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University of Colorado
1.
Chappell, Helen Elizabeth.
Temperature and Size Dependence of Photoluminescence in Lead Chalcogenide Quantum Dot Films.
Degree: MS, Physics, 2011, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/37 
► This work presents temperature-dependent photoluminescence spectra for nanocrystalline films, cast from PbS and PbSe quantum dots with diameters ranging from 0.6 nm to 9.2…
(more)
▼ This work presents temperature-dependent photoluminescence spectra for nanocrystalline films, cast from PbS and PbSe quantum dots with diameters ranging from 0.6 nm to 9.2 nm (band gaps from 0.52 eV to 1.96 eV). Across all sizes and materials, two emission peaks are observed in the photoluminescence spectra. A low-energy peak dominates at low temperatures, and a high-energy peak dominates at high temperatures. No materials-dependent effects are noted, but the spectral behavior is a strong function of nanocrystal band gap. Intensity trends, the spacing of the two emission peaks, and the shift of peak emission energy with temperature are all affected by band gap changes. Results are suggestive of a scenario in which one emission peak is due to a fixed-energy trap state. The impact of air exposure on spectral behavior is also considered, and likely explains many previous inconsistencies between similar studies. High-temperature emission is strongly quenched by exposure to oxygen, with quenching effects beginning within seconds of exposure. Low-temperature emission is largely unaffected by short-term air exposure. These results are modeled with the introduction of a dark trap state whose concentration grows as air exposure increases.
Advisors/Committee Members: Daniel Dessau, Arthur Nozik, Charles Rogers.
Subjects/Keywords: lead selenide; lead sulfide; oxidation; photoluminescence; quantum dots; trap states; Chemistry; Physics
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APA (6th Edition):
Chappell, H. E. (2011). Temperature and Size Dependence of Photoluminescence in Lead Chalcogenide Quantum Dot Films. (Masters Thesis). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/37
Chicago Manual of Style (16th Edition):
Chappell, Helen Elizabeth. “Temperature and Size Dependence of Photoluminescence in Lead Chalcogenide Quantum Dot Films.” 2011. Masters Thesis, University of Colorado. Accessed April 14, 2021.
https://scholar.colorado.edu/phys_gradetds/37.
MLA Handbook (7th Edition):
Chappell, Helen Elizabeth. “Temperature and Size Dependence of Photoluminescence in Lead Chalcogenide Quantum Dot Films.” 2011. Web. 14 Apr 2021.
Vancouver:
Chappell HE. Temperature and Size Dependence of Photoluminescence in Lead Chalcogenide Quantum Dot Films. [Internet] [Masters thesis]. University of Colorado; 2011. [cited 2021 Apr 14].
Available from: https://scholar.colorado.edu/phys_gradetds/37.
Council of Science Editors:
Chappell HE. Temperature and Size Dependence of Photoluminescence in Lead Chalcogenide Quantum Dot Films. [Masters Thesis]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/phys_gradetds/37
University of Colorado
2.
Allman, Michael Shane.
Coherent Tunable Coupling of Quantum Circuits.
Degree: PhD, Physics, 2011, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/38
► This thesis presents a detailed investigation of coherent tunable coupling between two coupled quantum circuits. Quantum circuits have the potential to be used as…
(more)
▼ This thesis presents a detailed investigation of coherent tunable coupling between two coupled quantum circuits. Quantum circuits have the potential to be used as the fundamental building blocks in quantum processors. Any large scale quantum processor will be composed of a large number of these coupled circuits. The efficient implementation of quantum algorithms will be difficult without a reliable mechanism for controlling the interaction strength between coupled systems, while preserving the delicate quantum information stored in the coherent superpositions of quantum states. We show that a flux-biased rf-SQUID can be used to coherently mediate the interaction between two coupled quantum circuits, a phase qubit and LC resonator. This interaction results from an effective mutual inductance between the qubit and resonator as a result of their direct coupling to the rf-SQUID. The sign and magnitude of this effective mutual inductance can be tuned with applied flux to the rf-SQUID, thus controlling the coupled interactions over a large range. We observe the modulation in coupling strength using measurements in both the frequency and time domains. The measurements are shown to agree well with theoretical predictions. This thesis discusses all aspects of the experiments from a theoretical description of each component to the design, fabrication, experimental setup and measurements.
Advisors/Committee Members: Raymond W. Simmonds, Charles Rogers, Kent Irwin.
Subjects/Keywords: Macroscopic quantum systems; Phase qubits; Quantum circuits; Quantum computing; Superconducting qubits; Tunable coupling; Physics; Quantum Physics
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APA (6th Edition):
Allman, M. S. (2011). Coherent Tunable Coupling of Quantum Circuits. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/38
Chicago Manual of Style (16th Edition):
Allman, Michael Shane. “Coherent Tunable Coupling of Quantum Circuits.” 2011. Doctoral Dissertation, University of Colorado. Accessed April 14, 2021.
https://scholar.colorado.edu/phys_gradetds/38.
MLA Handbook (7th Edition):
Allman, Michael Shane. “Coherent Tunable Coupling of Quantum Circuits.” 2011. Web. 14 Apr 2021.
Vancouver:
Allman MS. Coherent Tunable Coupling of Quantum Circuits. [Internet] [Doctoral dissertation]. University of Colorado; 2011. [cited 2021 Apr 14].
Available from: https://scholar.colorado.edu/phys_gradetds/38.
Council of Science Editors:
Allman MS. Coherent Tunable Coupling of Quantum Circuits. [Doctoral Dissertation]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/phys_gradetds/38
University of Colorado
3.
Ashby, Ava.
The Study of Modeled Atomtronic Barrier Potentials Through the Impedance Method.
Degree: MS, Physics, 2016, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/165
► The general impedance method developed by Khondker et.al [1] is applied to multiple barrier potentials to study the transmission behaviors of a single Gaussian…
(more)
▼ The general impedance method developed by Khondker et.al [1] is applied to multiple barrier potentials to study the transmission behaviors of a single Gaussian barrier potential, double rectangular barrier potential, and a double Gaussian barrier potential. Using the impedance method we will find quantum mechanical transmission behaviors like resonant tunneling for the quasi bound-states of the double barrier potentials. The single Gaussian barrier potential is an approximation for the atomtronic battery and the double Gaussian barrier potential is an approximation for the atomtronic transistor. Thus far, the atomtronic work presented in reference [2] was done in the classical regime where thermal currents dominate. The work presented in this thesis analyzes the quantum mechanical characteristics, such as tunneling, to be incorporated and perhaps used to explore coherent transistor action.
