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Electronic Theses and Dissertations

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Articles 271 - 292 of 292

Full-Text Articles in Electromagnetics and Photonics

Spectral Signature Modification By Application Of Infrared Frequency-Selective Surfaces, Brian Monacelli Jan 2005

Spectral Signature Modification By Application Of Infrared Frequency-Selective Surfaces, Brian Monacelli

Electronic Theses and Dissertations

It is desirable to modify the spectral signature of a surface, particularly in the infrared (IR) region of the electromagnetic spectrum. To alter the surface signature in the IR, two methods are investigated: thin film application and antenna array application. The former approach is a common and straightforward incorporation of optically-thin film coatings on the surface designated for signature modification. The latter technique requires the complex design of a periodic array of passive microantenna elements to cover the surface in order to modify its signature. This technology is known as frequency selective surface (FSS) technology and is established in the …

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Liquid Crystal Optics For Communications, Signal Processing And 3-D Microscopic Imaging, Sajjad Khan Jan 2005

Liquid Crystal Optics For Communications, Signal Processing And 3-D Microscopic Imaging, Sajjad Khan

Electronic Theses and Dissertations

This dissertation proposes, studies and experimentally demonstrates novel liquid crystal (LC) optics to solve challenging problems in RF and photonic signal processing, freespace and fiber optic communications and microscopic imaging. These include free-space optical scanners for military and optical wireless applications, variable fiber-optic attenuators for optical communications, photonic control techniques for phased array antennas and radar, and 3-D microscopic imaging. At the heart of the applications demonstrated in this thesis are LC devices that are non-pixelated and can be controlled either electrically or optically. Instead of the typical pixel-by-pixel control as is custom in LC devices, the phase profile across …

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Design And Assessment Of Compact Optical Systems Towards Special Effects Imaging, Vesselin Chaoulov Jan 2005

Design And Assessment Of Compact Optical Systems Towards Special Effects Imaging, Vesselin Chaoulov

Electronic Theses and Dissertations

A main challenge in the field of special effects is to create special effects in real time in a way that the user can preview the effect before taking the actual picture or movie sequence. There are many techniques currently used to create computer-simulated special effects, however current techniques in computer graphics do not provide the option for the creation of real-time texture synthesis. Thus, while computer graphics is a powerful tool in the field of special effects, it is neither portable nor does it provide work in real-time capabilities. Real-time special effects may, however, be created optically. Such approach …

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Tunable Liquid Crystal Photonic Devices, Yun-Hsing Fan Jan 2005

Tunable Liquid Crystal Photonic Devices, Yun-Hsing Fan

Electronic Theses and Dissertations

Liquid crystal (LC)-based adaptive optics are important for information processing, optical interconnections, photonics, integrated optics, and optical communications due to their tunable optical properties. In this dissertation, we describe novel liquid crystal photonic devices and their fabrication methods. The devices presented include inhomogeneous polymer-dispersed liquid crystal (PDLC), polymer network liquid crystals (PNLC) and phase-separated composite film (PSCOF). Liquid crystal/polymer composites could exist in different forms depending on the fabrication conditions. In Chap. 3, we demonstrate a novel nanoscale PDLC device that has inhomogeneous droplet size distribution. In such a PDLC, the inhomogeneous droplet size distribution is obtained by exposing the …

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System Design And Optimization Of Optical Coherence Tomography, Avni Ceyhun Akcay Jan 2005

System Design And Optimization Of Optical Coherence Tomography, Avni Ceyhun Akcay

Electronic Theses and Dissertations

Optical coherence imaging, including tomography (OCT) and microscopy (OCM), has been a growing research field in biomedical optical imaging in the last decade. In this imaging modality, a broadband light source, thus of short temporal coherence length, is used to perform imaging via interferometry. A challenge in optical coherence imaging, as in any imaging system towards biomedical diagnosis, is the quantification of image quality and optimization of the system components, both a primary focus of this research. We concentrated our efforts on the optimization of the imaging system from two main standpoints: axial point spread function (PSF) and practical steps …

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Interferometry-Based Free Space Communication And Information Processing, Muzamil Arshad Arain Jan 2005

Interferometry-Based Free Space Communication And Information Processing, Muzamil Arshad Arain

