圓偏光表面電漿子干涉儀之研製

Design & Construction of Circular Polarization Interferometer via Surface Plasmon Resonance

詹家銘(Chia-Ming Jan)

指導教授 ： 李世光

共同指導教授 ： 吳光鐘

國立臺灣大學/工學院/應用力學研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.01893

摘要

本研究為改良圓偏光干涉儀(Circular Polarization Interferometer)—以一組正交偏振光—TE和TM偏振光，經過四分之一波板形成左旋圓偏光和右旋圓偏光，利用兩偏極分光鏡於空間中相位差45°，使得輸出訊號產生相差90°之干涉，再以差動方式將正交方向之光強值相減取其正切函數，解出樣本相位資訊。圓偏光干涉術不但可以消除傳統干涉儀因無法調制等量入射光強所造成的直流項，並且避免高頻電子訊號干擾，大幅縮小系統體積。同時，本系統引入雙模態偏振光共光程概念(P-S common beam)，使TE光和TM光於系統內無光程差，如此干涉後兩道光之相差，僅為樣本所造成，在相位比較方面不需以已知樣本校正量測值，可減少實驗調校步驟，提升系統解析能力。
感測晶片之設計係利用表面電漿共振術(Surface Plasmon Resonance, SPR)，表面電漿波是一種存在於金屬與介電層之間，在邊界上引發量子震盪之電荷密度分佈所形成的波傳現象。當光從介電質材料入射至金屬表面時，於符合共振角條件下，在垂直界面處會形成一漸逝場，並向兩邊介質呈指數性衰減，即為表面電漿共振發生。此時，僅TM偏振反射光之光強與相位會有明顯變化而TE偏振光之表面電漿共振效應則可以忽略。本系統利用不同偏振態其共振效應之差異，由電磁理論吾人可推導出介電常數與光強、相位及角度之關係，以角度調制法和相位調制法擷取SPR反應訊號。目前這類技術已大量使用於量測薄膜厚度變化、氣體或液體的折射率改變及生化反應所造成光學性質改變。
本研究延續團隊之OBMorph光生化檢測儀開發經驗，以拋物面反射鏡與球面反射鏡之變角度入射子系統為基礎，配合圓偏光相移干涉架構之解相位方式，建立一體積小、成本低且具有大動態量測範圍之角度調制式與高解析度相位調制式圓偏光干涉儀系統。同時，藉由量測兩正交訊號的方式，成功地利用映射呂薩加圓修正光強量測值以驗證圓偏光干涉儀架構。於實驗中，以不同濃度之葡萄糖(glucose)進行折射率與相位關係的量測，經實驗結果分析，葡萄糖濃度與折射率之間在小範圍量測時會呈正比關係，而在表面電漿共振角附近入射時，相位變化與折射率之間會有接近線性關係，初步得到量測系統具有折射率變化小數點下四位之解析度。此外，本研究以不同濃度之C型反應蛋白(CRP，C-reactive protein)與Anti-CRP進行專一性測定，得到不同濃度CRP與anti-CRP鍵結時對應相位變化關係，驗證本系統於生物量測定性定量的能力。在動態量測方面，本研究以不同濃度之人類免疫球蛋白，IgG與Anti-IgG，進行抗體抗原鍵結反應，在標準流程操作下，成功地證明本系統具有生物分子反應試驗(BIA，Biomolecule Interaction Assay)能力。

關鍵字

表面電漿共振 ； 圓偏光干涉 ； 相位調制 ； C—反應蛋白

並列摘要

Circular polarization interferometer detets phase difference by means of utilizing one set of circular polarization beams to produce a 90°output phase delay. When TE wave and TM wave passed a quarter wavelength-plate, we used two polarization beasm spitters, and hope to bring ninty degree phase difference for output signals. Then we can directly calculate the phase difference from function of arctangent of the two orthogonal differential signals. Under the scheme of circular polarization interferometry, we can prevent interruption from high frequency electronic noise, and reduce system volume. Moreover, it can cancel out the DC term of interference fringes which cause low visibility. Furthermore, we recommend a full new scheme for interferometry — P-S common beams— to let the path difference between TE & TM waves be equal. It is powfully benefit for resolution of optomechnism.
Surface plasmon wave which can be excited between metal and dielectric layers is a wave propagation phenomena caused by the charge density of quantum resonance on the boundary. There is an evanescent field forming on surface plasmon angle while light beam impinges onto the interface. The electric field decays toward both side of the interface exponentially. The phase and intensity of TM reflective wave would change significantly at this moment. Beginning with the basis of electromagnetic theorem, the relationship between intensity, incident anlge, phase of TM reflective wave and dielectric constant could be derived. However, surface plasma resonance does not affect TE wave. We can obtain the light intensity, phase, resonance angle, and resonance wavelength in accordance with different effluence affected for TE & TM wave. These well developed interrogation techniques have been widely applied in measuring the thickness variation of thin film, the reflective indeices change of liquid or gas samples and the biomolecular interaction.
During the course of this study, we extended our research team’s many years optical system design experience and employed a paraboloidal mirror, a spherical mirror, and a precision servomotor control on circular polarization interferometer. We successfully develope a small volume, low cost, phase and angle interrogation circular polarization interferometer with wide range of dynamic measurement. Using Lissajous curve from two orthogonal signals, we could modify metered intensity. After measuring various concentrations of glucose standard solutions (100 mg/dL ~ 20000 mg/dL), the system has been proved to have 10-4 resolution in measuring reflective indices. By the assay of different concentrations of anti-CRP and CRP, the study verifies the system has the ability of biomolecule specific interaction detection which is even better than angular interrogation SPR instrument. The success of the IgG and anti-IgG for antigen-antibody combination proves the capability of BIA experiment of the system for biomedical detection.

並列關鍵字

surface plasmon resonance ； circular polarization interferometry ； phase-interrogation ； CRP

參考文獻

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