Advisors/Committee Members: Dana Anderson, Heather Lewandowski, Charles Rogers.
Subjects/Keywords: atomtronics; impedance method; numerical method; quantum mechanical transmission probablity; Physics
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APA (6th Edition):
Ashby, A. (2016). The Study of Modeled Atomtronic Barrier Potentials Through the Impedance Method. (Masters Thesis). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/165
Chicago Manual of Style (16th Edition):
Ashby, Ava. “The Study of Modeled Atomtronic Barrier Potentials Through the Impedance Method.” 2016. Masters Thesis, University of Colorado. Accessed April 14, 2021.
https://scholar.colorado.edu/phys_gradetds/165.
MLA Handbook (7th Edition):
Ashby, Ava. “The Study of Modeled Atomtronic Barrier Potentials Through the Impedance Method.” 2016. Web. 14 Apr 2021.
Vancouver:
Ashby A. The Study of Modeled Atomtronic Barrier Potentials Through the Impedance Method. [Internet] [Masters thesis]. University of Colorado; 2016. [cited 2021 Apr 14].
Available from: https://scholar.colorado.edu/phys_gradetds/165.
Council of Science Editors:
Ashby A. The Study of Modeled Atomtronic Barrier Potentials Through the Impedance Method. [Masters Thesis]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/phys_gradetds/165
University of Colorado
4.
Nummy, Thomas J.
Polarization Dependent Angle Resolved Photoemission Spectroscopy for the Determination of Intrinsic Material Symmetries.
Degree: PhD, 2018, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/244
► In this thesis I investigate the utility of the polarization and angle dependence of the photoemission matrix element in angle resolved photoemission spectroscopy (ARPES).…
(more)
▼ In this thesis I investigate the utility of the polarization and angle dependence of the photoemission matrix element in angle resolved photoemission spectroscopy (ARPES). This technique is capable of determining internal symmetries of the electronic wave functions in crystalline solids and has been historically underutilized in the ARPES community. In Chapter 1, I introduce the ARPES technique, the established theory and models behind it, and the experimental considerations in performing the technique. It is my personal belief that the fastest way to build intuition for complex physical phenomena is through simulation, and a good portion of graduate school career was spent developing simulation toolkits for the photoemission process. This work will be covered in detail in chapter 2. The later chapters cover the application of this technique to various materials systems. Chapter 3 focuses on the use of this technique to observe a topological phase transition in the Lanthanum Monopnictides. Chapter 4 contains my work on the Cuprate high temperature superconductors, Bi
2Sr
2Ca
1Cu
2O
8+x and La
2-xSr
xCuO
2 and the use of tight binding simulations to approximate the single particle wave function in this material.
Advisors/Committee Members: Daniel Dessau, Gerald Arnold, Micheal Hermele, Charles Rogers, Joel Eaves.
Subjects/Keywords: polarization; angle resolved photoemission spectrosopy; topological phase transition; intrinsic material symmetries; electronic wave function; Materials Science and Engineering; Physics
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APA (6th Edition):
Nummy, T. J. (2018). Polarization Dependent Angle Resolved Photoemission Spectroscopy for the Determination of Intrinsic Material Symmetries. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/244
Chicago Manual of Style (16th Edition):
Nummy, Thomas J. “Polarization Dependent Angle Resolved Photoemission Spectroscopy for the Determination of Intrinsic Material Symmetries.” 2018. Doctoral Dissertation, University of Colorado. Accessed April 14, 2021.
https://scholar.colorado.edu/phys_gradetds/244.
MLA Handbook (7th Edition):
Nummy, Thomas J. “Polarization Dependent Angle Resolved Photoemission Spectroscopy for the Determination of Intrinsic Material Symmetries.” 2018. Web. 14 Apr 2021.
Vancouver:
Nummy TJ. Polarization Dependent Angle Resolved Photoemission Spectroscopy for the Determination of Intrinsic Material Symmetries. [Internet] [Doctoral dissertation]. University of Colorado; 2018. [cited 2021 Apr 14].
Available from: https://scholar.colorado.edu/phys_gradetds/244.
Council of Science Editors:
Nummy TJ. Polarization Dependent Angle Resolved Photoemission Spectroscopy for the Determination of Intrinsic Material Symmetries. [Doctoral Dissertation]. University of Colorado; 2018. Available from: https://scholar.colorado.edu/phys_gradetds/244
University of Colorado
5.
Joshi, Saumil.
Performance limits of optical rectennas.
Degree: PhD, Electrical, Computer & Energy Engineering, 2015, University of Colorado
URL: https://scholar.colorado.edu/ecen_gradetds/107
► Optical rectennas are antenna-coupled diode rectifiers that receive and convert optical-frequency electromagnetic radiation into DC output. Because classical rectennas working at microwave frequencies can…
(more)
▼ Optical rectennas are antenna-coupled diode rectifiers that receive and convert optical-frequency electromagnetic radiation into DC output. Because classical rectennas working at microwave frequencies can achieve very high rectification efficiencies, rectennas working as solar cells were expected to have efficiencies significantly higher than conventional solar cells. By applying the theory of photon-assisted tunneling (PAT) to optical rectennas at solar intensities, I show that the power conversion efficiency of rectenna solar cells is fundamentally limited to the Trivich-Flinn efficiency limit of 44%. This unexpected result is the same as the Shockley-Queisser ultimate efficiency limit of conventional solar cells.
Is it possible to exceed this efficiency limit? I answer this question by showing that there is a correspondence between the quantum and classical operation of a rectenna. Such correspondence allows high frequency rectennas to operate in the same way as classical rectennas, and to potentially exceed the Trivich-Flinn efficiency limit. I propose two ways to achieve classical operation in optical rectennas.
Diode design is crucial for achieving high rectification efficiency. High-speed diodes, such as metal-insulator-metal (MIM) diodes, have insufficient asymmetry for harvesting low intensity radiation. I suggest steps to improve the characteristics of double insulator MIM diodes and calculate their power conversion efficiency using PAT theory. A simple figure of merit is provided to quickly assess the usefulness of MIM diodes in optical rectennas.
