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University of Colorado
1.
Chen, Cong.
Attosecond Light Pulses and Attosecond Electron Dynamics Probed Using Angle-Resolved Photoelectron Spectroscopy.
Degree: PhD, 2018, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/260 
► Recent advances in the generation and control of attosecond light pulses have opened up new opportunities for the real-time observation of sub-femtosecond (1 fs =…
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▼ Recent advances in the generation and control of attosecond light pulses have opened up new opportunities for the real-time observation of sub-femtosecond (1 fs = 10
-15 s) electron dynamics in gases and solids. Combining attosecond light pulses with angle-resolved photoelectron spectroscopy (atto-ARPES) provides a powerful new technique to study the influence of material band structure on attosecond electron dynamics in materials. Electron dynamics that are only now accessible include the lifetime of far-above-bandgap excited electronic states, as well as fundamental electron interactions such as scattering and screening. In addition, the same atto-ARPES technique can also be used to measure the temporal structure of complex coherent light fields. In this thesis, I present four experiments utilizing atto-ARPES to provide new insights into the generation and characterization of attosecond light pulses, as well as the attosecond electron dynamics in transition metals. First, I describe a new method to extend attosecond metrology techniques to the reconstruction of circularly polarized attosecond light pulses for the first time. Second, I show that by driving high harmonics with a two-color linearly polarized laser field, quasi-isolated attosecond pulses are generated because the phase matching window is confined. Third, I present the first measurement of lifetimes for photoelectrons that are born into free-electron-like states compared with those that are excited into unoccupied excited states in the band structure of a material (Ni(111)). The finite excited-state lifetime causes a ≈200 as delay in the emission of photoelectrons. Finally, I describe direct time-domain studies of electron-electron interactions in transition metals with both simple and complex Fermi surfaces. In particular, I show the influence of electron-electron scattering and screening on the lifetime of photoelectrons.
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Andreas Becker.
Subjects/Keywords: attosecond; electron dynamics; euv; high harmonic generation; photoemission; ultrafast; Dynamical Systems; Physics
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APA (6th Edition):
Chen, C. (2018). Attosecond Light Pulses and Attosecond Electron Dynamics Probed Using Angle-Resolved Photoelectron Spectroscopy. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/260
Chicago Manual of Style (16th Edition):
Chen, Cong. “Attosecond Light Pulses and Attosecond Electron Dynamics Probed Using Angle-Resolved Photoelectron Spectroscopy.” 2018. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/260.
MLA Handbook (7th Edition):
Chen, Cong. “Attosecond Light Pulses and Attosecond Electron Dynamics Probed Using Angle-Resolved Photoelectron Spectroscopy.” 2018. Web. 05 Mar 2021.
Vancouver:
Chen C. Attosecond Light Pulses and Attosecond Electron Dynamics Probed Using Angle-Resolved Photoelectron Spectroscopy. [Internet] [Doctoral dissertation]. University of Colorado; 2018. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/260.
Council of Science Editors:
Chen C. Attosecond Light Pulses and Attosecond Electron Dynamics Probed Using Angle-Resolved Photoelectron Spectroscopy. [Doctoral Dissertation]. University of Colorado; 2018. Available from: https://scholar.colorado.edu/phys_gradetds/260
University of Colorado
2.
Zusin, Dmitriy.
Ultrafast Dynamics of Magnetic Multilayer Films: Magneto-Optical Spectroscopy and Resonant Scattering in the Extreme Ultraviolet and Soft X-Ray Spectral Regions.
Degree: PhD, 2018, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/283
► This thesis focuses on studying ferromagnetic thin films with high temporal and spatial resolution using tabletop extreme ultraviolet (EUV) light sources based on high harmonic…
(more)
▼ This thesis focuses on studying ferromagnetic thin films with high temporal and spatial resolution using tabletop extreme ultraviolet (EUV) light sources based on high harmonic generation (HHG) and ultrafast soft X-rays from a free-electron laser. In Chapter 4, a new magneto-optical technique is developed. It allows a direct measurement of the full resonant complex EUV magneto-optical permittivity on a tabletop and thus, through a comparison with first principles calculations, is capable of capturing the microscopic mechanisms of ultrafast laser-induced demagnetization. It is found that, in Co, the demagnetization response is dominated by magnon excitations with possible smaller contributions from other mechanisms. Chapter 5 discusses the development of an efficient approach for resonant magnetic scattering (RMS) with a tabletop HHG source. This approach is used to study magnetic textures with spatial resolution. In an external magnetic field, a transition from a disordered network of stripe domains to an ordered lattice of magnetic vortices is observed in an Fe-Gd thin film. Chapter 6 presents the results of a dynamic soft X-ray RMS experiment on a disordered domain network performed at the Linear Coherent Light Source (LCLS). By directly applying the experimental data to a carefully simulated domain pattern, laser-induced transient changes in the domains are captured in real space, and strong non-uniformities in the demagnetization across the sample are observed. These non-uniformities are attributed to a combined effect of ultrafast spin-polarized currents and a gradient in the pump absorption throughout the thickness of the sample. Chapter 7 provides an outlook towards time-resolved lensless magnetic spectro-microscopy with HHG sources.
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Thomas J. Silva.
Subjects/Keywords: extreme ultraviolet; soft x-ray; high harmonic generation; resonant magnetic scattering; magneto-optical spectroscopy; Materials Science and Engineering; Optics; Physics
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APA (6th Edition):
Zusin, D. (2018). Ultrafast Dynamics of Magnetic Multilayer Films: Magneto-Optical Spectroscopy and Resonant Scattering in the Extreme Ultraviolet and Soft X-Ray Spectral Regions. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/283
Chicago Manual of Style (16th Edition):
Zusin, Dmitriy. “Ultrafast Dynamics of Magnetic Multilayer Films: Magneto-Optical Spectroscopy and Resonant Scattering in the Extreme Ultraviolet and Soft X-Ray Spectral Regions.” 2018. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/283.
MLA Handbook (7th Edition):
Zusin, Dmitriy. “Ultrafast Dynamics of Magnetic Multilayer Films: Magneto-Optical Spectroscopy and Resonant Scattering in the Extreme Ultraviolet and Soft X-Ray Spectral Regions.” 2018. Web. 05 Mar 2021.
Vancouver:
Zusin D. Ultrafast Dynamics of Magnetic Multilayer Films: Magneto-Optical Spectroscopy and Resonant Scattering in the Extreme Ultraviolet and Soft X-Ray Spectral Regions. [Internet] [Doctoral dissertation]. University of Colorado; 2018. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/283.
Council of Science Editors:
Zusin D. Ultrafast Dynamics of Magnetic Multilayer Films: Magneto-Optical Spectroscopy and Resonant Scattering in the Extreme Ultraviolet and Soft X-Ray Spectral Regions. [Doctoral Dissertation]. University of Colorado; 2018. Available from: https://scholar.colorado.edu/phys_gradetds/283
University of Colorado
3.
Lock, Robynne Marie.
High Harmonic Generation from Rotationally Excited Molecules.
Degree: PhD, Physics, 2011, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/29
► High harmonic generation (HHG) is understood through a three-step model. A strong laser field ionizes an atom or molecule. The free electron propagates in…
(more)
▼ High harmonic generation (HHG) is understood through a three-step model. A strong laser field ionizes an atom or molecule. The free electron propagates in the laser field and may recombine with the atom or molecule leading to the generation of extreme ultraviolet or soft x-ray light at odd harmonics of the fundamental. Since the wavelength of the recombining electron is on the order of internuclear distances in molecules, HHG acts as a probe of molecular structure and dynamics. Conversely, control of the molecules leads to control of the properties (intensity, phase, and polarization) of the harmonic emission. Rotationally exciting molecules provides field-free molecular alignment at time intervals corresponding to fractions of the rotational period of the molecule. Alignment is necessary for understanding how the harmonic emission depends on molecular structure and alignment. Additionally, HHG acts as a probe of the rotational wavepackets. This thesis reports three experiments on HHG from rotationally excited molecules. Before we can use HHG as a probe of complex molecular dynamics or control harmonic properties through molecules, the harmonic emission from aligned, linear molecules must first be understood. To that end, the first experiment measures the intensity and phase of harmonics generated from N
2O and N
2 near times of strong alignment revealing interferences during recombination. The second experiment demonstrates HHG as a sensitive probe of rotational wavepacket dynamics in CO
2 and N
2O, revealing new revival features not detected by any other probe. The final experiment focuses on understanding and controlling the polarization state of the harmonic emission. Generating elliptically polarized harmonics would be very useful for probing molecular and materials systems. We observe an elliptical dichroism in polarization-resolved measurements of the harmonic emission from aligned N
2 and CO
2 molecules, revealing evidence for electron-hole dynamics between the times of ionization and recombination.
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Andreas Becker.
Subjects/Keywords: high harmonic generation; strong field physics; ultrafast phenomena; Atomic, Molecular and Optical Physics
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APA (6th Edition):
Lock, R. M. (2011). High Harmonic Generation from Rotationally Excited Molecules. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/29
Chicago Manual of Style (16th Edition):
Lock, Robynne Marie. “High Harmonic Generation from Rotationally Excited Molecules.” 2011. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/29.
MLA Handbook (7th Edition):
Lock, Robynne Marie. “High Harmonic Generation from Rotationally Excited Molecules.” 2011. Web. 05 Mar 2021.
Vancouver:
Lock RM. High Harmonic Generation from Rotationally Excited Molecules. [Internet] [Doctoral dissertation]. University of Colorado; 2011. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/29.