Electronic Theses and Dissertations

This dissertation studies, analyzes, and experimentally demonstrates the innovative use of interference phenomenon in the field of opto-electronic information processing and optical communications. A number of optical systems using interferometric techniques both in the optical and the electronic domains has been demonstrated in the filed of signal transmission and processing, optical metrology, defense, and physical sensors. Specifically it has been shown that the interference of waves in the form of holography can be exploited to realize a novel optical scanner called Code Multiplexed Optical Scanner (C-MOS). The C-MOS features large aperture, wide scan angles, 3-D beam control, no moving parts, …

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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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High Gain / Broadband Oxide Glasses For Next Generation Raman Amplifiers, Clara Rivero Jan 2005

High Gain / Broadband Oxide Glasses For Next Generation Raman Amplifiers, Clara Rivero

Electronic Theses and Dissertations

Interest in Raman amplification has undergone a revival due to the rapidly increasing bandwidth requirements for communications transmission, both for long haul and local area networks, and recent developments in the telecom fiber industry and diode laser technology. In contrast to rare earth doped fiber amplifiers, for which the range of wavelengths is fixed and limited, Raman gain bandwidths are larger and the operating wavelength is fixed only by the pump wavelength and the bandwidth of the Raman active medium. In this context, glasses are the material of choice for this application due to their relatively broad spectral response, and …

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Coherence Properties Of Optical Near-Fields, Adela Apostol Jan 2005

Coherence Properties Of Optical Near-Fields, Adela Apostol

Electronic Theses and Dissertations

Next generation photonics-based technologies will ultimately rely on novel materials and devices. For this purpose, phenomena at subwavelength scales are being studied to advance both fundamental knowledge and experimental capabilities. In this dissertation, concepts specific to near-field optics and experimental capabilities specific to near-field microscopy are used to investigate various aspects of the statistical properties of random electromagnetic fields in the vicinity of optically inhomogeneous media which emit or scatter radiation. The properties of such fields are being characterized within the frame of the coherence theory. While successful in describing the far-field properties of optical fields, the fundamental results of …

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Liquid Crystal Materials And Tunable Devices For Optical Communications, Fang Du Jan 2005

Liquid Crystal Materials And Tunable Devices For Optical Communications, Fang Du

Electronic Theses and Dissertations

In this dissertation, liquid crystal materials and devices are investigated in meeting the challenges for photonics and communications applications. The first part deals with polymer-stabilized liquid crystal (PSLC) materials and devices. Three polymer-stabilized liquid crystal systems are developed for optical communications. The second part reports the experimental investigation of a novel liquid-crystal-infiltrated photonic crystal fiber (PCF) and explores its applications in fiber-optic communications. The curing temperature is found to have significant effects on the PSLC performance. The electro-optic properties of nematic polymer network liquid crystal (PNLC) at different curing temperatures are investigated experimentally. At high curing temperature, a high contrast, …

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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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Selective Mode Excitation In Specialty Waveguides Using Micro Optical, Waleed Mohammed Jan 2004

Selective Mode Excitation In Specialty Waveguides Using Micro Optical, Waleed Mohammed

Electronic Theses and Dissertations

Although optical fibers and specialty waveguides are the base of majority of today's telecom and light delivery applications, fabrication deformation, nonlinearity and attenuation limit the bandwidth of the data being transmitted or the amount of power carried by these systems. One-way to overcome these limitations without changing the fibers design or fabrication is to engineer the input light in order to excite a certain mode or a group of modes with unique optical properties. Diffractive and micro optics are highly effective for selectively coupling light to specific modes. Using micro optics, mode selective coupling can be achieved through several matching …

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Discrete Nonlinear Wave Propagation In Kerr Nonlinear Media, Joachim Meier Jan 2004

Discrete Nonlinear Wave Propagation In Kerr Nonlinear Media, Joachim Meier

Electronic Theses and Dissertations

Discrete optical systems are a subgroup of periodic structures in which the evolution of a continuous electromagnetic field can be described by a discrete model. In this model, the total field is the sum of localized, discrete modes. Weakly coupled arrays of single mode channel waveguides have been known to fall into this class of systems since the late 1960's. Nonlinear discrete optics has received a considerable amount of interest in the last few years, triggered by the experimental realization of discrete solitons in a Kerr nonlinear AlGaAs waveguide array by H. Eisenberg and coworkers in 1998. In this work …

