本論文設計一方向耦合結構的電漿子開關，其光訊號在電漿子(Plasmonic)波導與矽(Si)光波導之間進行轉換，電漿子開關元件特性包括傳播長度(Propagation Length)、操作電壓(Operated Voltage)、透射率(Transmittance)、插入損耗(Insertion Loss)、隔離度(Isolation)、消光比(Extinction Ratio)，透過改變材料與設計最佳化結構尺寸來優化這些參數。
本論文以謝政宏學長於2015年在IEEE發表的方向耦合結構電漿子開關為基礎，提出材料變換，首先改變電漿子波導的介電質材料，將對甲苯磺酸鹽(DAST)改變為二氧化釩(VO2)，可以直接搭配矽光波導達到相位匹配的效果，藉由二氧化釩在外加電壓後會產生相變的物理機制，可以控制此元件的開與關。本文透過研究傳播長度與操作電壓的變化趨勢，分析出最佳化的二氧化釩與銀(Ag)厚度，接著透過相位匹配分析，找出對應的兩波導寬度，最後透過插入損耗與隔離度的變化趨勢，分析出最佳化的耦合長度，經過以上模擬結果，可以分析出最佳化的結構尺寸。
本論文透過改變材料與設計最佳化結構尺寸後，大幅度地提升電漿子開關的效能表現，關與開狀態的透射率分別維持在55 %與60 %，所佔面積從原本的29.4 µm大幅縮減到2.05 µm，操作電壓從22.5 V降低到9.65 V，隔離度從10 dB提升到14 dB，消光比從10 dB提升到41 dB，改善超過3個數量級。

This paper design and analyze a directional coupler structure based plasmonic switch. The optical signal is converted between the plasmonic waveguide and the silicon optical waveguide. The characteristics of the plasmonic switch including propagation length, operated voltage, transmittance, insertion loss, isolation and extinction ratio. Through changing material and designing optimized structural dimensions to optimize above characteristics.
On the basis of directional coupler structure based plasmonic switch of Cheng-Hung Hsieh’s IEEE paper . This paper attempts to change the material. First, change the dielectric material of the plasmonic waveguide, DAST to vanadium dioxide(VO2).After the voltage is applied on the vanadium dioxide, vanadium dioxide’s phase will change. This physical mechanism can control the on and off state. In this paper, through studying the variation trend of propagation length and operated voltage to analysis the optimized thickness of vanadium dioxide and silver. Then, through phase matching to find the corresponding two waveguide widths. Finally, through studying the variation trend of insertion loss and isolation to analysis the optimized parallel length. After the above simulation results, the optimized structural dimensions can be designed.
After changing the material and designing optimized structural dimensions, the paper greatly improved the performance of the plasmonic switch. The transmittances of the off and on states are maintained at 55 % and 60 %, respectively. The footprint was greatly reduced from the original 29.4 μm to 2.05 μm. The operated voltage is reduced from 22.5 V to 9.65 V. The isolation is increased from 10 dB to 14 dB, and the extinction ratio is increased from 10 dB to 41 dB, improving by more than 3 orders of magnitude.

摘要 i
目錄 iii
圖目錄 vi
表目錄 x
第一章 背景與動機 1
1.1 研究背景 1
1.2 研究動機 2
1.3 文獻回顧 3
1.3.1 T形狀的金屬-介電質-金屬結構 3
1.3.2 齒形狀的金屬-絕緣體-金屬結構 5
1.3.3 垂直耦合結構 7
1.3.4 介電質負載電漿子波導結構 9
1.3.5 Mach-Zehnder干涉儀結構 11
1.3.6 方向耦合結構的電光調變器 14
1.3.7 傳統方向耦合(雙波導)結構 17
1.3.8 方向耦合(雙波導)結構 19
1.3.9 方向耦合(三波導)結構 22
第二章 基礎理論 26
2.1 德汝德模型(Drude Model) 26
2.2 電磁波的色散關係式(dispersion relation) 28
2.3 金屬-介電質間的表面電漿子模式 29
第三章 研究方法 34
3.1 模擬軟體介紹 34
3.2 網格的設定 35
3.3 重要參數的計算 38
3.3.1 等效折射係數(Effective mode index) 38
3.3.2 傳播長度(propagation length) 39
3.3.3 能量密度(Power density) 39
3.3.4 透射率(Transmittance: T) 40
3.3.5 插入損耗(Insertion Loss: IL) 40
3.3.6 隔離度(Isolation: I) 40
3.3.7 消光比(Extinction Ratio: ER) 40
第四章 電漿子開關模擬結果與討論 41
4.1 電漿子波導-金屬置頂之介電質負載表面電漿子波導管 42
4.1.1 二維波導管模態分析與K參數計算 42
4.1.2 模擬不同波導管寬度對傳播長度的影響 44
4.1.3 模擬不同銀金屬厚度對傳播長度的影響 46
4.1.4 模擬不同二氧化釩厚度對傳播長度的影響 48
4.2 主要波導-矽波導管 50
4.3 主要波導與電漿子波導之相位匹配分析 51
4.4 主要波導與電漿子波導的耦合長度 52
4.5 開與關之間的消光比 55
4.6 模擬不同波導間隙對耦合長度的影響 55
4.7 模擬不同操作電壓對電漿子開關的影響 58
4.7.1 操作電壓在9.65 V的效能表現 59
4.7.2 操作電壓在13 V的效能表現 62
4.7.3 操作電壓在19.5 V的效能表現 64
4.7.4 操作電壓在26 V的效能表現 67
4.7.5 四種不同操作電壓的總結 69
第五章 結論 70
附錄A 模擬不同等效折射係數對電漿子開關的影響 71
A.1等效折射係數為2.79的效能表現 71
A.2等效折射係數為3.24的效能表現 74
A.3不同等效折射係數的總結 76
參考文獻 77

