| Nano materials are useful materials with interesting optical and electronic properties. When combined with liquid crystals, they can improve the optical performance of liquid crystals. On the other hand, liquid crystals are very versatile materials which can be easily incorporated with nanoscale materials, or encapsulated inside nanoscale structures. Combining nano materials with liquid crystals, and studying the optical properties of these composites for the purpose of discovering new materials for low optical power, high resolution, and fast response, is the driving force behind our research. The motivation of this work is presented in Chapter 1 and a brief introduction of liquid crystals and nano materials is presented in Chapter 2.; In Chapter 3, we blended photosensitive cadmium selenide (CdSe) nanorods (7nm in diameter, 40nm in length) inside a nematic liquid crystal system. The effective intensity dependent refractive index coefficients are on the order of 10-2 (cm2/ Watt). This is at least 10 times larger than that of undoped liquid crystals. Most importantly, it is a transient process. We also observed one of the lowest electro-optical (E-O) switching threshold voltages from this doped system Vth = 0.78 ( Volts). It is postulated that the photosensitive CdSe nanorods improved the charge generation and charge transportation, as well as permittivity and conductivity anisotropy, of the liquid crystal system.; In Chapter 4, a unique 4-beam holographic method in an umbrella configuration is used to successfully fabricate three dimensional photonic structures within polymer dispersed liquid crystals. The resultant 3D structures exhibit multicolor reflection, and are optically characterized by taking transmission spectrum, as well as Bragg diffraction. An electro-optical switching time of tens of milliseconds is obtained from the structures. This tuning ability is achieved by the encapsulated liquid crystal droplets at the nodes of the structures. The fabrication is a fast, clean process over a large sample area. It is very useful for tunable photonics applications.; In addition to providing further detail on these works, I will briefly mention a few future research plans in Chapter 5. |
