利用電漿子螺旋溝槽產生並塑形近場光漩渦

Generation and shaping of near-field optical vortices using plasmonic spiral and slot

黃偉倫(Wei-Lun Huang)

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(2012年)

https://doi.org/10.6843/NTHU.2012.00098

摘要

本論文利用有限差分時域法模擬表面電漿的光漩渦現象，其中描述光漩渦基本性質的參數為光漩渦的拓樸荷數，其決定在 方位角內電場相位奇異的數量。影響表面電漿光漩渦拓樸荷數有兩個主要因素，一個為決定電漿子螺旋元件幾何結構的幾何荷數，另一個為入射此元件的平面波圓偏振態光內的光子自旋角動量。本論文探討兩者之間的關係，分析空間中表面電漿光漩渦分佈的基本特性。此外，創新的改變電漿子螺旋元件的結構分佈，可以適當的控制近場光漩渦在空間中的強度分佈，且不改變表面電漿光漩渦的拓樸荷數及其本身的性質。
　　實驗上，樣品製作以熱蒸鍍鍍製金屬薄膜至蓋玻片基板，再以聚焦離子束磨銑出電漿子螺旋微結構。近場光學量測方面，本論文利用一自行架設的收集式近場掃描光學顯微鏡，搭配垂直入射激發樣品之光路，以及剪切力回饋的掃描方式量測電漿子螺旋元件產生出表面電漿光漩渦的近場訊號。最後將近場量測數據與模擬數據作比較與分析，得到非常相似的結果證實電漿子螺旋元件設計原理的正確性。

關鍵字

奈米電漿子 ； 表面電漿 ； 光漩渦 ； 阿基米德螺旋 ； 近場量測

並列摘要

In this work, we use finite-difference time-domain method to simulate the optical vortex phenomenon of surface plasmons. An optical vortex is characterized by its topological charge, which denotes the number of phase singularities within a 2 azimuthal rotation. There are two main factors can influence the topological charge of surface plasmon vortex: one is the geometrical charge which can determine the geometry of plasmonic spiral device, another is the spin angular momentum of the photon of the incident circularly polarized plane wave. We analyze the basic property of surface plasmon vortex distributions in space by studying the relationship between these two factors. Furthermore, we change the structure arrangement of plasmonic spiral device in a novel way that can adaptively control the intensity distributions of the surface plasmon vortex in space without changing the topological charge and the basic property of the surface plasmon vortex.
　　In the aspect of sample fabrication, we use thermal evaporation to deposit the metallic film upon to the cover glass substrate. Then we use focused ion beam to mill the micro structure of plasmonic spiral device. In the aspect of near-field measurement, we use collection mode near-field scanning optical microscope with normal incident set-up and the shear force feedback scanning method to obtain the near-field signal of surface plasmon vortex, which is generated from the plasmonic spiral device. Finally, we compare the experimental data with the simulation result. Similar phenomenon can verify the correctness of the design principle of plasmonic spiral device.

並列關鍵字

nanoplasmonics ； surface plasmon ； optical vortex ； Archimedes spiral ； near-field mearsurement

參考文獻

15. S. A. Maier, Plasmonics: Fundamentals and Applications (Springer-Verlag, 2007).

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