液態晶體被廣泛應用在可見光波段之光學元件上，但在兆赫波段之元件卻相當缺乏。本實驗室已成功製作出兆赫波段下電控液晶相位延遲器，但是此元件的厚度較厚，使得反應時間較慢。本論文利用雙頻液晶不同頻率擁有不同介電異方性的特性來改善元件的反應時間。
由實驗結果發現利用雙頻液晶所製作的兆赫波段下電控液晶相位延遲器擁有很快的turn back反應時間，但turn on反應時間卻相當慢。經由配向膜和操作頻率的改進，成功利用垂直配向的雙頻液晶、操作頻率在500Hz和100kHz之間切換，可增快兆赫波段下電控液晶相位延遲器的反應時間達5﹪。

Liquid crystal (LC) has been widely used for optical components in visible light range. However, it is short of optical components in the terahertz (THz) frequency range. Our group had demonstrated an electrically controlled liquid crystal THz phase shifter. Because the LC layer of these THz components is thick, the response time is very slow. In this thesis, the response time is improved by using dual-frequency liquid crystal with different dielectric anisotropy at different applying frequencies.
In this work, the dual-frequency liquid crystal THz phase shifter has been demonstrated. The turn back response time of this THz phase shifter is fast, but the turn on response time is very slow. By using switching frequency between 500Hz and 100kHz in a homeotropically aligned dual-frequency liquid crystal THz phase shifter, we have successed in reducing the response time up to 5 ﹪.

摘 要 i
ABSTRACT ii
致謝 iii
目錄 iv
表目錄 vi
圖目錄 vi
第一章 緒論 1
1-1實驗動機與目的 1
1-2液態晶體簡介 3
1-3雙頻液晶特性簡介 4
第二章 基本原理 5
2-1加電壓之穿透率 5
2-2兆赫波量測系統介紹 7
2-3兆赫波段下的折射率分析 10
2-4相位延遲(Phase shift) 13
2-5反應時間 15
2-6反應時間的量測方法 18
第三章 樣品製作 19
3-1液晶樣品的製作 19
3-2清洗玻璃 19
3-3鍍配向膜 20
3-3-1鍍水平配向膜 20
3-3-2鍍垂直配向膜 21
3-4磨刷配向膜 21
3-5切割間隙物(Spacer) 22
3-6封裝液晶樣品盒 22
第四章 實驗結果與分析 23
4-1調變頻率之加電壓量穿透率求Ki 24
4-2兆赫波段下雙頻液晶的折射率ne、no 28
4-3相位延遲實驗結果 32
4-3-1雙頻液晶(MLC-2048)的相位延遲 34
4-3-2正型液晶(E7)的相位延遲 36
4-3-3正型液晶(MDA-00-3461)的相位延遲 37
4-4反應時間實驗結果 38
4-4-1 三種液晶反應時間的結果與比較 40
4-4-2 不同的表面配向膜對反應時間的影響 45
4-4-3 改變操作頻率對反應時間的影響 49
4-4-4 反應時間量測的結果和理論之比較 53
第五章 結論與未來展望 55
5-1結論 55
5-2未來展望 56
參考文獻 57

[1] B. B. Hu and M. C. Nuss, “Imaging with terahertz waves”,Opt. Lett. 20, 1716-1718 (1995)
[2] A. J. Fitzgerald, E. Berry, N. N. Zinovev, G. C. Walker, M. A. Smith,and J. M. Chamberlain, “An introduction to medical imaging with coherent terahertz frequency radiation”,R67(2002)
[3] C.-F. Hsieh, T.-T. Tang, H.-L. Chen, R.-P. Pan,and C.-L. Pan, “Voltage-controlled liquid-crystal terahertz phase shifter and quarter-wave plate”, Opt. Lett., 31, 1112(2006)
[4] K. Sakai, “Terahertz Optoelectronics”.( Berlin: Springer, 2005)
[5] Dongfeng Liu and Jiayin Qin,“Carrier dynamics of terahertz emission from low-temperature-grown GaAs”, APPLIED OPTICS,42, 3678(2003)
[6] P. K. Benicewicz, J. P. Roberts, and A. J. Taylor ,“Scaling of terahertz radiation from large-aperture biased photoconductors”, J. Opt. Soc. Am. B, 11,(1994)
[7] M. Van Exter, Ch. Fattinger, D. Grischkowsky, “Terahertz time-domain spectroscopy of water vapor” , Opt. Lett., 14, 1128 (1989)
[8] C. W. Chen, T. T. Tang, S. H. Lin, J. Y. Huang, C. S. Chang, P. K. Chung, S.T. Yen, and C. L. Pan, “Optical properties and potential applications of ε-GaSe at terahertz frequencies”, J. Opt. Soc. Am. B, 26, 9 (2009)
[9] Tsung-Ta Tang, “Study on the Alignment Properties of Liquid Crystal on the Substrate with Anodic Aluminum Oxide Films and the Grooved PDMS Substrate”, 國立交通大學光電工程學系博士論文(2009)
[10] S. Chandrasekhar, “Liquid Crystal”, 2nd ed. Cambridge, New York,(1992)
[11] Xiangyi Nie, Haiqing Xianyu, Ruibo Lu, Thomas X. Wu, and Shin-Tson Wu, “Pretilt Angle Effects on Liquid Crystal Response Time”, Journal of Display Technology, 3, 280(2007)
[12] D. W. Berreman, “Solid Surface Shape and the Alignment of an Adjacent Nematic Liquid Crystal”, Phys. Rev. Lett. 28, 1683–1686 (1972)
[13] J. M. Geary, J. W. Goodby, A. R. Kmetz, and J. S. Patel, “The mechanism of polymer alignment of liquid‐crystal materials”, J. Appl. Phys. 62,4100 (1987)
[14] C. P. Chen, S. P. Preman, T.-H. Yoon, and J. C. Kim, “Dual-mode operation of dual-frequency liquid crystal cell by horizontal switching”, Appl. Phys. Lett. 92, 123505(2008)
[15] A. B. Golovin, S. V. Shiyanovskii, and O. D. Lavrentovich, “Fast switching dual-frequency liquid crystal optical retarder, driven by an amplitude and frequency modulated voltage”, Appl. Phys. Lett. 83, 3864(2003)
[16]李曾申,“雙頻液晶中分子轉動與電場頻率相依特性之研究”,國立中正大學光機電整合工程研究所碩士論文(2006)
[17] Cho-Fan Hsieh, “Design and Measurement of Liquid Crystals Devices in Terahertz Frequency Range”, 國立交通大學電子物理學系博士論文(2009)
[18] Wei Lee, Chun-Yu Wang, and Yu-Cheng Shih, “Effects of carbon nanosolids on the electro-optical properties of a twisted nematic liquid-crystal host”, Appl. Phys. Lett. 85(2004)
[19] 潘鴻至,黃啟炎, “TN液晶盒摻雜奈米碳管之光電響應研究”