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Articles 1 - 30 of 1930

Full-Text Articles in Physics

Studying Near-Critical And Super-Critical Fluids In Reduced Gravity, Christian Hawkins, Ana Oprisan, Carole Lecoutre-Chabot, Yves Garrabos, Daniel Beysens Aug 2019

Studying Near-Critical And Super-Critical Fluids In Reduced Gravity, Christian Hawkins, Ana Oprisan, Carole Lecoutre-Chabot, Yves Garrabos, Daniel Beysens

Journal of the South Carolina Academy of Science

Critical and supercritical fluids have a variety of applications, from use as machine lubricants in high pressure or high temperature environments to the manufacturing of materials such as aerogel. The optical properties of fluids undergo rapid changes near the critical point resulting in a rapid increase in turbidity known as critical opalescence. These optical changes can be used to probe the universality of critical behavior. As a fluid approaches the critical point, the compressibility rapidly increases. In a gravitational field, this increase in compressibility leads to near-critical fluids stratifying by phase and density, making it difficult to observe the optical ...


Erratum: "Imaging The Three‐Dimensional Orientation And Rotational Mobility Of Fluorescent Emitters Using The Tri‐Spot Point Spread Function", Oumeng Zhang, Jin Lu, Tianben Ding, Matthew D. Lew Aug 2019

Erratum: "Imaging The Three‐Dimensional Orientation And Rotational Mobility Of Fluorescent Emitters Using The Tri‐Spot Point Spread Function", Oumeng Zhang, Jin Lu, Tianben Ding, Matthew D. Lew

Electrical & Systems Engineering Publications and Presentations

In the original paper, a calibration error exists in the image-formation model used to analyze experimental images taken by our microscope, causing a bias in the orientation measurements in Figs. 2 and 3. The updated measurements are shown in Fig. E1. We have also updated the supplementary material for the original article to discuss the revised PSF model and estimation algorithms (supplementary material 2) and show the revised model and measurements (Figs. S1, S3, S7, S8, and S10–S13).


Development Of A Ground-Based Aerial-Tracking Instrument For Open-Path Spectroscopy To Monitor Atmospheric Constituents, Haden Hodges Aug 2019

Development Of A Ground-Based Aerial-Tracking Instrument For Open-Path Spectroscopy To Monitor Atmospheric Constituents, Haden Hodges

Civil Engineering Undergraduate Honors Theses

A ground-based aerial-tracking instrument, known as the Ground Tracker, designed to provide spectral data to quantify greenhouse gases is under development. The Ground Tracker includes an Optical System including a high power rifle scope, video camera, and spectrometer used to locate an active light source from the Emitter, and collect spectral data by utilizing an actuating mirror. The implementation of this instrument could be made low cost by utilizing existing weather balloon infrastructure to allow the Emitter to be placed into the lower stratosphere. The recovery of the emitter will be possible by tracking the GPS coordinates. Weather balloon instrument ...


Possible Schemes For A Single Photon Switch, Hemlin Swaran Rag Aug 2019

Possible Schemes For A Single Photon Switch, Hemlin Swaran Rag

Theses and Dissertations

I consider the effectiveness of a single control photon to route a target photon using two processes: the first one uses the transient excitation of a two-level system and the second one which uses the permanent population transfer in a three-level Λ-system to route the target photon. In the absence of a single control photon and when the system has additional decay channels, I find ways to optimize the success probability of routing with an increasing number of photons in the control field.


A Brief Review Of Modern Uses Of Scattering Techniques, Daniel M. Wade, Dereth J. Drake Jun 2019

A Brief Review Of Modern Uses Of Scattering Techniques, Daniel M. Wade, Dereth J. Drake

Georgia Journal of Science

Thomson, Rayleigh, Mie, and Raman scattering are commonly used in several disciplines in science and engineering. The techniques involve the scattering of electromagnetic radiation or particles in a sample. This paper provides a brief history for each scattering method, describes the traditional laboratory approach for implementation, and discusses current uses and variations of these four techniques.


Lasers, Noah B. Caro Jun 2019

Lasers, Noah B. Caro

Physics

No abstract provided.


