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Articles 211 - 240 of 824
Full-Text Articles in Electromagnetics and Photonics
Mid-Infrared Optical Sensing Using Sub-Wavelength Gratings, Brian Hogan, Liam Lewis, Michael Mcauliffe, Stephen P. Hegarty
Mid-Infrared Optical Sensing Using Sub-Wavelength Gratings, Brian Hogan, Liam Lewis, Michael Mcauliffe, Stephen P. Hegarty
Cappa Publications
Optical sensing has shown great potential for both quantitative and qualitative analysis of compounds. In particular sensors which are capable of detecting changes in refractive index at a surface as well as in bulk material have received much attention. Much of the recent research has focused on developing technologies that enable such sensors to be deployed in an integrated photonic device. In this work we demonstrate experimentally, using a sub-wavelength grating the detection of ethanol in aqueous solution by interrogating its large absorption band at 9.54 µm. Theoretical investigation of the operating principle of our grating sensor shows that in …
Theoretical Analysis Of A Volume Holographic Lens Using Matlab, Sanjay Keshri, Kevin Murphy, Izabela Naydenova, Suzanne Martin
Theoretical Analysis Of A Volume Holographic Lens Using Matlab, Sanjay Keshri, Kevin Murphy, Izabela Naydenova, Suzanne Martin
Conference Papers
Volume holographic lenses have great potential for different types of applications requiring light redirection and beam shaping such as solar light collection and LED light management. For lighting applications using LEDs, it is essential to make a highly efficient optical element to be placed in front of the LED in order to decrease energy losses. For that reason, a careful theoretical analysis of the properties and operation regime of the lens must be carried out at the design stage. The characteristics of focusing Holographic Optical Elements (HOE) depend on many factors including their thickness, spatial frequency, the angular range of …
Sensing Of Multiple Parameters With Whispering Gallery Mode Optical Fiber Micro-Resonators, Arun Kumar Mallik Dr, Vishnan Kavungal, Gerald Farrell, Yuliya Semenova
Sensing Of Multiple Parameters With Whispering Gallery Mode Optical Fiber Micro-Resonators, Arun Kumar Mallik Dr, Vishnan Kavungal, Gerald Farrell, Yuliya Semenova
Conference Papers
Monitoring of multiple physical parameters, such as humidity, temperature, strain, concentrations of certain chemicals or gases in various environments is of great importance in many industrial applications both for minimizing adverse effects on human health as well as for maintaining production levels and quality of products. In this paper we demonstrate two different approaches to the design of multi-parametric sensors using coupled whispering gallery mode (WGM) optical fiber micro-resonators. In the first approach, a small array of micro-resonators is coupled to a single fiber taper, while in the second approach each of the micro-resonators within an array is coupled to …
Fundamental Properties Of Metallic Nanolasers, William Hayenga
Fundamental Properties Of Metallic Nanolasers, William Hayenga
Electronic Theses and Dissertations
The last two decades have witnessed tremendous advancements in the area of nanophotonics and plasmonics, which has helped propel the development of integrated photonic sources. Of central importance to such circuits is compact, scalable, low threshold, and efficient coherent sources that can be driven at high modulation frequencies. In this regard, metallic nanolasers offer a unique platform. Their introduction has enabled confinement of light at a subwavelength scale and the ultra-small size of the modes afforded by these structures allows for cavity enhancing effects that can help facilitate thresholdless lasing and large direct modulation bandwidths. In this report, I present …
Processing Of Advanced Infrared Materials, Daniel Mcgill
Processing Of Advanced Infrared Materials, Daniel Mcgill
Electronic Theses and Dissertations
Infrared transparent glassy and crystalline materials often have unique and complex processing requirements but are an important class of materials for such applications as optical windows, lenses, waveplates, polarizers and beam splitters. This thesis investigates two specific materials, one amorphous and one crystalline, that are candidates for use in the short and midwave-infrared and mid and longwave infrared, respectively. It is demonstrated that an innovative uniaxial sintering process, which uses a sacrificial pressure-transmitting medium, can be used to fully densify a 70TeO2-20WO3-10La2O3 (TWL) glass powder. The characteristics of the sintered TWL glass is compared to that of a parent glass …