Although ineffective at visible frequencies, MIM diodes have
RC time constants sufficient for operation at low terahertz frequencies, useful in applications including detection and high-speed electronics. I develop the steps to design MIM diodes at 1 THz, propose materials that will give the required current-voltage characteristics and
RC time constant, perform electrical and optical measurements on fabricated devices, and suggest steps to improve their performance.
In contrast to MIM diodes, novel planar devices called geometric diodes have very low
RC time constants and are capable of rectifying radiation up to 100 THz. I measure the infrared optical response of graphene-based geometric diodes, and demonstrate one of the best room-temperature detectors working at 28 THz.
Advisors/Committee Members: Garret Moddel, Wounjhang Park, Dragan Maksimovic, Milos Popovic, Charles Rogers.
Subjects/Keywords: antennas; detectors; diodes; electron tunneling; PAT; Electrical and Electronics
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APA (6th Edition):
Joshi, S. (2015). Performance limits of optical rectennas. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/ecen_gradetds/107
Chicago Manual of Style (16th Edition):
Joshi, Saumil. “Performance limits of optical rectennas.” 2015. Doctoral Dissertation, University of Colorado. Accessed April 14, 2021.
https://scholar.colorado.edu/ecen_gradetds/107.
MLA Handbook (7th Edition):
Joshi, Saumil. “Performance limits of optical rectennas.” 2015. Web. 14 Apr 2021.
Vancouver:
Joshi S. Performance limits of optical rectennas. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Apr 14].
Available from: https://scholar.colorado.edu/ecen_gradetds/107.
Council of Science Editors:
Joshi S. Performance limits of optical rectennas. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/ecen_gradetds/107
University of Colorado
6.
Montague, Joshua R.
As-Grown Gallium Nitride Nanowire Electromechanical Resonators.
Degree: PhD, Physics, 2013, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/74
► Technological development in recent years has led to a ubiquity of micro- and nano-scale electromechanical devices. Sensors for monitoring temperature, pressure, mass, etc., are…
(more)
▼ Technological development in recent years has led to a ubiquity of micro- and nano-scale electromechanical devices. Sensors for monitoring temperature, pressure, mass, etc., are now found in nearly all electronic devices at both the industrial and consumer levels. As has been true for integrated circuit electronics, these electromechanical devices have continued to be scaled down in size. For many nanometer-scale structures with large surface-to-volume ratio, dissipation (energy loss) becomes prohibitively large causing a decreasing sensitivity with decreasing sensor size.
In this work, gallium nitride (GaN) nanowires are investigated as singly-clamped (cantilever) mechanical resonators with typical mechanical quality factors,
Q (equal to the ratio of resonance frequency to peak full-width-at-half-maximum-power) and resonance frequencies, respectively, at or above 30,000, and near 1 MHz. These
Q values {in vacuum at room temperature{ indicate very low levels of dissipation; they are essentially the same as those for bulk quartz crystal resonators that form the basis of simple clocks and mass sensors. The GaN nanowires have lengths and diameters, respectively, of approximately 15 micrometers and hundreds of nanometers. As-grown GaN nanowire
Q values are larger than other similarly-sized, bottom-up, cantilever resonators and this property makes them very attractive for use as resonant sensors.
We demonstrate the capability of detecting sub-monolayer levels of atomic layer deposited (ALD) films, and the robust nature of the GaN nanowires structure that allows for their 'reuse' after removal of such layers. In addition to electron microscope-based measurement techniques, we demonstrate the successful capacitive detection of a single nanowire using microwave homodyne reflectometry. This technique is then extended to allow for simultaneous measurements of large ensembles of GaN nanowires on a single sample, providing statistical information about the distribution of individual nanowire properties. We observe nanowire-to-nanowire variations in the temperature dependence of GaN nanowire resonance frequency and in the observed mechanical dissipation. We also use this ensemble measurement technique to demonstrate unique, very low-loss resonance behavior at low temperatures. The low dissipation (and corresponding large
Q values) observed in as-grown GaN nanowires also provides a unique opportunity for studying fundamental energy loss mechanisms in nano-scale objects. With estimated mass sensitivities on the level of zeptograms (10
-21 g) in a one second averaging time, GaN nanowires may be a significant addition to the field of resonant sensors and worthy of future research and device integration.
Advisors/Committee Members: Charles Rogers, Victor M. Bright, Cindy Regal, Kyle McElroy, Daniel Dessau.
Subjects/Keywords: dissipation; gallium nitride; mems; nanowire; resonator; Physics
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APA (6th Edition):
Montague, J. R. (2013). As-Grown Gallium Nitride Nanowire Electromechanical Resonators. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/74
Chicago Manual of Style (16th Edition):
Montague, Joshua R. “As-Grown Gallium Nitride Nanowire Electromechanical Resonators.” 2013. Doctoral Dissertation, University of Colorado. Accessed April 14, 2021.
https://scholar.colorado.edu/phys_gradetds/74.
MLA Handbook (7th Edition):
Montague, Joshua R. “As-Grown Gallium Nitride Nanowire Electromechanical Resonators.” 2013. Web. 14 Apr 2021.
Vancouver:
Montague JR. As-Grown Gallium Nitride Nanowire Electromechanical Resonators. [Internet] [Doctoral dissertation]. University of Colorado; 2013. [cited 2021 Apr 14].
Available from: https://scholar.colorado.edu/phys_gradetds/74.
Council of Science Editors:
Montague JR. As-Grown Gallium Nitride Nanowire Electromechanical Resonators. [Doctoral Dissertation]. University of Colorado; 2013. Available from: https://scholar.colorado.edu/phys_gradetds/74
University of Colorado
7.
Whittaker, Jed Douglas.
Dispersive measurement of a metastable phase qubit using a tunable cavity.
Degree: PhD, Physics, 2012, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/80
► A metastable phase qubit was measured using a tunable cavity by two methods: a tunneling measurement followed by magnetometry readout by the cavity, and…
(more)
▼ A metastable phase qubit was measured using a tunable cavity by two methods: a tunneling measurement followed by magnetometry readout by the cavity, and a non destructive dispersive measurement of the qubit by the cavity. The Purcell effect was observed as a decrease in the energy relaxation time of the qubit in the vicinity of the cavity, and could be manipulated by dynamically tuning the cavity. The observed dispersive shift of the cavity did not match the two-level system model for nonlinear qubits. Instead, a three-level model of the qubit was needed to describe the data, necessitated by the weakly nonlinear nature of the metastable phase qubit. The cavity was also used to directly observe the photons radiated by a tunneling measurement.
