Retrievals of atmospheric information from satellite observations permit the investigation of otherwise inaccessible atmospheric phenomena. The recovery of this information from optical instrumentation located in orbit requires both an inversion algorithm like the Saskatchewan Multiplicative Algebraic Reconstruction Technique and a forward model like the SASKTRAN radiative transfer model. These are used together at the University of Saskatchewan to retrieve sulphate aerosol extinction profiles from the radiance measurements made by the Canadian built OSIRIS instrument. Although these retrievals are highly successful the process currently does not consider the polarization of light or OSIRIS's polarization sensitivities because SASKTRAN is a scalar model. In this work the development of a vector version of SASKTRAN that can perform polarized radiative transfer calculations is presented.<p> The vector SASKTRAN's results compare favorably with vector SCIATRAN, another polarized model that is in development at the University of Bremen. Comparisons of the stratospheric aerosol retrieval vectors generated from the scalar and vector SASKTRAN results indicate that the polarized calculations are an important factor in future work to improve the aerosol retrievals and to recover particle size or composition information.

This essay examines how the conflict in Libya in 2011 was reported by the Swedish newspaper Dagens Nyheter and the American newspaper The New York Times. The purpose is to examine how the conflict is portrayed and what similarities and differences that exist between the two newspapers. We have used a quantitative content analysis and critical discourse analysis to get our results. In conclusion, both newspapers polarize the conflict to a large extent, resulting in a one-sided and biased account. However The New York Times is more objective and neutral in its portrayal of the conflict.

In this study, a liquid crystal Fresnel lens based on the cholesteric blue phase liquid crystals is proposed. Blue phases are liquid-crystalline phases that appear in a very small temperature range between a cholesteric phase and an isotropic phase. There are three types of blue phases; BP¢¹,BP¢º and BP¢». The BP¢¹ and BP¢º are characterized by a spatially periodic director field with lattice constants comparable to the wavelength of visible light. Because of the structural symmetry, blue phases are optically isotropic. In this study, the electro-optical properties of the BP¢º under different applied voltages are investigated. The results reveal that the Bragg reflection of the BPII has a red shift by increasing the applied voltage and a phase transition from BPII to cholesteric phase occurs at the high voltage regime (>100V). Based on the results, an electrically controlled blue phase Fresnel lens with polarization independence and high diffraction efficiency is demonstrated.

This research investigated the thermal properties of the polarization switching (PS) in vertical-cavity surface-emitting lasers (VCSELs). The investigations were performed by experiments and numerical simulations. In the experiments, the current modulation frequency and ambient temperature of VCSELs were varied to study their thermal effects on PS, resulting in rich dynamics. The current-heating effect on PS was also investigated by a step function current experiment. Based on an assumption that PS is activated as the temperature in the active region reaches a certain temperature, we model a simplified temperature rate equation to simulate the experiment of the step function. The consistency of the experiments and simulations concludes that the thermal effect plays a major role in PS and PS¡¦s hysteresis. These results contribute to the understanding of the mechanism of VCSEL¡¦s polarization switching.

The samples this thesis investigated were m-plane nitrides films grown on m-plane sapphire by plasma-assisted molecular beam epitaxy (PAMBE). Scanning electron microscopy (SEM) images revealed the surface morphologies of the films and thicknesses of the films were measured by cross-sectional scanning electron microscopy. Then we used electron back-scattered diffraction (EBSD) and X-ray diffraction (XRD) to check the growth orientation of the films. The m-plane nitrides films have the anisotropic optical properties were due to the growth orientation of the films. The films are under anisotropic stress since they were grown along m-axis and hence change the electron band structure (EBS), which resulted in anisotropic optical property. We studied the polarization properties of the luminescence at 15 K and 300 K by polarization dependent photoluminescence (PL) and calculated the degree of polarization. And then measured the strain of the m-plane nitrides films by micro-Raman spectroscopy, discussed the degree of polarization and stress. The degree of polarization larger as the anisotropic stress of the film increased.

