Physical Sciences and Mathematics Commons^™

Irradiation Induced Order-Dis Order Transformations In Ni-Mo Alloys, Ovidiu F. Toader

Dissertations

No abstract provided.

Measurement Of The Nonlinear Refractive Index (N2) And Stimulated Raman Scattering In Optical Fibers As A Function Of Germania Content, Using The Photorefractive Beam Coupling Technique, Ferdinand Anayo Oguama

Dissertations

One of the greatest challenges in optical communication is the understanding and control of optical fiber nonlinearities. While these nonlinearites limit the power handling capacity of optical fibers and can cause noise, signal distortion and cross talk in optically amplified transmission systems, they have been equally harnessed for the development of new generations of optical amplifiers and tunable laser sources. The two prominent parameters that characterize the nonlinear properties of an optical fiber are the nonlinear refractive index n₂ and the Raman gain coefficient g_R. These parameters are related to the third order nonlinear susceptibility [x^{(3) …}

Understanding The Origins Of Metastability In Thin Film Growth; Tantalum And The Early Group Vb-Vib Metals, Neme Okechukwu Nnolim

Dissertations

Tantalum (Ta) is a metal that is highly prized for its applications in a variety of industries, including the microelectronics industry, where it is largely used in thin film modifications in order to achieve various electronic, magnetic and structural capabilities in solid-state devices. Ta frequently forms metastable phases, including the well-known ß-phase, during the preparation of thin Ta films by standard film deposition methods such as sputtering and electro-deposition. In order to gain insight into Ta metastable phase formation, the Bain transformation mechanism is studied for Ta and the neighboring body centered cubic (bcc) transition metals in Groups 5 and …

High Pressure Effects On Electron Transport And Structure Of Colossal Magnetoresistive Materials, Congwu Cui

Dissertations

Pressure effects on the electronic, magnetic properties and structure of several typical colossal magnetoresistive manganites, La_0.60Y_0.07Ca_0.33MnO₃, Pr_1-xCa_xMn0₃ (X = 0.25, 0.30, 0.35), Nd_1-xSr_xMnO₃ (x = 0.45, 0.50), were explored through high pressure resistivity and structure measurements. It was shown that pressure up to ~7 GPa induces more complicated charge, spin and lattice state changes than in the low pressure range explored previously. In La_0.60Y_0.07Ca_0.33MnO₃, pressure induces a local atomic structure transformation at a critical …

Nonlinear Optical Properties Of Novel Nanostructured Ion Implanted Laser Ablated Silicon Using Femtosecond Pulse Excitation, Elaine Nicole Lalanne

Dissertations

The study of the nonlinear optical properties of novel nanostructured ion implanted and laser ablation of Silicon is motivated by the need for materials that exhibit large values of the real part of the third order nonlinear susceptibility (χ⁽³⁾_Re). This property is essential for light controlled phase or refractive index modulation at low power, where the optical properties are used for optical switching devices. Previous nanosecond (ns) measurements indicated values of-2.8 x 10 ^-5; esu ( γ = 532 nm) for χ⁽³⁾_Re.

The characterization of nonlinear optical properties of the samples was studied …

Application Of Adaptive Optics To The Spectroscopic Investigation Of Small-Scale Solar Structures, Klaus Hartkorn

Dissertations

We study bright points, umbral dots and the G-band using a two-dimensional spectrometer and an Adaptive Optics system, which allows us to record high-resolution dopplergrams and residual intensity images. We find evidence that bright points are smaller than 120 km in diameter. Bright points are situated exclusively in regions of enhanced G-band brightness and do not show a change in their shape or a displacement in their position of more than 120 km horizontally over a height range from 0 km to 320 km above photospheric level T = 1. We do not find velocity differences of more than 100 …