含高分子與液晶雙層膜之一維光子結構的穿透光譜

Transmission Spectra of One-Dimensional Photonic Crystal with a Stratified Polymer/Liquid-Crystal Film

陳建璋(Chien-Chang Chen)

指導教授 ： 李偉 ； 徐芝珊

中原大學/理學院/物理研究所/碩士(2013年)

https://doi.org/10.6840/cycu201300784

摘要

本研究利用紫外光曝曬強度及曝曬時間的區域差異，製作出具有空間漸變厚度之層化高分子/液晶複合薄膜（phase separated composite film; PSCOF）並將此雙層結構引入一維光子晶體作為缺陷層，透過調控電壓與缺陷峰位置的關係，歸納出了高分子層於一維光子晶體的貢獻。
根據研究成果，存在於液晶盒中之層化高分子/液晶複合薄膜能使液晶盒之厚度更加穩固，且該特性隨著高分子層厚度的增加而漸趨明顯，大幅增加了以液晶作為缺陷層之一維光子晶體，其缺陷峰在高電壓調控時的穩定性。另外，缺陷峰調控之波段大小也因高分子層與液晶層厚度比例不同而有所改變，在雙層結構中，使用高分子單體與液晶不同比例之混合液，將使高分子層與液晶層具有相同之厚度比例，液晶層厚度越大缺陷峰調控範圍越大。為了進一步利用高分子層在不同製程中產生的厚度可變性，本實驗利用衰減強度線性漸變之光衰減片，使聚合過程中液晶盒各區域曝曬強度具線性變化，製作出高分子層厚度具空間線性漸變之層化高分子/液晶複合薄膜液晶盒，透過相位延遲量測技術及理論公式計算出各區域之高分子層厚度佐以輔證。最後吾人嘗試將此厚度漸變之雙層結構導入一維光子晶體作為缺陷層，整體缺陷峰在未施加電壓時，隨著液晶層厚度漸漸變小而紅移，此一成果有別於傳統多匝道光通訊的應用，能以空間的調變達到不同通訊波段的切換。

關鍵字

相分離複合薄膜 ； 液晶 ； 光子晶體

並列摘要

In this thesis, optical properties of one-dimensional (1D) photonic crystal （PC）infiltrated with an inhomogeneous bilayer structure, containing a liquid crystal （LC）and a phase separated composite film （PSCOF）, as defected layer is investigated. The inhomogeneous PSCOF bilayer is fabricated with spatial-varying thickness of polymer layer, leading to the obtaining of gradient refractive index. The contribution of polymer layer to the optical profiles of defect modes in our designed 1D PC/PSCOF cell is clarified by measuring the voltage- and position-dependent transmission spectra of the cell.
For the typical PC/PSCOF cell, experimental results on the voltage dependence of transmission spectra indicate that the polymer layer plays the role on stabilizing the thickness of the PC/PSCOF cell. Such a feature prevents the thickness of cell from distortion and thus enhances the stability of defect-mode peaks while applying high voltage to the cell. In addition, the tunable wavelength-range of defect modes is widened as the thickness of polymer layer decreases because of the increasing of overall optical path length, contributed by the LC. According to this thickness dependence of wavelength tunability, this study further designs an inhomogeneous PSCOF bilayer having spatial-varying polymer layer thickness by using variable density filter during UV exposure. The thickness of each layer in PSCOF bilayer is calculated by measuring the phase retardation of the cell. While using this inhomogeneous PSCOF bilayer as the defect layer in 1D PC, the spatial shift of defect modes is attributable to the gradient-variation of polymer layer thickness as well as the phase retardation in a cell. As a result, this study demonstrates firstly the spatially tunable photonic device based on the 1D PC/PSCOF hybrid structure.

並列關鍵字

liquid crystal ； phase separated composite film ； photonic crystal

參考文獻

[35]　艾倫，《含扭轉向列液晶之一維光子晶體的光譜模擬》，碩士論文，中原大學奈米科技碩士學位學程，民101年。

[37]　呂易昇，《層化高分子/液晶複合薄膜之光電特性》，碩士論文，中原大學應用物理研究所，民96年。

[38]　巫崇印，《層化高分子/液晶複合薄膜之直流電場效應》，碩士論文，中原大學應用物理研究所，民97年。

[1]　Y. H. Lin, H. Ren, S. Gauza, Y. H. Wu, Y. Zhao, J. Fang, and S. T. Wu, “IPS-LCD using a glass substrate and an anisotropic polymer film,” Journal of Display Technology 2(1), 21–25 (2006).

[3]　S. John, “Strong localization of photons in certain disordered dielectric superlattices,” Physical Review Letters 58(23), 2486–2489 (1987).