Rare Event Sampling In Applied Stochastic Dynamical Systems, Yiming Yu May 2019

Rare Event Sampling In Applied Stochastic Dynamical Systems, Yiming Yu

Dissertations

Predicting rare events is a challenging problem in many complex systems arising in physics, chemistry, biology, and materials science. Simulating rare events is often prohibitive in such systems due to their high dimensionality and the numerical cost of their simulation, yet analytical expressions for rare event probabilities are usually not available. This dissertation tackles the problem of approximation of the probability of rare catastrophic events in optical communication systems and spin-torque magnetic nanodevices. With the application of the geometric minimum action method, the probability of pulse position shifts or other parameter changes in a model of an actively mode-locked laser ...


Nonlinear Optical Studies Of Bulk And Thin Film Complex Materials, Joel E. Taylor May 2019

Nonlinear Optical Studies Of Bulk And Thin Film Complex Materials, Joel E. Taylor

LSU Doctoral Dissertations

Nonlinear optical studies of bulk and thin film materials provide a vast playground for physical and dynamical characterization. In this thesis, we have implemented experimental methods to probe novel phase transitions in single crystals using rotational anisotropic second harmonic generation (RASHG) and carrier dynamics in thin films with time-resolved pump-probe reflectivity. Furthermore, a novel low temperature ultra-high vacuum system coupled to nonlinear optics has been developed to extend lab capabilities. Doping (Bi1-xSbx)2Se3 with antimony, the surface electronic reconstruction near x=80% was identified with RASHG by deviations in the six-fold and three-fold polarization anisotropic ...


The Challenge For Vision Of Fluctuating Real-World Illumination, David H. Foster May 2019

The Challenge For Vision Of Fluctuating Real-World Illumination, David H. Foster

MODVIS Workshop

No abstract provided.


Symmetry And Dopant Diffusion In Inverted Nanopyramid Arrays For Thin Crystalline Silicon Solar Cells, Seok Jun Han May 2019

Symmetry And Dopant Diffusion In Inverted Nanopyramid Arrays For Thin Crystalline Silicon Solar Cells, Seok Jun Han

Chemical and Biological Engineering ETDs

In this dissertation, we enhance the efficiency of thin flexible monocrystalline silicon solar cells by breaking symmetry in light trapping nanostructures and improving homogeneity in dopant concentration profile. These thin cells are potentially less expensive than conventional thick silicon cells by using less silicon material and making the cells more convenient to be handled when supported on polymer films. Moreover, these cells are widely applicable due to their flexibility and lightweight. However, for high efficiencies, these cells require effective light trapping and charge collection. We achieve these in cells based on 14-mm-thick free-standing silicon films with light-trapping arrays of nanopyramidal ...


Photometry Of Star Clusters From Mendel Observatory, James Biegel May 2019

Photometry Of Star Clusters From Mendel Observatory, James Biegel

Across the Bridge: The Merrimack Undergraduate Research Journal

We have observed four open star clusters and three globular star clusters using Mendel Observatory’s 18” Richey-Chrétien telescope. Our photometry data was obtained using nonstandard R, G, and B filters. We plotted the results in the form of a Hertzsprung-Russell (H-R) diagram in an attempt to determine the so called “turn-off point” for the observed clusters, which is a strong indicator of age. Due to our limited sample size of stars in each cluster, we were not able to determine the turn-off points and obtain relative ages for the clusters. However, we find that the shapes of our H-R ...


Large-Scale Atomistic Simulations Of Complex And Functional Properties Of Ferroic Materials, Raymond Thomas Walter May 2019

Large-Scale Atomistic Simulations Of Complex And Functional Properties Of Ferroic Materials, Raymond Thomas Walter

Theses and Dissertations

Ferroelectric (FE) nanostructures have attracted considerable attention as our abilities improve to synthesize them and to predict their properties by theoretical means. Depolarizing field effects at interfaces of FE heterostructures are particularly notable for causing topological defects such as FE vortices and negative dielectric responses in superlattices. In this thesis, I employ two large-scale atomistic techniques, the first-principles-based effective Hamiltonian (HEff) method and the linear-scaling three-dimensional fragment (LS3DF) method. I use these methods to explore optical rotation in FE vortices, electro-optic effects in FE vortices and skyrmions, and voltage amplification via negative capacitance in ferroelectric-paraelectric superlattices. We employ HEff in ...


