Mechanical rubbing alignment is the most common used method in the liquid crystal display manufacturing process. However, it may cause dust and electrostatic problem. In this study, we investigate effects of low surface free energy Polydimethylsiloxane (PDMS) on orientation of liquid crystal molecules in a confined structure and fabricate alignment layer using PDMS. In the present study, we show that liquid crystal molecules are arranged in consistency without rubbing process and it may be a new homogeneously aligned mode in liquid crystal display. In this thesis, liquid crystal textures were observed using polarizing optical microscopy (POM). It was found that liquid crystal molecules were homogeneously aligned in PDMS holes. In addition, this thesis indicated that how liquid crystal alignment affected by PDMS layer thickness and surface treatment. We learned that using treatment of JALS-9800 film on the bottom substrate from liquid crystal texture can obtain the arrangement of expected liquid crystal molecules. The liquid crystal device can be produced using PDMS structure. The measurement of electro-optic characteristics showed that the circular shape in the confined structure had better transmittance and contrast ratio.

Many properties of photosensitize material is applied to the holographic recording of the photosensitive materials. The diacrylateis(RM257) is liquid crystalline materials. Beasuse the RM257 with photopolymeriable acrylate endgroups, under the action of light, polymerization of the mesogen with two polymerization groups lesds to crosslinked polymer networks. As the RM257 has a sensitivity to light and good molecular arrangement , it can be applied to optical storage. In this study, the use of the RM257 thin films as holographic recording materials ; the holography patterns were written using two s-s polarized, mutually coherence He-Ne laser at 633nm light. First, a single beam of He-Ne laser irradiates the RM257, and control exposure time, irradiation intensity, to investigate the RM257 on He-Ne laser (633nm) absorption. Then RM257 thin film exposed to two beams of He-Ne laser induced holographic interferemce fileld. Holography irradiation RM257 thin film arranged molecular singular direction and periodic alignment of molecular, and to fabricate the formation of holographic gratings. The sample temperature is controlled during holography irradiation, can improve RM257 thin film record as holographic interferemce fileld. To investigate holographic fileld induced the molecular of RM257 thin film.

He-Ne Laser induced polymerization in diacrylate mesogens RM257 had been verified in previous studies. Holography patterns can also be recorded in RM257 using He-Ne Laser. Higher diffraction efficiency was obtained by controlling temperature of the mesogen. In the present study, we consider the diacrylate compound RM82 that is main chain polymeric liquid crystal with different length of chain. We focus on two objectives in this study: (i) to investigate polymerization and absorbance of RM82 thin film that was exposed to He-Ne laser with the temperature of sample control, the initial power intensity of laser beam and the exposed time. (ii)Using the result of part (i), the possibility of the use of RM82 thin film for recording holographic patterns produced using a laser beam emitted from a 12mW He-Ne laser operated at 633 nm wavelength is studied. The periodic structures and orientated diacrylate polymer networks are produced in the polymer film by holographic field produced using He-Ne laser. The region of light stripes was aligned perpendicular to the gratings, whereas the region of dark stripes was disorder.

This study researches the nonlinear optical properties of the blue phase liquid crystals using the Z-scan technique. The purpose is to investigate the non-linear effect of the blue phase liquid crystals induced by the thermal and the liquid crystal reorientation effect. The Z-scan technique is common method to measure the non-linear index n2 and the non-linear absorption coefficient of materials. The measurement of the optical Kerr constant using Z-scan is based on the principle of spatial beam distortion due to the self-focusing or self-defocusing. For typical nematic liquid crystals, the nonlinear effect in the nematic phase is large than that in the isotropic phase. However, due to the anisotropic properties of the liquid crystal, the light-induced nonlinear effect in the nematic phase is polarization dependency. Unlike nematic phase, the blue phase is optical isotropic duo to its symmetric structure, and therefore blue phase are polarization independent and provide a larger non-linear effect. The experiments to measure the nonlinear refractive index n2 are as follows: firstly, a linearly polarized Ar+ laser light (£f=532nm) is focused in the z direction onto the sample via lens, and the detector was set behind the sample. Sequentially, the light intensity is recorded while the sample is scanned near the beam waist of the green laser. Finally, the non-linear index n2 of the material is derived from mathematical calculation. The study investigated two kinds of material, pure blue phase liquid crystal and dye-doped blue phase liquid crystal, and measured their non-linear index n2 in the blue phase and isotropic phase, respectively. The experimental results show that the non-linear index n2 of dye-doped blue phase liquid crystal is 100~1000 times as large as this of the pure blue phase liquid crystal at the blue phase. Besides, compared with isotropic phase in the blue phase liquid crystal, the blue phase actually possesses larger non-linear index n2. This experiment confirms that the nonlinear effect can be induced using linearly polarized Ar+ laser, and the nonlinear refractive index n2 can be measured using Z-scan technique.

