Advanced Design Methodologies And Novel Applications Of Reflectarray Antennas,
2012
University of Mississippi
Advanced Design Methodologies And Novel Applications Of Reflectarray Antennas, Payam Nayeri
Electronic Theses and Dissertations
Reflectarray antennas combine the numerous advantages of printed antenna arrays and reflector antennas and create a hybrid high-gain antenna with a low-profile, low-mass, and diversified radiation performance. Reflectarrays are now emerging as the new generation of high-gain antennas for long-distance communications. In this dissertation, some advanced concepts demonstrating novel features of reflectarray antennas are presented. • First, various approaches for radiation analysis of reflectarray antennas are described and implemented. Numerical results are then presented for a variety of systems and the advantages, limitations, and accuracy of these approaches are discussed and compared with each other. • A broadband technique by …
Homogenization Of Structured Metasurfaces And Uniaxial Wire Medium Metamaterials For Microwave Applications,
2012
University of Mississippi
Homogenization Of Structured Metasurfaces And Uniaxial Wire Medium Metamaterials For Microwave Applications, Chandra Sekhar Reddy Kaipa
Electronic Theses and Dissertations
In recent years, the study of electromagnetic wave interaction with artificial media has been the subject of intense research interest due to their extraordinary properties such as negative refraction, partial focusing, enhanced transmission, and spatial filtering, among others. Artificial media are crystals of various periodic metallic inclusions with dimensions of the order of ?/10 - ?/4. When compared to natural materials, the inclusions are, thus, not as small in terms of the wavelength, even in the optical band. Therefore, one should expect the electrodynamics of these media to be inherently non-local, characterized by strong spatial dispersion effects. The dissertation includes …
Submillisecond-Response Blue Phase Liquid Crystals For Display Applications,
2012
University of Central Florida
Submillisecond-Response Blue Phase Liquid Crystals For Display Applications, Kuan Ming Chen
Electronic Theses and Dissertations
With exploding growth of information exchanges between people, display has become indispensable in our daily lives. After decades of intensive research and development in materials and devices, and massive investment in manufacturing technologies, liquid crystal display (LCD) has overcome various obstacles and achieved the performance we need, such as wide viewing angle, high contrast ratio, and high resolution, etc. These excellent performances make LCD prevailed in every perspective. Recently, with the demands of energy conservation, a greener LCD with lower power consumption is desired. In order to achieve this goal, new energy-effective driving methods, such as field sequential color display, …
Image Degradation Due To Surface Scattering In The Presence Of Aberrations,
2012
University of Central Florida
Image Degradation Due To Surface Scattering In The Presence Of Aberrations, Narak Choi
Electronic Theses and Dissertations
This dissertation focuses on the scattering phenomena by well-polished optical mirror surfaces. Specifically, predicting image degradation by surface scatter from rough mirror surfaces for a two-mirror telescope operating at extremely short wavelengths (9nm~30nm) is performed. To evaluate image quality, surface scatter is predicted from the surface metrology data and the point spread function in the presence of both surface scatter and aberrations is calculated. For predicting the scattering intensity distribution, both numerical and analytic methods are considered. Among the numerous analytic methods, the small perturbation method (classical Rayleigh-Rice surface scatter theory), the Kirchhoff approximation method (classical BeckmanKirchhoff surface scatter theory), …
Injection-Locked Semiconductor Lasers For Realization Of Novel Rf Photonics Components,
2012
University of Central Florida
Injection-Locked Semiconductor Lasers For Realization Of Novel Rf Photonics Components, Nazanin Hoghooghi
Electronic Theses and Dissertations
This dissertation details the work has been done on a novel resonant cavity linear interferometric modulator and a direct phase detector with channel filtering capability using injection-locked semiconductor lasers for applications in RF photonics. First, examples of optical systems whose performance can be greatly enhanced by using a linear intensity modulator are presented and existing linearized modulator designs are reviewed. The novel linear interferometric optical intensity modulator based on an injection-locked laser as an arcsine phase modulator is introduced and followed by numerical simulations of the phase and amplitude response of an injection-locked semiconductor laser. The numerical model is then …
