透過導納軌跡分析設計Tamm 電漿極化子之共振響應

Abstract

電漿極化子共振現象因其普遍具有奈米尺度的局域強電場而在近年來備受重視，其中Tamm電漿極化子是一種受激發於光子晶體表面與金屬膜層介面間的極化子。許多近期的研究顯示，此一共振現象可以靠著改變金屬或是光子晶體膜層的厚度而調控。儘管此可控性已經在模擬與實驗上證實，但甚少研究觸及其背後造成共振波長偏移以及耦合強度變化的運作機制，亦沒有研究提供一套完整的Tamm共振方法，來設計共振波長以及對耦合強度的最佳化。本論文中，我們將透過一套依據導納軌跡發展出的設計方法，來鏈結此多層膜架構的改變與Tamm電漿極化子之共振模態。我們將透過此設計方法，來展示共振波長以及耦合強度的可控性。此外，透過選用不同的金屬膜層來耦合Tamm電漿極化子，可以觀察到在可見光波段，採用銀的結構相對於採用金和鋁的結構分別有4.7倍與84倍大的品質因子，同時採用銀的結構在共振模態下近場電場達到8倍強於入射電場。

Plasmonic resonance has received enormous attention for the past few decades due to its extraordinary behavior and nanoscale localization of immense electromagnetic fields. A Tamm plasmon polariton is a plasmonic resonance excited at the boundary between a photonic crystal and a metal. Many recent studies have shown that the resonance phenomena can be tuned by varying the thickness of the metal film or the photonic crystal. Although this behavior of a TP resonance has been demonstrated by simulation and experiment, the mechanism behind λTP shifting and variation of resonance coupling efficiency has been less studied. Also a systematic approach to design TP resonances at specific wavelengths and optimize the coupling efficiency remains unstudied. In this article, a novel approach based on admittance loci is proposed to demonstrate the relation between thin-film structures and the corresponding Tamm plasmon modes. The tunability of the resonance wavelength and optimization of coupling efficiency are demonstrated. In addition, by using different metals to couple Tamm plasmon modes in the visible spectrum, silver has 4.7 times larger Q-factor than gold and 84 times larger than aluminum at 700 nm. The near-field enhancement of silver Tamm plasmon modes could be up to 8 times larger than incident EM waves.