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Articles 31 - 43 of 43

Full-Text Articles in Physics

Optically Isotropic Liquid Crystals For Display And Photonic Applications, Jin Yan Jan 2013

Optically Isotropic Liquid Crystals For Display And Photonic Applications, Jin Yan

Electronic Theses and Dissertations

For the past few decades, tremendous progress has been made on liquid crystal display (LCD) technologies in terms of stability, resolution, contrast ratio, and viewing angle. The remaining challenge is response time. The state-of-the-art response time of a nematic liquid crystal is a few milliseconds. Faster response time is desirable in order to reduce motion blur and to realize color sequential display using RGB LEDs, which triples the optical efficiency and resolution density. Polymer-stabilized blue phase liquid crystal (PS-BPLC) is a strong candidate for achieving fast response time because its self-assembled cubic structure greatly reduces the coherence length. The response …

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Inverse Problems In Multiple Light Scattering, John Broky Jan 2013

Inverse Problems In Multiple Light Scattering, John Broky

Electronic Theses and Dissertations

The interaction between coherent waves and material systems with complex optical properties is a complicated, deterministic process. Light that scatters from such media gives rise to random fields with intricate properties. It is common perception that the randomness of these complex fields is undesired and therefore is to be removed, usually through a process of ensemble averaging. However, random fields emerging from light matter interaction contain information about the properties of the medium and a thorough analysis of the scattered light allows solving specific inverse problems. Traditional attempts to solve these kinds of inverse problems tend to rely on statistical …

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Metrology Of Volume Chirped Bragg Gratings Recorded In Photo-Thermo-Refractive Glass For Ultrashort Pulse Stretching And Compressing, Christopher Lantigua Jan 2013

Metrology Of Volume Chirped Bragg Gratings Recorded In Photo-Thermo-Refractive Glass For Ultrashort Pulse Stretching And Compressing, Christopher Lantigua

Electronic Theses and Dissertations

Chirped Bragg gratings (CBGs) recorded in photo-thermo-refractive (PTR) glass provide a very efficient and robust way to stretch and compress ultra-short laser pulses. These gratings offer the ability to stretch pulses from hundreds of femtoseconds, to the order of 1 ns and then recompress them. However, in order to achieve pulse stretching of this magnitude, 100 mm thick CBGs are needed. Using these CBGs to both stretch, and re-compress the pulse thus requires propagation through 200 mm of optical glass. This therefore demands perfect control of the glass homogeneity, as well as the holographic recording process of the CBG. In …

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Mesoscale Light-Matter Interactions, Kyle Douglass Jan 2013

Mesoscale Light-Matter Interactions, Kyle Douglass

Electronic Theses and Dissertations

Mesoscale optical phenomena occur when light interacts with a number of different types of materials, such as biological and chemical systems and fabricated nanostructures. As a framework, mesoscale optics unifies the interpretations of the interaction of light with complex media when the outcome depends significantly upon the scale of the interaction. Most importantly, it guides the process of designing an optical sensing technique by focusing on the nature and amount of information that can be extracted from a measurement. Different aspects of mesoscale optics are addressed in this dissertation which led to the solution of a number of problems in …

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Implementation Of Branch-Point-Tolerant Wavefront Reconstructor For Strong Turbulence Compensation, Michael J. Steinbock Jun 2012

Implementation Of Branch-Point-Tolerant Wavefront Reconstructor For Strong Turbulence Compensation, Michael J. Steinbock

Theses and Dissertations

Branch points arise in optical transmissions due to strong atmospheric turbulence, long propagation paths, or a combination of both. Unfortunately, these conditions are very often present in desired operational scenarios for laser weapon systems, optical communication, and covert imaging, which suffer greatly when traditional adaptive optics systems either cannot sense branch points or implement non-optimal methods for sensing and correcting branch points. Previous research by Pellizzari presented a thorough analysis of various novel branch point tolerant reconstructors in the absence of noise. In this research a realistic model of the Air Force Institute of Technology's adaptive optics system is developed …

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Electromagnetic Propagation Anomalies In Waveguiding Structures And Scattering Systems, Alessandro Salandrino Jan 2011

Electromagnetic Propagation Anomalies In Waveguiding Structures And Scattering Systems, Alessandro Salandrino

Electronic Theses and Dissertations

The effects related to diffraction and interference are ubiquitous in phenomena involving electromagnetic wave propagation, and are accurately predicted and described within the framework of classical electrodynamics. In the vast majority of the cases the qualitative features of the evolution of a propagating wave can be inferred even without detailed calculations. A field distribution will spread upon propagation, will accumulate phase along the direction of power flow, will exert mechanical forces upon scattering objects in the direction of propagation etc. When such predictions fail, counterintuitive effects and new functionalities can be engineered. In this work a series of exceptional cases …

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Optical Wave Propagation In Discrete Waveguide Arrays, Jared Hudock Jan 2005

Optical Wave Propagation In Discrete Waveguide Arrays, Jared Hudock

Electronic Theses and Dissertations

The propagation dynamics of light in optical waveguide arrays is characteristic of that encountered in discrete systems. As a result, it is possible to engineer the diffraction properties of such structures, which leads to the ability to control the flow of light in ways that are impossible in continuous media. In this work, a detailed theoretical investigation of both linear and nonlinear optical wave propagation in one- and two-dimensional waveguide lattices is presented. The ability to completely overcome the effects of discrete diffraction through the mutual trapping of two orthogonally polarized coherent beams interacting in Kerr nonlinear arrays of birefringent …