Epitaxial m-plane (11 ¡Â00) ZnO thin films grown on m-sapphire substrates by atomic layer deposition have been studied. Atomic imaging and electron diffraction conducted in a transmission electron microscope (TEM) and crystallography by X-ray diffractometry all show consistent epitaxial relations with ZnO m-plane // sapphire m-plane, while ZnO [112 ¡Â0] // Al2O3 [0001], and ZnO [0001] // Al2O3 [112 ¡Â0]. The widths (full width at half maximum, or FWHM) of the rocking curves depend on the crystallographic axis of rotation. Dislocations near the interface between the ZnO epi-layers and sapphire substrates can be found from the cross-sectional TEM images when the direction of the incident electron beam, namely, the zone axis, is parallel to ZnO [112 ¡Â0], the a-axis of ZnO. There are stacking faults found in ZnO films away from their interfaces with the substrates. Polarization-dependent photoluminescence by differently polarized incident laser beam have also been investigated. Careful analysis of the spectra via multi-peak fittings revealed optical transitions at 3.32eV for T = 15K, which, however, shifted to 3.28eV at T = 300K. This shift in energy is accounted for by the quadratic temperature dependence of the Fermi level as determined by the positions of the lines of emission corresponding to the band edge transition. The 300K spectrum showed a more distinct peak at 2.48eV when the polarization of the emitted light was along the a-axis of ZnO, as compared to that along the c-axis of ZnO. The origin of this difference remains unaccounted for at the time of writing this thesis. The rest of the peaks have been interpreted in terms of optical transitions involving band gap impurity states, possible exciton formations, and their interactions with phonons.

In this thesis, we investigate the transformation bandwidth and the thickness sensitivity of the anisotropic-slab linearly polarizes (LP) to circularly polarized (CP) polarizer. We define a transformation bandwidth and the thickness sensitivity based on the axial ratio. New methods are proposed that can eliminate the lengthy derivation and give deeper physical insight to the problem. Under the small reflection approximation, i.e., only the forward waves are considered, our methods can be applied to the design of the anisotropic-slab LP to CP polarizer. For the single anisotropic slab, the effect is represented graphically on the polarization ratio plane. It is shown that the polarization locus for a given axial ratio leads to a circle in the polarization state diagram. When combined with the graphical description of the change in the polarization state, the transformation bandwidth and the thickness sensitivity from an initial LP wave to a desired CP wave can be obtained easily. Furthermore, we present a method using the equivalent circuits to represent the polarization effect in anisotropic media, so that some concepts of the electric circuit can be applied. This method is more convenient in dealing with the polarization change when multiple anisotropic-slabs exist. The transformation bandwidths and the thickness sensitivities for the anisotropic-slab polarizer for several lossless media are studied. The results are discussed and illustrated.

In this thesis, two series of self-assembled GaN and AlxGa1-xN nanorods are grown by plasma-assisted molecular beam epitaxy (PAMBE) on Si(111) wafer. The Al contents in AlxGa1-xN nanorods is varied from 6% to 75% by changing the Al cell beam flux (BFM). Second, the GaN/AlGaN multiple quantum wells (MQWs) with variation thickness are grown on the GaN nanorods with a p-GaN layer on the top. Al concentration is determined by electron probe x-ray micro-analysis (EPMA) and x-ray diffraction (XRD). The reflection high-energy electron diffraction (RHEED) and scanning electron microscopy (SEM) images show that the height, density and morphology of nanorods depend on the Al content. The (micro-)PL, CL and Raman spectra also show the variation of the characterization from those of GaN to AlN. The transmission electron microscopy (TEM) images show that the GaN/AlGaN MQWs structures with well widths of 1, 2, 3, 4, 6, 8 and 16 c-LC (Lattice constant on c-direction) were successful grown on the nanorods. The (micro-)PL and CL spectra show red-shift of the peak position with the decrease of Mg-doped concentration. When the well thickness is less then 4 c-LC, the CL spectra show blue-shift of the peak position with the decrease of the well thickness due to the Quantum-confined effect and the polarization effect in MQWS.

Based on a full-wave formulation, a vector boundary element method (VBEM) is proposed to model the photonic crystal fibers (PCFs) (microstructured fibers). The accuracy and efficiency of the approach are confirmed by comparing the results calculated with those in previous literatures. With employing the VBEM, the guiding characteristics, including the effective indexes, vector mode patterns, and the polarization properties of the PCFs are investigated. There polarization characteristics of the PCFs with elliptical air holes (EPCFs) and the one ring air-hole EPCF embedded in the step-index core are studied and discussed. In addition, based on the VBEM formulations, a novel and efficient numerical approach to calculate the dispersion parameters of the PCFs is also proposed. The effect of the PCF geometrical structure on the group velocity dispersion property is reviewed, and then the one-ring defect and two-ring defect PCFs are studied and designed for the ultra-flattened dispersion applications. As an example, a four-ring (two-ring defect) PCF with flattened dispersion of ¡Ó0.25 ps/km/nm from 1.295£gm to 1.725£gm wavelength is numerically demonstrated.

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