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Nanophotonics studies the interaction of light with nanoscale devices and nanostructures. This thesis focuses on developing nanoscale devices for optical modulation (saturable absorber and all-optical modulator) and investigating light scattering from nanoparticles for underwater navigation and energy sector application. Saturable absorbers and all-optical modulators are essential to generate ultrashort high-power laser pulses and high-speed communications. Graphene-based devices are broadband, ultrafast, and compatible with different substrates and fibers. Nevertheless, the required fluence to saturate or modulate the optical signal with graphene is still high to realize low-threshold, compact broadband devices, which are essential for many applications. This dissertation emphasizes that the strong light-matter interaction in graphene-plasmonic hybrid metasurface greatly enhances monolayer graphene’s saturable absorption and optical signal modulation effect while maintaining graphene’s ultrafast carrier dynamics. Furthermore, based on this concept, simulation models and experimental demonstrations are presented in this dissertation to demonstrate both subwavelength (~λ/5 in near-infrared and ~λ/10 in mid-infrared) thick graphene-based saturable absorber (with record-low saturation fluence (~0.1μJ/cm2), and ultrashort recovery time (~60fs) at near-infrared wavelengths) and all-optical modulators ( with 40% reflection modulation at 6.5μm with ~55μJ/cm2 pump fluence and ultrafast relaxation time of ~1ps at 1.56μm with less than 8μJ/cm2 pump fluence).
Underwater navigation is essential for various underwater vehicles. However, there is no reliable method for underwater navigation. This dissertation presents a numerical simulation model and algorithm for navigation based on underwater polarization mapping data. With the methods developed, for clear water in the swimming pool, it is possible to achieve a sun position error of 0.35˚ azimuth and 0.03˚ zenith angle, and the corresponding location prediction error is ~23Km. For turbid lake water, a location determination error of ~100Km is achieved. Furthermore, maintenance of heliostat mirrors and receiver tubes is essential for properly operating concentrated solar power (CSP) plants. This dissertation demonstrates a fast and field deployable inspection method to measure the heliostat mirror soiling levels and receiver tube defect detection based on polarization images. Under sunny and clear sky conditions, accurate reflection efficiency (error ~1%) measurement for mirrors with different soiling levels is achieved, and detection of receiver tube defects is demonstrated.
ContributorsRafique, Md Zubair Ebne (Author) / Yao, Yu (Thesis advisor) / Palais, Joseph (Committee member) / Zhang, Yong-Hang (Committee member) / Sukharev, Maxim (Committee member) / Arizona State University (Publisher)
Created2022
Description
Polarization detection and control techniques play essential roles in various applications, including optical communication, polarization imaging, chemical analysis, target detection, and biomedical diagnosis. Conventional methods for polarization detection and polarization control require bulky optical systems. Flat optics opens a new way for ultra-compact, lower-cost devices and systems for polarization detection and control. However, polarization measurement and manipulating devices with high efficiency and accuracy in the mid-infrared (MIR) range remain elusive. This dissertation presented design concepts and experimental demonstrations of full-Stokes parameters detection and polarization generation devices based on chip-integrated plasmonic metasurfaces with high performance and record efficiency. One of the significant challenges for full-Stokes polarization detection is to achieve high-performance circular polarization (CP) filters. The first design presented in this dissertation is based on the direct integration of plasmonic quarter-wave plate (QWP) onto gold nanowire gratings. It is featured with the subwavelength thickness (~500nm) and extinction ratio around 16. The second design is based on the anisotropic thin-film interference between two vertically integrated anisotropic plasmonic metasurfaces. It provides record high efficiency (around 90%) and extinction ratio (>180). These plasmonic CP filters can be used for circular, elliptical, and linear polarization generation at different wavelengths. The maximum degree of circular polarization (DOCP) measured from the sample achieves 0.99998.
The proposed CP filters were integrated with nanograting-based linear polarization (LP) filters on the same chip for single-shot polarization detection. Full-Stokes measurements were experimentally demonstrated with high accuracy at the single wavelength using the direct subtraction method and over a broad wavelength range from 3.5 to 4.5mm using the Mueller matrix method. This design concept was later expanded to a pixelized array of polarization filters. A full-Stokes imaging system was experimentally demonstrated based on integrating a metasurface with pixelized polarization filters arrays and an MIR camera.
