金奈米粒子和單根金奈米線的基板調節區域表面電漿共振

Substrate-Mediated Localized Surface Plasmon Resonance of Gold Nanoparticles and Single Gold Nanowire

近年來由於金屬奈米結構具有區域表面電漿共振的特性，表現出許多獨特和顯著的光學性質，並可應用於奈米光學元件、生物感測等研究領域，因此受到廣大的重視。當金屬奈米結構置於介電質基板時，會產生基板調節現象，改變原本的共振模態。本文藉由暗視野光學顯微術、分析金奈米粒子與奈米線在基板上的散射光譜，並以有限差分時域法，模擬金奈米結構受基板調節時的共振模態。圓球形的金奈米粒子於基板上，由於基板誘發模態耦合，可觀察到偶極和四極模態的共振波峰，但對單一金奈米線，則只有觀察到偶極模態耦合所產生的共振波峰。 In recent years, metal nanostructures have attracted great research interests in a wide range of fields including nanophotonic devices, biosensors, etc. due to their remarkable optical properties related to localized surface plasmon resonance(LSPR) . When metal nanostructures are located on a dielectric substrate, the strong substrate-mediated effect induces distinct shifts of LSPR peaks and modification of resonance modes. In this article, the substratemediated LSPR modes of gold nanoparticles and nanowires are investigated. The resonance spectra are obtained by dark-field optical microscopy and the resonance modes are analyzed by numerical simulations based on the finitedifference time-domain method. For a spherical gold nanoparticle on a dielectric substrate, the plasmon dipolar and quadrupolar modes can be observed due to the substrate-mediated coupling effect. For the single gold nanowire, only substrate-mediated dipolar coupling modes are observed.