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Articles 1081 - 1110 of 1749

Full-Text Articles in Electromagnetics and Photonics

Design And Analysis Of Circularly Polarized Electrically Small Antennas, Jesse R. Ludwig Jan 2014

Design And Analysis Of Circularly Polarized Electrically Small Antennas, Jesse R. Ludwig

College of Graduate Studies: Theses & Dissertations

A growing need for efficient wireless communication is prevalent in the world in which we live. From cell phones to television to GPS applications, wireless communications are vital in consumer electronics and military applications. In these applications, a miniaturized antenna is sometimes necessary for reducing overall size of the communication system. For many satellite based communication applications, circular polarization in antennas is needed for efficient communication. In this thesis, the miniaturization technique known as T-top loading is utilized on two novel antenna designs. One design is an electrically small, circularly polarized planar cross dipole and the other design is a …

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Reconfigurable Microstrip Antennas With Tunable Radiation Pattern Characteristics, Ahmed Khidre Jan 2014

Reconfigurable Microstrip Antennas With Tunable Radiation Pattern Characteristics, Ahmed Khidre

Electronic Theses and Dissertations

Reconfigurable beam antenna systems are capable of changing their radiation characteristics in real time, such as beam direction, beam shape, beamwidth, etc. Such antenna system is desired for various wireless applications because of many reasons among them; it helps to enhance signal strength received from an intended target, mitigates interference, and accommodates sudden changes in traffic demand of wireless networks. It might also help to reduce the deployment cost of wireless networks infrastructures. In this dissertation, designs for reconfigurable beam microstrip antennas with tunable radiation characteristics have been proposed. The method to achieve these designs is the reconfigurable parasitic element …

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Modification Of Plasmonic Nano Structures' Absorption And Scattering Under Evanescent Wave Illumination Above Optical Waveguides Or With The Presence Of Different Material Nano Scale Atomic Force Microscope Tips, Gazi Mostafa Huda Jan 2014

Modification Of Plasmonic Nano Structures' Absorption And Scattering Under Evanescent Wave Illumination Above Optical Waveguides Or With The Presence Of Different Material Nano Scale Atomic Force Microscope Tips, Gazi Mostafa Huda

Theses and Dissertations--Electrical and Computer Engineering

The interaction of an evanescent wave and plasmonic nanostructures are simulated in Finite Element Method. Specifically, the optical absorption cross section (Cabs) of a silver nanoparticle (AgNP) and a gold nanoparticle (AuNP) in the presence of metallic (gold) and dielectric (silicon) atomic force microscope (AFM) probes are numerically calculated in COMSOL. The system was illuminated by a transverse magnetic polarized, total internally reflected (TIR) waves or propagating surface plasmon (SP) wave. Both material nanoscale probes localize and enhance the field between the apex of the tip and the particle. Based on the absorption cross section equation the author …

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Broadband Approaches And Beam-Scanning Techniques For Reflectarray Antenna, Yilin Mao Jan 2014

Broadband Approaches And Beam-Scanning Techniques For Reflectarray Antenna, Yilin Mao

Electronic Theses and Dissertations

Reflectarray antennas combine the numerous advantages of reflector antennas and phased array antennas and create a hybrid high-gain antenna with a low-profile, low-mass, easy-fabrication, and diversified radiation performance. However, it still has some inherent drawbacks, such as limited bandwidth and scanning range, which are targeted in this dissertation. At first, the array theory approach for radiation analysis of reflectarray antennas is described and implemented. Numerical results are then presented and compared with reference results to confirm its reliability. As the most critical influential factor to the reflectarray bandwidth, the element bandwidth was studied at first, and the effects of element …

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Analysis And Design Of Low Profile Multiband Multifunctional Antenna Arrays, Walker F. Hunsicker Jan 2014

Analysis And Design Of Low Profile Multiband Multifunctional Antenna Arrays, Walker F. Hunsicker

Electronic Theses and Dissertations

Light-weight phased array antennas for aerospace and mobile applications require utilizing the same antenna aperture to provide multiple functions with dissimilar radiation pattern specifications (e.g., multiband operation for communications and tracking). Multi-functional antennas provide advantages over aggregate antenna clusters by reducing space requirements, and can aid in the optimal placement of all required apertures to provide adequate isolation between channels. Furthermore, the combination of antenna apertures into a comgeometry mitigates co-site installation issues by addressing interference within the integrated radiator design itself as opposed to the extensive analysis which is required to configure multiple radiators in close proximity. The combination …