Active Recall Networks For Multiperspectivity Learning Through Shared Latent Space Optimization, Theus Aspiras, Ruixu Liu, Vijayan K. Asari
Active Recall Networks For Multiperspectivity Learning Through Shared Latent Space Optimization, Theus Aspiras, Ruixu Liu, Vijayan K. Asari
Electrical and Computer Engineering Faculty Publications
Given that there are numerous amounts of unlabeled data available for usage in training neural networks, it is desirable to implement a neural network architecture and training paradigm to maximize the ability of the latent space representation. Through multiple perspectives of the latent space using adversarial learning and autoencoding, data requirements can be reduced, which improves learning ability across domains. The entire goal of the proposed work is not to train exhaustively, but to train with multiperspectivity. We propose a new neural network architecture called Active Recall Network (ARN) for learning with less labels by optimizing the latent space. This …
Deep Temporal Convolutional Networks For Short-Term Traffic Flow Forecasting, Wentian Zhao, Yanyun Gao, Tingxiang Ji, Xili Wan, Feng Ye, Guangwei Bai
Deep Temporal Convolutional Networks For Short-Term Traffic Flow Forecasting, Wentian Zhao, Yanyun Gao, Tingxiang Ji, Xili Wan, Feng Ye, Guangwei Bai
Electrical and Computer Engineering Faculty Publications
To reduce the increasingly congestion in cities, it is essential for intelligent transportation system (ITS) to accurately forecast the short-term traffic flow to identify the potential congestion sites. In recent years, the emerging deep learning method has been introduced to design traffic flow predictors, such as recurrent neural network (RNN) and long short-term memory (LSTM), which has demonstrated its promising results. In this paper, different from existing work, we study the temporal convolutional network (TCN) and propose a deep learning framework based on TCN model for short-term city-wide traffic forecast to accurately capture the temporal and spatial evolution of traffic …
High Performance Liquid Crystal Devices For Augmented Reality And Virtual Reality, Md Javed Rouf Talukder
High Performance Liquid Crystal Devices For Augmented Reality And Virtual Reality, Md Javed Rouf Talukder
Electronic Theses and Dissertations
See-through augmented reality and virtual reality displays are emerging due to their widespread applications in education, engineering design, medical, retail, transportation, automotive, aerospace, gaming, and entertainment. For augmented reality and virtual reality displays, high-resolution density, high luminance, fast response time and high ambient contrast ratio are critically needed. High-resolution density helps eliminate the screen-door effect, high luminance and fast response time enable low duty ratio operation, which plays a key role for suppressing image blurs. A dimmer placed in front of AR display helps to control the incident background light, which in turn improves the image contrast. In this dissertation, …
Imaging Through Glass-Air Anderson Localizing Optical Fiber, Jian Zhao
Imaging Through Glass-Air Anderson Localizing Optical Fiber, Jian Zhao
Electronic Theses and Dissertations
The fiber-optic imaging system enables imaging deeply into hollow tissue tracts or organs of biological objects in a minimally invasive way, which are inaccessible to conventional microscopy. It is the key technology to visualize biological objects in biomedical research and clinical applications. The fiber-optic imaging system should be able to deliver a high-quality image to resolve the details of cell morphology in vivo and in real time with a miniaturized imaging unit. It also has to be insensitive to environmental perturbations, such as mechanical bending or temperature variations. Besides, both coherent and incoherent light sources should be compatible with the …
Novel Solid State Lasers Based On Volume Bragg Gratings, Evan Hale
Novel Solid State Lasers Based On Volume Bragg Gratings, Evan Hale
Electronic Theses and Dissertations
Since their invention in 1960, lasers have revolutionized modern technology, and tremendous amounts of innovation and development has gone into advancing their properties and efficiencies. This dissertation reports on further innovations by presenting novel solid state laser systems based on the volume Bragg gratings (VBGs) and the newly developed holographic phase mask (HPMs) for brightness enhancement, dual wavelength operation, and mode conversion. First, a new optical element was created by pairing the HPM with two surface gratings creating an achromatic holographic phase mask. This new optical device successfully performed transverse mode conversion of multiple narrow line laser sources operating from …
High-Dynamic-Range Foveated Near-Eye Display System, Guanjun Tan
