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Title: PREDICTING SURFACE SCATTER USING A LINEAR SYSTEMS FORMULATION OF NON-PARAXIAL SCALAR DIFFRACTION.
Creator: Krywonos, Andrey, Harvey, James, University of Central Florida
Abstract / Description: Scattering effects from rough surfaces are non-paraxial diffraction phenomena resulting from random phase variations in the reflected wavefront. The ability to predict these effects is important in a variety of applications including x-ray and EUV imaging, the design of stray light rejection systems, and reflection modeling for rendering realistic scenes and animations of physical objects in computer graphics. Rayleigh-Rice (small perturbation method) and Beckmann-Kirchoff (Kirchhoff...
Show moreScattering effects from rough surfaces are non-paraxial diffraction phenomena resulting from random phase variations in the reflected wavefront. The ability to predict these effects is important in a variety of applications including x-ray and EUV imaging, the design of stray light rejection systems, and reflection modeling for rendering realistic scenes and animations of physical objects in computer graphics. Rayleigh-Rice (small perturbation method) and Beckmann-Kirchoff (Kirchhoff approximation) theories are commonly used to predict surface scatter effects. In addition, Harvey and Shack developed a linear systems formulation of surface scatter phenomena in which the scattering behavior is characterized by a surface transfer function. This treatment provided insight and understanding not readily gleaned from the two previous theories, and has been incorporated into a variety of computer software packages (ASAP, Zemax, Tracepro). However, smooth surface and paraxial approximations have severely limited the range of applicability of each of the above theoretical treatments. In this dissertation, a linear systems formulation of non-paraxial scalar diffraction theory is first developed and then applied to sinusoidal phase gratings, resulting in diffraction efficiency predictions far more accurate than those provided by classical scalar theories. The application of the theory to these gratings was motivated by the fact that rough surfaces are frequently modeled as a superposition of sinusoidal surfaces of different amplitudes, periods, and orientations. The application of the non-paraxial scalar diffraction theory to surface scatter phenomena resulted first in a modified Beckmann-Kirchhoff surface scattering model, then a generalized Harvey-Shack theory, both of which produce accurate results for rougher surfaces than the Rayleigh-Rice theory and for larger incident and scattering angles than the classical Beckmann-Kirchhoff theory. These new developments enable the analysis and simplify the understanding of wide-angle scattering behavior from rough surfaces illuminated at large incident angles. In addition, they provide an improved BRDF (Bidirectional Reflectance Distribution Function) model, particularly for the smooth surface inverse scattering problem of determining surface power spectral density (PSD) curves from BRDF measurements.
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Date Issued: 2006
Identifier: CFE0001446, ucf:47055
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001446

Title: PROBING RANDOM MEDIA WITH SINGULAR WAVES.
Creator: Schwartz, Chaim, Dogariu, Aristide, University of Central Florida
Abstract / Description: In recent years a resurgence of interest in wave singularities (of which optical vortices are a prominent example), light angular momentum and the relations between them has occurred. Many applications in various areas of linear and non-linear optics have been based on studying effects related to angular momentum and optical vortices. This dissertation examines the use of such wave singularities for studying the light propagation in highly inhomogeneous media and the relationship to angular...
Show moreIn recent years a resurgence of interest in wave singularities (of which optical vortices are a prominent example), light angular momentum and the relations between them has occurred. Many applications in various areas of linear and non-linear optics have been based on studying effects related to angular momentum and optical vortices. This dissertation examines the use of such wave singularities for studying the light propagation in highly inhomogeneous media and the relationship to angular momentum transfer. Angular momentum carried by light can be, in many cases, divided in two terms. The… first one relates to the polarization of light and can be associated, in the quantum description, to the spin of a photon. The second is determined by the electromagnetic …field distribution and, in analogy to atomic physics, is associated with the orbital angular momentum (OAM) of a photon. Under the paraxial approximation appropriate for the case of beam propagation, the two terms do not couple. However, each of them can be modified by the interaction with different media in which the light propagates through processes which involve angular momentum exchange. The decoupling of spin and orbital parts of light angular momentum can not, in general, be assumed for non paraxial propagation in turbid media, especially when backscattering is concerned. In Chapter 3 of this dissertation, scattering effects on angular momentum of light are discussed both for the single and multiple scattering processes. It is demonstrated for the first time that scattering from a spherically symmetric scattering potential, couples the spin and the OAM such that the total angular momentum ‡flux density in conserved in every direction. Remarkably, the conservation of angular momentum occurs also for some classes of multiple scattering trajectories and this phenomenon manifests itself in ubiquitous polarization patterns observed in back-scattering from turbid media. It is newly shown in this dissertation that the polarization patterns a result of OAM carrying optical vortices which have a geometrical origin. These geometrical phase vortices are analyzed using the helicity space approach for optical geometrical phase (Berry phase). This approach, introduced in the con- text of random media, elucidates several aspects specific to propagation in helicity preserving and non-preserving scattering trajectories. Another aspect of singular waves interaction with turbid media relates to singularities embedded in the incident waves. Chapter 4 of the dissertation discusses how the phase distribution associated with an optical vortex leads to changes in the spatial correlations of the electromagnetic field. This change can be used to control the properties of the effect of enhanced backscattering in a way which allows inferring the optical properties of the medium. A detailed theoretical and experimental study of this effect is presented here for the first time for both double-pass geometries and diffusive media. It is also demonstrated that this novel experimental technique can be used to determine the optical properties of turbid media and, moreover, it permits to sense the depth of reflective inclusions in opaque media. When considering a regime of weakly inhomogeneous media, the paraxial approximation is still valid and therefore the spin and OAM do not couple. If, In addition, the medium is optically isotropic then the polarization is not affected. However, when the medium is non-axially symmetric for any specific realization, the OAM does change as a result of interaction with the medium. This effect can be studied using a newly developed method of coherent modes coupling which is presented in Chapter 5. This approach allows studying the power spread across propagating modes which carry different orbital angular momentum. The powerful concept of coherent modes coupling can be applied to fully coherent, fully polarized sources as well to partially coherent, partially polarized ones. An example of this scattering regime is atmospheric turbulence and the propagation through turbulence is thoroughly examined in Chapter 5. The results included in this dissertation are of fundamental relevance for a variety of applications which involves probing different types of random media. Such applications include remote sensing in atmospheric and maritime environments, optical techniques for biomedical diagnostics, optical characterization procedures in material sciences and others.
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Date Issued: 2006
Identifier: CFE0001174, ucf:46852
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001174

