多個金屬奈米粒子電磁場分佈之數值模擬

Abstract

本論文中，吾人提出一套新穎的簡化邊界積分方程(SBIE)法，以模擬均質空間中多個任意分佈之金奈米球的散射、吸收與侷域電磁場分佈。吾人將SBIE與商業軟體COMSOL所計算之近場作比較，發現兩者相似度高，而且計算多個奈米粒子時，SBIE的計算效率遠勝COMSOL。接著將金奈米球排成各式一維、二維和三維的陣列，模擬結果顯示侷域表面電漿子(LSP)共振強度大幅提升，且其頻寬亦可拓寬至近紅外光波段。吾人亦發現，藉由改變金奈米球的幾何尺寸、粒子間距、奈米球總數、環境的介電常數與各式排列，集體的LSP共振將有顯著可調頻的效果。值得一提的是，此SBIE法比常用之耦合電偶極近似法更嚴謹，更有潛力處理具有不同尺寸、不同形狀與不同材質等的三維多體散射問題。易言之，此套彈性度高的SBIE法有助於設計各式新穎的表面電漿子元件。

In this thesis, we propose a novel simplified boundary integral-equation (SBIE) method for investigating the scattering, absorption and field localization properties of multiple gold nanospheres (NSs) arbitrarily distributed in a homogeneous space. By comparing with the commercial software COMSOL, simulation results of the near-field patterns confirm the validity of the SBIE method. Meantime, we find that the SBIE is much more efficient than COMSOL for treating a large number of nanoparticles. Then, we arrange the gold NSs as one-, two- and three-dimensional arrays to further test our program. It is found that the localized surface plasmon (LSP) resonance can be enhanced and widely broadened to the near infrared (NIR) range. We also find that the LSP resonance can be significantly tuned by varying the constituent nanoparticle geometries, interparticle separation, total NS number, dielectric environment, arrangement of distributions, etc. Note that, the SBIE is more rigorous than the conventional coupled-dipole approximation (CDA) model and has the potential to cope with scattering problems for multiple objects with different sizes, shapes and materials. In other words, this versatile SBIE method is helpful for the design of a variety of novel plasmonic devices.