本研究旨在表徵和測試電光可調諧太赫茲梯度漁網超材料。表徵包括確定不同的材料特性，例如折射率和消光係數，而測試包括確定超材料操縱入射太赫茲光束的不同能力（例如彎曲效應、透鏡效應等）。

在本論文中，提出了在太赫茲中使用可調諧漁網梯度漁網超材料（TGFM）進行波操縱的概念。 TGFM 設計有優化的晶胞幾何形狀和尺寸，具有大的負折射率和偏振無關和入射角不敏感的特性。使用不同的模擬以及實驗推導太赫茲輻射的 S 參數來解釋波操縱。這些 S 參數也用於確定 TGFM 的材料特性。所提出的 TGFM 能夠將入射光束彎曲到總共 11.88° 的角度。

This Research aims at characterization and testing of an electro-optic Tunable Terahertz Gradient fishnet metamaterial. The characterization includes the determination of different material properties such as refractive index and extinction coefficient whereas the testing include the determination of different abilities of the metamaterial to manipulate the incident terahertz beams (such as bending effect, lensing effect, etc.).
In this thesis, the concept of wave manipulation using a tunable fishnet gradient fishnet metamaterial (TGFM) in THz is presented. The TGFM is designed with optimized unit-cell geometries and dimensions with large negative refractive indices and polarization-independent and incident angle insensitive properties. Wave manipulation was explained using different simulations as well as experimentally deriving the S parameter of the THz radiation. These S parameters were also used to determine the material properties of the TGFM. The proposed TGFM possesses the ability to bend the incident beams to an angle of 11.88° in total.

1 INTRODUCTION TO TERAHERTZ SPECTROSCOPY 1
1.1 Instrumentations in THz Spectroscopy Measurements 1
1.1.1 THz-TDS System 2
1.1.2 THz-FDS System 2
1.2 Advantages over Other Spectroscopy Techniques 3
1.3 Limitations of Terahertz Spectroscopy 4
1.4 Applications of Terahertz spectroscopy 5
1.5 Terahertz Imaging Systems 6
1.5.1 THz-TDS Imaging system 6
1.5.2 THz-FDS Imaging System 7
1.6 Motivation 8
1.7 Outline 11
2 TUNABLE FISHNET GRADIENT METAMATERIAL (TGFM) 12
2.1 Introduction to Metamaterials 12
2.2 Fishnet Metamaterial 14
2.2.1 Effective LC Circuit Description of the Fishnet Structure 16
2.2.2 Changing the Geometry and Topology 17
2.3 Tunable Fishnet Metamaterial (TFM) 20
2.4 Tunable Gradient Fishnet Metamaterial (TGFM) 23
2.5 Phase Modulation using Phased Array 24
3 DESIGN AND FABRICATION OF THE TGFM 27
3.1 Improvements on the TGFM Design 27
3.2 Designing the TGFM 28
3.2.1 Increment of Unit-cell Size 29
3.2.2 Changing the TGFM Design 31
3.3 Verification of TGFM Based Wave Manipulation 33
3.4 Fabrication of TGFM 36
3.4.1 Substrate Selection 36
3.5 Determination of Operational Voltage and Frequency 39
3.5.1 Locating Resonant Dips in S21 Spectrum 41
3.5.2 Determination of Operational Voltage and Frequency Range 43
3.5.3 S21 Phase Spectrum 46
4 EXPERIMENTAL RESULTS: TGFM PROPERTIES 49
4.1 Material Properties of the TGFM 49
4.1.1 Setup for retrieving Transmission Spectrum 49
4.1.2 Calculation of Material Properties using Transmission Spectrum 50
4.1.3 Setup for Retrieving Reflection Spectrum 52
4.1.4 Calculation of Material Properties using Reflection Spectrum 53
4.2 Beam Deflection Angle due to Gradient Index 55
4.2.1 Setup for 1-D Scanning 55
4.2.2 Beam Profiles with Linear Voltage Distribution 58
4.2.3 Voltage Tunable Deflection Angle: Linear Phase Distribution 69
4.3 Acquiring Images using the Beam Profiles 74
4.3.1 Image Acquisition of a Metal Strip Placed at x = 0 mm Position 75
4.3.2 Image Acquisition of Two Metal Strips 77
4.4 2-D Pulse TDS System Setup 80
5 CONCLUSION AND FUTURE WORK 82
5.1 Conclusion 82
5.2 Future Considerations 82

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