ContributorsBai, Jing (Author) / Yao, Yu (Thesis advisor) / Balanis, Constantine A. (Committee member) / Wang, Liping (Committee member) / Zhang, Yong-Hang (Committee member) / Arizona State University (Publisher)
Created2021
Description
Polarization imaging and polarization microscopy is of great interest in industrial inspection, defense, biomedical and clinical research, food safety, etc. An ideal polarization imaging system suitable for versatile applications should be full-Stokes, compact, broadband, fast, and highly accurate within a large operation angle. However, such a polarization imaging system remains elusive among state-of-the-art technology. Recently, flat optics based on metasurfaces have been explored for polarization detection and imaging. Compared with state-of-art, metasurface-based solutions have the advantages of compactness, great design flexibility, and feasibility for on-chip integration. This dissertation reports a dual wavelength (630 to 670nm and 480nm to 520nm) chiral metasurfaces featured with sub-wavelength dimension, extinction ratio over 10 across a broad operation bandwidth (175nm) and efficiency over 60%, which can be used for detection and generation of circular polarization (Chapter 2).
This dissertation then reports a chip-integrated full-Stokes polarimetric Complementary metal–oxide–semiconductor (CMOS) imaging sensor based on metasurface polarization filter arrays (MPFA) mentioned above. The sensor has high measurement accuracy of polarization states with an angle of view up to 40°. Calibration and characterization of the device are demonstrated, whereby high polarization states measurement accuracy (measurement error <4%) at incidence angle up to ±20° and full Stokes polarization images of polarized objects are shown. (Chapter 3).
A scalable fabrication approach based on nano imprint lithography is demonstrated, with improved fabrication efficiency, lower cost, and higher optical performance up to 10 times compared to EBL process. (Chapter 4).
Several polarization imaging applications including a dual-camera full-Stokes underwater polarization navigation system are discussed. Polarization mapping under clear sky and clear water is demonstrated for proof concept. Enhancing contrast of objects through turbid water and polarization images of silver dendrites are also discussed (Chapter 5).
Though distinctive in its advantages in rich polarization information, most existing Mueller matrix microscope (MMM) operate at single mode, narrow bandwidth with bulky components. This dissertation reports a compact, dual wavelength, dual mode MMM with satisfactory measurement accuracy (Mueller matrix (MM) measurement error≤ 2.1%) using polarimetric imaging sensor mentioned previously, MM imaging of photonic structures, bio-tissues, etc are demonstrated for proof of concept (Chapter 6).
ContributorsZuo, Jiawei (Author) / Yao, Yu (Thesis advisor) / Wang, Chao (Thesis advisor) / Palais, Joseph (Committee member) / Sinha, Kanupriya (Committee member) / Arizona State University (Publisher)
Created2023
Description
Given the "New Nine Measures" for capital market reform, a policy document issued by the State Council of China, the development of markets for interest rate derivatives, such as treasury futures, becomes an increasingly important task. Several shortcomings of the existing treasury futures market have been noted: including low market liquidity, singular investor composition, restrict contract terms, and low hedging demand.
This study contributes to a better understanding of the treasury futures market by analyzing changes in China treasury futures market regulations and their impact on market liquidity of treasury futures. Found that compared with the mature market, China treasury futures market exists liquidity shortage, the trading system, market structure and the division of regulatory are factors which influence the liquidity of China treasury futures market.
This study found that reducing transaction costs for further optimization of the width and depth of China treasury futures market are not obvious by using quantitative analysis method, expanding the smallest change price can optimize the market depth, reducing transaction costs and expanding smallest change price can optimize the immediacy, volume and hosting amount. In addition, the bond market will also influence the treasury futures market, the price fluctuations and the morphology of the yield curve of bond market have significant influence on width, depth and holdings of market.
The system of China treasury futures market needs to be optimized by expanding the smallest change price and reducing transaction costs. The market structure needs to be optimized by establishing unified bond market and enriching investor structure.
These findings have significant theoretical and practical implications. The study also provides policy recommendations for the design and establishment of treasury futures market to the regulatory agencies.
This study contributes to a better understanding of the treasury futures market by analyzing changes in China treasury futures market regulations and their impact on market liquidity of treasury futures. Found that compared with the mature market, China treasury futures market exists liquidity shortage, the trading system, market structure and the division of regulatory are factors which influence the liquidity of China treasury futures market.
This study found that reducing transaction costs for further optimization of the width and depth of China treasury futures market are not obvious by using quantitative analysis method, expanding the smallest change price can optimize the market depth, reducing transaction costs and expanding smallest change price can optimize the immediacy, volume and hosting amount. In addition, the bond market will also influence the treasury futures market, the price fluctuations and the morphology of the yield curve of bond market have significant influence on width, depth and holdings of market.
The system of China treasury futures market needs to be optimized by expanding the smallest change price and reducing transaction costs. The market structure needs to be optimized by establishing unified bond market and enriching investor structure.
These findings have significant theoretical and practical implications. The study also provides policy recommendations for the design and establishment of treasury futures market to the regulatory agencies.
