Optics Commons^™

Sargassum In The Florida Keys: Assessment Using High Resolution Remote Sensing, Sarah “Sully” Sullivan

USF Tampa Graduate Theses and Dissertations

Pelagic Sargassum in the Atlantic Ocean, one type of floating macroalgae, has increased in biomass and extent since 2011, bringing environmental, health, and economic issues to coastal communities. The introduction of large quantities of Sargassum to the Florida Keys, a tourism hub renowned for coral reef and marine diversity, poses a potentially devastating threat. Currently, Sargassum mats are widely monitored using medium resolution satellite imagery such as those collected by the Moderate Resolution Imaging Spectroradiometer (MODIS, 1km) and spectral band difference algorithms such as the Alternative Floating Algae Index (AFAI), but the resulting maps lack the detail and nearshore certainty …

Frequency Domain Diffuse Optics Spectroscopies For Quantitative Measurement Of Tissue Optical Properties, Sadhu Moka

USF Tampa Graduate Theses and Dissertations

Tissue oxygen saturation, blood flow and blood volume are physiological bio-markers of tissue health. Diffuse Optical Spectroscopy(DOS) and Diffuse Correlation Spectroscopy (DCS) are two complementary approaches to measure tissue oxygen saturation and blood flow respectively. Quantitative Diffuse Optical Spectroscopy (DOS) uses multi-spectral intensities of near-infrared light that have been modulated at RF frequencies to estimate static tissue optical properties and hence concentrations of oxygenated and de-oxygenated hemoglobin. Diffuse Correlation Spectroscopy estimates tissue dynamics - i.e., blood flow, by measuring temporal intensity auto-correlation function of backscattered light diffusing through the tissue. Conventionally, DCS instruments use coherent light sources with constant intensity. …

Reducing Instrumentation Barriers Of Diffuse Correlation Spectroscopy For Low-Cost Deep Tissue Blood Flow Monitoring, Arindam Biswas

USF Tampa Graduate Theses and Dissertations

Cerebral blood flow (CBF) is a good indicator of brain health as blood carries necessary nutrients, oxygen, and metabolic byproducts. Quantitative blood flow information can be used in several clinical and therapeutic applications such as stroke detection, measuring autoregulation, evaluating brain injury, or determining neuronal activity. Over the past few decades, light-based deep tissue hemodynamic detection modalities have become popular for non-invasive CBF measurements. In particular, noninvasive Diffuse Correlation Spectroscopy (DCS), has become a tool of choice for research and clinical applications due to its depth sensitivity (>1 cm), portability, validity against other technologies such as Magnetic Resonance Imaging …

Finding Signal In The Noise: High-Fidelity, Quantitative, Optical Blood Perfusion Imaging With Interference, Abdul Mohaimen Safi

USF Tampa Graduate Theses and Dissertations

For label-free, non-invasive, wide field-of-view (FOV) imaging/monitoring of blood flow, speckle-based approaches are gaining popularity. However, to obtain quantitative flow information, speckle techniques rely on the multi-exposure scheme which requires complex, bulky, and expensive instrumentation, limiting its application to preclinical studies. This dissertation directly addresses these issues. In the first part of this dissertation, we report a novel single shot synthetic multi-exposure speckle imaging (syMESI) method to synthetically produce multi-exposure images from one short single exposure speckle image using spatial binning/averaging. We demonstrate that syMESI can reimagine conventional hardware based MESI, with low-cost single exposure laser speckle imaging (LSCI) instrumentation. …

Exploring Magneto-Excitons In Bulk And Mono-Layer Semiconductors Using Non-Linear Spectroscopy Techniques, Varun Mapara

USF Tampa Graduate Theses and Dissertations

The research in two-dimensional (2D) materials has evolved from ``traditional" quantum wells based on group III-V and II-VI semiconductors to atomically thin sheets of van der Waals materials such as 2D semiconducting Transition Metal Dichalcogenides (TMDs). These 2D materials remain a stimulating field that continues to introduce new challenges. From both a fundamental physics and technological perspective, magneto-optical spectroscopy has been an essential tool in this research field. TMDs, for example, pose the challenge of characterizing their spin-valley-resolved physics and deriving implications in quantum computation and information research. With the discovery of valley Zeeman effects, the spin-valley physics of TMDs …

Spontaneous Raman Scattering Enhancement With Microcavities And Multipass Resonators For Trace Gas Detection, Juan Sebastian Gomez Velez