Plasmonic Properties Of Nanoparticle And Two Dimensional Material Integrated Structure, Desalegn Tadesse Debu May 2019

Plasmonic Properties Of Nanoparticle And Two Dimensional Material Integrated Structure, Desalegn Tadesse Debu

Theses and Dissertations

Recently, various groups have demonstrated nano-scale engineering of nanostructures for optical to infrared wavelength plasmonic applications. Most fabrication technique processes, especially those using noble metals, requires an adhesion layer. Previously proposed theoretical work to support experimental measurement often neglect the effect of the adhesion layers. The first finding of this work focuses on the impact of the adhesion layer on nanoparticle plasmonic properties. Gold nanodisks with a titanium adhesion layer are investigated by calculating the scattering, absorption, and extinction cross-section with numerical simulations using a finite difference time domain (FDTD) method. I demonstrate that a gold nanodisk with an adhesive ...


Generation And Use Of Femtosecond, Gigawatt, Near Infrared Laser Pulses From An Amplified, Mode-Locked, Ti:Sapphire Laser, David Anthony Valdés May 2019

Generation And Use Of Femtosecond, Gigawatt, Near Infrared Laser Pulses From An Amplified, Mode-Locked, Ti:Sapphire Laser, David Anthony Valdés

Optical Science and Engineering ETDs

This work modeled the early to middle successes achieved in the field of ultrafast, high peak power optics, beginning with the work of Nobel Prize winners Donna Strickland and Gérard Mourou in 1985. In our work, 100 fs light pulses of around 800 nm were generated by a Ti:Sapphire oscillator, then amplified to approximately 30 GW peak power using a chirped pulse amplification system that included regenerative and multi-pass amplifiers. As a verification of our pulses having high peak powers and ultrashort durations, they were then used to strike water, glass, and a Kerr Cell. Supercontinuum generation was observed ...


Design, Fabrication, And Characterization Of Multilayer Hyperbolic Metamaterials, James Dilts May 2019

Design, Fabrication, And Characterization Of Multilayer Hyperbolic Metamaterials, James Dilts

Graduate Theses - Physics and Optical Engineering

Hyperbolic metamaterials (HMMs) show extreme anisotropy, acting as metals and dielectrics along orthogonal directions. They are designed using the effective medium theory (EMT) and can be fabricated using standard semiconductor processing techniques. Current techniques used to characterize the optical behavior of HMMs have a high complexity or are unable to robustly determine the complex permittivity tensor. We describe the details of a procedure to obtain a very low mean-squared-error (MSE) for extraction of permittivity from hyperbolic metamaterials using spectroscopic ellipsometry. We have verified our procedure by fabricating three different samples of various materials and fill factors designed to have a ...


Optical Response Analysis Of Thz Photoconductive Antenna Using Comsol Multiphysics, Jose Isaac Santos Batista May 2019

Optical Response Analysis Of Thz Photoconductive Antenna Using Comsol Multiphysics, Jose Isaac Santos Batista

Electrical Engineering Undergraduate Honors Theses

A THz photoconductive antenna consists of antenna pads laid over a photoconductive substrate. These types of antennas are excited through the application of an optical pump (laser), which generates carriers inside the semiconductor. The acceleration and recombination of these carriers produce photocurrent that excites the antenna and generates THz pulse. This thesis focuses on analyzing the optical response of a photoconductive antenna, which consist of the interaction of the incident electric field of a laser pump with the radiating device. It develops the amplitude modulation process of a plane wave of light into a laser pump. It also takes into ...


