在優化設計的奈米金屬叢集中實現可選擇的侷限表面電漿激發態

本論文提出並以實驗驗證一可選擇性激發侷限表面電漿激發態之奈米金屬叢集結構，且為世界上首度能在近場光範圍內產生高達十種可選擇的激發態；另一方面，此叢集結構尚可用以分析近場光訊號之偏振態，並能進一步判讀圓偏振態之旋光性。本研究包含數值模擬與分析、奈米元件製程，以及光學量測實驗等三部份，將在各章節分別詳細論述。本論文藉由數值模擬發現，在由奈米金屬球或奈米金屬圓柱所構成的叢集結構之中，吾人可藉由控制激發光源的偏振態，產生至多十種不同的表面電漿激發態；而這樣的選擇性激發亦可在具有類似排列的奈米孔洞結構之中實現。上述提出的叢集結構經由優化設計後，吾人使用聚焦離子術系統，在熱蒸鍍之黃金薄膜上進行奈米磨銑，藉以製作元件樣品。量測部份，吾人結合商用之近場光學掃描顯微鏡及自行搭設之光學系統，量測在不同偏振態的激發下，樣品表面之奈米電漿近場光學訊號，並與數值模擬結果比較之。實驗證實本論文之優化叢集結構，可以藉由激發光源偏振態之改變，產生多種表面電漿激發態，且尚可藉以區分圓偏振態之旋光性。

關鍵字

奈米電漿子；表面電漿；偏振態；近場量測

並列摘要

We propose and experimentally demonstrate several nano-devices which are able to selectively excite optical fields using surface plasmons within the designed structures. It was the first time to our best knowledge that up to ten selective states could be excited in the near-field. On the other hand, the device is also capable of analyzing the polarization state in the near-field, especially the handedness of circular polarizations. Numerical analysis, device fabrication and optical measurement are all covered in this work. Numerical experiments suggest that up to ten selective localized surface plasmon states can be generated using excitation with different polarization states, in a device consisting of seven gold nanospheres or nanodisks. This capability can be also reproduced using a designed structure with several nano-holes on a gold film. The proposed device was fabricated using a common process involving thermally evaporated gold film and focused ion-beam milling. Optical measurements were performed with a homemade optical measurement system, which include a near-field scanning optical microscope and polarization controlling optics. Selective excitations of localized surface plasmons were experimentally verified, and shown to be capable of distinguishing the handedness of circular polarizations.

並列關鍵字

Plasmonics ； Surface plasmons ； Polarization ； Near-field measurement

參考文獻

1. W. L. Barnes, A. Dereux, and T. W. Ebbesen, "Surface plasmon subwavelength optics," Nature 424, 824-830 (2003).

2. R. H. Ritchie, "PLASMA LOSSES BY FAST ELECTRONS IN THIN FILMS," Physical Review 106, 874-881 (1957).

3. H. A. Atwater, "The promise of plasmonics," Scientific American 296, 56-63 (2007).

4. D. K. Gramotnev, and S. I. Bozhevolnyi, "Plasmonics beyond the diffraction limit," Nature Photonics 4, 83-91 (2010).

5. M. Stockman, S. Faleev, and D. Bergman, "Coherent control of femtosecond energy localization in nanosystems," Phys. Rev. Lett. 88, 067402 (2002).

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在優化設計的奈米金屬叢集中實現可選擇的侷限表面電漿激發態

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