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  Partner: UNT Libraries
 Department: Department of Physics
 Decade: 2010-2019
 Year: 2011
High Efficiency High Power Blue Laser by Resonant Doubling in PPKTP

High Efficiency High Power Blue Laser by Resonant Doubling in PPKTP

Date: August 2011
Creator: Danekar, Koustubh
Description: I developed a high power blue laser for use in scientific and technical applications (eg. precision spectroscopy, semiconductor inspection, flow cytometry, etc). It is linearly polarized, single longitudinal and single transverse mode, and a convenient fiber coupled continuous wave (cw) laser source. My technique employs external cavity frequency doubling and provides better power and beam quality than commercially available blue diode lasers. I use a fiber Bragg grating (FBG) stabilized infrared (IR) semiconductor laser source with a polarization maintaining (PM) fiber coupled output. Using a custom made optical and mechanical design this output is coupled with a mode matching efficiency of 96% into the doubling cavity. With this carefully designed and optimized cavity, measurements were carried out at various fundamental input powers. A net efficie ncy of 81 % with an output power of 680 mW at 486 nm was obtained using 840 mW of IR input. Also I report an 87.5 % net efficiency in coupling of blue light from servo locked cavity into a single mode PM fiber. Thus I have demonstrated a total fiber to fiber efficiency of 71% can be achieved in our approach using periodically poled potassium titanyl phosphate (PPKTP). To obtain these results, all ...
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Ion Beam Synthesis of Carbon Assisted Nanosystems in Silicon Based Substrates

Ion Beam Synthesis of Carbon Assisted Nanosystems in Silicon Based Substrates

Date: May 2011
Creator: Poudel, Prakash Raj
Description: The systematic study of the formation of β-SiC formed by low energy carbon ion (C-)implantation into Si followed by high temperature annealing is presented. The research is performed to explore the optimal annealing conditions. The formation of crystalline β-SiC is clearly observed in the sample annealed at 1100 °C for a period of 1 hr. Quantitative analysis is performed in the formation of β-SiC by the process of implantation of different carbon ion fluences of 1×1017, 2×1017, 5×1017, and 8×1017 atoms /cm2 at an ion energy of 65 keV into Si. It is observed that the average size of β-SiC crystals decreased and the amount of β-SiC crystals increased with the increase in the implanted fluences when the samples were annealed at 1100°C for 1 hr. However, it is observed that the amount of β-SiC linearly increased with the implanted fluences up to 5×1017 atoms /cm2. Above this fluence the amount of β-SiC appears to saturate. The stability of graphitic C-C bonds at 1100°C limits the growth of SiC precipitates in the sample implanted at a fluence of 8×1017 atoms /cm2 which results in the saturation behavior of SiC formation in the present study. Secondly, the carbon cluster formation process ...
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Nanoscale Materials Applications: Thermoelectrical, Biological, and Optical Applications with Nanomanipulation Technology

Nanoscale Materials Applications: Thermoelectrical, Biological, and Optical Applications with Nanomanipulation Technology

Date: August 2011
Creator: Lee, Kyung-Min
Description: In a sub-wavelength scale, even approaching to the atomic scale, nanoscale physics shows various novel phenomena. Since it has been named, nanoscience and nanotechnology has been employed to explore and exploit this small scale world. For example, with various functionalized features, nanowire (NW) has been making its leading position in the researches of physics, chemistry, biology, and engineering as a miniaturized building block. Its individual characteristic shows superior and unique features compared with its bulk counterpart. As one part of these research efforts and progresses, and with a part of the fulfillment of degree study, novel methodologies and device structures in nanoscale were devised and developed to show the abilities of high performing thermoelectrical, biological, and optical applications. A single β-SiC NW was characterized for its thermoelectric properties (thermal conductivity, Seebeck coefficient, and figure of merit) to compare with its bulk counterpart. The combined structure of Ag NW and ND was made to exhibit its ability of clear imaging of a fluorescent cell. And a plasmonic nanosture of silver (Ag) nanodot array and a β-SiC NW was fabricated to show a high efficient light harvesting device that allows us to make a better efficient solar cell. Novel nanomanipulation techniques were ...
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Temporal Properties Of Dynamic Processes On Complex Networks

Temporal Properties Of Dynamic Processes On Complex Networks

Date: December 2011
Creator: Turalska, Malgorzata A.
Description: Many social, biological and technological systems can be viewed as complex networks with a large number of interacting components. However despite recent advancements in network theory, a satisfactory description of dynamic processes arising in such cooperative systems is a subject of ongoing research. In this dissertation the emergence of dynamical complexity in networks of interacting stochastic oscillators is investigated. In particular I demonstrate that networks of two and three state stochastic oscillators present a second-order phase transition with respect to the strength of coupling between individual units. I show that at the critical point fluctuations of the global order parameter are characterized by an inverse-power law distribution and I assess their renewal properties. Additionally, I study the effect that different types of perturbation have on dynamical properties of the model. I discuss the relevance of those observations for the transmission of information between complex systems.
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Thorium and Uranium M-shell X-ray Production Cross Sections for 0.4 – 4.0 MeV Protons, 0.4 - 6.0 MeV Helium Ions, 4.5 – 11.3 MeV Carbon Ions, and 4.5 – 13.5 MeV Oxygen Ions.

Thorium and Uranium M-shell X-ray Production Cross Sections for 0.4 – 4.0 MeV Protons, 0.4 - 6.0 MeV Helium Ions, 4.5 – 11.3 MeV Carbon Ions, and 4.5 – 13.5 MeV Oxygen Ions.

Date: May 2011
Creator: Phinney, Lucas C.
Description: The M-shell x-ray production cross section for thorium and uranium have been determined for protons of energy 0.4 - 4.0 MeV, helium ions of energy 0.4 - 6.0 MeV, carbon ions of energy 4.5 - 11.3 MeV and oxygen ions of energy 4.5 - 13.5 MeV. The total cross sections and the cross sections for individual x-ray peaks in the spectrum, consisting of the following transitions Mz (M4-N2, M5-N3, M4-N3), Ma (M5-N6,7), Mb (M4-N6, M5-O3, M4- O2), and Mg (M4-O3, M5-P3, M3-N4, M3-N5), were compared to the theoretical values determined from the PWBA + OBKN and ECUSAR. The theoretical values for the carbon and oxygen ions were also modified to take into account the effects of multiple ionizations of the target atom by the heavier ions. It is shown that the results of the ECUSAR theory tend to provide better agreement with the experimental data.
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