Azo-Dye Doped Liquid Crystal (DDLC) is a developed material which can be used to fabricate optical shutter, displays, etc. In this thesis, we presents of the transient grating on a planar aligned DDLC. The effect of various polarizations of writing and probing beams, and of temperature on the transient grating are examined. Then, we propose a model to explain the result. Through this study, we understand the factors that determine the light-induced aligning Dye effect on nematic liquid crystals.

Abstract During the last decade, the maximum capacity of an optical fiber transmission line more than doubled every year to match the fast-growing communication need. The technology break through in dry fiber fabrication opens the possibility for fiber bandwidth all the way from 1.3

The fabrication and characterization of boron-doped diamond microelectrodes for use in electrochemical detection coupled with capillary electrophoresis (CE-EC) is discussed. They exhibited low and stable background currents and sigmoidally shaped voltammetric curves for cysteine, cystine and Fe(CN)63-/4- . Evaluation of the CE-EC system and the electrode performance were accomplished using a 10 mM borate buffer, pH 8.8, run buffer, and a 70-cm-long fused-silica capillary (10-mm i.d.) with seven sulfur-containing amino acids (methionine, cysteine, cystine, homocysyeine, homocystine, glutathionine, glutathionine disulfide) as test analytes. Reproducible separation (elution time) and detection (peak current) of seven sulfur-containing amino acids were observed with response precisions of 5% or less.

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During the last decade, the maximum capacity of an optical fiber transmission line more than doubled every year to match the fast-growing communication need. The technology break through in dry fiber fabrication opens the possibility for fiber bandwidth all the way from 1300 nm to 1600 nm. The fast increasing demand of communication capacity results in the emergence of wavelength division multiplexing (WDM) technology, enabling tens of channels with different wavelengths transmitted simultaneously on an optical fiber. In consequence, it raises the requirement of spectral bandwidth of all the optical components used in the optical transport networking systems. Cr4+:YAG has potential to meet this demand because its 3T2¡÷3A2 transition has a strong spontaneous emission that just covers the low-loss window of optical fiber. The crystalline host offers a excellent mechanical characteristic. Such a fiber is, therefore, eminently suitable for super-wideband optical source since the required pump power is expected to be higher. We have successfully demonstrated a diode-laser pumped Cr:YAG crystal fiber ASE light source. The crystal fibers are grown by the laser-heated pedestal growth technique. Using a 46.6 mm-long Cr:YAG single crystal fiber of a 3-dB ASE width of 265 nm and a power spectral density ¡V22.1 dBm/nm was achieved. In the future, to further increase the quantum efficiency and output power we will reduce the core diameter, lengthen the fiber, increase the Cr4+ doping concentration, fabricate double-cladding, coat the fiber facets, and improve the cooling system.

¡@¡@Currently, The Cr-doped fibers are grown by LHPG method or drawing-tower technique. The Cr-doped YAG preform was firstly fabricated by a rod-in-tube method. We have successfully fabricated the Cr-doped fibers by using a commercial drawing-tower technique. By employing a negative pressure control in drawing-tower technique on the YAG preform, the Cr-doped fibers with a better core circularity and uniformity, and good interface between core and cladding were fabricated. The core non-circularity was smaller than 3%, the spontaneous emission spectrum showed the bandwidth that approach to 300 nm, and the output power density level have promoted to a few nW/nm. ¡@In this study, we focused on the analysis of dynamic fluorescent characteristics of Cr-doped fibers in order to improve the quality effectively. The lifetimes of Cr4+ fluorescence and concentration of Cr ions were 1.5 £gs and 510 £gg/g, respectively.The concentration of the Cr ions was less than the Cr-doped fibers grown by LHPG method. The high-resolution micrograph showed that there was nano-crystalline structure in the core surrounded by SiO2 amorphous matrix. These nano-particles gathered at the core and formed micrometer clusters, and therefore resulted in high scattering loss around 1.17dB/cm. ¡@¡@In order to improve the Cr-doped fibers quality, reduce propagation loss, and promote the spontaneous emission power density. We have to decrease the temperature and drawing speed in the drawing process Therefore, the new Cr-doped fibers may have the potential for being used as a new generation broadband fiber amplifier to cover the bandwidth of the entire 1.3-1.6 £gm range which exhibit 300 nm usable spectral bands.

