表面電漿光子晶體之光學特性研究

Abstract

在本論文中主要探討了二維的光子晶體鍍上金屬結合成具有表面電漿特性的週期性結構之光學性質研究。簡易地利用直徑為450跟500奈米的聚苯乙烯顆粒球自我組成的方法排列出二維光子晶體再濺鍍上金屬金即可組成具有表面電漿特性的樣品。因為它週期性表面電漿的特性使得在穿透光譜上有異常的高峰值產生，在之前的研究指出會在穿透光譜上有異常高峰值的原因可能來自於週期性表面電漿結構的繞射，稱為布拉格電漿(Bragg plasmon)。 在實驗上探討了聚苯乙烯顆粒球的粒徑、在不同的偏振光下不同的入射角以及對於環境折射率的敏感度，對於此表面電漿結構在穿透光譜上的影響，有助於了解這種表面電漿週期性結構的成因與特性，並且加以應用；因此我們成功地將液晶與表面電漿週期性結構組合成元件，利用表面電漿週期性結構對於環境折射率的敏感度以及液晶分子折射率的異向性，成功地可利用外加電壓的方式調控表面電漿極化(Surface plasmon polaritons)的位置(同時也是穿透光譜上的高峰值)。 期望對於這種表面電漿週期性奈米結構的了解與應用，可對於未來有更多的應用價值。

In this thesis, the optical properties of plasmonic periodical structure which composes of Au coated on two-dimension (2D) photonic crystal have been studied. 2D photonic crystals were made simply from polystyrene (PS) spheres with different diameters by self-organization method, and then Au film was deposited on 2D PS spheres array. This structure is called as plasmonic photonic crystal with peculiar plasmonic characteristics. With the properties of plasmonic periodical structure, there exist extraordinary peaks in the transmission spectrum. The phenomenon of extraordinary peaks in transmission spectrum is due to the diffraction of plasmonic periodical structure called Bragg plasmon. In this study, multiple factors of the extraordinary transmission peak position, such as the diameter of PS spheres, various incident angles and polarization of excitation, and sensitivity of environmental refractive index, have been investigated to understand the origin and behavior of plasmonic periodical structure. Moreover, liquid crystal and plasmonic photonic crystal have been combined to form a new cell successfully. Using the sensitivity to environmental refractive index of the plasmonic photonic crystal and the anisotropy of refractive index of liquid crystal molecules, the wavelength of surface plasmon polaritons, can be modulated successfully by an applied voltage. We expect that the novel properties of plasmonic photonic crystal shown here, could promote present optoelectronic devices, for a wide range of applications.