Construction Of A Hyperspectral Camera Using Off-The-Shelf Parts And 3d-Printed Parts, Connor Heo May 2019

Construction Of A Hyperspectral Camera Using Off-The-Shelf Parts And 3d-Printed Parts, Connor Heo

Mechanical Engineering Undergraduate Honors Theses

The Arkansas Center for Space and Planetary Sciences (ACSPS) is working together with the Mechanical Engineering Department to build a modifiable camera with 3D-printed parts and off-the-shelf parts (sourced from Edmund Optics and Amazon). The design is to be readily changeable, primarily with the 3D printed parts, as to accommodate new ideas and functionalities in the future. Ultimately, the camera should be relatively cheap while maintaining functionality for proposed use cases. Earlier versions of the design will be tested extensively and rapidly updated in the ACSPS labs with benchtop testing. This will involve subjects with both visible and infrared emissions ...


Modeling And Characterization Of A Ring-Resonator Based Silicon Photonic Sensor On Silicon-On-Insulator (Soi), Gwangho Choi May 2019

Modeling And Characterization Of A Ring-Resonator Based Silicon Photonic Sensor On Silicon-On-Insulator (Soi), Gwangho Choi

Graduate Theses - Physics and Optical Engineering

The purpose of this work is to build silicon photonic devices and verify their functionalities. In particular, the structure of a ring resonator (RR) is analyzed and applied to various silicon photonic application in sensing. Silicon waveguides, grating couplers, directional couplers, and RRs are fabricated on the silicon-on-insulator (SOI) wafer. Geometrical parameters and optical properties of the silicon devices are studied and also applied to the design of the aforementioned devices. The waveguide dimensions and, optical properties of the silicon waveguide such as dispersion and effective-index are examined. The RRs are made of a series of straight and bent waveguides ...


Optical Enhancement In Periodic Plasmonic Gratings For Sers And Metal-Semiconductor-Metal Photodetectors (Msm-Pds) Applications, Ahmad Aziz Darweesh May 2019

Optical Enhancement In Periodic Plasmonic Gratings For Sers And Metal-Semiconductor-Metal Photodetectors (Msm-Pds) Applications, Ahmad Aziz Darweesh

Theses and Dissertations

This dissertation is aimed to numerically study the effect of plasmonic grating electrodes on the efficiency of metal-semiconductor-metal photodetectors (MSM PDs) and the sensitivity of Surface Enhanced Raman Spectroscopy (SERS). This research can benefit many areas of nanoscience and optics, including plasmonic applications, such as, super lenses, nano-scale optical circuits, optical filters, surface plasmon enhanced photo-detectors solar cells, imaging sensors, charge-coupled devices (CCD), and optical-fiber communication systems. Several parameters, wire widths and thickness, gap space, taper angle, and the incident wavelength and angle, were investigated. The goal of this research is to utilize the plasmonic phenomenon by using plasmonic gratings ...


Perturbative Generalization Of Nonparaxial Ultrashort Tightly-Focused Elegant Laguerre-Gaussian Beams, Andrew M. Vikartofsky Apr 2019

Perturbative Generalization Of Nonparaxial Ultrashort Tightly-Focused Elegant Laguerre-Gaussian Beams, Andrew M. Vikartofsky

Theses, Dissertations, and Student Research: Department of Physics and Astronomy

An analytical method for calculating the electromagnetic fields of a nonparaxial elegant Laguerre-Gaussian (eLG) vortex beam is presented for arbitrary pulse duration, spot size, and LG mode. This perturbative approach provides a numerically tractable model for the calculation of arbitrarily high radial and azimuthal LG modes in the nonparaxial regime, without requiring integral representations of the fields. A key feature of this perturbative model is its use of a Poisson-like frequency spectrum, which allows for the proper description of pulses of arbitrarily short duration. The time-domain representation of this model is presented as a non-recursive closed-form expression to any order ...


