本研究設計與分析一系列具有多波段吸收特性的兆赫茲超材料吸收器，結構採用金屬–介電–金屬（Metal–Insulator–Metal, MIM）形式，並以高阻值矽為介電基板，銀為上下金屬層材料。藉由調整上層金屬的幾何圖形，設計出五種具代表性的單元結構（Meta1 至 Meta5），並利用 CST Microwave Studio 進行模擬，探討其電磁吸收性能及共振機制，並搭配 THz-TDS 系統進行反射模組實驗驗證。
模擬與實驗結果顯示，所設計結構皆展現明顯的多頻吸收特性，吸收率最高可達 0.95，其中 Meta3 結構展現出最低平均誤差與最佳重現性。進一步分析場分布與表面電流特徵，揭示吸收峰主要來自偶極共振、LC 共振與高階模態耦合等多種共振機制，並觀察不同模態間之場能量集中現象。另從半峰全寬與 Q 值分析可知，Meta2 的共振峰最為尖銳、頻率選擇性最佳，Meta3 則擁有最多吸收峰但頻寬較寬，而 Meta5 在模擬與實驗間呈現良好一致性，顯示具備吸收穩定與設計潛力。此外，亦以傳輸矩陣法模擬理想平面 MIM 結構，驗證 Fabry–Pérot 型干涉效應在無圖形結構下之吸收能力，強調圖形設計對多頻共振實現之關鍵性。
本研究亦探討材料參數變異對吸收效能之影響，發現高阻值矽基板具較佳吸收表現，適合作為中間層材料。並提出未來可透過氣體置換與除濕手段改善量測準確性。對於結構設計方面，建議可導入更薄之介電層材料以降低干涉效應，同時探索分形幾何與主動材料的應用，以實現多頻或可調式吸收器之功能性提升，或結合兆赫茲超材料波導耦合元件。整體研究成果驗證了 MIM 結構在兆赫茲波段的吸收能力，為後續感測器與濾波元件設計提供可行方向與理論依據。

This study presents the design and analysis of a series of multiband terahertz metamaterial absorbers based on the metal–insulator–metal (MIM) structure. The proposed absorbers utilize high-resistivity silicon as the dielectric substrate and silver as the top and bottom metallic layers. Five representative unit-cell designs (Meta1 to Meta5) were developed by tailoring the geometry of the top metal patterns. Electromagnetic absorption characteristics and resonance mechanisms were investigated through CST Microwave Studio simulations, and experimental validation was performed using a terahertz time-domain spectroscopy (THz-TDS) system in reflection mode.
Simulation and experimental results demonstrate that all proposed structures exhibit distinct multiband absorption characteristics, with peak absorptance values of up to 0.95. Among them, Meta3 shows the lowest average error and best reproducibility. Field and surface current distribution analyses reveal that the observed absorption peaks originate from various resonance mechanisms, including dipole resonance, LC resonance, high-order mode coupling, and localized field concentration across different modes. Additionally, analysis of the full width at half maximum (FWHM) and quality factor (Q) shows that Meta2 exhibits the sharpest and most frequency-selective resonance peaks; Meta3 supports the most significant number of absorption modes but with broader bandwidths; and Meta5 demonstrates strong consistency between simulation and experiment, indicating good absorption stability and design potential. A complementary simulation using the transfer matrix method for an ideal planar MIM structure further confirms that Fabry–Pérot-type interference contributes to the absorption behavior in non-patterned configurations, highlighting the critical role of pattern geometry in achieving multiband resonance.
This study also examines the influence of material parameter variation on absorption performance and confirms that high-resistivity silicon provides superior absorption, making it a suitable dielectric layer. Gas purging and dehumidification methods are suggested to improve measurement accuracy. For future design enhancements, thinner dielectric layers are recommended to suppress interference effects. The exploration of fractal geometries and active materials is also proposed to realize tunable or multifunctional absorbers, potentially combined with terahertz metamaterial waveguide-coupled components. The overall results verify the effectiveness of the MIM structure in the terahertz regime and provide theoretical and practical guidance for future sensor and filter device development.

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