Aluminum doped zinc oxide AZO has been studied for 20 years. It can improve thin films¡¦ thermal stability and transparency in visible range .However AZO is not as good as ITO in conductivity and transparency, that¡¦s why the application of AZO is only limited in few fields. This is because the nature limit of ZnO. Because part of doped Al forms Al2O3 instead of sits on Zn sites, that enhances light and carriers scattering and suppresses the optical transparency and electric conductivity. This study is plane to take advantage of amorphous properties, that may be achieved try grown films at liquid Nitrogen temperature, in which the distribution of Al and Zn will be very uniform and the solubility of Al will be high. ZnO:Al thin films is grown on glass substrates at low temperature by Radio frequency magnetron sputtering system. Low-temperature deposition is done in order to deposit amorphous thin films (ceramic targets ZnO contained 2wt.% Al2O3). The Al3+ in place of Zn2+ should be uniformly distributed in the thin films because of amorphous structure. It expects to find the best deposition condition under a fixed target-to-substrate distance (10cm) by varying growth, such as the deposition mode, PF plasma power and working pressure. AFM, XRD (grazing incident x-ray diffraction) and N&K analyzer were used to measure the thin surface morphology, structure, thickness and transmittance, respectively. The colors of the thin films are very different dependent on the modes of deposition. The low sputtering rate by lower RF power and high working pressure is the key to successfully grow amorphous ZnO:Al films. The amorphous ZnO:Al thin films (a-5) are deposited under 100W of RF power and 50mTorr of working pressure. The transmittance of the assembly of ZnO:Al thin films/glass substrate is the same as glass substrates which inducates the transmittance of films is far above 90%. However, the amorphous ZnO:Al thin films are poor conductor . We also tried to improve it by the post-annealing of ZnO:Al thin films in 2% hydrogen atmosphere. It is found to be not successful.

Thesis (M.S.)--Naval Postgraduate School, 2002. / Thesis advisor(s): Todd Weatherford, Ronald Pieper. Includes bibliographical references (p. 39-40). Also available online.

This dissertation explores the electrochemical behavior of enzymes and their cofactors at carbon nanotube (CNT) and nitrogen-doped carbon nanotube (N-CNT) electrodes. Two common types of oxidoreductases are considered: flavin adenine dinucleotide (FAD)-dependent oxidases and nicotinamide adenine dinucleotide-dependent (NAD⁺)-dehydrogenases. Chapter 1 presents the oxygen reduction reaction (ORR) at N-CNT electrodes as a way to electrochemically measure enzymatic turnover at the electrode surface. The unique peroxide pathway at N-CNT electrodes, which catalytically disproportionates hydrogen peroxide (H₂O₂) back into oxygen, provides an increased ORR current directly proportional to the rate of enzymatic turnover for H₂O₂ producing enzymes, even in an oxygen saturated solution. Biosensing of L-lactate using the increased ORR current is demonstrated using L-lactate oxidase. Chapter 2 explores the surface bound electrochemical signal of FAD when FAD-dependent enzyme or free FAD is allowed to spontaneously adsorb onto the CNT/N-CNT surface. Specifically, the origin of the enzymatically generated FAD signal and the rate constant of the electron transfer are elucidated. Chapter 3 continues the discussion of the cofactor FAD by demonstrating its use as an informative surface specific redox probe for graphitic carbon surfaces. Primarily, FAD can be used to determine the electroactive surface area and the relative hydrophobicity/hydrophilicity of graphitic surfaces. Chapter 4 changes gears to NAD⁺-dependent dehydrogenases by investigating the electrocatalytic oxidation of NADH at N-CNTs in comparison with conventional carbon electrodes or nondoped CNTs. Biosensing of glucose through the oxidation of NADH is demonstrated using glucose dehydrogenase adsorbed onto the N-CNT surface. Chapter 5 continues the discussion of NAD⁺-dependent dehydrogenases by addressing the reaction kinetics of NADH oxidation at N-CNTs as a tool to measure the enzymatic reduction of NAD⁺.

The current treatment of water contaminated with organic compounds includes adsorption, air stripping, and advanced oxidation processes. These methods large quantities of water and require excessive energy and time. A novel treatment process of concentrating and then electrochemically oxidizing compound would be a more feasible practice. This research investigated the oxidative destruction of perfluorooctane sulfonate (PFOS), perfluorobutane sulfonate (PFBS) and trichloroethene (TCE) at boron-doped diamond film electrodes and the adsorption of PFOS and PFBS on granular activated carbon and ion exchange resins.Experiments measuring oxidation rates of PFOS and PFBS were performed over a range in current densities and temperatures using a rotating disk electrode (RDE) reactor and a parallel plate flow-through reactor. Oxidation of PFOS was rapid and yielded sulfate, fluoride, carbon dioxide and trace levels of trifluoroacetic acid. Oxidation of PFBS was slower than that of PFOS. A comparison of the experimentally measured apparent activation energy with those calculated using Density Functional Theory (DFT) studies indicated that the most likely rate-limiting step for PFOS and PFBS oxidation was direct electron transfer. The costs for treating PFOS and PFBS solutions were compared and showed that PFOS is cheaper to degrade than PFBS.Screening studies were performed to find a viable adsorbent or ion exchange resin for concentrating PFOS or PFBS. Granular activated carbon F400 (GAC-F400) and an ion exchange resin, Amberlite IRA-458, were the best methods for adsorbing PFOS. Ionic strength experiments showed that the solubility of the compounds affected the adsorption onto solid phases. Regeneration experiments were carried out to determine the best method of recovering these compounds from the adsorbents; however, the compounds could not be effectively removed from the adsorbents using standard techniques.The electrochemical oxidation of trichloroethene (TCE) at boron-doped diamond film electrodes was studied to determine if this would be a viable degradation method for chlorinated solvents. Flow-through experiments were performed and showed TCE oxidation to be very rapid. Comparing the data from the DFT studies and the experimentally calculated apparent activation energies the mechanism for TCE oxidation was determined to be controlled by both direct electron transfer and oxidation via hydroxyl radicals.