Investigating The Talbot Effect In Arrays Of Optical Dipole Traps For Neutral Atom Quantum Computing, Sergio Aguayo Apr 2019

Investigating The Talbot Effect In Arrays Of Optical Dipole Traps For Neutral Atom Quantum Computing, Sergio Aguayo

Physics

Quantum computers are devices that are able to perform calculations not achievable for classical computers. Although there are many methods for creating a quantum computer, using neutral atoms offers the advantage of being stable when compared to other methods. The purpose of this investigation is to explore possible optical dipole trap configurations that would be useful for implementing a quantum computer with neutral atoms. Specifically, we computationally investigate arrays of pinholes, the diffraction pattern generated by them, and the onset of the Talbot effect in these traps. We manipulate the radius of the pinholes, the number of pinholes in the ...


Second-Harmonic Generation From Hyperbolic Plasmonic Nanorod Metamaterial Slab, Gregory Wurtz Mar 2019

Second-Harmonic Generation From Hyperbolic Plasmonic Nanorod Metamaterial Slab, Gregory Wurtz

Showcase of Faculty Scholarly & Creative Activity

Hyperbolic plasmonic metamaterials provide numerous opportunities for designing unusual linear and nonlinear optical properties. In this work, second-harmonic generation in a hyperbolic metamaterial due to a free-electron nonlinear response of a plasmonic component of the metamaterial is studied. It is shown that owing to a rich modal structure of an anisotropic plasmonic metamaterial slab, the overlap of fundamental and second-harmonic modes results in the broadband enhancement of radiated second-harmonic intensity by up to 2 orders of magnitude for TM- and TE-polarized fundamental light, compared to a smooth Au film under TM-polarised illumination. Compared to the radiated second-harmonic intensity from a ...


Designing Liquid Crystal For Optoacoustic Detection, Michael T. Dela Cruz Mar 2019

Designing Liquid Crystal For Optoacoustic Detection, Michael T. Dela Cruz

Theses and Dissertations

This research impacts the development of a cost-saving, on-chip device that can replace a wide range of costly, bulky sensors for commercial and defense applications. In particular, the goals of this work were to design and test a sensor that uses the optical properties of liquid crystal (LC) to detect acoustic waves. This began with developing a method to fine-tune the optical features of the liquid crystal. Statistical analysis of select experimental variables, or factors, lead to ideal settings of those variables when creating the sensor. A two-factor and three-factor experiment were separately conducted and analyzed as a preliminary demonstration ...


The Non-Mechanical Beam Steering Of Light In Reflective Inverse Diffusion, Eric K. Nagamine Mar 2019

The Non-Mechanical Beam Steering Of Light In Reflective Inverse Diffusion, Eric K. Nagamine

Theses and Dissertations

Wavefront shaping is a technique that uses spatial light modulators to conjugate the phase of light incident on a rough surface, such that the light will refocus after reflection. This refocusing effect is called reflective inverse diffusion. There currently are two different approaches used to achieve reflective inverse diffusion: iterative methods and matrix methods. Iterative methods find one phase mask which allows for reflected light to be focused at a single, specific position, with results that are immediately available and continuously improving. Matrix methods calculate the complex matrix which describes the rough surface and allows for reflected light to be ...


Scaling Film Cooling Adiabatic Effectiveness With Mass Transfer And Thermal Experimental Techniques, Luke J. Mcnamara Mar 2019

Scaling Film Cooling Adiabatic Effectiveness With Mass Transfer And Thermal Experimental Techniques, Luke J. Mcnamara

Theses and Dissertations

With increasing engine temperatures, it is becoming more important to design effective film cooling schemes. Low temperature, large scale tests are often implemented in the design process to reduce cost and complexity. A nondimensional adiabatic effectiveness can be used as an indication of the performance of a film cooling scheme. However, the coolant flow rate must be properly scaled between the low temperature tests and engine temperatures to accurately predict film cooling effectiveness. This process is complicated by gas property variation with temperature. Tests are commonly conducted using thermal measurement techniques with infrared thermography (IR), but the use of pressure ...