In this study, we researched three kinds of surface treatment (no surface treatment, homogeneous alignment (HA) and vertical alignment (VA)) effect for the optoelectronic properties of cholesteric blue phase liquid crystals (BPLCs). We demonstrate the surface treatments have influence on the temperature range of BPLCs. The VA-BPLC possesses the widest temperature range, about 6.0 ¢J. The temperature range of both no surface treatment BPLC and HA-BPLC are about 5.5 ¢J. In the process of cooling, the surface treatments will restrain the change of the pitch of BPLC. Besides, surface treatment will let the crystalline of BPLC shipshape, so that it can reduce the scattering of the reflection light of BPLC. In the vertical electric field, the reflection wavelength of BPLC will be red-shift when the applied voltage increased. The reflection wavelength of the HA-BPLC can be tuned about 90 nm. The reflection wavelength of the VA-BPLC can be tuned about 120 nm. We have demonstrated the treatment of vertical alignment will reduce the operating voltage of BPLC.

In this thesis, with external cavity semiconductor laser, a high lateral resolution thickness measurement is proposed and demonstrated. The approach is typical an intra-cavity measurement of focused cell thickness by wavelength tuning of an external cavity laser diode. In addition, using blue light of 406nm as laser diode, higher lateral resolution is also observed. Using the proposed thickness method, the lateral resolution and longitudinal resolution have been demonstrated with 20£gm and 0.15£gm, respectively. We also discuss the feasibility of £gm scaled lateral resolution through improvement of laser diode, such as M^2~1.

In this thesis we synthesize discotic liquid crystal materials. After demonstrating the molecular structures by 1H-NMR of Acid-6, we measure the properties of this material. We use discotic liquid crystal Acid-6 and measure its¡¦ properties. It shows the properties of Acid-6 which is having the ability of absorbing visible light. By UV-Vis spectrum, we can realize the absorption band is located at 400 nm and confirm that it is able to be a photo-sensitized dye. Besides, the property of discotic liquid crystal is the self-assembly ability, the molecular can assemble into hexagonal columnar structure by themselves, which enable discotic liquid crystal to have better mobility. The DSSCs have good power conversion efficiency with using discotic liquid crystals Acid-6. We can measure its¡¦ mobility to know the component with which the most appropriate.

In this study, we fabricated an electrically wavelength-tunable resonant-cavity light emitting diode (RCLED). It was achieved by the combination of an AlGaInAs quantum well structure with an intra-cavity liquid crystal material. In the phase modulator layer, we used nematic liquid crystal (NLC) and cholesteric liquid crystal (CLC), respectively, comparing their difference in the infrared-spectrum. When inserting NLC, the anisotropic properties of liquid crystal enable continuous tuning of mode emission along the extraordinary direction and provide a 58 nm tuning range. The optical characteristics of this device are polarization dependent. On the contrary, the CLC-based device is polarization independent because any polarization of incident light experiences the same averaged refractive index. However, the phase difference of CLC is less than NLC, only a 41 nm tuning range of this sample. We also simulated and discussed experimental results of NLC-based RCLED. The optical pumping of the active region is realized by a CW laser at 1064 nm wavelength and observed at room temperature.

Discotic liquid crystals (DLCs), which consist of disk-like molecules, have recently attracted considerable attention for their interesting electronic properties. One of the most significant of DLCs is their high charge carrier mobility in their columnar structure. Recently the number of researches have been increasing on applications such as organic light-emitting diodes (OLED), photovoltaic devices (OPV) and organic field-effect transistors (OFET). The purpose of the study is to investigate the mobility of different alignment of DLCs. The material used in the present study is HDBP-8. We will show that the stack of DLCs depended on temperature strongly. We will also discuss charge transport properties of homeotropic alignment. Carrier transport has been investigated in the hexagonal columnar (Colh) mesophase of HDBP-8 using time-of-flight (TOF) technique. The carrier mobilities are up to the order of 10-3 cm2V-1s-1 for both positive and negative charges with weak dependence on the electric fields.

In this study, we study three kinds of surface treatments in the blue phase lasers. Three kinds of surface treatments include no surface treatment, homogeneous alignment ,HA, and vertical alignment ,VA. Blue Phase liquid crystal is a three-dimensional photonic crystal, and it can be used to be a laser cavity. When the blue phase doped with a laser dye, a laser emission can be observed under appropriate pumping energy. In the first part, we fabricate the blue phase lasers with three kinds of surface, there are different surface treatments to study the surface effect of the optoelectronic properties. It is found that the threshold pumping power is significantly decreased under a surface treatment on glass substrate. In the second part, we change cooling rate in the formation of the blue phase liquid crystals, and study the optoelectronic properties of blue phase lasers. The experiment results reveal that the slower cooling rate leads to a order blue phase substrate, resulting in a lower threshold pumping energy of the blue phase laser.