兆赫波段下可調式電控液晶相位延遲器反應時間之改善

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﹪。

關鍵字

液態晶體；相位延遲器；兆赫波；反應時間

並列摘要

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 ﹪.

並列關鍵字

Liquid crystal ； phase shifter ； THz wave ； response time

參考文獻

[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)

國際替代計量

兆赫波段下可調式電控液晶相位延遲器反應時間之改善

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