表面電漿共振效應於光奈米元件之數值研究

Numerical Investigation of Surface Plasmon Resonance Effects on Optical Nanodevices

胡至展(Chih-Chan Hu)

指導教授 ： 蔡曜聰 ； 周趙遠鳳

國立中央大學/資訊電機學院/電機工程學系/博士(2015年)

摘要

在本篇論文中，我們將依序由微小奈米粒子於光觸媒系統的應用出發，逐步探討到體積較大的光奈米元件，接著論及各元件間連結所需的奈米波導等三領域的表面電漿共振效應之研究與應用。
在第一個領域中，我們利用三維有限元素法，針對銀奈米珠成長於二氧化鈦光觸媒活化層上之表面電漿共振效應來進行數值研究。那麼由結果顯示論文中結構C在金屬奈米粒子附近能呈現出較強的近場值。另外基於模擬結果，我們瞭解到具有銀奈米珠之二氧化鈦層能在近紫外光、可見光及近紅外光頻譜上呈現侷域性較強的表面電漿共振效應。其電場強度增強之主要因素，係因填充進銀奈米珠之介電值大小逐步提高所肇致。
接著在第二領域中，我們同樣利用三維有限元素法來針對週期性排列之外廓式領結型奈米天線陣列(POBNA)/實心式領結型奈米天線陣列(PSBNA)埋入基板之效應與穿隧特性進行數值研究。其中間隙場增強特性、穿隧特性、電荷分佈及電荷模型之實部與虛部等議題，皆被我們徹底的研究及討論。尤其當入射光波長大於0.775 μm時，週期性外廓式領結型奈米天線埋入時之gap enhancement更是高達2×108。而且我們也發現POBNA/PSBNA埋入矽基板之深度可作為場強及共振波峰值位移量等重要因子之參考依據。同時比起過去其他論文中曾提及之POBNA/PSBNA結構，這次我們提供了更微小尺度之設計和更寬廣的吸收頻譜應用。
最後在第三個領域中，我們也針對不同型態之S型銀奈米線波導進行數值分析及研究，同時也發展了能透過某段空氣距離，將入射光耦合至彎曲型電漿奈米線波導之重要設計指南。藉由三維有限元素法之數值研究結果，我們瞭解如果在S型銀電漿奈米線波導外層利用介電質材料來包覆的話，其表面電漿子電場侷域特性會被大大增強。其中當入射光波長介於300 nm~ 345 nm及455 nm~ 780 nm之波段時，於波導末端隔200 nm處偵測近場強度的話，我們能獲得高於200 V/m之近場強度，顯見我們的設計提供了極佳的近場增強及更寬頻譜的傳播範圍。

關鍵字

數值研究 ； 光奈米元件 ； 表面電漿共振 ； 光觸媒 ； 奈米天線 ； 奈米線波導

並列摘要

This dissertation describes a study on three applications of surface plasmon resonance (SPR): the use of nanoparticles in a photocatalyst, the investigation of larger optical nanodevices, and waveguide connections among components.
Regarding the first application, a three-dimensional (3D) finite element method (FEM) was used to numerically investigate the effect of SPR on the photocatalytic activity of silver nanobeads photodeposited onto a TiO2 layer. Results showed that the proposed case C structure exhibited increased electric near-field amplitude around the metal nanoparticles (MNPs). Simulation results showed that Ag nanobeads photodeposited onto a TiO2 layer support localized SPR in near-UV, visible, and near-infrared spectral domains. The region of an enhanced electric field intensity increased as the filling dielectric medium in dielectric hole (DH) increased.
Regarding the second application, FEM with 3D calculations was used to numerically investigate the effects and transmittance properties of a periodic outline bowtie nanoantenna array (POBNA)/periodic solid bowtie nanoantenna array (PSBNA) embedded in a silica substrate at different depths. Investigation of the gap enhancement, transmittance properties, charge distribution, and the real and image charge model is discussed here. Gap enhancements associated with the embedding of POBNA exceeded 2 × 108 for incident wavelengths above 0.775 μm. The embedded depth of the POBNA/PSBNA was found to be a crucial parameter that could influence field enhancement and the peak resonant wavelength position. This finding could facilitate realizing more compact dimensions and a wider spectral domain compared with those of previously proposed structures while maintaining the POBNA/PSBNA size.
Regarding the third application, an S-shaped Ag plasmonic nanowire waveguide (SSAPNW) was analyzed numerically by using 3D FEM, and key design guidelines that can facilitate ensuring effective propagation of incident light through air into a bending plasmonic nanowire waveguide were developed. The results indicated that the confinement of the surface plasmon fields of the SSAPNW could be considerably improved by covering the metallic nanowire with a dielectric coating. Near-field intensities at a distance of 200 nm from the distal end of the SSAPNW can exceed 200 V/m for incident wavelengths in the ranges 300 nm <  < 345 nm and 455 nm <  < 780 nm; thus, a high field intensity and broadband propagation can be achieved.

並列關鍵字

Numerical Investigation ； Optical Nanodevices ； Surface Plasmon Resonance ； Photocatalyst ； Nanoantenna ； Nanowire Waveguide

參考文獻

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