High-Dynamic-Range Foveated Near-Eye Display System, Guanjun Tan
Electronic Theses and Dissertations
Wearable near-eye display has found widespread applications in education, gaming, entertainment, engineering, military training, and healthcare, just to name a few. However, the visual experience provided by current near-eye displays still falls short to what we can perceive in the real world. Three major challenges remain to be overcome: 1) limited dynamic range in display brightness and contrast, 2) inadequate angular resolution, and 3) vergence-accommodation conflict (VAC) issue. This dissertation is devoted to addressing these three critical issues from both display panel development and optical system design viewpoints. A high-dynamic-range (HDR) display requires both high peak brightness and excellent dark …
Modeling Land Subsidence Using Insar And Airborne Electromagnetic Data: Dataset, Ryan G. Smith, R. Knight
Modeling Land Subsidence Using Insar And Airborne Electromagnetic Data: Dataset, Ryan G. Smith, R. Knight
Research Data
Supporting dataset for article published in Water Resources Research, Volume 55, Issue 4, pages 2801-2819
Recurrent Residual U-Net For Medical Image Segmentation, Md Zahangir Alom, Christopher Yakopcic, Mahmudul Hasan, Tarek M. Taha, Vijayan K. Asari
Recurrent Residual U-Net For Medical Image Segmentation, Md Zahangir Alom, Christopher Yakopcic, Mahmudul Hasan, Tarek M. Taha, Vijayan K. Asari
Electrical and Computer Engineering Faculty Publications
Deep learning (DL)-based semantic segmentation methods have been providing state-of-the-art performance in the past few years. More specifically, these techniques have been successfully applied in medical image classification, segmentation, and detection tasks. One DL technique, U-Net, has become one of the most popular for these applications. We propose a recurrent U-Net model and a recurrent residual U-Net model, which are named RU-Net and R2U-Net, respectively. The proposed models utilize the power of U-Net, residual networks, and recurrent convolutional neural networks. There are several advantages to using these proposed architectures for segmentation tasks. First, a residual unit helps when training deep …
A Survey Of Techniques For Mobile Service Encrypted Traffic Classification Using Deep Learning, Pan Wang, Xuejiao Chen, Feng Ye, Zhixin Sun
A Survey Of Techniques For Mobile Service Encrypted Traffic Classification Using Deep Learning, Pan Wang, Xuejiao Chen, Feng Ye, Zhixin Sun
Electrical and Computer Engineering Faculty Publications
The rapid adoption of mobile devices has dramatically changed the access to various net- working services and led to the explosion of mobile service traffic. Mobile service traffic classification has been a crucial task that attracts strong interest in mobile network management and security as well as machine learning communities for past decades. However, with more and more adoptions of encryption over mobile services, it brings a lot of challenges about mobile traffic classification. Although classical machine learning approaches can solve many issues that port and payload-based methods cannot solve, it still has some limitations, such as time-consuming, costly handcrafted …
Mode Coupling In Space-Division Multiplexed Systems, Huiyuan Liu
Mode Coupling In Space-Division Multiplexed Systems, Huiyuan Liu
Electronic Theses and Dissertations
Even though fiber-optic communication systems have been engineered to nearly approach the Shannon capacity limit, they still cannot meet the exponentially-growing bandwidth demand of the Internet. Space-division multiplexing (SDM) has attracted considerable attention in recent years due to its potential to address this capacity crunch. In SDM, the transmission channels support more than one spatial mode, each of which can provide the same capacity as a single-mode fiber. To make SDM practical, crosstalk among modes must be effectively managed. This dissertation presents three techniques for crosstalk management for SDM. In some cases such as intra-datacenter interconnects, even though mode crosstalk …
Formulation And Implementation Of Iterative Method For Generating Spatially-Variant Lattices, Manuel Fernando Martinez
Formulation And Implementation Of Iterative Method For Generating Spatially-Variant Lattices, Manuel Fernando Martinez
Open Access Theses & Dissertations