Title: Design of a hydrogen-filled hollow-core Raman fiber laser.
Creator: Qin, Yangyang, Amezcua Correa, Rodrigo, Schulzgen, Axel, Shah, Lawrence, University of Central Florida
Abstract / Description: The purpose of this study is to investigate the design of a Raman fiber laser based on a molecule hydrogen-filled hollow-core fiber with non-touching single ring of capillaries structure. O-hydrogen vibrational frequency shift of 4155 cm-1 and rotational frequency shift of 587 cm-1 were employed to generate Raman scattering from a 1064nm pump source.A thorough exploration was made to show how all Raman fiber laser components made up: gas chamber, hollow-core fibers, windows. The whole process...
Show moreThe purpose of this study is to investigate the design of a Raman fiber laser based on a molecule hydrogen-filled hollow-core fiber with non-touching single ring of capillaries structure. O-hydrogen vibrational frequency shift of 4155 cm-1 and rotational frequency shift of 587 cm-1 were employed to generate Raman scattering from a 1064nm pump source.A thorough exploration was made to show how all Raman fiber laser components made up: gas chamber, hollow-core fibers, windows. The whole process of chamber design, modification and fabrication were demonstrated. Besides, two kinds of anti-resonant hollow-core fibers were studied and tested. The transmission and loss spectrum of these fibers were measured thus it's easier to make a choice. Through the whole thesis a Raman fiber laser can be set up and tested very soon.
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Date Issued: 2017
Identifier: CFE0006645, ucf:51213
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006645

Title: Random Transformations of Optical Fields and Applications.
Creator: Kohlgraf-Owens, Thomas, Dogariu, Aristide, Saleh, Bahaa, Schulzgen, Axel, Tamasan, Alexandru, University of Central Florida
Abstract / Description: The interaction of optical waves with material systems often results in complex, seemingly random fields. In many cases, the interaction, while complicated, is both linear and deterministic.This dissertation focuses on the possible inverse problems associated with the determination of either the excitation field or the scattering system. The scattered field can be thought of as a massive sampling and mixing of the excitation field. This dissertation will show how such complicated sampling...
Show moreThe interaction of optical waves with material systems often results in complex, seemingly random fields. In many cases, the interaction, while complicated, is both linear and deterministic.This dissertation focuses on the possible inverse problems associated with the determination of either the excitation field or the scattering system. The scattered field can be thought of as a massive sampling and mixing of the excitation field. This dissertation will show how such complicated sampling functions can be characterized and how the corresponding scattering medium can then be used as an optical device such as a lens, polarimeter, or spectrometer.Another class of inverse problems deals with extracting information about the material system from changes in the scattered field. This dissertation includes a novel technique, based on dynamic light scattering, that allows for a full polarimetric measurement of the scattered light using a reference field with controllable polarization. Another technique relates to imaging the reflectivity of a target that is being randomly illuminated. We demonstrate that a method based on the correlation between the integrated scattered intensity and the corresponding illumination intensity distribution can prove superior to standard imaging microscopy at low-light levels.
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Date Issued: 2012
Identifier: CFE0004786, ucf:49746
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004786

Title: Inverse Problems in Multiple Light Scattering.
Creator: Broky, John, Dogariu, Aristide, Christodoulides, Demetrios, Wu, Shintson, Tamasan, Alexandru, University of Central Florida
Abstract / Description: 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...
Show moreThe 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 average quantities and ignore the deterministic interaction between the optical field and the scattering structure. Thus, because ensemble averaging inherently destroys specific characteristics of random processes, one can only recover limited information about the medium. This dissertation discusses practical means that go beyond ensemble averaging to probe complex media and extract additional information about a random scattering system. The dissertation discusses cases in which media with similar average properties can be differentiated by detailed examination of fluctuations between different realizations of the random process of multiple scattering. As a different approach to this type of inverse problems, the dissertation also includes a description of how higher-order field and polarization correlations can be used to extract features of random media and complex systems from one single realization of the light-matter interaction. Examples include (i) determining the level of multiple scattering, (ii) identifying non-stationarities in random fields, and (iii) extracting underlying correlation lengths of random electromagnetic fields that result from basic interferences. The new approaches introduced and the demonstrations described in this dissertation represent practical means to extract important material properties or to discriminate between media with similar characteristics even in situations when experimental constraints limit the number of realizations of the complex light-matter interaction.
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Date Issued: 2012
Identifier: CFE0004656, ucf:49888
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004656

