Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
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Item SILICON NITRIDE INTEGRATED PHOTONIC DEVICES AND THEIR APPLICATIONS IN ASTRONOMY AND QUANTUM PHYSICS(2022) Zhan, Jiahao; Dagenais, Mario; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The photonics technology has revolutionized the telecommunication industry in the past 40 years with the deployment of the undersea fiber-optic network. Nowadays, with the maturity of silicon photonics technology, the integrated photonic platform is enabling more and more cutting-edge technologies, such as optical transceivers for data center connectivity, automotive LiDARs for self-driving vehicles, the next-generation astronomical instrumentation and nearterm photonic quantum computers, to name a few. In recent years, silicon nitride (Si3N4) material has attracted a significant amount of attention mainly due to the ultra-low loss that can be achieved. Compared to silicon, Si3N4 has a much wider transparency window, and does not suffer from two-photon absorption and free-carrier absorption over the telecommunication band. The relatively low refractive index of Si3N4 also means less sensitivity of optical modes to the waveguide sidewall roughness, therefore reducing the scattering loss. In this dissertation, I will first give an introduction of integrated photonics, and a brief overview of some novel applications and current trends. Next I will graphically show our methods for device fabrication and characterization, and then demonstrate a few integrated photonic devices implemented on the Si3N4 material platform, including Bragg gratings, multimode interferometers, polarization beam splitters, and polarization rotators, with an in-depth discussion of their potentialapplications, principles of operation, simulation and experimental results. I will then embark on a new chapter on arrayed waveguide gratings (AWGs), with emphasis on its application in integrated astronomical spectrometers. To obtain a continuous two-dimensional spectrum, cleaving at the output focal plane of the AWGis required. I will discuss and demonstrate a three-stigmatic-point AWG, which provides an elegant solution to the non-flat focal plane issue in traditional Rowland AWGs. This work is a critical step towards the development of an efficientand miniaturized astronomical spectrograph for the upcoming extremely-large telescopes. Next, I will introduce a one-dimensional nanobeam cavity enabled by a slow-light waveguide. A cubic relation between the quality factor and the length of the cavity will be derived and experimental verification will be demonstrated. The current progress towards the investigation of the Purcell effect of this nanobeam cavity will be discussed, including the platform and the loss characterization of the deposited amorphous silicon material. In the final chapter, I will first summarize the major conclusions from the previous chapters. Then I will briefly discuss some future research directions extending the work in this thesis, including ultra-broadband polarization beam splitter, the development of an on-chip Bell state analyzer, and the design of a polarization-insensitive flat-focal-field spectrometer.Item CONCENTRATION ENHANCEMENT AND DEVICE FABRICATION FOR THE IMPROVED PERFORMANCE OF GRADIENT ELUTION MOVING BOUNDARY ELECTROPHORESIS(2014) Sikorsky, Alison Anne; Fourkas, John t; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Many recent efforts in the field of microfluidics have been focused on reducing the size and the complexity of devices and on simplifying the methods of analysis performed with them. Gradient elution moving boundary electrophoresis (GEMBE) is a recently described counterflow electrophoresis method that was developed to simplify the analysis of ions in complex matrices. In this thesis, the improvement of the limit of detection of GEMBE and reduction of the GEMBE channel length is investigated. Integration of simple and robust device components required for the successful adaptation of many analytical methods to multiplexed and field-portable devices often has negative effects on detection sensitivity, such as in the optical detection components in a capillary electrophoresis (CE) system. One of the simplest methods to improve sensitivity in the CE field is known as sample stacking. This method involves preparing the sample in a buffer with a different concentration (and conductivity) than that of the run buffer, such that when an electric field is applied the analyte concentration is increased at the boundary between the two different buffer concentrations. A method in which the sample is prepared in a buffer at a lower concentration than the run buffer has been implemented. This method achieves a significantly greater signal enhancement than expected for sample stacking. The concentration enhancement ability of this method is demonstrated utilizing GEMBE with channel current detection. Current GEMBE device construction methods impose limitations on the minimum length of the separation channel. One technique well suited for minimizing the size of the GEMBE separation channel is multiphoton absorption polymerization (MAP). Because MAP is a non-linear optical fabrication method, polymerization is limited to a small region near the focal point of a laser beam. As a result, three-dimensional structures with small feature sizes can be easily created. The 3D capabilities of MAP have been exploited to create channels with circular cross sections and ~300 μm lengths for GEMBE. The integration of device components fabricated with MAP and molded with PMDS allows visualization of the GEMBE separations, and provides insights into the effect of channel length on GEMBE step width.Item Baltimore Center for Making: A Public Interface for Creative Culture(2010) Canon, Kira; Williams, Isaac S; Architecture; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Our modern society depends on consumerism in order to match products and services with the people who need them; however, in its current form this process often comes at great expense to the finite resources of the environment. In addition, the global economy has created work places where workers are physically very distant from their peers, causing the individual to lose the empathetic face-to-face connections that are necessary for emotional fulfillment. Moreover, the work products of this information age are often ethereal, depriving workers of the satisfaction inherent in seeing the physical result of their hours of labor. This thesis imagines a civic institution that encourages different groups of people to share resources and empowers them to use their hands to make things in the material world. Hybrid site and program conditions create a palimpsest architectural proposal that seeks to galvanize the community of Baltimore around design and making.Item Fabrication of Bragg Gratings Using Interferometric Lithography(2007-04-30) Pizarro, Ricardo Andres; Goldhar, Julius; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A setup has been designed and realized for the fabrication of Bragg Gratings in edge emitting semiconductor laser. In this setup a HeCd laser, at 325nm, is used in a Lloyd's mirror configuration, to interferometrically expose a sinusoidal grating on photoresist. The dilution of photo-resistant (PR) material allows for a spincoat thickness of 50nm which is needed to minimize standing waves in the photo-resist that lead to a nonuniform exposure. Variations of exposure time show the progression of photo-resist gratings. Etching recipes using both dry and wet etching techniques were successfully used to transfer the grating pattern into semiconductor material. Bragg Gratings with period of 250nm in InP and InGaAs have been characterized with an Atomic Force Microscope to have a grating height of over 100nm.