View All Items

Title: ON THE USE OF VARIABLE COHERENCE IN INVERSE SCATTERING PROBLEMS.
Creator: Baleine, Erwan, Dogariu, Aristide, University of Central Florida
Abstract / Description: Even though most of the properties of optical fields, such as wavelength, polarization, wavefront curvature or angular spectrum, have been commonly manipulated in a variety of remote sensing procedures, controlling the degree of coherence of light did not find wide applications until recently. Since the emergence of optical coherence tomography, a growing number of scattering techniques have relied on temporal coherence gating which provides efficient target selectivity in a way achieved only...
Show moreEven though most of the properties of optical fields, such as wavelength, polarization, wavefront curvature or angular spectrum, have been commonly manipulated in a variety of remote sensing procedures, controlling the degree of coherence of light did not find wide applications until recently. Since the emergence of optical coherence tomography, a growing number of scattering techniques have relied on temporal coherence gating which provides efficient target selectivity in a way achieved only by bulky short pulse measurements. The spatial counterpart of temporal coherence, however, has barely been exploited in sensing applications. This dissertation examines, in different scattering regimes, a variety of inverse scattering problems based on variable spatial coherence gating. Within the framework of the radiative transfer theory, this dissertation demonstrates that the short range correlation properties of a medium under test can be recovered by varying the size of the coherence volume of an illuminating beam. Nonetheless, the radiative transfer formalism does not account for long range correlations and current methods for retrieving the correlation function of the complex susceptibility require cumbersome cross-spectral density measurements. Instead, a variable coherence tomographic procedure is proposed where spatial coherence gating is used to probe the structural properties of single scattering media over an extended volume and with a very simple detection system. Enhanced backscattering is a coherent phenomenon that survives strong multiple scattering. The variable coherence tomography approach is extended in this context to diffusive media and it is demonstrated that specific photon trajectories can be selected in order to achieve depth-resolved sensing. Probing the scattering properties of shallow and deeper layers is of considerable interest in biological applications such as diagnosis of skin related diseases. The spatial coherence properties of an illuminating field can be manipulated over dimensions much larger than the wavelength thus providing a large effective sensing area. This is a practical advantage over many near-field microscopic techniques, which offer a spatial resolution beyond the classical diffraction limit but, at the expense of scanning a probe over a large area of a sample which is time consuming, and, sometimes, practically impossible. Taking advantage of the large field of view accessible when using the spatial coherence gating, this dissertation introduces the principle of variable coherence scattering microscopy. In this approach, a subwavelength resolution is achieved from simple far-zone intensity measurements by shaping the degree of spatial coherence of an evanescent field. Furthermore, tomographic techniques based on spatial coherence gating are especially attractive because they rely on simple detection schemes which, in principle, do not require any optical elements such as lenses. To demonstrate this capability, a correlated lensless imaging method is proposed and implemented, where both amplitude and phase information of an object are obtained by varying the degree of spatial coherence of the incident beam. Finally, it should be noted that the idea of using the spatial coherence properties of fields in a tomographic procedure is applicable to any type of electromagnetic radiation. Operating on principles of statistical optics, these sensing procedures can become alternatives for various target detection schemes, cutting-edge microscopies or x-ray imaging methods.
Show less
Date Issued: 2006
Identifier: CFE0001387, ucf:47005
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001387

Title: COHERENCE PROPERTIES OF OPTICAL NEAR-FIELDS.
Creator: Apostol, Adela, Dogariu, Aristide, University of Central Florida
Abstract / Description: 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...
Show moreNext 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 the conventional coherence theory disregard the contribution of short-range evanescent waves. Nonetheless, the specific features of random fields at subwavelength distances from interfaces of real media are influenced by the presence of evanescent waves because, in this case, both propagating and nonpropagating components contribute to the detectable properties of the radiation. In our studies, we have fully accounted for both contributions and, as a result, different surface and subsurface characteristics of inhomogeneous media could be explored. We investigated different properties of random optical near-fields which exhibit either Gaussian or non-Gaussian statistics. We have demonstrated that characteristics of optical radiation such as first- and second-order statistics of intensity and the spectral density in the vicinity of random media are all determined by both evanescent waves contribution and the statistical properties of the physical interface. For instance, we quantified the subtle differences which exist between the near- and far-field spectra of radiation and we brought the first experimental evidence that, contrary to the predictions of the conventional coherence theory, the values of coherence length in the near field depend on the distance from the interface and, moreover, they can be smaller than the wavelength of light. The results included in this dissertation demonstrate that the statistical properties of the electromagnetic fields which exist in the close proximity of inhomogeneous media can be used to extract structural information. They also suggest the possibility to adjust the coherence properties of the emitted radiation by modifying the statistical properties of the interfaces. Understanding the random interference phenomena in the near-field could also lead to new possibilities for surface and subsurface diagnostics of inhomogeneous media. In addition, controlling the statistical properties of radiation at subwavelength scales should be of paramount importance in the design of miniaturized optical sources, detectors and sensors.
Show less
Date Issued: 2005
Identifier: CFE0000408, ucf:46410
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000408