Council of Science Editors:
Lock RM. High Harmonic Generation from Rotationally Excited Molecules. [Doctoral Dissertation]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/phys_gradetds/29
University of Colorado
4.
La-o-vorakiat, Chan.
Element-Selective Ultrafast Magnetization Dynamics with a Tabletop Light Source.
Degree: PhD, Physics, 2011, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/46
► Next-generation hard-disk drives will require smaller magnetic bits and faster magnetization switching; hence, better understanding of nanoscale magnetic material is one of the key…
(more)
▼ Next-generation hard-disk drives will require smaller magnetic bits and faster magnetization switching; hence, better understanding of nanoscale magnetic material is one of the key factors in developing of these devices. Here, I present the first ultrafast magnetization dynamics studies by use of extreme ultraviolet radiation from a tabletop high-harmonic generation source. This new probing technique offers three advantages over conventional ones: ultrafast time resolution, element selectivity, and the tabletop size.
I report three experiments showing that high harmonics are a powerful tool for probing magnetization in magnetic materials. First, our group measures simultaneously the magnetizations of Ni and Fe in Permalloy using the transverse magneto-optical Kerr effect. Second, we study laser-induced demagnetization dynamics in two ferromagnetic alloys: Permalloy and Permalloy-Cu. Contrary to a common expectation that the dynamics in strong exchange-coupled alloys would be identical, we discover that the magnetization of Fe decays earlier than that of Ni during the first 60 fs. To explain this delay, we propose a simple model incorporating a finite exchange-time factor into the magnetization rate equations. Finally, to confirm the observed sequence of dynamics in alloys, we conduct the magnetization study of elemental Fe and Ni with identical experimental conditions. The results indicate that the order of demagnetizations in the elemental forms is the same as that in Permalloy: Fe demagnetizes faster than Ni does.
Advisors/Committee Members: Henry C. Kapteyn, Margaret M. Murnane, Thomas J. Silva.
Subjects/Keywords: Demagnetization Dynamics; High-harmonic Generation; Magnetism; Ultrafast; Condensed Matter Physics
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APA (6th Edition):
La-o-vorakiat, C. (2011). Element-Selective Ultrafast Magnetization Dynamics with a Tabletop Light Source. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/46
Chicago Manual of Style (16th Edition):
La-o-vorakiat, Chan. “Element-Selective Ultrafast Magnetization Dynamics with a Tabletop Light Source.” 2011. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/46.
MLA Handbook (7th Edition):
La-o-vorakiat, Chan. “Element-Selective Ultrafast Magnetization Dynamics with a Tabletop Light Source.” 2011. Web. 05 Mar 2021.
Vancouver:
La-o-vorakiat C. Element-Selective Ultrafast Magnetization Dynamics with a Tabletop Light Source. [Internet] [Doctoral dissertation]. University of Colorado; 2011. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/46.
Council of Science Editors:
La-o-vorakiat C. Element-Selective Ultrafast Magnetization Dynamics with a Tabletop Light Source. [Doctoral Dissertation]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/phys_gradetds/46
University of Colorado
5.
Arpin, Paul Christopher.
Generation and Characterization of Coherent Soft X-Ray Light with High Harmonic Generation.
Degree: PhD, Physics, 2011, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/51
► High order harmonic generation (HHG) is a source of bright, ultrafast, fully spatially coherent, extreme ultraviolet (EUV) light with applications in ultrafast molecular and…
(more)
▼ High order harmonic generation (HHG) is a source of bright, ultrafast, fully spatially coherent, extreme ultraviolet (EUV) light with applications in ultrafast molecular and materials spectroscopy, element selective ultrafast magnetic dynamics, nano-thermal heat transport and high-resolution imaging. Harmonics have been generated up to a few keV, but the flux has been very low past 100 eV. Thus, applications of HHG have focused on the EUV region. By enhancing the brightness of harmonics at higher energies, we can expand the applications of HHG to the soft x-ray region of the spectrum. The "water window" is a particularly important region of the spectrum for high resolution biological imaging. In this region, between 284 and 540 eV, water is an order of magnitude more transparent than carbon, providing contrast between various biological materials. This thesis presents two methods to improve the brightness of harmonics in the water window. In the first, harmonics were generated from doubly ionized argon, which extended the cutoff photon energy to 540 eV, 200 eV higher than previously demonstrated from argon. The second method used the recently developed mid-infrared phase-matching technique to fully phase match the harmonic process at soft x-ray photon energies up to 540 eV which increased the brightness of harmonics in the water window by three orders of magnitude. This source was then characterized with the first spatial coherence measurement of any compact light source in this spectral range. In the future, this source can be used for high resolution, element specific, coherent imaging in the water window and ultrafast transient absorption spectroscopy in molecules and materials.
Advisors/Committee Members: Henry C. Kapteyn, Margaret M. Murnane, Andreas Becker.
Subjects/Keywords: Atomic, Molecular and Optical Physics; Optics; Physics
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APA (6th Edition):
Arpin, P. C. (2011). Generation and Characterization of Coherent Soft X-Ray Light with High Harmonic Generation. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/51
Chicago Manual of Style (16th Edition):
Arpin, Paul Christopher. “Generation and Characterization of Coherent Soft X-Ray Light with High Harmonic Generation.” 2011. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/51.
MLA Handbook (7th Edition):
Arpin, Paul Christopher. “Generation and Characterization of Coherent Soft X-Ray Light with High Harmonic Generation.” 2011. Web. 05 Mar 2021.
Vancouver:
Arpin PC. Generation and Characterization of Coherent Soft X-Ray Light with High Harmonic Generation. [Internet] [Doctoral dissertation]. University of Colorado; 2011. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/51.
Council of Science Editors:
Arpin PC. Generation and Characterization of Coherent Soft X-Ray Light with High Harmonic Generation. [Doctoral Dissertation]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/phys_gradetds/51
University of Colorado
6.
Li, Qing.
Study of Nanoscale Phonon Dynamics using Ultrafast Coherent Extreme Ultraviolet Beams.
Degree: PhD, Physics, 2011, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/54
► Phonon transport is essential in both understanding and characterizing materials, particularly in nanoscale systems. In this thesis, I use coherent ultrafast extreme ultraviolet (EUV)…
(more)
▼ Phonon transport is essential in both understanding and characterizing materials, particularly in nanoscale systems. In this thesis, I use coherent ultrafast extreme ultraviolet (EUV) beams from high-order harmonic generation, to study the dynamics of photoacoustics and energy-carrying phonons at the nanoscale. I first generate and detect short-wavelength photoacoustic waves by impulsively heating sub-optical phononic crystals with an infrared laser. By monitoring the diffraction dynamics of EUV beams I observe the shortest-wavelength surface acoustic waves to date at 35 nm, corresponding to an interface layer sensitivity of sub-10 nm. I also achieve coherent control of SAW generation and preferentially enhance higher-order SAWs which allows us to reduce the generated SAW wavelength by a factor of two for a defined nanostructure period. I apply this photoacoustic technique to thin film metrology metrology: by generating nanoscale longitudinal and surface acoustic waves simultaneously, I am able to characterize the mechanical properties of ultrathin film samples. Secondly, I study thermal transport dynamics in nano-to-bulk systems where phonons are heat carriers. I first observed quasi-ballistic thermal transport in 1D nano-to-bulk systems, and detect a stronger ballistic effect in 2D nanostructured materials. Temperature- and polarization-dependent experiments are also reported in this thesis. Furthermore, I was able to make a first attempt in dynamic thermal imaging using coherent diffraction of EUV beams.
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Ronggui Yang.
Subjects/Keywords: ballistic effect; extreme ultraviolet; high harmonic generation; photoacoustic; surface acoustic wave; thermal transport; Physics
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APA (6th Edition):
Li, Q. (2011). Study of Nanoscale Phonon Dynamics using Ultrafast Coherent Extreme Ultraviolet Beams. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/54
Chicago Manual of Style (16th Edition):
Li, Qing. “Study of Nanoscale Phonon Dynamics using Ultrafast Coherent Extreme Ultraviolet Beams.” 2011. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/54.
MLA Handbook (7th Edition):
Li, Qing. “Study of Nanoscale Phonon Dynamics using Ultrafast Coherent Extreme Ultraviolet Beams.” 2011. Web. 05 Mar 2021.
Vancouver:
Li Q. Study of Nanoscale Phonon Dynamics using Ultrafast Coherent Extreme Ultraviolet Beams. [Internet] [Doctoral dissertation]. University of Colorado; 2011. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/54.
Council of Science Editors:
Li Q. Study of Nanoscale Phonon Dynamics using Ultrafast Coherent Extreme Ultraviolet Beams. [Doctoral Dissertation]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/phys_gradetds/54
University of Colorado
7.
Chen, Ming-Chang.
Modifying Driving Laser Wavelength to Generate Coherent, Ultrafast X-rays from Phase-Matched High-Order Harmonics.
