Electromagnetics and Photonics Commons^™

Gratings In Optical Waveguides And Lasers, Weida Zhang

Electrical Engineering Theses and Dissertations

Gratings play a crucial role in Distributed Bragg reflector (DBR) lasers, influencing their performance and characteristics. The focus of this work is aimed at the design of DBR lasers that significantly impact the laser's spectral and temporal behavior, making it a key component in optimizing DBR laser functionality.

The SMU developed grating software, compared with commercially available photonics software, has improved accuracy and much smaller computation times. The improved accuracy and reduced computation times compared with commercial photonics software occur because commercial software is typically based on numerical methods such as finite-difference time-domain (FDTD), eigenmode expansion and beam propagation methods …

Multisensory System For Probing Scattering Media, Muralidhar Madabhushi Balaji

Electrical Engineering Theses and Dissertations

There are numerous problems in the physical sciences wherein the scattering of light fundamentally limits our ability to perceive and reason about objects within the visual field. Examples include navigation in foggy weather, detecting hidden contraband/explosives, detecting diseased regions in agricultural produce, and detecting tumors within tissue. In all these scenarios, the scrambling of light paths due to scattering reduces the ability to locate embedded objects and identify their spatial or spectral features.

Existing approaches address the challenge by augmenting optical sensing modalities with complementary techniques that do not rely on optical phenomenology, such as Magnetic Resonance Imaging (MRI) or …

Wireless Power Transfer Using Cavity With Height Discontinuities, Linsheng Zhang

Electrical Engineering Theses and Dissertations

A novel device for efficient wireless power transfer (WPT) system is presented. The proposed WPT system utilizes modified microstrip antennas with height discontinuities (MAHDs) to achieve power transfer. Similar to the conventional WPT system using inductive devices, the power transmission relies on the magnetic field coupling in the near field region. However, the researcher can treat the isolated transmitter or receiver as a modified microstrip antenna, which resembles a capacitive device. Like a capacitive antenna, we can utilize the cavity model, which significantly simplifies field analysis, design and impedance matching process, reduces the overall space requirement, and potentially increases the …

Series Aperture Coupled Fed Phased Array Antenna, Guang Yang

Electrical Engineering Theses and Dissertations

Phased arrays are employed in a wide range of civil and Military contexts, including RADAR, cellular communications, and satellite communications. However, modern phased-array antennas require complex design and bulky structure at high costs, hindering their implementation in many applications. The critical aspect of a phased array design lies in power splitting with a proper phase to each radiating element. Conventional power splitters such as quarter-wavelength or Wilkinson power splitters suffer problems associated with complex array network and high power dissipation. Furthermore, popular phase shifters such as MEMS switch, ferrite-based or PIN diode have drawbacks of low power-handling capability, expensive packaging, …

High Performance Scene Generator For Testing Of Imaging Sensors, Austin Modoff

Electrical Engineering Theses and Dissertations

Since the invention of modern solid-state imaging sensors in the 1980s, considerable advancements have been made, improving aspects such as frequency response, dynamic range, resolution, and wavelength diversity, as well as inventing many different types of sensor architectures such as framing sensors and event sensors. While considerable improvements in this field are evolving every day, the methods by which to test and validate these systems remain unchanged. Many of these test platforms require specialized designs to test only one or two specific qualities. For example, a spinning disk in front of a black body source to measure the frequency response …

Orbital Angular Momentum Orthogonality-Based Crosstalk Reduction: Theory And Experiment, Unaiza Tariq

Electrical Engineering Theses and Dissertations

Full duplex communication systems allow a single channel to be used for simultaneous two-way communication, increasing spectral efficiency. However, full duplex communication systems suffer from the issue of self-interference between local transmitter and receiver antennas. Analog subtraction and signal processing methods have previously been used to reduce this problem. This dissertation proposes the use of waves carrying orbital angular momentum (OAM) to mitigate the problem of self-interference by offering a means of additional isolation between local antennas.

Orbital angular momentum has been widely studied both in the photonics and radio domain. The theoretically infinite orthogonal states of an OAM signal …

Development And Application Of A Design Flow For Photonic Integrated Circuits, Ifeanyi Achu

Electrical Engineering Theses and Dissertations

Silicon photonics allows for the fabrication of many optical elements on a single photonic integrated circuit (PIC). By taking advantage of the established foundry technology used in the CMOS and silicon’s high refractive index, high feature density manufacturing can be achieved in mass quantities. In CMOS fabrication, from conception of an electronic circuit to testing, the process of designing an electronic circuit is dictated by a design flow which has been developed over the course of decades. This flow includes circuit level design and simulation, layout of the circuit, layout and verification of the chip, fabrication, packaging, and testing. Given …

Golightly : A Gpu Implementation Of The Finite-Difference Time-Domain Method, S. David Lively

Electrical Engineering Theses and Dissertations

Traditionally, optical circuit design is tested and validated using software which implement numerical modeling techniques such as Beam Propagation, Finite Element Analysis and the Finite-Difference Time-Domain (FDTD) method. FDTD simulations require significant computational power. Existing installations may distribute the computational requirements across large clusters of high-powered servers. This approach entails significant expense in terms of hardware, staffing and software support which may be prohibitive for some research facilities and private-sector engineering firms. The application of modern programmable GPUs to problems in scientific visualization and computation has facilitated faster development cycles for a variety of industry segments including large dataset visualization, …