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.
Show less
Date Issued: 2004
Identifier: CFE0000049, ucf:46132
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000049

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.
Show less
Date Issued: 2004
Identifier: CFE0000048, ucf:46143
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000048

Title: POLARIMETRY OF RANDOM FIELDS.
Creator: Ellis, Jeremy, Dogariu, Aristide, University of Central Florida
Abstract / Description: On temporal, spatial and spectral scales which are small enough, all fields are fully polarized. In the optical regime, however, instantaneous fields can rarely be examined, and, instead, only average quantities are accessible. The study of polarimetry is concerned with both the description of electromagnetic fields and the characterization of media a field has interacted with. The polarimetric information is conventionally presented in terms of second order field correlations which are...
Show moreOn temporal, spatial and spectral scales which are small enough, all fields are fully polarized. In the optical regime, however, instantaneous fields can rarely be examined, and, instead, only average quantities are accessible. The study of polarimetry is concerned with both the description of electromagnetic fields and the characterization of media a field has interacted with. The polarimetric information is conventionally presented in terms of second order field correlations which are averaged over the ensemble of field realizations. Motivated by the deficiencies of classical polarimetry in dealing with specific practical situations, this dissertation expands the traditional polarimetric approaches to include higher order field correlations and the description of fields fluctuating in three dimensions. In relation to characterization of depolarizing media, a number of fourth-order correlations are introduced in this dissertation. Measurements of full polarization distributions, and the subsequent evaluation of Stokes vector element correlations and Complex Degree of Mutual Polarization demonstrate the use of these quantities for material discrimination and characterization. Recent advancements in detection capabilities allow access to fields near their sources and close to material boundaries, where a unique direction of propagation is not evident. Similarly, there exist classical situations such as overlapping beams, focusing, or diffusive scattering in which there is no unique transverse direction. In this dissertation, the correlation matrix formalism is expanded to describe three dimensional electromagnetic fields, providing a definition for the degree of polarization of such a field. It is also shown that, because of the dimensionality of the problem, a second parameter is necessary to fully describe the polarimetric properties of three dimensional fields. Measurements of second-order correlations of a three dimensional field are demonstrated, allowing the determination of both the degree of polarization and the state of polarization. These new theoretical concepts and innovative experimental approaches introduced in thiss dissertation are expected to impact scientific areas as diverse as near field optics, remote sensing, high energy laser physics, fluorescence microscopy, and imaging.
Show less
Date Issued: 2006
Identifier: CFE0000982, ucf:46697
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000982

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.
Show less
Date Issued: 2006
Identifier: CFE0001174, ucf:46852
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001174

Title: NEAR-FIELD OPTICAL INTERACTIONS AND APPLICATIONS.
Creator: Haefner, David, Dogariu, Aristide, University of Central Florida
Abstract / Description: The propagation symmetry of electromagnetic fields is affected by encounters with material systems. The effects of such interactions, for example, modifications of intensity, phase, polarization, angular spectrum, frequency, etc. can be used to obtain information about the material system. However, the propagation of electromagnetic waves imposes a fundamental limit to the length scales over which the material properties can be observed. In the realm of near-field optics, this limitation is...
Show moreThe propagation symmetry of electromagnetic fields is affected by encounters with material systems. The effects of such interactions, for example, modifications of intensity, phase, polarization, angular spectrum, frequency, etc. can be used to obtain information about the material system. However, the propagation of electromagnetic waves imposes a fundamental limit to the length scales over which the material properties can be observed. In the realm of near-field optics, this limitation is overcome only through a secondary interaction that couples the high-spatial-frequency (but non-propagating) field components to propagating waves that can be detected. The available information depends intrinsically on this secondary interaction, which constitutes the topic of this study. Quantitative measurements of material properties can be performed only by controlling the subtle characteristics of these processes. This dissertation discusses situations where the effects of near-field interactions can be (i) neglected in certain passive testing techniques, (ii) exploited for active probing of static or dynamic systems, or (iii) statistically isolated when considering optically inhomogeneous materials. This dissertation presents novel theoretical developments, experimental measurements, and numerical results that elucidate the vectorial aspects of the interaction between light and nano-structured material for use in sensing applications.
Show less
Date Issued: 2010
Identifier: CFE0003095, ucf:48318
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003095