Degree: PhD, Physics, 2012, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/60
► Recently, ultrafast, coherent X-ray science and technology has received a lot of attentions, especially with respect to tabletop X-rays produced by high harmonic generation…
(more)
▼ Recently, ultrafast, coherent X-ray science and technology has received a lot of attentions, especially with respect to tabletop X-rays produced by high harmonic generation (HHG). The femtosecond-to-attosecond X-ray pulse enables the dynamics of chemical reactions, nano-materials and bio-molecular systems to be studied with unprecedented temporal and spatial resolution. However, the bright HHG light source is limited to < 150 eV spectral region due to phase-mismatch issue and the lack of the right driving laser wavelength. Development of phase-matching scheme and different-wavelength lasers for extending bright HHG to shorter wavelengths becomes a challenge. Over the past five years, we essentially solve the high-harmonic phase matching problem using longer driving wavelengths. Our experimental results have shown that full phase matching of HHG scales very strongly with wavelength of the driving laser, making it possible for the first time to obtain bright phase-matched emission to the 0.5 keV using a 2 mum laser and the keV using a 3.9 mum laser with a conversion efficiency >1000 times that previously reported. Their supercontinuum bandwidths are capable of generation extremely short pulses down to single digit attoseconds ( 10 – 18 sec). This timescale is remarkable in that it approaches a new regime where light transit times approach atomic dimensions. On the other hand, by using a shorter wavelength of driving laser (0.4 um), we also optimized the HHG flux ˜ 10 times brighter than before in the EUV spectral region between 45 and 60 eV. We found that the most substantial HHG enhancement arises when the right combination of the laser wavelengths, gas species and gas pressures. A high flux tabletop coherent X-ray beam line is feasible to implement, for applications in biological and materials imaging, or as a seeding source for a free-electron laser amplifier.
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Steven Cundiff.
Subjects/Keywords: Optics; Physics
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APA ·
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APA (6th Edition):
Chen, M. (2012). Modifying Driving Laser Wavelength to Generate Coherent, Ultrafast X-rays from Phase-Matched High-Order Harmonics. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/60
Chicago Manual of Style (16th Edition):
Chen, Ming-Chang. “Modifying Driving Laser Wavelength to Generate Coherent, Ultrafast X-rays from Phase-Matched High-Order Harmonics.” 2012. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/60.
MLA Handbook (7th Edition):
Chen, Ming-Chang. “Modifying Driving Laser Wavelength to Generate Coherent, Ultrafast X-rays from Phase-Matched High-Order Harmonics.” 2012. Web. 05 Mar 2021.
Vancouver:
Chen M. Modifying Driving Laser Wavelength to Generate Coherent, Ultrafast X-rays from Phase-Matched High-Order Harmonics. [Internet] [Doctoral dissertation]. University of Colorado; 2012. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/60.
Council of Science Editors:
Chen M. Modifying Driving Laser Wavelength to Generate Coherent, Ultrafast X-rays from Phase-Matched High-Order Harmonics. [Doctoral Dissertation]. University of Colorado; 2012. Available from: https://scholar.colorado.edu/phys_gradetds/60
University of Colorado
8.
Galloway, Benjamin Robert.
High-Order Harmonic Generation Driven by Mid-Infrared Laser Light.
Degree: PhD, Physics, 2017, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/233
► Light is a powerful tool for making observations of the physical world. In particular, light in the extreme ultraviolet (EUV) and X-ray regimes enable…
(more)
▼ Light is a powerful tool for making observations of the physical world. In particular, light in the extreme ultraviolet (EUV) and X-ray regimes enable unique and higher resolution measurements than is possible using longer wavelengths. A relatively new technique called high-order harmonic generation (HHG) provides a route for scientists to produce light in these useful spectral ranges, starting with lasers operating at more accessible wavelengths. HHG has been successfully applied to a number of applications including high resolution microscopy, spectroscopy, and measurements of magnetism, thermal transport, and molecular structure. This dissertation covers several illuminating studies of HHG in the temporal and spectral domains when the process is driven by long wavelength, mid-infrared light. Interestingly, the characteristics of the harmonic emission are highly dependent on the driving laser parameters and geometries. As the driving laser wavelength is increased, the harmonic cutoff and bandwidth naturally broaden, while the emitted pulse train reduces in length until a single isolated burst of phase-matched harmonics with sub-femtosecond duration is achieved. This trend is experimentally verified by performing an electric field autocorrelation of the harmonic emission. The resulting HHG supercontinuum has particular utility in X-ray absorption fine structure spectroscopies, where the nanoscale lattice structure can be probed. These spectroscopies have been performed on polymer, scandium, and iron samples using the broadest HHG bandwidths achieved to date, extending up to 1.6 keV. Pushing this harmonic cutoff further would conventionally require the use of longer wavelength drivers approaching the far-infrared regime. However, long driving wavelengths can also result in relativistic effects, resulting in longitudinal Lorentz drifts that could cause the HHG process to be inhibited. A theoretical accounting of all of the forces involved does not indicate HHG would be shut off entirely, however, and it is possible for HHG to occur even with driving wavelengths beyond 10 µm and harmonic cutoffs in the hard X-ray regime. The use of cylindrical vector beams or multi-beam geometries can also be used to compensate for relativistic effects, as well as to create new phase-matching conditions for sum and difference frequency processes. Through high-order difference frequency generation in a two-beam noncollinear geometry, it is predicted that the conventional phase-matching limitations could be significantly exceeded, opening up the possibility to use visible drivers to reach the soft X-ray regime or further. Pushing the limits of the HHG spectral characteristics would inevitably enable new levels of capability for its applications. The investigations presented here will follow a progression from shorter to longer wavelengths as drivers for the HHG process, starting with experiments using the most commonly used Ti:sapphire wavelength of 800 nm, moving to 1.3 µm and 2.0 µm, then up to 3.9 µm, and ultimately…
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Michael Litos.
Subjects/Keywords: extreme ultraviolet light; high harmonic generation; laser physics; mid-infrared light; nonlinear optics; x-ray light; Atomic, Molecular and Optical Physics; Optics; Physics
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APA (6th Edition):
Galloway, B. R. (2017). High-Order Harmonic Generation Driven by Mid-Infrared Laser Light. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/233
Chicago Manual of Style (16th Edition):
Galloway, Benjamin Robert. “High-Order Harmonic Generation Driven by Mid-Infrared Laser Light.” 2017. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/233.
MLA Handbook (7th Edition):
Galloway, Benjamin Robert. “High-Order Harmonic Generation Driven by Mid-Infrared Laser Light.” 2017. Web. 05 Mar 2021.
Vancouver:
Galloway BR. High-Order Harmonic Generation Driven by Mid-Infrared Laser Light. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/233.
Council of Science Editors:
Galloway BR. High-Order Harmonic Generation Driven by Mid-Infrared Laser Light. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/phys_gradetds/233
University of Colorado
9.
Gopalakrishnan, Maithreyi.
Comparative Study of Laser-Induced Ultrafast Demagnetization Dynamics in Fe, Co, and Ni.
Degree: MS, Physics, 2016, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/171
► Even twenty years after the discovery of ultrafast demagnetization of ferromagnetic materials induced by a femtosecond laser pulse there is still an ongoing debate…
(more)
▼ Even twenty years after the discovery of ultrafast demagnetization of ferromagnetic materials induced by a femtosecond laser pulse there is still an ongoing debate about the mechanisms that drive the process. Surprisingly, a comprehensive study that compares demagnetization dynamics in different materials on equal footing is lacking. Yet, the scientific community would greatly benefit from such study. We fill this gap by performing a systematic comparison of ultrafast demagnetization behavior in Iron, Cobalt and Nickel, the simplest itinerant ferromagnets, under a wide range of pump fluences. In this experiment, we utilize a tabletop broadband extreme ultraviolet source to probe magnetization dynamics at the M2,3 absorption edges of these three elements using the transverse magneto-optical Kerr effect. The obtained data can be used to inform theory and, thereby, assist in resolving the remaining questions about the micro- and macroscopic mechanisms behind ultrafast laser-induced magnetization dynamics in materials.
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Heather Lewandowski, Steven J. Pollock.
Subjects/Keywords: Harmonic; Laser; Magnetism; Spin; Temperature; Ultrafast; Condensed Matter Physics; Optics
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APA (6th Edition):
Gopalakrishnan, M. (2016). Comparative Study of Laser-Induced Ultrafast Demagnetization Dynamics in Fe, Co, and Ni. (Masters Thesis). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/171
Chicago Manual of Style (16th Edition):
Gopalakrishnan, Maithreyi. “Comparative Study of Laser-Induced Ultrafast Demagnetization Dynamics in Fe, Co, and Ni.” 2016. Masters Thesis, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/171.
MLA Handbook (7th Edition):
Gopalakrishnan, Maithreyi. “Comparative Study of Laser-Induced Ultrafast Demagnetization Dynamics in Fe, Co, and Ni.” 2016. Web. 05 Mar 2021.
Vancouver:
Gopalakrishnan M. Comparative Study of Laser-Induced Ultrafast Demagnetization Dynamics in Fe, Co, and Ni. [Internet] [Masters thesis]. University of Colorado; 2016. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/171.
Council of Science Editors:
Gopalakrishnan M. Comparative Study of Laser-Induced Ultrafast Demagnetization Dynamics in Fe, Co, and Ni. [Masters Thesis]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/phys_gradetds/171
University of Colorado
10.
Grennell, Amanda N.
Photophysics and Electron Transfer Dynamics of Type-II and Quasi Type-II Heterostructure Nanocrystals.