Title: GOLD NANOPARTICLES: SYNTHESIS, PROPERTY STUDY AND APPLCICATIONS FORBIOMOLECULAR DETECTION AND PHOTOTHERMAL THERAPY.
Creator: liu, xiong, Huo, Qun, University of Central Florida
Abstract / Description: This dissertation presents a systematic study on gold nanoparticles: from their chemical synthesis, modification of surface functionalities, optical properties studies with emphasis on the absorption and scattering properties, to applications of gold nanoparticles in biomolecular detection, imaging and photothermal therapy. In chapter 2, we studied the kinetics of gold nanoparticle growth under Brust-Shiffrin reaction conditions. In chapter 3, we further examined the reaction mechanism and...
Show moreThis dissertation presents a systematic study on gold nanoparticles: from their chemical synthesis, modification of surface functionalities, optical properties studies with emphasis on the absorption and scattering properties, to applications of gold nanoparticles in biomolecular detection, imaging and photothermal therapy. In chapter 2, we studied the kinetics of gold nanoparticle growth under Brust-Shiffrin reaction conditions. In chapter 3, we further examined the reaction mechanism and growth kinetics of gold nanoparticles using oleylamine as both a reducing reagent and particle growth passivation ligand. From these two projects, important understanding was revealed on gold nanoparticle formation and growth mechanism. Chapter 4 describes the synthesis of a monofunctional gold nanoparticle through a solid phase place exchange reaction. From Chapter 5, we moved to the optical property study of gold nanoparticles, particularly the absorption and scattering phenomenon. In this work a systematic analysis on the extinction coefficient of gold nanoparticles was performed, providing meaningful references for applications based on optical absorption properties of gold nanoparticles. In Chapter 6 and Chapter 7, we developed a one-step homogeneous immunoassay for protein detection and analysis based on the strong light scattering of gold nanoparticles and dynamic light scattering detection technique. In Chapter 8, we further improved the stability of gold nanoparticle bioconjugates using a poly(ethylene glycol)-coated gold nanoparticles and further tested this nanoparticle in the one-step homogeneous immunoassay. Finally in Chapter 9, we demonstrated the application of gold nanoparticles for in vitro bioimaging and photothermal therapy of a lung cancer cell. In summary, this dissertation presents a comprehensive study on the synthesis, surface modification, property study of gold nanoparticles and their applications in biomolecular imaging and analysis.
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Date Issued: 2009
Identifier: CFE0002874, ucf:48020
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002874

Title: PHYSICAL PROPERTIES OF WAVE SCATTERING BY CHIRAL PERIODIC STRUCTURE.
Creator: Yang, Xiaomin, Wu, Xinzhang, University of Central Florida
Abstract / Description: Attention has been focused on electromagnetic chirality and its potential applications to microwave, millimeter wave and optical wave devices. In this work, wave propagation through a chiral periodic structure with arbitrary shape is investigated. Although perturbation theory and coupled-mode theory have been used to analyze chiral periodic structure, those are approximate methods and can only be used for low frequency applications. In this work, the rigorous mode-matching method is used to...
Show moreAttention has been focused on electromagnetic chirality and its potential applications to microwave, millimeter wave and optical wave devices. In this work, wave propagation through a chiral periodic structure with arbitrary shape is investigated. Although perturbation theory and coupled-mode theory have been used to analyze chiral periodic structure, those are approximate methods and can only be used for low frequency applications. In this work, the rigorous mode-matching method is used to solve the problem. Staircase approximation is introduced to change the curved structure to a multilayer structure. The field solutions in the uniform air regions and unbounded air-chiral periodic array have been derived. Finite element method is used to solve the eigenvalues and eigenfunctions in the periodic chiral slabs. Mode-matching method is used at the boundaries to calculate the scattering characteristics. Numerical results are displayed to explain the underlying physical properties of the chiral periodic structure. The Wood's anomalies at high frequencies have been investigated and explained by the excitation of leaky waves guided along the periodic layer. The influence of frequency, chirality parameter, incident angle, curve shape and period are discussed. It has been found that the chiral periodic structure can be used as both a frequency selective device and a mode conversion device. First, the derivation and numeric calculation were done with the principal plane incidence. Then, the discussion was extended to the more general case of oblique incidence by the coordinate transformation.
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Date Issued: 2009
Identifier: CFE0002964, ucf:47987
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002964

Title: POLARIMETRIC CHARACTERIZATION OF RANDOM ELECTROMAGNETIC BEAMS AND APPLICATIONS.
Creator: Mujat, Mircea, Dogariu, Aristide, University of Central Florida
Abstract / Description: The polarimetric properties of random electromagnetic beams provide new means for characterizing random media. A novel interferometric technique is introduced for controlling the polarimetric, spectral, and coherence characteristics of random electromagnetic beams. Several new techniques are presented for measuring the state of polarization and the polarization transfer through scattering media. The polarimetric signatures of different particulate systems are related to their structural...
Show moreThe polarimetric properties of random electromagnetic beams provide new means for characterizing random media. A novel interferometric technique is introduced for controlling the polarimetric, spectral, and coherence characteristics of random electromagnetic beams. Several new techniques are presented for measuring the state of polarization and the polarization transfer through scattering media. The polarimetric signatures of different particulate systems are related to their structural properties and to the size distribution, shape, orientation, birefringent or dichroic properties of the particles. Various scattering regimes and different geometries are discussed for applications relevant to the bio-medical field, material science, and remote sensing.
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Date Issued: 2004
Identifier: CFE0000049, ucf:46132
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000049