Applications Of Volume Holographic Elements In High Power Fiber Lasers,
2012
University of Central Florida
Applications Of Volume Holographic Elements In High Power Fiber Lasers, Apurva Jain
Electronic Theses and Dissertations
The main objective of this thesis is to explore the use of volume holographic elements recorded in photo-thermo-refractive (PTR) glass for power scaling of narrow linewidth diffraction-limited fiber lasers to harness high average power and high brightness beams. Single fiber lasers enable kW level output powers limited by optical damage, thermal effects and non-linear effects. Output powers can be further scaled using large mode area fibers, however, at the cost of beam quality and instabilities due to the presence of higher order modes. The mechanisms limiting the performance of narrow-linewidth large mode area fiber lasers are investigated and solutions using …
Low Voltage Blue Phase Liquid Crystal Displays,
2012
University of Central Florida
Low Voltage Blue Phase Liquid Crystal Displays, Linghui Rao
Electronic Theses and Dissertations
From cell phones, laptops, desktops, TVs, to projectors, high reliability LCDs have become indispensable in our daily life. Tremendous progress in liquid crystal displays (LCDs) has been made after decades of extensive research and development in materials, device configurations and manufacturing technology. Nowadays, the most critical issue on viewing angle has been solved using multidomain structures and optical film compensation. Slow response time has been improved to 2-5 ms with low viscosity LC material, overdrive and undershoot voltage, and thin cell gap approach. Moving image blur has been significantly reduced by impulse driving and frame insertion. Contrast ratio in excess …
Lithographic Vertical-Cavity Surface-Emitting Lasers,
2012
University of Central Florida
Lithographic Vertical-Cavity Surface-Emitting Lasers, Guowei Zhao
Electronic Theses and Dissertations
Remarkable improvements in vertical-cavity surface-emitting lasers (VCSELs) have been made by the introduction of mode- and current-confining oxide optical aperture now used commercially. However, the oxide aperture blocks heat flow inside the device, causing a larger thermal resistance, and the internal strain caused by the oxide can degrade device reliability, also the diffusion process used for the oxide formation can limit device uniformity and scalability. Oxide-free lithographic VCSELs are introduced to overcome these device limitations, with both the mode and current confined within the lithographically defined intracavity mesa, scaling and mass production of small size device could be possible. The …
Vertical Field Switching Blue Phase Liquid Crystals For Field Sequential Color Displays,
2012
University of Central Florida
Vertical Field Switching Blue Phase Liquid Crystals For Field Sequential Color Displays, Hui-Chuan Cheng
Electronic Theses and Dissertations
Low power consumption is a critical requirement for all liquid crystal display (LCD) devices. A field sequential color (FSC) LCD was proposed by using red (R), green (G) and blue (B) LEDs and removing the lossy component of color filters which only transmits ~30% of the incoming white light. Without color filters, FSC LCDs exhibit a ~3X higher optical efficiency and 3X higher resolution density as compared to the conventional color filters-based LCDs. However, color breakup (CBU) is a most disturbing defect that degrades the image quality in FSC displays. CBU can be observed in stationary or moving images. It …
Optical Mode Pattern Study Of Gan Based Leds With And Without Nanoscale Top Grating,
2012
California Polytechnic State University - San Luis Obispo
Optical Mode Pattern Study Of Gan Based Leds With And Without Nanoscale Top Grating, Gregory Chavoor
Electrical Engineering
This study analyzes optical confinement factor and light emitting mode order for three different GaN LEDs: a conventional LED, thin Film LED, and thin Film LED with a photonic crystal (PhC) grating. For the first structure, we increase the thickness of AlxGa1-xN from 0 to 600nm, alter the x composition in AlxGa1-xN from 0.05 to 0.2 in steps of 0.05, and adjust the p-GaN and n-GaN thicknesses each from 0 to 200nm. For the second structure, we alter the n-GaN substrate thickness from 300-1000nm in steps of 100nm and 1000-4000nm in steps …
New Class Of Garnet Nanocomposites For Use In Magnetic Photonic Crystals Prepared By Rf Magnetron Co-Sputtering,
2012
Edith Cowan University
New Class Of Garnet Nanocomposites For Use In Magnetic Photonic Crystals Prepared By Rf Magnetron Co-Sputtering, Mohammad Nur-E-Alam, Mikhail Vasiliev, Kamal Alameh
ECU Presentations
No abstract provided.
