| Summary: | 碩士 === 國立臺灣大學 === 應用力學研究所 === 99 === 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.
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