The dynamic pattern formation and the beam-steering characteristics of cholesteric gratings were studied. Films with a planar cholesteric texture and various thickness to pitch length ratios (d/p) were fabricated. An optical microscope was used to observe the stripe patterns of the cholesteric gratings formed by applying a voltage to the planar films. The micrographs showed that the cholesteric gratings were formed in two different ways, depending on the sample's d/p ratio. For samples with 1/2≤d/p≤1.0, the grating stripes simultaneously appeared across the whole sample, and the contrast of the stripes increased with time during formation. For films with d/p≥1.5, the stripes were initiated near the edges, and near the defects on the substrates, and then slowly extended to the whole sample along the rubbing direction. The diffraction measurements showed that the diffracted beams could be steered either electrically or optically only for the latter type of film. These results can be well explained theoretically.

We design a dual-view liquid crystal display (DVLCD) which display two different images in the left and right viewing directions simultaneously. The main-pixel of the DVLCD comprises the right sub-pixels (RSPs) and the left sub-pixels (LSPs). The LCs in the RSPs and the LSPs have the opposite rotation directions, which are controlled by the inclined electric fields provided by the patterned electrodes. Addressing the RSPs and LSPs with the voltages having different polarities effectively decreases the maximum operation voltage of the DVLCD. The proposed DVLCD is free of the complicate multiple-step rubbing and shadow mask treatments, and hence has the advantages of low cost and easy fabrication.

The alignment characteristics of the homogeneous liquid-crystal (LC) cell rubbed multidirectionally were examined. LC molecules align along an axis between two different rubbing directions. The rubbing strength, cell thickness, and ambient temperature markedly influence the final orientation of the LC molecules. The orientation of the LC molecules and the transmission of a multidirectionally rubbed cell can be controlled according to the ambient temperature. A model that assumes substrate with various groove densities along various rubbing directions is presented. The elastic constant and the viscosity of the LC molecules are found to be the key factors that influence the orientation of the LC molecules.

The electro-optical responses of the in-plane switching (IPS) dual-frequency liquid crystal (LC) cell operated with the amplitude-modulation method and the frequency-modulation method were investigated. The obtained results reveal that the electric torque exerted to the LCs and the strong anchoring energy produced from the rubbed polyimide dominate the reorientation of the LCs. With the frequency-modulation method, the generated electric torque combined with the strong surface anchoring energy give the cell a very short fall time, which is independent of the applied frequency. A new waveform composed of the amplitude modulation and the frequency modulation of the supplied voltage-pulse to achieve a fast responding IPS LC cell is proposed. The obtained response time is much less than that of the conventional amplitude-modulation method.

We report the results obtained from the studies of cholesteric gratings doped with a dichroic guest-host dye, G206. First, a dye-doped planar cholesteric texture was switched to a fingerprint texture. Using the pump (Ar+ laser)–probe (He–Ne laser) technique, we then studied the diffraction characteristics of the Raman-Nath cholesteric grating. The results showed that the diffraction efficiencies of the first- and second-order diffracted beams decreased and increased, respectively, with increasing power of the pump beam, while those of the zeroth order remained unchanged. In addition, the diffracted beams can be steered using the pump beam. We propose a model based on the thermal effect resulting from the dye absorption of the pump beam. It explains the experimental results qualitatively well.