臺灣博碩士論文加值系統

折射率的測量在食品安全或是寶石鑑定等方面都是非常重要的。而傳統檢測方法不外乎是測量待測物的Critical angle或 Brewster angle。若要更精確的量測則是利用SPR技術。而本實驗則是利用之前所發展的End-etching method的濕蝕刻方式，將單模光纖進行蝕刻。待蝕刻完成後尖端約成30度角，口徑約為80 nm至100 nm。在之前的實驗已經證明此光纖探針不需在表層鍍上金、銀等金屬來激發表面電漿波。因此不需要繁瑣的微影製程。也不需要在檢測前先將光纖探針表面接上分子，即可進行環境折射率的測量。
而光纖探針的檢測原理是利用針尖的core(RI=1.46)與環境折射率(1.3至1.4)間的差異，導致光在兩介質間傳遞時(光密介質進入光疏介質)，會在針尖部分產生亮點(可視為光被拘束)。當環境折射率越高，被侷限的光點則越矮胖。
當光通過檢測物要進入物鏡時，此時光對low NA值物鏡的收光截面若為正向入射，所收到low angular intensity的光會隨著環境折射率(液體的折射率)增加而上升，光訊號強度也隨之增強。反之若入射光對收光截面有一個角度差時，其收到的光訊號可能多半為high angular intensity，則光訊號強度卻會隨著環境折射率的增加而下降。
光纖探針的靈敏度經測試後可高達8000% RIU，而檢測極限經線性回推結果約為2.5*10−5 RIU。並且這種方法也同時具有動態檢測能力。
本實驗目的在於將光纖探針結合流道，並將收光端以多模光纖取代物鏡，以大幅減少檢測系統體積以及減少訊號的流失。
以蝕刻光纖作為檢測工具除了具有高靈敏度、低環境雜訊以及動態檢測等優點外，也同時具備成本低廉、探針製作簡單與檢測速度快等好處。若能將檢測系統元件化與輕便化，更能提高光纖探針的應用價值。

To measure liquid refractive index is important in applications. The traditional method for the measurement of refractive index (RI) is measuring the critical angle or Brewster’s angle. In this experiment, the tapered fiber sensor adapting “End-etching method” was coated with hot melt glue for chemical etching, the capillary effect to form a sharp tip. The tip size was about 80 to 100 nanometers and with a rough surface when we observed by the SEM.

The tapered fiber is a label-free and metal-free sensor. The test method is optical spot confined in the tip. The spot is found to greatly increase when the environmental RI changes from 1.3 to 1.4. The increase in spot size results in the narrowing of the angular intensity distribution. By using a low NA objective to collect the low angular components, the intensity sensitivity up to 8000%/RIU is achieved. This sensitivity indicates that the fiber tip can detect 2.5*10−5 RIU at 0.2% intensity stability.

The medium affects the guiding properties and thus changes the optical transmission. The experimental results exhibit that the tapered fiber has a larger dynamic range for RI measurement.

In the thesis, these fibers were for 1330 nm wavelength produced by 3M. We designed a method to combine fiber-on-chip for testing liquid refractive indices, to reduce the volume of system and decrease liquid amounts for testing. The liquid flow rates were controlled with syringe pumps. The advantages of tapered fiber systems include small sizes, high sensitivity, dynamic measurement and low cost.

致謝 II
摘要 III
Abstract IV
目錄 V
圖目錄 VII
表目錄 XI
第一章 前言 1
1-1研究動機 1
1-2 蝕刻光纖檢測介紹 2
光纖蝕刻製程: 3
1-3實驗原理 6
1-4蝕刻光纖的優劣所造成之影響 9
1-5 RIU (intensity sensitivity)的計算方式 10
第二章 光纖探針結合流道之實驗架構與數據分析 11
2-1 實驗儀器 12
2-2 實驗架構 14
流道設計 15
2-3 光纖固定在流道的過程 16
光纖固定在流道過程的簡介： 16
2-4靈敏度測試 23
檢測未蝕刻光纖組: 25
平頭光纖組一 25
平頭光纖組二 27
測量蝕刻光纖組: 29
探針間距0.8mm組 29
探針間距1.2mm組 31
探針間距1.3mm組 33
探針間距1.4mm組 35
探針間距1.9mm組 37
2-5 結論: 39
第三章 有機溶液揮發性實驗 41
3-1 實驗架構 42
3-2 測量數據與分析 44
溶液揮發性測量第一組 44
溶液揮發性測量第二組 49
第四章 結論及未來工作 58
4-1實驗總結 58
4-2 未來工作與元件設計 59
參考文獻 60

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