Optics Commons^™

Hot-Carrier Dynamics And Transport Mechanisms In Inas/Alassb Multiple Quantum Wells, Herath Pathiranage Janaka Chathuranga Piyathilaka

Graduate Theses, Dissertations, and Problem Reports (ETD)

Semiconductor photovoltaics convert light into electricity through the extraction of photo-excited charge carriers. Among the most important parameters for a photovoltaic cell are good optical absorption in the desired region of the electromagnetic spectrum, and sufficient excited-state lifetimes and mobilities of the photocarriers to allow for charge separation and extraction before recombination. For solar cell applications there are significant challenges to overcome to improve the efficiency of the light-to-electricity conversion. The cells are most commonly made of silicon, which has a nearly perfect bandgap for absorbing the most solar radiation, an indirect bandgap to give a long photocarrier lifetime and …

Characterization And Coherent Spin Selective Manipulation Of Quantum Dot Energy Levels, Tristan Anthony Wilkinson

Graduate Theses, Dissertations, and Problem Reports (ETD)

Semiconductor quantum dots (QDs) are promising candidates to fulfill a wide range of applications in real-world quantum computing, communication, and networks. Their excellent optical properties such as high brightness, single-photon purity, and narrow linewidths show potential utility in many areas. In order to realize long term goals of integration into complex and scalable quantum information systems, many current challenges must be overcome. One of these challenges is accomplishment of all necessary computing operations within a QD, which might be enabled by coherent manipulation of single QD energy level structures. In the realm of scalability for quantum devices, a way to …

Charge Dynamics Of Inas Quantum Dots Under Resonant And Above-Band Excitation, Gary R. Lander Jr

Graduate Theses, Dissertations, and Problem Reports (ETD)

Research involving light-matter interactions in semiconductor nanostructures has been an interesting topic of investigation for decades. Many systems have been studied for not only probing fundamental physics of the solid state, but also for direct development of technological advancements. Research regarding self-assembled, epitaxially grown quantum dots (QDs) has proven to be prominent in both regards. The development of a reliable, robust source for the production of quantum bits to be utilized in quantum information protocols is a leading venture in the world of condensed matter and solid-state physics. Fluorescence from resonantly driven QDs is a promising candidate for the production …

Ultrafast Magnetic Entropy Dynamics With Time-Resolved Pump-Probe Magneto-Optical Technique., Sahar Goharshenasanesfahani

Electronic Theses and Dissertations

It has been observed that ultrathin films, multilayers, or magnetic nanostructures indicate novel magnetic phenomena that differ profoundly from the respective bulk properties. Besides, because of the broad applications of these magnetic materials in the industry, they are an exciting research area. Hence, investigating the low-dimensional magnetic systems is one of the most active fields in experimental condensed matter physics. Magnetization dynamics can occur over a wide range of time scales (from seconds to femtoseconds). Some of these processes even occur on time scales as short as a few picoseconds (10^-12s) or femtoseconds (10^-15s). Measurement of …

Two-Dimensional Black Phosphorus For Terahertz Emission And Near-Field Radiative Heat Transfer, Mahmudul Hasan Doha

Graduate Theses and Dissertations

The main focus of this work is to investigate two potential optical and optoelectronic applications of black phosphorus (BP): the near-field radiative heat transfer in plasmonic heterostructures with graphene and terahertz emission from multi-layer BP photoconductive antennas. When the separation distance between graphene-black phosphorene is much smaller than or comparable to the thermal wavelength at different temperatures, a near-field radiation heat transfer breaks the Planck blackbody limit. The magnitude of the near-field radiation enhancement acutely depends on the gate voltage, doping, and vacuum gap of the graphene and BP pair. The strong near-field radiation heat transfer enhancement of the specific …

Gaas Growth On Sapphire Substrates (C And R Plane) For Integrated Microwave Photonics (Imwp), Samir Kumar Saha

Graduate Theses and Dissertations

The microwave signal processing in the optical domain creates new opportunities for information and communication technology (ICT) and networks by increasing speed, bandwidth, and processing capability. IMWP incorporates the functions of microwave photonics components/subsystems in monolithic or hybrid photonic circuits to meet future needs. Sapphire platforms have the potential to integrate all-in-one, for instance, light source, analog signal processing, light detection, CMOS control circuit, silicon on sapphire to achieve high-performance, low-cost mixed-signal optical links etc. Molecular beam epitaxy (MBE) has been used to grow GaAs on sapphire substrates to integrate optoelectronic devices in the same platform.

