Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
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
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item An Integrated Photonic Platform For Quantum Information Processing(2021) Dutta, Subhojit; Waks, Edo EW; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Quantum photonics provides a powerful toolbox with vast applications ranging from quantum simulation, photonic information processing, all optical universal quantum computation, secure quantum internet as well as quantum enhanced sensing. Many of these applications require the integration of several complex optical elements and material systems which pose a challenge to scalability. It is essential to integrate linear and non-linear photonics on a chip to tackle this issue leading to more compact, high bandwidth devices. In this thesis we demonstrate a pathway to achieving several components in the quantum photonic toolbox on the same integrated photonic platform. We focus particularly on two of the more nontrivial components, a single photon source and an integrated quantum light-matter interface. We address the problem of a scalable, chip integrated, fast single photon source, by using atomically thin layers of 2D materials interfaced with plasmonic waveguides. We further embark on the challenge of creating a new material system by integrating rare earth ions with the emerging commercial platform of thin film lithium niobate on insulator. Rare earth ions have found widespread use in classical and quantum information processing. However, these are traditionally doped in bulk crystals which hinder their scalability. We demonstrate an integrated photonic interface for rare earth ions in thin film lithium niobate that preserves the optical and coherence properties of the ions. This combination of rare earth ions with the chip-scale active interface of thin film lithium niobate opens a plethora of opportunities for compact optoelectronic devices. As an immediate application we demonstrate an integrated optical quantum memory with a rare earth atomic ensemble in the thin film. The new light matter interface in thin film lithium niobate acts as a key enabler in an already rich optical platform representing a significant advancement in the field of integrated quantum photonics.Item HIGH EFFICIENCY CIS SOLAR CELLS BY A SIMPLE TWO-STEP SELENIZATION PROCESS AND WAVEGUIDE BRAGG GRATINGS IN INTEGRATED PHOTONICS(2019) Zhang, Yang; Dagenais, Mario; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Part I: High Efficiency CIS Solar Cells with Simple Fabrication Method CIS has a very high optical absorption coefficient, which makes it able to absorb more than 90% of the incident photons with energies higher than 1.04 eV within 1-2 µm thickness. Because of the high absorption coefficient and low bandgap, high quality CIS solar cells can have a very high short circuit current compared with other thin film material or other type of solar cells. We offer a very simple two-step process based on annealing stacked elemental layers under selenium vapor within a graphite box, followed by a potassium fluoride postdeposition treatment, which is a low-cost and highly manufacturable approach. We are able to reproducibly achieve above 12% conversion efficiency, with the champion cell exhibiting near-record 14.7% efficiency. Our results indicate that perhaps the CIS system is less sensitive to elaborate processing steps and details than previously thought. This simple approach offers a very useful experimental platform from which to study a variety of thin film PV research topics, including the possibility of producing tandem solar cell by also using perovskite. Part II: Waveguides Bragg Gratings in Integrated Photonics Integrated photonics on silicon-based material combines two great inventions of the last century: silicon technology and photonic technology. It is paving the way for a monolithically integrated optoelectronic platform on a single chip. Being a prevailing research topic in the past decade, it has seen tremendous progress with the successful development of high-performance components. Among all integrated photonics platforms, the silicon nitride planar waveguide platform provides benefits like low optical losses, transparency over a wide wavelength range (400-2350 nm), compatibility with CMOS and wafer-scale foundry processes, and high-power handling capabilities. In this part, waveguides Bragg gratings are investigated to improve the performance of several integrated photonics components. An 83-dB rejection ratio pump filter using a periodic waveguide Bragg grating with an efficient z-shape waveguide design to suppress the TM mode and avoid scattered modes is demonstrated. Fabry-Perot cavity enhanced four-wave mixing devices are optimized based on a numerical model developed with an ABCD matrix method and four-wave mixing in a Fabry-Perot cavity that uses grating is demonstrated experimentally. Finally, to reduce the pixel size and power consumption of optical phased array for virtual reality applications, complex waveguide Bragg gratings are generated via both Layer Peeling/Adding algorithm and genetic algorithm to support slow-light modes over certain bandwidth.