利用阿基米德螺旋達成選擇性表面電漿光鉗與光轉子之探討

Selective Optical Trapping/Rotation Using Plasmonic Archimedes Spiral

蔡瑋義

指導教授 ： 黃承彬

國立清華大學/電機資訊學院/光電工程研究所/碩士(2013年)

摘要

在本論文之第一部份，利用有限元素法分析阿基米德螺旋結構所激發的表面電漿子產生超聚焦現象與光漩渦現象，探討這兩種表面電漿子現象對於捕捉與旋轉微小粒子的可行性。產生這些現象有兩個主要因素，一為電漿子螺旋元件的幾何結構，另一個為激發此元件光源的圓偏振態旋向。表面電漿子能將區域內光場增強以及將光場侷限在次波長尺度內，此兩特性與傳統光學鑷子使用聚焦的雷射光捕捉微小粒子並加以操縱的概念雷同，因此利用傳統光學鑷子的原理去分析阿基米德螺旋結構。

本論文之第二部分，我們於實驗上，利用熱蒸鍍的方式鍍製金屬薄膜，再以聚焦離子研磨出阿基米德螺旋微結構於蓋玻片基底上。實驗量測方面利用商用光學顯微鏡搭配自行架設的激發樣品之光路，並使用CCD觀測微小粒子是否受到光漩渦與超聚焦的效應，因而產生被捕捉與旋轉的現象，最後將CCD所取得的影像結果與模擬數據做比較。實驗所得到的結果與模擬的結果相似，從而可證實電漿子螺旋元件的光聚焦現象與光漩渦現象的正確性。

關鍵字

光學鑷子 ； 表面電漿捕捉

並列摘要

In the first part of this work, we use finite element method to simulate the optical vortex and super-focus phenomenon within an Archimedes spiral. There are two main factors that influence these phenomena: One is the geometrical charge determined by the geometry of plasmonic spiral device, the other is the spin angular momentum of the incident plane wave. We analyze the two kinds of surface plasmonic phenomenon for trapping particle and rotating particle. Traditionally, optical tweezer use focused laser beam to trap particle and manipulate. Plasmonic can enhance and localize light field which is similar to optical tweezers principle. Therefore, we use that concept to analyze Archimedes spiral structure.
In the secondary part of this work, our samples are fabricated using thermal evaporation to deposit a 200 nm film over a glass substrate. Then we make micro structure of plasmonic spiral device by using focused ion beam (FIB). In the experimental process, we use optical microscope system with a CCD (charge-coupled device) to observe the motion of micro-particles. Finally, we compare video result with simulation result. The simulation result is matching the experimental result which we observe.

並列關鍵字

optical tweezers ； plasmonic trapping

參考文獻

[14] S.A.Maier, Plasmonics: Fundamentals and Application(Springer-verlag,20007)

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