液晶/單體中光聚合效應的圖案轉換觀察和由Z-scan方法鑑定非線性光學現象;Observation of pattern transition through photo-polymerization and non-linear optical effect characterized by Z-scan in liquid-crystal-monomer mixture

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/54288

Title:	液晶/單體中光聚合效應的圖案轉換觀察和由Z-scan方法鑑定非線性光學現象;Observation of pattern transition through photo-polymerization and non-linear optical effect characterized by Z-scan in liquid-crystal-monomer mixture
Authors:	陳大農;Chen,Ta-nung
Contributors:	照明與顯示科技研究所
Keywords:	光聚合效應;Z-scan;液晶/單體;非線性光學;photo-polymerization;non-linear optical effect;Z-scan
Date:	2012-07-19
Issue Date:	2012-09-11 18:43:12 (UTC+8)
Publisher:	國立中央大學
Abstract:	在這篇論文中，我們提出利用超快脈衝雷射:Ti:sapphire可提供高電場，導致混合物中的液晶/單體相分離，進而產生微波導，而微波導的形成是因為單光子和雙光子吸收，而使得液晶混合物中的單體聚合成多體聚合物。在液晶/單體混合物之光聚合實驗中我們觀察到圖案轉換，在波長360 nm雷射光曝照下，雷射掃瞄速度越慢則混合物之聚合效應越強，其微波導寬度越寬。在波長720 nm雷射光引致的雙光子效應下，當光電場偏振方向與雷射掃描方向垂直時，所形成的聚合圖案是像弦波式的圖形。利用模擬驗證，微波導的形成是由於光聚合效應和相分離效應互相平衡的結果，而弦波式的圖形是由雙光子聚合效應與混合物流動效應的競爭所產生。另外，我們以z-scan的實驗，來探討高脈衝雷射聚焦點之液晶盒內部的分子排列變化，以交叉驗證相分離現象，以及探討其引致的非線性克爾效應所產生的透鏡現象，並且計算得到材料的非線性折射率。In this thesis, we propose using ultra-fast Ti:sapphire laser pulse to form high optical field, which causes phase separation in liquid crystal/ monomer mixtures. The micro-waveguide is formed because the one-photon and two-photon absorption and the monomer molecules are linked into polymer matrix. The pattern transition is observed in photo-polymerization experiment. Upon 360 nm laser exposure, the lower the laser scanning speed, the wider the micro-waveguide. Two-photon absorption is started upon 720 nm laser exposure, and serpentine pattern is induced when the optical polarization is perpendicular to the laser scanning direction. Simulation shows the micro-waveguide formation is a result of the balance between photo-polymerization and phase separation, while the serpentine pattern is a result of competition between two-photon-polymerization and convection force in liquid-crystal-monomer mixture. In addition, we use z-scan experiment to investigate molecular orientation and distribution at the focal point of laser pulse. The phase separation phenomenon is verified. We also study the induced resulting lens effect due to nonlinear optical Kerr effect, and estimate the nonlinear coefficients of materials.
Appears in Collections:	[Institute of Lighting and Display Science ] Electronic Thesis & Dissertation

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