以三維時域有限差分法研究線性偶極奈米天線結構之間隙電場增強效應

Abstract

三維時域有限差分法已成為廣泛使用的電磁模擬方法，我們利用C++程式語言建構一個具平行運算能力之三維時域有限差分法模擬器， 利用訊息傳遞介面協定進行多工處理下，處理器互相傳遞訊息之方法，進而達到加速模擬之效果。本篇論文主要分析線性奈米偶極天線結構之間隙電場增強效應。 首先，討論單一線性奈米偶極天線，以一正向入射平面電磁波作為波 源，得到波長區間為 0.3 微米到 4.0 微米的響應，計算線性奈米偶極天線間隙之局部電場增強效應及其共振波長，並且調整偶極天線之長度，以觀察天線長度變化對於增強效應之影響和兩者之間的關係。當 極化方向之天線長度越長，其共振波長越長，其增強效應越強。其後研究線性奈米偶極天線陣列，比較不同之天線陣列結構，發現陣列中 單元天線之極化方向長度互相交疊越多，間隙電場增強效應越強，最後以二維線性奈米偶極天線陣列之間隙電場增強效應最強。

The finite-difference time-domain (FDTD) method has been an popular electromagnetics simulation technique. We construct a parallelized three-dimensional (3-D) electromagnetics simulator using the FDTD method in C++ language. We use the message pass interface (MPI) protocol and multiprocessing so that the simulation time can be shortened. The main topic of this thesis research is to analyze the gap-field enhancement of nano dipole antennas under normally incident light. Firstly, single nano-dipoles are simulated by applying a broadband normally incident plane wave to get their responses for the electric-field enhancements in the dipole gap and resonant wavelengths in the wavelength range of 0.3 m to 4.0 m. Then the length of linear dipole nano-antenna is changed in order to observe the influence of dipole length. It is found that the longer that portion in the x-direction of the dipole, the higher the gap-field enhancement. Then linear dipole nano-antennas arrays are studied. Different kinds of nano-antennas arrays are compared. It is found that the more portion in the x-direction of the dipole overlaps with the adjacent dipole in the array, the electric field enhancement would be larger. These results reveal that the 2-D linear dipole nano-antenna arrays have the maximum enhancement.