USF Tampa Graduate Theses and Dissertations

The continual increase in production and use of chemicals in an ever-growing field of applications naturally brings forth the necessity to accurately and efficiently measure molecular composition. Spontaneous Raman scattering is a reliable technique which can optically identify molecules based on their intrinsic rotational-vibrational energy structure. The Raman emission from a substance can be spectrally analyzed to detect molecular species simultaneously and with isotopic sensitivity using a single laser source. However, even though the process is non-invasive and effective, the rate at which the emission occurs is notoriously low due to a weak scattering cross-section. Therefore, research into the development …

Measuring And Utilizing High-Dimensional Information Of Optical Fields, Ziyi Zhu

USF Tampa Graduate Theses and Dissertations

Currently, many areas of optical techniques including imaging, inspection and communication emphasize the utilization of the high-dimensional information encoded in optical fields. There is also a requirement for novel measurement techniques to extract this high-dimensional information with high-speed and accuracy. We firstly introduce a scan-free direct measurement technique that is capable of simultaneously characterizing the amplitude and phase of a coherent scalar optical field. Our direct measurement approach is constituted of a weak polarization perturbation which is followed by the recording of a polarization-resolving imaging process. The weak perturbation rotates the linear polarization on the spatial frequency domain of the …

Estimating Coastal Water Turbidity Using Viirs Nighttime Measurement, Chih-Wei Huang

USF Tampa Graduate Theses and Dissertations

Coastal water turbidity is a key environmental factor that influences the relative clarity of the water, which therefore reduces sunlight penetration. The comprehensive spatial and temporal coverage of remote sensing allows mapping of water turbidity near the coast. Even in locations where time-consuming and expensive conventional turbidity monitoring programs exist, local technological limitations prevent complete coverage. Traditional optical satellite techniques using the visible band also have limitations in monitoring turbidity due to non-optimal observing conditions such as clouds, sun-glint, and thick aerosols. In this study, in order to complement the daytime satellite measurements, I used the data from Visible Infrared …

Tip-Enhanced Nano-Optical Imaging Of Superacid Treated Bilayer Mos2-Ws2 2d Lateral Heterostructures, Amala Dixit

USF Tampa Graduate Theses and Dissertations

Nanoscale optical characterization of two-dimensional (2D) materials and heterostructures is important for the design of novel optoelectronic flexible nano-devices. Nano-optical photoluminescence (PL) and Raman imaging of bilayer 2D materials has been a challenging problem due to weak signals. The exciton-dominated light emission of two-dimensional (2D) transition metal dichalcogenide (TMDC) materials is affected by the formation of defects and doping states. Previous studies have shown that chemical treatment modifies the defect and doping states of chemical vapor deposition (CVD)-grown monolayers of MoS₂ and WS₂, which provides a promising possibility for engineering the optoelectronic properties of these 2D TMDCs. …

Application Of Metamaterials To Rf Energy Harvesting And Infrared Photodetection, Clayton M. Fowler

USF Tampa Graduate Theses and Dissertations

Techniques for adapting metamaterials for the improvement of RF energy harvesting and infrared photodetection are demonstrated using experimental and computer simulation methods. Two methods for RF energy harvesting are experimentally demonstrated and supported by computer simulation. In the first method, a metamaterial perfect absorber (MPA) is made into a rectenna capable of harvesting RF energy and delivering power to a load by soldering Schottky diodes onto connected split ring resonator (SRR) structures composing the planar metasurface of the perfect absorber. The metamaterial rectenna is accompanied by a ground plane placed parallel to it, which forms a Fabry-Perot cavity between the …

Coherent Response Of Two Dimensional Electron Gas Probed By Two Dimensional Fourier Transform Spectroscopy, Jagannath Paul

USF Tampa Graduate Theses and Dissertations

Advent of ultrashort lasers made it possible to probe various scattering phenomena in materials that occur in a time scale on the order of few femtoseconds to several tens of picoseconds. Nonlinear optical spectroscopy techniques, such as pump-probe, transient four wave mixing (TFWM), etc., are very common to study the carrier dynamics in various material systems. In time domain, the transient FWM uses several ultrashort pulses separated by time delays to obtain the information of dephasing and population relaxation times, which are very important parameters that govern the carrier dynamics of materials. A recently developed multidimensional nonlinear optical spectroscopy is …