Formulation And Solution Of Electromagnetic Integral Equations Using Constraint-Based Helmholtz Decompositions,
2012
University of Kentucky
Formulation And Solution Of Electromagnetic Integral Equations Using Constraint-Based Helmholtz Decompositions, Jin Cheng
Theses and Dissertations--Electrical and Computer Engineering
This dissertation develops surface integral equations using constraint-based Helmholtz decompositions for electromagnetic modeling. This new approach is applied to the electric field integral equation (EFIE), and it incorporates a Helmholtz decomposition (HD) of the current. For this reason, the new formulation is referred to as the EFIE-hd. The HD of the current is accomplished herein via appropriate surface integral constraints, and leads to a stable linear system. This strategy provides accurate solutions for the electric and magnetic fields at both high and low frequencies, it allows for the use of a locally corrected Nyström (LCN) discretization method for the resulting …
Optical Fluid-Based Photonic And Display Devices,
2012
University of Central Florida
Optical Fluid-Based Photonic And Display Devices, Su Xu
Electronic Theses and Dissertations
Conventional solid-state photonic devices exhibit an ultra-high optical performance and durability, but minimal adaptability. Recently, optical fluid-based photonic and display devices are emerging. By dynamically manipulating the optical interface formed by liquids, the optical output can be reconfigured or adaptively tuned in real time. Such devices exhibit some unique characteristics that are not achievable in conventional solid-state photonic devices. Therefore, they open a gateway for new applications, such as image and signal processing, optical communication, sensing, and lab-on-a-chip, etc. Different operation principles of optical fluidbased photonic devices have been proposed, for instance fluidic pressure, electrochemistry, thermal effect, environmentally adaptive hydrogel, …
Non-Reciprocal Wave Transmission In Integrated Waveguide Array Isolators,
2012
University of Central Florida
Non-Reciprocal Wave Transmission In Integrated Waveguide Array Isolators, Tony Yatming Ho
Electronic Theses and Dissertations
Non-reciprocal wave transmission is a phenomenon witnessed in certain photonic devices when the wave propagation dynamics through the device along one direction differs greatly from the dynamics along the counter-propagating direction. Specifically, it refers to significant power transfer occurring in one direction, and greatly reduced power transfer in the opposite direction. The resulting effect is to isolate the directionality of wave propagation, allowing transmission to occur along one direction only. Given the popularity of photonic integrated circuits (PIC), in which all the optical components are fabricated on the same chip so that the entire optical system can be made more …
Infrared Tapered Slot Antennas Coupled To Tunnel Diodes,
2012
University of Central Florida
Infrared Tapered Slot Antennas Coupled To Tunnel Diodes, Louis A. Florence
Electronic Theses and Dissertations
Tapered slot antennas (TSAs) have seen considerable application in the millimeter-wave portion of the spectrum. Desirable characteristics of TSAs include symmetric E- and H-plane antenna patterns, and broad non-resonant bandwidths. We investigate extension of TSA operation toward higher frequencies in the thermal infrared (IR), using a metal-oxide-metal diode as the detector. Several different infrared TSA design forms are fabricated using electronbeam lithography and specially developed thin-film processes. The angular antenna patterns of TSA-coupled diodes are measured at 10.6 micrometer wavelength in both E- and H-planes, and are compared to results of finite-element electromagnetic modeling using Ansoft HFSS. Parameter studies are …
High-Efficiency Blue Phase Liquid Crystal Displays,
2012
University of Central Florida
High-Efficiency Blue Phase Liquid Crystal Displays, Yan Li
Electronic Theses and Dissertations