Advisors/Committee Members: Raymond W. Simmonds, Charles Rogers, Konrad Lehnert, Zoya Popovic, Immanuel Knill.
Subjects/Keywords: circuit quantum electrodynamics; phase qubit; quantum computing; superconductivity; Condensed Matter Physics; Physics; Quantum Physics
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APA (6th Edition):
Whittaker, J. D. (2012). Dispersive measurement of a metastable phase qubit using a tunable cavity. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/80
Chicago Manual of Style (16th Edition):
Whittaker, Jed Douglas. “Dispersive measurement of a metastable phase qubit using a tunable cavity.” 2012. Doctoral Dissertation, University of Colorado. Accessed April 14, 2021.
https://scholar.colorado.edu/phys_gradetds/80.
MLA Handbook (7th Edition):
Whittaker, Jed Douglas. “Dispersive measurement of a metastable phase qubit using a tunable cavity.” 2012. Web. 14 Apr 2021.
Vancouver:
Whittaker JD. Dispersive measurement of a metastable phase qubit using a tunable cavity. [Internet] [Doctoral dissertation]. University of Colorado; 2012. [cited 2021 Apr 14].
Available from: https://scholar.colorado.edu/phys_gradetds/80.
Council of Science Editors:
Whittaker JD. Dispersive measurement of a metastable phase qubit using a tunable cavity. [Doctoral Dissertation]. University of Colorado; 2012. Available from: https://scholar.colorado.edu/phys_gradetds/80
University of Colorado
8.
Sankar, Shannon Reynier.
Approaching broadband quantum-limited displacement noise in a deformable optical cavity.
Degree: PhD, Physics, 2012, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/82
► An outstanding goal of the optomechanics community, particularly in the field of gravitational wave detection, is to demonstrate a system with a broadband displacement…
(more)
▼ An outstanding goal of the optomechanics community, particularly in the field of gravitational wave detection, is to demonstrate a system with a broadband displacement sensitivity limited by quantum fluctuations of the probe field. This thesis presents significant progress in this direction, namely a means of achieving a sufficiently small off-resonant thermal noise of a deformable optomechanical cavity through the incorporation of a low mass, highly compliant, cryogenically cooled mirror structure with a sensitive motional readout. We conclusively demonstrate the mitigation of Brownian fluctuations in this system by the reduction of the thermal bath temperature, and our measurements are shown to be in close agreement with a finite element analysis of the device. This analysis has been utilized in devising improved oscillator geometries. This work provides a clear path towards the observation of quantum fluctuations in our system and demonstrates the Brownian properties of the crystalline multilayers which make them a promising technology for the realization of low-thermal-noise reflectors in the quantum regime.
Advisors/Committee Members: Nergis Mavalvala, Konrad Lehnert, Cindy Regal, Alan Mickelson, Charles Rogers.
Subjects/Keywords: LIGO; optomechanics; quantum displacement noise; radiation pressure; Optics; Physics
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APA (6th Edition):
Sankar, S. R. (2012). Approaching broadband quantum-limited displacement noise in a deformable optical cavity. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/82
Chicago Manual of Style (16th Edition):
Sankar, Shannon Reynier. “Approaching broadband quantum-limited displacement noise in a deformable optical cavity.” 2012. Doctoral Dissertation, University of Colorado. Accessed April 14, 2021.
https://scholar.colorado.edu/phys_gradetds/82.
MLA Handbook (7th Edition):
Sankar, Shannon Reynier. “Approaching broadband quantum-limited displacement noise in a deformable optical cavity.” 2012. Web. 14 Apr 2021.
Vancouver:
Sankar SR. Approaching broadband quantum-limited displacement noise in a deformable optical cavity. [Internet] [Doctoral dissertation]. University of Colorado; 2012. [cited 2021 Apr 14].
Available from: https://scholar.colorado.edu/phys_gradetds/82.
Council of Science Editors:
Sankar SR. Approaching broadband quantum-limited displacement noise in a deformable optical cavity. [Doctoral Dissertation]. University of Colorado; 2012. Available from: https://scholar.colorado.edu/phys_gradetds/82
University of Colorado
9.
Sirois, Adam Joseph.
Parametric Cavity Quantum Electrodynamics With Superconducting Circuits and Large Cavities.
Degree: PhD, Physics, 2016, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/169
► The research reported here details experimental progress toward future superconductor-based quantum computing technologies. Specifically, we present techniques for moving quantum information between various cavity…
(more)
▼ The research reported here details experimental progress toward future superconductor-based quantum computing technologies. Specifically, we present techniques for moving quantum information between various cavity resonators – spatially as well as between frequencies. Rather than using traditional resonant coupling though, we induce non-resonant coupling through parametric frequency conversion. This technology is mediated by chip-based, micro-fabricated, Josephson Junction circuits.
Parametric processes have the advantage over traditional coupling by allowing the constituents of the system – for example: cavity modes or qubits – to remain fixed in frequency, tuned to their optimal operation frequency, thereby avoiding unwanted resonant interactions. As the number of constituents grows – as quantum computing architectures expand to more and more bits – these techniques will become necessary to optimize performance.
Outside of the focus on quantum computation, these techniques have wide application for materials research, quantum optics, and extending traditionally optical-frequency experiments to microwave-frequencies. To that end, we demonstrate a hybrid quantum technology which expands the toolbox of superconducting quantum information to a new system, namely sapphire whispering gallery mode resonators. These resonators have been studied in the optical frequency domain, but here we demonstrate their usefulness at microwave frequencies.
All of the experiments in this dissertation should be considered proof-of-principle demonstrations of a future technology. Thus, we note when and where improvements for future devices will be necessary.
Advisors/Committee Members: Raymond Simmonds, John Price, Murray Holland, Charles Rogers, Alan Mickelson.
