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(1 - 9 of 9)
- Title
- POLARIMETRIC CHARACTERIZATION OF RANDOM ELECTROMAGNETIC BEAMS AND APPLICATIONS.
- Creator
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Mujat, Mircea, Dogariu, Aristide, University of Central Florida
- Abstract / Description
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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
- USING LOW-COHERENCE INTERFEROMETRY TO MONITOR CELL INVASION IN AN IN-VITRO MODEL SYSTEM.
- Creator
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Davoudi Nasab, Behnaz, Dogariu, Aristide, Andl, Claudia, University of Central Florida
- Abstract / Description
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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
- SYSTEM DESIGN AND OPTIMIZATION OF OPTICAL COHERENCE TOMOGRAPHY.
- Creator
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Akcay, Avni, Rolland, Jannick, University of Central Florida
- Abstract / Description
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Optical coherence imaging, including tomography (OCT) and microscopy (OCM), has been a growing research field in biomedical optical imaging in the last decade. In this imaging modality, a broadband light source, thus of short temporal coherence length, is used to perform imaging via interferometry. A challenge in optical coherence imaging, as in any imaging system towards biomedical diagnosis, is the quantification of image quality and optimization of the system components, both a primary...
Show moreOptical coherence imaging, including tomography (OCT) and microscopy (OCM), has been a growing research field in biomedical optical imaging in the last decade. In this imaging modality, a broadband light source, thus of short temporal coherence length, is used to perform imaging via interferometry. A challenge in optical coherence imaging, as in any imaging system towards biomedical diagnosis, is the quantification of image quality and optimization of the system components, both a primary focus of this research. We concentrated our efforts on the optimization of the imaging system from two main standpoints: axial point spread function (PSF) and practical steps towards compact low-cost solutions. Up to recently, the criteria for the quality of a system was based on speed of imaging, sensitivity, and particularly axial resolution estimated solely from the full-width at half-maximum (FWHM) of the axial PSF with the common practice of assuming a Gaussian source power spectrum. As part of our work to quantify axial resolution we first brought forth two more metrics unlike FWHM, which accounted for side lobes in the axial PSF caused by irregularities in the shape of the source power spectrum, such as spectral dips. Subsequently, we presented a method where the axial PSF was significantly optimized by suppressing the side lobes occurring because of the irregular shape of the source power spectrum. The optimization was performed through optically shaping the source power spectrum via a programmable spectral shaper, which consequentially led to suppression of spurious structures in the images of a layered specimen. The superiority of the demonstrated approach was in performing reshaping before imaging, thus eliminating the need for post-data acquisition digital signal processing. Importantly, towards the optimization and objective image quality assessment in optical coherence imaging, the impact of source spectral shaping was further analyzed in a task-based assessment method based on statistical decision theory. Two classification tasks, a signal-detection task and a resolution task, were investigated. Results showed that reshaping the source power spectrum was a benefit essentially to the resolution task, as opposed to both the detection and resolution tasks, and the importance of the specimen local variations in index of refraction on the resolution task was demonstrated. Finally, towards the optimization of OCT and OCM for use in clinical settings, we analyzed the detection electronics stage, which is a crucial component of the system that is designed to capture extremely weak interferometric signals in biomedical and biological imaging applications. We designed and tested detection electronics to achieve a compact and low-cost solution for portable imaging units and demonstrated that the design provided an equivalent performance to the commercial lock-in amplifier considering the system sensitivity obtained with both detection schemes.
Show less - Date Issued
- 2005
- Identifier
- CFE0000651, ucf:46527
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000651
- Title
- INTERFEROMETRY-BASED FREE SPACE COMMUNICATION AND INFORMATION PROCESSING.
- Creator
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Arain, Muzamil, Riza, Nabeel, University of Central Florida
- Abstract / Description
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This dissertation studies, analyzes, and experimentally demonstrates the innovative use of interference phenomenon in the field of opto-electronic information processing and optical communications. A number of optical systems using interferometric techniques both in the optical and the electronic domains has been demonstrated in the filed of signal transmission and processing, optical metrology, defense, and physical sensors. Specifically it has been shown that the interference of waves in...
Show moreThis dissertation studies, analyzes, and experimentally demonstrates the innovative use of interference phenomenon in the field of opto-electronic information processing and optical communications. A number of optical systems using interferometric techniques both in the optical and the electronic domains has been demonstrated in the filed of signal transmission and processing, optical metrology, defense, and physical sensors. Specifically it has been shown that the interference of waves in the form of holography can be exploited to realize a novel optical scanner called Code Multiplexed Optical Scanner (C-MOS). The C-MOS features large aperture, wide scan angles, 3-D beam control, no moving parts, and high beam scanning resolution. A C-MOS based free space optical transceiver for bi-directional communication has also been experimentally demonstrated. For high speed, large bandwidth, and high frequency operation, an optically implemented reconfigurable RF transversal filter design is presented that implements wide range of filtering algorithms. A number of techniques using heterodyne interferometry via acousto-optic device for optical path length measurements have been described. Finally, a whole new class of interferometric sensors for optical metrology and sensing applications is presented. A non-traditional interferometric output signal processing scheme has been developed. Applications include, for example, temperature sensors for harsh environments for a wide temperature range from room temperature to 1000 degree C.
