Electromagnetics and Photonics Commons^™

Broad Bandwidth Optical Frequency Combs From Low Noise, High Repetition Rate Semiconductor Mode-Locked Lasers, Anthony Klee

Electronic Theses and Dissertations

Mode-locked lasers have numerous applications in the areas of communications, spectroscopy, and frequency metrology. Harmonically mode-locked semiconductor lasers with external ring cavities offer a unique combination of benefits in that they can produce high repetition rate pulse trains with low timing jitter, achieve narrow axial mode linewidths, have the potential for entire monolithic integration on-chip, feature high wall-plug efficiency due to direct electrical pumping, and can be engineered to operate in different wavelength bands of interest. However, lasers based on InP/InGaAsP quantum well devices which operate in the important telecom C-band have thus far been relatively limited in bandwidth as …

Advanced Blue Phase Liquid Crystal Displays, Daming Xu

Electronic Theses and Dissertations

Thin-film transistor (TFT) liquid crystal displays (LCDs) have become indispensable in our daily lives. Their widespread applications range from smartphones, laptops, TVs to navigational devices, data projectors and wearable displays. Over past decades, massive efforts have been invested in device development, material characterization and manufacturing technology. As a result, the performance of LCDs, such as viewing angle, contrast ratio, color gamut and resolution, have been improved significantly. Nonetheless, there are still urgent needs for fast response time and low power consumption. Fast response time helps reduce motion image blurs and enable color sequential displays. The latter is particularly attractive since …

Multi-Purpose Device For Analyzing And Measuring Ultra-Short Pulses, Naman Anilkumar Mehta

Electronic Theses and Dissertations

Intensity auto correlator is device to measure pulse widths of ultrashort pulses on the order of picoseconds and femtoseconds. I have built an in-house, compact, portable, industry standard intensity auto correlator for measuring ultrashort pulse-widths. My device is suitable for pulse-widths from 500 ps to 50 fs. The impetus for developing this instrument stemmed from our development of a multicore-fiber laser for high power laser applications, which also produces very short pulses that cannot be measured with an oscilloscope. As techniques for measuring short pulse-widths have been well studied, what made my journey exciting was the process of taking an …

A 2x2 Polarization Switchable Patch Antenna Array For Polarization Modulation, Pengfei Ji

All Graduate Theses, Dissertations, and Other Capstone Projects

This thesis introduced and investigated a new concept in the development of a 2X2 polarization switchable patch antenna array for polarization modulation. Polarization modulation is a technique to modulate digital information using different polarization of the electromagnetic wave. The existing waveform based modulation techniques are well developed and start approaching to their performance limits. Polarization modulation provides a new modulation dimension for wireless communications and can further increase data throughput. A four-port circular patch antenna is presented and investigated for the implementation of polarization modulation. It has four ports, each excites radiation of a different polarization. A single pole four …

Application Of Embedded Frequency Selective Surfaces For Structural Health Monitoring, Dustin Franklin Pieper

Masters Theses

"This thesis proposes the use of Frequency Selective Surfaces (FSSs) as an embedded structural health monitoring (SHM) sensor. FSSs are periodic arrays of conductive elements that filter certain frequencies of incident electromagnetic radiation. The behavior of this filter is heavily dependent on the geometry of the FSS and local environment. Therefore, by monitoring how this filtering response changes when the geometric or environmental changes take place, information about those changes may be determined. In previous works, FSS-based sensing has shown promise for sensing normal strain (a stretching or compressing geometrical deformation). This concept is extended in this thesis by investigating …

Esd Related Soft Error Detection And Root Cause Analysis, Suyu Yang

Masters Theses

"In this article, several methods are outlined for detecting functional changes in an IC due to external interference such as ESD or EMI. The goal is to provide diagnostic tools for detection of potential soft failure susceptibilities of complex systems during the hardware design stage without the aid of any complex software. After the soft errors are found, circuit modeling techniques are used to characterize the DUT. By running the circuit model, the soft error threshold can be predicted and the circuit model can be used to evaluate the performance of other ESD protection methods. In the end several methods …

Study Jitter Amplification Of A Passive Channel And Investigation Of S₂₁ Magnitude Extraction Methodologies Using A Pattern Generator And Oscilloscope, Xinyun Guo