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3d Printed Electromagnetic Transmission And Electronic Structures Fabricated On A Single Platform Using Advanced Process Integration Techniques, Paul I. Deffenbaugh Jan 2014

3d Printed Electromagnetic Transmission And Electronic Structures Fabricated On A Single Platform Using Advanced Process Integration Techniques, Paul I. Deffenbaugh

Open Access Theses & Dissertations

3D printing has garnered immense attention from many fields including in-office rapid prototyping of mechanical parts, outer-space satellite replication, garage functional firearm manufacture, and NASA rocket engine component fabrication. 3D printing allows increased design flexibility in the fabrication of electronics, microwave circuits and wireless antennas and has reached a level of maturity which allows functional parts to be printed. Much more work is necessary in order to perfect the processes of 3D printed electronics especially in the area of automation. Chapter 1 shows several finished prototypes of 3D printed electronics as well as newly developed techniques in fabrication. Little is …

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Self-Heating Control Of Edge Emitting And Vertical Cavity Surface Emitting Lasers, Yu Zhang Jan 2014

Self-Heating Control Of Edge Emitting And Vertical Cavity Surface Emitting Lasers, Yu Zhang

Electronic Theses and Dissertations

Self-heating leads to temperature rise of laser diode and limits the output power, efficiency and modulation bandwidth due to increased loss and decreased differential gain. The main heat sources in laser diode during continuous wave operation are Joule heating and free carrier absorption loss. To control device self-heating, the epi structure needs to be designed with low electrical resistance and low absorption loss, while the heat flux must spread out of the device efficiently. This dissertation presents the control of self-heating of both edge emitting laser diodes and vertical cavity surface emitting lasers (VCSELs). For the 980nm high power edge …

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Particle Manipulation Via Optical Forces And Engineering Soft-Matter Systems With Tunable Nonlinearities., Shima Fardad Jan 2014

Particle Manipulation Via Optical Forces And Engineering Soft-Matter Systems With Tunable Nonlinearities., Shima Fardad

Electronic Theses and Dissertations

One of the most intriguing properties of light-matter interaction is the ability of an electromagnetic field to exert mechanical forces on polarizable objects. This phenomenon is a direct consequence of the fact that light carries momentum, which in turn can be transferred to matter. Mediated by scattering, this interaction usually manifests itself as a “pushing force” in the direction of beam propagation. However, it is possible to judiciously engineer these optical forces, either by tailoring particle polarizability, and/or by structuring the incident light field. As a simple example, a tightly focused laser beam demonstrates strong gradient forces, which may attract …

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Frequency Selective Detection Of Infrared Radiation In Uncooled Optical Nano-Antenna Array, Sushrut Modak Jan 2014

Frequency Selective Detection Of Infrared Radiation In Uncooled Optical Nano-Antenna Array, Sushrut Modak

Electronic Theses and Dissertations

Mid-infrared (mid-IR) detection and imaging over atmospheric transparent 3-5 μm and 8-12 μm bands are increasingly becoming important for various space, defense and civilian applications. Various kinds of microbolometers offer uncooled detection of IR radiation. However, broadband absorption of microbolometers makes them less sensitive to spectrally resolved detection of infrared radiation and the fabrication is also very tedious involving multiple complex lithography steps. In this study, we designed an optical nano-antenna array based detector with narrow frequency band of operation. The structure consists of a two-element antenna array comprised of a perforated metallic hole array coupled with an underneath disk …

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Nonlinear Integrated Photonics On Silicon And Gallium Arsenide Substrates, Jichi Ma Jan 2014

Nonlinear Integrated Photonics On Silicon And Gallium Arsenide Substrates, Jichi Ma

