本論文透過膽固醇液晶作為兆赫波段相位調控元件，具備無偏振性質並且在1THz超過一個2π的相移，並探討此材料在兆赫波段的行為與特性。由BL006向列型液晶加入旋光材料S811製成膽固醇液晶，利用液晶在兆赫波段不具散射特性及與兆赫波偏振方向無關的行為製作此波段光學調控元件，使用電壓拉動液晶分子使膽固醇液晶的折射率在focal conic texture與homeotropic texture中變化，提高液晶樣品厚度增加相移，並且由旋光材料濃度控制液晶pitch大小，改善元件需要的外加電場成功製作出此波段下的相位調控元件。此外我們使用THz–TDS系統觀察到以不同加電壓的方式下，兆赫波段下BL006膽固醇液晶在0V具有的另一個穩態。

In this thesis, we propose and demonstrate a simple and precise method for
measuring mm scaled cell gap by using terahertz time domain spectroscopy
(THz-TDS) system. This method allows us to measure the cell gap from 15mm to
1.5mm. In addition, the accuracy of measured thickness for the proposed method is
also discussed and analyzed. Meanwhile, a nematic liquid crystal BL006 with
birefringence as high as 0.27 in THz frequency range and its optical properties of
cholesteric liquid crystal (CLC) as mixing chiral materials are investigated and
reported. The ordinary refractive index and average effective refractive index at 20oC
are from 1.52 to 1.56 and from 1.61 to 1.64, respectively, in THz frequency ranging
from 0.2 THz to 1.4THz. In addition, we also demonstrate that cell filled with CLC is
with polarization independent property for THz radiation. Through the 5mm cell filled
CLC with diluted concentration of the dopant chiral material for decreasing the
critical voltage, an electric controlled polarization independent phase shifter with the
modulation depth exceeding 2pi is demonstrated. Furthermore, we also investigate the
driving field dependence of phase retardation and discuss the reliability.

論文審定書．．．．．．．．．．．．．．．．．．．Ⅰ
誌謝．．．．．．．．．．．．．．．．．．．．．．Ⅲ
中文摘要．．．．．．．．．．．．．．．．．．．．Ⅳ
英文摘要．．．．．．．．．．．．．．．．．．．．Ⅴ目錄．．．．．．．．．．．．．．．．．．．．．．Ⅵ
圖次．．．．．．．．．．．．．．．．．．．．．．Ⅶ
第一章 緒論．．．．．．．．．．．．．．．．．．．1
第二章 兆赫波相位調變方式與實驗系統介紹．．．．．3
2.1 兆赫波相位調變方式．．．．．．．．．．．．．4
2.2 兆赫波時域解析光譜系統．．．．．．．．．．．7
2.3電光晶體取樣法．．．．．．．．．．．．．．．11
第三章 膽固醇液晶在兆赫波段之光學性質量測方式．15
3.1 膽固醇液晶簡介．．．．．．．．．．．．．．．16
3.2 兆赫波段之多波長干涉法量測液晶盒厚．．．．．20
3.3 THz-TDS 分析液晶在兆赫波段之光學性質與步進馬達誤差探討．．．．．．．．．．．．．．．．．．．25
3.4 結論．．．．．．．．．．．．．．．．．．．．28
第四章 兆赫波段電控無偏振特性相位調控器製作．．29
4.1 膽固醇液晶螺距對於臨界偏壓大小的改善．．．．30
4.2 BL006 膽固醇型液晶在兆赫波段之光學性質．．34
4.3 偏振獨立2π相位調變器．．．．．．．．．．．36
4.4膽固醇液晶在不同電壓下的行為與相位改變．．．37
4.5 結論．．．．．．．．．．．．．．．．．．．．40
第五章 總結與未來展望．．．．．．．．．．．．．41
參考文獻．．．．．．．．．．．．．．．．．．．43
Publication list．．．．．．．．．．．．．．．．．45

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