以三維時域有限差分法研究電漿子奈米結構之耦合效應及感測應用

Abstract

本論文中,我們利用 C 語言建構了一個平行化三維時域有限差分模擬器,並利用多台電腦透過訊息傳遞介面協定來加速模擬。 我們利用這個自行建構的平行化時域有限差分模擬器來模擬奈米結構,討論其耦合現象,並應用於感測。第一部份,我們研究直立型及平躺型開口環形共振腔的共振機制並將之應用於感測,其中感測器的感測能力可由感測強度以及品質因素兩個量度作為標準,並且發現,透過增加結構的週期能夠有效提升品質因素,其中平躺環形共振 腔可達到品質因素 15.54 而直立環形共振腔更可達 37.71。直立結構 由於多了磁場直接耦合的效應,會使得感測效率勝過平躺結構,但由於製程的困難性,我們致力於增加平躺式結構的品質因素。因此於第二部分,我們探討平躺型結構的奈米結構之耦合現象,其中包括結構 的非對稱性及耦合強度對於耦合效應的影響,並將耦合結構應用於感測。透過我們的設計,在七重奈米柱的結構我們能夠將品質因素提升 到 26.55,對比最原始的平躺型開口環形共振腔來說,有非常顯著的提升。

In this thesis, a parallelized three-dimensional (3-D) finite-difference time-domain (FDTD) numerical simulator by using the message passing interface (MPI) library code in C language is developed and applied to the following topics. In the first part, we systemically investigate the mechanism of resonances of split-ring-resonators (SRRs) and apply them to sensing applications. We analyze two types of SRRs, vertical SRRs (VSRRs) and planar SRRs (PSRRs), and investigate the sensing performance by sensitivity and figure of merit (FOM) for both types of SRRs. We find out that the FOM can be effectively enhanced by increasing the period of the structure and FOM = 15.34 for PSRRs and FOM = 37.71 for VSRRs can be achieved. The sensing performance of VSRRs surpasses PSRRs because of the bianisotropic effect. However, the planar structures are less difficult in fabrication, and thus we further study the planar structures to see if we can enhance their sensing performance. In the second part, we investigate coupling effects of planar nanostructures, including PSRRs and nano-rods. We investigate the coupling interaction between plasmonic nanostructures by analyzing the asymmetry effect and coupling strength of structures and apply them to sensing applications. By delicately utilizing the coupling effects, in a seven nano-rod array case, FOM = 26.55 is achieved, which is a great improvement compared to original PSRR cases.