金屬層表面介電奈米結構耦合表面電漿子之互動研究：奈米直寫儀次波長介電光學頭之模擬與研製

Interactions of Dielectric Nano Surface Structures on Metallic Film Coupled Surface Plasmon：Simulation and Fabrication of a Sub-wavelength Dielectric Optical Head for Nanowriter

楊東霖(Dong-Lin Yang)

指導教授 ： 葉超雄

共同指導教授 ： 李世光

國立臺灣大學/工學院/應用力學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.00578

摘要

本論文以近年來全球研究團隊所注目的新物理現象－異常穿透及指向性現象為研究基礎，提出金屬層介電光學頭於指向性的物理機制與最佳化設計法則，並藉由近場光學實驗方式驗證此光學頭具有在遠場範圍保持次波長光點之能力。
金屬層介電光學頭的結構是於金屬薄膜上製作次波長等級的奈米光柵。有鑑於全金屬光學頭製作上的限制，介電光柵結構以其各項優點及製作彈性，成為光學頭大量製造的發展可能。此光學頭以創新設計所提出，並初步觀察其具指向性，本論文將是對於光學頭各子系統的物理機制與潛在能力進行探究。首先提出以嚴格耦合波分析法透過新式模擬模型，以還原介電光學頭的異常物理現象－穿透量與指向性，且能夠獲得有意義的資訊與直接觀察到光學頭的行為。並基於所提出的模型以求證表面電漿耦合作用，與表面電漿波存在於光學頭各子系統的模式。本論文已建立出利用嚴格耦合波分析與有限差分時域法所得之結果的關聯性，以確定表面電漿波與光學頭表面結構之繞射現象所引致指向行為。另外，亦針對介電光學的指向性提出最佳化法則，強調波長選擇與週期設計的重要性。
實驗上採用電子束微影製作光學頭以達成模擬預測與實驗一致的結果，進而確定指向性最佳化法則的正確性與實用價值。另一突破性的實驗即透過近場光學的方式，觀察介電光學頭指向光束的特性，證實金屬層介電光學頭具有於遠場範圍仍保持次波長光點之聚焦能力。

關鍵字

表面電漿子

並列摘要

Based on the new physical phenomena－extraordinary transmission and directional beaming phenomena, the physical origin and optimization rule of dielectric optical head have been proposed in this thesis. And it has been verified that the optical head can produce a confined emitted beam in far field and suppress the decay of intensity simultaneously.
Dielectric optical head is composed of dielectric grating layer constructed on a thin gold film deposited onto the glass substrate. In view of the limitation to fabricate nano-scaled metallic structure, dielectric grating can be flexibly manufactured via various processes, such as nanoimprint for mass production. In this thesis, a new simulation model proposed on rigorous coupled wave analysis (RCWA) has been utilized to explore the extraordinary transmission and directional beaming phenomena of the dielectric optical head. More significant results can be obtained through the new simulation model, which requires fewer computations efforts. The optimization rule proposed for directional beaming emphasizes the importance of selecting wavelength and period of grating. This research also draws the relation between the simulated results from rigorous coupled wave analysis and finite difference time domain (FDTD) method to confirm the surface plasmon wave involved in diffraction.
Experimental results obtained from the optical head developed based on the e-beam lithography fabricated dielectric grating agree well with the simulated results obtained by using the optimization design. Besides, it is verified for the first time that the dielectric optical head can produce a subwavelength beam in far field and suppress the decay of intensity simultaneously as that of the metal head published previously.

並列關鍵字

surface plasmon ； dielectric optical head

參考文獻

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