The liquid crystal display on the liquid crystal alignment is known to be influenced by the rubbing strength. In the thesis, in order to figure out the best condition for homeotropic alignment, we add the number of rubbing, which causes the increase of the rubbing strength. In the experiment, we discuss two parts. The first part discusses the relation between polarity and liquid crystal. The instrument used mainly is contact angle measurement system, which measures the contact angle between liquid and sample and calculates the polarity, the dispersion and the surface free energy. In the second part, we change the rubbing strength to analyze the influence of liquid crystal cell. Also, we use the electro-optical measurement to analyze the cell which is fabricated by different rubbing strength. It is at this part that we focus on analyzing the optical texture, transmittance, contract ratio, and sharpness. The sample¡¦s polarity rises as the rubbing strength increases. It is the influence of the liquid crystal pretitle angles that the polarity as well as the liquid crystal cell¡¦s optical property changes. Such changes could be seen in transmittance, contract ratio and sharpness

On account of ¡§the X-ray Phase Problem¡¨, it¡¦s impossible to get the electronic density by inverse Fourier transformation(IFT). And the crystal structure of molecule can¡¦t be solved by IFT. There are many methods to overcome the problem, such as Direct Method, Heavy Atom, and Simulated Annealing. But for macro-molecules, we still face a great challenge due to tremendous computing load. We propose a method by using wavelets to resolve the electronic density. We hope the multiresolution nature of wavelets can reduce the computing load for simulated annealing method.

Currently , the STN-LCD with twist angle of 240 degree is the most popular operation mode . In this thesis , we utilize Photo-Sensitive spacer of TFT-LCD to substitute for the traditional spacer , and apply them in the above mentioned STN-LCD . The traditional spacer were used N2 air to spray on glass substrate by SUS tube . It make light leakage , decrease the transmittance , contrast ratio and aggregate spacer easily . When we pressure on glass and the phenomenon of migration has been found accordingly . It will influence quality of LCD . So we utilize Photo-Sensitive spacer to substitute for the traditional spacer in order to improve the defect . In this thesis , we fabricate different kind Photo-Sensitive spacer of size , shape and area ratio (Photo-Resist (NPS) from Everlight Chemical Industrial Corp) . We utilize Photo Lithography process to form the spacer thickness on insulation layer , and find the best type . In this experiment , the different characteristic of material between traditional spacer and Photo-Spacer were compared . And we utilize different process condition (pressure) and material(LC £Gnd) to discuss the relation . Finally , we proof the advantage of Photo-Spacer apply in STN-LCD .

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Discotic liquid crystal is one kind of self-assembled material, liquid crystal with regular alignment could be applied to many kinds of organic electro-optical devices. This novel discotic liquid crystal polymer DLC-PAM, we used polyacrylamide(PAM) as main chain of the novel discotic liquid crystal polymer DLC-PAM and grafted the discotic liquid crystal monomer Acid-6 onto PAM by chemical synthesis. There were two parts in this study, first we investigated the electro-optical properties of DLC-PAM. Observation the aligned property of DLC-PAM during temperature variation utilizing polarizing optical microscope, DLC-PAM exhibited the columnar alignment. We observed hexagonal columns which DLC-PAM aligned by X-ray diffraction, it benefited the carrier transporting. The absorption spectrum of DLC-PAM presented an absorption peak at 409 nm certifying that DLC-PAM could absorb the visible light. We measured the HOMO potential of DLC-PAM which is 5.47eV by PESA. Form absorption spectrum we calculated the band-gap of DLC-PAM which was 2.55~2.82eV, and then we used the HOMO potential and the band-gap to calculate the LUMO potential of DLC-PAM to be 2.65~2.92eV. The second part in this study we applied DLC-PAM to the organic solar cell. Because of the energy level of DLC-PAM and the different device structure tests we realized that DLC-PAM was suitable to be hole transporting layer. The device structure we used was ITO/PEDOT:PSS/DLC-PAM/P3HT:PCBM/Al, DLC-PAM layer was added between the PEDOT:PSS layer and the active layer. The power conversion efficiencies proved that DLC-PAM layer which benefited hole transporting raising the power conversion efficiency of the solar cell. The power efficiency of the device added DLC-PAM layer raised 16.2% comparing with the standard device.

Cr4+:YAG is an attractive gain medium due to its broad 3-dB emission spectrum ranging from 1253 to 1530 nm, which cover the low-loss window of the silica fiber. Such a broadband haracteristic offers a potential to develop a broadband amplified spontaneous emission (ASE) light source, optical amplifier, and tunable laser. Growing the Cr4+:YAG bulk crystal into fiber form is necessary for generating larger gain by the better optical confinement of the waveguide structure. For the application of laser, it is superior to bulk crystals for reducing lasing threshold and obtain the high slope efficiency due to the beter optical confinement and heat dissipation. A record-low threshold of 0.75 mW was achieved at room temperature. It is more than 500 times lower than any previously reported Cr4+:YAG lasers, and a slope efficiency of 6.9% was obtained. The ultralow-threshold lasing is made possible by the low propagation loss of 0.08 dB/cm and the high pump intensity of the core. Such a low-threshold operation makes the double-clad crystal fiber laser be compatible to present optical communication systems. Furthermore, we demonstrate that the proposed optimization algorithm can provide an efficient and direct approach to analyzing both fiber structure and bulk medium in terms of practical application requirements. The simulation results reveal that Cr4+:YAG DCF lasers offer advantages over bulk lasers in terms of low-threshold lasing and high efficiency, which are essential for their use in optical communication systems.

The research has been analyzed by using scanning electron and transmission electron microscopy (SEM and TEM).To research microstructure in single crystal alumina induced by Vickers indentation and the effect of alumina microstructure induced by deformation twinning. Sapphire is a kind of alumina single crystal called Corundum. It has fine machinery, optical, chemistry and anti-radiationary nature and been used widespread in industry world in recent years. Mechanical twinning is the main mode of plastic deformation. It has two types (1) basal twinning (2) rhombohedral twinning. When author pressed 20 N on (0001) plane, it produces B (0001), R1 ( 102) and R1 ¡¨ ( 104) in cross- section. But when pressing 20 N in (1 10) plane, it produces B (0001), B 1 ( 101) and R2 ( 012) in cross-section. In order to understand the role of pressure direction in twinning at room temperature, this research will discuss what effects will be produced twinning microstructure of alumina sample and derivation of dislocation microstructure by using scanning electron and transmission electron microscopy.

This study investigates the cholesteric grating based on a hybrid alignment. The experiment results reveal that the ordered stripe of the hybridly aligned cholesteric grating (H-fingerprint) only exists for the d/p ratio between 1.5 and 3, and the stripe orientation of the H-fingerprint is difficult to control due to the variation of the d/p ratio. Optical properties of the H-fingerprint are also investigated. The results show that the 1st order diffraction efficiency of the H-fingerprint is higher than the diffraction efficiency 2nd order, and its two switching times are about 1500ms and 500ms for the off-time and the on-time, respectively. The H-fingerprint with an anti-parallel rubbing process and the thermal effect are also investigated. The results reveal that the anti-parallel rubbing and the thermal effect can effectively control the stripe orientation of the H-fingerprint. The results greatly increase the possibility of applications for the H-fingerprint.

Thesis (Ph. D.)--Lehigh University, 2000. / Includes vita. Includes bibliographical references (leaves 189-194).

Thesis (Ph.D.)--Kent State University, 2008. / Title from PDF t.p. (viewed Jan 5, 2010). Advisor: Philip J. Bos. Keywords: liquid crystal, smectic, display, ferroelectric. Includes bibliographical references (p. 190-194).