ContributorsMa, Jun (Author) / Gu, Bin (Thesis advisor) / Chen, Hong (Thesis advisor) / Wang, Tan (Committee member) / Arizona State University (Publisher)
Created2016
Description
III-nitride InGaN light-emitting diodes (LEDs) enable wide range of applications in solid-state lighting, full-color displays, and high-speed visible-light communication. Conventional InGaN quantum well LEDs grown on polar c-plane substrate suffer from quantum confined Stark effect due to the large internal polarization-related fields, leading to a reduced radiative recombination rate and device efficiency, which limits the performance of InGaN LEDs in high-speed communication applications. To circumvent these negative effects, non-trivial-cavity designs such as flip-chip LEDs, metallic grating coated LEDs are proposed. This oral defense will show the works on the high-modulation-speed LEDs from basic ideas to applications. Fundamental principles such as rate equations for LEDs/laser diodes (LDs), plasmonic effects, Purcell effects will be briefly introduced. For applications, the modal properties of flip-chip LEDs are solved by implementing finite difference method in order to study the modulation response. The emission properties of highly polarized InGaN LEDs coated by metallic gratings are also investigated by finite difference time domain method.
ContributorsChen, Hong (Author) / Zhao, Yuji (Thesis advisor) / Yao, Yu (Committee member) / Wang, Liping (Committee member) / Arizona State University (Publisher)
Created2016
Description
Conductance fluctuations associated with quantum transport through quantumdot systems are currently understood to depend on the nature of the corresponding classical dynamics, i.e., integrable or chaotic. There are a couple of interesting phenomena about conductance fluctuation and quantum tunneling related to geometrical shapes of graphene systems. Firstly, in graphene quantum-dot systems, when a magnetic field is present, as the Fermi energy or the magnetic flux is varied, both regular oscillations and random fluctuations in the conductance can occur, with alternating transitions between the two. Secondly, a scheme based on geometrical rotation of rectangular devices to effectively modulate the conductance fluctuations is presented. Thirdly, when graphene is placed on a substrate of heavy metal, Rashba spin-orbit interaction of substantial strength can occur. In an open system such as a quantum dot, the interaction can induce spin polarization. Finally, a problem using graphene systems with electron-electron interactions described by the Hubbard Hamiltonian in the setting of resonant tunneling is investigated.
Another interesting problem in quantum transport is the effect of disorder or random impurities since it is inevitable in real experiments. At first, for a twodimensional Dirac ring, as the disorder density is systematically increased, the persistent current decreases slowly initially and then plateaus at a finite nonzero value, indicating remarkable robustness of the persistent currents, which cannot be discovered in normal metal and semiconductor rings. In addition, in a Floquet system with a ribbon structure, the conductance can be remarkably enhanced by onsite disorder.
Recent years have witnessed significant interest in nanoscale physical systems, such as semiconductor supperlattices and optomechanical systems, which can exhibit distinct collective dynamical behaviors. Firstly, a system of two optically coupled optomechanical cavities is considered and the phenomenon of synchronization transition associated with quantum entanglement transition is discovered. Another useful issue is nonlinear dynamics in semiconductor superlattices caused by its key potential application lies in generating radiation sources, amplifiers and detectors in the spectral range of terahertz. In such a system, transition to multistability, i.e., the emergence of multistability with chaos as a system parameter passes through a critical point, is found and argued to be abrupt.
Another interesting problem in quantum transport is the effect of disorder or random impurities since it is inevitable in real experiments. At first, for a twodimensional Dirac ring, as the disorder density is systematically increased, the persistent current decreases slowly initially and then plateaus at a finite nonzero value, indicating remarkable robustness of the persistent currents, which cannot be discovered in normal metal and semiconductor rings. In addition, in a Floquet system with a ribbon structure, the conductance can be remarkably enhanced by onsite disorder.
Recent years have witnessed significant interest in nanoscale physical systems, such as semiconductor supperlattices and optomechanical systems, which can exhibit distinct collective dynamical behaviors. Firstly, a system of two optically coupled optomechanical cavities is considered and the phenomenon of synchronization transition associated with quantum entanglement transition is discovered. Another useful issue is nonlinear dynamics in semiconductor superlattices caused by its key potential application lies in generating radiation sources, amplifiers and detectors in the spectral range of terahertz. In such a system, transition to multistability, i.e., the emergence of multistability with chaos as a system parameter passes through a critical point, is found and argued to be abrupt.