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Polarimetric Characterization Of Random Electromagnetic Beams And Applications, Mircea Mujat Jan 2004

Polarimetric Characterization Of Random Electromagnetic Beams And Applications, Mircea Mujat

Electronic Theses and Dissertations

Polarimetry is one of the principal means of investigating the interaction of light with matter. Theoretical models and experimental techniques are presented in this dissertation for polarimetric characterization of random electromagnetic beams and of signatures of random media in different scattering regimes and configurations. The degree of polarization rather than the full description of the state of polarization is of interest in multiple scattering and free space propagation where the statistical nature and not the deterministic component of light bears the relevant information. A new interferometric technique for determining the degree of polarization by measuring the intensity fluctuations in a …

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Stable Spatial Solitons In Semiconductor Optical Amplifiers, Erdem Ultanir Jan 2004

Stable Spatial Solitons In Semiconductor Optical Amplifiers, Erdem Ultanir

Electronic Theses and Dissertations

A spatial soliton is a shape invariant self guided beam of light or a self induced waveguide. Spatial solitons appear as a result of the balance of diffraction and nonlinear focusing in a system. They have been observed in many different conservative media in the last couple of years. Solitons are ubiquitous, because of the probability of using their interactions in optical data processing, communications etc. Up to now due to the power required to generate the solitons, and the response times of the soliton supporting media, these special waves of nature could not penetrate the applications arena. Semiconductors, with …

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Chemical Structure - Nonlinear Optical Property Relationships For A Series Of Two-Photon Absorbing Fluorene Molecules, Joel Mccajah Hales Jan 2004

Chemical Structure - Nonlinear Optical Property Relationships For A Series Of Two-Photon Absorbing Fluorene Molecules, Joel Mccajah Hales

Electronic Theses and Dissertations

This dissertation reports on the investigation of two-photon absorption (2PA) in a series of fluorenyl molecules. Several current and emerging technologies exploit this optical nonlinearity including two-photon fluorescence imaging, three-dimensional microfabrication, site-specific photodynamic cancer therapy and biological caging studies. The two key features of this nonlinearity which make it an ideal candidate for the above applications are its quadratic dependence on the incident irradiance and the improved penetration into absorbing media that it affords. As a consequence of the burgeoning field which exploits 2PA, it is a goal to find materials that exhibit strong two-photon absorbing capabilities. Organic materials are …

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Evaluation Of The Photo-Induced Structural Mechanisms In Chalcogenide, Cedric Lopez Jan 2004

Evaluation Of The Photo-Induced Structural Mechanisms In Chalcogenide, Cedric Lopez

Electronic Theses and Dissertations

Chalcogenide glasses and their use in a wide range of optical, electronic and memory applications, has created a need for a more thorough understanding of material property variation as a function of composition and in geometries representative of actual devices. This study evaluates compositional dependencies and photo-induced structural mechanisms in As-S-Se chalcogenide glasses. An effective fabrication method for the reproducible processing of bulk chalcogenide materials has been demonstrated and an array of tools developed, for the systematic characterization of the resulting material's physical and optical properties. The influence of compositional variation on the physical properties of 13 glasses within the …

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Dispersion-Managed Breathing-Mode Semiconductor Mode-Locked Ring Laser, Bojan Resan Jan 2004

Dispersion-Managed Breathing-Mode Semiconductor Mode-Locked Ring Laser, Bojan Resan

Electronic Theses and Dissertations

A novel dispersion-managed breathing-mode semiconductor mode-locked ring laser is developed. The "breathing-mode" designation derives from the fact that intracavity pulses are alternately stretched and compressed as they circulate around the ring resonator. The pulses are stretched before entering the semiconductor gain medium to minimize the detrimental strong integrating self-phase modulation and to enable efficient pulse amplification. Subsequently compressed pulses facilitate bleaching the semiconductor saturable absorber. The intracavity pulse compression ratio is higher than 50. Down chirping when compared to up chirping allows broader mode-locked spectra and shorter pulse generation owing to temporal and spectral semiconductor gain dynamics. Pulses as short …

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Numerical Study Of Optical Delay In Semiconductor Multilayer Distributed Bragg Reflector And Tunable Microcavity Structures, Michael I. K. Etan Mar 2001

Numerical Study Of Optical Delay In Semiconductor Multilayer Distributed Bragg Reflector And Tunable Microcavity Structures, Michael I. K. Etan

Theses and Dissertations

The Air Force has a growing need for the greater bandwidth, speed, and flexibility offered by optical communication links. Future space systems and airborne platforms will most likely use optical signals for efficient power transmission and to minimize the possibility of spoofing and eavesdropping. Tunable optical delays play an important role in the implementation of free space optical communication links. The primary challenge in implementing these systems is the active maintenance of coherent wave fronts across the system's optical aperture. For space applications, this aperture may he hundreds of meters in diameter. Spatial segmentation of a large aperture into smaller …

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