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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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Monolithic Integration Of Dual Optical Elements On High Power Semicond, Laurent Vaissie Jan 2004

Monolithic Integration Of Dual Optical Elements On High Power Semicond, Laurent Vaissie

Electronic Theses and Dissertations

This dissertation investigates the monolithic integration of dual optical elements on high power semiconductor lasers for emission around 980nm wavelength. In the proposed configuration, light is coupled out of the AlGaAs/GaAs waveguide by a low reflectivity grating coupler towards the substrate where a second monolithic optical element is integrated to improve the device performance or functionality. A fabrication process based on electron beam lithography and plasma etching was developed to control the grating coupler duty cycle and shape. The near-field intensity profile outcoupled by the grating is modeled using a combination of finite-difference time domain (FDTD) analysis of the nonuniform …

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Thermal Management, Beam Control,And Packaging Designs For High Power, Te-Yuan Chung Jan 2004

Thermal Management, Beam Control,And Packaging Designs For High Power, Te-Yuan Chung

Electronic Theses and Dissertations

Several novel techniques for controlling, managing and utilizing high power diode lasers are described. Low pressure water spray cooling for a high heat flux system is developed and proven to be an ideal cooling method for high power diode laser arrays. In order to enable better thermal and optical performance of diode laser arrays, a new and simple optical element, the beam control prism, is invented. It provides the ability to accomplish beam shaping and beam tilting at the same time. Several low thermal resistance diode packaging designs using beam control prisms are proposed, studied and produced. Two pump cavity …

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Multiple Scattering Of Light In Inhomogeneous Media And Applications, Claudia Mujat Jan 2004

Multiple Scattering Of Light In Inhomogeneous Media And Applications, Claudia Mujat

Electronic Theses and Dissertations

Light scattering-based techniques are being developed for non-invasive diagnostics of inhomogeneous media in various fields, such as medicine, biology, and material characterization. However, as most media of interest are highly scattering and have a complex structure, it is difficult to obtain a full analytical solution of the scattering problem without introducing approximations and assumptions about the properties of the system under consideration. Moreover, most of the previous studies deal with idealized scattering situations, rarely encountered in practice. This dissertation provides new analytical, numerical, and experimental solutions to describe subtle effects introduced by the properties of the light sources, and by …

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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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Quadratic Spatial Soliton Interactions, Ladislav Jankovic Jan 2004

Quadratic Spatial Soliton Interactions, Ladislav Jankovic

Electronic Theses and Dissertations

Quadratic spatial soliton interactions were investigated in this Dissertation. The first part deals with characterizing the principal features of multi-soliton generation and soliton self-reflection. The second deals with two beam processes leading to soliton interactions and collisions. These subjects were investigated both theoretically and experimentally. The experiments were performed by using potassium niobate (KNBO3) and periodically poled potassium titanyl phosphate (KTP) crystals. These particular crystals were desirable for these experiments because of their large nonlinear coefficients and, more importantly, because the experiments could be performed under non-critical-phase-matching (NCPM) conditions. The single soliton generation measurements, performed on KNBO3 by launching the …

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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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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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Towards Direct Writing Of 3-D Photonic Circuits Using Ultrafast Lasers, Arnaud Zoubir Jan 2004

Towards Direct Writing Of 3-D Photonic Circuits Using Ultrafast Lasers, Arnaud Zoubir

Electronic Theses and Dissertations

The advent of ultrafast lasers has enabled micromachining schemes that cannot be achieved by other current techniques. Laser direct writing has emerged as one of the possible routes for fabrication of optical waveguides in transparent materials. In this thesis, the advantages and limitations of this technique are explored. Two extended-cavity ultrafast lasers were built and characterized as the laser sources for this study, with improved performance over existing systems. Waveguides are fabricated in oxide glass, chalcogenide glass, and polymers, these being the three major classes of materials for the telecommunication industry. Standard waveguide metrology is performed on the fabricated waveguides, …

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