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系統識別號 U0026-0109201510563100
論文名稱(中文) 以回灌液晶模板技術發展可白光域空間調控波長之雷射
論文名稱(英文) Spatially Tunable Lasing Emission in Visible Region Based On Refilled Liquid Crystal Template Technique
校院名稱 成功大學
系所名稱(中) 光電科學與工程學系
系所名稱(英) Department of Photonics
學年度 103
學期 2
出版年 104
研究生(中文) 林宏霖
研究生(英文) Hong-Lin Lin
學號 L76021406
學位類別 碩士
語文別 英文
論文頁數 101頁
口試委員 指導教授-李佳榮
口試委員-傅永貴
口試委員-黃家逸
口試委員-蔡明善
中文關鍵字 膽固醇液晶模板  高反射  光子能隙  可空間調控性  雷射模態轉換  能隙邊緣雷射 
英文關鍵字 cholesteric liquid crystal polymer template  hyper-reflectivity  photonic bandgap  spatial tunability  laser-mode conversion  bandedge lasing 
學科別分類
中文摘要 本論文成功製作出可空間調控整個可見光區波長之光子能隙及雷射元件。此元件是以製作膽固醇液晶模板技術為基礎,經由四個製作階段:聚合前、聚合後、洗掉後,以及重灌後所完成。實驗結果顯示此元件之光子能隙調控範圍幾乎可涵蓋整個白光區域(409 nm至775 nm)。且在回灌摻雜兩種雷射染料之向列型液晶後,由於染料分子間可藉由螢光共振能量轉移效應,使得產生之螢光頻譜可分佈於整個可見光區,在適當能量適當波長之脈衝光激發下可在樣品的不同位置產生波長為接近連續變化且分佈從藍光區一直到紅光區之雷射輸出。此外,此空間調控雷射元件在不同溫度下可於單模態能隙邊緣雷射與多模態能隙雷射之間轉換。雷射模態轉換關鍵在於模板內注入奈米孔洞之液晶是否具有雙折射性,當模板內回填之染料摻雜向列型液晶處於向列態時,由於模板內不同孔洞內的液晶排向可能稍微不一致,使得樣品有效折射率不同位置稍微不同,導致光子能隙邊緣雖不同位置有小幅度波動,而產生多模態能隙邊緣雷射;當回填液晶加熱到處於各向同性態時,由於液晶在不同奈米孔洞內的折射率都相同,故不同位置之光子能隙邊緣固定,進而產生單模態能隙邊緣模式雷射輸出。
除了製作單層膽固醇液晶模板之外,本論文也實現製備具有雙層相反旋性之膽固醇液晶模板結構之合成元件,此元件不但具有可高反射整個白光區光子能隙,並且能有效地同時利用右圓與左圓偏振螢光並經由重灌的雙層相反旋性之膽固醇液晶模板共振腔結構轉換成成具有雙旋性圓偏振之雷射輸出,故可降低雷射能量閥值。由於本元件具有許多優勢,如結構穩定、可雷射模態轉換、光子能隙與雷射波長可調範圍寬廣及可左右圓偏振雷射同時輸出等特性,相信在未來具有相當潛力可應用於光電子、光通訊、以及顯示器等領域。
英文摘要 A spatially tunable photonic band-gap (PBG) and laser device, whose tuning range can almost cover the entire visible region, is successfully developed in this study through the cholesteric liquid crystal (CLC) polymer template refilling technique. The device is fabricated in four stages, namely, the before-curing, after-curing, after-washing-out, and after-refilling stages. Experiment results show that the tunable spectral range for the PBG of the device covers nearly the entire visible region (409 nm to 775 nm). After refilling the template with a dye-doped nematic LC (DDNLC), which includes two types of dyes, a broad fluorescence spectrum that almost covers the entire visible region is obtained via Förster energy transfer effect, resulting in a spatially tunable laser that can lase from the blue to the red regions (483.18 nm to 633.73 nm). In addition, the spatially tunable laser mode between the single- and the multi-mode bandedge laser modes can be converted by varying the temperature. The key to the laser-mode conversion is the birefringence of the refilled LC. When the DDNLC that is refilled into the nanopores of the template is in the nematic phase, the effective refractive indices of the LCs become slightly different across various nanopores of the template on the pumped region. These cause multiple domains with slightly reduced PBG and band edge that, in turn, lead to multi-mode bandedge lasing emission. After heating the refilled LCs to the isotropic phase, the refractive indices in these nanopores at various positions of the template become identical, resulting in the single-mode bandedge lasing emission.
