Matching Items (43)
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Description
Semiconductor nanostructures are promising building blocks for light management in thin silicon solar cells and silicon-based tandems due their tunable optical properties. The present dissertation is organized along three main research areas: (1) characterization and modeling of III-V nanowires as active elements of solar cell tandems, (2) modeling of silicon

Semiconductor nanostructures are promising building blocks for light management in thin silicon solar cells and silicon-based tandems due their tunable optical properties. The present dissertation is organized along three main research areas: (1) characterization and modeling of III-V nanowires as active elements of solar cell tandems, (2) modeling of silicon nanopillars for reduced optical losses in ultra-thin silicon solar cells, and (3) characterization and modeling of nanoparticle-based optical coatings for light management.

First, the recombination mechanisms in polytype GaAs nanowires are studied through photoluminescence measurements coupled with rate equation analysis. When photons are absorbed in polytype nanowires, electrons and holes quickly thermalize to the band-edges of the zinc-blende and wurtzite phases, recombining indirectly in space across the type-II offset. Using a rate equation model, different configurations of polytype defects along the nanowire are investigated, which compare well with experiment considering spatially indirect recombination between different polytypes, and defect-related recombination due to twin planes and other defects. The presented analysis is a path towards predicting the performance of nanowire-based solar cells.

Following this topic, the optical mechanisms in silicon nanopillar arrays are investigated using full-wave optical simulations in comparison to measured reflectance data. The simulated electric field energy density profiles are used to elucidate the mechanisms contributing to the reduced front surface reflectance. Strong forward scattering and resonant absorption are observed for shorter- and longer- aspect ratio nanopillars, respectively, with the sub-wavelength periodicity causing additional diffraction. Their potential for light-trapping is investigated using full-wave optical simulation of an ultra-thin nanostructured substrate, where the conventional light-trapping limit is exceeded for near-bandgap wavelengths.

Finally, the correlation between the optical properties of silicon nanoparticle layers to their respective pore size distributions is investigated using optical and structural characterization coupled with full-wave optical simulation. The presence of

scattering is experimentally correlated to wider pore size distributions obtained from nitrogen adsorption measurements. The correlation is validated with optical simulation of random and clustered structures, with the latter approximating experimental. Reduced structural inhomogeneity in low-refractive-index nanoparticle inter-layers at the metal/semiconductor interface improves their performance as back reflectors, while reducing parasitic absorption in the metal.
ContributorsVulic, Natasa (Author) / Goodnick, Stephen M (Thesis advisor) / Honsberg, C. (Christiana B.) (Committee member) / Holman, Zachary C (Committee member) / Smith, David J. (Committee member) / Arizona State University (Publisher)
Created2019
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Description
Proteins play a central role to human body and biological activities. As powerful tools for protein detections, many surface plasmon resonance based techniques have been developed to enhance the sensitivity. However, sensitivity is not the only final goal. As a biosensor, four things really matter: sensitivity, specificity, resolution (temporal/spatial) and

Proteins play a central role to human body and biological activities. As powerful tools for protein detections, many surface plasmon resonance based techniques have been developed to enhance the sensitivity. However, sensitivity is not the only final goal. As a biosensor, four things really matter: sensitivity, specificity, resolution (temporal/spatial) and throughput.

This dissertation presents several works on developing novel plasmonic based techniques for protein detections on the last two aspects to extend the application field. A fast electrochemically controlled plasmonic detection technique is first developed with the capability of monitoring electrochemical signal with nanosecond response time. The study reveals that the conformational gating of electron transfer in a redox protein (cytochrome c) takes place over a broad range of time scales (sub-µs to ms). The second platform integrates ultra-low volume piezoelectric liquid dispensing and plasmonic imaging detection to monitor different protein binding processes simultaneously with low sample cost. Experiment demonstrates the system can observe binding kinetics in 10×10 microarray of 6 nL droplet, with variations of kinetic rate constants among spots less than ±5%. A focused plasmonic imaging system with bi-cell algorithm is also proposed for spatial resolution enhancement. The two operation modes, scanning mode and focus mode, can be applied for different purposes. Measurement of bacterial aggregation demonstrates the higher spatial resolution. Detections of polystyrene beads binding and 50 nm gold nanoparticles oscillation show a high signal to noise ratio of the system.