The initial stage of …

Wave Excitation And Dynamics In Disordered Systems, Yiming Huang

Dissertations, Theses, and Capstone Projects

This thesis presents studies of the field and energy excited in disordered systems as well as the dynamics of scattering.

Dynamic and steady state aspects of wave propagation are deeply connected in lossless open systems in which the scattering matrix is unitary. There is then an equivalence among the energy excited within the medium through all channels, the Wigner time delay, which is the sum of dwell times in all channels coupled to the medium, and the density of states. But these equivalences fall away in the presence of material loss or gain. In this paper, we use microwave measurements, …

Nonlinear Optical Studies Of Interfacial Ferroelectricity And Strain Distribution In Perovskite Dielectric Films, Tony Le

Dissertations, Theses, and Capstone Projects

Dielectric and ferroelectric perovskite films have been model energy storage structures for their low-dielectric loss, extremely high charge-discharge speed, and good temperature stability, yet there is still much to understand about the material’s limitations. This dissertation presents a detailed understanding of the strain-induced ferroelectricity at the boundary between a strontium titanate (SrTiO₃) ultrathin film epitaxially grown on a germanium (Ge) substrate through optical second harmonic generation (SHG), and the polydomain distribution in the Zr-doped BaTiO₃ (BZT) films by time-resolved pump-probe spectroscopy.

First, SHG measurements were performed to reveal interfacial ferroelectricity in the epitaxial SrTiO₃/Ge (100) …

Linear And Non Linear Properties Of Two-Dimensional Exciton-Polaritons, Mandeep Khatoniar

Dissertations, Theses, and Capstone Projects

Technology has been accelerating at breakneck speed since the first quantum revolution, an era that ushered transistors and lasers in the late 1940s and early 1960s. Both of these technologies relied on a matured understanding of quantum theories and since their inception has propelled innovation and development in various sectors like communications, metrology, and sensing. Optical technologies were thought to be the game changers in terms of logic and computing operations, with the elevator pitch being "computing at speed of light", a fundamental speed limit imposed by this universe’s legal system (a.k.a physics). However, it was soon realized that that …

Topological Classical Wave Systems With Modulations, Interactions, And Higher-Order Topological States, Mengyao Li

Dissertations, Theses, and Capstone Projects

Topological phases in classical wave systems, such as photonic and acoustic, have been actively investigated and applied for wave guiding, lasing, and numerous other novel phenomena and device applications Topological phase transitions enable robust boundary states, and the field has been broadening recently into a vast variety of systems with temporal modulations and interactions. Floquet modulation, for example, is the modulation applied periodically in time which may break symmetries and leads to novel topological phases.

Introducing non-Hermitian Floquet modulation enables more interesting phenomena including bandgap in imaginary part of the spectrum and gainy/lossy topological edge states with complex energy values. …

Photoluminescence Spectra Of Silicon Doped With Cadmium, N A. Sultanov, E T. Rakhimov, Z Mirzajonov, F T. Yusupov

Scientific-technical journal

Cadmium and zinc, as transition metals, are deep-level impurities (DL) and have a significant effect on the electrical, photoelectric, recombination, and other properties of semiconductor crystals.This paper presents the results of experimental studies of the optical and electrical properties of silicon crystals containing impurity atoms of cadmium and zinc using DLTS and low-temperature photoluminescence (PL).

