以全向量虛軸有限元素波束傳播法分析槽形與三角形表面電漿子波導

Abstract

本研究致力於使用虛軸有限元素波束傳播法分析表面電漿極化子波導。這些具有侷域模場分布特性的波導包括了對稱�非對稱槽形波導與理想�實際三角形波導，將受到詳細研究。首先，我們介紹表面電漿子與表面電漿極化子導波結構的歷史、相關研究、與基本現象。之後，我們展示分析計算的結果，包括等效折射率與損耗（傳播長度）、模場分布、以及色散關係。在不同設計參數情況下的詳細模場分部有助於觀察物理現象並找出設計方法（以及設計上的權衡考量）。我們解釋觀察的結果，並與已發表的研究作比較。本論文也分析並詮釋許多有趣的議題，諸如鮮少發表的三角形波導的尖角分析計算、非對稱與對稱槽形波導行為的不同傾向、以及重新檢驗在以發表文獻中所描述的模場「截止」現象。

This research is devoted to analyzing the surface plasmon polariton (SPP) waveguides using the finite-element imaginary-distance beam propagation method (FE-ID-BPM). These waveguides, including symmetric/asymmetric slot waveguides as well as ideal/real triangle-shaped waveguides, have confined modal field distributions and are studied in detail. First, we introduce the history and the studies and the basic physical phenomenon of the surface plasmon as well as SPP guiding structures. Then we present our calculation results, comprising the effective index and the loss (propagation length), the modal field profiles, and the dispersion relationships. Detailed modal field profiles in different design parameter cases are displayed to observe the physical phenomenon and scout the design methods (as well as the design trade-offs). The observed results are interpreted and compared to other published works. Several interesting issues, for example, the sharp corner case of the triangle-shaped waveguide which is rarely reported, the different inclination of asymmetric slot waveguides compared to symmetric ones, and the reexamination of the mode ``cut-off' phenomenon described in published literature, are addressed and explained.