Subjects/Keywords: square cavities; sapphire WGM; coupler; Physics
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APA (6th Edition):
Sirois, A. J. (2016). Parametric Cavity Quantum Electrodynamics With Superconducting Circuits and Large Cavities. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/169
Chicago Manual of Style (16th Edition):
Sirois, Adam Joseph. “Parametric Cavity Quantum Electrodynamics With Superconducting Circuits and Large Cavities.” 2016. Doctoral Dissertation, University of Colorado. Accessed April 14, 2021.
https://scholar.colorado.edu/phys_gradetds/169.
MLA Handbook (7th Edition):
Sirois, Adam Joseph. “Parametric Cavity Quantum Electrodynamics With Superconducting Circuits and Large Cavities.” 2016. Web. 14 Apr 2021.
Vancouver:
Sirois AJ. Parametric Cavity Quantum Electrodynamics With Superconducting Circuits and Large Cavities. [Internet] [Doctoral dissertation]. University of Colorado; 2016. [cited 2021 Apr 14].
Available from: https://scholar.colorado.edu/phys_gradetds/169.
Council of Science Editors:
Sirois AJ. Parametric Cavity Quantum Electrodynamics With Superconducting Circuits and Large Cavities. [Doctoral Dissertation]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/phys_gradetds/169
University of Colorado
10.
Grover, Sachit.
Diodes for Optical Rectennas.
Degree: PhD, Electrical, Computer & Energy Engineering, 2011, University of Colorado
URL: https://scholar.colorado.edu/eeng_gradetds/17
► Two types of ultra-fast diode are fabricated, characterized, and simulated for use in optical rectennas. A rectenna consists of an antenna connected to a…
(more)
▼ Two types of ultra-fast diode are fabricated, characterized, and simulated for use in optical rectennas. A rectenna consists of an antenna connected to a diode in which the electromagnetic radiation received by the antenna is rectified in the diode. I have investigated metal/insulator/metal (MIM) tunnel diodes and a new, geometric diode for use in rectenna-based infrared detectors and solar cells. Factors influencing the performance of a rectenna are analyzed. These include DC and optical-frequency diode-characteristics, circuit parameters, signal amplitude, and coherence of incoming radiation.
To understand and increase the rectification response of MIM-based rectennas, I carry out an in-depth, simulation-based analysis of MIM diodes and design improved multi-insulator tunnel barriers. MIM diodes are fundamentally fast. However, from a small-signal circuit model the operating frequency of a rectenna is found to be limited by the diode's RC time constant. To overcome this limitation, I have designed and simulated a distributed rectifier that uses the MIM diode in a traveling-wave configuration. High-frequency characteristics of MIM diodes are obtained from a semiclassical theory for photon-assisted tunneling. Using this theory, the dependence of rectenna efficiency on diode characteristics and signal amplitude is evaluated along with the maximum achievable efficiency. A correspondence is established between the first-order semiclassical theory and the small-signal circuit model.
The RC time constant of MIM diodes is too large for efficient operation at near-infrared-to-visible frequencies. To this end, a new, planar rectifier that consists of an asymmetrically-patterned thin-film, is developed. The diode behavior in this device is attributed to the geometric asymmetry of the conductor. Geometric diodes are fabricated using graphene and measured for response to infrared illumination. To model the I(V) curve of geometric diodes, I have implemented a quantum mechanical simulation based on the tight-binding Hamiltonian. The simulated and the measured current-voltage characteristics are consistent with each other. I have also derived a semiclassical theory, analogous to the one for MIM diodes, for analyzing the optical response of geometric diodes.
Advisors/Committee Members: Garret Moddel, Charles Rogers, Robert McLeod, Wounjhang Park, Bart V. Zeghbroeck.
Subjects/Keywords: infrared detector; MIM diode; nanotechnology; photon-assisted transport; rectenna; solar cell; Electrical and Computer Engineering; Nanoscience and Nanotechnology; Physics
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APA (6th Edition):
Grover, S. (2011). Diodes for Optical Rectennas. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/eeng_gradetds/17
Chicago Manual of Style (16th Edition):
Grover, Sachit. “Diodes for Optical Rectennas.” 2011. Doctoral Dissertation, University of Colorado. Accessed April 14, 2021.
https://scholar.colorado.edu/eeng_gradetds/17.
MLA Handbook (7th Edition):
Grover, Sachit. “Diodes for Optical Rectennas.” 2011. Web. 14 Apr 2021.
Vancouver:
Grover S. Diodes for Optical Rectennas. [Internet] [Doctoral dissertation]. University of Colorado; 2011. [cited 2021 Apr 14].
Available from: https://scholar.colorado.edu/eeng_gradetds/17.
Council of Science Editors:
Grover S. Diodes for Optical Rectennas. [Doctoral Dissertation]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/eeng_gradetds/17
University of Colorado
11.
Kindel, William F.
Generation and Efficient Measurement of Single Photons Using Superconducting Circuits.
Degree: PhD, Physics, 2015, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/153
► In this thesis, I demonstrate and evaluate an on-demand source of single propagating microwaves photons. Working in the context of a quantum network, nodes…
(more)
▼ In this thesis, I demonstrate and evaluate an on-demand source of single propagating microwaves photons. Working in the context of a quantum network, nodes are connected via propagating, nonclassical states of the electromagnetic field. As such, preparing and detecting propagating quantum states is an essential task. I work with one particular node consisting of a microfabricated, effective two level system coupled to a microwave resonator and study its ability to produce propagating nonclassical states, such as single photon states. In principle, states generated by this node could be sent to other such nodes. However, I send them into a Josephson parametric amplifier (JPA) to characterize the source.
In particular, I discuss how to design and couple the two components that form my source: a fixed frequency transmon qubit and a 3D superconducting waveguide cavity. I demonstrate the ability to control of the dynamics of this combined system and implement a single photon generation protocol, which utilizes a single microwave control field that is far detuned from the photon emission frequency. To characterize the generation, I perform tomography on the propagating photon state to determine its density matrix
ρ. I perform repeated JPA-backed, linear measurements of the propagating state. Based on the histograms of my measurements, I infer a maximum single photon component
ρ11 = 0:36 ± 0:01. I characterize the imperfections of the photon generation and detection, including detection inefficiency and measurement backaction. I find that within uncertainty my measurements match my expectation.
Advisors/Committee Members: Konrad W. Lehnert, Murray Holland, Charles Rogers, James Thompson, Mathias Weber.