Influence Of Mechanical Deformation On The Photo-Voltaic Properties Of Thin Polycrystalline Cdte, Cdse, Cds Films Manufactured By Portional Evaporation In Vacuum, T I. Rakhmonov, R U. Siddikov, A Mirzaaxmedov

Scientific-technical journal

Some issues of improving the technology of obtaining thin-film (d»1.0 μm) elements with anomalous photovoltaic properties from cadmium chalcogenides by thermal evaporation in vacuum in separate portions on transparent dielectric substrates are considered. The experimental results of studying the current-voltage, lux-ampere, lux-voltage and deformation characteristics of CdTe, CdSe, CdS polycrystalline films are analyzed. It is shown that the obtained samples have linear I - V, L - A, temperature (T≈120-320 K) and deformation characteristics (ε≈-3‧10^-5-3‧10^-3 arb. units). Therefore, they can serve as promising photocells for the producing of film photodetectors sensitive to mechanical deformation in the visible …

Plasmonic Waveguides To Enhance Quantum Electrodynamic Phenomena At The Nanoscale, Ying Li, Christos Argyropoulos

Department of Electrical and Computer Engineering: Faculty Publications

The emerging field of plasmonics can lead to enhanced light-matter interactions at extremely nanoscale regions. Plasmonic (metallic) devices promise to efficiently control both classical and quantum properties of light. Plasmonic waveguides are usually used to excite confined electromagnetic modes at the nanoscale that can strongly interact with matter. The analysis of these nanowaveguides exhibits similarities with their low frequency microwave counterparts. In this article, we review ways to study plasmonic nanostructures coupled to quantum optical emitters from a classical electromagnetic perspective. These quantum emitters are mainly used to generate single-photon quantum light that can be employed as a quantum bit …

Interactions Of Organic Fluorophores With Plasmonic Surface Lattice Resonances, Robert J. Collison

Dissertations, Theses, and Capstone Projects

It is common knowledge that metals, alloys and pure elements alike, are lustrous and reflective, the more so when a metal surface is flat, polished, and free from oxidation and surface fouling. However, some metals reflect visible light, in the 380 nm to 740 nm range of wavelengths, much more strongly than others. In particular, some metals reflect wavelengths in certain portions of the ultraviolet (UV), visible, and near-infrared (NIR) regime, let us say 200 nm to 2000 nm, while absorbing light strongly in other segments of this range. There are several factors that account for this difference between various …

Emulating Condensed Matter Systems In Classical Wave Metamaterials, Matthew Weiner

Dissertations, Theses, and Capstone Projects

One of the best tools we have for the edification of physics is the analogy. When we take our classical set of states and dynamical variables in phase space and treat them as vectors and Hermitian operators respectively in Hilbert space through the canonical quantization, we lose out on a lot of the intuition developed with the previous classical physics. With classical physics, through our own experiences and understanding of how systems should behave, we create easy-to-understand analogies: we compare the Bohr model of the atom to the motion of the planets, we compare electrical circuits to the flow of …

Control Of Molecular Energetics And Transport Via Strong Light-Matter Interaction, Rong Wu

Dissertations, Theses, and Capstone Projects

Strong light-matter coupling in excitonic systems results in the formation of half-light half-matter quasiparticles called exciton polaritons. These hybrid quasiparticles take on the best of both systems, namely, the long-range propagation and coherence arising from the photonic component and the nonlinear interaction from the excitonic component. We develop methods for making high quality factor cavities and investigate the potential applications of these strongly coupled states arising specifically in organic molecular systems.

In the first project we investigate the potential of organic dye molecules to undergo condensation in an optical cavity at room temperature. The second study involves the use of …

Free Charge Carrier Properties In Two-Dimensional Materials And Monoclinic Oxides Studied By Optical Hall Effect, Sean Knight

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

In this dissertation, optical Hall effect (OHE) measurements are used to determine the free charge carrier properties of important two-dimensional materials and monoclinic oxides. Two-dimensional material systems have proven useful in high-frequency electronic devices due to their unique properties, such as high mobility, which arise from their two-dimensional nature. Monoclinic oxides exhibit many desirable characteristics, for example low-crystal symmetry which could lead to anisotropic carrier properties. Here, single-crystal monoclinic gallium oxide, an AlInN/GaN-based high-electron-mobility transistor (HEMT) structure, and epitaxial graphene are studied as examples. To characterize these material systems, the OHE measurement technique is employed. The OHE is a physical …