The real properties of protein rely on its dynamic personalities. The above works shed light upon fast and high throughput detection of protein kinetics, and enable more applications for plasmonic imaging techniques. It is anticipated that such methods will help to invoke a new surge to unveil the mysteries of biological activities and chemical process.
ContributorsWang, Yan (Author) / Tao, Nongjian (Thesis advisor) / Chae, Junseok (Committee member) / Goryll, Michael (Committee member) / Wang, Shaopeng (Committee member) / Arizona State University (Publisher)
Created2018
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Description
The following paper discusses the validation of the TolTEC optical design along with a progress report regarding the design of the optical mounting system. Solidworks and Zemax were used in conjunction to model the proposed optics designs. The final optical design was selected through extensive CAD modeling and testing within

The following paper discusses the validation of the TolTEC optical design along with a progress report regarding the design of the optical mounting system. Solidworks and Zemax were used in conjunction to model the proposed optics designs. The final optical design was selected through extensive CAD modeling and testing within the Large Millimeter Telescope receiver room. The TolTEC optics can be divided into two arrays, one comprised of the warm mirrors and the second, cryogenically-operated cold mirrors. To ensure structural stability and optical performance, the mechanical design of these systems places a heavy emphasis on rigidity. This is done using a variety of design techniques that restrict motion along the necessary degrees of freedom and maximize moment of inertia while minimizing weight. Work will resume on this project in the Fall 2017 semester.
ContributorsKelso, Rhys Partain (Author) / Mauskopf, Philip (Thesis director) / Groppi, Christopher (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
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Description
In this experiment, an attempt was made to measure the index of refraction of a thin glass microscope slide, with a known thickness of 1.01 mm. A monochromatic laser with wavelength of 532nm was employed to generate the interference pattern through the use of a Michelson interferometer. The slide was

In this experiment, an attempt was made to measure the index of refraction of a thin glass microscope slide, with a known thickness of 1.01 mm. A monochromatic laser with wavelength of 532nm was employed to generate the interference pattern through the use of a Michelson interferometer. The slide was placed in the path of one of the beams. The slide could then be rotated through a series of angles, and, from the resulting changes in the interference pattern, the index of refraction of the slide could be extracted. The index of refraction was found to be 1.5±0.02.
ContributorsSwenson, Jordan (Author) / Sukharev, Maxim (Thesis director) / Bennett, Peter (Committee member) / Barrett, The Honors College (Contributor) / Department of Physics (Contributor)
Created2014-05
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Description
Within the context of the Finite-Difference Time-Domain (FDTD) method of simulating interactions between electromagnetic waves and matter, we adapt a known absorbing boundary condition, the Convolutional Perfectly-Matched Layer (CPML) to a background of Drude-dispersive medium. The purpose of this CPML is to terminate the virtual grid of scattering simulations by

Within the context of the Finite-Difference Time-Domain (FDTD) method of simulating interactions between electromagnetic waves and matter, we adapt a known absorbing boundary condition, the Convolutional Perfectly-Matched Layer (CPML) to a background of Drude-dispersive medium. The purpose of this CPML is to terminate the virtual grid of scattering simulations by absorbing all outgoing radiation. In this thesis, we exposit the method of simulation, establish the Perfectly-Matched Layer as a domain which houses a spatial-coordinate transform to the complex plane, construct the CPML in vacuum, adapt the CPML to the Drude medium, and conclude with tests of the adapted CPML for two different scattering geometries.
ContributorsThornton, Brandon Maverick (Author) / Sukharev, Maxim (Thesis director) / Goodnick, Stephen (Committee member) / School of Mathematical and Statistical Sciences (Contributor) / Department of Physics (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
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Description
III-nitride InGaN light-emitting diodes (LEDs) enable wide range of applications in solid-state lighting, full-color displays, and high-speed visible-light communication. Conventional InGaN quantum well LEDs grown on polar c-plane substrate suffer from quantum confined Stark effect due to the large internal polarization-related fields, leading to a reduced radiative recombination rate and

