利用雙天線超穎材料操控兆赫波行為之研究

Abstract

近年來，由於在非侵入式成像、醫療診斷、高頻寬通訊和非破壞性量測中的應用，兆赫波引起了相當大的關注，引起世界各地廣大的研究興趣。但由於受到有限的發射源及偵測靈敏度上的限制，以及在空氣中傳輸受水氣影響等問題，如何廣泛的利用兆赫波成為一大難題。有些團隊致力於研究做出更高強度、穩定的發射源、更靈敏的偵測器，也有許多團隊利用光、電、機械形變等方式對兆赫波進行調製。其中，將不同的超穎材料結構使用在兆赫波的領域有了巨大的進展。 然而，在實際應用上，利用超穎材料的技術仍然受到其繁複的調適能力和有限工作頻寬的阻礙。因此在本篇論文中，希望透過使用有限元素分析法模擬軟體，模擬出適合應用在兆赫波波段的雙天線超穎材料結構，藉由不同的天線佈置、入射光調變及機械性調變，來探討共振模態及控制共振頻率位置。搭配兆赫波的時域光譜進行在光學上的特性量測，並透過傅立葉轉換的計算得到其頻譜。實際製作出樣品後發現，隨著雙天線的夾角不同，可以成功地調變出0.7THz到1.1THz範圍內的兆赫波供應用。此外，也發現利用不同的入射兆赫波偏振方向可以控制共振模態，這些均與模擬結果相符。而為了可以更好的應用，我們將雙天線結構製作於可撓式基板上，進行更進一步的研究，未來可望將其應用於實際的光學探測及調變上。

Nowadays, terahertz (THz) waves have attracted considerable attention from a wide range of research interests in non-invasive imaging, medical diagnostics, high-bandwidth communications, and non-destructive security scans. However, the application of THz waves is restricted because of the limited light source and detective resolution of THz waves and the absorption of water in the air. Some groups work toward finding out a stronger, more stable light source or a more sensitive detector, and many groups try to modify the THz waves through kinds of ways. In these researches, the combination of different metamaterial structures to modulate THz waves has made great progress. However, the practical application of metamaterial is still limited by its complex debugging capabilities and narrow operating bandwidth. In this thesis, we utilized the Finite Element Method (FEM) to simulate and then find out a better double antenna structure which is operating in the range of THz waves. We successfully simulated the resonance modes and resonant frequency of structures with different antenna arrangements and the different polarization of light sources. After we successfully fabricated the sample, we analyze it from its time-domain spectrum, and calculate it with Fourier transform. Finally, we successfully found out that the spectrum can be modified in the range between 0.7THz and 1.1THz through the different angle between two antennas, which can be applied to the optical detection and modulation. Furthermore, we also observed that the different polarization of incident THz waves would influence the resonance modes, which confirms the simulation results. For further application, we fabricate the double antennas structure on flexible substrate, and we expect that it could be widely utilized in the future.