum absorption is up to 98.7%. Moreover, the absorber is insensitive to the polarization direction, and has wide angle of absorbing. If change the structure size in proportion, the working frequency band of the absorber can be extended to the band of microwave and infrared. This broadband absorber has potential applications in the field of electromagnetic stealth, thermal radiation detecting and THz broadband communicating.In addition, this thesis introduces the MEMS(Micro-Electro-Mechanical Systems) micromachining process and it’s characteristic in detail. And at the same time, the design method of the absorber is also presented. At last, after carry out the THz tunable absorber by the software of CST, the tunable absorber is fabricated by using commercial MEMS process, then analysis the principle of electromagnetic absorption of the tunable absorber, discuss the situation of the different parameters influence the absorption curve. After all, the modulation characteristic of the absorber is verified by the experiment. The simulation results show that the low-frequency absorption peak appears redshift and the modulation of amplitude is about 2.2%, the variation of the absorption is 0.5%; the modulation of amplitude at the middle-frequency absorption peak is about 5.7%, the variation of the absorption is 7.4%; the modulation of amplitude at the high-frequency absorption peak is about 0.65%, and the variation of the absorption is 3%. The experiment results also show that the low-frequency absorption peak appears redshift and the modulation of amplitude is about 0.7%, the variation of the absorption is about 0.5%; the modulation of amplitude at the middle-frequency absorption peak is about 3.9%, the variation of the absorption is 1%; the modulation of amplitude at the high-frequency absorption peak is about 1.4%, and the variation of the absorption is 8%. The simulation results are in good agreement with the experiment. This THz tunable absorber can be treated as THz modulator, and can be applied in many fields, such as frequency selective spectral detecting, THz switches, multi-spectral imaging and so on.