Generation Of Broadband Thz Pulses By Laser Wakefield At Radial Boundary Of Plasma Column, Serge Y. Kalmykov, Alexander Englesbe, Jennifer Elle, Andreas Schmitt-Sody Mar 2019

Generation Of Broadband Thz Pulses By Laser Wakefield At Radial Boundary Of Plasma Column, Serge Y. Kalmykov, Alexander Englesbe, Jennifer Elle, Andreas Schmitt-Sody

Serge Youri Kalmykov

Photoionization of an ambient gas by a tightly focused, femtosecond, weakly relativistic laser pulse leaves behind
the pulse a column of electron density (a “filament”). At the column surface, the density drops to zero within a thin (micronscale) boundary layer. Ponderomotive force of the pulse drives within the filament a cylindrical wave of charge separation (laser wake). If the pulse waist size is much smaller than the Langmuir wavelength, electron current in the wake is mostly transverse. In the filament surface area, this current rapidly decays (electrons, crossing the sharp density gradient, phase out of wake within a few Langmuir ...


Fundamental Limits Of Measuring Single-Molecule Rotational Mobility, Oumeng Zhang, Matthew D. Lew Feb 2019

Fundamental Limits Of Measuring Single-Molecule Rotational Mobility, Oumeng Zhang, Matthew D. Lew

Electrical & Systems Engineering Publications and Presentations

Various methods exist for measuring molecular orientation, thereby providing insight into biochemical activities at nanoscale. Since fluorescence intensity and not electric field is detected, these methods are limited to measuring even-order moments of molecular orientation. However, any measurement noise, for example photon shot noise, will result in nonzero measurements of any of these even-order moments, thereby causing rotationally-free molecules to appear to be partially constrained. Here, we build a model to quantify measurement errors in rotational mobility. Our theoretical framework enables scientists to choose the optimal single-molecule orientation measurement technique for any desired measurement accuracy and photon budget.


Control Of Light-Matter Interactions Via Nanostructured Photonic Materials, Nicholas Proscia Feb 2019

Control Of Light-Matter Interactions Via Nanostructured Photonic Materials, Nicholas Proscia

All Dissertations, Theses, and Capstone Projects

The thesis here investigates the manipulation of light-matter interactions via nanoscale engineering of material systems. When material systems are structured on the nanoscale, their optical responses can be dramatically altered. In this thesis, this is done in two primary ways: One method is by changing the geometry of nanostructures to induce a resonant behavior with incident electromagnetic field of optical wavelengths. This allows field enhancement in highly localized areas to strengthen exotic light-matter interactions that would otherwise be too weak to measure or for practical use. In this regard, the work presented here studies a voltage produced in a metal ...


Hybrid Optical Integrator Based On Silicon-On-Insulator Platform, Taewon Huh Jan 2019

Hybrid Optical Integrator Based On Silicon-On-Insulator Platform, Taewon Huh

Graduate Theses - Physics and Optical Engineering

A hybrid optical integrator is a recirculating loop that performs oversampling typically for analog input, using the cross-gain modulation (XGM) in a semiconductor optical amplifier (SOA). The modulated input signal changes the gain of the loop through XGM and thus modifies the loop accumulation. This thesis presents hybrid optical integrator for an all-optical analog-to-digital converter based on a silicon photonics platform. The device consists of silicon waveguides of dimension 220 × 500 nm (thick × width) and approximately 5 m optical loop length including fiber length, input and output grating couplers for 1550 nm signal, directional couplers, and external components (SOA, optical ...


Direct Optically Driven Spin-Charge Dynamics Govern The Femtosecond Response Of Ferromagnets, Phoebe Marie Tengdin Jan 2019

Direct Optically Driven Spin-Charge Dynamics Govern The Femtosecond Response Of Ferromagnets, Phoebe Marie Tengdin

Electrical Engineering Graduate Theses & Dissertations

Ferromagnetic materials have strong electron correlations that drive quantum effects and make the physics that describes them extremely challenging. In particular, the electron, spin, and lattice degrees of freedom can interact in surprising ways when driven out of equilibrium by ultrafast laser excitation. In this thesis I uncover several previously unexpected connections between the electronic and spin systems in ferromagnets. Dynamics occur at unexpectedly fast timescales, driven using femtosecond laser excitation pulses. The tools that I use to observe the exceeding fast (10s of femtosecond) dynamics are bursts of extreme ultraviolet light resonant with the M-edge of transition metals and ...