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研究生： 顏君玲
Yen, Chun-Ling
論文名稱： 利用PEDOT電極之液晶太赫茲空間光調制器之研究
Liquid-Crystal-Based Terahertz Spatial Light Modulator Using PEDOT as Electrodes
指導教授： 潘犀靈
Pan, Ci-Ling
口試委員: 林怡欣
Lin, Yi-Hsin
施宙聰
Shy, Jow-Tsong
楊承山
Yang, Chan-Shan
學位類別： 碩士
Master
系所名稱： 理學院 - 物理學系
Department of Physics
論文出版年： 2018
畢業學年度： 106
語文別： 英文
論文頁數： 76
中文關鍵詞： 兆赫波 、液晶 、空間光調制器 、相位移 、中間層
外文關鍵詞： Terahertz, Liquid Crystal, Spatial Light Modulator, phase shift, intermediate layer
相關次數： 點閱：2  下載：0 
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    • Poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) 此種有機電極材料在兆赫(太赫茲)頻域下有很高的穿透率，穿透率可高達約90%。在本工作中，我們使用以簡單的旋塗(spin-coating)製程製作之PEDOT/PSS薄膜作為以液晶為基底的兆赫(太赫茲)光電元件之透明電極。
    我們設計了一種易於製作、低成本、符合經濟效益的空間光調制器(SLM)，並在PEDOT/PSS上製作空間光調制器的像素圖案，空間光調制器的每一個像素均為扭曲向列型液晶盒。
    在本論文中，我們使用兆赫時域光譜技術(THz-TDS)進行量測分析，比較三種不同光學異向性(雙折射率)的液晶，分別為MDA-00-3461，TD101-146以及mixture-W1825所製作不同厚度的相位調制器的相位移程度，使用高雙折射率液晶mixture-W1825 (其在0.2到1.2THz頻寬間所量測出的ne~2.03，no ~1.65，△n~0.37)，只需要250μm厚度即可達到在1.2THz的95.2o的相位移。
    此外，我們引入了一種聚合物薄膜置於厚的兆赫液晶盒中間，作為中間層的均勻配向層，以提升響應速度和達到更高的相位以及振幅調製。在本工作中，我們實驗發現一500μm厚的MDA-00-3461液晶相位調制器，相位移從94o增加到111°，此外振幅調制頻寬從0.2-0.6 THz擴展到0.2-0.9 THz，響應速度之上升時間由1.63秒縮短至1.06秒，下降時間由>100秒縮短至40秒。

    An organic electrode material, poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) exhibits as high as transmittance 90% in the range 0.2 - 1.2 THz. In this work, spin coated PEDOT/PSS thin films use as transparent electrodes for various liquid crystal (LCs) based Terahertz (THz) devices.
    We design a 3 × 3 pixels PEDOT/PSS pattern for spatial light modulator (SLM), which is simple device fabrication step and low cost for economic effective, each pixel of the SLM is a twisted nematic (TN) LC cell.
    In this thesis included, evaluation of optical anisotropy properties of three different kinds of LCs, such as MDA-00-3461, TD101-146 and mixture-W1825 using THz time-domain spectroscopy (THz-TDS). In addition, we investigated the phase shift phenomena of these three types of LCs cell at different thickness. We observed that mixture-W1825 LCs be excellent candidate for THz devices application (measured values of ne, no and △n are 2.03, 1.65 and 0.37, respectively at 0.2 - 1.2 THz). The highest phase shift achieved 95.2o at 1.2 THz with injected mixture-W1825 LCs into 250 μm thick cell only.
    Besides that, we introduced a polymeric thin film as an intermediate layer in between a thick THz LCs cells to improve the alignment properties for faster response and higher phase as well as amplitude modulation. The phase shift increased from 94o to 111o, amplitude modulation range increased from 0.2-0.6 THz to 0.2-0.9 THz with intermediate based LCs cell (injected LCs MDA-00-3461, 500μm thickness). Also, improve the response time properties of the bi-layers as compare single layer LCs cell. The rise time and fall time is shortened from 1.63 sec to 1.06 sec, and 100 sec to 40 sec, respectively.

    摘要 I Abstract II 致謝 III Table of Contents IV List of Figure VII List of Table XIII Chapter 1 Introduction 1 1.1 Terahertz technology 1 1.1.1 Introduction to terahertz radiation 1 1.1.2 Terahertz time-domain spectroscopy 2 1.2 Liquid crystal 3 1.2.1 Nematic liquid crystal 4 1.2.2 Alignment of liquid crystal layers and twisted nematic (TN) liquid crystal cells 6 1.2.3 High birefringence liquid crystal 8 1.3 Terahertz liquid crystal device 9 1.4 PEDOT/PSS 9 1.4.1 Surface Patterning of PEDOT/PSS 10 1.5 Motivation and objectives 11 1.6 Organization of this thesis 12 Chapter 2 Spatial light modulator 13 2.1 Jones matrix 14 2.2 Single pixel detector 17 2.3 Compressed sensing 18 Chapter 3 Experimental Methods 24 3.1 Terahertz time-domain spectroscopy system 24 3.1.1 Ti: sapphire femtosecond laser system 24 3.1.2 Photoconductive antenna-based THz-TDS 24 3.1.3 Extraction of optical parameters of materials 27 3.1.3.1 Introduction of thick sample 28 3.1.3.2 Introduction of thin sample (thin-film approximation) 29 3.1.3.3 Extraction of complex refractive index 32 3.2 Theoretical phase shift of applied voltage on LC 35 3.3 Sample preparation 36 3.3.1 LC cell and reference cell 36 3.3.2 Substrate with PEDOT/PSS 37 3.3.3 LC-based THz spatial light modulator 38 3.3.4 Intermediate layer 39 Chapter 4 Experimental results and discussion 41 4.1 Transmittance of different conductive film 41 4.2 Optical properties of different liquid crystal 44 4.3 Liquid crystal THz phase shift abilities 48 4.3.1 THz phase shift abilities of different thickness as well as different kinds of liquid crystals 48 4.3.2 Comparison of theoretical threshold voltage and real threshold voltage 59 4.3.3 THz phase shift abilities with intermediate layer 62 4.4 PEDOT/PSS pattern 68 4.5 Simulation results of compressive sensing 69 Chapter 5 Conclusions and future works 72 5.1 Conclusions 72 5.2 Future works 73 Reference 74

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