Title: Image degradation due to surface scattering in the presence of aberrations.
Creator: Choi, Narak, Harvey, James, Zeldovich, Boris, Moharam, M., Eastes, Richard, University of Central Florida
Abstract / Description: 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...
Show moreThis 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 Beckman-Kirchhoff surface scatter theory), and the generalized Harvey-Shack surface scatter theory are adopted. As a numerical method, the integral equation method (method of moments) known as a rigorous solution is discussed. Since the numerical method is computationally too intensive to obtain the scattering prediction directly for the two mirror telescope, it is used for validating the three analytic approximate methods in special cases. In our numerical comparison work, among the three approximate methods, the generalized Harvey-Shack model shows excellent agreement to the rigorous solution and it is used to predict surface scattering from the mirror surfaces.Regarding image degradation due to surface scatter in the presence of aberrations, it is shown that the composite point spread function is obtained in explicit form in terms of convolutions of the geometrical point spread function and scaled bidirectional scattering distribution functions of the individual surfaces of the imaging system. The approximations and assumptions in this formulation are discussed. The result is compared to the irradiance distribution obtained using commercial non-sequential ray tracing software for the case of a two-mirror telescope operating at the extreme ultra-violet wavelengths and the two results are virtually identical. Finally, the image degradation due to the surface scatter from the mirror surfaces and the aberration of the telescope is evaluated in terms of the fractional ensquared energy (for different wavelengths and field angles) which is commonly used as an image quality requirement on many NASA astronomy programs.
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Date Issued: 2012
Identifier: CFE0004289, ucf:49492
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004289

Title: APPLICATIONS OF LINEAR AND NONLINEAR OPTICAL EFFECTS IN LIQUID CRYSTALS.
Creator: Sarkissian, Hakob, Zeldovich, Boris, University of Central Florida
Abstract / Description: Liquid crystals have been a major subject of research for the past decades. Aside from the variety of structures they can form, they exhibit a vast range of optical phenomena. Many of these phenomena found applications in technology and became an essential part of it. In this dissertation thesis we continue the line to propose a number of new applications of optical effects in liquid crystals and develop their theoretical framework. One such application is the possibility of beam combining...
Show moreLiquid crystals have been a major subject of research for the past decades. Aside from the variety of structures they can form, they exhibit a vast range of optical phenomena. Many of these phenomena found applications in technology and became an essential part of it. In this dissertation thesis we continue the line to propose a number of new applications of optical effects in liquid crystals and develop their theoretical framework. One such application is the possibility of beam combining using Orientational Stimulated Scattering in a nematic liquid crystal cell. Our numerical study of the OSS process shows that normally this possibility does not exist. However, we found that if a number of special conditions is satisfied efficient beam combining with OSS can be done. These conditions require a combination of special geometric arrangement of incident beams, their profiles, nematic material, and more. When these conditions are fulfilled, power of the beamlets can be coherently combined into a single beam, with high conversion efficiency while the shape and wave-front of the output beam are still of good quality. We also studied the dynamics of the OSS process itself and observed (in a numerical model) a number of notorious instabilities caused by effects of back-conversion iv process. Additionally, there was found a numerical solitary-wave solution associated with this back-conversion process. As a liquid crystal display application, we consider a nematic liquid crystal layer with the anisotropy axis modulated at a fixed rate in the transverse direction with respect to light propagation direction. If the layer locally constitutes a half-wave plate, then the thinscreen approximation predicts 100% -efficient diffraction of normal incident wave. If this diffracted light is blocked by an aperture only transmitting the zero-th order, the cell is in dark state. If now the periodic structure is washed out by applying voltage across the cell and light passes through the cell undiffracted, the light will pass through the aperture as well and the cell will be in its bright state. Such properties of this periodically aligned nematic layer suggest it as a candidate element in projection display cells. We studied the possibility to implement such layer through anchoring at both surfaces of the cell. It was found that each cell has a thickness threshold for which the periodic structure can exist. The anchored periodic structure cannot exist if thickness of the cell exceeds this threshold. For the case when the periodic structure exists, we found the structure distortion in comparison with the preferable ideal sinusoidal profile. To complete description of the electromechanical properties of the periodic cell, we studied its behavior at Freedericksz transition. Optical performance was successfully described with the coupled-mode theory. While influence of director distortion is shown to be negligibly small, the walk-off effects appear to be larger. In summary, there are good prospects for use of this periodically v aligned cell as a pixel in projection displays but experimental study and optimization need to be performed. In the next part we discuss another modulated liquid crystal structure in which the director periodically swings in the direction of light propagation. The main characteristic of such structure is the presence of bandgap. Cholesteric liquid crystals are known to possess bandgap for one of two circular polarizations of light. However, unlike the cholesterics the bandgap of the proposed structure is independent of polarization of normally incident light. This means that no preparation of light is needed in order for the structure to work in, for example, liquid crystal displays. The polarization universality comes at the cost of bandgap size, whose maximum possible value ∆ωPTN compared to that of cholesterics ∆ωCh is approximately twice smaller: ∆ωPTN ≈ 0.58∆ωCh if modulation profile is sinusoidal, and ∆ωPTN ≈ 0.64∆ωCh if it is rectangular. This structure has not yet been experimentally demonstrated, and we discuss possible ways to make it.
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Date Issued: 2006
Identifier: CFE0001164, ucf:46856
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001164

Title: MULTIPLE SCATTERING OF LIGHT IN INHOMOGENEOUS MEDIA AND APPLICATIONS.
Creator: Mujat, Claudia, Dogariu, Aristide, University of Central Florida
Abstract / Description: 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...
Show moreLight 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 the boundaries, absorption and morphology of the investigated media. A novel Monte Carlo simulation was developed to describe the statistics of partially coherent beams after propagation through inhomogeneous media. The Monte Carlo approach also enabled us to study the influence of the refractive index contrast on the diffusive processes, to discern between different effects of absorption in multiple scattering, and to support experimental results on inhomogeneous media with complex morphology. A detailed description of chromatic effects in scattering was used to develop new models that explain the spectral dependence of the detected signal in applications such as imaging and diffuse reflectance measurements. The quantitative and non-invasive characterization of inhomogeneous media with complex structures, such as porous membranes, diffusive coatings, and incipient lesions in natural teeth was then demonstrated.
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Date Issued: 2004
Identifier: CFE0000048, ucf:46143
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000048

