孔洞形狀對於鑽有週期性孔洞陣列金屬/介電材料結構穿透特性之效應及在紅外線熱輻射源與光學濾波器之應用

本文在實驗上觀察不同長寬比的長方形孔洞在二維金屬薄膜孔洞陣列結構的異常性穿透特性。實驗發現當孔洞的長寬比達到7，主導穿透的電磁場會由原本的表面電漿模態轉變成侷域型的震盪模態。其中我們也研究在不同形狀的孔洞陣列，Wood異常特性對穿透頻譜造成的影響。我們使用簡單的傳輸線模型來說明侷域型穿透頻譜的尖峰波長位置變化。我們也探討了銀/二氧化矽/銀三層結構的表面電漿熱輻射元件，我們比較二氧化矽層厚度在不同厚薄的情形，發現當二氧化矽厚度較薄時，對整體的熱輻射能量是有提升的作用。主要是因為表面電漿傳遞上的損失並且儲存於兩層金屬間的二氧化矽層，並且增強了光學吸收的特性。不同的窄頻紅外線光源也被探討，我們利用厚度較厚的二氧化矽層作為銀/二氧化矽/金三層結構的熱輻射元件之光波導層，加熱時產生的波導震盪模態能達到窄頻的紅外線光源之用途。研究二氧化矽厚度對於表面電漿及波導模態間的色散關係，並且由理論得到與實驗一致的結果。藉由縮小孔洞的週期，我們可以達到單一模態的光源且達到更窄頻的效果，其品質因子可達到33。實驗證實利用聚二甲基矽氧烷的基板可以容易的製作出週期性的金屬波浪結構，且週期可以簡易的由沉積的金屬厚度來決定。這樣可彈性伸縮的金屬光柵激發了銀/空氣的表面電漿模態，我們可以藉由外加應力的拉伸進而改變此共振波長達到3.5%，實驗證實這樣新型的可調變光學濾波元件的確有發展的可能性。

關鍵字

異常性穿透；表面電漿；熱輻射；波導；品質因子；聚二甲基矽氧烷；光學濾波元件

並列摘要

The extraordinary transmission through silver film perforated with rectangular hole array with different aspect ratio is investigated. The propagating surface plasmon polaritons (SPPs) is observed to transform to localized resonance mode when the aspect ratio exceeds 7. The role of the Wood’s anomaly on the shape of the transmission spectrum is also investigated. The transmission peak of the localized resonance is fitted quite well with the theoretical calculation using a simplified transmission-line model. Additionally, the emission spectra of Ag/SiO2/Ag tri-layer plasmonic thermal emitters are investigated. Comparison of the emission spectra of the thermal emitters with SiO2 layers having different thicknesses, it is found that the thermal emission can be enhanced when the SiO2 layers is thin. The results suggested that the surface plasmon (SP) leak and store in the intermediate SiO2 layer between two metal layers that will enhance the absorption in the tri-layer structure. The various narrow bandwidth infrared light sources are reported. The suitably designed trilayer Ag/SiO2/Au thermal emitter with thick SiO2 layer supports the waveguide mode (WM) and can be used as the narrow bandwidth infrared light source. This study investigates the influence of dielectric thickness on the energy dispersion relations of SPs and waveguide modes and derives the theoretical dispersion relation, which fit well with experimental results. By shortening the lattice constant, the pure emitted peaks with ultra-narrowband can be obtained, the optimum quality factor approaches to 33. Additionally, we demonstrate that a periodic metallic wavy-structure can be easily fabricated on elastomeric polydymethylsiloxane (PDMS) substrates. The period of the wavy-structure is controllable by varing the thickness of the deposited silver film. The elastomeric-gratings can excite surface plasmon on Ag/air interfaces, the resonant wavelength can be tuned to a range of 3.5% by applying an external mechanical strain. Our experiments demonstrate the possibility of a new type optical filter with tunable wavelengths.

並列關鍵字

extraordinary transmission ； surface plasmon polaritons ； thermal radiation ； waveguide mode ； quality factor ； polydymethylsiloxane ； optical filter device

參考文獻

[1] H. A. Bethe, “Theory of diffraction by small holes,” Phys. Rev., 66, 163 (1944)

[2] T. W. Ebbesen, H. J. Lezec, and H. F. Ghaemi et al., “Extraordinary optical transmission through sub-wavelength hole arrays,” Nature, 391, 667 (1998)

[3] R. W. Wood, “Anomalous diffraction gratings,” Phys. Rev. 48, 928 (1935)

[4] L. Rayleigh, “Note on the remarkable case of diffraction spectra described by Prof. Wood,” Philos. Mag. 14, 60 (1907)

[5] J. M. McMahon, J. Henzie, and T. W. Odom et al., “Tailoring the sensing capabilities of nanohole arrays in gold films with Rayleigh anomalysurface plasmon polaritons,” Opt. Express, 15, 18119 (2007)

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孔洞形狀對於鑽有週期性孔洞陣列金屬/介電材料結構穿透特性之效應及在紅外線熱輻射源與光學濾波器之應用

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