平面次波長週期結構之異常穿透與吸收特性

次波長週期結構在物理科學領域當中具有兩種特性，一種為空間中電磁波的濾波特性，另一種為提供在天然材料中不存在或不易見的物理特性。次波長週期結構在設計上具有相當高的自由度，因此可以將其應用於微波、兆赫波和光波波段的元件當中，來增進效能或提供其他功能。使次波長週期結構有這些特性的物理機制來自於共振，有因為幾何結構所產生的site共振或因為週期性的晶格排列而產生的晶格共振，還有表面電漿共振、波導模態共振或共振腔模態等，而這些不同的共振模態相互耦合下，還能產生Fano共振。在了解這些共振機制之後，將可以更容易設計來達到目的。本論文目的在探討電磁波在次波長週期結構異常穿透與異常吸收之行為，其重點為共振模態之分析與發生機制之探討，再來設計出最佳化之結構。首先，提出完美導體週期結構的微小化擇頻表面，利用蜿蜒曲線來增長環形孔洞長度使全穿透的site共振增長共振波長，可以達到晶格微小化的效果，並且發現共振波長與蜿蜒曲線的摺數有高度相關，如此一來結構之共振波長便可以預測，將易於設計與應用。接著，在了解真實金屬的孔洞與貼片在光波與紅外光波段的穿透與吸收行為後，設計出金屬與介電質的多層結構，藉由激發金屬介面上的表面電漿模態共振與介電質中的波導模態共振，可以得到一個寬頻廣角的近完美吸收結構。

關鍵字

次波長週期結構；超常材料； site共振；晶格共振；表面電漿共振；波導模態共振；共振腔模態； Fano共振；微小化擇頻表面；異常穿透；異常吸收

並列摘要

Subwavelength periodic structures have two characteristics in physical science. One is the spatial filtering effect of electromagnetic waves, and the other is providing unusual or nonexistent physical properties. Subwavelength periodic structures have lot of degree of freedoms in design. Therefore, they can be used in the component of microwave, terahertz regime, or visible regime, to approve the efficiency or to provide the other effects. Resonance is the physical mechanism of subwavelength periodic structures. Site resonance can be excited by the geometry in a unit cell. The periodic lattice arrangements bring about lattice resonance. In another way, the interaction between electromagnetic wave and different materials can excite like surface plasmon resonance, guided mode resonance, and Fabry-Perot resonance. In particular, the coupling between these resonances is related to Fano resonance. After realize the mechanism, subwavelength periodic structures can be more easily designed to achieve the purpose. The object of this thesis is to study the anomalous transmission and absorption of the subwavelength periodic structures. This thesis emphasizes the analysis of resonant mechanism, and then designs optimal structures. First, we purpose miniaturized element frequency selective surface made by perfect conductor. By using meander-line aperture, the resonant wavelengths of site resonance increase, that is, the lattice constant is miniaturized. Moreover, we find the relation between resonant wavelengths and the folding number of meander-line. Because the resonant wavelengths are predictable, the structures will be easy for design and application. Then, after studying the transmission and absorption of real metal structure in visible regime and near infrared regime, we design multi-layer structures made by metal and dielectric slab. By exciting the surface plasmon resonance of metal surface and the guided mode resonance in dielectric slab, there are nearly perfect absorption with broad band and wide angle of these structures.

並列關鍵字

subwavelength periodic structure ； metamaterial ； site resonance ； lattice resonance ； surface plasmon resonance ； guided mode resonance ； Fabry-Perot resonance ； Fano resonance ； miniaturized element frequency selective surface

參考文獻

[1] B. A. Munk, Frequency Selective Surfaces: Theory and Design: Wiley-Interscience, 2000.

[2] R. Mittra, et al., "Techniques for analyzing frequency selective surfaces-a review," Proceedings of the IEEE, vol. 76, pp. 1593-1615, 1988.

[3] C. Caloz and T. Itoh, Electromagnetic Metamaterials: Transmission Line Theory and Microwave Applications: Wiley-IEEE Press, 2006.

[5] A. Alu, et al., "Plasmonic brewster angle: broadband extraordinary transmission through optical gratings," Physical Review Letters, vol. 106, p. 123902, 2011.

[6] X.-R. Huang, et al., "Making metals transparent for white light by spoof surface plasmons," Physical Review Letters, vol. 105, 2010.

國際替代計量

平面次波長週期結構之異常穿透與吸收特性

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