The use of a matrix-free, memory-efficient approach to generate large-scale spatially variant lattices (SVL) was explored. A matrix-free iterative SVL generation algorithm was formulated and then implemented with a tremendous memory reduction observed. The algorithm consists of solving first-order central finite-differences along the entirety of the problem space point-by-point to obtain the grating phase function Φ(𝑠⃗) to which all desired spatially variant lattice properties are applied to. The algorithm was studied to identify key areas of data and task parallelism to exploit in heterogeneous computing systems consisting of clusters of central processing units (CPU) and graphics processing units (GPU) combinations. …
Broadband Mid-Infrared Frequency Combs Generated Via Frequency Division, Qitian Ru
Broadband Mid-Infrared Frequency Combs Generated Via Frequency Division, Qitian Ru
Electronic Theses and Dissertations
Frequency combs have revolutionized metrology and demonstrated numerous applications in science and technology. Combs operating in the mid-infrared region could be beneficial for molecular spectroscopy for several reasons. First, numerous molecules have their spectroscopic signatures in this region. Furthermore, the atmospheric window (3-5μm and 8-14μm) is located here. Additionally, a mid-infrared frequency comb could be employed as a diagnostic tool for the many components of human breath, as well as for detection of harmful gases and contaminants in the atmosphere. In this thesis, I used synchronously pumped subharmonic optical parametric oscillators (OPOs) operating at degeneracy to produce ultra-broadband outputs near …
Artificial Magnetism And Topological Phenomena In Optics, Midya Parto
Artificial Magnetism And Topological Phenomena In Optics, Midya Parto
Electronic Theses and Dissertations
Recent years have witnessed intense research activities to effectively control the flow of photons using various classes of optical structures such as photonic crystals and metamaterials. In this regard, optics has benefited from concepts in condensed matter and solid-state physics, where similar problems concerning electronic wavefunctions arise. An important example of such correspondence is associated with the photon dynamics under the effect of an artificial magnetic field. This is especially important since photons, as neutral bosons, do not inherently interact with magnetic fields. One way to mitigate this issue is to exploit magneto-optical materials. However, as is well known, using …
Non-Hermitian And Space-Time Mode Management, Nicholas Nye
Non-Hermitian And Space-Time Mode Management, Nicholas Nye
Electronic Theses and Dissertations
In the last few years, optics has witnessed the emergence of two fields namely metasurfaces and parity-time (PT) symmetry. Optical metasurfaces are engineered structures that provide unique responses to electromagnetic waves, absent in natural materials. On the other hand, PT symmetry has emerged from quantum mechanics, when a new class of non-Hermitian Hamiltonian quantum systems was shown to have real eigenvalues. In this work, we demonstrate how PT-symmetric diffractive structures are capable of eliminating diffraction orders in specific directions, while maintaining/enhancing the remaining orders. In the second part of this work, we emphasize on supersymmetry (SUSY) and its applications in …
Computational Imaging Systems For High-Speed, Adaptive Sensing Applications, Yangyang Sun
Computational Imaging Systems For High-Speed, Adaptive Sensing Applications, Yangyang Sun
Electronic Theses and Dissertations
Driven by the advances in signal processing and ubiquitous availability of high-speed low-cost computing resources over the past decade, computational imaging has seen the growing interest. Improvements on spatial, temporal, and spectral resolutions have been made with novel designs of imaging systems and optimization methods. However, there are two limitations in computational imaging. 1), Computational imaging requires full knowledge and representation of the imaging system called the forward model to reconstruct the object of interest. This limits the applications in the systems with a parameterized unknown forward model such as range imaging systems. 2), the regularization in the optimization process …
Cryogenic Performance Projections For Ultra-Small Oxide-Free Vertical-Cavity Surface-Emitting Lasers, Mina Bayat
Cryogenic Performance Projections For Ultra-Small Oxide-Free Vertical-Cavity Surface-Emitting Lasers, Mina Bayat
Electronic Theses and Dissertations
Small-sized vertical-cavity surface-emitting laser (VCSEL) may offer very low power consumption along with high reliability for cryogenic data transfer. Cryogenic data transfer has application in supercomputers and superconducting for efficient computing and also focal plane array cameras operating at 77 K, and at the lower temperature of 4 K for data extraction from superconducting circuits. A theoretical analysis is presented for 77 K and 4 K operation based on small cavity, oxide-free VCSEL sizes of 2 to 6 µm, that have been shown to operate efficiently at room temperature. Temperature dependent operation for optimally-designed VCSELs are studied by calculating the …
