- 學位論文
D型多模光纖感測器與ATR稜鏡感測器對液體折射率量測之研究
Liquid refractive index measurements by uses of D-type multi-mode fiber sensors and the ATR prism type sensor
摘要
本篇論文分別利用光纖感測器及稜鏡感測器兩種不同方法，對於不同折射率的待測液體做量測。 1. 為了要提高D型光纖對於待測物折射率的靈敏度與解析度，本研究D型多模光纖感測器將利用光譜分析（optical spectrum analyzer）的方法與衰減全反射（attenuated total reflection, ATR）及表面電漿共振(surface plasmon resonance, SPR)原理來作研究。 將金膜的鍍膜厚度從20~50nm做改變，不同金膜厚度的情況下，可以觀察出當待測液體折射率改變時，所量測到光強度比值最低點所對應的漸逝波長也會隨著偏移。而波長最小解析度為0.01nm，在待測折射率 1.33~1.47的範圍內，解析度最佳可達5.2×10-7 (RIU)。 2. 有別於一般的SPR稜鏡感測器，本研究提出一種新型的S偏極ATR稜鏡感測器，針對液體折射率量測做強度法模擬分析與實驗。模擬結果可得到最佳鍍膜厚度參數，並可得知對於不同折射率的待測液體，其共振角的角度範圍並與SPR感測器做相互比較。 模擬結果顯示，利用S偏極ATR稜鏡感測器，在待測液體折射率n= 1.33~1.47的範圍中，其解析度可以比SPR感測器更加穩定，而其最佳解析度可達1.89×10-6 (RIU)，同時其共振角的半高寬比SPR稜鏡感測器來的窄，結果顯示出S偏極光一樣可做為量測之用。
並列摘要
In this study, we propsed two methods for liquid refractive index measurements by uses of D-type multi-mode fiber sensors and the ATR prsim type sensor. 1. A multi-mode D-type optical fiber sensor based on the surface plasmon resonance(SPR), attenuated total reflection(ATR) and using optical spectrum analyzer method is presented. It is coated with an Au-film layer with a thickness of 20~50nm to detect the refractive variation of a liquid by measuring the output spectrum. Calculation of the reflectance ratio of the specimen, compared to water, enables determination of the resonant wavelength and the refractive index. The proposed method is used to enhance the measurement sensitivity and achieve a resolution to 5.2×10-7(RIU). 2 Being different with the usual SPR prism type sensor, a novel measurement system based on attenuated total reflection(ATR) with S polarization was built up in our Lab. For measuring the liquid refractive index, we used five-layers ATR sensors to simulate its attenuated angles corresponding different refractive index liquid and the best coating thickness. Comparing the resoulation between S- and P-polarizations, the S-polarized ATR sensor is better than the P-polarized SPR sensor, and the resoulation can achieve to 1.89×10-6 (RIU). The results exhibits that is feasibility to use S-polarization for measurement.