Subjects/Keywords: circuit; microwave; photon; qubit; cavity design; coupled system; Quantum Physics
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APA (6th Edition):
Kindel, W. F. (2015). Generation and Efficient Measurement of Single Photons Using Superconducting Circuits. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/153
Chicago Manual of Style (16th Edition):
Kindel, William F. “Generation and Efficient Measurement of Single Photons Using Superconducting Circuits.” 2015. Doctoral Dissertation, University of Colorado. Accessed April 14, 2021.
https://scholar.colorado.edu/phys_gradetds/153.
MLA Handbook (7th Edition):
Kindel, William F. “Generation and Efficient Measurement of Single Photons Using Superconducting Circuits.” 2015. Web. 14 Apr 2021.
Vancouver:
Kindel WF. Generation and Efficient Measurement of Single Photons Using Superconducting Circuits. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Apr 14].
Available from: https://scholar.colorado.edu/phys_gradetds/153.
Council of Science Editors:
Kindel WF. Generation and Efficient Measurement of Single Photons Using Superconducting Circuits. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/phys_gradetds/153
University of Colorado
12.
Christian, Theresa M.
Overcoming Limitations in Semiconductor Alloy Design.
Degree: PhD, 2018, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/262
► Inorganic semiconductors provide an astonishingly versatile, robust, and efficient platform for optoelectronic energy conversion devices. However, conventional alloys and growth regimes face materials challenges…
(more)
▼ Inorganic semiconductors provide an astonishingly versatile, robust, and efficient platform for optoelectronic energy conversion devices. However, conventional alloys and growth regimes face materials challenges that restrict the full potential of these devices. Novel alloy designs based on isoelectronic co-doping, metamorphic growth and controllable atomic ordering offer new pathways to practical and ultra-high-efficiency optoelectronic devices including solar cells and light-emitting diodes. Abnormal isoelectronic alloys of GaP
1-xBi
x, GaP
1-x-yBi
xN
y, and GaAs
1-xBi
x with unprecedented bismuth incorporation fractions and crystalline quality are explored in this thesis research. Comparative studies of several GaP
1-xBi
x and GaP
1-x-yBi
xN
y alloys demonstrate that the site-specific incorporation of bismuth during epitaxial growth is sensitive to growth temperature and has dramatic effects on carrier transfer processes in these alloys. Additionally, distinctive bismuth-related localized states are spectrally identified for the first time in samples of GaAs
1-xBi
x grown by laser-assisted epitaxial growth. These results address fundamental questions about the nature of bismuth-bismuth inter-impurity interactions. Finally, a metamorphic growth strategy for a novel light-emitting diode (LED) design is also discussed. This work utilized direct-bandgap Al
xIn
1-xP active layers with atomic ordering-based electron confinement to improve emission in the yellow and green spectral regions, where incumbent technologies are least effective, and demonstrated the feasibility of non-lattice-matched LED active materials for visible light emission.
Advisors/Committee Members: Angelo J. Mascarenhas, Daniel Dessau, Charles Rogers, Juliet Gopinath, Bart Van Zeghbroeck.
Subjects/Keywords: bismuth; dilute bismides; electronic structure; iii-v semiconductors; isoelectronic alloys; light-emitting diodes; Materials Science and Engineering; Physics
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Manager
APA (6th Edition):
Christian, T. M. (2018). Overcoming Limitations in Semiconductor Alloy Design. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/262
Chicago Manual of Style (16th Edition):
Christian, Theresa M. “Overcoming Limitations in Semiconductor Alloy Design.” 2018. Doctoral Dissertation, University of Colorado. Accessed April 14, 2021.
https://scholar.colorado.edu/phys_gradetds/262.
MLA Handbook (7th Edition):
Christian, Theresa M. “Overcoming Limitations in Semiconductor Alloy Design.” 2018. Web. 14 Apr 2021.
Vancouver:
Christian TM. Overcoming Limitations in Semiconductor Alloy Design. [Internet] [Doctoral dissertation]. University of Colorado; 2018. [cited 2021 Apr 14].
Available from: https://scholar.colorado.edu/phys_gradetds/262.
Council of Science Editors:
Christian TM. Overcoming Limitations in Semiconductor Alloy Design. [Doctoral Dissertation]. University of Colorado; 2018. Available from: https://scholar.colorado.edu/phys_gradetds/262
University of Colorado
13.
Widjonarko, Nicodemus Edwin.
Physics of Nickel Oxide Hole Transport Layer for Organic Photovoltaics Application.
Degree: PhD, Physics, 2013, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/99
► Organic photovoltaics (OPV) offers a potential for solar-electric power generation to be affordable. Crucial to OPV device performance is the incorporation of interlayers, ultra-thin…
(more)
▼ Organic photovoltaics (OPV) offers a potential for solar-electric power generation to be affordable. Crucial to OPV device performance is the incorporation of interlayers, ultra-thin films deposited between the photoactive material and the electrical contacts. These interlayers have various, targeted functionalities: optical window, encapsulation, or electronic bridge. The last category is known as "transport layers", and is the focus of this thesis.
In this thesis, we explore and investigate the physics that leads to improvements in OPV device performance when a transport layer is employed. We focus on the use of non-stoichiometric nickel oxide (NiO
x) as a hole transport layer (HTL) in poly(3-hexylthiophene):phenyl-C
61-butryric acid methyl ester (P3HT:PCBM) solar cells. NiO
x deposited by physical vapor deposition is chosen for this study because of its successful use as HTL, the ease to engineer its electronic properties by varying deposition parameters, and it leading to improved device lifetime.
Our initial studies indicate that the well-known \high work-function" rule is not adequate to explain the trends observed in the devices. The series of investigations discussed in this thesis reveal that band-offsets at the NiO
x / P3HT:PCBM interface need to be taken into account in order to explain the observed trends. Non-optimal band-offsets lead to either sigmoidal current-voltage characteristics or reduced photocurrent.
The optimal energy level alignment depends on the energy levels of the photo-active material, which are measurable. This means that an HTL material must be optimized for different photoactive material. A simple and practical set of rules are proposed to achieve this optimal energy level alignment for a given photoactive material. The rules not only include the pervasively-used \high work-function" rule, but also the impacts of band-offsets investigated in this work.