III-nitride InGaN light-emitting diodes (LEDs) enable wide range of applications in solid-state lighting, full-color displays, and high-speed visible-light communication. Conventional InGaN quantum well LEDs grown on polar c-plane substrate suffer from quantum confined Stark effect due to the large internal polarization-related fields, leading to a reduced radiative recombination rate and device efficiency, which limits the performance of InGaN LEDs in high-speed communication applications. To circumvent these negative effects, non-trivial-cavity designs such as flip-chip LEDs, metallic grating coated LEDs are proposed. This oral defense will show the works on the high-modulation-speed LEDs from basic ideas to applications. Fundamental principles such as rate equations for LEDs/laser diodes (LDs), plasmonic effects, Purcell effects will be briefly introduced. For applications, the modal properties of flip-chip LEDs are solved by implementing finite difference method in order to study the modulation response. The emission properties of highly polarized InGaN LEDs coated by metallic gratings are also investigated by finite difference time domain method.
ContributorsChen, Hong (Author) / Zhao, Yuji (Thesis advisor) / Yao, Yu (Committee member) / Wang, Liping (Committee member) / Arizona State University (Publisher)
Created2016
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Description
Current organic light emitting diodes (OLEDs) suffer from the low light extraction efficiency. In this thesis, novel OLED structures including photonic crystal, Fabry-Perot resonance cavity and hyperbolic metamaterials were numerically simulated and theoretically investigated. Finite-difference time-domain (FDTD) method was employed to numerically simulate the light extraction efficiency of various 3D

Current organic light emitting diodes (OLEDs) suffer from the low light extraction efficiency. In this thesis, novel OLED structures including photonic crystal, Fabry-Perot resonance cavity and hyperbolic metamaterials were numerically simulated and theoretically investigated. Finite-difference time-domain (FDTD) method was employed to numerically simulate the light extraction efficiency of various 3D OLED structures. With photonic crystal structures, a maximum of 30% extraction efficiency is achieved. A higher external quantum efficiency of 35% is derived after applying Fabry-Perot resonance cavity into OLEDs. Furthermore, different factors such as material properties, layer thicknesses and dipole polarizations and locations have been studied. Moreover, an upper limit for the light extraction efficiency of 80% is reached theoretically with perfect reflector and single dipole polarization and location. To elucidate the physical mechanism, transfer matrix method is introduced to calculate the spectral-hemispherical reflectance of the multilayer OLED structures. In addition, an attempt of using hyperbolic metamaterial in OLED has been made and resulted in 27% external quantum efficiency, due to the similar mechanism of wave interference as Fabry-Perot structure. The simulation and optimization methods and findings would facilitate the design of next generation, high-efficiency OLED devices.
ContributorsSu, Hang (Author) / Wang, Liping (Thesis advisor) / Li, Jian (Committee member) / Huang, Huei-Ping (Committee member) / Arizona State University (Publisher)
Created2016
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Description
The interaction of light with nanoscale structures consisting of metal and two-level quantum emitters is investigated computationally. A method of tilting the incoming electromagnetic wave is used to demonstrate coupling between a sinusoidal grating and two-level quantum emitters. A system consisting of metallic v-grooves and two-level emitters is thoroughly explored

The interaction of light with nanoscale structures consisting of metal and two-level quantum emitters is investigated computationally. A method of tilting the incoming electromagnetic wave is used to demonstrate coupling between a sinusoidal grating and two-level quantum emitters. A system consisting of metallic v-grooves and two-level emitters is thoroughly explored in the linear regime, where the spatially uniform fields provide a unique means of characterizing the coupling between the v-grooves and emitters. Furthermore, subwavelength spatial effects in the ground state population of emitters in the v-grooves are observed and analyzed in the non-linear regime. Finally, photon echoes are explored in the case of a one-dimensional ensemble of interacting two-level emitters as well as two-level emitters coupled to metallic slits, demonstrating the influence of collective effects on the echo amplitude in the former and the modifcation of the photon echo due to interaction with surface plasmons on the slits in the latter.
ContributorsBlake, Adam H (Author) / Sukharev, Maxim (Thesis advisor) / Treacy, Mike (Committee member) / Shovkovy, Igor (Committee member) / Drucker, Jeff (Committee member) / Arizona State University (Publisher)
Created2016
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Description
The study of subwavelength behavior of light and nanoscale lasing has broad

potential applications in various forms of computation i.e. optical and quantum, as well as

in energy engineering. Although this field has been under active research, there has been

little work done on describing the behaviors of threshold and

The study of subwavelength behavior of light and nanoscale lasing has broad

potential applications in various forms of computation i.e. optical and quantum, as well as

in energy engineering. Although this field has been under active research, there has been

little work done on describing the behaviors of threshold and saturation. Particularly, how

the gain-molecule behavior affects the lasing behavior has yet to be investigated.

