含有熱敏型旋光劑之膽固醇液晶的溫度效應

Abstract

膽固醇液晶為週期性螺旋結構，具有特定的光子能隙，其中心反射波長取決於膽固醇液晶的螺距與平均折射率。本論文使用一種對熱極度敏感的對掌性分子TCD，摻入膽固醇液晶，它會因為溫度的變化而改變膽固醇液晶的螺距，使我們可以藉由環境溫度來控制膽固醇液晶的反射波段。本研究提出一個特殊方法，將TCD摻雜於雙頻膽固醇液晶中，利用介電加熱的特性改變膽固醇液晶的螺距；藉由施加不同頻率之交流電產生不同介電熱能，控制膽固醇液晶的中心反射波長，達到反射不同色光的功能。最後將摻有TCD的膽固醇液晶應用於具有兩穿透峰的非對稱光子晶體中當作缺陷層，藉由溫度控制膽固醇液晶之中心反射波段可以降低穿透峰之強度。

The photonic bandgap (PBG) nature of a cholesteric liquid crystal (CLC) is determined by the pitch length and the average refractive index of the CLC. In this study we employed a thermosensitive chiral dopant (TCD), characterized by its thermo-induced change in helical twisting power in terms of the handedness as well as the strength, to shift the central reflection band in the spectrum. We demonstrated the local deformation of the CLC helical structure achieved by the dielectric heating effect. We can apply voltage at various frequencies to control the reflection of incident light so to yield many colors such as red, green, and blue. Moreover, a thermally tunable photonic device was further demonstrated using a one-dimensional asymmetric photonic crystal (PC) infiltrated with the thermosensitive CLC as a defect layer. By means of a temperature controller to shift the PBG of the CLC, the transmission peaks can be tuned in the spectrum dominated by the asymmetric PC structure.