Advisors/Committee Members: Joseph J. Berry, Charles Rogers, David S. Ginley, Garry Rumbles, Ivan Smalyukh.
Subjects/Keywords: Band Alignment; Design Rule; Hole Transport Layer; Interface; Nickel Oxide; Organic Photovoltaics; Condensed Matter Physics; Materials Science and Engineering; Physics
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APA ·
Chicago ·
MLA ·
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CSE |
Export
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Manager
APA (6th Edition):
Widjonarko, N. E. (2013). Physics of Nickel Oxide Hole Transport Layer for Organic Photovoltaics Application. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/99
Chicago Manual of Style (16th Edition):
Widjonarko, Nicodemus Edwin. “Physics of Nickel Oxide Hole Transport Layer for Organic Photovoltaics Application.” 2013. Doctoral Dissertation, University of Colorado. Accessed April 14, 2021.
https://scholar.colorado.edu/phys_gradetds/99.
MLA Handbook (7th Edition):
Widjonarko, Nicodemus Edwin. “Physics of Nickel Oxide Hole Transport Layer for Organic Photovoltaics Application.” 2013. Web. 14 Apr 2021.
Vancouver:
Widjonarko NE. Physics of Nickel Oxide Hole Transport Layer for Organic Photovoltaics Application. [Internet] [Doctoral dissertation]. University of Colorado; 2013. [cited 2021 Apr 14].
Available from: https://scholar.colorado.edu/phys_gradetds/99.
Council of Science Editors:
Widjonarko NE. Physics of Nickel Oxide Hole Transport Layer for Organic Photovoltaics Application. [Doctoral Dissertation]. University of Colorado; 2013. Available from: https://scholar.colorado.edu/phys_gradetds/99
University of Colorado
14.
Christian, Theresa Marie.
Overcoming Limitations in Semiconductor Alloy Design.
Degree: PhD, Physics, 2017, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/217
► Inorganic semiconductors provide an astonishingly versatile, robust, and efficient platform for optoelectronic energy conversion devices. However, conventional alloys and growth regimes face materials challenges…
(more)
▼ Inorganic semiconductors provide an astonishingly versatile, robust, and efficient platform for optoelectronic energy conversion devices. However, conventional alloys and growth regimes face materials challenges that restrict the full potential of these devices. Novel alloy designs based on isoelectronic co-doping, metamorphic growth and controllable atomic ordering offer new pathways to practical and ultra-high-efficiency optoelectronic devices including solar cells and light-emitting diodes.
Abnormal isoelectronic alloys of GaP
1-xBi
x, GaP
1-x-yBi
xN
y, and GaAs
1-xBi
x with unprecedented bismuth incorporation fractions and crystalline quality are explored in this thesis research. Comparative studies of several GaP
1-xBi
x and GaP
1-x-yBi
xN
y alloys demonstrate that the site-specific incorporation of bismuth during epitaxial growth is sensitive to growth temperature and has dramatic effects on carrier transfer processes in these alloys. Additionally, distinctive bismuth-related localized states are spectrally identified for the first time in samples of GaAs
1-xBi
x grown by laser-assisted epitaxial growth. These results address fundamental questions about the nature of bismuth-bismuth inter-impurity interactions.
Finally, a metamorphic growth strategy for a novel light-emitting diode (LED) design is also discussed. This work utilized direct-bandgap Al
xIn
1-xP active layers with atomic ordering-based electron confinement to improve emission in the yellow and green spectral regions, where incumbent technologies are least effective, and demonstrated the feasibility of non-lattice-matched LED active materials for visible light emission.
Advisors/Committee Members: Angelo J. Mascarenhas, Daniel Dessau, Charles Rogers, Juliet Gopinath, Bart Van Zeghbroeck.
Subjects/Keywords: bismuth; dilute bismides; electronic structure; III-V semiconductors; isoelectronic alloys; light-emitting diodes; Materials Science and Engineering; Physics
Record Details
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Christian, T. M. (2017). Overcoming Limitations in Semiconductor Alloy Design. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/217
Chicago Manual of Style (16th Edition):
Christian, Theresa Marie. “Overcoming Limitations in Semiconductor Alloy Design.” 2017. Doctoral Dissertation, University of Colorado. Accessed April 14, 2021.
https://scholar.colorado.edu/phys_gradetds/217.
MLA Handbook (7th Edition):
Christian, Theresa Marie. “Overcoming Limitations in Semiconductor Alloy Design.” 2017. Web. 14 Apr 2021.
Vancouver:
Christian TM. Overcoming Limitations in Semiconductor Alloy Design. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Apr 14].
Available from: https://scholar.colorado.edu/phys_gradetds/217.
Council of Science Editors:
Christian TM. Overcoming Limitations in Semiconductor Alloy Design. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/phys_gradetds/217
University of Colorado
15.
Spettel, Karen Elizabeth.
Investigation of Conformational Control of Photoinduced Electron Transfer in Ruthenium Polypyridyl Dye-Sensitized Solar Cells.
Degree: PhD, Chemistry & Biochemistry, 2015, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/164
► To explore the impact of structure on photoinduced electron transfer processes, systematically tuned 4′-aryl-substituted terpyridyl ruthenium(II) complexes are synthesized and then studied in solution,…
(more)
▼ To explore the impact of structure on photoinduced electron transfer processes, systematically tuned 4′-aryl-substituted terpyridyl ruthenium(II) complexes are synthesized and then studied in solution, film, and device settings. These complexes are introduced in the framework of dye-sensitized solar cells (DSSCs)—a low cost alternative to conventional silicon-based devices. A monolayer of ruthenium chromophores attached to a mesoporous TiO
2 semiconductor is designed to efficiently absorb photons and initiate the separation of charge across a dye/semiconductor interface. Acting as a working electrode in a complete cell, this construction of sensitized TiO
2 particles allows for the conversion of photons to current. In our work, structural tuning is performed within the aryl-terpyridine ligands, by systematically introducing methyl substituents at the ortho positions of the aryl moiety in order to explore dynamical electron transfer coupling at ruthenium/TiO
2 interfaces.