Title: USING LOW-COHERENCE INTERFEROMETRY TO MONITOR CELL INVASION IN AN IN-VITRO MODEL SYSTEM.
Creator: Davoudi Nasab, Behnaz, Dogariu, Aristide, Andl, Claudia, University of Central Florida
Abstract / Description: In an optically random system, such as naturally occurring and man-made media, light undergoes pronounced multiple scattering. This phenomenon has shown a remarkable potential in characterizing complex materials. In this regime, scattering occurs from each individual center of the scattering and independent scattering events lead to multiple light scattering. This phenomenon is often described as a random walk of photons and can be modeled in terms of a diffusion equation based on the...
Show moreIn an optically random system, such as naturally occurring and man-made media, light undergoes pronounced multiple scattering. This phenomenon has shown a remarkable potential in characterizing complex materials. In this regime, scattering occurs from each individual center of the scattering and independent scattering events lead to multiple light scattering. This phenomenon is often described as a random walk of photons and can be modeled in terms of a diffusion equation based on the radiative transfer theory. In this thesis, we used optical path-length spectroscopy (OPS), which is an experimental method to obtain the path-length probability density of the propagating light in multiple scattering media, with a low-coherence optical field to investigate the distribution of photon path lengths in a skin cell model system. This method is capable of measuring the transport mean free path of light in a highly scattering medium and depth-resolved profiles of the backscattered light. Our OPS experimental configuration is based on a fiber-optic Michelson interferometer geometry using single mode optical fibers. We performed OPS based on low-coherence interferometry (LCI) on three-dimensional organotypic models of esophageal cell invasion by measuring the optical path-length distribution of backscattered light in normal and invasive conditions. The optical path-length distribution of light waves inside the cell samples provides information on how a change in the extracellular matrix affects invasiveness of the esophageal cells and induction of signaling pathways. Also, we demonstrated the compatibility to study the structural changes during a two-week period for in vitro cell samples.
Show less
Date Issued: 2017
Identifier: CFH2000219, ucf:45955
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH2000219

Title: Harnessing Spatial Intensity Fluctuations for Optical Imaging and Sensing.
Creator: Akhlaghi Bouzan, Milad, Dogariu, Aristide, Saleh, Bahaa, Pang, Sean, Atia, George, University of Central Florida
Abstract / Description: Properties of light such as amplitude and phase, temporal and spatial coherence, polarization, etc. are abundantly used for sensing and imaging. Regardless of the passive or active nature of the sensing method, optical intensity fluctuations are always present! While these fluctuations are usually regarded as noise, there are situations where one can harness the intensity fluctuations to enhance certain attributes of the sensing procedure. In this thesis, we developed different sensing...
Show moreProperties of light such as amplitude and phase, temporal and spatial coherence, polarization, etc. are abundantly used for sensing and imaging. Regardless of the passive or active nature of the sensing method, optical intensity fluctuations are always present! While these fluctuations are usually regarded as noise, there are situations where one can harness the intensity fluctuations to enhance certain attributes of the sensing procedure. In this thesis, we developed different sensing methodologies that use statistical properties of optical fluctuations for gauging specific information. We examine this concept in the context of three different aspects of computational optical imaging and sensing. First, we study imposing specific statistical properties to the probing field to image or characterize certain properties of an object through a statistical analysis of the spatially integrated scattered intensity. This offers unique capabilities for imaging and sensing techniques operating in highly perturbed environments and low-light conditions. Next, we examine optical sensing in the presence of strong perturbations that preclude any controllable field modification. We demonstrate that inherent properties of diffused coherent fields and fluctuations of integrated intensity can be used to track objects hidden behind obscurants. Finally, we address situations where, due to coherent noise, image accuracy is severely degraded by intensity fluctuations. By taking advantage of the spatial coherence properties of optical fields, we show that this limitation can be effectively mitigated and that a significant improvement in the signal-to-noise ratio can be achieved even in one single-shot measurement. The findings included in this dissertation illustrate different circumstances where optical fluctuations can affect the efficacy of computational optical imaging and sensing. A broad range of applications, including biomedical imaging and remote sensing, could benefit from the new approaches to suppress, enhance, and exploit optical fluctuations, which are described in this dissertation.
Show less
Date Issued: 2017
Identifier: CFE0007274, ucf:52200
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007274

Title: Mesoscale Light-Matter Interactions.
Creator: Douglass, Kyle, Dogariu, Aristide, Abouraddy, Ayman, Hagan, David, Sugaya, Kiminobu, University of Central Florida
Abstract / Description: 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...
Show moreMesoscale 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 complex media. Dynamical and structural information from complex fluids(-)such as colloidal suspensions and biological fluids(-)was obtained by controlling the size of the interaction volume with low coherence interferometry. With this information, material properties such as particle sizes, optical transport coefficients, and viscoelastic characteristics of polymer solutions and blood were determined in natural, realistic conditions that are inaccessible to conventional techniques.The same framework also enabled the development of new, scale-dependent models for several important physical and biological systems. These models were then used to explain the results of some unique measurements. For example, the transport of light in disordered photonic lattices was interpreted as a scale-dependent, diffusive process to explain the anomalous behavior of photon path length distributions through these complex structures. In addition, it was demonstrated how specialized optical measurements and models at the mesoscale enable solutions to fundamental problems in cell biology. Specifically, it was found for the first time that the nature of cell motility changes markedly with the curvature of the substrate that the cellsivmove on. This particular work addresses increasingly important questions concerning the nature of cellular responses to external forces and the mechanical properties of their local environment.Besides sensing of properties and modeling behaviors of complex systems, mesoscale optics encompasses the control of material systems as a result of the light-matter interaction. Specific modifications to a material's structure can occur due to not only an exchange of energy between radiation and a material, but also due to a transfer of momentum. Based on the mechanical action of multiply scattered light on colloidal particles, an optically-controlled active medium that did not require specially tailored particles was demonstrated for the first time. The coupling between the particles and the random electromagnetic field affords new possibilities for controlling mesoscale systems and observing nonequilibrium thermodynamic phenomena.
Show less
Date Issued: 2013
Identifier: CFE0004990, ucf:49606
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004990