Investigation Of Complex Refractive Index Of Grad Phene Oxide Using Polarisation Response Of Graphene Oxide-Coated Planarizeoptical Waveguide, Soon Xin Gan

Student Works (2020-2029)

Since a single atomic layer of carbon, also as known as graphene is being successfully exfoliated from 3D graphite, intense research on graphene and its derivative begins. Among them, graphene oxide (GO) is considered one of the most prominent candidates in the category of graphene derivatives for the application of electronic, optoelectronic and photonics. However, although GO has been applied in many applications like saturable absorbers of Q-switch laser and optical limiters for eye protection, its intrinsic optical properties especially complex refractive index reported so far still has a large deviation. Also, most of the optical characterization research on GO …

Development Of Co2 Laser-Heating For The Study Of Wide Band Gap Oxide Materials, Christian Matthew Childs

UNLV Theses, Dissertations, Professional Papers, and Capstones

The ability to access a vast region of the pressure-temperature landscape using energy density tuning enables exotic states of matter to be probed. A well documented method for such exploration, under static conditions, is the use of the laser-heated diamond anvil cell (LH-DAC), accessing a combination of high pressure (>300 GPa) and high temperature (>5000 K). This thesis presents our development of direct CO2 laser heating techniques to study a series of wide band gap insulators, La2Sn2O7, ZrO2, and CeO2, under high pressure conditions. The lasing frequency of CO2 lasers is such that these wide band gap materials …

Mid-Ir Optical Refrigeration And Radiation Balanced Lasers, Saeid Rostami

Optical Science and Engineering ETDs

This dissertation reports recent advances in mid-infrared (mid-IR) optical refrigeration and Radiation Balanced Lasers (RBLs). The first demonstration of optical refrigeration in Ho:YLF and Tm:YLF crystals as promising mid-IR laser cooling candidates is reported. Room temperature laser cooling efficiency of Tm- and Ho-doped crystals at different excitation polarization is measured and their external quantum efficiency and background absorption are extracted. Complete characterization of laser cooling samples is obtained via performing detailed low-temperature spectroscopic analysis, and their minimum achievable temperature as well as conditions to achieve laser cooling efficiency enhancement in mid-IR are investigated. By developing a Thulium-doped fiber amplifier, seeded …

Validation Of Trap Density Theory In Single Layer Organic Light Emitting Diodes With Tris(8 Hydroxyquinolinato)Aluminium As The Emissive Material, Zaini Mohd Suffian

Student Works (2020-2029)

Organic light-emitting diodes (OLEDs) rapidly evolving as the future of solid-state lighting and display application due to its numerous advantages and features. However, the efficiency, lifetime, and fabrication method still need to be improved. Even in solving efficiency issues in the device, there are many challenges to be addressed and overcome. In theory, charge transport phenomena contribute greatly towards increasing or improving the device efficiency. The magnitude of carrier mobility determines the performance of the device, as it influenced device efficiency. For organic semiconductor such as OLED, space-charge limited current (SCLC) theory was used to determine the mobility of the …

Electrodynamics Modeling Of Plasmonic-Organic Hybrid Waveguides, Marcus Michel

Pomona Senior Theses

Optical fibers have multiple advantages over conventional electrical connections, such as lower energy losses and higher bandwidth. To use optics for chip-to-chip communication, electro-optic (EO) modulators need to be scaled down to be incorporated on integrated circuits. This size reduction has been accomplished using plasmonic-organic hybrid (POH) waveguides, which make use of nonlinear organic EO materials and surface plasmon polaritons to achieve light modulation in devices with lengths on the micron scale. As these devices are just starting to be developed, there are many avenues for their potential optimization. In order to streamline and reduce the cost of the optimization …

Vanadyl Tetrabutyltetrakis(Dimethylamino) Phthalocyanine Based Thin Films For Organic Sensor And Transistor Applications, Nur Adilah Roslan

Student Works (2020-2029)

