菱形晶格週期性金屬孔洞電漿子熱輻射器和窄頻共振腔型熱輻射器之特性研究

The Characteristics of Plasmonic Thermal Emitters with Top Metal Perforated by Hole Array Arranged in Rhombus Lattice and the Study of Narrow Bandwidth Cavity Thermal Emitters

吳奕廷(Yi-Ting Wu)

指導教授 ： 李嗣涔

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.03371

摘要

本文的第一個主題是從理論和實驗探討銀薄模上菱形晶格週期性圓型孔洞的異常性穿透現象及其對電漿子熱幅射器幅射頻譜的影響，當銀/矽模態波長夠長使得銀/矽模態和銀/空氣模態不耦合時，銀/矽模態的穿透強度由其簡併模態的數目決定；在銀/矽模態和銀/空氣模態耦合的短波長區，銀/矽模態的峰值將因藕合而變得不明顯。對於菱形晶格電漿子熱幅射器而言，其幅射峰值的強度為黑體幅射強度乘上表面金屬的穿透效率，穿透效率正比於簡併模態的數目。本文的第二個主題是將電漿子熱幅射器的厚度增加到微米等級以分析反射頻譜和幅射頻譜中的共振腔模態，發現共振腔膜態也會如同表面電漿子般的和表面週期性孔洞耦合產生布拉格散射共振腔模態；本文提出了隨機孔洞分布型共振腔熱幅射器打亂表面的週期以消除和週期有關的表面電漿子模態和布拉格散射共振腔模態以實現窄頻純頻譜的中紅外光共振腔型熱幅射器，並藉由改變孔洞的大小發現了孔洞的存在將導致了侷域型共振腔模態和 Fabry-Peort 孔洞振盪模態的產生，雖然小孔洞的隨機孔洞分布型共振腔熱幅射器可以提供純淨的幅射頻譜，其輸出強度卻受限於低密度的孔洞總面積而相當的弱。據此，本文提出了另一種新穎的短週期孔洞陣列型共振腔熱幅射器以解決輸出強度的問題：高輸出強度、純淨的幅射頻譜、可在高溫下穩定的操作、低半高寬的幅射峰值和微弱的非理想效應效像是侷域型共振腔模態或 Fabry-Perot 孔洞振盪模態可以同時被達成，而且只要改變共振腔的厚度即可決定不同波長的幅射峰值。

關鍵字

表面電漿子 ； 熱幅射器 ； 中紅外光 ； 菱形晶格 ； 異常性穿透

並列摘要

In this first topic of this thesis, the extraordinary transmission characteristics of silicon substrates with a silver film on top perforated with hole array arranged in a rhombus lattice are investigated in theory and experiment. It is found that the transmissions of Ag/Si modes are approximately linearly dependent on the numbers of degenerated modes in the longer wavelength range where the couplings between Ag/Si and Ag/air modes are weak. In the shorter wavelength range where Ag/Si and Ag/air are coupled together, the transmission peaks of Ag/Si modes are unapparent due to modes coupling. For plasmonic thermal emitters (PTEs) with hole array arranged in rhombus lattice, the peak intensities follow the blackbody radiation curve multiplying transmission efficiency of the top metal film which is dependent on the numbers of degenerated modes. In the second topic of this thesis, the SiO2 thickness of PTEs is increased to the order of μm to investigate cavity modes in the reflection and emission spectra, it is found that cavity modes (CMs) would be scattered by the periodic hole array and result in many Bragg scattered CMs in the spectra. Cavity thermal emitters (CTEs) with randomly distributed hole array (RDHA) are proposed to eliminate Bragg scattered CMs and Ag/SiO2 SPPs modes to realize narrower-band mid-infrared thermal emitters with purer spectra. The influence of hole size to the CMs is also investigated, it is found that larger scattering of light through larger surface hole array would form the localized CMs (LCMs) and Fabry-Perot hole shape resonance (FP hole) modes. Although CTEs with RDHA can offer pure emission spectra if the hole size is small, their output intensities are very weak due to low density of total hole area. Novel CTEs with short period of hole array (SPHA) are proposed to overcome the intensity problem. High output intensity, pure emission spectra, high temperature operation, narrow full width half maximum of emission peaks and low non-ideal effect such as LCMs and FP-hole modes and could achieve simultaneously. The wavelengths of emission peaks are tunable by the thickness of the cavity.

並列關鍵字

surface plasmon ； thermal emitter ； mid-infrared ； rhombus ； extraordinary transmission

參考文獻

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