Show less - Date Issued
- 2005
- Identifier
- CFE0000598, ucf:46478
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000598
- Title
- SEARCH, CHARACTERIZATION, AND PROPERTIES OF BROWN DWARFS.
- Creator
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Tata, Ramarao, Martin, Eduardo, University of Central Florida
- Abstract / Description
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Brown dwarfs (BD) were mere theoretical astrophysical objects for more than three decades (Kumar (1962)) till their first observational detection in 1995 (Rebolo et al. (1995), Nakajima et al. (1995)). These objects are intermediate in mass between stars and planets. Since their observational discovery these objects have been studied thoroughly and holistically.Various methods for searching and characterizing these objects in different regions of the sky have been put forward and tested with...
Show moreBrown dwarfs (BD) were mere theoretical astrophysical objects for more than three decades (Kumar (1962)) till their first observational detection in 1995 (Rebolo et al. (1995), Nakajima et al. (1995)). These objects are intermediate in mass between stars and planets. Since their observational discovery these objects have been studied thoroughly and holistically.Various methods for searching and characterizing these objects in different regions of the sky have been put forward and tested with great success. Theoretical models describing their physical, atmospheric and chemical processes and properties have been proposed and have been validated with a large number of observational results. The work presented in this dissertation is a compilation of synoptic studies of ultracool dwarfs(UDs. • A search for wide binaries around solar type stars in upper scorpio OB association(Upper Sco) do indicate (the survey is not yet complete) a deficit of BD binaries at these large separations (< 5AU). • Twenty six new UDs were discovered at low galactic latitudes in our survey from archival data and a novel technique using reduced proper motion. • Six field UDs were discovered by spectroscopic follow-up of the candidates selected from a deep survey. • Optical interferometry was used to independently determine the orbit of the companion of HD33636 which was initially determined using Hubble Space Telescope(HST)astrometry and radial velocity found. Some inconsistency in the HST determined orbit and mass. • Optical linear polarization in UDs was used to investigate the dust propertied in their atmospheres. A trend in polarization as predicted by theoretical models was validated, and atmospheric dust grain sizes and projected rotational velocities for these objects were estimated. Comprehensive studies of UDs are proving to be crucial not only in our understanding of UDs but also for star and planet formation as brown dwarfs represent their lower and upper mass boundaries, respectively.
Show less - Date Issued
- 2009
- Identifier
- CFE0002943, ucf:47952
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002943
- Title
- Characteristics of Hydrogel-Wetted Thin Films.
- Creator
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Owens, James, Putnam, Shawn, Chow, Louis, Xu, Yunjun, University of Central Florida
- Abstract / Description
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The meniscus region of a thin film is known to have high heat transfer properties due to high evaporation rates and activation of latent heat. The region known as the thin film meniscus (?_film(
Show moreThe meniscus region of a thin film is known to have high heat transfer properties due to high evaporation rates and activation of latent heat. The region known as the thin film meniscus (?_film(<)2 (&)#181;m ) can account for more than half of the total heat transfer of a droplet or film. This study focuses on the potential elongation and curvature amplification of the thin film meniscus region by the implementation of a layer of high hydrogen bonding (hydrogel) film on which the liquid meniscus is built. Forced wetting via liquid propagation though this hydrogel layer in the radial direction increases the surface area of the film. By analyzing the mass flux of liquid lost through evaporation and using both spectroscopic and optical methods to obtain the curvature of the film, relationships between hydrogel thickness and the resulting mass flux were made. Isothermal and steady state assumptions were used to relate hydrogel thickness layers to meniscus curvature, evaporative mass flux, and overall heat transfer coefficients. The experimental results demonstrate, that steady state conditions are achievable with small percentage change in film profile over time. These results are promising toward the addition of the hydrogel coatings and further advancements in heat piping and high heat flux cooling systems for micro electronic devices.
Show less - Date Issued
- 2017
- Identifier
- CFE0006634, ucf:51257
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006634
- Title
- Plasma Dynamics of Laser Filaments.
- Creator
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Reyes, Danielle, Richardson, Martin, Gaume, Romain, Chini, Michael, University of Central Florida
- Abstract / Description
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Laser filamentation is a complex phenomenon occurring for pulses with peak power above a critical value. A filament is a dynamic self-guided structure characterized by several unique qualities, which include a beam with a high-intensity core surrounded by an energy reservoir, a weakly ionized plasma channel, and supercontinuum generation. Several of the proposed applications for filamentation utilize the plasma channel, such as for assisted electric discharge and microwave guiding. However,...