Masters Theses

"Recently the clock channel jitter amplification has been observed in several publications. Currently in many high-speed I/O systems, to avoid the cost and the complex clock recovery circuit design, people use traces forwarding clock signal from transmitting IC to receiving IC. When these clock traces are long enough, the amount of attenuation will induce not only inter-symbol-interference (ISI) but also modulate with the input jitter. Eventually it will lead some type of jitter been amplified after the channel. Similarly, the high speed communication channel (data channel) will also face this issue. Since there are no studies on the jitter amplification …

Intensity Control Of Dielectric Barrier Discharge Filaments, Matthew Crawford Paliwoda

Masters Theses

"When operated in a filamentary mode, a volume dielectric barrier discharge (DBD) is known to produce patterned plasma structures. These structures are currently being explored for reconfigurable metamaterial applications. In this work the presence and intensity of a single filament, within an array of filaments, was controlled by adjusting the voltage to that filament's individual needle electrode. The current, voltage, and time-averaged normalized light intensity were measured while varying the voltage of the needle through a self-biasing resistance. For a 7.5 kV, 3.2 kHz DBD in air, the needle-controlled filament intensity varies from that of the surrounding filaments to zero …

Mitigation Of Glass Weave Skew Using A Combination Of Low Dk Spread Glass, Multi-Ply Dielectric And Routing Direction, Kartheek Nalla

Masters Theses

"As the data rates increase into the multi-gigabit range, the bit periods fall in the range of few tens of picoseconds. At above few Gbps, it becomes very important to reduce skew between differential pairs as it can adversely impact the signal eye and thereby increase bit error rate. The goal of this study is to mitigate the skew contributed by woven glass fabric of PCB dielectrics.

The glass weave skew between differential pairs in a PCB occurs due to the difference in dielectric constants (DK) of glass and resin. This thesis aims to mitigate the skew by reducing the …

Nanosphere Lithography And Its Application In Rapid And Economic Fabrication Of Plasmonic Hydrogenated Amorphous Silicon Photovoltaic Devices, Chenlong Zhang

Dissertations, Master's Theses and Master's Reports

Solar photovoltaic (PV) devices harvest energy from solar radiation and convert it to electricity. PV technologies, as an alternative to traditional fossil fuels, use clean and renewable energy while minimizing pollution. For decades researchers have been developing thin film solar cells as an important alternatives to the relatively expensive bulk crystal solar cell technology. Among those, hydrogenated amorphous silicon (a-Si:H) solar cells prevails for good efficiency, non-toxic and materially abundant nature. However, a-Si:H thickness must be minimized to prevent light induced degradation, so optical enhancement is necessary. Light manipulation has to be applied and carefully engineered to trap light within …

Quasi-Magnetostatic Field Modeling Of Ships In The Presence Of Dynamic Sea Waves, Cody Lonsbury

Theses and Dissertations--Electrical and Computer Engineering

Mechanical stresses placed on ferromagnetic materials while under the influence of a magnetic field are known to cause changes to the permanent magnetization of the material. Modeling this phenomenon is vital to the safety of ocean faring ships. In this thesis, a quasi-strip theory method of computing the nonlinear wave induced motion of a ship is developed, and the fluid pressure on the surface of the hull is used to determine the mechanical stresses. An existing magnetostatic volume integral equation code is used to evaluate the effects of the ship motion and hull stresses. The resulting changes in the magnetic …

Dielectric Prism Antenna, Jose Antonio Avila

Open Access Theses & Dissertations

3D printing is revolutionizing the development and manufacturing of devices. Currently multi-material 3D printing, like metals plus dielectrics, is in the early stages and not very accessible. This work set out to develop an all-dielectric antenna that could be 3D printed with current widely accessible 3D printing technologies. The antenna developed is an all-dielectric ultra-thin antenna with a simple geometry. The antenna radiates by using total internal reflection and a circulating mode operating as a leaky whispering gallery mode. We are calling the antenna the dielectric prism antenna because it acts like an optical prism. The dielectric prism antenna was …

Towards The Scalability And Hybrid Parallelization Of A Spatially Variant Lattice Algorithm, Henry Roger Moncada Lopez

Open Access Theses & Dissertations

The purpose of this research is to design a faster implementation of the spatially variant algorithm that improves its performance when it is running on a parallel computer system.

