| dc.description.abstract | In this thesis, we report the asymmetrical optical properties of the three liquid crystal (LC) devices, including (i) cholesteric LC coupled with a quarter-wave plate and a linear polarizer, (ii) dichroic dye-doped 90° twisted nematic LC (DDd-90° TNLC), and (iii) dye-doped TNLC gratings.
In the first part, the incident light passes through the linear polarizer and the quarter-wave plate to form a circularly polarized light which can be reflected by the planar textures of the cholesteric LC (CLC) plate, so the asymmetrical optical property can be achieved. Moreover, the reflection bandwidth and wavelength of the CLC plate is dependent on the angle of propagation direction of the incident light, so the 1D-DIMOS software was also adopted to simulate the limitation of visual angle of this LC device.
In the second part, owing to the rubbing direction of the two glass substrates are perpendicular to each other and the dichroic dyes possess the polarization selective light absorption, the DDd-90° TNLC device has the asymmetrical light absorption property. By measuring the polarization rotation and the polarization selective light absorption, the asymmetrical optical properties of the DDd-90° TNLC are completely demonstrated and analyzed, and the experimental results do agree well with the theoretical analyses. Furthermore, in the final part, we extend such an interesting structure to the dye-doped TNLC grating fabricated through the photoalignment process. According to the experimental results and the theoretical simulation about the polarization rotation properties of the dye-doped TNLC gratings, we demonstrate that the same linearly polarized light (0˚ or 90˚) incident onto the illuminated and the unilluminated surfaces presents the asymmetric diffraction property. Moreover, the diffraction efficiency based on the dichroic dye absorption and phase difference between the two kinds of LC structures of the dye-doped TNLC grating can be tuned electrically. | en_US |