Show moreLaser filamentation is a complex phenomenon occurring for pulses with peak power above a critical value. A filament is a dynamic self-guided structure characterized by several unique qualities, which include a beam with a high-intensity core surrounded by an energy reservoir, a weakly ionized plasma channel, and supercontinuum generation. Several of the proposed applications for filamentation utilize the plasma channel, such as for assisted electric discharge and microwave guiding. However, filament properties are highly influenced by the physical conditions under which they are formed. A host of studies have been conducted to further characterize filaments, but much work still remains in order to understand their complex behavior. This work presents an accurate and direct measurement of the electron density based on an interferometric technique. The impact of different initial parameters on filament spatio-temporal dynamics in air is investigated, concentrating primarily on their influence on the plasma. For comparison of the experiment with theory, the plasma decay is modeled by a system of kinetic equations that takes into account three-body and dissociative electron recombination reactions.
Show less - Date Issued
- 2017
- Identifier
- CFE0006646, ucf:51222
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006646
- Title
- Implementation of Optical Interferometry and Spectral Reflectometry for High Fidelity Thin Film Measurements.
- Creator
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Arends-Rodriguez, Armando, Putnam, Shawn, Chow, Louis, Kauffman, Jeffrey, University of Central Florida
- Abstract / Description
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An in-house reflectometer/interferometer has been built to investigate the varying curvature and thickness profiles in the contact line region of air, acetone, iso-octane, ethanol, and water on various types of substrates. Light intensity measurements were obtained using our reflectometer/interferomter and then analyzed in MATLAB to produce thickness and curvature profiles. The apparatus is based on the principle of a reflectometer, consisting of different optical elements, probe, light...
Show moreAn in-house reflectometer/interferometer has been built to investigate the varying curvature and thickness profiles in the contact line region of air, acetone, iso-octane, ethanol, and water on various types of substrates. Light intensity measurements were obtained using our reflectometer/interferomter and then analyzed in MATLAB to produce thickness and curvature profiles. The apparatus is based on the principle of a reflectometer, consisting of different optical elements, probe, light source, and spectrometer. Our reflectometer/interferomter takes measurements in the UV-Vis-IR range (200nm-1000nm). This range is achieved by using a light source that has both a deuterium light (190nm-800nm), a tungsten halogen light (400nm-1100nm), a Metal-Core Printed Circuit Board LED (800nm-1000nm) and a Metal-Core Printed Circuit board cold white LED (400nm-800nm, 6500 K). A UV-VIS-IR spectrometer reads the light response after light is focused on the region of interest. Then a CCD camera (2448x2048) records the profiles for image analyzing interferometry. The readings were then validated based on results in the literature and studies with cylindrical lens samples.
Show less - Date Issued
- 2017
- Identifier
- CFE0006559, ucf:51328
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006559
- Title
- A Linear Multiplexed Electrospray Thin Film Deposition System.
- Creator
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Lojewski, Brandon, Deng, Weiwei, Chen, Ruey-Hung, Chen, Quanfang, University of Central Florida
- Abstract / Description
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Liquid spray is essential to industries requiring processes such as spray coating, spray drying, spray pyrolysis, or spray cooling. This thesis reports the design, fabrication, and characterization of a thin film deposition system which utilizes a linear multiplexed electrospray (LINES) atomizer. First, a thorough review of the advantages and limitations of prior multiplexed electrospray systems leads to discussion of the design rationale for this work. Next, the line of charge model was...
Show moreLiquid spray is essential to industries requiring processes such as spray coating, spray drying, spray pyrolysis, or spray cooling. This thesis reports the design, fabrication, and characterization of a thin film deposition system which utilizes a linear multiplexed electrospray (LINES) atomizer. First, a thorough review of the advantages and limitations of prior multiplexed electrospray systems leads to discussion of the design rationale for this work. Next, the line of charge model was extended to prescribe the operating conditions for the experiments and to estimate the spray profile. The spray profile was then simulated using a Lagrangian model and solved using a desktop supercomputer based on Graphics Processing Units (GPUs). The simulation was extended to estimate the droplet number density flux during deposition. Pure ethanol was electrosprayed in the cone-jet mode from a 51-nozzle aluminum LINES atomizer with less than 3% relative standard deviation in the D10 average droplet diameter as characterized using Phase Doppler Interferometry (PDI). Finally a 25-nozzle LINES was integrated into a thin film deposition system with a heated, motion controlled stage, to deposit TiO2 thin films onto silicon wafers from an ethanol based nanoparticle suspension. The resulting deposition pattern was analyzed using SEM, optical profilometry, and macro photography and compared with the numerical simulation results. The LINES tool developed here is a step forward to enabling the power of electrospray for industrial manufacturing applications in clean energy, health care, and electronics.
Show less - Date Issued
- 2013
- Identifier
- CFE0005106, ucf:50745
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005106
