透過隨機設計的方式，我們提出了三種不同圖形的雙面超材料完美吸收體，其結構為兩層金屬層中間夾介電層的三明治結構，在特定頻率下可以完美地吸收來自兩個相反方向的電磁波。藉由有限積分時域法的模擬結果，我們提出的雙面超材料完美吸收體在1.146 THz工作頻率下，其吸收率可以達到95.45%並有0.0888 THz的頻寬。另外，我們透過多重反射理論計算出與模擬結果非常相似的吸收值。藉由計算在多重反射模型中各個地方的場值、能量以及等效的介電係數、導磁係數、折射率和損耗，我們主張超材料雙面完美吸收體是因為阻抗匹配導致反射很低，而穿透很低的原因則是因為在共振頻率時超材料雙面完美吸收體的高等效損耗係數。另外，我們使用黃光微影製程製作試片並用霍氏轉換紅外光譜儀量測試片的穿透值與反射值，量測的結果與模擬的結果非常一致且只有0.3%的頻率偏移量。最後，我們透過電場分佈圖以及能量分佈圖證實了我們提出的雙面超材料完美吸收體確實可以將電磁波完美地吸收。

We have proposed three different designs of the double-sided perfect metamaterial absorbers (PMAs) through a metal-dielectric-metal three-layered prototype with randomly developed metallic patterns, which can absorb the incoming light from the two opposite directions. Then, we characterize the double-sided PMAs with the aim of the finite integration time domain method, which demonstrates that our proposed double-sided PMAs can possess an absorbance peak of 95.45% at 1.146 THz with the bandwidth of 0.0888 THz for the two different directions of the normal incident light. Also, the multiple reflection theory suggests the identical result compared to the numerical simulation. By calculating each component in the multiple reflections, we claim that the reflection dip of the double-sided PMA stems from the impedance matching, and the low transmission value is the result of the large effective loss tangent of the PMA. Further, the proposed double-sided PMAs are fabricated by the UV photolithography fabrication process and measured by the Fourier transform infrared spectroscopy. The measured transmittance and reflectance agree with the simulation results well with an offset of 0.3% in absorbance frequency. Finally, the electric field distribution and the power flow reveal that the electromagnetic wave is indeed absorbed by our proposed double-sided PMAs.

致謝 i
摘要 ii
Abstract iii
Table of content iv
List of Figures vi
Chapter 1 Introduction 1
1-1 Introduction to Metamaterials 1
1-2 Research Motivation 1
1-3 Thesis organization 2
Chapter 2 Literature review 4
2-1 Introduction to conventional absorber 4
2-2 Perfect metamaterial absorber 5
2-2-1 Introduction to perfect metamaterial absorber 5
2-2-2 Bulk effective medium model 7
2-2-3 Interference throry model 8
2-2-4 Other kinds of PMA 11
Chapter 3 Design and simulation 14
3-1 Pattern design through stochastic process 14
3-2 Simulation results of double-sided PMAs 15
3-3 Achieving the performance of double-sided PMAs by classic single-sided PMAs 18
Chapter 4 Methods and Experimental setup 20
4-1 Experimental flow 20
4-2 UV Photolithography 21
4-3 Oxygen plasma 22
4-4 Electron gun deposition and lift-off process 24
4-5 Fabrication of the second layer metallic pattern 25
4-6 Measurement equipment (Fourier transform infrared spectroscopy) 26
Chapter 5 Results and discussion 27
5-1 Calculation results 27
5-1-1 Multiple reflection theory 27
5-1-2 Parameter retrieve 29
5-1-2 Comparison between the simulaiton and the calculation results 32
5-1-3 The mechanism of the double-sided PMA 36
5-2 Experimental and measurement results 40
5-2-1 Transmittance spectrum 41
5-2-2 Reflectance spectrum of 11 degree incident angle 44
5-2-3 Transparency in visible range 46
5-3 Field monitor 48
5-3-1 E-field distribution 48
5-3-2 H-field distribution 50
5-3-3 Power flow 52
5-4 Scaling factor 55
5-5 Other custom-made design 57
Chapter 6 Conclusions 58
Appendix A 59
Appendix B 67
Reference 70

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