Degree: PhD, 2017, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/269
► Type-II and quasi type-II heterostructure nanocrystals are known to exhibit extended excited-state lifetimes compared to their single material counterparts because of reduced wavefunction overlap between…
(more)
▼ Type-II and quasi type-II heterostructure nanocrystals are known to exhibit extended excited-state lifetimes compared to their single material counterparts because of reduced wavefunction overlap between the electron and hole. Thus, type-II heterostructures are promising materials for solar-to-fuel conversion, as extended excited-state lifetimes make transfer of charges to a catalyst more competitive with intrinsic nanocrystal decay processes. However, due to fast and efficient hole trapping and non-uniform morphologies, the photophysics of dot-in-rod heterostructures are more rich and complex than this simple picture. Using transient absorption spectroscopy, we observe that the behavior of electrons in the CdS “rod” or “bulb” regions of non-uniform ZnSe/CdS and CdSe/CdS dot-in-rods is similar regardless of the “dot” material, which supports previous work demonstrating that hole trapping and particle morphology drive electron dynamics. Furthermore, we show that the longest lived state in these dot-in-rods is not generated by the type-II or quasi type-II band alignment between the dot and the rod, but rather by electron-hole dissociation that occurs due to fast hole trapping in the CdS rod and electron localization to the bulb. We propose that specific variations in particle morphology and surface chemistry determine the mechanism and efficiency of charge separation and recombination in these nanostructures, and therefore impact their excited-state dynamics to a greater extent than the heterostructure energy level alignment alone. When coupled to a [Fe-Fe] hydrogenase, which catalyzes reduction of protons to H
2, we observe faster rates of electron transfer and higher quantum efficiency of electron transfer with CdSe/CdS and ZnSe/CdS dot-in-rods, but only from the bulb and interface states. Furthermore, the total efficiency of electron transfer of the ensemble is highest when the bulb/interface state is directly populated. This indicates that the bulb morphology is essential to efficient electron transfer in a dot-in-rod hydrogenase system.
Advisors/Committee Members: Gordana Dukovic, Joel D. Eaves, Mathias M. Weber, Niels H. Damrauer, Margaret M. Murnane.
Subjects/Keywords: electron transfer; heterostructures; nanocrystals; nanorods; photophysics; ultrafast spectroscopy; Nanoscience and Nanotechnology; Physical Chemistry
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APA (6th Edition):
Grennell, A. N. (2017). Photophysics and Electron Transfer Dynamics of Type-II and Quasi Type-II Heterostructure Nanocrystals. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/269
Chicago Manual of Style (16th Edition):
Grennell, Amanda N. “Photophysics and Electron Transfer Dynamics of Type-II and Quasi Type-II Heterostructure Nanocrystals.” 2017. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/chem_gradetds/269.
MLA Handbook (7th Edition):
Grennell, Amanda N. “Photophysics and Electron Transfer Dynamics of Type-II and Quasi Type-II Heterostructure Nanocrystals.” 2017. Web. 05 Mar 2021.
Vancouver:
Grennell AN. Photophysics and Electron Transfer Dynamics of Type-II and Quasi Type-II Heterostructure Nanocrystals. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/chem_gradetds/269.
Council of Science Editors:
Grennell AN. Photophysics and Electron Transfer Dynamics of Type-II and Quasi Type-II Heterostructure Nanocrystals. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/chem_gradetds/269
University of Colorado
11.
Dorney, Kevin Michael.
A Twist in Strong-Field Physics: Structured, Ultrafast Optical and Extreme Ultraviolet Waveforms with Tailored Spin and Orbital Angular Momentum.
Degree: PhD, 2019, University of Colorado
URL: https://scholar.colorado.edu/chemistry_gradetds/1
► Structured light, which is composed of custom-tailored light waves possessing nontrivial intensity, polarization, and phase, has emerged in recent decades as a powerful tool…
(more)
▼ Structured light, which is composed of custom-tailored light waves possessing nontrivial intensity, polarization, and phase, has emerged in recent decades as a powerful tool for probing and controlling light-matter interactions, with wide-reaching applications in fields ranging from microscopy, to scientific/industrial imaging, lithography, and even to forensic science. In particular, structured light possessing optical angular momentum can exhibit both spin and orbital flavors related to the polarization and topological phase structure of light, respectively. This new ability to sculpt light into complex optical patterns has proven to be particularly beneficial for telecommunications, quantum computing, chiral sensing, and super-resolution imaging, to name a few. By connecting principles of generating and controlling structured light with the extreme nonlinear process of high-harmonic generation, this thesis details how exquisite control can be attained over extreme ultraviolet attosecond light wavesemdash in some cases rivaling and even surpassing the intricate structures so readily obtained at visible wavelengths. Using novel optical control schemes, I first show that the ellipticity of attosecond pulse trains produced via high-harmonic generation can be actively controlled in real time, yielding attosecond pulses with a custom-tunable polarization state. These concepts are then taken a step further by adding controllable amounts of orbital angular momentum to the visible driving lasers, which yields full control over the polarization, divergence, and topological charge of short-wavelength, coherent light pulses. The use of spin-orbit driving beams provides unprecedented control over the emitted high-harmonics, allowing for the generation of, for example, spatially isolated short-wavelength vortex beamsemdash and attosecond pulsesemdash of pure circular polarization. Then in a final, beautiful result, I show experimentally that by driving the high harmonic upconversion process with a time-delayed pair of optical vortex beams, it is possible to create an entirely new property of propagating waveforms, that possess a self-torque. This novel property of light is manifested in extreme ultraviolet beams that exhibit a rapid, attosecond variation of their orbital angular momentum, which spans an entire octave of topological charges. In the future, these sculpted attosecond waveforms with designer spin and orbital angular momentum can serve as the basis for applying structured light waves to solving grand challenge problems in chemistry and physics, while also making it possible to tailor light-matter interactions on nanometer spatial and attosecond temporal scales.
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Carlos Hernandez-Garcia, Niels Damrauer, Jun Ye.
Subjects/Keywords: attosecond science; high-harmonc generation; lasers; nonlinear optics; structured light; ultrafast optics; Chemistry; Physics
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APA (6th Edition):
Dorney, K. M. (2019). A Twist in Strong-Field Physics: Structured, Ultrafast Optical and Extreme Ultraviolet Waveforms with Tailored Spin and Orbital Angular Momentum. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chemistry_gradetds/1
Chicago Manual of Style (16th Edition):
Dorney, Kevin Michael. “A Twist in Strong-Field Physics: Structured, Ultrafast Optical and Extreme Ultraviolet Waveforms with Tailored Spin and Orbital Angular Momentum.” 2019. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/chemistry_gradetds/1.
MLA Handbook (7th Edition):
Dorney, Kevin Michael. “A Twist in Strong-Field Physics: Structured, Ultrafast Optical and Extreme Ultraviolet Waveforms with Tailored Spin and Orbital Angular Momentum.” 2019. Web. 05 Mar 2021.
Vancouver:
Dorney KM. A Twist in Strong-Field Physics: Structured, Ultrafast Optical and Extreme Ultraviolet Waveforms with Tailored Spin and Orbital Angular Momentum. [Internet] [Doctoral dissertation]. University of Colorado; 2019. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/chemistry_gradetds/1.
Council of Science Editors:
Dorney KM. A Twist in Strong-Field Physics: Structured, Ultrafast Optical and Extreme Ultraviolet Waveforms with Tailored Spin and Orbital Angular Momentum. [Doctoral Dissertation]. University of Colorado; 2019. Available from: https://scholar.colorado.edu/chemistry_gradetds/1
University of Colorado
12.
Tengdin, Phoebe Marie.
Direct Optically Driven Spin-Charge Dynamics Govern the Femtosecond Response of Ferromagnets.
Degree: PhD, 2019, University of Colorado
URL: https://scholar.colorado.edu/eeng_gradetds/35
► Ferromagnetic materials have strong electron correlations that drive quantum effects and make the physics that describes them extremely challenging. In particular, the electron, spin, and…
(more)
▼ Ferromagnetic materials have strong electron correlations that drive quantum effects and make the physics that describes them extremely challenging. In particular, the electron, spin, and lattice degrees of freedom can interact in surprising ways when driven out of equilibrium by ultrafast laser excitation. In this thesis I uncover several previously unexpected connections between the electronic and spin systems in ferromagnets. Dynamics occur at unexpectedly fast timescales, driven using femtosecond laser excitation pulses. The tools that I use to observe the exceeding fast (10s of femtosecond) dynamics are bursts of extreme ultraviolet light resonant with the
M-edge of transition metals and produced via high harmonic generation. We combine time-resolved transverse magneto-optical Kerr effect and time- and angle-resolved photoemission spectroscopies to show that the same critical behavior that governs the equilibrium magnetic phase transition in nickel also governs the ultrafast dynamics within 20 fs of laser excitation. When the electron temperature is transiently driven above the Curie temperature, we observe an extremely rapid change in the material response: the spin system absorbs sufficient energy within the first 20 fs to subsequently proceed through the phase transition, whereas demagnetization and the collapse of the exchange splitting occur on much longer, fluence- independent time scales of 176 fs. This observation defines a new timescale in the field of ultrafast ferromagnetism. The next question is then whether or not a response at this speed or faster can be directly observed in more complex materials. To investigate this I perform experiments on the half-metallic heusler compound Co
2MnGe. Here a single infrared femtosecond laser pulse drives ultrafast transfer of spin polarization from one elemental sublattice to another within its pulse duration. I simultaneously probe the magnetic response of cobalt and manganese to make a surprising finding: the magnetization of Co is transiently enhanced, while that of Mn rapidly quenches. This marks the first direct manipulation of electron spins via light, providing a path to spintronic logic devices such as switches and triggers that operate on few femtosecond or even faster timescales.
Advisors/Committee Members: Margaret M. Murnane, Henry Kapteyn, Tom J. Silva, Hans Nembach, Xiaobo Yin.
Subjects/Keywords: correlated electrons; ferromagnetism; high harmonic generation; quantum materials; ultrafast; Materials Science and Engineering; Optics
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MLA ·
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APA (6th Edition):
Tengdin, P. M. (2019). Direct Optically Driven Spin-Charge Dynamics Govern the Femtosecond Response of Ferromagnets. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/eeng_gradetds/35
Chicago Manual of Style (16th Edition):
Tengdin, Phoebe Marie. “Direct Optically Driven Spin-Charge Dynamics Govern the Femtosecond Response of Ferromagnets.” 2019. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/eeng_gradetds/35.