The spatially variant algorithm is used to synthesize a spatially variant lattice for a periodic electromagnetic structure. The algorithm has the ability to spatially vary the unit cell orientation and exploit its directional dependencies. The algorithm produces a lattice that is smooth, continuous and free of defects. The lattice spacing remains strikingly uniform when the unit cell orientation, lattice spacing, fill fraction and more are spatially varied. This is important for …

Sensing Using Specialty Optical Fibers, Amy Van Newkirk

Electronic Theses and Dissertations

Fiber optic based sensing is a growing field with many applications in civil and aerospace engineering, oil and gas industries, and particularly in harsh environments where electronics are not able to function. Optical fibers can be easily integrated into structures, are immune to electromagnetic interference, can be interrogated from remote distances, and can be multiplexed for distributed measurements. Because of these properties, specialty fiber designs and devices are being explored for sensing temperature, strain, pressure, curvature, refractive index, and more. Here we show a detailed analysis of a multicore fiber (MCF) for sensing, including its design and optimization in simulation, …

Electrical Parasitic Bandwidth Limitations Of Oxide-Free Lithographic Vertical-Cavity Surface-Emitting Lasers, Xu Yang

Electronic Theses and Dissertations

Nowadays, Vertical-Cavity Surface-Emitting Lasers (VCSELs) are the most popular optical sources in short-reach data communications. In the commercial oxide VCSEL technology, an oxide aperture is created inside resonant cavity in realizing good mode and current confinement, however, high electrical resistance comes along with forming the oxide aperture and the electrical parasitic bandwidth becomes the main limitation in modulation speed. In this report, electrical bandwidths of oxide-free lithographic VCSELs have been studied along with their general lasing properties. Due to the new ways of fabricating the aperture, record low resistances have been achieved in oxide-free lithographic VCSELs with various sizes, while …

Experimental Performance Evaluation And Design Of Schemes For Passive Rfid Network, Shadi Ebrahimi-Asl

Doctoral Dissertations

"Passive Radio Frequency Identification (RFID) is a short range technology for transferring information. The main advantage of passive RFID systems over active communication systems is the battery-less operation at the client sides. However, there are two major challenges that limit the widespread adaptation of passive RFID systems: short communication range and low read rate in dense deployments. This dissertation addresses these issues by studying the root causes and develops solutions for them.

In this dissertation, understanding the backscattering behavior of antennas and also the mutual coupling interactions among them are found to be the root causes of the two above-mentioned …

Beyond Conventional C-Plane Gan-Based Light Emitting Diodes: A Systematic Exploration Of Leds On Semi-Polar Orientations, Morteza Monavarian

Theses and Dissertations

Despite enormous efforts and investments, the efficiency of InGaN-based green and yellow-green light emitters remains relatively low, and that limits progress in developing full color display, laser diodes, and bright light sources for general lighting. The low efficiency of light emitting devices in the green-to-yellow spectral range, also known as the “Green Gap”, is considered a global concern in the LED industry. The polar c-plane orientation of GaN, which is the mainstay in the LED industry, suffers from polarization-induced separation of electrons and hole wavefunctions (also known as the “quantum confined Stark effect”) and low indium incorporation efficiency that …

Optical Investigations Of Ingan Heterostructures And Gesn Nanocrystals For Photonic And Phononic Applications: Light Emitting Diodes And Phonon Cavities, Shopan D. Hafiz

Theses and Dissertations

InGaN heterostructures are at the core of blue light emitting diodes (LEDs) which are the basic building blocks for energy efficient and environment friendly modern white light generating sources. Through quantum confinement and electronic band structure tuning on the opposite end of the spectrum, Ge_1−xSn_x alloys have recently attracted significant interest due to its potential role as a silicon compatible infra-red (IR) optical material for photodetectors and LEDs owing to transition to direct bandgap with increasing Sn. This thesis is dedicated to establishing an understanding of the optical processes and carrier dynamics in InGaN heterostructures for achieving …

