The objective of this thesis was to explore the chemistry of series of linear and star shaped compounds based on benzimidazolyl, 2-(2’-pyridyl)benzimidazolyl, and 2,2’-dipyridylamino functional groups. These groups all possess Lewis base sites suitable for metal coordination, and are all known fluorophores. The first compounds to be presented are the homo-substituted benzimidazolyl derivatives. Compounds 2.1-2.5 have been fully characterized and are all luminescent with emission energies in the UV region. While coordination complexes with these ligands have not been isolated, the effect of metal ion complexation on ligand luminescence has been explored via metal ion titration experiments. Furthermore, these compounds all have electron affinities greater than -3.0 eV and large optical bandgaps that range between 3.55 and 3.95 eV. These compounds also have high thermal and morphological stability. In light of this, compound 2.3 was selected as a representative example, and further characterized as an electron transport/hole blocking material for OLED applications. It has demonstrated a performance comparable to that of the well known electron transport material Alq3 (q = 8-hydroxyquinolinate). The second class of compounds, 3.2 and 3.3, represent a pair of hetero-substituted ligands with two different binding sites available for coordination chemistry. A copper (I) complex of 3.3 has been isolated and exhibits orange phosphorescence at room temperature and at 77 K. Furthermore, a series of metal titration experiments have been performed on 3.3 and 3.4, and have demonstrated the preference of different metal ions for either the 2,2’-dipyridylamino site, or the 2-(2’-pyridyl)benzimidazolyl binding site. The details of these explorations will be presented in the subsequent chapters. / Thesis (Master, Chemistry) -- Queen's University, 2007-07-31 12:17:06.011

A detailed theoretical study for the operation of the surface-acoustic-wave diode storage correlator is presented. A circuit model describing the device is developed which is used to analyze the signal storage characteristics and the different read-out modes of operation for both p-n and Schottky diode structures. The calculated predictions of the proposed theory are in excellent agreement with experimental data published by independent researchers. The theory presented is self consistent and takes into account, for the first time, the minority carrier lifetime in the dynamics of charging the p-n diode structures which was neglected in previous theories. A straightforward transmission line theory approach is developed for finding the surface-wave amplitude excited by the diode potential during the read-out process. The frequency response characteristics predicted for these structures is a fairly slowly varying function of frequency; hence such correlators are essentially bandlimited by the input and output surface-wave transducers.

No description available.

This thesis consists of three main parts. An introduction to diode-pumped solid-state lasers, thermal modelling of solid-state lasers and rate-equation modelling of solid-state lasers. The first part explains the basic components and operation principles of a typical diode-end-pumped solid-state laser. The stimulated emission process, solid-state laser gain media, various pump geometries and a basic end-pumped laser resonator configuration are among the topics that are explained. Since thermal effects are one of the main limiting factors in the power-scaling of diode-pumped solid-state lasers, the second part of this thesis describes numerical and analytical thermal models that determine the thermal lens and thermally induced stresses in a laser crystal. As a first step, a time-independent numerical thermal model which calculates the three-dimensional temperature distribution in the laser crystal is implemented. In order to calculate the time dependent thermally induced stresses in a laser crystal, a coupled thermal-stress finite element analysis model was implemented. Even though some steady-state analytical solutions for simple crystal geometries do exist, the finite element analysis approach was taken so that the time dependent thermally induced stresses could be calculated for birefringent crystals of various geometries. In order to validate the numerical results, they are compared to experimental data and analytical solutions where possible. In the last part, the population dynamics inside the laser gain medium are described and modelled with a quasi-three-level rate-equation model. A comprehensive spatially resolved rate-equation model is developed and discussed. In order to simplify the implementation of the rate-equation model as a computer simulation, the spatial dependence of the laser parameters is ignored so that the model reduces to a singleelement plane-wave model. The simplified rate-equation model is implemented and solved numerically. The model is applied to a four-level CW and Q-switched Nd:YLF laser as well as a quasi-three-level QCW Tm:GdV04 laser. The models' predictions are thoroughly verified with experimental results and also with analytical solutions where possible. / Thesis (M.Sc.)-University of KwaZulu-Natal, 2008.

No description available.

Organic light emitting diodes (OLEDs) are being commercialized in display applications, and will be potentially in lighting applications in the near future. This thesis is about the design of high performance OLEDs, which includes both the electrical and optical design of OLEDs. In particular, the following work is included in this thesis: i) Energy level alignment and charge injection at metal/organic interfaces have been systematically studied. ii) Transition metal oxide anodes have been developed to inject sufficient holes into the OLEDs due to their high work function. The oxide anodes have also been used to systematically study the transport properties in organic semiconductors. iii) Highly simplified OLED devices with unprecedentedly high efficiency have been realized using both fluorescent and phosphorescent emitters. The high performance was enabled by using a high work function metal oxide anode and a hole transport material with very a deep highest occupied molecular orbital (HOMO). iv) An optical model has been developed to describe the optical electric field across the OLED device. By using the model, a high performance flexible OLED using metal anode was designed and realized.

This project involves the study of optical properties of polymers doped with TRIMM (transparent refractive index matched micro-particles), and their uses in light guides. The refractive index difference between dopant and host material is small (0.02), so forward transmittance is high, and losses due to backscattering are negligible. Flexible polymer optical fibre (POF) and polymethylmethacrylate (PMMA) rods are being incorporated into an increasing range of lighting and light mixing applications. For energy efficient mixing of red, green and blue (RGB) light-emitting diodes (LEDs) to produce white light and a range of other colours, light is transmitted from the end of a light guide ('endlight'). A major problem here is solved, namely the achievement of uniform illumination, simultaneously with low losses from scattering. Light output from RGB LEDs is shown to be completely mixed by short TRIMM-doped light guides. Alternatively, long lengths of TRIMM-doped POF can be used for 'side-light'. The concentration of TRIMM for these is chosen such that light is emitted from the side walls of the guide to give even illumination along its length. A geometrical method of ray tracing in particle-doped rectangular and cylindrical light guides is derived, and Monte Carlo ray tracing simulations performed for undoped and TRIMM-doped light guides. The evolution of the distribution of ray angles, internal and external to a light guide, with propagation distance are studied. Computer simulations of angular distribution of light emitted from the wall of POF agree with measurements performed using a photogoniometer. Simulations and measurements of light output intensity and colour from RGB LED arrays when projected from the end of a mixing rod, are also presented. Colour calculations agree with photometric measurements of RGB LED output from clear and TRIMM-doped PMMA mixing rods. Results of transmittance measurements and computer simulations show that light losses are almost entirely due to Fresnel reflectance from the entrance and exit surfaces of the rods. Photogoniometer measurements of the angular distribution of light from LEDs are used as a basis for LED source models used in ray tracing simulations. Results of an investigation comparing the effect of using a smoothed LED source model instead of measurement-based models on simulated light output distributions are presented. The light output from LEDs can have sudden peaks in intensity at certain angles, resulting in distinctive patterns with clear colour separation, after mixing in clear polymer mixing rods. These caustic patterns are eliminated by using TRIMM-doped mixing rods, with a transmittance of 90% after Fresnel losses, which can be readily reduced.

Thesis (M.S.)--Oregon Graduate Center, 1988.

Zugl.: Zürich, Techn. Hochsch., Diss., 2007

Dissertation (Ph.D.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references.