Organic electronic devices have been successively making progress into the commercial market to substitute conventional inorganic electronic devices. The endeavor to improve the performance displayed by organic semiconductor materials has urged a substantial number of researchers set to seek new materials. Metal phthalocyanines (MPcs), in particular, have garnered much attention due to their enticing benefits viz., cost efficiency, eco-friendly organic material, as well as thermal and chemical stability. Primarily, this study investigated the physical, morphological, optical, and electrical properties of vanadyl 3,10,17,24-tetra-tert-butyl-1,8,15,22-tetrakis(dimethylamino)-29H,31H-phthalocyanine or synonymously known as vanadyl tetrabutyltetrakis (dimethylamino) phthalocyanine (VTP). Subsequently, this study looked into the potential applications of …

Ultrafast Optical Properties Of La0.7sr0.3mno3 Thin Films, Saeed Yousefi Sarraf

Graduate Theses, Dissertations, and Problem Reports (ETD)

Thin film solids often exhibit different physical properties in the ultra-thin regime. Enhancement of surface to bulk ratio results in the domination of surface/interface related phenomena such as surface recombination. Moreover, in the ultra-thin regime, quantum size and quantum confinement effects can alter the band gap of the system and constrain the strain wave propagation in the thin film. Ultrafast properties of solids can also be drastically altered in the ultra-thin regime due to the aforementioned phenomena. Experimentally, observation of these phenomena is challenging due to the insufficient material to absorb and interact with the electromagnetic wave. This dissertation addresses …

Exciton Polaritons In Two-Dimensional Transition Metal Dichalcogenides, Jie Gu

Dissertations, Theses, and Capstone Projects

Strong interaction between photons and excitons in semiconductors results in the formation of half-light half-matter quasiparticles termed exciton-polaritons. Owing to their hybrid character, they inherit the strong interparticle interaction from their excitonic (matter) component via Coulomb interaction while the photonic component lends the small mass (~10⁵ times lighter than free electrons) and long propagation distances. Additionally, exciton-polaritons also carry properties of the host material excitons such as spin and valley polarization and can be probed via the photons that leak out of the cavities since the photon carries all the information owing to conservation laws. Since the first demonstration …

Optical And Collective Properties Of Excitons In 2d Semiconductors, Matthew N. Brunetti

Dissertations, Theses, and Capstone Projects

We study the properties of excitons in 2D semiconductors (2DSC) by numerically solving the Schr\"{o}dinger equation for an interacting electron and hole in the effective mass approximation, then calculating optical properties such as the transition energies, oscillator strengths, and absorption coefficients. Our theoretical approach allows us to consider both direct excitons in monolayer (ML) 2DSC and spatially indirect excitons in heterostructures (HS) consisting of two 2DSC MLs separated by few-layer insulating hexagonal boron nitride (h-BN). In particular, we study indirect excitons in TMDC HS, namely MoS₂, MoSe₂, WS₂, and WSe₂; …

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 …

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 (Bi_1-xSb_x)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 …

Topological Insulating States In Photonics And Acoustics, Xiang Ni

Dissertations, Theses, and Capstone Projects

Recent surge of interest in topological insulators, insulating in their interior but conducting at the surfaces or interfaces of different domains, has led to the discovery of a variety of new topological states, and their topological invariants are characterized by numerous approaches in the category of topological band theory. The common features shared by topological insulators include, the topological phase transition occurs if the bulk bandgap is formed due to the symmetries reduction, the topological invariants exist characterizing the global properties of the material and inherently robust to disorder and continuous perturbations irrespective of the local details. Most importantly, these …

High-Pressure High-Temperature Exploration Of Phase Boundaries Using Raman Spectroscopy, Jasmine Kashmir Hinton

UNLV Theses, Dissertations, Professional Papers, and Capstones

Metastability of states can provide interesting properties that may not be readily accessible in a material’s ground state. Many materials show high levels of polymorphism, indicating a rich energy landscape and a potential for metastable states. Melt crystallization techniques provide a potential route to these states. We use a resistively heated diamond anvil cell (DAC) with fine control of a system’s pressure and temperature to explore these systems. Raman spectroscopy is used to track subtle structural changes across phase boundaries. Organic systems, such as glycine and aspirin, were our initial interest due to their high polymorphism and reported low melting …