以三維裂環共振器實現之等向性完美吸收體

Isotropic perfect absorbers realized by three-dimensional split ring resonators

陳淑嫣(Shu-Yen Chen)

指導教授 ： 嚴大任

國立清華大學/工學院/材料科學工程學系/碩士(2019年)

摘要

超材料完美吸收體自成功地實現於多種幾何形狀的實驗研究以來，透過各式各樣的實際應用展現其廣泛的用途。隨著超材料的發展和奈米科技的進步，許多基於超材料完美吸收體所製造的元件由平面轉成立體化。因此，許多三維結構所具有的獨特性質和迷人特性為超材料領域帶來了新奇並使其成長。
在三維超材料的製備中我們採用了應力驅動技術，即存在於材料系統中的應變梯度驅使平面圖形在經過選擇性蝕刻後捲起而形成三維圖形。此方法的優點是不需要重複地進行複雜的曝光步驟即能直接由一個平面組成立體結構。如此一來，既節省了大量的時間又能避免在曝光過程中由於未精確對準而造成的不完美，藉此提高了應力驅動的自組裝技術在奈米科技中的地位。
綜合以上所述，本論文提出了一種透過應力驅動的自組裝技術所建構的等向性三維超材料完美吸收體。透過各項數值模擬以及實驗的結果驗證了此結構不僅具有不受偏振角度影響的特性，還具有能夠容忍光以較大傾斜角度入射的能力。最重要的是，這個三維吸收體在中紅外波段的吸光度可達到97%以上。而在應用方面，我們在實驗過程中觀察到可以通過改變在此三維結構設計中捲起的手臂之曲率以調整其吸光能力的強弱。因此，我們將此發現視為此等向性三維完美吸收體可做為可調諧元件的潛力。展望未来，隨著奈米技術和超材料的發展，這個三維超材料完美吸收體值得被期待以多樣的方式進行各式應用。

關鍵字

超材料 ； 完美吸收體 ； 三維 ； 自組裝 ； 中紅外 ； 不受極化角影響

並列摘要

Metamaterial perfect absorbers (MPA) have been broadly implemented in a variety of practical applications since they were successfully demonstrated with several kinds of geometry. With the evolution of metamaterials as well as the progress of nanotechnology, a lot of devices based on the MPA are transformed from planar patterns into stereoscopic structures. Consequentially, numerous unique and fascinating properties stemming from three-dimensional structures bring about the novelty and growing in the field of metamaterials.
As for the fabrication of the three-dimensional metamaterial, we adopted the stress-driven technique in which the strain-gradient exiting in the material system drove a flat pattern to roll up into a three-dimensional structure after the selective etching process. The advantage of this approach is that a stereoscopic structure can be formed directly from a planar pattern without multiple and complicated exposure steps. In this way, both the significant time saving feature and the avoidance of imprecision resulting from the misalignment during the exposure promote the status of stress-driven self-assembly technique in the nanotechnology.
To summarize, in this thesis, we propose an isotropic three-dimensional metamaterial perfect absorber which is constructed by the stress-driven self-assembly methodology. Not only the independence of polarized angle but also the wide tolerance of oblique incidence is presented by our designed structure numerically and experimentally. Most of all, this three-dimensional absorber achieves the absorbance up to 97% in the mid-infrared region. In terms of its application, we discover that the curvature of arms is one of the factors that can adjust the absorptive ability of this three-dimensional absorber, and which makes the perfect absorber a potential candidate for tunable devices. Going forward, with the growth in nanotechnology and metamaterials, it is expected that this metamaterial perfect absorber based on the vertical split ring resonators (VSRRs) can be used in a variety way.

並列關鍵字

Metamaterials ； Perfect absorber ； Three-dimensional ； Self-assembly ； Mid-infrared ； Polarization-independence

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