Design And Fabrication Of Scalable Multifunctional Multimaterial Fibers And Textiles, Felix Tan
Design And Fabrication Of Scalable Multifunctional Multimaterial Fibers And Textiles, Felix Tan
Electronic Theses and Dissertations
Multimaterial fibers eschew the traditional mono-material structures typical of traditional optical fibers for novel internal architectures that combine disparate materials with distinct optical, mechanical, and electronic properties, thereby enabling novel optoelectronic functionalities delivered in the form factor of an extended fiber. This new class of fibers developed over the past two decades is attracting interest from researchers in such different fields as optics, textiles, and biomedicine. The juxtaposition of multiple materials integrated at micro- and nanoscales in complex geometries while ensuring intimate smooth interfaces extending continuously for kilometers facilitates unique applications such as non-invasive laser surgery, self-monitoring fibers, e-textiles, and …
Stable, Highly Luminescent Perovskite-Polymer Composites For Photonics Applications, Juan He
Stable, Highly Luminescent Perovskite-Polymer Composites For Photonics Applications, Juan He
Electronic Theses and Dissertations
Metal halide perovskites (simplified as perovskites as below), particularly those in nanocrystal forms, have recently emerged as highly efficient, bandgap tunable photonics materials that can be easily solution processed at low cost for display, lighting or other energy conversion applications. However, the quick degradation of perovskite nanocrystals under external stresses or upon colloidal aggregations has been a major challenge for most applications where high reliability is normally required. In this thesis, we have explored a polymer swelling-deswelling microencapsulation (SDM) process that enables the dispersion, in-situ crystallization and subsequent surface passivation of perovskite nanocrystals in polymer matrices, and leads to ultrastable …
Computational Imaging With Limited Photon Budget, Zheyuan Zhu
Computational Imaging With Limited Photon Budget, Zheyuan Zhu
Electronic Theses and Dissertations
The capability of retrieving the image/signal of interest from extremely low photon flux is attractive in scientific, industrial, and medical imaging applications. Conventional imaging modalities and reconstruction algorithms rely on hundreds to thousands of photons per pixel (or per measurement) to ensure enough signal-to-noise (SNR) ratio for extracting the image/signal of interest. Unfortunately, the potential of radiation or photon damage prohibits high SNR measurements in dose-sensitive diagnosis scenarios. In addition, imaging systems utilizing inherently weak signals as contrast mechanism, such as X-ray scattering-based tomography, or attosecond pulse retrieval from the streaking trace, entail prolonged integration time to acquire hundreds of …
Optical Sensing Of Structural Dynamics In Complex Media, Jose Rafael Guzman Sepulveda
Optical Sensing Of Structural Dynamics In Complex Media, Jose Rafael Guzman Sepulveda
Electronic Theses and Dissertations
Quantifying the structural dynamics of complex media is challenging because of the multiple temporal and spatial scales involved. Thanks to the ability to retrieve collective dynamics noninvasively, light scattering-based approaches are often the methods of choice. This dissertation discusses specific features of dynamic light scattering that utilizes spatio-temporal coherence gating. It is demonstrated that this optical fiber-based approach can operate over a large range of optical regimes and it has a number of unique capabilities such as an effective isolation of single scattering, a large sensitivity, and a high collection efficiency. Moreover, the approach also provides means for proper ensemble …
Hybrid Integration Of Second- And Third-Order Highly Nonlinear Waveguides On Silicon Substrates, Guillermo Fernando Camacho Gonzalez
Hybrid Integration Of Second- And Third-Order Highly Nonlinear Waveguides On Silicon Substrates, Guillermo Fernando Camacho Gonzalez
Electronic Theses and Dissertations
In order to extend the capabilities and applications of silicon photonics, other materials and compatible technologies have been developed and integrated on silicon substrates. A particular class of integrable materials are those with high second- and third-order nonlinear optical properties. This work presents contributions made to nonlinear integrated photonics on silicon substrates, including chalcogenide waveguides for over an octave supercontinuum generation, and rib-loaded thin-film lithium niobate waveguides for highly efficient second-harmonic generation. Through the pursuit of hybrid integration of the two types of waveguides for applications such as on-chip self-referenced optical frequency combs, we have experimentally demonstrated fabrication integrability of …