Interference Of Light In Multilayer Metasurfaces: Perfect Absorber And Antireflection Coating, Khagendra Prasad Bhattarai

USF Tampa Graduate Theses and Dissertations

We have studied several metamaterials structures with multiple layers by explaining them theoretically and verifying experimentally. The engineered structures we have designed work either as a perfect absorber or antireflection coating. The multilayer model as we call it Three Layer Model (TLM) has been developed, which gives the total reflection and transmission as a function of reflection and transmission of individual layers. By manipulating the amplitude and phase of the reflection and the transmission of the individual layers, we can get the required functionality of the optoelectronic devices. To get zero reflection in the both perfect absorber and the antireflection …

Resonant Light Scattering From Semiconductor Quantum Dots, Kumarasiri Konthasinghe

USF Tampa Graduate Theses and Dissertations

In this work, resonant laser spectroscopy has been utilized in two major projects --resonance fluorescence measurements in solid-state quantum-confined nanostructures and laser-induced fluorescence measurements in gases. The first project focuses on studying resonant light-matter interactions in semiconductor quantum dots "artificial atoms" with potential applications in quantum information science. Of primary interest is the understanding of fundamental processes and how they are affected by the solid-state matrix. Unlike atoms, quantum dots are susceptible to a variety of environmental influences such as phonon scattering and spectral diffusion. These interactions alter the desired properties of the scattered light and hinder uses in certain …

Microcavity Enhanced Raman Scattering, Benjamin James Petrak

USF Tampa Graduate Theses and Dissertations

Raman scattering can accurately identify molecules by their intrinsic vibrational frequencies, but its notoriously weak scattering efficiency for gases presents a major obstacle to its practical application in gas sensing and analysis. This work explores the use of high finesse (50 000) Fabry-Pérot microcavities as a means to enhance Raman scattering from gases. A recently demonstrated laser ablation method, which carves out a micromirror template on fused silica--either on a fiber tip or bulk substrates-- was implemented, characterized, and optimized to fabricate concave micromirror templates ~10 µm diameter and radius of curvature. The fabricated templates were coated with a high-reflectivity …

Nano-Photonic Waveguides For Chemical And Biomedical Sensing, Surya Venkatasekhar Cheemalapati

USF Tampa Graduate Theses and Dissertations

In this dissertation, advances in the fields of Photonics, and Plasmonics, and specifically, single cell analysis and waveguide sensing will be addressed. The first part of the dissertation is on Finite Difference Time Domain (FDTD) optimization and experimental demonstration of a nano-scale instrument that allows sensing at the cellular and subcellular levels. A new design of plasmonic coupler into a nanoscale waveguide is proposed and optimized using FDTD simulations. Following this, a subcellular nanoendoscope that can locally excite fluorescence in labelled cell organelles and collect the emitted fluorescent light for detailed spectrum analysis is fabricated and tested. The nanoendoscope has …

Optical Communication Using Hybrid Micro Electro Mechanical Structures (Mems) And Commercial Corner Cube Retroreflector (Ccr), Sunny Kedia

USF Tampa Graduate Theses and Dissertations

This dissertation presents a free-space, long-range, passive optical communication system that uses electrostatically modulated microelectromechanical systems (MEMS) structures coupled with a glass total internal reflection (TIR)-type corner cube retroreflector (CCR) as a non-emitting data transmitter. A CCR consists of three mirrors orthogonal to each other, so that the incident beam is reflected back to the incident beam, source. The operational concept is to have a MEMS modulator fusion with TIR CCR, such that the modulators are working periodically to disrupt the evanescent waves at the air interface of one of the three back glass faces of a TIR CCR. The …

Dual 7-Degree-Of-Freedom Robotic Arm Remote Teleoperation Using Haptic Devices, Yu-Cheng Wang

USF Tampa Graduate Theses and Dissertations

A teleoperated system of dual redundant manipulator will be controlled in this thesis. The robot used with the dual redundant manipulator in this thesis is Baxter. Baxter’s redundant robot arms are 7-degree-of-freedom arms. The problem that will be solved in this thesis is optimization of the 7-degree-of-freedom robot arms. The control algorithm of the 7-degree-of-freedom robot arms will be discussed and built. A simulation program will be built to test the control algorithm. Based on the control algorithm, a teleoperation system will be created for Baxter. The controller used is Omni, which is a six-joint haptic device. Omni will also …