ContributorsYing, Lei (Author) / Lai, Ying-Cheng (Thesis advisor) / Vasileska, Dragica (Committee member) / Chen, Tingyong (Committee member) / Yao, Yu (Committee member) / Arizona State University (Publisher)
Created2016
Description
The city of Shanghai is set to become an international financial center (IFC) by 2020. To achieve this goal, it is imperative to clearly define the key characteristics of an IFC. In this study I draw from recent research on the ranking of IFCs to develop an index of these key characteristics that can be used to assess a city’s standings as an IFC. Based on a review of prior research, I first put together a comprehensive list of the indicators that have been used to evaluate IFCs, which includes six first-level indicators and 34 second-level indicators. I then collect information on all these indicators from public sources for the following eight cities each year from 2011 to 2013: London, New York, Paris, Hong Kong, Tokyo, Singapore, Beijing and Shanghai. Next, I conduct a principal component analysis (PCA) on my data, and obtain four primary factors that contain most information of the original 34 indicators. The first factor covers 18 of the original indicators and reflects a city’s level of development in general business environment. The second factor covers 10 of the original indicators and reflects a city’s level of development in financial markets. The third factor covers three of the original indicators and reflects a city’s level of economic vitality. The fourth factor covers three of the original indicators and reflects a city’s level of the costs of living. I further calculate the composite scores for the above eight cities along these four factors, and find that these eight cities can be classified into three tiers on the basis of their scores. The first tier consists of New York and London; the second tier consists of Singapore, Hong Kong, Paris and Tokyo; and the third tier consists of Shanghai and Beijing. I also find that Shanghai has been making progress in its scores along these four factors over the last three years, especially regarding financial market development, economic vitality, and cost of living. What Shanghai needs to focus on next is to improve its business environment so that it can move up to the second tier in IFC status.
ContributorsWang, Weiren, Ph.D (Author) / Yao, David (Thesis advisor) / Gu, Bin (Thesis advisor) / Chen, Hong (Committee member) / Arizona State University (Publisher)
Created2015
Description
Nanowires are one-dimensional (1D) structures with diameter on the nanometer scales with a high length-to-diameter aspect ratio. Nanowires of various materials including semiconductors, dielectrics and metals have been intensively researched in the past two decades for applications to electrical and optical devices. Typically, nanowires are synthesized using the vapor-liquid-solid (VLS) approach, which allows defect-free 1D growth despite the lattice mismatch between nanowires and substrates. Lattice mismatch issue is a serious problem in high-quality thin film growth of many semiconductors and non-semiconductors. Therefore, nanowires provide promising platforms for the applications requiring high crystal quality materials.
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.
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.
ContributorsLiu, Zhicheng (Author) / Ning, Cun-Zheng (Thesis advisor) / Palais, Joseph (Committee member) / Yu, Hongbin (Committee member) / Yao, Yu (Committee member) / Arizona State University (Publisher)
Created2015
Description
Using historical data from the third-party payment acquiring industry, I develop a statistical model to predict the probability of fraudulent transactions by the merchants. The model consists of two levels of analysis – the first focuses on fraud detection at the store level, and the second focuses on fraud detection at the merchant level by aggregating store level data to the merchant level for merchants with multiple stores. My purpose is to put the model into business operations, helping to identify fraudulent merchants at the time of transactions and thus mitigate the risk exposure of the payment acquiring businesses. The model developed in this study is distinct from existing fraud detection models in three important aspects. First, it predicts the probability of fraud at the merchant level, as opposed to at the transaction level or by the cardholders. Second, it is developed by applying machine learning algorithms and logistical regressions to all the transaction level and merchant level variables collected from real business operations, rather than relying on the experiences and analytical abilities of business experts as in the development of traditional expert systems. Third, instead of using a small sample, I develop and test the model using a huge sample that consists of over 600,000 merchants and 10 million transactions per month. I conclude this study with a discussion of the model’s possible applications in practice as well as its implications for future research.
ContributorsZhou, Ye (Author) / Chen, Hong (Thesis advisor) / Gu, Bin (Thesis advisor) / Chao, Xiuli (Committee member) / Arizona State University (Publisher)
Created2015
Description
This thesis starts with an analysis of the current situation of the pharmaceutical industry in China, and discusses the strategic mergers and acquisitions (M&A) by small and medium-sized enterprises (SMEs) in the pharmaceutical industry in China. It elaborates on the rationale for the development of the mergers and acquisitions of the pharmaceutical SMEs. Then a literature review is provided on the causes of corporate mergers and acquisitions such as the economies of scale, synergistic effect, transaction costs, market power, and strategic diversification.Next,the thesis analyzes the underlying rationale for the M&A transactions in the pharmaceutical industry in China, and explores the likely path of successful value creation for pharmaceutical SMEs in China. Specifically, with five in-depth case studies of M&A transactions of pharmaceutical firms, this thesis reveals the critical success factors leading to value creation and growth in the practice of mergers and acquisitions of the pharmaceutical SMEs in China.
ContributorsZhou, Yan (Author) / Pei, Ker-Wei (Thesis advisor) / Chen, Hong (Committee member) / Shen, Wei (Committee member) / Arizona State University (Publisher)
Created2015