Blue phase liquid crystals (BPLCs) have a delicate lattice structure existing between chiral nematic and isotropic phases, with a stable temperature range of about 2 K. But due to short coherent length, these self-assembled nano-structured BPLCs have a fast response time. In the past three decades, the application of BPLC has been rather limited because of its narrow temperature range. In 2002, Kikuchi et al. developed a polymer stabilization method to extend the blue-phase temperature range to more than 60 K. This opens a new gateway for display and photonic applications. In this dissertation, I investigate the material properties of …
Laser Filamentation Interaction With Materials For Spectroscopic Applications,
2012
University of Central Florida
Laser Filamentation Interaction With Materials For Spectroscopic Applications, Matthew Weidman
Electronic Theses and Dissertations
Laser filamentation is a non-diffracting propagation regime consisting of an intense core that is surrounded by an energy reservoir. For laser ablation based spectroscopy techniques such as Laser Induced Breakdown Spectroscopy (LIBS), laser filamentation enables the remote delivery of high power density laser radiation at long distances. This work shows a quasiconstant filament-induced mass ablation along a 35 m propagation distance. The mass ablated is sufficient for the application of laser filamentation as a sampling tool for plasma based spectroscopy techniques. Within the scope of this study, single-shot ablation was compared with multi-shot ablation. The dependence of ablated mass on …
Multi-Wavelength, Multi-Beam, Photonic Based Sensor For Object Discrimination And Positioning,
2012
Edith Cowan University
Multi-Wavelength, Multi-Beam, Photonic Based Sensor For Object Discrimination And Positioning, Kavitha Venkataraayan
Theses: Doctorates and Masters
Over the last decade, substantial research efforts have been dedicated towards the development of advanced laser scanning systems for discrimination in perimeter security, defence, agriculture, transportation, surveying and geosciences. Military forces, in particular, have already started employing laser scanning technologies for projectile guidance, surveillance, satellite and missile tracking; and target discrimination and recognition. However, laser scanning is relatively a new security technology. It has previously been utilized for a wide variety of civil and military applications. Terrestrial laser scanning has found new use as an active optical sensor for indoors and outdoors perimeter security. A laser scanning technique with moving …
Enhanced Refractometer Based On Periodically Tapered Small Core Singlemode Fiber,
2012
Technological University Dublin
Enhanced Refractometer Based On Periodically Tapered Small Core Singlemode Fiber, Pengfei Wang, Gilberto Brambilla, Ming Ding, Timothy Lee, Lin Bo, Yuliya Semenova, Qiang Wu, Gerald Farrell
Articles
Abstract—An all-fiber 1 refractive index (RI) sensor with a 2 simple configuration of periodical tapers is proposed and inves3 tigated experimentally. The proposed fiber RI sensor consists of 4 a small core fiber sandwiched between two standard singlemode 5 fibers, with tapers periodically fabricated along the small core 6 fiber using a focused CO2 laser beam. Such a structure can be 7 used for RI sensing by measuring the dip wavelength shift of 8 the multimode interference within the small core fiber cladding. 9 An average sensitivity of 226.6 nm/RIU (RI Unit) has been 10 experimentally achieved in the RI …
Surface And Guided Waves On Structured Surfaces,
2012
University of Texas at El Paso
Surface And Guided Waves On Structured Surfaces, Javier Polanco
Open Access Theses & Dissertations
Surface and guided waves on structured surfaces and inhomogeneous media studies the propagation of waves in systems with spatially varying parameters. In the rainbow case (chapter 1), the dielectric constant changes with coordinates. In the cylinder case: boundary and the metal (chapter 2), it is a curved surface. Finally, in the last case (chapter 3), the dielectric constant changes in z-direction.
