膽固醇液晶相位光柵可藉由適當的液晶盒厚度(d)及膽固醇液晶螺距(p)比值(d/p)下外加電壓下形成，其最大優點為可藉由外加電場等方式調控其光柵週期，因此在光導向(Beam steering)之角度控制上有很好的應用。如何在不需持續外加電壓下維持膽固醇液晶光柵結構是其中一個重要研究方向。在本論文中利用自組成材料十二氫氧基硬酯酸((12-Hydroxystearic Acid)，HSA) 摻入膽固醇液晶裡，藉由HSA分子間的氫鍵可穩固液晶排列的機制，製作一不需持續外加電壓即可穩固存在並保有可輕易調制週期特性之多重穩態(Multi-stable)膽固醇液晶光柵。
首先，我們探討不同HSA濃度對於穩固膽固醇液晶光柵之影響，選擇出適當HSA的濃度參數3 wt％製作凝膠穩固之膽固醇液晶光柵。我們對此製作出之光柵元件，研究其穩固前後之繞射角度及繞射效率等特性差異，並研究此液晶光柵穩固後對外加電場90 V的抵抗能力及在兩週內之持續穩固特性。實驗結果顯示可利用HSA分子氫鍵加熱解開的特性，加熱後利用不同電壓下所形成不同週期的膽固醇液晶光柵，並且穩固改變後之週期，成功製作出多重穩固之膽固醇液晶光柵，並研究重複解開再穩固之操作10次後，對繞射特性之影響，由結果可得HSA材料並不會因穩固操作次數增加其穩固效果降低。
藉由自組成材料HSA的氫鍵作用力穩固液晶的排列，我們成功製作出多重穩態及可調的光柵元件，此液晶光柵元件製作簡單且方便使用，不需外加電場即可維持光柵結構，且可穩固在電場調整下之各種週期，作為光導向元件上具有相當的應用潛力。

A cholesterol liquid crystal (CLC) grating is obtained by using a CLC cell having an appropriate ratio of the cell gap (d) and natural helix pitch (p) under a suitable applied voltage. The most advantage is that its period can be tuned under an applied field. Therefore, it has a potential for use as a beam steering grating for tunning the diffraction angle. The motivation of this thesis is to investigate a CLC grating that can be stabilized without applying voltage. In this thesis, we demonstrate a multi-stable CLC grating, which can be stabilized and modulated the period easily using 12-Hydroxystearic Acid (HSA) doped in CLC. The hydrogen bonds of HSA molecules can stabilize the alignment of LC molecules.
Firstly, we study the effect of different concentrations of HSA on the stabilization of a CLC grating, and find that the optimum concentration of HSA to stabilize a CLC grating is 3 wt％. Experimentally, a CLC grating device is fabricated, and its diffraction angle and diffraction efficiency are studied before and after stabilization. Moreover, we investigate the stabilization against the voltage applied to the device and stabilization duration. Finally, by using the feature of the hydrogen bonds in HSA molecules being unlocked by heating, the period of a CLC grating can be changed under different applied voltages, then heating and re-stabilized after cooling. We demonstrate a multi-stable CLC grating, and study the recycle times of HSA under repeated heating-cooling procedure, which influences the diffraction characteristics. The results show that the stabilization of HSA is independent of repeat times.
We demonstrate the fabrication of a multi-stable and tunable CLC grating using the self-assembly material, HSA, which possesses hydrogen bonds and can stabilize a CLC grating without applying a voltage. The fabrication of a CLC grating is simple, and the device is very convenient to be used. Thus, the device has high potential for application in beam steering.

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