In addition to the DDNLC-refilled single CLC template device, the fabrication of a spatially tunable DDNLC-refilled merged cell, which consists of two CLC templates with right and left handednesses, is also achieved in this study. This merged cell is hyper-reflective in the entire visible region and can provide an efficient resonance for either right- or left-circular fluorescence for lasing emission, thus leading to a lower lasing threshold compared with that of the refilled single CLC template cell. The refilled merged laser device possesses many advantages, such as high stability, lasing-mode convertibility, wide tunabilities in both lasing wavelength and PBG, and simultaneous right- and left-circularly polarized lasing output. Thus, the merged laser device has a high potential for applications in the fields of photonics, optical communications, and display.
論文目次 摘要 I
Abstract II
Acknowledgements IV
Contents V
List of Figures VIII
List of Tables XV
Chapter 1 Introduction 1
Chapter 2 Liquid Crystals 5
2-1 Introduction to Liquid Crystals 5
2-2 Classification of Liquid Crystals 6
2-2-1 Lyotropic Liquid Crystals 6
2-2-2 Thermotropic Liquid Crystals 7
2-3 Physical and Electrooptic Characteristics of Liquid Crystal 11
2-3-1 Birefringence and Optical Anisotropy 11
2-3-2 Dielectric Anisotropy 14
2-3-3 Elastic Continuum Theory of Liquid Crystals 16
Chapter 3 Cholesteric Liquid Crystal and Polymer Templates 18
3-1 Optical Properties of Cholesteric Liquid Crystals 18
3-2 Factors Influencing on Helical Pitch 20
3-2-1 Temperature 20
3-2-2 Concentration of chiral dopants 21
3-2-3 Magnetic and Electric Fields 21
3-2-4 Optical Fields 23
3-3 Cholesteric Liquid Crystal Polymer Templates 24
3-3-1 Backgrounds of Cholesteric Liquid Crystal Polymer Templates 24
3-3-2 Fabrication of LC polymer template 25
3-4 Tunability of Cholesteric Liquid Crystal Polymer Templates 27
3-4-1 Electric Field 27
3-4-2 Thermally-induced multicolored hyper-reflective cholesteric liquid crystals 29
3-4-3 Optical Field 31
Chapter 4 Laser mechanism 33
4-1 Basic Principles of Laser 33
4-1-1 Interactions between Photons and Atoms 33
4-1-2 Population Inversion 36
4-1-3 Basic Operation of Laser 38
4-2 Mechanism of Distributed Feedback Lasing Emission 39
4-3 Photonic Bandedge Lasers of Cholesteric Liquid Crystals 40
4-4-1 Forster Resonance Energy Transfer 42
4-4-2 Liquid Crystal Dye Laser Covering Visible Range 44
4-4-3 Spatially Tunable Cholesteric Liquid Crystal Dye Laser Covering a Full Visible Range 47
Chapter 5 Sample Fabrication and Experimental Setups 49
5-1 Materials 49
5-1-1 CLC Polymer Templates 49
5-1-2 Refilled Materials 52
5-2 Sample Fabrication 54
5-2-1 Fabrication of Empty Cells 54
5-2-2 Mixture for Fabrication of Single CLC Polymer Template 56
5-2-3 Fabrication of DDNLC-Refilled Single CLC Polymer Template Cells 58
5-2-4 Fabrication of DDNLC-Refilled Merged CLC Polymer Template Cells 61
5-3 Experimental Setups 62
Chapter 6 Results and Discussion 65
6-1 Spatially-Tunable PBG of DDNLC-Refilled CLC Polymer Template Sample 65
6-2 Spatially-Tunable DDNLC-Refilled CLC Template Laser 68
6-3 Spatially-Tunable Laser in DDNLC-Refilled Merged CLC Template Cell with Opposite Handednesses 81
6-3-1 Spatially-Tunable PBG of DDNLC-Refilled Merged CLC Template Cell with Opposite Handednesses 82
6-3-2 Spatially-Tunable Lasing Emissions for DDNLC-Refilled Merged CLC Template Cell 84
6-3-3 Lasing Features of DDNLC-Refilled Merged CLC Template Cell with Opposite Handednesses 88
Chapter 7 Conclusion and Future works 96
7-1 Conclusion 96
7-2 Future works 97
References 98
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