MLA Handbook (7th Edition):
Tengdin, Phoebe Marie. “Direct Optically Driven Spin-Charge Dynamics Govern the Femtosecond Response of Ferromagnets.” 2019. Web. 05 Mar 2021.
Vancouver:
Tengdin PM. Direct Optically Driven Spin-Charge Dynamics Govern the Femtosecond Response of Ferromagnets. [Internet] [Doctoral dissertation]. University of Colorado; 2019. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/eeng_gradetds/35.
Council of Science Editors:
Tengdin PM. Direct Optically Driven Spin-Charge Dynamics Govern the Femtosecond Response of Ferromagnets. [Doctoral Dissertation]. University of Colorado; 2019. Available from: https://scholar.colorado.edu/eeng_gradetds/35
University of Colorado
13.
Peters, Willliam Kenneth.
Carrier Dynamics in Nanocrystalline Lead Salts and Non-Adiabatic Dynamics in Near-Degenerate States of Molecules.
Degree: PhD, Chemistry & Biochemistry, 2012, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/73
► Degenerate femtosecond pump-probe transient absorption measurements are presented of hot carrier dynamics following above band-edge absorption in colloidal lead sulfide quantum dots. A transient…
(more)
▼ Degenerate femtosecond pump-probe transient absorption measurements are presented of hot carrier dynamics following above band-edge absorption in colloidal lead sulfide quantum dots. A transient bleach is only found when pumping to a satellite valley. When pumping in the main valley no transient bleach is seen with 20-25 fs pulses, indicating hot carrier dephasing occurs in 5 fs or less. The signal at long times is ~300 times smaller than would be expected from a two level system, indicating systematic excited state absorption. Based on this data, arguments based on bulk band structure and scattering length indicate hot electrons are essentially bulk-like until cooling to quantum confined states.
Femtosecond electronic dynamics are also studied theoretically for model Hamiltonians developed to model near-degenerate states in molecules or molecular dimers. Particular emphasis is placed on the case of weak nonadiabatic coupling when the electronic energy gap is close to one vibrational quantum of energy. A visualization scheme is developed for plotting nonadiabatic wavefunctions with an explicitly shown vibrational wavefunction and coordinate-dependent coloring which indicates both electronic composition and overall wavefunction sign. Nonadiabatic eigenstates are found to display a vibrationally nodeless character, indicating large-amplitude oscillations between zero-order electronic basis states.
Advisors/Committee Members: David M. Jonas, G. Barney Ellison, Niels H. Damrauer, Rex T. Skodje, Margaret M. Murnane.
Subjects/Keywords: Chemistry; Physical Chemistry
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APA (6th Edition):
Peters, W. K. (2012). Carrier Dynamics in Nanocrystalline Lead Salts and Non-Adiabatic Dynamics in Near-Degenerate States of Molecules. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/73
Chicago Manual of Style (16th Edition):
Peters, Willliam Kenneth. “Carrier Dynamics in Nanocrystalline Lead Salts and Non-Adiabatic Dynamics in Near-Degenerate States of Molecules.” 2012. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/chem_gradetds/73.
MLA Handbook (7th Edition):
Peters, Willliam Kenneth. “Carrier Dynamics in Nanocrystalline Lead Salts and Non-Adiabatic Dynamics in Near-Degenerate States of Molecules.” 2012. Web. 05 Mar 2021.
Vancouver:
Peters WK. Carrier Dynamics in Nanocrystalline Lead Salts and Non-Adiabatic Dynamics in Near-Degenerate States of Molecules. [Internet] [Doctoral dissertation]. University of Colorado; 2012. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/chem_gradetds/73.
Council of Science Editors:
Peters WK. Carrier Dynamics in Nanocrystalline Lead Salts and Non-Adiabatic Dynamics in Near-Degenerate States of Molecules. [Doctoral Dissertation]. University of Colorado; 2012. Available from: https://scholar.colorado.edu/chem_gradetds/73
University of Colorado
14.
Mancuso, Christopher Andrew.
Strong Field Ionization of Atoms Irradiated with Two-Color Circularly Polarized Femtosecond Laser Fields: Rescattering in a Whole New Dimension.
Degree: PhD, Physics, 2016, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/177
► High-harmonic generation driven by two-color counter-rotating circularly polarized laser fields was recently demonstrated experimentally as a breakthrough source of bright, coherent, circularly polarized beams in…
(more)
▼ High-harmonic generation driven by two-color counter-rotating circularly polarized laser fields was recently demonstrated experimentally as a breakthrough source of bright, coherent, circularly polarized beams in the extreme ultraviolet and soft-x-ray regions. However, the conditions for optimizing the single-atom yield are significantly more complex than for linearly polarized driving lasers and are not fully understood. In this thesis, I present a comprehensive study of strong-field ionization–the complementary process to high-harmonic generation–driven by two-color circularly polarized fields. First, I describe a new experimental method that allows for the reconstruction of three-dimensional photoelectron angular distributions generated with two-color circularly polarized laser fields. Second, I present the first measurements of electron-ion rescattering in these fields, showing that the process can be systematically controlled by changing the parameters of the driving lasers. Finally, I present the first observation of nonsequential double ionization in two-color circularly polarized laser fields, showing how to optimize the yield of electrons that return to the parent ion at high energies. These findings help build an understanding of the single-atom physics behind high-harmonic generation. Additionally, since electrons ionized in two-color circularly polarized laser fields can be driven in two-dimensional trajectories before retuning to the parent ion, these findings will help inform the next-generation of experiments studying molecular dynamics on the ultrafast time scale.
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Charles Durfee, Sterling Backus, Daniel Adams.
Subjects/Keywords: Electron Rescattering; High Harmonic Generation; Nonsequential Double Ionization; Strong Field Ionization; Physics; Plasma and Beam Physics
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APA (6th Edition):
Mancuso, C. A. (2016). Strong Field Ionization of Atoms Irradiated with Two-Color Circularly Polarized Femtosecond Laser Fields: Rescattering in a Whole New Dimension. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/177
Chicago Manual of Style (16th Edition):
Mancuso, Christopher Andrew. “Strong Field Ionization of Atoms Irradiated with Two-Color Circularly Polarized Femtosecond Laser Fields: Rescattering in a Whole New Dimension.” 2016. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/177.
MLA Handbook (7th Edition):
Mancuso, Christopher Andrew. “Strong Field Ionization of Atoms Irradiated with Two-Color Circularly Polarized Femtosecond Laser Fields: Rescattering in a Whole New Dimension.” 2016. Web. 05 Mar 2021.
Vancouver:
Mancuso CA. Strong Field Ionization of Atoms Irradiated with Two-Color Circularly Polarized Femtosecond Laser Fields: Rescattering in a Whole New Dimension. [Internet] [Doctoral dissertation]. University of Colorado; 2016. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/177.
Council of Science Editors:
Mancuso CA. Strong Field Ionization of Atoms Irradiated with Two-Color Circularly Polarized Femtosecond Laser Fields: Rescattering in a Whole New Dimension. [Doctoral Dissertation]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/phys_gradetds/177
University of Colorado
15.
Hickstein, Daniel Durand.
Photoelectron and Photoion Spectroscopy of Atoms, Nanoparticles, and Nanoplasmas Irradiated with Strong Femtosecond Laser Fields.
Degree: PhD, Physics, 2014, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/179
► Modern femtosecond lasers can produce pulses of light that are shorter than the vibrational periods in molecules and have electric fields stronger than the…
(more)
▼ Modern femtosecond lasers can produce pulses of light that are shorter than the vibrational periods in molecules and have electric fields stronger than the Coulomb field that binds electrons in atoms. These short pulse lasers enable the observation of chemical reactions, the production of attosecond bursts of high-energy photons, and the precision-machining of solid materials with minimal heat transport to the material. In this thesis, I describe three experiments that provide new insight into strong-field (~10
14 Watts/cm
2) femtosecond laser-matter interactions in three important regimes. First, I discuss the strong-field ionization of gas-phase atoms, identify a new structure in the photoelectron angular distribution of xenon gas, and explain this structure as a result of field-driven electrons colliding with the Coulomb potential of the ion. Second, I describe a new method to perform photoelectron and photoion spectroscopy on single, isolated nanoparticles and demonstrate this technique by observing the directional ion ejection that takes place in the laser ablation of nanostructures. Finally, I present the first experimental observations of shock wave propagation in nanoscale plasmas. These findings will guide future efforts to probe the structure of atoms and molecules on the femtosecond timescale, design nanomaterials that enhance light on the subwavelength scale, and produce high-energy ions from plasmas.
Advisors/Committee Members: Henry C. Kapteyn, David M. Jonas, Margaret M. Murnane, Carl W. Lineberger, Agnieszka A. Jaron-Becker.
Subjects/Keywords: femtosecond; laser; nanoparticle; nanoplasma; plasma; xenon; Chemistry; Optics; Physics
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APA (6th Edition):
Hickstein, D. D. (2014). Photoelectron and Photoion Spectroscopy of Atoms, Nanoparticles, and Nanoplasmas Irradiated with Strong Femtosecond Laser Fields. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/179
Chicago Manual of Style (16th Edition):
Hickstein, Daniel Durand. “Photoelectron and Photoion Spectroscopy of Atoms, Nanoparticles, and Nanoplasmas Irradiated with Strong Femtosecond Laser Fields.” 2014. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/179.