Title: Mesoscopic Interactions in Complex Photonic Media.
Creator: Rezvani Naraghi, Roxana, Dogariu, Aristide, Tetard, Laurene, Rahman, Talat, Abouraddy, Ayman, University of Central Florida
Abstract / Description: Mesoscale optics provides a framework for understanding a wide range of phenomena occurring in a variety of fields ranging from biological tissues to composite materials and from colloidal physics to fabricated nanostructures. When light interacts with a complex system, the outcome depends significantly on the length and time scales of interaction. Mesoscale optics offers the apparatus necessary for describing specific manifestations of wave phenomena such as interference and phase memory in...
Show moreMesoscale optics provides a framework for understanding a wide range of phenomena occurring in a variety of fields ranging from biological tissues to composite materials and from colloidal physics to fabricated nanostructures. When light interacts with a complex system, the outcome depends significantly on the length and time scales of interaction. Mesoscale optics offers the apparatus necessary for describing specific manifestations of wave phenomena such as interference and phase memory in complex media. In-depth understanding of mesoscale phenomena provides the required quantitative explanations that neither microscopic nor macroscopic models of light-matter interaction can afford. Modeling mesoscopic systems is challenging because the outcome properties can be efficiently modified by controlling the extent and the duration of interactions.In this dissertation, we will first present a brief survey of fundamental concepts, approaches, and techniques specific to fundamental light-matter interaction at mesoscopic scales. Then, we will discuss different regimes of light propagation through randomly inhomogenous media. In particular, a novel description will be introduced to analyze specific aspects of light propagation in dense composites. Moreover, we will present evidence that the wave nature of light can be critical for understanding its propagation in unbounded highly scattering materials. We will show that the perceived diffusion of light is subjected to competing mechanisms of interaction that lead to qualitatively different phases for the light evolution through complex media. In particular, we will discuss implications on the ever elusive localization of light in three-dimensional random media. In addition to fundamental aspects of light-matter interaction at mesoscopic scales, this dissertation will also address the process of designing material structures that provide unique scattering properties. We will demonstrate that multi-material dielectric particles with controlled radial and azimuthal structure can be engineered to modify the extinction cross-section, to control the scattering directivity, and to provide polarization-dependent scattering. We will show that dielectric core-shell structures with similar macroscopic sizes can have both high scattering cross-sections and radically different scattering phase functions. In addition, specific structural design, which breaks the azimuthal symmetry of the spherical particle, can be implemented to control the polarization properties of scattered radiation. Moreover, we will also demonstrate that the power flow around mesoscopic scattering particles can be controlled by modifying their internal heterogeneous structures.Lastly, we will show how the statistical properties of the radiation emerging from mesoscopic systems can be utilized for surface and subsurface diagnostics. In this dissertation, we will demonstrate that the intensity distributions measured in the near-field of composite materials are direct signatures of the scale-dependent morphology, which is determined by variations of the local dielectric function. We will also prove that measuring the extent of spatial coherence in the proximity of two-dimensional interfaces constitutes a rather general method for characterizing the defect density in crystalline materials. Finally, we will show that adjusting the spatial coherence properties of radiation can provide a simple solution for a significant deficiency of near-field microscopy. We will demonstrate experimentally that spurious interference effects can be efficiently eliminated in passive near-field imaging by implementing a random illumination.
Show less
Date Issued: 2017
Identifier: CFE0006647, ucf:51253
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006647

Title: Broadband Coherent Perfect Absorption in One-Dimensional Optical Systems.
Creator: Villinger, Massimo Maximilian, Abouraddy, Ayman, Dogariu, Aristide, Fathpour, Sasan, University of Central Florida
Abstract / Description: Absorption plays a critical role in a variety of optical applications (-) sometimes it is desirable to minimize it as in optical fibers and waveguides, or to enhance it as in solar cells and photodetectors. We describe here a new optical scheme that controllably produces high optical absorption over a broad wavelength range (hundreds of nm) in systems that have low intrinsic absorption over the same range. This effect, 'coherent perfect absorption' or CPA, arises from a subtle interplay...
Show moreAbsorption plays a critical role in a variety of optical applications (-) sometimes it is desirable to minimize it as in optical fibers and waveguides, or to enhance it as in solar cells and photodetectors. We describe here a new optical scheme that controllably produces high optical absorption over a broad wavelength range (hundreds of nm) in systems that have low intrinsic absorption over the same range. This effect, 'coherent perfect absorption' or CPA, arises from a subtle interplay between interference and absorption of two beams incident on a weakly absorbing medium. In the first part of this study, we present an analytical model that captures the relevant physics of CPA in one-dimensional photonic structures. This model elucidates an absorption-mediated interference effect that underlies CPA (-) an effect that is normally forbidden in Hermitian systems, but is allowed when conservation of energy is violated due to the inclusion of loss. As a concrete example, we consider a Fabry-P(&)#233;rot resonator containing a lossy dielectric and confirm this model through a computational study of a 1-micron-thick silicon layer in a cavity formed of dispersive mirrors with aperiodic multilayer design. We confirm that one may achieve 100% absorption in this thin silicon layer (whose intrinsic absorption is only ~ 3%) in the near-infrared. We then design two device models using few-micron-thick aperiodic planar dielectric mirrors and demonstrate (computationally, as well as experimentally) spectrally flat, coherently enhanced absorption at the theoretical limit in a 2-micron-thick film of polycrystalline silicon embedded in symmetric and asymmetric cavities. This coherent effect is observed over an octave-spanning wavelength range of ~800 (-) 1600 nm utilizing incoherent light in the near-infrared, exploiting mirrors that have wavelength-dependent reflectivity devised to counterbalance the decline in silicon's intrinsic absorption at long wavelengths. We anticipate that the design principles established here may be extended to other materials, broader spectral ranges, and large surface areas. Finally, we study the effect of the angle of incidence on CPA in planar structures. The results of this study point to a path for realizing CPA in such systems continuously over large bandwidths.
Show less
Date Issued: 2015
Identifier: CFE0006059, ucf:50985
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006059