Title: NEURAL NETWORKS SATISFYING STONE-WEIESTRASS THEOREM AND APPROXIMATING SCATTERED DATABYKOHONEN NEURAL NETWORKS.
Creator: Thakkar, Pinal, Mohapatra, Ram, University of Central Florida
Abstract / Description: Neural networks are an attempt to build computer networks called artificial neurons, which imitate the activities of the human brain. Its origin dates back to 1943 when neurophysiologist Warren Me Cello and logician Walter Pits produced the first artificial neuron. Since then there has been tremendous development of neural networks and their applications to pattern and optical character recognition, speech processing, time series prediction, image processing and scattered data approximation....
Show moreNeural networks are an attempt to build computer networks called artificial neurons, which imitate the activities of the human brain. Its origin dates back to 1943 when neurophysiologist Warren Me Cello and logician Walter Pits produced the first artificial neuron. Since then there has been tremendous development of neural networks and their applications to pattern and optical character recognition, speech processing, time series prediction, image processing and scattered data approximation. Since it has been shown that neural nets can approximate all but pathological functions, Neil Cotter considered neural network architecture based on Stone-Weierstrass Theorem. Using exponential functions, polynomials, rational functions and Boolean functions one can follow the method given by Cotter to obtain neural networks, which can approximate bounded measurable functions. Another problem of current research in computer graphics is to construct curves and surfaces from scattered spatial points by using B-Splines and NURBS or Bezier surfaces. Hoffman and Varady used Kohonen neural networks to construct appropriate grids. This thesis is concerned with two types of neural networks viz. those which satisfy the conditions of the Stone-Weierstrass theorem and Kohonen neural networks. We have used self-organizing maps for scattered data approximation. Neural network Tool Box from MATLAB is used to develop the required grids for approximating scattered data in one and two dimensions.
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Date Issued: 2004
Identifier: CFE0000226, ucf:46262
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000226

Title: UP-CONVERSION IN RARE-EARTH DOPED MICRO-PARTICLES APPLIED TO NEW EMISSIVE 2D DISLAYS.
Creator: Milliez, Anne, Bass, Michael, University of Central Florida
Abstract / Description: Up-conversion (UC) in rare-earth co-doped fluorides to convert diode laser light in the near infrared to red, green and blue visible light is applied to make possible high performance emissive displays. The infrared-to-visible UC in the materials we study is a sequential form of non-linear two photon absorption in which a strong absorbing constituent absorbs two low energy photons and transfers this energy to another constituent which emits visible light. Some of the UC emitters' most...
Show moreUp-conversion (UC) in rare-earth co-doped fluorides to convert diode laser light in the near infrared to red, green and blue visible light is applied to make possible high performance emissive displays. The infrared-to-visible UC in the materials we study is a sequential form of non-linear two photon absorption in which a strong absorbing constituent absorbs two low energy photons and transfers this energy to another constituent which emits visible light. Some of the UC emitters' most appealing characteristics for displays are: a wide color gamut with very saturated colors, very high brightness operation without damage to the emitters, long lifetimes and efficiencies comparable to those of existing technologies. Other advantages include simplicity of fabrication, versatility of operating modes, and the potential for greatly reduced display weight and depth. Thanks to recent advances in material science and diode laser technology at the excitation wavelength, UC selected materials can be very efficient visible emitters. However, optimal UC efficiencies strongly depend on chosing proper operating conditions. In this thesis, we studied the conditions required for optimization. We demonstrated that high efficiency UC depends on high pump irradiance, low temperature and low scattering. With this understanding we can predict how to optimally use UC emitters in a wide range of applications. In particular, we showed how our very efficient UC emitters can be applied to make full color displays and very efficient white light sources.
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Date Issued: 2006
Identifier: CFE0001058, ucf:46828
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001058

Title: Testing the Capability of Close-Range Photogrammetry to Document Outdoor Forensic Scenes With Skeletal Remains Using Mock Scenarios.
Creator: Gidusko, Kevin, Schultz, John, Branting, Scott, Walker, John, University of Central Florida
Abstract / Description: More rigorous methodological protocols are needed to document outdoor forensic scenes containing skeletal remains. However, law enforcement protocols rarely provide specific guidelines for processing these scenes. Regardless, the need to preserve contextual information at crime scenes is of paramount importance and it is worth exploring new technological applications that will allow for better documentation. Close-range photogrammetry (CRP) is one option for outdoor scene documentation, more...
Show moreMore rigorous methodological protocols are needed to document outdoor forensic scenes containing skeletal remains. However, law enforcement protocols rarely provide specific guidelines for processing these scenes. Regardless, the need to preserve contextual information at crime scenes is of paramount importance and it is worth exploring new technological applications that will allow for better documentation. Close-range photogrammetry (CRP) is one option for outdoor scene documentation, more prominently utilized in archaeological contexts, that may provide forensic archaeologists with a tool to better document these scenarios via 3D modeling. To test the efficacy of CRP as documentation tool three mock scenarios representing common outdoor scenes were created using faux osteological material: a close scatter of osteological remains in a pine flatwood setting, a wide scatter of osteological remains in the same setting, and the partial excavation of skeletonized remains. Images were collected using a digital camera and processed using Agisoft Photoscan Professional. A series of variables were tested in successive iterations of data capture for each scenario to determine best practices for overall accuracy: camera images captured by hand versus fixed to a tripod, scale bar positioning, and number of images captured. Accuracy was determined via final root mean square error values and through a comparison between real-world to virtual measurements. Results show that CRP is a cost and time-effective method of documenting contextual data at a scene via the creation of 3D models and scaled orthomosaic images. This method is most useful for the documentation of excavations owing to the controlled and contrasted sub-surface in comparison to the subject material. The two scatter scenarios offered additional challenges due to the complexity of the ground covering, however models nonetheless provided accurate contextual detail and errors may be mitigated through proper data capture. There was little difference in the variables for image capture, scale bar placement, or number of images. Instead, the quality of images, image capture method, and post-processing operations proved to be more important. Due to the ease of use and the ability to convey best practices for data capture, the utilization of CRP for outdoor scene documentation is recommended as a valuable addition to current forensic documentation protocols. Future research should focus on the utilization of actual osteological material as a proxy for forensic scenarios as well as study the applicability of CRP to assist in documenting taphonomic modifications.
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Date Issued: 2018
Identifier: CFE0007182, ucf:52261
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007182

