生醫光電是一成長迅速的研究領域，而且已成為生物科技重點發展項目之一。近年來，研究人員提出將微環形諧振器(Microring Resonator；MRR)用於無標記生物感測應用，由環內強電場增強引起的高品質因子(Q)使得MRR成為有效地分析檢測生物分子之微小濃度引起折射率變化檢測的良好候選者。本論文提出利用微環形諧振器之元件特性，結合低同調干涉技術及Delayed Self-Homodyne方法來研製高靈敏生醫感測器。
在本論文中，我們運用光纖通訊波段之寬頻譜光源及Mach-Zehnder干涉儀作為實驗架構主體，量測系統分為兩個部分，低同調干涉系統及線寬量測系統。低同調干涉系統是以Mach-Zehnder干涉儀及低同調光源作為此系統的主要架構，並結合微環形諧振器的環降(Ringdown)現象，來達到醫學感測的目的。在數據處理上，使用Matlab將環降現象的干涉波包以高斯曲線擬和(Gaussian Curve Fitting)的方式分析不同濃度待測物各階波包之間的位移，靈敏度約為10.21μm⁄μM。
線寬量測系統為運用Delayed Self-Homodyne方法與高解析度頻譜分析儀(Electrical Spectrum Analyzer, ESA)來替代波長分析儀(Optical Spectrum Analyzer, OSA)。藉由Fiber Bragg Grating濾波特性，結合隨折射率變化產生偏移的微環形諧振器共振波長，來進行感測。Delayed Self-Homodyne方法的架構為Mach-Zehnder干涉儀，利用補償光纖的方式使兩路光程差遠大於輸入光源的同調長度，使Mach-Zehnder干涉儀的兩路光變的互不相干，利用Coupler再將兩路光源合併，兩路光的交集處經由ESA顯示出來，在數據分析上以此交集處線寬的變化與不同濃度待測物的變化加以比較，此感測器的靈敏度約為0.00191nm/(mg/ml)。

Biophotonics is a rapidly growing field in prevailing researches and becomes one of the major developed projects of biomedical technologies. In recent years, the microring resonator (MRR) has been utilized for label-free biosensing applications. The high quality factor (Q) from the strong electric field enhancement within the ring makes the MRR a good candidate for biomolecule detection under low analyte concentration conditions. Here we propose to develop high sensitivity biosensors using MRR characteristics interrogated with the low coherent interference technique and delayed Self-Homodyne method.
In this thesis, the main experimental structure consists of the Mach-Zehnder interferometer and broad band source in the optical fiber communication wavelength range. The characterization is divided into two parts - the low coherence interferograms and linewidth measurement. The optical low coherence interferometry (OLCI) is composed of the Mach-Zehnder structure and low coherence light source, and its interferogram Ringdown from the MRR could be utilized for biosensing applications. The interferogram Ringdown could be analyzed to detect the spatial shifting between different orders and various analyte concentrations using Gaussian curve fitting. The sensitivity can demonstrate 10.21μm⁄μM.
The linewidth measurement uses the electrical spectrum analyzer (ESA) for a higher frequency resolution from the delayed Self-Homodyne compared with the optical spectrum analyzer (OSA). The sensing is performed by the linewidth change with ambient refractive index variation through the cascaded wave from the fiber Bragg grating and MRR. The delayed Self-Homodyne method is to intentionally make two Mach-Zehnder optical path difference larger than the input light coherence for two output incoherent waves and then followed by photodetector and ESA. The linewidth variations at various analyte concentrations demonstrate the sensitivity as 0.00191nm/(mg/ml).

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