MLA Handbook (7th Edition):
Hickstein, Daniel Durand. “Photoelectron and Photoion Spectroscopy of Atoms, Nanoparticles, and Nanoplasmas Irradiated with Strong Femtosecond Laser Fields.” 2014. Web. 05 Mar 2021.
Vancouver:
Hickstein DD. Photoelectron and Photoion Spectroscopy of Atoms, Nanoparticles, and Nanoplasmas Irradiated with Strong Femtosecond Laser Fields. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/179.
Council of Science Editors:
Hickstein DD. Photoelectron and Photoion Spectroscopy of Atoms, Nanoparticles, and Nanoplasmas Irradiated with Strong Femtosecond Laser Fields. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/phys_gradetds/179
University of Colorado
16.
Gardner, Dennis Floyd, Jr.
Coherent Diffractive Imaging Near the Spatio-Temporal Limit with High-Harmonic Sources.
Degree: PhD, 2017, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/194
► This thesis discusses methods for high-resolution static and stroboscopic microscopy using tabletop coherent extreme ultraviolet (EUV) radiation from tabletop high-harmonic generation (HHG) sources. These…
(more)
▼ This thesis discusses methods for high-resolution static and stroboscopic microscopy using tabletop coherent extreme ultraviolet (EUV) radiation from tabletop high-harmonic generation (HHG) sources. These coherent short wavelength light sources are combined with a lensless, computational, phase and amplitude-contrast technique called ptychographic Coherent Diffractive Imaging (CDI). While ptychographic CDI techniques are currently widespread for visible, EUV and X-ray microscopy, no previous work has been able to achieve at-wavelength resolution of extended samples, especially in a reflection geometry, nor has previous work been able to image periodic samples with high-fidelity. In this work, a combination of experimental methods for high-numerical aperture imaging and novel computational algorithms enabled the highest resolution-to-wavelength demonstrations using any CDI technique. These algorithms include tilted plane correction, which enables high-resolution imaging of surfaces in a reflection geometry, and a powerful technique termed ‘modulus enforced probe’, which enables both imaging of periodic objects and convergence of the ptychographic CDI algorithm in fewer iterations. Furthermore, the ultrafast pulse duration of the high-harmonic radiation is harnessed to demonstrate proof-of-principle pump-probe imaging of nanostructures, capturing thermal transport processes in nanostructures with an axial resolution of 3 angstroms. Stroboscopic imaging with nanoscale resolution is a critical tool for the investigation of nanoscale heat flow and magnetic switching for the advancement of next generation nano-electronics, data storage, and nano-engineered systems.
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Daniel E. Adams, Ivan I. Smalyukh, Mark Hernandez.
Subjects/Keywords: coherent diffractive imaging; computational imaging; extreme ultraviolet EUV; high harmonic generation; high-resolution microscopy; ptychography; Nanotechnology; Optics; Physics
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APA ·
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APA (6th Edition):
Gardner, Dennis Floyd, J. (2017). Coherent Diffractive Imaging Near the Spatio-Temporal Limit with High-Harmonic Sources. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/194
Chicago Manual of Style (16th Edition):
Gardner, Dennis Floyd, Jr. “Coherent Diffractive Imaging Near the Spatio-Temporal Limit with High-Harmonic Sources.” 2017. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/194.
MLA Handbook (7th Edition):
Gardner, Dennis Floyd, Jr. “Coherent Diffractive Imaging Near the Spatio-Temporal Limit with High-Harmonic Sources.” 2017. Web. 05 Mar 2021.
Vancouver:
Gardner, Dennis Floyd J. Coherent Diffractive Imaging Near the Spatio-Temporal Limit with High-Harmonic Sources. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/194.
Council of Science Editors:
Gardner, Dennis Floyd J. Coherent Diffractive Imaging Near the Spatio-Temporal Limit with High-Harmonic Sources. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/phys_gradetds/194
University of Colorado
17.
Chen, Cong.
Attosecond Light Pulses and Attosecond Electron Dynamics Probed Using Angle-Resolved Photoelectron Spectroscopy.
Degree: PhD, 2017, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/205
► Recent advances in the generation and control of attosecond light pulses have opened up new opportunities for the real-time observation of sub-femtosecond (1 fs…
(more)
▼ Recent advances in the generation and control of attosecond light pulses have opened up new opportunities for the real-time observation of sub-femtosecond (1 fs = 10
-15 s) electron dynamics in gases and solids. Combining attosecond light pulses with angle-resolved photoelectron spectroscopy (atto-ARPES) provides a powerful new technique to study the influence of material band structure on attosecond electron dynamics in materials. Electron dynamics that are only now accessible include the lifetime of far-above-bandgap excited electronic states, as well as fundamental electron interactions such as scattering and screening. In addition, the same atto-ARPES technique can also be used to measure the temporal structure of complex coherent light fields. In this thesis, I present four experiments utilizing atto-ARPES to provide new insights into the generation and characterization of attosecond light pulses, as well as the attosecond electron dynamics in transition metals. First, I describe a new method to extend attosecond metrology techniques to the reconstruction of circularly polarized attosecond light pulses for the first time. Second, I show that by driving high harmonics with a two-color linearly polarized laser field, quasi-isolated attosecond pulses are generated because the phase matching window is confined. Third, I present the first measurement of lifetimes for photoelectrons that are born into free-electron-like states compared with those that are excited into unoccupied excited states in the band structure of a material (Ni(111)). The finite excited-state lifetime causes a ≈200 as delay in the emission of photoelectrons. Finally, I describe direct time-domain studies of electron-electron interactions in transition metals with both simple and complex Fermi surfaces. In particular, I show the influence of electron-electron scattering and screening on the lifetime of photoelectrons.
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Andreas Becker, Xiaobo Yin, W. Carl Lineberger.
Subjects/Keywords: attosecond; electron dynamics; EUV; high harmonic generation; photoemission; ultrafast; Physics
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APA (6th Edition):
Chen, C. (2017). Attosecond Light Pulses and Attosecond Electron Dynamics Probed Using Angle-Resolved Photoelectron Spectroscopy. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/205
Chicago Manual of Style (16th Edition):
Chen, Cong. “Attosecond Light Pulses and Attosecond Electron Dynamics Probed Using Angle-Resolved Photoelectron Spectroscopy.” 2017. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/205.
MLA Handbook (7th Edition):
Chen, Cong. “Attosecond Light Pulses and Attosecond Electron Dynamics Probed Using Angle-Resolved Photoelectron Spectroscopy.” 2017. Web. 05 Mar 2021.
Vancouver:
Chen C. Attosecond Light Pulses and Attosecond Electron Dynamics Probed Using Angle-Resolved Photoelectron Spectroscopy. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/205.
Council of Science Editors:
Chen C. Attosecond Light Pulses and Attosecond Electron Dynamics Probed Using Angle-Resolved Photoelectron Spectroscopy. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/phys_gradetds/205
University of Colorado
18.
Grennell, Amanda Norell.
Photophysics and Electron Transfer Dynamics of Type-Ii and Quasi Type-Ii Heterostructure Nanocrystals.
Degree: PhD, Chemistry & Biochemistry, 2017, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/222
► Type-II and quasi type-II heterostructure nanocrystals are known to exhibit extended excited-state lifetimes compared to their single material counterparts because of reduced wavefunction overlap between…
(more)
▼ Type-II and quasi type-II heterostructure nanocrystals are known to exhibit extended excited-state lifetimes compared to their single material counterparts because of reduced wavefunction overlap between the electron and hole. Thus, type-II heterostructures are promising materials for solar-to-fuel conversion, as extended excited-state lifetimes make transfer of charges to a catalyst more competitive with intrinsic nanocrystal decay processes. However, due to fast and efficient hole trapping and non-uniform morphologies, the photophysics of dot-in-rod heterostructures are more rich and complex than this simple picture. Using transient absorption spectroscopy, we observe that the behavior of electrons in the CdS “rod” or “bulb” regions of non-uniform ZnSe/CdS and CdSe/CdS dot-in-rods is similar regardless of the “dot” material, which supports previous work demonstrating that hole trapping and particle morphology drive electron dynamics. Furthermore, we show that the longest lived state in these dot-in-rods is not generated by the type-II or quasi type-II band alignment between the dot and the rod, but rather by electron-hole dissociation that occurs due to fast hole trapping in the CdS rod and electron localization to the bulb. We propose that specific variations in particle morphology and surface chemistry determine the mechanism and efficiency of charge separation and recombination in these nanostructures, and therefore impact their excited-state dynamics to a greater extent than the heterostructure energy level alignment alone. When coupled to a [Fe-Fe] hydrogenase, which catalyzes reduction of protons to H2, we observe faster rates of electron transfer and higher quantum efficiency of electron transfer with CdSe/CdS and ZnSe/CdS dot-in-rods, but only from the bulb and interface states. Furthermore, the total efficiency of electron transfer of the ensemble is highest when the bulb/interface state is directly populated. This indicates that the bulb morphology is essential to efficient electron transfer in a dot-in-rod hydrogenase system.
Advisors/Committee Members: Gordana Dukovic, Joel D. Eaves, Mathias M. Weber, Niels H. Damrauer, Margaret M. Murnane.
Subjects/Keywords: Electron transfer; Heterostructures; Nanocrystals; Nanorods; Photophysics; Ultrafast spectroscopy; Nanoscience and Nanotechnology; Physical Chemistry
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APA (6th Edition):
Grennell, A. N. (2017). Photophysics and Electron Transfer Dynamics of Type-Ii and Quasi Type-Ii Heterostructure Nanocrystals. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/222
Chicago Manual of Style (16th Edition):
Grennell, Amanda Norell. “Photophysics and Electron Transfer Dynamics of Type-Ii and Quasi Type-Ii Heterostructure Nanocrystals.” 2017. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/chem_gradetds/222.
