以平行化分離場量有限差分時域法分析週期性多段轉折奈米天線結構

Abstract

時域有限差分法已被廣泛的運用在電磁數值模擬上，我們採用C++程式語 言建構時域有限差分法中的分離場形法模擬器，進行周期結構在平面波斜向入 射所產生相關效應的研究。為了增加計算效率，我們適時的使用平行化運算， 並且透過多台電腦間的資料傳遞介面協定。本研究以數值電磁方法討論以一個 寬頻、波長為0.3~4.0 微米之間的平面波正向或斜向入射到中心對稱及反對稱 的多段轉折奈米天線。因為局域表面電漿共振現象天線間隙間的電場強度增量 會非常高，因此我們探討在斜向入射時不同入射角度，以及正向入射時不同極 化角度，對天線間隙裡的電場強度增量頻譜的影響。此外，本研究也會探討將 y 方向的週期長度增倍時，天線間隙裡的電場強度增量頻譜的變化會如何。研 究結果發現電場強度增量頻譜除了和入射角度及極化角度有關，也會和y 方向 的週期長度相關。

The finite-difference time-domain method (FDTD) has been widely used in numerical electromagnetics. We have established a parallelized three dimensional (3-D) split-field FDTD simulator in C++ language to study the periodic structures with obliquely incident plane wave source. In addition, several computers are connected to accelerate the computations by using the message passing interface (MPI) protocol to evaluate the efficiency of the simulation. In this research, the asymmetric and symmetric Multi-Bent-Section Nano-Antenna (MBSNA) arrays are numerically studied by a broadband normally or obliquely incident plane wave to obtain responses in the wavelength range from 0.5um to 4.0um. The electric-field enhancement in the gaps of the nano-antennas will be very high because of the phenomenon of localized surface plasmon resonance (LSPR). Thus, we studied the influence of different varied incident angles in obliquely incident source or different polarization angles in normally incident source on the enhancement spectrum in the gap of the nano-antenna. Moreover, we double the y-direction periodic length of the symmetric MBSNAs to observe the difference in the enhancement spectrum in the gap of the structure. The enhancement spectrum in the gap of the nano-antenna is found to depend on not only the incident and polarization angle, but the y-direction periodic length.