Electronic Theses and Dissertations

Silicon photonics is nowadays a mature technology and is on the verge of becoming a blossoming industry. Silicon photonics has also been pursued as a platform for integrated nonlinear optics based on Raman and Kerr effects. In recent years, more futuristic directions have been pursued by various groups. For instance, the realm of silicon photonics has been expanded beyond the well-established near-infrared wavelengths and into the mid-infrared (3 - 5 µm). In this wavelength range, the omnipresent hurdle of nonlinear silicon photonics in the telecommunication band, i.e., nonlinear losses due to two-photon absorption, is inherently nonexistent. With the lack of …

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Specialty Fiber Lasers And Novel Fiber Devices, Clemence Jollivet Jan 2014

Specialty Fiber Lasers And Novel Fiber Devices, Clemence Jollivet

Electronic Theses and Dissertations

At the Dawn of the 21st century, the field of specialty optical fibers experienced a scientific revolution with the introduction of the stack-and-draw technique, a multi-steps and advanced fiber fabrication method, which enabled the creation of well-controlled micro-structured designs. Since then, an extremely wide variety of finely tuned fiber structures have been demonstrated including novel materials and novel designs. As the complexity of the fiber design increased, highly-controlled fabrication processes became critical. To determine the ability of a novel fiber design to deliver light with properties tailored according to a specific application, several mode analysis techniques were reported, addressing the …

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Lp Fiber Mode Converters Using Holographic Phase Mask In Photo-Thermo-Refractive Glass, Aniket Patil Jan 2014

Lp Fiber Mode Converters Using Holographic Phase Mask In Photo-Thermo-Refractive Glass, Aniket Patil

Electronic Theses and Dissertations

In this study, an investigation was undertaken to research the use of holographic phase masks (HPMs) in photo-thermo-refractive (PTR) glass as mode converters for linearly polarized (LP) fiber modes. A Spatial Light Modulator (SLM) was used to generate higher-order transverse fiber modes LPm,n. Under proper incidence condition on the holographic device, LPm,n modes are diffracted and simultaneously converted into higher order or lower order LP modes. The process was analyzed by imaging the far field on a CCD camera. It is demonstrated that using this novel method of converting transverse fiber modes several combinations of LP modes can be converted …

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Advanced Liquid Crystal Materials For Display And Photonic Applications, Yuan Chen Jan 2014

Advanced Liquid Crystal Materials For Display And Photonic Applications, Yuan Chen

Electronic Theses and Dissertations

Thin-film-transistor (TFT) liquid crystal display (LCD) has been widely used in smartphones, pads, laptops, computer monitors, and large screen televisions, just to name a few. A great deal of effort has been delved into wide viewing angle, high resolution, low power consumption, and vivid color. However, relatively slow response time and low transmittance remain as technical challenges. To improve response time, several approaches have been developed, such as low viscosity liquid crystals, overdrive and undershoot voltage schemes, thin cell gap with a high birefringence liquid crystal, and elevated temperature operation. The state-of-the-art gray-to-gray response time of a nematic LC device …

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Generation And Characterization Of Sub-70 Isolated Attosecond Pulses, Qi Zhang Jan 2014

Generation And Characterization Of Sub-70 Isolated Attosecond Pulses, Qi Zhang

Electronic Theses and Dissertations

Dynamics occurring on microscopic scales, such as electronic motion inside atoms and molecules, are governed by quantum mechanics. However, the Schroedinger equation is usually too complicated to solve analytically for systems other than the hydrogen atom. Even for some simple atoms such as helium, it still takes months to do a full numerical analysis. Therefore, practical problems are often solved only after simplification. The results are then compared with the experimental outcome in both the spectral and temporal domain. For accurate experimental comparison, temporal resolution on the attosecond scale is required. This had not been achieved until the first demonstration …

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High Performance Three-Dimensional Display Based On Polymer-Stabilized Blue Phase Liquid Crystal, Yifan Liu Jan 2014

High Performance Three-Dimensional Display Based On Polymer-Stabilized Blue Phase Liquid Crystal, Yifan Liu

Electronic Theses and Dissertations

Autostereoscopic 2D/3D (two-dimension/three-dimension) switchable display has been attracting great interest in research and practical applications for several years. Among different autostereoscopic solutions, direction-multiplexed 3D displays based on microlens array or parallax barrier are viewed as the most promising candidates, due to their compatibility with conventional 2D display technologies. These 2D/3D switchable display system designs rely on fast switching display panels and photonics devices, including adaptive focus microlens array and switchable slit array. Polymer-stabilized blue phase liquid crystal (PS-BPLC) material provides a possible solution to meet the aforementioned fast response time requirement. However, present display and photonic devices based on blue …