MLA Handbook (7th Edition):
Grennell, Amanda Norell. “Photophysics and Electron Transfer Dynamics of Type-Ii and Quasi Type-Ii Heterostructure Nanocrystals.” 2017. Web. 05 Mar 2021.
Vancouver:
Grennell AN. Photophysics and Electron Transfer Dynamics of Type-Ii and Quasi Type-Ii Heterostructure Nanocrystals. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/chem_gradetds/222.
Council of Science Editors:
Grennell AN. Photophysics and Electron Transfer Dynamics of Type-Ii and Quasi Type-Ii Heterostructure Nanocrystals. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/chem_gradetds/222
University of Colorado
19.
Shanblatt, Elisabeth Rose.
High-Resolution, Quantitative, and Three-Dimensional Coherent Diffractive Imaging with a Tabletop Euv Source.
Degree: PhD, Physics, 2017, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/215
► Imaging is a critical tool used across a broad range of applications in science, technology, medicine, and manufacturing. Microscopy, the type of imaging which…
(more)
▼ Imaging is a critical tool used across a broad range of applications in science, technology, medicine, and manufacturing. Microscopy, the type of imaging which allows us to access the elusive yet rich world of what is smaller than we can naturally see – makes it possible to observe and design the nano-world of biological, material, and nanofabricated systems. In this thesis, I describe the development of a new type of microscopy that combines two powerful tools: coherent extreme ultraviolet (EUV) light sources produced by high harmonic generation, and ptychographic coherent diffractive imaging. This microscope produces high-resolution, chemically-specific, phase- and amplitude- contrast images with large fields of view on the order of hundreds of microns, while preserving a high spatial resolution on the scale of tens of nanometers. Recently, we extended this new tabletop microscopy technique to image reflective samples, periodic samples, and to image dynamic nano-scale elastic and thermal processes. I will discuss these advances and in particular demonstrate two new capabilities: first, a new imaging technique with high compositionally- and morphologically-sensitive quantitative information, capable of imaging reactions and diffusion at a buried interface. This capability will open up a new, exquisitely sensitive layer-by-layer imaging that has many applications in nanoscience and nanotechnology, including surface and materials science and metrology. Secondly, I will demonstrate imaging of a thick sample in three dimensions. By accounting for diffraction within a thick sample, it is possible to obtain high-resolution three-dimensional images of biological and meta-material samples non-invasively, and without the use of staining or labeling.
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Daniel E. Adams, Robert R. McLeod, Eric A. Cornell.
Subjects/Keywords: 3D imaging; Computational imaging; Extreme ultraviolet light; High harmonic generation; Materials characterization; Nanotechnology; Materials Science and Engineering; Optics; Physics
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APA (6th Edition):
Shanblatt, E. R. (2017). High-Resolution, Quantitative, and Three-Dimensional Coherent Diffractive Imaging with a Tabletop Euv Source. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/215
Chicago Manual of Style (16th Edition):
Shanblatt, Elisabeth Rose. “High-Resolution, Quantitative, and Three-Dimensional Coherent Diffractive Imaging with a Tabletop Euv Source.” 2017. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/215.
MLA Handbook (7th Edition):
Shanblatt, Elisabeth Rose. “High-Resolution, Quantitative, and Three-Dimensional Coherent Diffractive Imaging with a Tabletop Euv Source.” 2017. Web. 05 Mar 2021.
Vancouver:
Shanblatt ER. High-Resolution, Quantitative, and Three-Dimensional Coherent Diffractive Imaging with a Tabletop Euv Source. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/215.
Council of Science Editors:
Shanblatt ER. High-Resolution, Quantitative, and Three-Dimensional Coherent Diffractive Imaging with a Tabletop Euv Source. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/phys_gradetds/215
University of Colorado
20.
Hernández Charpak, Jorge Nicolás.
Uncovering New Thermal and Elastic Properties of Nanostructured Materials Using Coherent Euv Light.
Degree: PhD, Physics, 2017, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/216
► Advances in nanofabrication have pushed the characteristic dimensions of nanosystems well below 100nm, where physical properties are often significantly different from their bulk counterparts,…
(more)
▼ Advances in nanofabrication have pushed the characteristic dimensions of nanosystems well below 100nm, where physical properties are often significantly different from their bulk counterparts, and accurate models are lacking. Critical technologies such as thermoelectrics for energy harvesting, nanoparticle-mediated thermal therapy, nano-enhanced photovoltaics, and efficient thermal management in integrated circuits depend on our increased understanding of the nanoscale. However, traditional microscopic characterization tools face fundamental limits at the nanoscale. Theoretical efforts to build a fundamental picture of nanoscale thermal dynamics lack experimental validation and still struggle to account for newly reported behaviors. Moreover, precise characterization of the elastic behavior of nanostructured systems is needed for understanding the unique physics that become apparent in small-scale systems, such as thickness-dependent or fabrication-dependent elastic properties. In essence, our ability to fabricate nanosystems has outstripped our ability to understand and characterize them. In my PhD thesis, I present the development and refinement of coherent extreme ultraviolet (EUV) nanometrology, a novel tool used to probe material properties at the intrinsic time- and length-scales of nanoscale dynamics. By extending ultrafast photoacoustic and thermal metrology techniques to very short probing wavelengths using tabletop coherent EUV beams from high-harmonic upconversion (HHG) of femtosecond lasers, coherent EUV nanometrology allows for a new window into nanoscale physics, previously unavailable with traditional techniques. Using this technique, I was able to probe both thermal and acoustic dynamics in nanostructured systems with characteristic dimensions below 50nm with high temporal (sub-ps) and spatial (<10pm vertical) resolution, including the smallest heat sources probed (20nm) and thinnest film (10.9nm) fully mechanically characterized to date. By probing nanoscale thermal transport (i.e. cooling) of periodic hot nanostructures down to 20nm in characteristic dimension in both 1D (nanolines) and 2D (nanocubes) geometries, I uncovered a new surprising regime of nanoscale thermal transport called the "collectively-diffusive regime". In this regime, nanoscale hot spots cool faster when placed closer together than when farther apart. This is a consequence of the interplay between both the size and spacing of the nanoscale heat sources with the phonon spectrum of a material. This makes our technique one of the only experimental routes to directly probe the dynamics of phonons in complex materials, which is critical to both technological applications and fundamental condensed matter physics. I developed a proof of concept model and used it to extract the first experimental differential conductivity phonon mean free path (MFP) spectra for silicon and sapphire, which compare well with first-principles calculations. However, a complete picture of the physics is still elusive. Thus, I developed a…
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Mahmoud Hussein, Minhyea Lee, Ronggui Yang.
Subjects/Keywords: extreme ultraviolet light; nanoscale elastic properties; nanoscale thermal transport; phonon dynamics; thin films; ultrafast dynamics; Materials Science and Engineering; Nanoscience and Nanotechnology; Optics
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APA (6th Edition):
Hernández Charpak, J. N. (2017). Uncovering New Thermal and Elastic Properties of Nanostructured Materials Using Coherent Euv Light. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/216
Chicago Manual of Style (16th Edition):
Hernández Charpak, Jorge Nicolás. “Uncovering New Thermal and Elastic Properties of Nanostructured Materials Using Coherent Euv Light.” 2017. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/216.
MLA Handbook (7th Edition):
Hernández Charpak, Jorge Nicolás. “Uncovering New Thermal and Elastic Properties of Nanostructured Materials Using Coherent Euv Light.” 2017. Web. 05 Mar 2021.
Vancouver:
Hernández Charpak JN. Uncovering New Thermal and Elastic Properties of Nanostructured Materials Using Coherent Euv Light. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/216.
Council of Science Editors:
Hernández Charpak JN. Uncovering New Thermal and Elastic Properties of Nanostructured Materials Using Coherent Euv Light. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/phys_gradetds/216
University of Colorado
21.
Fan, Tingting.
Bright Linearly and Circularly Polarized Extreme Ultraviolet and Soft X-Ray High Harmonics for Absorption Spectroscopy.
