表面電漿共振(Suface Plasmon Resonance, SPR) 是利用光的全反射。若在反射面附近有金屬層，光全反射時的漸逝波會引發金屬層上電子的集體共振，造成反射光發生劇烈的衰減。此衰減信號的特性與反射面附近的環境大有關係，我們就可利用此種特性來檢測或監控待測物。由於光束的電子振盪與金屬薄膜內金屬原子產生共振作用時，常見的表面電漿共振量測方式有四種，角度調制、波長調制、強度調制與相位調制，其中又以相位調制之靈敏度為最高，因為在特定角度或特定波長相位的變化量是非常劇烈的，當待測物折射率不同時其相位變化是所有量測方法中最顯著的。
本論文提出以低同調干涉結合表面電漿共振以相位量測的方式提高靈敏度，由於SPR對於極化非常敏感只對TM偏振光有反應，因此量測系統的光纖全部改用極化保持光纖加強系統穩定性，並提高步進馬達解析度為7.56-nm/step，增加SPR解析度。
比較串聯與並聯兩者不同低同調干涉量測系統應用於SPR的差異，串聯低同調干涉系統量測microRNA-21靈敏度為0.479 μm/μM，由本實驗室使用之步進馬達7.56-nm/step推算解析度為1.58×〖10〗^(-2) μM，而並聯低同調干涉實驗誤差較大，需要更為穩定的系統，因此這部分以探討系統誤差、分析原因以及如何改善為主。

Surface plasmon resonance (SPR) can be excited by total internal reflection on a metal layer near reflective surface. The evanescent wave will then form a collective resonance of the electrons on the metal layer and illustrate a sharp attenuation of the reflect light at the resonant angle, which is easily influenced by the environmental variation and utilized in biological detection. There are four kinds of SPR characteristics: angle, wavelength, intensity and phase modulation. Among them, the phase modulation demonstrates the highest sensitivity became the phase change amount from different refractive index of the device under test (DUT) at a specific angle or a specific wavelength is very sharp and deep.
In this thesis, a novel approach to improve SPR spatial phase biosensing is demonstrated. Because SPR is very sensitive to polarization and only occurs in transverse magnetic (TM) polarized light, all the optical fibers in the measurement system are converted to the polarization-maintaining optical fiber to enhance the testing stability. Furthermore, the stepper motor resolution is increased up to 7.56-nm/step to increase SPR resolution.
The SPR and optical fiber low coherence interferometry (OFLCI) are interrogated to improve the sensitivity and two different approaches from serial and parallel structures are compared for characterization consistency. The sensitivity of microRNA from two staged serial OFLCI system experimentally demonstrates 0.479 μm/μM. Its theoretical resolution is estimated to be 1.58×〖10〗^(-2) μM after the 7.56-nm/step stepper motor is used. And the parallel OFLCI based SPR is not stable in the interferogram from low coherent source interfered with laser. The systematic errors will then be analyzed and discussed.

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