Second-Order Enhanced Coupling Strength Grating Out-Couplers For A Monolithic Laser-Electro-Absorption Modulator, Maryam Dezfuli

Electrical Engineering Theses and Dissertations

Conventional grating out-couplers in III-V waveguides typically require lengths of several hundreds of microns to outcouple 50 to 90% of the incident optical power. Enhanced coupling strength (ECS) gratings, which reduce the out-coupler grating length to tens of microns, have a large relative permittivity difference between the materials on either side of the grating boundary along with a high index cover layer. With appropriately chosen permittivity and layer thicknesses, the addition of a cover layer “pulls” the peak of the optical mode towards the grating region, resulting in a significant increase in the grating confinement factor. The resulting ECS out-coupler …

On-Chip Nonreciprocal Components For Full-Duplex Communications And Gaussian Regulated Gate Driver For Electromagnetic Interference Reduction, Chang Yang

Electrical Engineering Theses and Dissertations

This dissertation is comprised of two unrelated design endeavors. The first one is about two CMOS nonreciprocal components: 1) an isolator and 2) a circulator. To make the components compact enough for the next generation communication systems with wide bandwidth, both components operate at 100 GHz band for full-duplex transceivers for ultra-high-data-rate millimeter-wave wireless communication. The proposed nonreciprocal structures are based on a time-domain modulation by signals at around 1/6 of the RF frequencies and spatial duplexing over the RF signal paths, demonstrating over 45 dB isolation in a bandwidth of 1.5 GHz over the tuning range of 85-110 GHz. …

Standing-Wave Dielectric Array Antennas, Ayman Althuwayb

Electrical Engineering Theses and Dissertations

Due to the evolutions in wireless communication systems, antenna engineers have been confronting a number of challenges regarding improving the performance of antennas, miniaturizing the size as well as considering the fabrication simplicity. Although dielectric resonator antennas typically suffer from exhibiting low gain, they have been thoroughly under investigating as they are being excellent candidates to be utilized to fulfill contemporary communication systems requirements and specifications, especially at high-frequency ranges. The reason behind this solicitude is because they have several advantageous features, including but not limited to the simplicity of the used excitation mechanism and fabrication easiness.

One of the …

Indirect Imaging Using Heterodyne Remote Digital Holography, Muralidhar Madabhushi Balaji

Electrical Engineering Theses and Dissertations

Conventional line-of-sight imaging techniques rely on detecting light paths bouncing from the object and reaching directly to the detector. Absence of any such direct light paths from object to detector results in a failure to recover any useful information using conventional techniques. The absence of direct light paths from object to detector can be observed in several real-world scenarios such as looking around a corner, imaging through turbid media, imaging through tissue etc.

The focus of this thesis is pertaining to the problem of looking around corners (or) imaging object hidden from line of sight at macroscopic scales. This thesis …

A Comparative Analysis Of Integrated Optical Waveguide Isolators With Magneto-Optic Layers, Reyhane Oztekin

Electrical Engineering Theses and Dissertations

The objective of this study is to theoretically devise an on-chip optical isolator which is monolithically integrated with a semiconductor waveguide layer yielding low loss. The optical properties of iron are modeled for the use of optical waveguide isolators by improving the Brendel-Bormann model. Our model for iron shows excellent fit with the optical data up to 30 electronvolts (eV). The semiconductor optical waveguide isolator with magneto-optic layers based on non-reciprocal loss shift is developed in this study. Fe, Co, and Ni metals as well as cerium-substituted yttrium iron garnet (Ce:YIG) have been used as magneto-optic layers. We have shown …

Circularly Polarized Two-Dimensional Microstrip Standing-Wave Array Antenna, Yang Fan

Electrical Engineering Theses and Dissertations

This dissertation reviews current designs of single-fed circularly polarized microstrip antennas and proposes a novel design concept with improved performance. The structure is similar to a regular microstrip patch antenna and the design procedure is relatively simple. By extending this SF scheme to an array structure based on the standing-wave array concept, a novel circular polarized array antenna can be realized by using one SF CP patch with standing-wave feeding networks. The standing-wave array antenna developed at SMU has a low-profile planar configuration and a simple feeding network structure and thus can be fabricated easily and cheaply with relatively high …

Spatial Division Multiplexing Using Ince-Gaussian Beams, Sahil Sakpal

Electrical Engineering Theses and Dissertations

In space division multiplexing (SDM) the spatial modes of a multimode optical fiber are used as individual data channels. SDM gives another degree of freedom over wavelength for increasing data transmission rates. As a result, SDM is a potential solution for more than 400Gbit/s requirements in data centers where scaling data transmission rates with parallel single mode optical fibers is currently ubiquitous. However, due to mode coupling, i.e., spatial modes exchange of power, SDM may require multiple inputs multiple output digital signal processing (MIMO-DSP) to mitigate resulting mode crosstalk, the cost and complexity of which may be prohibited in data …