Title: Nanoscale Control of Gap-plasmon Enhanced Optical Processes.
Creator: Lumdee, Chatdanai, Kik, Pieter, Dogariu, Aristide, Kuebler, Stephen, Huo, Qun, University of Central Florida
Abstract / Description: Surface plasmon resonances of metal nanostructures have been studied intensely in recent years. The strong plasmon-mediated electric field enhancement and field confinement well beyond the diffraction limit has been demonstrated to improve the performance of optical devices including ultrasensitive sensors, light emitters, and optical absorbers. A plasmon resonance mode of particular recent interest is the gap plasmon resonance that occurs on closely spaced metallic structures. In contrast to...
Show moreSurface plasmon resonances of metal nanostructures have been studied intensely in recent years. The strong plasmon-mediated electric field enhancement and field confinement well beyond the diffraction limit has been demonstrated to improve the performance of optical devices including ultrasensitive sensors, light emitters, and optical absorbers. A plasmon resonance mode of particular recent interest is the gap plasmon resonance that occurs on closely spaced metallic structures. In contrast to plasmon resonances supported by isolated metal nanostructures, coupled nanostructures provide additional spectral and spatial control over the plasmon resonance response. For example, the resonance frequencies of metal nanoparticle dimers depend strongly on the gap size between the nanoparticles. Gap plasmons can produce local electric field enhancement factors that are several orders of magnitude stronger and more confined than surface plasmon resonances of isolated plasmonic nanospheres. The reliance of gap plasmons on few-nanometer separation between nanostructures makes it difficult to prepare gap-plasmon supporting structures with predictable resonance frequency and field enhancement. A structure that avoids this challenge is the film-coupled nanoparticle (NP). Similar to nanoparticle dimers, a nanoparticle on a supporting metallic film (or NP-on-a-mirror) can offer a strong coupling between the particle and its local environment, in this case the supporting film instead of adjacent nanoparticles, enabling strongly confined gap-plasmon modes. The NP-on-a-mirror geometry has been shown to produce reproducible gap plasmon resonances in a chemically and thermally robust, easy to fabricate structure. In this Thesis, we first present a scheme for controlling the gap plasmon resonance frequency of single gold nanoparticles using aluminum oxide coated metal films. We demonstrate experimentally and numerically that the gap-plasmon resonance of single gold nanoparticles can be tuned throughout the visible range by controlling the aluminum oxide thickness via anodization. In a separate study of Au NP on Al2O3 coated gold films it is shown that the oxide coating improves the stability of the structure under intense laser irradiation. An combined experimental and numerical analysis of the spectral response of Au NP on rough Au films shows that a film roughness of a few nanometer can affect the gap plasmon resonance in the absence of an oxide spacer layer. A photoluminescence study of single gold nanoparticles on an Al2O3 coated gold film shows that the gap-plasmon resonance of this type of plasmonic structure can increase gold photoluminescence by more than four orders of magnitude. Related numerical simulations reveal that the local photoluminescence enhancement of a gold nanoparticle on an Al2O3 coated gold film can be as high as one million near the particle-film junction. Finally, a new plasmonic sensing element was proposed based on our findings in the previous chapters. This proposed hole-in-one structure offers several attractive features including an easily optically accessible gap plasmon mode, while maintaining a relatively simple fabrication method. Taken together, the research presented in this Thesis demonstrates how the resonance frequency, field enhancement, mode polarization, structural stability, and structure reliability can be controlled at the nanoscale. The knowledge gained in the course of this work could lead to further development of nanophotonic devices that utilize extremely confined optical fields and precisely controlled resonance frequencies.
Show less
Date Issued: 2015
Identifier: CFE0005972, ucf:50772
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005972

