橢圓金奈米環之長短軸比效應於表面電漿光學與折射率感測特性之研究

Abstract

對於不同的環寬、金奈米環的高可調性表面電漿效應已經被研究。由於金奈米環的內側和外側的表面電漿偶合，使得整體的電場增強度大大的提升；這樣的特性可以用在生醫感測、光學捕捉和電場增強光譜。 在這篇研究中,我們提出了橢圓金奈米環來研究長短軸比效應在複合式結構裡的影響。在模擬和實驗上,我們用共振波長,模態分佈和電荷分佈圖在不同的偏振態方向來理解長短軸比效應在橢圓金奈米環的光學行為。我們發現到共振波長的可調性和電場增強度可以藉由控制長短軸比獲得提升。此外，我們同時研究橢圓金奈米環和橢圓金奈米盤的折射率感測特性做比較。我們觀察到長短軸比效應於表面電漿折射率感測特性的影響，並且在電場於短軸偏振下發現到橢圓金奈米環獨特的光學和感測率特性，也對此做了完整的討論與研究。

The high tunable localized surface plasmon resonance of nanoring has been investigated with different ring widths. The strong electric field intensity enhancement of bonding mode is provided by the plasmon coupling between the inner and outer surface of nanoring, which is suitable for biological sensing, nanotrapping and field enhanced spectroscopy. In this thesis, we propose the elliptical gold nanoring for studying the aspect ratio effect of such hybridized nanostructure. The resonance wavelength, mode profile and charge distribution of elliptical gold nanoring has been studied by simulation and experiment with different aspect ratios and polarizations. The results show that the tunability of the peak wavelength and the electric field intensity enhancement are improved by controlling the aspect ratio. Furthermore, the index sensing properties of elliptical gold nanoring were compared with that of elliptical gold nanodisc. The aspect ratio effect on index sensing was observed and the unique plasmonic properties under transverse polarization have been completely studied.