Spectrum Of Intracerebral Hemorrhage In Children: A Report From Picu Of A Resource Limited Country, Qalab Abbas, Qurat Ul Ain Merchant, Bushra Nasir, Anwar Ul Haque, Basit Salam, Gohar Javed

Department of Paediatrics and Child Health

Intracerebral hemorrhage (ICH) in children is a rare but disabling disease that accounts for almost half cases of stroke. We report our experience of ICH in children. Retrospective review of medical records of children (1 month-16 years) admitted in Pediatric Intensive Care Unit between January 2007 and December 2014 was done. Data collected included age, gender, presentation, examination findings, neuroimaging done (CT, MRI, and angiography) management (conservative/intervention), and outcome. Results are presented as frequency and percentages. Of the total 50 patients, 58% were male and 26% were <1 year. On presentation 44% had vomiting, 42% had seizures, and GCS < 8 while 40% had altered level of consciousness. Single bleed was present in 88%, 94% had supratentorial bleed, and 32% had intraventricular extension. 72% had bleed volume of <30 mL and 8% had >60 mL. CT scan was done in 98% patients and MRI in 34%, …

Small Size Coupling Feed And Inductive Shorting Antenna For Wide Bandwidth, Increased Gain And Efficiency With Low Specific Absorption Rate (Sar) Operation, Md Mahfuzur Rahman

Dissertations, Master's Theses and Master's Reports

Day by day technology is changing our lives rapidly. With these radical changes, demands in communication industry are also increasing drastically. To cope up with these demands, 2G, 3G, 4G, LTE (Long Term Evolution) communication systems have been introduced. Modern cellular phone should be capable to operate in wide range of frequency spectrum for their global access to provide end user customers these communication services. Hence mobile antennas should be designed in such a way that they should generate wideband operation. But commercially available standalone mobile antennas aren’t capable to operate in all those communication systems, several antennas are used …

Analysis On The Performance Limitations Of An Interferometric Geolocation Device, Michael Witt

Dissertations, Master's Theses and Master's Reports

GPS is a critical tool often used in terrestrial location and navigation. However, GPS relies on a system of satellites in medium earth orbit and is prone to dropouts at higher latitudes, and may be susceptible to spoofing or other attacks. Thus, it is prudent to examine possible alternatives. Recently, star tracking has been of interest in global positioning. There are many implementations of a star tracker using an imaging-based optical system to capture star locations in order to estimate position using celestial navigation techniques. These imaging systems are performance limited by blurring imposed by atmospheric turbulence, platform jitter, and …

Channel Modeling For Fifth Generation Cellular Networks And Wireless Sensor Networks, Amir Torabi

Dissertations, Master's Theses and Master's Reports

In view of exponential growth in data traffic demand, the wireless communications industry has aimed to increase the capacity of existing networks by 1000 times over the next 20 years. A combination of extreme cell densification, more bandwidth, and higher spectral efficiency is needed to support the data traffic requirements for fifth generation (5G) cellular communications. In this research, the potential improvements achieved by using three major 5G enabling technologies (i.e., small cells, millimeter-wave spectrum, and massive MIMO) in rural and urban environments are investigated. This work develops SPM and KA-based ray models to investigate the impact of geometrical parameters …

Sol-Gel Silica Coated Optical Fiber Sensor For Ammonia Gas Detection, Dejun Liu, Arun Mallik, Wei Han, Qiang Wu

Conference papers

A high sensitivity ammonia gas sensor based on a tapered small core single-mode fiber (SCSMF) structure for measurement of ammonia gas concentration is reported. The proposed tapered SCSMF fiber structure has a waist diameter of 13.5 μm and it is fabricated using a customized microheater brushing technique. The silica based material prepared by sol-gel method is used as a coating applied to the surface of tapered fiber structures. Experimental results show that sensor is very sensitive to ammonia. The best measurement resolution of the ammonia concentration is estimated to be 16 ppb for gas concentrations of 0.5 ppm to 2.5 …

Ellipsometric Characterization Of Silicon And Carbon Junctions For Advanced Electronics, Alexander G. Boosalis