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Holographic Recording And Applications Of Multiplexed Volume Bragg Gratings In Photo-Thermo-Refractive Glass, Daniel Ott Jan 2014

Holographic Recording And Applications Of Multiplexed Volume Bragg Gratings In Photo-Thermo-Refractive Glass, Daniel Ott

Electronic Theses and Dissertations

Recent developments in holographic recording of volume Bragg gratings (VBGs) in photo-thermo-refractive (PTR) glass have demonstrated their utility as components in high power laser systems for spectral narrowing, transverse mode control, beam combining, and pulse stretching/compression. VBG structures are capable of diffracting incident light into a single diffraction order with high efficiency given the Bragg condition is met. The Bragg condition depends on both the wavelength and angle of the incident light making VBGs useful for filtering and manipulating both the wavelength and angular spectrum of a source. This dissertation expands upon previous research in PTR VBGs by investigating multiplexed …

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Entangled Photon Pairs In Disordered Photonic Lattices, Lane Martin Jan 2014

Entangled Photon Pairs In Disordered Photonic Lattices, Lane Martin

Electronic Theses and Dissertations

Photonic lattices consisting of arrays of evanescently coupled waveguides fabricated with precisely controlled parameters have enabled the study of discrete optical phenomena, both classical and quantum, and the simulation of other physical phenomena governed by the same dynamics. In this dissertation, I have experimentally demonstrated transverse Anderson localization of classical light in arrays with off-diagonal coupling disorder and investigated theoretically and experimentally the propagation of entangled photon pairs through such disordered systems. I discovered a new phenomenon, Anderson co-localization, in which a spatially entangled photon pair in a correlated transversally extended state localizes in the correlation space, though neither photon …

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Translation Of 'Seasons Of Life: A Panoramic Selection Of Songs By Rabindranath Tagore', Monish Ranjan Chatterjee Jan 2014

Translation Of 'Seasons Of Life: A Panoramic Selection Of Songs By Rabindranath Tagore', Monish Ranjan Chatterjee

Electrical and Computer Engineering Faculty Publications

No abstract provided.

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Shielding Effectiveness (Se) Measurement For Maxair Waveguide Panel, Lossy Material Evaluation By Laptop Application, Xiao Li Jan 2014

Shielding Effectiveness (Se) Measurement For Maxair Waveguide Panel, Lossy Material Evaluation By Laptop Application, Xiao Li

Masters Theses

"The first part of the thesis presents the EM shielding effectiveness (SE) measurement of new kind of waveguide panel, MaxAir, which based on metal coating technology. SE Measurement tell the SE performance of MaxAir compared to the traditional metal waveguide panel. In terms of good features such as lower price, less weight, MaxAir could replace traditional waveguide panel in some applications by its SE results. There are two SE measurement methods are performed for MaxAir panel, both of them based on reverberation chamber. Measured SE for several MaxAir panel samples in different cell dimension and coating configuration. By the Measured …

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Cable Discharge Events (Cde) -- A Modeling And Simulation Perspective, Viswa Pilla Jan 2014

Cable Discharge Events (Cde) -- A Modeling And Simulation Perspective, Viswa Pilla

Masters Theses

"Cable discharge events (CDE) typically occur when a charged cable is connected to an electronic device. Several CDE damages in Ethernet LAN and USB communication interface equipment are reported by the IC manufacturers. CDE differs from other types of ESD such as human body model (HBM), charged device model (CDM) and IEC 61000-4-2 mainly due to faster rise times, longer pulse widths and higher peak currents. Various factors such as cable geometries, charging and discharging mechanisms, and load conditions influence CDE. Several researchers have developed some measurement techniques to understand CDE waveforms. However, there is little information regarding its modeling …

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A Complex-Envelope Fdtd Formulation Using Real-Valued Field-Variables, Qi Liu Jan 2014