Title: Conservation Laws and Electromagnetic Interactions.
Creator: Kajorndejnukul, Veerachart, Dogariu, Aristide, Abouraddy, Ayman, Kik, Pieter, Rahman, Talat, University of Central Florida
Abstract / Description: Aside from energy, light carries linear and angular momenta that can be transferred to matter. The interaction between light and matter is governed by conservation laws that can manifest themselves as mechanical effects acting on both matter and light waves. This interaction permits remote, precise, and noninvasive manipulation and sensing at microscopic levels. In this dissertation, we demonstrated for the first time a complete set of opto-mechanical effects that are based on nonconservative...
Show moreAside from energy, light carries linear and angular momenta that can be transferred to matter. The interaction between light and matter is governed by conservation laws that can manifest themselves as mechanical effects acting on both matter and light waves. This interaction permits remote, precise, and noninvasive manipulation and sensing at microscopic levels. In this dissertation, we demonstrated for the first time a complete set of opto-mechanical effects that are based on nonconservative forces and act at the interface between dielectric media. Without structuring the light field, forward action is provided by the conventional radiation pressure while a backward movement can be achieved through the natural enhancement of linear momentum. If the symmetry of scattered field is broken, a side motion can also be induced due to the transformation between spin and orbital angular momenta. In experiments, these opto-mechanical effects can be significantly amplified by the long-range hydrodynamic interactions that provide an efficient recycling of energy. These unusual opto-mechanical effects open new possibilities for efficient manipulation of colloidal microparticles without having to rely on intricate structuring or shaping of light beams. Optically-controlled transport of matter is sought after in diverse applications in biology, colloidal physics, chemistry, condensed matter and others.Another consequence of light-matter interaction is the modification of the optical field itself, which can manifest, for instance, as detectable shifts of the centroids of optical beams during reflection and refraction. The spin-Hall effect of light (SHEL) is one type of such beam shifts that is due to the spin-orbit transformation governed by the conservation of angular momentum. We have shown that this effect can be amplified by the structural anisotropy of random nanocomposite materials.
Show less
Date Issued: 2015
Identifier: CFE0005961, ucf:50818
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005961

Title: OPTICAL PROPAGATION OF SELF-SUSTAINING WAVEFRONTS AND NONLINEAR DYNAMICS IN PARABOLIC MULTIMODE FIBERS.
Creator: Mills, Matthew, Christodoulides, Demetrios, Hagan, David, Dogariu, Aristide, Kaup, David, University of Central Florida
Abstract / Description: The aim of this thesis is to introduce my work which has generally been focused on opticalwavefronts that have the unusual property of resisting commonplace phenomena such as diffraction and dispersion. Interestingly, these special beams are found both in linear and nonlinear situations. For example, in the linear regime, localized spatio-temporal waves which resemble the spherical harmonic symmetries of the hydrogen quantum orbitals can simultaneously negotiate both diffractive and...
Show moreThe aim of this thesis is to introduce my work which has generally been focused on opticalwavefronts that have the unusual property of resisting commonplace phenomena such as diffraction and dispersion. Interestingly, these special beams are found both in linear and nonlinear situations. For example, in the linear regime, localized spatio-temporal waves which resemble the spherical harmonic symmetries of the hydrogen quantum orbitals can simultaneously negotiate both diffractive and dispersiveeffects. In the nonlinear regime, dressed optical filaments can be arranged to propagate multi-photon produced plasma channels orders of magnitude longer than expected.The first portion of this dissertation will begin by surveying the history of diffraction-free beamsand introducing some of their mathematical treatments. Interjected throughout this discussion will be several relevant concepts which I explored during my first years a CREOL. The discussion will then be steered into a detailed account of diffraction/dispersion free wavefronts which display hydrogen-like symmetries. The second segment of the document will cover the highly nonlinear process of optical filamentation. This chapter will almost entirely investigate the idea of the dressed filament, an entity which allows for substantial prolongation of this light string. I will then conclude by delving into the topicof supercontinuum generation in parabolic multimode fibers which, in the upcoming years, has great potential of becoming important in optics.
Show less
Date Issued: 2015
Identifier: CFE0005977, ucf:50767
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005977

Title: Filtering Problems in Stochastic Tomography.
Creator: Gomez, Tyler, Swanson, Jason, Yong, Jiongmin, Tamasan, Alexandru, Dogariu, Aristide, University of Central Florida
Abstract / Description: Distinguishing signal from noise has always been a major goal in probabilistic analysis of data. Such is no less the case in the field of medical imaging, where both the processes of photon emission and their rate of absorption by the body behave as random variables. We explore methods by which to extricate solid conclusions from noisy data involving an X-ray transform, long the mathematical mainstay of such tools as computed axial tomography (CAT scans). Working on the assumption of having...
Show moreDistinguishing signal from noise has always been a major goal in probabilistic analysis of data. Such is no less the case in the field of medical imaging, where both the processes of photon emission and their rate of absorption by the body behave as random variables. We explore methods by which to extricate solid conclusions from noisy data involving an X-ray transform, long the mathematical mainstay of such tools as computed axial tomography (CAT scans). Working on the assumption of having some prior probabilities assigned to various states a body can be found in, we introduce and make rigorous an understanding of how to condition these into posterior probabilities by using the scan data.
Show less
Date Issued: 2017
Identifier: CFE0006740, ucf:51839
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006740