Title: Third-order optical nonlinearities for integrated microwave photonics applications.
Creator: Malinowski, Marcin, Fathpour, Sasan, Delfyett, Peter, Christodoulides, Demetrios, Lyakh, Arkadiy, University of Central Florida
Abstract / Description: The field of integrated photonics aims at compressing large and environmentally-sensitive opticalsystems to micron-sized circuits that can be mass-produced through existing semiconductor fabri-cation facilities. The integration of optical components on single chips is pivotal to the realizationof miniature systems with high degree of complexity. Such novel photonic chips find abundant ap-plications in optical communication, spectroscopy and signal processing. This work concentrateson...
Show moreThe field of integrated photonics aims at compressing large and environmentally-sensitive opticalsystems to micron-sized circuits that can be mass-produced through existing semiconductor fabri-cation facilities. The integration of optical components on single chips is pivotal to the realizationof miniature systems with high degree of complexity. Such novel photonic chips find abundant ap-plications in optical communication, spectroscopy and signal processing. This work concentrateson harnessing nonlinear phenomena to this avail.The first part of this dissertation discusses, both from component and system level, the developmentof a frequency comb source with a semiconductor mode-locked laser at its heart. New nonlinear de-vices for supercontinuum and second-harmonic generations are developed and their performance isassessed inside the system. Theoretical analysis of a hybrid approach with synchronously-pumpedKerr cavity is also provided. The second part of the dissertation investigates stimulated Brillouinscattering (SBS) in integrated photonics. A fully-tensorial open-source numerical tool is developedto study SBS in optical waveguides composed of crystalline materials, particularly silicon. SBS isdemonstrated in an all-silicon optical platform.
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Date Issued: 2019
Identifier: CFE0007674, ucf:52497
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007674

Title: Development of laser spectroscopy for elemental and molecular analysis.
Creator: Liu, Yuan, Richardson, Martin, Vanstryland, Eric, Bass, Michael, Sigman, Michael, University of Central Florida
Abstract / Description: Laser-Induced Breakdown Spectroscopy (LIBS) and Raman spectroscopy are still growing analytical and sensing spectroscopic techniques. They significantly reduce the time and labor cost in analysis with simplified instrumentation, and lead to minimal or no sample damage. In this dissertation, fundamental studies to improve LIBS analytical performance were performed and its fusion with Raman into one single sensor was explored.On the fundamental side, Thomson scattering was reported for the...
Show moreLaser-Induced Breakdown Spectroscopy (LIBS) and Raman spectroscopy are still growing analytical and sensing spectroscopic techniques. They significantly reduce the time and labor cost in analysis with simplified instrumentation, and lead to minimal or no sample damage. In this dissertation, fundamental studies to improve LIBS analytical performance were performed and its fusion with Raman into one single sensor was explored.On the fundamental side, Thomson scattering was reported for the first time to simultaneously measure the electron density and temperature of laser plasmas from a solid aluminum target at atmospheric pressure. Comparison between electron and excitation temperatures brought insights into the verification of local thermodynamic equilibrium condition in laser plasmas.To enhance LIBS emission, Microwave-Assisted LIBS (MA-LIBS) was developed and characterized. In MA-LIBS, a microwave field extends the emission lifetime of the plasma and stronger time integrated signal is obtained. Experimental results showed sensitivity improvement (more than 20-fold) and extension of the analytical range (down to a few tens of ppm) for the detection of copper traces in soil samples. Finally, laser spectroscopy systems that can perform both LIBS and Raman analysis were developed. Such systems provide two types of complimentary information (-) elemental composition from LIBS and structural information from Raman. Two novel approaches were reported for the first time for LIBS-Raman sensor fusion: (i) an Ultra-Violet system which combines Resonant Raman signal enhancement and high ablation efficiency from UV radiation, and (ii) a Ti:Sapphire laser based NIR system which reduces the fluorescence interference in Raman and takes advantage of femtosecond ablation for LIBS.
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Date Issued: 2013
Identifier: CFE0005105, ucf:50729
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005105