Coherent Digital Holographic Adaptive Optics, Changgeng Liu

USF Tampa Graduate Theses and Dissertations

A new type of adaptive optics (AO) based on the principles of digital holography (DH) is proposed and developed for the use in wide-field and confocal retinal imaging. Digital holographic adaptive optics (DHAO) dispenses with the wavefront sensor and wavefront corrector of the conventional AO system. DH is an emergent imaging technology that gives direct numerical access to the phase of the optical field, thus allowing precise control and manipulation of the optical field. Incorporation of DH in an ophthalmic imaging system can lead to versatile imaging capabilities at substantially reduced complexity and cost of the instrument. A typical conventional …

Study Of The Motility Of Biological Cells By Digital Holographic Microscopy, Xiao Yu

USF Tampa Graduate Theses and Dissertations

In this dissertation, I utilize digital holographic microscopy (DHM) to study the motility of biological cells. As an important feature of DHM, quantitative phase microscopy by digital holography (DH-QPM) is applied to study the cell-substrate interactions and migratory behavior of adhesive cells. The traction force exerted by biological cells is visualized as distortions in flexible substrata. Motile fibroblasts produce wrinkles when attached to a silicone rubber film. For the non-wrinkling elastic substrate polyacrylamide (PAA), surface deformation due to fibroblast adhesion and motility is visualized as tangential and vertical displacement. This surface deformation and the associated cellular traction forces are measured …

Investigation Of Colored Dissolved Organic Matter (Cdom) Optical Properties, Nutrients, And Salinity In Coastal Florida: Springshed To Estuaries, Ana Rosa Arellano

USF Tampa Graduate Theses and Dissertations

Optical parameters measured via absorption spectroscopy and high-resolution fluorescence spectroscopy were used to characterize dissolved organic matter (DOM) in the springshed of Kings Bay, a spring-fed estuary located on Florida's Springs Coast. Over the past 40 years, springs supplying groundwater to Kings Bay have shown an increase in nitrate concentration. The overall goal of this project was to fingerprint wells and spring sites with elevated nitrogen concentrations using CDOM optical properties and establish relationships between nutrient and optical parameters. Samples were obtained from various sites: springs, Kings Bay surface (KBS), wells, coastal waters in and at the mouth of Crystal …

Digital Holographic Measurement Of Nanometric Optical Excitation On Soft Matter By Optical Pressure And Photothermal Interactions, David C. Clark

USF Tampa Graduate Theses and Dissertations

In this dissertation we use digital holographic quantitative phase microscopy to observe and measure phase-only structures due to induced photothermal interactions and nanoscopic structures produced by photomechanical interactions. Our use of the angular spectrum method combined with off-axis digital holography allows for the successful hologram acquisition and processing necessary to view these phenomena with nanometric and, in many cases, subnanometric precision. We show through applications that this has significance in metrology of bulk fluid and interfacial properties.

Our accurate quantitative phase mapping of the optically induced thermal lens in media leads to improved measurement of the absorption coefficient over existing …

Optical Detection And Classification Of Phytoplankton Taxa Through Spectral Analysis, Daniel Tyler Sensi

USF Tampa Graduate Theses and Dissertations

Phytoplankton serve as the bottom of the marine food web and therefore play an essential role in marine ecosystems. On the other hand, coastal phytoplankton communities can adversely affect the marine ecosystem and humans. A variety of techniques have been developed to measure and study phytoplankton, including in situ methods (e.g., flow cytometry) and laboratory methods (e.g., microscopic taxonomy). These provide accurate measurements of phytoplankton taxa and concentrations, yet they are limited in space and time, and synoptic information is difficult to obtain with these techniques.

Optical remote sensing may provide complementary information for its synoptic nature, as demonstrated by …

Evanescent Wave Coupling Using Different Subwavelength Gratings For A Mems Accelerometer, Al-Aakhir A. Rogers

USF Tampa Graduate Theses and Dissertations

A novel technique of coupling near-field evanescent waves by means of variable period subwavelength gratings (1.2 ìm and 1.0 ìm), using a 1.55 ìm infrared semiconductor laser is presented for the use of an optical MEMS accelerometer. The subwavelength gratings were fabricated on both glass and silicon substrates respectively.

Optical simulation of the subwavelength gratings was carried out to obtain the maximum coupling efficiency of the two subwavelength gratings; the grating thickness, grating width, and the grating separation were optimized. This was performed for both silicon and glass substrates.

The simulations were used to determine the total system noise, including …