Title: Beam Deflection.
Creator: Münnich, Matthias, Hagan, David, Vanstryland, Eric, Dogariu, Aristide, University of Central Florida
Abstract / Description: In order to fully understand the third order nonlinear optical response of materials under high irradianceexcitation it is necessary to study the temporal and polarization dependence of nonlinearrefraction and absorption. There are several existing approaches such as Z-scan and pump-probetechniques to determine those responses. As part of this work, these approaches will be briefly outlinedbefore presenting beam deflection, applied from photothermal beam deflection, as an...
Show moreIn order to fully understand the third order nonlinear optical response of materials under high irradianceexcitation it is necessary to study the temporal and polarization dependence of nonlinearrefraction and absorption. There are several existing approaches such as Z-scan and pump-probetechniques to determine those responses. As part of this work, these approaches will be briefly outlinedbefore presenting beam deflection, applied from photothermal beam deflection, as an alternativeexperimental technique to determine the nonlinear refraction with its temporal and polarizationdynamics. This technique measures the angle of the probe beam deflected via the index gradientof the material induced by strong excitation beam, to determine both the sign and magnitude of thenonlinear refraction. The temporal and tensor properties of the nonlinear refractive index can bedetermined by introducing a delay line, and by varying the polarization of the excitation and probebeam, respectively.To demonstrate the practicality of the beam deflection technique, we performed measurements onFused Silica, Carbon Disulfide and Zinc Oxide. Each of these samples shows quite different nonlinearresponses. Amorphous fused silica exhibits nonlinear refraction purely from instantaneouselectronic contribution; while Carbon Disulfide shows a much slower response, originating notonly from the electronic contribution but also from non-instantaneous nuclear movements (e.g.molecular orientation). These two contributions can be separated by varying the polarization directionof the excitation and probe beam. By introducing lock-in detection technique, a sensitivityof λ/5500 can be achieved. In Zinc Oxide, a wide-bandgap semiconductor, we measure bothnonlinear refraction and two-photon absorption simultaneously. Therefore the beam deflection isa sensitive technique, which can be used to measure the time and polarization dynamics of thenonlinear response of the material.
Show less
Date Issued: 2013
Identifier: CFE0004896, ucf:49653
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004896

Title: Detecting, Tracking, and Recognizing Activities in Aerial Video.
Creator: Reilly, Vladimir, Shah, Mubarak, Georgiopoulos, Michael, Stanley, Kenneth, Dogariu, Aristide, University of Central Florida
Abstract / Description: In this dissertation we address the problem of detecting humans and vehicles, tracking their identities in crowded scenes, and finally determining human activities. First, we tackle the problem of detecting moving as well as stationary objects in scenes that contain parallax and shadows. We constrain the search of pedestrians and vehicles by representing them as shadow casting out of plane or (SCOOP) objects.Next, we propose a novel method for tracking a large number of densely moving objects...
Show moreIn this dissertation we address the problem of detecting humans and vehicles, tracking their identities in crowded scenes, and finally determining human activities. First, we tackle the problem of detecting moving as well as stationary objects in scenes that contain parallax and shadows. We constrain the search of pedestrians and vehicles by representing them as shadow casting out of plane or (SCOOP) objects.Next, we propose a novel method for tracking a large number of densely moving objects in aerial video. We divide the scene into grid cells to define a set of local scene constraints which we use as part of the matching cost function to solve the tracking problem which allows us to track fast-moving objects in low frame rate videos.Finally, we propose a method for recognizing human actions from few examples. We use the bag of words action representation, assume that most of the classes have many examples, and construct Support Vector Machine models for each class. We then use Support Vector Machines for classes with many examples to improve the decision function of the Support Vector Machine that was trained using few examples via late fusion of weighted decision values.
Show less
Date Issued: 2012
Identifier: CFE0004627, ucf:49935
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004627

Title: On the range of the Attenuated Radon Transform in strictly convex sets.
Creator: Sadiq, Kamran, Tamasan, Alexandru, Nashed, M, Katsevich, Alexander, Dogariu, Aristide, University of Central Florida
Abstract / Description: In the present dissertation, we characterize the range of the attenuated Radon transform of zero, one, and two tensor fields, supported in strictly convex set. The approach is based on a Hilbert transform associated with A-analytic functions of A. Bukhgeim. We first present new necessary and sufficient conditions for a function to be in the range of the attenuated Radon transform of a sufficiently smooth function supported in the convex set. The approach is based on an explicit Hilbert...
Show moreIn the present dissertation, we characterize the range of the attenuated Radon transform of zero, one, and two tensor fields, supported in strictly convex set. The approach is based on a Hilbert transform associated with A-analytic functions of A. Bukhgeim. We first present new necessary and sufficient conditions for a function to be in the range of the attenuated Radon transform of a sufficiently smooth function supported in the convex set. The approach is based on an explicit Hilbert transform associated with traces of the boundary of A-analytic functions in the sense of A. Bukhgeim. We then uses the range characterization of the Radon transform of functions to characterize the range of the attenuated Radon transform of vector fields as they appear in the medical diagnostic techniques of Doppler tomography. As an application we determine necessary and sufficient conditions for the Doppler and X-ray data to be mistaken for each other. We also characterize the range of real symmetric second order tensor field using the range characterization of the Radon transform of zero tensor field.
Show less
Date Issued: 2014
Identifier: CFE0005408, ucf:50437
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005408