Title: RESPONSE-CALIBRATION TECHNIQUES FOR ANTENNA-COUPLED INFRARED SENSORS.
Creator: Krenz, Peter, Boreman, Glenn, University of Central Florida
Abstract / Description: Infrared antennas are employed in sensing applications requiring specific spectral, polarization, and directional properties. Because of their inherently small dimensions, there is significant interaction, both thermal and electromagnetic, between the antenna, the antenna-coupled sensor, and the low-frequency readout structures necessary for signal extraction at the baseband modulation frequency. Validation of design models against measurements requires separation of these effects so that the...
Show moreInfrared antennas are employed in sensing applications requiring specific spectral, polarization, and directional properties. Because of their inherently small dimensions, there is significant interaction, both thermal and electromagnetic, between the antenna, the antenna-coupled sensor, and the low-frequency readout structures necessary for signal extraction at the baseband modulation frequency. Validation of design models against measurements requires separation of these effects so that the response of the antenna-coupled sensor alone can be measured in a calibrated manner. Such validations will allow confident extension of design techniques to more complex infrared-antenna configurations. Two general techniques are explored to accomplish this goal. The extraneous signal contributions can be measured separately with calibration structures closely co-located near the devices to be characterized. This approach is demonstrated in two specific embodiments, for removal of cross-polarization effects arising from lead lines in an antenna-coupled infrared dipole, and for removal of distributed thermal effects in an infrared phased-array antenna. The second calibration technique uses scanning near-field microscopy to experimentally determine the spatial dependence of the electric-field distributions on the signal-extraction structures, and to include these measured fields in the computational electromagnetic model of the overall device. This approach is demonstrated for infrared dipole antennas which are connected to coplanar strip lines. Specific situations with open-circuit and short-circuit impedances at the termination of the lines are investigated.
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Date Issued: 2010
Identifier: CFE0003177, ucf:48606
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003177

Title: Properties of High Energy Laser Light Transmission through Large Core Optical Cables.
Creator: Kennedy, Christopher, Schulzgen, Axel, Bass, Michael, Soileau, Marion, Gordon, Ali, University of Central Florida
Abstract / Description: Laser induced damage is of interest in studying the transmission of large amounts of optical energy through step-index, large core multimode fibers. Optical fibers often have to be routed around objects when laser light is being transmitted between two locations which require the fiber to bend into a curve. Depending on how tight the bend is, this can result in transmission losses or even catastrophic damage when the energy density of the laser pulse exceeds the damage threshold of silica...
Show moreLaser induced damage is of interest in studying the transmission of large amounts of optical energy through step-index, large core multimode fibers. Optical fibers often have to be routed around objects when laser light is being transmitted between two locations which require the fiber to bend into a curve. Depending on how tight the bend is, this can result in transmission losses or even catastrophic damage when the energy density of the laser pulse exceeds the damage threshold of silica glass. Waveguide theory predicts that light traveling through a bend will form whispering-gallery modes that propagate through total internal reflection bounces along the inside of the outer edge of the bend. This is critical since in these locations the energy density of the light will increase significantly, raising the potential of laser damage, nonlinear effects, and transmission losses. This loss is especially problematic when two 90(&)deg; bends going in opposite directions are in close proximity to each other, forming an 'S-bend'. Light that is grouped along the outer edge going through the first bend will enter the second bend at a sharper angle which causes much high transmission losses and raises the possibility of failure.Models using R-Soft BeamProp and Zemax were developed to study transmission losses, investigate light interactions at critical areas, and predict under which conditions laser damage would occur. BeamProp presents a clearer view of the modal distribution of light within the core of the fiber and is used to analyze how a plane wave with a Gaussian intensity distribution excites the fiber modes. Zemax provides a tool to perform non-sequential ray tracing through the fiber cable and stray light analysis within the core and once the light exits the fiber. Intensity distributions of the cross sectional area of the fiber shows the whispering gallery modes forming as the light propagates around bends and disburses as it propagates afterwards. It was discovered using R-Soft that if the separation distance between bends in an S-bend is approximately 3 mm there exists a condition where maximum transmission occurs. For 365 (&)#181;m diameter core fiber it was calculated that the difference in output power could be as high as 150%. This was initially completely unexpected; however ray tracing using Zemax was able to verify that this distance allows the light to transition so that it enters the 2nd bend at the optimal angle to enter the whispering gallery mode. Experiments were performed that validated the models' predictions and images were captured clearly showing the spatial distribution shift of the light within the core of the fiber.Experiments were performed to verify light grouping together to form whispering gallery modes as predicted by Zemax. Microscope images were taken as a function of distance from various bends to observe the periodic nature in which the laser light fills up the fiber. Additionally, a configuration was setup to examine stimulated Brillioun scattering and determine the onset of laser damage in the fiber. Fibers were tested as a function of bend radius and number of shots and recommendations for future systems were made. Lastly, mechanical failure tests were performed to determine the relationship between stress placed on the fiber through bending and fiber lifetime in a static environment. This allowed a minimum safe bend radius to be calculated for a 30 year lifetime that agreed with previous calculated values.
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Date Issued: 2013
Identifier: CFE0004871, ucf:49668
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004871

Title: MONTE CARLO SIMULATION OF HOLE TRANSPORT AND TERAHERTZ AMPLIFICATION IN MULTILAYER DELTA DOPED SEMICONDUCTOR STRUCTURES.
Creator: Dolguikh, Maxim, Peale, Robert, University of Central Florida
Abstract / Description: Monte Carlo method for the simulation of hole dynamics in degenerate valence subbands of cubic semiconductors is developed. All possible intra- and inter-subband scattering rates are theoretically calculated for Ge, Si, and GaAs. A far-infrared laser concept based on intersubband transitions of holes in p-type periodically delta-doped semiconductor films is studied using numerical Monte-Carlo simulation of hot hole dynamics. The considered device consists of monocrystalline pure Ge layers...
Show moreMonte Carlo method for the simulation of hole dynamics in degenerate valence subbands of cubic semiconductors is developed. All possible intra- and inter-subband scattering rates are theoretically calculated for Ge, Si, and GaAs. A far-infrared laser concept based on intersubband transitions of holes in p-type periodically delta-doped semiconductor films is studied using numerical Monte-Carlo simulation of hot hole dynamics. The considered device consists of monocrystalline pure Ge layers periodically interleaved with delta-doped layers and operates with vertical or in-plane hole transport in the presence of a perpendicular in-plane magnetic field. Inversion population on intersubband transitions arises due to light hole accumulation in E B fields, as in the bulk p-Ge laser. However, the considered structure achieves spatial separation of hole accumulation regions from the doped layers, which reduces ionized-impurity and carrier-carrier scattering for the majority of light holes. This allows remarkable increase of the gain in comparison with bulk p-Ge lasers. Population inversion and gain sufficient for laser operation are expected up to 77 K. Test structures grown by chemical vapor deposition demonstrate feasibility of producing the device with sufficient active thickness to allow quasioptical electrodynamic cavity solutions. The same device structure is considered in GaAs. The case of Si is much more complicated due to strong anisotropy of the valence band. The primary new result for Si is the first consideration of the anisotropy of optical phonon scattering for hot holes.
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Date Issued: 2005
Identifier: CFE0000863, ucf:46672
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000863

