Browsing by Subject "Integrated"
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Item Polymer-based integrated photonic devices for interconnects(2018-06-19) Pan, Zeyu; Chen, Ray T.; Pan, Zhigang; Ho, Paul S.; Wang, Yaguo; Tao, HuIntegrated photonic devices based on optical waveguides have been extensively studied for various applications, especially the high-speed intra- and inter-chip interconnects. Usually, a waveguide contains a core with high refractive index and cladding with lower refractive index. Among various waveguides, silicon, polymer, and silicon-polymer hybrid devices are the most promising candidates for low cost, small size, light weight, and low power consumption (CSWaP) optical interconnect. Firstly, silicon-based optical devices can be fabricated using CMOS compatible nanofabrication technology, which is already widely used to manufacture integrated circuits. Silicon photonic devices can have very small footprint and enable high density photonic circuits, due to high refractive index contrast. However, one of the intrinsic obstacles is the absence of χ⁽²⁾-nonlinearity in unstrained silicon due to its centrosymmetric crystal structure, making modulating photons on silicon platform a great challenge. Secondly, polymer-based devices have been found very attractive, owing to the advantages of high thermo-optic (TO) or electro-optic (EO) coefficient, high transparency in the telecommunication wavelength windows, and fabrication feasibility over large areas on printed circuit board (PCB) or other kinds of substrates. The roll-to-roll (R2R) compatible imprinting and ink-jet printing for developing polymer-based devices on flexible or rigid substrates enable large-area, light-weight, low-cost optical interconnects. However, due to the low refractive index contrast, the polymer photonic devices always require large footprint. Finally, the silicon-organic hybrid (SOH) platform enables the marriage of the best of these two materials and thus has been receiving substantial attention. In this dissertation, integrated photonic devices based on silicon, polymer, or hybrid platform will be presented. First, high-efficiency quasi-vertical tapers for polymer waveguide based inter-board optical interconnects will be demonstrated. A triangular-shape tapered structure is adopted above the waveguide core to transform a fiber mode into a single mode polymer rib waveguide mode as an optical mode transformer. A coupling loss of 1.79±0.30 dB and 2.23±0.31 dB per coupler for the quasi-TM and quasi-TE mode respectively have been experimentally demonstrated, across the C and L bands (1535 nm – 1610 nm). Then, a reconfigurable thermo-optic polymer switch based true-time-delay network will be analyzed and demonstrated. Thirdly, I will show a novel subwavelength-grating waveguide ring resonator based high-speed modulators, which is the largest bandwidth and the most compact footprint that has been demonstrated for the ring resonators on the silicon-organic hybrid (SOH) platform. Finally, the on-chip time-division multiplexing and de-multiplexing system will be designed and analyzed.Item Silo-busting : the Texas effort to make mental health care mainstream(2017-12-07) Covington, Caroline Harris; Dahlby, Tracy; Oppenheimer, DanielAmid the ongoing political debate over health care, a revolutionary approach to the actual practice of medicine is quietly taking root nationwide, and especially in Texas. So-called “integrated care,” in which collaborative teams treat patients’ mental and physical health together, is becoming particularly popular despite Texas’ poor health care track record. Integrated care breaks down the traditional “silos” that have kept mental and physical health care separate throughout the years, and claims to make patients healthier for less money. But Texas will have to overcome several logistical, training and financial hurdles before it can become the norm.Item The technical potential of renewable natural gas (RNG) in the United States, and the economic potential of methanation-derived RNG in Texas(2014-12) Ólafsson, Brynjólfur Víðir; Webber, Michael E., 1971-Renewable Natural Gas (RNG) is a low-carbon fuel source that is derived from the anaerobic digestion (AD) or thermal gasification (TG) of biomass, or produced using renewable electricity through the methanation of carbon dioxide. This thesis uses a thermodynamic balance to determine the total technical potential of RNG in the United States, as well as the future technical potential of methanation-derived RNG based on growth curves for renewable electricity. Furthermore, this work establishes an analytic decision-making framework for determining on a rolling basis, from an economic standpoint, whether to sell electricity directly to the grid, or produce and sell methanation-derived RNG. This framework is used to establish the economic potential of RNG, based on Texas wind resources. This work details the formulation of a model that determines which production option generates more marginal profit, based on fluctuating electricity and gas prices. The model also aggregates the total amount of electricity and RNG sold, assuming that the main objective is to maximize the marginal profit of integrated wind- and methanation facilities. This work concludes that the annual technical potential of methanation-derived RNG nationally was 1.03 Quads in 2011. The technical potential of biomass-derived RNG was 9.5 Quads. Thus, the total 2011 technical potential of RNG in the United States was 10.5 Quads, or equal to roughly 43% of the total US consumption of natural gas that year. Assuming a constant, 80% electrolyser efficiency, the technical potential of methanation-derived RNG is expected to rise at an average rate of 1.4% per year, following growth curves for renewable power, until the year 2040, when it will be 1.54 Quads. The 2011 economic potential of methanation-derived RNG in Texas was between 2.06×10⁷ MMBTU and 3.19×10⁷ MMBTU, or between 19.4% and 30.1% of the corresponding annual technical potential. Furthermore, the total marginal profit increase from introducing the option of producing and selling methanation-derived RNG was around $366 million, given a ‘best case scenario’ for the state of Texas.