本研究分成兩個部份，一是利用奈米壓印製程技術製作高深寬比的金屬奈米結構，並分別探討傳統奈米壓印對於金屬高深寬比結構製作的瓶頸，以及本論文在此一問題上的突破與研究成果；二是以奈米共振腔電漿子超穎表面 (Plasmonic metasurfaces)，並研究改變結構尺寸對於光學特性之影響。
首先，本研究發展一種新型技術，利用奈米壓印技術搭配背向式曝光 (Back-side exposure lithography)，在透明基板上製作出高深寬比的奈米級金屬結構。此一技術解決奈米壓印在製作金屬奈米結構時，因受限於舉離製程 (Lift-off) 與模具表面結構深寬比的限制，所產生之深寬比不足的問題與瓶頸。本研究先以奈米壓印製程在透明基板上定義具有遮蔽紫外光效果的金屬圖形，並利用其當作光罩，搭配背後曝光將負光阻定義在沒有金屬結構的區域，並製作出與金屬圖形互補之高深寬比的光阻結構；接著利用二次舉離製程，達到高深寬比的奈米結構。本研究成功製作出結構寬度340 nm、週期700 nm、結構高度736 nm、深寬比為2.16之金屬奈米結構。
本論文之第二部分為製作三種不同功能的奈米共振電漿子腔超穎表面，分別為：單元結構 (Unit cell) 或半波片 (Halfwave plate)、梯度板 (Gradient Metasurface)、以及超穎透鏡 (Meta-lens)，透過不同結構尺寸大小探討其光學性質。實驗流程是在 2 吋玻璃基板上製作出三層金屬高度為40 nm結構，並且包覆三層高度為 200 nm 玻璃材質的介電層。為達成共振腔的目的，第一層和第三層為相互正交且線寬100 nm、週期200 nm的金屬線光柵；第二層則為各種不同設計的奈米圖案化金屬結構，最後組成一奈米共振腔電漿子超穎表面，以實現光學或光電元件的薄型化。所製作之三種共振電漿子腔超穎表面結構中，其最高偏振轉換效率、光束偏轉效率和光點聚焦效率分別為：單元結構為54.4 %、梯度板為35.7 %、超穎透鏡為 21 %。

This study consists of two different research works. The first part involves the fabrication of metallic nanostructures using nanoimprint lithography (NIL) and backside ultraviolet (UV) exposure. The goal is to enhance the aspect ratio of fabricated metallic nanostructures. The second part of this thesis is about the fabrication of plasmonic metasurfaces using NIL methods. It investigates the effects of structural size variations on the optical properties of fabricated plasmonic metasurfaces.
In NIL, due to the constrains coming from metal lift-off process and original structural heigh of imprinting molds, the attainable aspect ratio for metallic nanostructures is quite limited and therefore imposes certain limitation on their applications . This study applies NIL to define metal patterns on a UV-transparent substrate. These metal patterns then serve as photomasks for backside UV exposure on a negative-tone photoresist (PR) so that complementary and high aspect ratio PR patterns are formed. Followed by second metal lift-off, metallic nanostructures with high aspect ratio ae obtained. This study successfully fabricated metallic linear gratings with a linewidth of 340 nm, a period of 700 nm, and a structural height of 736 nm, resulting in an aspect ratio of 2.16.
For fabricating metasurfaces using NIL, three types of nano-resonant plasmonic metasurfaces are fabricated, namely, unit cells or half-wave plates, supercell, and meta-lenses. The optical properties of these structures are examined by varying their characteristic dimensions. Experiments involve creating a 40 nm high three-layer metallic structure on a 2-inch glass substrate, encapsulated by 200 nm high dielectric layer. To form the resonant cavity, the first and third layers consist of orthogonal metal nano-wire gratings with a linewidth of 100 nm and a period of 200 nm. The second layer contains various designed nanopatterned metal structures, ultimately forming a nano-resonant plasmonic metasurfaces. The highest transmission efficiency for each structure is as follows: 54.4% for the unit structure, 35.7% for the supercell, and 21% for the meta-lens.

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