Title: Semiconductor Laser Based on Thermoelectrophotonics.
Creator: Liu, Xiaohang, Deppe, Dennis, Vanstryland, Eric, Dogariu, Aristide, Bass, Michael, University of Central Florida
Abstract / Description: This dissertation presents to our knowledge the first demonstration of a quantum well (QW) laser monolithically integrated with internal optical pump based on a light emitting diode (LED). The LED with high efficiency is operated in a thermoelectrophotonic (TEP) regime for which it can absorb both its own emitted light and heat. The LED optical pump can reduce internal optical loss in the QW laser, and enables monolithically integrated TEP heat pumps to the semiconductor laser. The design,...
Show moreThis dissertation presents to our knowledge the first demonstration of a quantum well (QW) laser monolithically integrated with internal optical pump based on a light emitting diode (LED). The LED with high efficiency is operated in a thermoelectrophotonic (TEP) regime for which it can absorb both its own emitted light and heat. The LED optical pump can reduce internal optical loss in the QW laser, and enables monolithically integrated TEP heat pumps to the semiconductor laser. The design, growth and fabrication processes of the laser chip are discussed, and its experimental data is presented. In order to further increase the TEP laser efficiency the development of QDs as the active region for TEP edge emitting laser (EEL) is studied. The usage of QD as TEP laser's active region is significant in terms of its low threshold current density, low internal optical loss and high reliability, which are mainly due to low transparency in QD laser. The crystal growth of self-organized QDs in molecular beam epitaxial (MBE) system and characterization of QDs are mentioned. The design, growth, processing and fabrication of a QD laser structure are detailed. The characteristics of laser devices with different cavity length are reported. QD active regions with different amount of material are grown to improve the active region performance. Theoretical calculations based on material parameters and semiconductor physics indicate that with proper design, the combination of high efficiency LED in TEP regime with a QD laser can result in the integrated laser chip power conversion efficiency exceeding unity.
Show less
Date Issued: 2014
Identifier: CFE0005369, ucf:50477
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005369

Polarization (3)	+ -
coherence (3)	+ -
Coherence (2)	+ -
Optical Sensing (2)	+ -
Optics (2)	+ -

Polarimetry (2)	+ -
Scattering (2)	+ -
Statistical Optics (2)	+ -
Statistical optics (2)	+ -
optical sensing (2)	+ -
optics (2)	+ -
random media (2)	+ -
03/30/2018 (1)	+ -
1-Laplacian (1)	+ -
A-analytic maps (1)	+ -
Atomic Force Microscopy (1)	+ -
Attenuated Doppler transform. (1)	+ -
Attenuated Radon Transform (1)	+ -
Beam Deflection (1)	+ -
CPA (1)	+ -
Coherent Perfect Absorption (1)	+ -
Complete Electrode Model (1)	+ -
Computational Electrodynamics (1)	+ -
Computational Imaging and Sensing (1)	+ -
Current Density Impedance Imaging (1)	+ -
Diffusion (1)	+ -
Electrical Impedance Tomography (1)	+ -
Electromagnetic Forces (1)	+ -
Esophageal cancer (1)	+ -
Fabry-Pérot resonator (1)	+ -

ETD Collection (27)	+ -
Honors Collection (1)	+ -

Dogariu, Aristide (28)	+ -
University of Central Florida (28)	+ -
Abouraddy, Ayman (5)	+ -
Tamasan, Alexandru (5)	+ -
Christodoulides, Demetrios (3)	+ -

Hagan, David (3)	+ -
Kik, Pieter (3)	+ -
Rahman, Talat (3)	+ -
Vanstryland, Eric (3)	+ -
Bass, Michael (2)	+ -
Nashed, M (2)	+ -
Saleh, Bahaa (2)	+ -
Akhlaghi Bouzan, Milad (1)	+ -
Andl, Claudia (1)	+ -
Apostol, Adela (1)	+ -
Atia, George (1)	+ -
Baleine, Erwan (1)	+ -
Batarseh, Issa (1)	+ -
Belfield, Kevin (1)	+ -
Broky, John (1)	+ -
Davis, Kristopher (1)	+ -
Davoudi Nasab, Behnaz (1)	+ -
DeWilde, Yannick (1)	+ -
Deppe, Dennis (1)	+ -
Douglass, Kyle (1)	+ -
Dutkay, Dorin (1)	+ -
Ellis, Jeremy (1)	+ -
Fathpour, Sasan (1)	+ -
Georgiopoulos, Michael (1)	+ -
Glebov, Leonid (1)	+ -

Search In

Pages

Pages

Sort Results By:

Narrow results by:

Topical Subject

Collection

Type of Resource

Language

Creator

Format

Owner