A Complex-Envelope Fdtd Formulation Using Real-Valued Field-Variables, Qi Liu

Electronic Theses and Dissertations

Use of the complex-envelope (CE) representation of band-pass limited sources and their resulting fields increases the allowable time-step in finite-difference time-domain (FDTD) simulations. The complex envelope representation transforms band-pass limited fields and sources to complex-valued low-pass limited form and Maxwells equations from real-valued partial differential equations (PDEs) to complex-valued PDEs. Previous CE FDTD schemes have used complex valued difference equations in terms of complex valued field quantities to approximate these complex PDEs. This choice requires the use of complex numbers and complex operations in the computer program implementing the solution. An alternative CE FDTD scheme using only real numbers and …

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Multifunctional, Multimaterial Particle Fabrication Via An In-Fiber Fluid Instability, Joshua Kaufman Jan 2014

Multifunctional, Multimaterial Particle Fabrication Via An In-Fiber Fluid Instability, Joshua Kaufman

Electronic Theses and Dissertations

Spherical micro- and nano-particles have found widespread use in many various applications from paint to cosmetics to medicine. Due to the multiplicity of desired particle material(s), structure, size range, and functionality, many approaches exist for generating such particles. Bottom-up methods such as chemical synthesis have a high yield and work with a wide range of materials; however, these processes typically lead to large polydispersity and cannot produce structured particles. Top-down approaches such as microfluidics overcome the polydispersity issue and may produce a few different structures in particles, but at lower rates and only at the micro-scale. A method that can …

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3d Printed Spatially Variant Metamaterials, Cesar Roman Garcia Jan 2014

3d Printed Spatially Variant Metamaterials, Cesar Roman Garcia

Open Access Theses & Dissertations

The recent advancement in 3D printing has created a new way to design electronics and electromagnetic devices. This allows for a new breed of non-planar designs to be used, fully exploiting all three dimensions like never before. More functions can be fit into the same amount of space, products with novel form factors can be more easily manufactured, interconnects can be routed more smoothly, interfaces can be better implemented, electrical and mechanical functions can be comingled, and entirely new device paradigms will be invented. When departing from traditional planar topologies many new problems arise like signal integrity, crosstalk, noise, and …

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Digitally Manufactured Spatially Variant Photonic Crystals, Javier Jair Pazos Jan 2014

Digitally Manufactured Spatially Variant Photonic Crystals, Javier Jair Pazos

Open Access Theses & Dissertations

Metamaterials and photonic crystals are engineered composites that exhibit electromagnetic properties superior to those found in nature. They have been shown to produce novel and useful phenomena that allow extraordinary control over the electromagnetic field. One of these phenomena is self-collimation, an effect observed in photonic crystals in which a beam of light propagates without diffraction and is forced to flow in the direction of the crystal. Self-collimation however, like many of the mechanisms enabled through dispersion engineering, is effective in directions only along the principal axes of the lattice. To this effect, a general purpose synThesis procedure was developed …

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Photonic Filtering For Applications In Microwave Generation And Metrology, Marcus Bagnell Jan 2014

Photonic Filtering For Applications In Microwave Generation And Metrology, Marcus Bagnell

Electronic Theses and Dissertations

This work uses the photonic filtering properties of Fabry-Perot etalons to show improvements in the electrical signals created upon photodetection of the optical signal. First, a method of delay measurement is described which uses multi-heterodyne detection to find correlations in white light signals at 20 km of delay to sub millimeter resolution. By filtering incoming white light with a Fabry-Perot etalon, the pseudo periodic signal is suitable for measurement by combining and photodetecting it with an optical frequency comb. In this way, optical data from a large bandwidth can be downconverted and sampled on low frequency electronics. Second, a high …

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Parity-Time And Supersymmetry In Optics, Mohammad Ali Miri Jan 2014

Parity-Time And Supersymmetry In Optics, Mohammad Ali Miri

Electronic Theses and Dissertations

Symmetry plays a crucial role in exploring the laws of nature. By exploiting some of the underlying analogies between the mathematical formalism of quantum mechanics and that of electrodynamics, in this dissertation we show that optics can provide a fertile ground for studying, observing, and utilizing some of the peculiar symmetries that are currently out of reach in other areas of physics. In particular, in this work, we investigate two important classes of symmetries, parity-time symmetry (PT) and supersymmetry (SUSY), within the context of classical optics. The presence of PT symmetry can lead to entirely real spectra in non-Hermitian systems. …

