In this study, we research the characteristic of light in the waveguide with etched ITO channels. The anisotropic of liquid crystal induces the index of reflection changed while applying alternative voltage. The etched ITO electrode will become waveguide in cell by applying alternative voltage. We observe the characteristic of light with different number of channels. Single ITO channel results graded type reflection index distribution, and it is similar to graded type optical fiber. We find that the laser beams will induce coupling in channels with many etched ITO channels.

We propose to develop a voltage-controllable multi-guide directional coupler in a planar nematic liquid crystal cell. The ITO grating-like electrodes are fabricated by the etching technique, and the director of liquid crystals will be aligned to the direction of applied electric field. Owing to the uniaxial property of liquid crystals, the difference of refractive index between two neighboring channels is increased with the applied voltage. Therefore, the coupling efficiency among grating-like multi-guide is also increased with the applied voltage. By using the combination of microscope and CCD system, the dynamic coupling can be observed under the distribution of grating-like electric field. The propagation of light in each channel can be selected by the controllable voltage between the electrodes of the individual channel. The intensity distribution of coupling in the transverse direction can be obtained by analyzing the image captured from the microscope and CCD system.

We hope to achieve the goal of improving molecule nature of the liquid crystal by change the functional group or the symmetry of the molecule. In the thesis, the derivatives of dibenzophenazine are synthesized and their mesogenic properties are investigated. Polarised optical microscopy (POM) and differential scanning calorimetry (DSC) studies show all these compounds to exhibit a very wide mesophase range. These mesophases are identified as columnar hexagonal phases by X-ray diffraction (XRD).

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Optical measurement is a very important science in present times. Generally, optical interference is applied in precise measuring. In this thesis, we use the opto-electric properties of liquid-crystal layers and the phase-shifting shearing interferometer will be applied. Clear patterns should be figured when measuring optical properties traditional interferometers. A new interferometer called phase-shifting shearing interferometer was developed recently. It is not necessary to appear clear patterns in measurements. In application to this interferometer, the phase information got by way of shifting the reference lens that can control phase differences. Phase controlled in thus method is mostly by the step motor or the PZT installation. Now we replace this installation by liquid-crystal layers since the accuracy of liquid-crystal layers controlled by voltage is better than the mechanical installation. The measuring precision is improved wide. In this paper, we study the optical properties under the application both DC and AC voltage to a series of thickness of the liquid-crystal layer, and the suitable condition of liquid-crystal layers to apply to the phase-shifting shearing interferometer.

Abstract There are three parts in this paper. The first, we study the mechanism of soliton in nematic liquid crystal (NLC), molecules of NLC will be rotated easily by optical field while we apply an external electric field. Then the effective refraction index is changed. The light beam in NLC will create spatial soliton by producing the effect of self-focusing to balance the diffraction. Second, we study the interaction between solitons. One soliton will create a potential well of refraction index. The other one will be attracted in the potential well. These two solitons propagate in the form of spiral, if the separated distance and the angle are suitable. And the third, we observe the phenomenon with probe beam in the path of soliton. The path of the soliton forms a channel like a wave guide. The probe beam insert into the path of the soliton with different angles. The probe beam collides with the soliton in the proper range of angles will follow its path.

In the present study we investigate the use of polymer liquid crystal for holographic recording. Holographic patterns were produced by means of two-beam interference using an Ar+ laser. The polymer liquid crystal thin layers were prepared by injecting RM257 into cells through capillary action at 140¢XC where the RM257 mesogen was in isotropic state. By exposing the mesogenic layer to the laser interference patterns, we have successfully imprint holographic patterns into RM257 thin layers. In order to reach the best alignment, the intensity of laser beam, sample temperature, the spacial period and exposure time must be properly set.

RM257 consists of photoactive mesogenic end groups. By in situ polymerization of the mesogen, the optical information can be recorded into RM257 thin film. In this study, the RM257 thin films were exposed to a holography irradiation created using an Ar+ laser. The holography patterns have been found to be imprinted into the polymer thin films. The refractive efficiency can be increased when the sample temperature is properly controlled during holography irradiation. The work was started from the use of two beam interferometry, and further to use three beam interference. The molecular arrangement in the resultant polymer film and their function in optical modulation have been studied.

Discotic liquid crystal (LC) molecules have a structure that is comprised of a rigid aromatic core with side-chain molecules. Intermolecular £k-£k interactions force the tube to orient and form one-dimensional columnar structures which can act as molecular wires. In recent years, discotic LC molecules have been deposited on surfaces from solution to create the solid-state electronic elements used widely in solar cells, organic light-emitting diodes (OLED), organic photovoltaic, field-effect transistors (FET), and molecular wires. Different stacking morphologies can change the behavior of the material and thus will have potential for different applications. Hence, effective control over the stacking of the LC molecules on surfaces is important for optimizing the performance and effectiveness of LC-based electronic components and devices. This study has focused on LC molecules with acid and ester containing functional groups, and how these groups influence the stacking behavior on surfaces. Here, the self-aggregation behavior of the discotic LC ester in solution was investigated quantitatively by determining the concentration dependence of the 1H NMR chemical shifts. Our results showed that discotic LC ester has different self-aggregation behavior in CH2Cl2, THF and Benzene organic solvents. THF solvent showed the highest degree of aggregation, followed by CH2Cl2, and then benzene. We also studied the effects of (i) different solvents (THF, CH2Cl2, and Benzene), (ii) different surface functional groups (OH, CH3, NH2, SH, and diphenyl), and (iii) temperature, on the stacking phenomenon of discotic LCs on silicon surfaces. In part (i) our results showed that discotic LC ester had different morphologies on silicon surfaces due to differences in solvent polarity and evaporation rate. In part (ii), we observed that different surface functional groups did not affect the intermolecular interaction between either the ester- or acid-type LC molecules. For the acid-type LC, strong hydrogen bonding interactions with the surface caused the crystals to form rod-like fiber structures. However, the ester-type LC molecules formed ribbon-like stacks on the surfaces. For functional groups containing CH3 (more hydrophobic surfaces), we observed no LC molecules on the surface, which was likely due to the poor wettability of the solvents on OTS. In part (iii), we observed that both acid and ester discotic LCs formed large aggregates on the surfaces due to a ¡§ripening effect¡¨. With increased temperature, the molecules were able to overcome the wetting interaction with the surface and self-aggregate into three-dimensional clusters.

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