Holographic Optical Elements For Visible Light Applications In Photo-Thermo-Refractive Glass, Fedor Kompan
Holographic Optical Elements For Visible Light Applications In Photo-Thermo-Refractive Glass, Fedor Kompan
Electronic Theses and Dissertations
This dissertation reports on design and fabrication of various optical elements in Photo-thermo-refractive (PTR) glass. An ability to produce complex holographic optical elements (HOEs) for the visible spectral region appears very beneficial for variety of applications, however, it is limited due to photosensitivity of the glass confined within the UV region. First two parts of this dissertation present two independent approaches to the problem of holographic recording using visible radiation. The first method involves modification of the original PTR glass rendering it photosensitive to radiation in the visible spectral region and, thus, making possible the recording of holograms in PTR …
Third-Order Optical Nonlinearities For Integrated Microwave Photonics Applications, Marcin Malinowski
Third-Order Optical Nonlinearities For Integrated Microwave Photonics Applications, Marcin Malinowski
Electronic Theses and Dissertations
The field of integrated photonics aims at compressing large and environmentally-sensitive optical systems to micron-sized circuits that can be mass-produced through existing semiconductor fabrication facilities. The integration of optical components on single chips is pivotal to the realization of miniature systems with high degree of complexity. Such novel photonic chips find abundant applications in optical communication, spectroscopy and signal processing. This work concentrates on harnessing nonlinear phenomena to this avail. The first part of this dissertation discusses, both from component and system level, the development of a frequency comb source with a semiconductor mode-locked laser at its heart. New nonlinear …
Compact -300 Kv Dc Inverted Insulator Photogun With Biased Anode And Alkali-Antimonide Photocathode, C. Hernandez-Garcia, P. Adderley, B. Bullard, J. Benesch, J. Grames, J. Gubeli, F. Hannon, J. Hansknecht, J. Jordan, R. Kazimi, G. A. Krafft, M. A. Mamun, M. Poelker, M. L. Stutzman, R. Suleiman, M. Tiefenback, Y. Wang, S. Zhang, H. Baumgart, G. Palacios-Serrano, S. Wijethunga, J. Yoskowitz, C. A. Valerio Lizarraga, R. Montoya Soto, A. Canales Ramos
Compact -300 Kv Dc Inverted Insulator Photogun With Biased Anode And Alkali-Antimonide Photocathode, C. Hernandez-Garcia, P. Adderley, B. Bullard, J. Benesch, J. Grames, J. Gubeli, F. Hannon, J. Hansknecht, J. Jordan, R. Kazimi, G. A. Krafft, M. A. Mamun, M. Poelker, M. L. Stutzman, R. Suleiman, M. Tiefenback, Y. Wang, S. Zhang, H. Baumgart, G. Palacios-Serrano, S. Wijethunga, J. Yoskowitz, C. A. Valerio Lizarraga, R. Montoya Soto, A. Canales Ramos
Electrical & Computer Engineering Faculty Publications
This contribution describes the latest milestones of a multiyear program to build and operate a compact −300 kV dc high voltage photogun with inverted insulator geometry and alkali-antimonide photocathodes. Photocathode thermal emittance measurements and quantum efficiency charge lifetime measurements at average current up to 4.5 mA are presented, as well as an innovative implementation of ion generation and tracking simulations to explain the benefits of a biased anode to repel beam line ions from the anode-cathode gap, to dramatically improve the operating lifetime of the photogun and eliminate the occurrence of micro-arc discharges.
Optical Micro-Seismometer Based On Evanescent Field Perturbation Of Whispering Gallery Modes, Jaime Da Silva
Optical Micro-Seismometer Based On Evanescent Field Perturbation Of Whispering Gallery Modes, Jaime Da Silva
Mechanical Engineering Research Theses and Dissertations
This thesis proposes a light-weight, compact, and accurate optical micro-seismometer that could be used in many applications, such as planetary exploration. The sensor proposed here is based on the principle of whispering gallery optical mode (WGM) resonance shifts of a dielectric micro-resonator due to disturbances of its evanescent field. The micro-seismometer could be used in place of the traditional bulky seismometers. The design of a waveguide-resonator and mechanical structure to disturb the evanescent field are presented. A proof-of-concept a seismometer model that uses a 5µm ring resonator is numerically tested with actual seismic data. The results show that a WGM-based …