近期在奈米光學元件方面的進展，尤其是表面電漿子相關的元件，已經在全光信號處理領域取得了顯著的進步，超越了傳統基於晶體管的電子學的物理限制。這些進展允許在超越繞射極限的情況下實現嚴格的空間限制，為多功能光子奈米電路的發展鋪平了道路。本研究展示了在電漿子雙線傳輸線裝置中數位集成電路的實驗實現，突顯了從串聯閘操作到組合電路中純平行操作的轉變。具體來說，展示了幾種算術電路的實現，僅需要使用單一激光束的四種預定義偏振態來完成所有的邏輯/算術操作。這些裝置展現了令人印象深刻的性能，運作於超過12.5 THz的光帶寬，因此提供了一種朝向整合在晶片上的光子處理器發展的可行方法。
此外，過渡金屬硫族化合物（TMDs），特別是MoSe2，整合到電漿子奈米電路中，解決了與非線性奈米光子電路普遍相關的低非線性轉換效率的挑戰。這種整合顯著增強了二倍頻訊號，與原始非線性電漿電路相比，二倍頻訊號增加了13.8倍。通過調整輸入光的偏振角度，能夠實現電漿子電路二倍頻訊號的選擇性路由，其消光比達到14.86 dB，從而維持了良好的相干性。這些進展，以高效的二倍頻訊號生成、耦合和可控路由為特點，這種混合電漿子電路有希望推進在晶片上的光頻率轉換、選擇性路由、開關、邏輯操作，甚至可能的量子操作等領域的即時應用。

Recent advancements in photonic devices, particularly those utilizing surface plasmons, have marked a significant step forward in all-optical signal processing, transcending the physical constraints of traditional transistor-based electronics. These advancements allow for tight spatial confinement beyond the diffraction limit, paving the way for multifunctional photonic nanocircuitry. This research showcases the experimental realization of Digital Integrated Circuits in plasmonic two-wire transmission-line devices, highlighting a shift from serial gate operations to pure parallel operations in combinational circuits. Specifically, the implementation of several arithmetic circuits is demonstrated, requiring only four predefined polarizations of a single laser beam for all logic/arithmetic operations. These devices exhibit impressive performance, operating at over 12.5 THz optical bandwidth, thus offering a viable approach towards the development of integrated on-chip photonics processors.
Furthermore, the integration of transition metal dichalcogenides (TMDs), particularly MoSe2, onto plasmonic nanocircuitry, addresses the challenge of low nonlinear conversion efficiency commonly associated with nonlinear nanophotonic circuits. This integration significantly enhances second-harmonic generation (SHG) signals, achieving a 13.8-fold increase in SHG compared to the pristine nonlinear plasmonic circuits. By adjusting the input laser's polarization angle, selective routing of SHG signals within the plasmonic circuit is achieved, with routing extinction ratios reaching 14.86 dB, thereby maintaining good coherence. These advancements, characterized by efficient SHG generation, coupling, and controllable routing, position this hybrid TMD-plasmonic nanocircuitry as a promising candidate for immediate applications in areas such as on-chip optical frequency conversion, selective routing, switching, logic operations, and potentially quantum operations.

Chapter 1 Surface Plasmon Polaritons 8
1.1. Definition 8
1.2. SPP: length scales 9
1.3. SPP: dispersion relation 9
1.4. SPP: wavelength 11
1.5. SPP: Polariton propagation length 11
1.6. SPP: penetration depth 12
Chapter 2 Digital Logic Design 13
2.1. Boolean Algebra 13
2.2. Arithmetic Operation Circuits 16
Chapter 3 Plasmonic transmission-line-based digital circuits 19
3.1. Motivation 19
3.2. Plasmonic two-wire-transmission-line 20
3.2.1. Plasmonic Wave Guide 20
3.2.2. Mode Profile of TWTL 20
3.2.3. A Polarization-Actuated SPP on TWTL routed 21
3.3. Principle of plasmonic digital logic operations 23
3.4. Plasmonic arithmetic circuits design and experimental results 26
3.4.1. 4 to 2-Encoder 26
3.4.2. OR, XOR, and NOT gates 27
3.4.3. AND gate 28
3.4.4. Half-adder 29
3.4.5. Parallel INHIBIT AND circuit 30
3.4.6. Half-subtractor 32
3.4.7. Demultiplexer 33
3.5. Structure Design 34
3.5.1. Design parameters for the plasmonic TWTL logic gate 34
3.5.2. The design details of AND gate 35
3.5.3. The design details of AND gate in the half-subtractor 36
3.5.4. The in-coupling efficiency and propagation loss 37
Chapter 4 Nonlinear coherent routing and enhancement 39
4.1. Introduction 39
4.2. Polarization dependent properties 40
4.2.1. Mathematical description of SHG from TMD Monolayer 40
4.2.2. Mathematical expressions and polarization characteristics of SPP in TWTL 42
4.2.3. Plasmonic-TMD hybrid system working principle 42
4.3. Coherent control of SHG in plasmonic-TMD hybrid system 44
4.4. SHG enhancement in plasmonic-TMD hybrid system 47
4.5. Analysis of SHG driven sources in plasmonic hybrid systems 50
Chapter 5 Methods 52
5.1. Device Fabrication 52
5.2. Experimental Setup 52
5.2.1. Linear operation 52
5.2.2. Nonlinear operation 52
5.3. Numerical Simulations 53
Chapter 6 Conclusions 54
References 56
Appendix 59

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