研究生: |
韋冠中 Wei, Guan-Joung |
---|---|
論文名稱: |
膽固醇液晶模板於可寬頻帶調控與高反射率光子能隙元件之研究與應用 Wide-band spatially tunable and hyper-reflective photonic bandgap based on a refilled cholesteric liquid crystal polymer template |
指導教授: |
李佳榮
Lee, Chia-Rong |
學位類別: |
碩士 Master |
系所名稱: |
理學院 - 光電科學與工程學系 Department of Photonics |
論文出版年: | 2014 |
畢業學年度: | 102 |
語文別: | 英文 |
論文頁數: | 70 |
中文關鍵詞: | 液晶 、膽固醇液晶模板 、高反射率光子能隙 、空間調控性 |
外文關鍵詞: | liquid crystal, cholesteric liquid crystal polymer template, hyper-reflective photonic bandgap, spatially tunable |
相關次數: | 點閱:97 下載:2 |
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近年來,液晶領域科學家們利用具旋性之液晶高分子製作新穎之膽固醇聚合物模板 (簡稱模板),此模板可有效改善膽固醇液晶模板之天生光學侷限性,例如:提高反射率超過傳統膽固醇液晶之反射極限50%、在單一樣品中具有多個光子能隙、可彈性置換回填材料改變其光學特性等。
本篇論文乃製作兩個具有螺距梯度且相反旋性之膽固醇液晶模板,組合成一個可空間調控且可同時反射相反旋性圓偏振光之複合式膽固醇聚合物模板,其可空間調控波段範圍涵蓋整個白光區。此研究亦進一步探討此模板反射率受限之可能原因與增進反射率之方法,此方法可藉由將模板樣品升溫高於回灌液晶之澄清點以上,使得此模板之回灌液晶於液晶相時之散射可大大地有效降低,其反射率亦可明顯提高。
最後,本篇論文利用模板製作出擁有高反射率與可寬頻帶空間調控之光子能隙元件,其最高反射率可超過85%,可空間調控光子能隙波段涵蓋400 nm至800 nm,其覆蓋整個全白光範圍。未來,此具有全白光區高反射率之可空間調控光子能隙模板元件不只可應用於可全白光區之空間濾波器亦可發展成可全白光區空間調控、無須反射鏡、可同時產生左右旋圓偏振雷射之低能量閾值雷射器。
The scientists in the field of liquid crystal (LC) exploited chiral LC polymer to fabricate novel cholesteric LC (CLC) polymer template (simply called template) in recent years. The template can effectively overcome the limitation in the optical features of traditional CLCs, such as enhancement of reflectivity over 50%, multiple photonic bandgaps (PBGs), and changeable optical characteristics by flexibly replacing the refillingLC materials, and so on.
This thesis fabricates two gradient-pitched CLC templates with two opposite handednesses, which are then merged as a spatially tunable and hyper-reflective CLC template sample. This sample can simultaneously reflect right- and left-circularly polarized lights and the tunable spectral range includes the entire visible region. In addition, this study investigates the causes to limit the reflectance of the template sample and a method to improve the reflectance. By increasing the temperature of the template sample exceeding the clearing point of the refilling LC, the light scattering significantly decreases and the reflectance effectively increases.
In summary, this study fabricates a merged template sample to develop a wide-band spatially tunable and hyper-reflective PBG device. This device has a maximum reflectance over 85% and a wide-band spatial tunability in PBG between 400 nm and 800 nm which covers the entire visible region. This hyper-reflective PBG template device with a wide-band tunability over entire visible region can not only be employed as a wide-band spatially tunable filter, but also used to develop a low-threshold mirror-less laser with a spatial tunability at entire visible region and simultaneous emission of left- and right-circular polarizations.
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