表面電漿共振 (surface plasmon resonance，SPR) 的模態及共振角度對於奈米金屬膜層厚度與環境的折射率之微量變化下，具有高靈敏度與高準確性的優點。由於表面電漿共振模態僅存在於TM極化的入射電磁波，當耦合菱鏡介質的折射率與金屬膜介面之表面電漿共振角度條件匹配時，入射光將可幾乎全部耦合成表面波，理想上此時入射光將接近零。金屬上介面之介質層折射率改變對表面電漿共振的影響為本論文的主軸，可藉由折射率的變化，調控表面電漿共振角度(θSPR)或共振波長。
藉由在菱鏡邊界鍍上50 nm厚的金膜，並於結構中加入具有折射率異向性之液晶材料，製作出可調控之克萊舒曼 (Kretschmann) 結構。當液晶分子的排列改變時，折射率也隨之變化，藉此調控表面電漿的共振角度。我們在液晶材料中摻雜少量光敏感之偶氮染料(azo-dye)，使液晶具有光調控之特性。本研究探討了不同種類的向列型液晶與不同濃度的光引致染料分子之混合物，並藉由兩種機制改變折射率來調制表面電漿共振角度的方式：第一種為光配向的方式，使用偏振光來調控甲基紅 (Methyl Red) 染料分子的排列方向，改變液晶的排列，使原本折射率n_o轉變成n_eff，但由於偶氮染料吸附效應的光配向機制，會導致重複切換的困難。第二種為利用具有光致同素異構化反應的偶氮染料4MAB及偶氮苯 (azobenzene)液晶1205，照光使液晶相變點降低，液晶分子排列混亂，折射率可由n_o與n_iso之間做調變。但4MAB的比例會影響液晶雙折射性，造成共振角度的位移量降低，而1205為具有折射異向性的染料分子，摻雜的比例對其雙折射性的影響相對較低。
　　利用各種不同的向列型液晶及不同濃度的染料分子，在不同的機制下，改變折射率對共振角位移量的結果，發現當使用純1205時，得到最大光控調變共振角位移量為2.31°及理論上共振波長的變化量為49 nm(633 nm → 682 nm)，並且偶氮苯液晶也具有雙穩態特性及快速調變之優點，可應用於光調制器與光學濾波器。

Surface plasmon resonance (SPR) is very sensitive to the refractive index of the layer on top of its metal surface. Only TM polarized light can excite surface plasmon mode. The resonance angle of surface plasmon polariton (SPP) is very strict and only when the k-vector of incident light matches the k-vector of SPP mode can SPP waves be excited. With measurements of the coupling angle of SPP wave, we can measure very slight refractive index change on top of the metal film.
A 50 nm thin Au film was evaporated on the flat surface of the prism which is suitable for Kretschmann geometry experiment. On top of Au film we put a liquid crystal (LC) layer. When the orientation of liquid crystal changes, the refractive index on the Au surface also change, which can modulate the resonance angle of SPR. In the reserch, a little azo-dye was doped in liquid crystal material to be photo-tunable. This study explored the mixture of various nematic liquid crystal and different photo-induced dye concentrates. We used two methods of changing the refractive index to modulate the resonance angle of SPR. The first one was to add a photo alignment layer. The polarization of pumping light affects the orientation of Methyl Red molecules and then the material changes the orientation of liquid crystal molecules which make the refractive index n_o into n_eff. Due to the attachment effect of Methyl Red on the Au surface, it is difficult to repeat the LC rotation. The second method was to use 4MAB and azobenzene liquid crystal 1205 with photoisomerization. Pumping light made the clear point of LC lower and the liquid crystal alignment became random. The refractive index could be adjusted between n_o and n_iso. However, the concentration of 4MAB would influence the birefringence of liquid crystal. It lowered the difference between the two resonance angles. In contrast, 1205 has refractive anisotropy, and the smear-out effect on the LC refractive index is cleared out.
By using different nematic liquid crystals and different concentrations of azo molecules, we found that when pure 1205 was used, the max displacement of resonance angle was 2.31° and the variation of wavelength was 49nm (633 nm → 682 nm) in terms of photo modulate. In addition, azobezene liquid crystal also had the advantage of bistable and fast switch, which could be applied to optical modulations and optical filter design.

誌謝 iii
摘要 iv
Abstract vi
目錄 viii
表目錄 xi
圖目錄 xii
第一章 緒論 1
1.1 前言 1
1.2 研究目的 2
1.3 文獻回顧 3
1.4 論文架構 4
第二章 研究理論 6
2.1 衰逝全反射 6
2.2 表面電漿波 7
2.2.1 表面電漿共振模態 8
2.2.2 表面電漿共振激發架構 17
2.2.3 三層結構反射率之理論 21
2.3 Kretschmann 組態之SPR模擬 25
2.3.1 有限元素法簡介 27
2.3.2 不同金膜厚度下之SPR模態 30
2.3.3 不同介質折射率下之SPR模態 31
2.4 液晶的簡介 33
2.5 液晶的物理特性 35
2.5.1 秩序參數 35
2.5.2 折射率異向性 36
2.6 光引致染料分子 40
第三章 實驗方法與步驟 42
3.1 樣品備製 42
3.1.1 Kretschmann架構製作 42
3.1.2 向列型液晶 46
3.1.3 光引致染料 48
3.1.4 藥品調製 50
3.1.5 液晶盒製作 51
3.2 SPR量測架構及方法 52
3.2.1 照光對穿透度影響之量測 52
3.2.2 SPR量測 53
第四章 結果與討論 56
4.1 金膜在不同介質下之SPR模態 56
4.2 液晶混合不同光引致染料分子下之SPR模態 57
4.2.1 E7+Methyl Red之SPR膜態 58
4.2.2 E7+4MAB之SPR膜態 59
4.2.3 BL006+4MAB之SPR膜態 61
4.2.4 BL006+5CB+4MAB之SPR膜態 63
4.2.5 BL006+1205之SPR膜態 66
4.2.6 1205之SPR膜態 68
第五章 總結與未來展望 71
參考文獻 73

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