[1] 吳民耀、劉威志, "表面電漿子理論與模擬," 物理雙月刊(二十八捲二期), 2006.
[2] H.A.Atwater, A. Polman, and N. Mater, "Plasmonics for improved photovoltaic devices," Nature Materials, vol. 9, pp. 205-213, OCT 2010.
[3] H. A. Atwater, "The promise of plasmonics," Scientific American, vol. 296, pp. 56-62, APR 2007.
[4] J. K. Y. J. Lu, H. Y. Chen, C. H. Wu, N. Dabidian, and C. E. Sanders, "Plasmonic nanolaser using epitaxially grown silver film," Science, vol. 337, pp. 450-453, JUL 2012.
[5] 郭建銘, "效能增強混合式表面電漿子波導管之設計與分析," 碩士, 工程與系統科學, 國立清華大學, 新竹市, 2015.
[6] H.-S. Chu, E.-P. Li, P. Bai, and R. Hegde, "Optical performance of single-mode hybrid dielectric-loaded plasmonic waveguide-based components," Applied Physics Letters, vol. 96, p. 221103, 2010.
[7] J. W. Wang, X. W. Guan, Y. R. He, Y. C. Shi, Z. C. Wang, and S.L.He, "Sub-mum power splitters by using silicon hybrid plasmonic waveguides," Optics Express, vol. 19, pp. 838-847, JAN 2011.
[8] A. Emboras, C. Hoessbacher, and C. Haffner, "Electrically controlled plasmonic switches and modulators," IEEE, VOL. 21, p. 4, AUG 2015.
[9] X. Mei, X. G. Huang, and T. Jin, "A sub-wavelength electro-optic switch based on plasmonic T-shaped waveguide," Plasmonic, v. 6,pp. 613-618, DEC 2011.
[10] A. N. Taheri and H. Kaatuzian, "Design and simulation of a nanoscale electroplasmonic 1 × 2 switch based on asymmetric metal–insulator–metal stub filters," Applied Optics, Vol. 53, pp. 6546-6553, 2011.
[11] D. C. Zografopoulos and R. Beccherelli, "Design of a vertically coupled liquid-crystal long-range plasmonic optical switch," Appl. Phys. vol. 102, p. 101103, 2013.
[12] A. V. Krasavin, S. Randhawa, and J.-S. Bouillard, "Optically-programmable nonlinear photonic component for dielectric-loaded plasmonic circuitry," Optics Express, vol. 19, pp. 25222-25229, 2011.
[13] A. Arya and R. Manivasakann, A compact and high-speed plasmonic slot waveguide coupled with photonic waveguide based 22 electro-optic switch vol. SPIE OPTO, vol. 9750, p. 97501, 2016.
[14] J.-S. Kim and J. T. Kim, "Silicon electro-optic modulator based on an ITO-integrated tunable directional coupler," Applied Physics, vol. 49, pp. 075101-075106, 2016.
[15] B. Janjan, V. Ahmadi, and D. Fathi, "7μm-long all-optical 1x2 switch utilizing Si/VO2 hybrid waveguide," Iranian conference on electrical engineering, 2017.
[16] C.-H. Hsieh, K.-P. Lin, and K.-C. Leou, "Design of a compact high-performance electro-optic plasmonic switch," IEEE Photonics Technology Letters, vol. 27, p. 23, 2015.
[17] C. Ye, K. Liu, R. A. Soref, and V. J.Sorger, "A compact plasmonic MOS-based 2x2 electro-optic switch," Nanophotonics, 2015.