金屬奈米體系之表面電漿模態色散研究

Abstract

近年來，表面電漿極化子(Surface plasmon polaritons)的研究越來越熱門，它的相關應用也如火如荼地在發展，至於電腦模擬研究也是層出不窮。之前已有許多人對平板、圓球、單根圓柱等簡單體系做了詳細研究，至於比較複雜奈米體系之間的耦合效應，是如今的一大研究重點。我們使用有限元素法(FEM)來探討奈米金屬表面電漿極化子(SPPs)的色散關係，首先針對單一介面(空氣/金屬)、金屬薄板和單根無限長金屬圓柱做計算，利用我們使用的方法，得到和解析解一致的結果，確定我們方法的可靠性，再來，對雙根無限長金屬圓柱其表面電漿模態的SPP色散關係作探討，給出電場和電荷分布等詳細分析。對於單根圓柱，其色散關係展示出兩種模態，由電荷分布可明顯區別出這兩種。但對於雙根圓柱，倆者之間的模態會互相耦合，進而產生出新的混合模態，故我們對此進行深入的探討，分析整理出這些新的模態。

Surface plasmon polaritons (SPP) are electromagnetic eigen-excitations coupled with charge oscillations at the metal-dielectric surface, which has been applied in optical imaging, bio- and chemical- sensors, enhanced Raman and nonlinear optics effect, etc by favor of its sub-wavelength and local field enhancement effects. People have studied surface plasmon modes in single metallic nanostructure, including sphere, ellipsoid, cylinder, etc. Now the coupling effects between nanostructures become a new hot topic since they will give rise to fascinating properties. Here we will focus on the dispersion of propagating surface plasmon modes in periodic metallic nanostructures. Our approach is the eigenmode analysis based upon the finite element method (FEM), and can be applied to 2D/3D dispersive, anisotropic, and arbitrary shaped nanostructures.