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Ellipsometry has long been a valuable technique for the optical characterization of layered systems and thin films. While simple systems like epitaxial silicon dioxide are easily characterized, complex systems of silicon and carbon junctions have proven difficult to analyze. Traditional model dielectric functions for layered silicon homojunctions, a system with a similar structure to modern transistors, often have correlated parameters during ellipsometric data analysis. Similarly, epitaxial graphene as grown from thermal sublimation of silicon from silicon carbide or through chemical vapor deposition, tend to have model dielectric function parameters that correlate with the optical thickness of the graphene due to …

Scaled Synthetic Aperture Radar System Development, Ryan K. Green

Master's Theses

Synthetic Aperture Radar (SAR) systems generate two dimensional images of a target area using RF energy as opposed to light waves used by cameras. When cloud cover or other optical obstructions prevent camera imaging over a target area, SAR can be substituted to generate high resolution images. Linear frequency modulated signals are transmitted and received while a moving imaging platform traverses a target area to develop high resolution images through modern digital signal processing (DSP) techniques. The motivation for this joint thesis project is to design and construct a scaled SAR system to support Cal Poly radar projects. Objectives include …

Tungsten Disulphide Based All Fiber Q-Switching Cylindrical-Vector Beam Generation, J. Lin, K. Yan, Yong Zhou, L. X. Xu, C. Gu, Qiwen Zhan

Electro-Optics and Photonics Faculty Publications

We proposed and demonstrated an all fiber passively Q-switching laser to generate cylindrical-vectorbeam, a two dimensional material,tungsten disulphide (WS2), was adopted as a saturable absorber inside the laser cavity, while a few-mode fiber Bragg grating was used as a transverse mode-selective output coupler. The repetition rate of the Q-switching output pulses can be varied from 80 kHz to 120 kHz with a shortest duration of 958 ns. Attributed to the high damage threshold and polarization insensitivity of the WS2 based saturable absorber, the radially polarized beam and azimuthally polarized beam can be easily generated in the Q-switchingfiber laser.

A Study Of Direct Digital Manufactured Rf/Microwave Packaging, John W.I. Stratton

USF Tampa Graduate Theses and Dissertations

Various facets of direct digital manufactured (DDM) microwave packages are studied. The rippled surface inherent in fused deposition modeling (FDM) fabricated geometries is modeled in Ansoft HFSS, and its effect on the performance of microstrip transmission lines is assessed via simulation and measurement. The thermal response of DDM microstrip transmission lines is analyzed over a range of RF input powers, and linearity is confirmed over that range.

Two IC packages are embedded into DDM printed circuit boards, and their performance is analyzed. The first is a low power RF switch, and the second is an RF front end device that …

Skin Effect Suppression In Infrared-Laser Irradiated Planar Multi-Walled Carbon Nanotube/Cu Conductors, Kamran Keramatnejad, Yang Gao, Yunshen Zhou, Hossein Rabiee Glogir, Mengmeng Wang, Yongfeng Lu

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Skin effect suppression in planar multi-walled carbon nanotube (MWCNT)/Copper (Cu) conductors was realized at the 0-10 MHz frequency range through infrared laser irradiation of MWCNTs, which were coated on the surface of the Cu substrate via the electrophoretic deposition (EPD) method. The effect of laser irradiation and its power density on electrical and structural properties of the MWCNT/Cu conductors was investigated using a wavelength-tunable CO2 laser and then comparing the performance of the samples prepared at different conditions with that of pristine Cu. The irradiation at λ=9.219 μm proved to be effective in selective delivery of energy towards depths close …

Industry-University Collaboration: A University Of Dayton Model, Guru Subramanyam

Electrical and Computer Engineering Faculty Publications

This paper introduces industry-university collaboration activities currently in place at the University of Dayton's School of Engineering. These collaborations are important to prepare industry-ready graduates who excel in technical, entrepreneurial, and leadership skills. One of the key curricular components is the industry-sponsored multidisciplinary projects. Industry involvement in advisory committee, strategic research partnerships, and other forms are discussed.

Negative Index In A Lossy Chiral Metamaterial Under First-Order Material Dispersion Using A Drude Model, Tarig A. Algadey, Monish Ranjan Chatterjee

Electrical and Computer Engineering Faculty Publications

Using the Drude model for complex conductivity,phase and group velocities, and indices are calculated under first-order dispersion in chiral metamaterials. Conditions are derived for negative index, and the results compared with parametric analyses.