Title: THEORETICAL TAILORING OF PERFORATED THIN SILVER FILMS FOR AFFINITY SURFACE PLASMON RESONANCE BIOSENSOR APPLICATIONS.
Creator: Gongora Jr., Renan, Zou, Shengli, University of Central Florida
Abstract / Description: Metallic films, in conjunction with biochemical-targeted probes, are expected to provide early diagnosis, targeted therapy and non-invasive monitoring for epidemiology applications. The resonance wavelength peaks, both plasmonic and Wood-Rayleigh Anomalies (WRAs), in the scattering spectra are affected by the metallic architecture. As of today, much research has been devoted to extinction efficiency in the plasmonic region. However, Wood Rayleigh Anomalies (WRAs) typically occur at...
Show moreMetallic films, in conjunction with biochemical-targeted probes, are expected to provide early diagnosis, targeted therapy and non-invasive monitoring for epidemiology applications. The resonance wavelength peaks, both plasmonic and Wood-Rayleigh Anomalies (WRAs), in the scattering spectra are affected by the metallic architecture. As of today, much research has been devoted to extinction efficiency in the plasmonic region. However, Wood Rayleigh Anomalies (WRAs) typically occur at wavelengths associated with the periodic distance of the structures. A significant number of papers have already focused on the plasmonic region of the visible spectrum, but a less explored area of research was presented here; the desired resonance wavelength region was 400-500nm, corresponding to the WRA for the silver film with perforated hole with a periodic distance of 400nm. Simulations obtained from the discrete dipole approximation (DDA) method, show sharp spectral bands (either high or low scattering efficiencies) in both wavelength regions of the visible spectrum simulated from Ag film with cylindrical hole arrays In addition, surprising results were obtained in the parallel scattering spectra,where the electric field is contained in the XY plane, when the angle between the metallic surface and the incident light was adjusted to 14 degrees; a bathochromic shift was observed for the WRA peak suggesting a hybrid resonance mode. Metallic films have the potential to be used in instrumental techniques for use as sensors, i.e. surface plasmon resonance affinity biosensors, but are not limited to such instrumental techniques. Although the research here was aimed towards affinity biosensors, other sensory designs can benefit from the optimized Ag film motifs. The intent of the study was to elucidate metal film motifs, when incorporated into instrumental analysis, allowing the quantification of genetic material in the visible region. Any research group that routinely benefits from quantification of various analytes in solution matrices will also benefit from this study, as there are a bewildering number of instrumental sensory methods and setups available.
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Date Issued: 2014
Identifier: CFH0004538, ucf:45155
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH0004538

scattering (4)	+ -
Scattering (3)	+ -
Discrete Dipole Approximation (2)	+ -
Polarization (2)	+ -
coherence (2)	+ -

dynamic light scattering (2)	+ -
laser (2)	+ -
3D (1)	+ -
APPROXIMATION OF SCATTERED DATA (1)	+ -
Biosensors (1)	+ -
Cassegrain (1)	+ -
Chirality (1)	+ -
Close-Range Photogrammetry (1)	+ -
Computational Chemistry (1)	+ -
Continuous metal film (1)	+ -
Coupling mode (1)	+ -
Diffusion (1)	+ -
Displays (1)	+ -
Enhanced electric fields. (1)	+ -
Excavation (1)	+ -
Fano Resonance (1)	+ -
Fiber Laser (1)	+ -
Forensic Archaeology (1)	+ -
Forensics (1)	+ -
GHS (1)	+ -
GaAs (1)	+ -
Gold nanoparticle (1)	+ -
Interaction (1)	+ -
KA (1)	+ -
KOHONEN NEURAL NETWORKS (1)	+ -

ETD Collection (21)	+ -
Honors Collection (1)	+ -

University of Central Florida (22)	+ -
Dogariu, Aristide (5)	+ -
Bass, Michael (3)	+ -
Schulzgen, Axel (3)	+ -
Zou, Shengli (3)	+ -

Christodoulides, Demetrios (2)	+ -
Harvey, James (2)	+ -
Huo, Qun (2)	+ -
Tamasan, Alexandru (2)	+ -
Zeldovich, Boris (2)	+ -
Zhai, Lei (2)	+ -
Amezcua Correa, Rodrigo (1)	+ -
Boreman, Glenn (1)	+ -
Branting, Scott (1)	+ -
Broky, John (1)	+ -
Chen, Gang (1)	+ -
Choi, Narak (1)	+ -
Delfyett, Peter (1)	+ -
Dolguikh, Maxim (1)	+ -
Eastes, Richard (1)	+ -
Fathpour, Sasan (1)	+ -
Gesquiere, Andre (1)	+ -
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Gordon, Ali (1)	+ -
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Kang, Hyeran (1)	+ -
Kennedy, Christopher (1)	+ -
Kohlgraf-Owens, Thomas (1)	+ -
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