First, syntheses, electrochemical potentials, static emission, and temperature-dependent excited-state lifetimes of several 4′-aryl-substituted terpyridyl complexes of ruthenium(II) are presented. In these solution phase studies, the power of structural tuning manifests primarily with a 14-fold decrease in the excited-state lifetime of dimethylated species relative to unsubstituted aryl-terpyridine species. Next, an overview of the materials and procedures utilized to make complete DSSCs is presented. In an effort to determine the implications of structural tuning of these complexes within the DSSCs, total solar power conversion efficiency measurements are performed. These are then deconstructed to better understand the fundamental processes and how they impact light-to-current conversion. Injection yields are identified as the primary factor limiting the efficiencies of these ruthenium terpyridyl DSSCs. The final chapter presents an investigation of the kinetics of charge recombination—an energy-wasting back electron transfer process at play in photoinduced charge-separated processes. Transient absorption spectroscopy is applied to sensitized TiO
2 films in an electrochemical setup simulating device conditions. The addition of methyl steric bulk is found to inhibit charge recombination, with measured recombination lifetimes increasing by over 12-fold across the series of structurally-tuned complexes. If injection yields can be improved, the structural tuning of recombination rate constants may be an important design rule for improving solar conversion efficiency in solar cells and water splitting devices.
Advisors/Committee Members: Niels H. Damrauer, Cortlandt G. Pierpont, Gordana Dukovic, Steven M. George, Charles Rogers.
Subjects/Keywords: Conformational Control; Dye Sensitized Solar Cells; Electron Transfer; Ruthenium Polypyridyl; Steric Hindrance; Physical Chemistry
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APA ·
Chicago ·
MLA ·
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CSE |
Export
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APA (6th Edition):
Spettel, K. E. (2015). Investigation of Conformational Control of Photoinduced Electron Transfer in Ruthenium Polypyridyl Dye-Sensitized Solar Cells. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/164
Chicago Manual of Style (16th Edition):
Spettel, Karen Elizabeth. “Investigation of Conformational Control of Photoinduced Electron Transfer in Ruthenium Polypyridyl Dye-Sensitized Solar Cells.” 2015. Doctoral Dissertation, University of Colorado. Accessed April 14, 2021.
https://scholar.colorado.edu/chem_gradetds/164.
MLA Handbook (7th Edition):
Spettel, Karen Elizabeth. “Investigation of Conformational Control of Photoinduced Electron Transfer in Ruthenium Polypyridyl Dye-Sensitized Solar Cells.” 2015. Web. 14 Apr 2021.
Vancouver:
Spettel KE. Investigation of Conformational Control of Photoinduced Electron Transfer in Ruthenium Polypyridyl Dye-Sensitized Solar Cells. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Apr 14].
Available from: https://scholar.colorado.edu/chem_gradetds/164.
Council of Science Editors:
Spettel KE. Investigation of Conformational Control of Photoinduced Electron Transfer in Ruthenium Polypyridyl Dye-Sensitized Solar Cells. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/chem_gradetds/164
University of Colorado
16.
Park, Samuel D.
Femtosecond and Two-Dimensional Spectroscopy of Lead Chalcogenide Quantum Dots.
Degree: PhD, Chemistry & Biochemistry, 2015, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/175
► Quantum dots have applications in lighting displays and in biomedical imaging, and potential applications in next generation photovoltaics. The fine structure, optical inhomogeneity, coupling…
(more)
▼ Quantum dots have applications in lighting displays and in biomedical imaging, and potential applications in next generation photovoltaics. The fine structure, optical inhomogeneity, coupling between excitons, and exciton dephasing rates are important to quantify because they affect the optical properties of quantum dots. These observables are encrypted in linear absorption lineshapes but can be measured with nonlinear spectroscopy.
The first two-dimensional (2D) Fourier transform spectra of lead chalcogenide quantum dots in the short-wave infrared are presented. With the additional dimension afforded by 2D spectra, linewidths from homogeneous and inhomogeneous broadening can be separated. Simulations to model the experimental 2D spectra are performed at long relaxation times to extract the optical inhomogeneity of a PbSe quantum dot ensemble. Additional information can be determined more accurately from 2D spectra than from transient absorption measurements. Specifically, the simulation of experimental 2D spectra shows that the excited state absorption redshift, which has been attributed to the bi-exciton binding energy, is larger than previously reported results, suggesting new interpretations.
Pump-probe polarization anisotropy measurements with 15 fs pulse durations are employed to investigate the electronic structure of chlorine-passivated PbS quantum dots at the bandgap. The measurement of the initial anisotropy required the removal of unwanted signal contribution from cross-phase modulation. The presence of cross-phase modulation motivated the calculation, simulation, and measurement of this signal for spectrally resolved pump-probe transients and two-dimensional Fourier transform spectroscopy. The initial anisotropy contains information about both bi-exciton states and some hot single exciton states, and the time dependence quantifies the timescale of intervalley scattering. Our results for PbS quantum dots indicate a lower initial anisotropy than expected from the effective mass approximations for PbS quantum dots with a rapid loss of any anisotropy in less than 20 fs.
Advisors/Committee Members: David M. Jonas, Robert P. Parson, Veronica Vaida, Charles Rogers, Niels H. Damrauer.
Subjects/Keywords: quantum dots; photovoltaics; fourier transform spectra; chalcogenide quantum dots; cross-phase modulation; Physical Chemistry
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
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APA (6th Edition):
Park, S. D. (2015). Femtosecond and Two-Dimensional Spectroscopy of Lead Chalcogenide Quantum Dots. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/175
Chicago Manual of Style (16th Edition):
Park, Samuel D. “Femtosecond and Two-Dimensional Spectroscopy of Lead Chalcogenide Quantum Dots.” 2015. Doctoral Dissertation, University of Colorado. Accessed April 14, 2021.
https://scholar.colorado.edu/chem_gradetds/175.
MLA Handbook (7th Edition):
Park, Samuel D. “Femtosecond and Two-Dimensional Spectroscopy of Lead Chalcogenide Quantum Dots.” 2015. Web. 14 Apr 2021.
Vancouver:
Park SD. Femtosecond and Two-Dimensional Spectroscopy of Lead Chalcogenide Quantum Dots. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Apr 14].
Available from: https://scholar.colorado.edu/chem_gradetds/175.
Council of Science Editors:
Park SD. Femtosecond and Two-Dimensional Spectroscopy of Lead Chalcogenide Quantum Dots. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/chem_gradetds/175
. 
Open Access Theses and Dissertations