Dielectric Relaxation and Dielectric Heating Effect in a Complex Mesophase and Its Photonic Applications
| Autor: | Hsiao, Yu-Cheng, 蕭宇成 |
|---|---|
| Rok vydání: | 2017 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 105 Physics of dielectric heating in complex mesogenic materials especially liquid crystal materials (LCs) has been a complicated topic. The dielectric relaxation process for mesogenic materials is usually chaotic without obvious order. In the last century, the Debye relaxation law, the Cole–Cole equation, the Cole–Davidson equation, the Havriliak–Negami relaxation, and the Kohlrausch–Williams–Watts function have successively been derived from statistical mechanics. In this thesis, we propose a general dielectric relaxation law that unifies the above-mentioned formulas, and we point out that these formulas are only variations of the general formula in different conditions. We applied the general dielectric relaxation formula for derivation of the law of general dielectric heating. This formula is especially suited for describing the easily induced dielectric heating effect in dual-frequency liquid crystals (DFLCs). In this thesis, we further exploit this heating effect in various applications for both nematic DFLCs and cholesteric DFLCs (DFCLCs). For nematic DFLCs, we propose to apply dielectric heating for reducing driving voltage. The dielectric heating results in increased cross-over frequency and also reduces viscosity of DFLCs to allow for lower driving voltage. For DFCLCs, we demonstrated that with dielectric heating, local deformation in cholesteric structure can be achieved. The defect mode in cholesteric structure can be controlled through the degree of dielectric heating. Furthermore, we have shown that cholesteric film with binary chiral agents exhibits electrically tunable selective reflection in visible wavelength. Lastly, we demonstrated the electrothermo-optical effect based on dielectric heating. Comparing to the commonly-known electro-optical effects, the electrothermo-optical effect exhibits anomalous behaviors. Based on dielectric heating, this thesis proposed various practical applications in the field of optics. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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