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Reference Compensation For Localized Surface-Plasmon Resonance Sensors, Neha Nehru Jan 2014

Reference Compensation For Localized Surface-Plasmon Resonance Sensors, Neha Nehru

Theses and Dissertations--Electrical and Computer Engineering

Noble metal nanoparticles supporting localized surface plasmon resonances (LSPR) have been extensively investigated for label free detection of various biological and chemical interactions. When compared to other optical sensing techniques, LSPR sensors offer label-free detection of biomolecular interactions in localized sensing volume solutions. However, these sensors also suffer from a major disadvantage – LSPR sensors remain highly susceptible to interference because they respond to both solution refractive index change and non-specific binding as well as specific binding of the target analyte. These interactions can severely compromise the measurement of the target analyte in a complex unknown media and hence limit …

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Error Control And Efficient Memory Management For Sparse Integral Equation Solvers Based On Local-Global Solution Modes, Jun-Shik Choi Jan 2014

Error Control And Efficient Memory Management For Sparse Integral Equation Solvers Based On Local-Global Solution Modes, Jun-Shik Choi

Theses and Dissertations--Electrical and Computer Engineering

This dissertation presents and analyzes two new algorithms for sparse direct solution methods based on the use of local-global solution (LOGOS) modes. One of the new algorithms is a rigorous error control strategy for LOGOS-based matrix factorizations that utilize overlapped, localizing modes (OL-LOGOS) on a shifted grid. The use of OL-LOGOS modes is critical to obtaining asymptotically efficient factorizations from LOGOS-based methods. Unfortunately, the approach also introduces a non-orthogonal basis function structure. This can cause errors to accumulate across levels of a multilevel implementation, which has previously posed a barrier to rigorous error control for the OL-LOGOS factorization method. This …

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A Multi-Physics Computational Approach To Simulating Thz Photoconductive Antennas With Comparison To Measured Data And Fabrication Of Samples, Darren Ray Boyd Jan 2014

A Multi-Physics Computational Approach To Simulating Thz Photoconductive Antennas With Comparison To Measured Data And Fabrication Of Samples, Darren Ray Boyd

Theses and Dissertations--Electrical and Computer Engineering

The frequency demands of radiating systems are moving into the terahertz band with potential applications that include sensing, imaging, and extremely broadband communication. One commonly used method for generating and detecting terahertz waves is to excite a voltage-biased photoconductive antenna with an extremely short laser pulse. The pulsed laser generates charge carriers in a photoconductive substrate which are swept onto the metallic antenna traces to produce an electric current that radiates or detects a terahertz band signal. Therefore, analysis of a photoconductive antenna requires simultaneous solutions of both semiconductor physics equations (including drift-diffusion and continuity relations) and Maxwell’s equations. A …

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Visible-Light Photocatalyzed Cross-Linking Of Diacetylene Ligands By Quantum Dots To Improve Their Aqueous Colloidal Stability, Marion G. Götz, Hiroko Takeuchi, Matthew J. Goldfogel, Julia M. Warren, Brandon D. Fennel, Colin D. Heyes Jan 2014

Visible-Light Photocatalyzed Cross-Linking Of Diacetylene Ligands By Quantum Dots To Improve Their Aqueous Colloidal Stability, Marion G. Götz, Hiroko Takeuchi, Matthew J. Goldfogel, Julia M. Warren, Brandon D. Fennel, Colin D. Heyes

Chemistry & Biochemistry Faculty Publications and Presentations

Ligand cross-linking is known to improve the colloidal stability of nanoparticles, particularly in aqueous solutions. However, most cross-linking is performed chemically, in which it is difficult to limit interparticle cross-linking, unless performed at low concentrations. Photochemical cross-linking is a promising approach but usually requires ultraviolet (UV) light to initiate. Using such high-energy photons can be harmful to systems in which the ligand–nanoparticle bond is fairly weak, as is the case for the commonly used semiconductor quantum dots (QDs). Here, we introduce a novel approach to cross-link thiolated ligands on QDs by utilizing the photocatalytic activity of QDs upon absorbing visible …

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