In this work, the interaction of surface-plasmon-polaritons (SPPs) and molecules is

observed in lasing. Various phenomenologies are observed related to the appearance of the

threshold and saturation regions. The lasing profile, as a visual delimiter of lasing threshold

and saturation, is introduced and used to study various parametrical dependencies of lasing,

including the number-density of molecules, the molecular thickness and the frequency

detuning between the molecular transition frequency and the SPP resonant frequency. The

molecular population distributions are studied in terminal and dynamical methods and are

found to contain unexpected and theoretically challenging properties. Using an average

dynamical analysis, the simulated spontaneous emission cascade can be clearly seen.

Finally, theoretical derivations of simple 1D strands of dipoles are presented in both

the exact and mean-field approximation, within the density matrix formalism. Some

preliminary findings are presented, detailing the observed behaviors of some simple

systems.
ContributorsBrewer, Andre J (Author) / Sukharev, Maxim (Thesis advisor) / Rivera, Daniel E (Thesis advisor) / Menéndez, Jose (Committee member) / Arizona State University (Publisher)
Created2017
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Description
Semiconductor nanolasers, as a frontier subject has drawn a great deal of attention over the past decade. Semiconductor nanolasers are compatible with on-chip integrations towards the ultimate realization of photonic integrated circuits. However, innovative approaches are strongly required to overcome the limitation of lattice-mismatch issues. In this dissertation, two alternative

Semiconductor nanolasers, as a frontier subject has drawn a great deal of attention over the past decade. Semiconductor nanolasers are compatible with on-chip integrations towards the ultimate realization of photonic integrated circuits. However, innovative approaches are strongly required to overcome the limitation of lattice-mismatch issues. In this dissertation, two alternative approaches are employed to overcome the lattice-mismatch issues. i) By taking advantage of nanowires or nanobelts techniques, flexibility in bandgap engineering has been greatly expanded, resulting in the nanolasers with wide wavelength coverage and tunability. Simultaneous two-color lasing in green and red is firstly achieved from monolithic cadmium sulfide selenide nanosheets. The wavelength separation is up to 97 nm at room temperature, larger than the gain bandwidth of a single semiconductor material in the visible wavelength range. The strategies adopted for two-color lasers eventually leads to the realization of simultaneous red, green and blue lasing and white lasing from a single zinc cadmium sulfide selenide nanosheet with color tunability in the full visible range, making a major milestone in the ultimate solution of laser illumination and laser display. In addition, with the help of nanowire techniques, material emission has been extended to mid-infrared range, enabling lasing at ~3µm from single lead sulfide subwavelength wires at 180 K. The cavity volume of the subwavelength laser is down to 0.44 λ3 and the wavelength tuning range is over 270 nm through the thermo-optic mechanism, exhibiting considerable potentials for on-chip applications in mid-infrared wavelength ranges. ii) By taking advantage of membrane transfer techniques, heterogeneous integration of compound semiconductor and waveguide material becomes possible, enabling the successful fabrication of membrane based nano-ring lasers on a dielectric substrate. Thin membranes with total thickness of ~200nm are first released from the original growth substrate and then transferred onto a receiving substrate through a generally applicable membrane transfer method. Nano-ring arrays are then defined by photolithography with an individual radius of 750 nm and a radial thickness of 400-500 nm. As a result, single mode lasing is achieved on individual nano-ring lasers at ~980 nm with cavity volumes down to 0.24 λ3, providing a general avenue for future heterogeneous integration of nanolasers on silicon substrates.
ContributorsFan, Fan (Author) / Ning, Cun-Zheng (Thesis advisor) / Balanis, Constantine A (Committee member) / Palais, Joseph C. (Committee member) / Yu, Hongbin (Committee member) / Arizona State University (Publisher)
Created2016