超微型電漿透鏡於次波長級聚焦之設計與調變

Design and Modulation of Ultracompact Plasmonic Lens for Subwavelength Focusing

張開昊(Kai-Hao Chang)

指導教授 ： 李柏璁

國立交通大學/電機學院/光電工程系所/博士(2019年)

摘要

次波長級聚焦是一個重要的奈米光學主題;於超解析, 光學儲存, 奈米粒子操控, 奈米微影技術等應用中廣泛使用。 在眾多光學聚焦技術中﹐電漿透鏡為一個簡單方法可產生超越繞射極限之次波長級聚焦。此外﹐它提供了一個光跟物質強交互作用平台伴隨著豐富的光學現象與功能。在本篇論文中﹐我們藉由特別設計之奈米結構達成調變軸向解析度﹐從微米尺度到奈米尺度之解析能力。同時，我們也建立所對應之聚焦近似模型來解釋軸向聚焦特性﹔對具有深度解析能力之奈米光學技術發展是個突破。更進一步地﹐多波長操作可經由金屬光柵之電漿能隙進行篩選，挑出可聚焦之波長。在基本物理特性方面﹐我們研究消散波於增強橫向解析度之現象。我們提出之複合式環型電漿透鏡與人造孔隙型電漿透鏡，可藉由調變相位進而達到不同程度之建設性干涉。同時，消散波參與上述干涉之現象;其間接證據可藉由用掃描式近場顯微術觀察與驗證。
此外﹐在多種不同功能應用需求上,光學捕捉能夠經由不同設計之奈米孔隙下，排成環型陣列而達成。偏極轉換和多重物體捕捉可藉控制入射光之偏振達到動態調變之效果。此研究提供了在微小尺度下達到良好聚焦特性之方法,策略,和實際應用之關鍵點﹔對於奈米光子學和奈米科技之發展相當重要。

關鍵字

表面電漿 ； 奈米光學 ； 次波長聚焦 ； 光學捕捉 ； 消散波

並列摘要

Subwavelength focusing is an important subject for the application of superresolution, optical storage, nanoobject manipulation, and nanolithography. Among many technologies, plasmonic lens (PL) is a good candidate achieving for application of board band operation via tuning plasmon resonance. In addition, it provides a platform of strong light and matter interaction for rich optical properties and functionalities. In this dissertation, we develop the method for modulation of axial resolution from microscale to nanoscale by specially designed nanostructures. The corresponding approximate-perturbed-focus model is established for explaining focusing performances in axial direction, which is a breakthrough for the technology of depth resolving ability. Furthermore, the multiwavelength operations is demonstrated by simple principle with the effect of plasmonic bandgap. For fundamental physical properties, enhanced lateral resolution by tuning evanescent waves is investigated. Modulation of phase is used to tune the degree of constructive interference. Indirect evidence of evanescent-waves interference is found in our proposed plasmonic lens of concentric compound lens and meta-aperture-based lens. These evanescent-waves-mediated optical properties are experimentally demonstrated and realized by using scanning near-field microscopy.
For the application of nanotechnology, the multifunction of micro/nanoparticle optical manipulation and trapping can be achieved through different-shape design of nanoaperture in a circular array. Polarization conversion and multiple-objective trapping can be dynamic modulated by controlling the polarization of incident light. Our research provides strategies and some limited factors including fabrication and measurement in practice which is important for the development of nanophotonics and nanotechnology.

並列關鍵字

surface plasmon ； nanooptics ； subwavelength focusing ； optical trapping ； evanescent waves

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