ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
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With the 1D geometry, nanowires are natural optical waveguides for light guiding and propagation. By introducing feedback mechanisms to nanowire waveguides, such as the cleaved end facets, the nanowires can work as ultra-small size lasers. Since the first demonstration of the room-temperature ultraviolet nanowire lasers in 2001, the nanowire lasers covering from ultraviolet to mid infrared wavelength ranges have been intensively studied. This dissertation focuses on the optical characterization and laser fabrication of two nanowire materials: erbium chloride silicate nanowires and composition-graded CdSSe semiconductor alloy nanowires.
Chapter 1 – 5 of this dissertation presents a comprehensive characterization of a newly developed erbium compound material, erbium chloride silicate (ECS) in a nanowire form. Extensive experiments demonstrated the high crystal quality and excellent optical properties of ECS nanowires. Optical gain higher than 30 dB/cm at 1.53 μm wavelength is demonstrated on single ECS nanowires, which is higher than the gain of any reported erbium materials. An ultra-high Q photonic crystal micro-cavity is designed on a single ECS nanowire towards the ultra-compact lasers at communication wavelengths. Such ECS nanowire lasers show the potential applications of on-chip photonics integration.
Chapter 6 – 7 presents the design and demonstration of dynamical color-controllable lasers on a single CdSSe alloy nanowire. Through the defect-free VLS growth, engineering of the alloy composition in a single nanowire is achieved. The alloy composition of CdSxSe1-x uniformly varies along the nanowire axis from x=1 to x=0, giving the opportunity of multi-color lasing in a monolithic structure. By looping the wide-bandgap end of the alloy nanowire through nanoscale manipulation, the simultaneous two-color lasing at green and red colors are demonstrated. The 107 nm wavelength separation of the two lasing colors is much larger than the gain bandwidth of typical semiconductors. Since the two-color lasing shares the output port, the color of the total lasing output can be controlled dynamically between the two fundamental colors by changing the relative output power of two lasing colors. Such multi-color lasing and continuous color tuning in a wide spectral range would eventually enable color-by-design lasers to be used for lighting, display and many other applications.
In the first chapter, Indium Phosphide nanowires were grown using elemental sources (In and P powders). I consider the various kinds of InP morphologies grown using this method. The effect of source temperature on the stoichiometry and optical properties of nanowires is studied. Lasing behavior has been seen in InP nanostructures, showing superior material quality of InP.
InGaP alloy nanowires were grown using compound and elemental sources. Nanowires grown using compound sources have significant oxide incorporation and showed kinky morphology. Nanowires grown using elemental sources had no oxide and showed better optical quality. Also, these samples showed a tunable alloy composition across the entire substrate covering more than 50% of the InGaP alloy system. Integrated intensity showed that the bandgap of the nanowires changed from indirect to direct bandgap with increasing Indium composition. InGaP alloy nanowires were compared with Gallium Phosphide nanowires in terms of PL emission, using InGaP nanowires it is possible to grow nanowires free of defects and oxygen impurities, which are commonly encountered in GaP nanowires.