| Abstract: | 表面電漿子是一種侷限在金屬和介質介面的與量子化電子振盪模式強烈耦合的電磁波。表面電漿子的低維特性及增強的介面電磁埸引發了各種十分有趣的新奇現象，同時造就了許多新穎的應用如以天文數字般增強的拉曼散射、異常的光通過奈米洞的傳輸、超越光波的繞射極限、改進的太陽能電池效能、微型奈米雷射等。然而，要調控和應用電漿子超穎材料的新穎特性，我們必須徹底理解決定這些超穎材料物理性質的因子如大小、形狀、成分及環境等。因此，本計畫擬採用綜合的理論建模、解析推導和數值模擬方法[1]來探討多種超穎材料中表面電漿子相關現象的起因與機理。我們將依据所研究系統的特征，採用多種互補的數值計算方法[如格點電偶極近似法(DDA)、有限元近似法(FEM)及有限差分時域法(FDTD)]進行一系列的電磁理論模擬. 我們還將結合解析的理論方法如改進的長波近似法和異向電偶極模型對各種表面電漿子共振現象的新穎特性質作深入的分析。我們將研究不同種類超穎材料的新奇物理性質及其重要的應用。研究擬著重於下列三個議題。(1)複雜形狀奈米顆粒(四面體、立方體、八面體和螺旋體等)的電磁響應：這些奈米顆粒是建構許多超穎材料(如電、磁與負折射超穎材料)的基本元素。因此，我們將計算這些奈米顆粒的電漿子能譜、本征模態及電磁極化率等，以便完全了解它們的電磁響應。(2)複雜形狀奈米顆粒構成的低維超穎材料的光學性質：我們擬通過研究這些低維超穎材料的光學性質來了解奈米顆粒間的相互作用對其光學性質的影響並試圖從理論上設計具所需功能的超穎材料。(3)具聚焦和波導性質的雙負折射超穎材料：為建造次波長分辨率的光學奈米元件，我們同時需要次波長光源和偵測器。我們擬尋找能使我們充分利用超穎材料負折射來實現光和物質波聚焦的條件。本計畫含有極為有趣但頗具挑戰性的課題，在數學上和計算上需要繁重的工作量。而且，超穎材料電漿子學是一個快速發展的新興領域。因此，為求本計畫成功，我們擬整合俄羅斯Klimov教授和台灣郭光宇教授兩個研究團隊互補的專長、技術及人力，來共同攻克本計畫所提的研究課題。我們還將和俄羅斯與台灣的實驗同仁交流與合作、一起攻克超穎材料電漿子學中一些重要研究課題、共同培養奈米光電科技人才。
Surface plasmon polaritons (SPPs) are electromagnetic waves confined to a metal-dielectric interface and coupled to the collective oscillation of free charge carriers. The low-dimension nature of SPPs and the strong electromagnetic field at the interface are responsible for many fascinating phenomena in fundamental science and exciting opportunities for technological applications such as enhancing Raman scattering by astronomical orders of magnitude, enabling extraordinary transmission of light through nanoholes, guiding electromagnetic waves beyond the diffraction limit, developing metamaterials with negative refraction, improving the efficiency of solar cells, and developing ultrasmall nanolasers. In order to manipulate the novel properties of plasmonic nanomaterials for various applications, we should thoroughly understand how the factors such as the shape, size, composition and environment of the structures control their physical properties. The principal purpose of this proposal is, therefore, to understand the origin and mechanism of the exciting surface plasmon-related phenomena in a range of metal nanomaterials. This will be achieved primarily by a powerful combined approach of the analytical modeling and numerical simulations [1]. We will perform extensive numerical electromagnetic simulations by using several complementary frequency-domain methods [e.g., the discrete dipole approximation (DDA) and finite-element method (FEM)] as well as the time-domain method [i.e., finite-difference time domain (FDTD) method)] that we have recently acquired. Our numerical calculations will be complemented by the analytic theoretical techniques such as the anisotropic electric dipole model. We will investigate the novel properties of different kinds of plasmonic nanomaterials and their fascinating potential applications. We will mainly focus on the following three topics. (1) Electromagnetic responses of single nanoparticle of complex shapes (e.g., tetrahedron, cube, octahedron, other platonic solids and chiral nanoparticles): These single particles are the building blocks of many plasmonic nanomaterials such as electric, magnetic and negative-index metamaterials. Thus, to understand fully their electromagnetic responses, we will find the plasmonic spectra and eigen-modes as well as the electromagnetic polarizabilities of these particles. (2) Optical properties of low-dimensional metamaterials of complex nanoparticles: We will then investigate the optical properties of the low-dimensional metamaterials made of these nanoparticles, to find the effects of the inter-nanoparticle interaction on the optical properties of these metamaterials, and to theoretically design novel metamaterials with desired properties. (3) Focusing and guiding properties of double negative metamaterials: We will also consider the double negative metamaterials made of single nanoobjects of nontrivial shapes. To build nanodevices with a subwavelength resolution, one would need both subwavelength sources and detectors. We thus want to find the conditions and geometries which would allow one to make full use of the negative refraction potential of the metamaterials for light and matter wave focusing applications. This proposal contains some exciting projects, requiring heavy demands both mathematically and computationally. Furthermore, plasmonic metamaterials are an emerging important field that is developing rapidly. Thus, to be successful, we will pool together the complementary expertise, skills and manpower of the research groups of Prof. Klimov in Russia and Prof. Guo in Taiwan to form a winning international collaboration team. Indeed, Prof. Klimov is a leading Russian electromagnetic theorist in the fields of photonics and plasmonic metamaterials. Prof. Guo is a prominent solid state theorist and also a leading computational materials physicist in Taiwan. Together, we will be able to carry out the exciting and challenging projects proposed here to fruition. We will also work closely with the experimental colleagues in both Taiwan and Russia and strive to make some breakthroughs. |