Degree: PhD, Physics, 2017, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/220
► High harmonic generation (HHG) is an extreme nonlinear optical process. When implemented in a phase-matched geometry, HHG coherent upconverts femtosecond laser light into coherent…
(more)
▼ High harmonic generation (HHG) is an extreme nonlinear optical process. When implemented in a phase-matched geometry, HHG coherent upconverts femtosecond laser light into coherent “X-ray laser” beams, while retaining excellent spatial and temporal coherence, as well as the polarization state of the driving laser. HHG has a tabletop footprint, with femtosecond to attosecond time resolution, combined with nanometer spatial resolution. As a consequence of these unique capabilities, HHG is now being widely adopted for use in molecular spectroscopy and imaging, materials science, as well as nanoimaging in general. In the first half of this thesis, I demonstrate high flux linearly polarized soft X-ray HHG, driven by a single-stage 10-mJ Ti:sapphire regenerative amplifier at a repetition rate of 1 kHz. I first down-converted the laser to 1.3 μ
m using an optical parametric amplifier, before up-converting it into the soft X-ray region using HHG in a high-pressure, phase-matched, hollow waveguide geometry. The resulting optimally phase-matched broadband spectrum extends to 200 eV, with a soft X-ray photon flux of > 10
6 photons/pulse/1% bandwidth at 1 kHz, corresponding to > 10
9 photons/s/1% bandwidth, or approximately a three orders-of-magnitude increase compared with past work. Using this broad bandwidth X-ray source, I demonstrated X-ray absorption spectroscopy of multiple elements and transitions in molecules in a single spectrum, with a spectral resolution of 0.25 eV, and with the ability to resolve the near edge fine structure. In the second half of this thesis, I discuss how to generate the first bright circularly polarized (CP) soft X-ray HHG and also use them to implement the first tabletop X-ray magnetic circular dichroism (XMCD) measurements. Using counter-rotating CP lasers at 1.3 μ
m and 0.79 μ
m, I generated CPHHG with photon energies exceeding 160 eV. The harmonic spectra emerge as a sequence of closely spaced pairs of left and right CP peaks, with energies determined by conservation of energy and spin angular momentum. I explain the single-atom and macroscopic physics by identifying the dominant electron quantum trajectories and optimal phase matching conditions. The first advanced propagation simulations for CPHHG reveal the influence of the finite phase matching temporal window on the spectrum, as well as the unique polarization-shaped attosecond pulse train. The first tabletop XMCD measurements at the N4,5 absorption edges of Gd using this light source validate the high degree of circularity, brightness, and stability of this light source. These results demonstrate the feasibility of manipulating the polarization, spectrum and temporal shape of soft X-ray HHG by manipulating the driving laser waveform. Finally, I present the first bright phase-matched CPHHG driven by lasers at wavelengths of 2 μ
m and 0.79 μ
m, which extends CPHHG to a broader wavelength combination and confirms the universal nature of this generation scheme. By analyzing the helicity dependent intensity asymmetry of CPHHG…
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Andreas Becker, Agnieszka A. Jaron-Becker, Ronggui Yang.
Subjects/Keywords: Absorption spectroscopy; Extreme ultraviolet; High harmonics generation; Magnetic materials; Ultrafast light science; X-rays; Optics; Physics
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APA ·
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APA (6th Edition):
Fan, T. (2017). Bright Linearly and Circularly Polarized Extreme Ultraviolet and Soft X-Ray High Harmonics for Absorption Spectroscopy. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/220
Chicago Manual of Style (16th Edition):
Fan, Tingting. “Bright Linearly and Circularly Polarized Extreme Ultraviolet and Soft X-Ray High Harmonics for Absorption Spectroscopy.” 2017. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/220.
MLA Handbook (7th Edition):
Fan, Tingting. “Bright Linearly and Circularly Polarized Extreme Ultraviolet and Soft X-Ray High Harmonics for Absorption Spectroscopy.” 2017. Web. 05 Mar 2021.
Vancouver:
Fan T. Bright Linearly and Circularly Polarized Extreme Ultraviolet and Soft X-Ray High Harmonics for Absorption Spectroscopy. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/220.
Council of Science Editors:
Fan T. Bright Linearly and Circularly Polarized Extreme Ultraviolet and Soft X-Ray High Harmonics for Absorption Spectroscopy. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/phys_gradetds/220
University of Colorado
22.
Wang, Susannah Rachel.
High Peak and Average Power Mid-Infrared Laser for High Harmonic Generation of Soft X-Rays.
Degree: PhD, Physics, 2016, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/222
► This thesis describes the development of a new mid-infrared laser designed to drive high harmonic generation of keV-energy soft x-rays with high flux. The…
(more)
▼ This thesis describes the development of a new mid-infrared laser designed to drive high harmonic generation of keV-energy soft x-rays with high flux. The mid-infrared wavelength regime (3 to 5 μ
m wavelength) is required to generate high harmonics with photon energies reaching 1 keV in the form of isolated attosecond bursts. This light would provide simultaneous few-nanometer spatial resolution and attosecond time resolution that could shed light on physical processes which occur at these length and time scales. Such processes have both scientific and technological importance. The laser system described in this thesis reaches pulse energies up to 1.25 mJ at 1 kHz repetition rate, 3.1 μ
m wavelength, and with enough bandwidth to support 60 fs transform-limited pulses. Also, we demonstrate preliminary pulse compression to below 500 fs. This laser is therefore the first table-top mid-infrared laser with enough peak intensity and average power to generate harmonics with sufficient flux to be useful for application experiments. This laser uses Optical Parametric Chirped Pulse Amplification (OPCPA) to convert near-infrared light to the 3 μ
m wavelength regime, combining fiber lasers, cryogenically cooled solid state lasers, diode lasers, and optical parametric amplification in a unique architecture. In this thesis, we describe the current design of this laser system, the considerations that influenced its design, and its potential for scaling to higher pulse energies and repetition rates in the future.
Advisors/Committee Members: Henry C. Kapteyn, Margaret M. Murnane, Sterling Backus, Andreas Becker, Kelvin Wagner.
Subjects/Keywords: HHG; laser; mid-infrared; OPCPA; ultrafast; x-ray; Optics; Physics; Quantum Physics
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APA (6th Edition):
Wang, S. R. (2016). High Peak and Average Power Mid-Infrared Laser for High Harmonic Generation of Soft X-Rays. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/222
Chicago Manual of Style (16th Edition):
Wang, Susannah Rachel. “High Peak and Average Power Mid-Infrared Laser for High Harmonic Generation of Soft X-Rays.” 2016. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/222.
MLA Handbook (7th Edition):
Wang, Susannah Rachel. “High Peak and Average Power Mid-Infrared Laser for High Harmonic Generation of Soft X-Rays.” 2016. Web. 05 Mar 2021.
Vancouver:
Wang SR. High Peak and Average Power Mid-Infrared Laser for High Harmonic Generation of Soft X-Rays. [Internet] [Doctoral dissertation]. University of Colorado; 2016. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/222.
Council of Science Editors:
Wang SR. High Peak and Average Power Mid-Infrared Laser for High Harmonic Generation of Soft X-Rays. [Doctoral Dissertation]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/phys_gradetds/222
University of Colorado
23.
Turgut, Emrah.
Studying Laser-Induced Spin Currents Using Ultrafast Extreme Ultraviolet Light.
Degree: PhD, Physics, 2014, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/108
► Next-generation magnetic-memory devices and heat-assisted magnetic-recording applications will require a better understanding of magnetic multilayers and their interactions with optical-laser pulses. In this thesis,…
(more)
▼ Next-generation magnetic-memory devices and heat-assisted magnetic-recording applications will require a better understanding of magnetic multilayers and their interactions with optical-laser pulses. In this thesis, by combining the advantages of ultrabroad-band extreme-ultraviolet light including ultrafast time resolution, element selectivity and tabletop easy access, I report three findings in the study of ultrafast magnetization dynamics in itinerant ferromagnets. First, I experimentally prove that the transverse magneto-optical Kerr response with extreme-ultraviolet light has a purely magnetic origin and that our experimental technique is an artifact-free ultrafast magnetic probe. Second, I demonstrate the first ultrafast magnetization enhancement driven by ultrafast spin currents in Ni/Ru/Fe multilayers. Third, I engineer the sample system by choosing either insulating or spin-scattering spacer layers between the Ni and Fe magnetic layers and by structural ordering. Then, I control the competition between ultrafast spin-flip scattering and superdiffusive spin-current mechanisms; either of these processes may to be the dominant mechanism in ultrafast demagnetization.
Finally, I report two continuing experiments that are promising for future ultrafast magnetization studies with extreme-ultraviolet sources. These experiments are resonant-magnetic small-angle-scattering and the generation of bright circularly polarized high harmonics accompanied by a demonstration of the first x-ray magnetic circular dichroism with a tabletop system.
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Daniel S. Dessau, Ivan I. Smalyukh, Thomas J. Silva.
Subjects/Keywords: Femtomagnetism; Magnetic Multilayers; Magnetization; Spintronics; Ultrafast; X-ray; Condensed Matter Physics; Optics
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APA (6th Edition):
Turgut, E. (2014). Studying Laser-Induced Spin Currents Using Ultrafast Extreme Ultraviolet Light. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/108
Chicago Manual of Style (16th Edition):
Turgut, Emrah. “Studying Laser-Induced Spin Currents Using Ultrafast Extreme Ultraviolet Light.” 2014. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/108.
MLA Handbook (7th Edition):
Turgut, Emrah. “Studying Laser-Induced Spin Currents Using Ultrafast Extreme Ultraviolet Light.” 2014. Web. 05 Mar 2021.
Vancouver:
Turgut E. Studying Laser-Induced Spin Currents Using Ultrafast Extreme Ultraviolet Light. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/108.
Council of Science Editors:
Turgut E. Studying Laser-Induced Spin Currents Using Ultrafast Extreme Ultraviolet Light. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/phys_gradetds/108
University of Colorado
24.
Hogle, William Craig.
High Harmonic Driven Attosecond and Femtosecond Molecular Dynamics.
Degree: PhD, Physics, 2014, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/118
► To fully understand atomic and molecular dynamics scientists must be able to probe and study dynamics on their fundamental time scales. The motion, structure,…
(more)
▼ To fully understand atomic and molecular dynamics scientists must be able to probe and study dynamics on their fundamental time scales. The motion, structure, and arrangement of molecules play a fundamental role in chemical reactions. Analyzing these reactions is not only important for their immediate insights but the understanding is essential for the progress of many areas of science and technology including biology, material science, and medicine.
These dynamics require a light source with not only the time resolution to capture attosecond and femtosecond dynamics but one that can also reach a large energy range of interesting processes. High harmonic generation (HHG) provides a tunable coherent light source of high energy photons while remaining table-top in size. These highly excited states can be fully analyzed using coincidence electron and ion spectroscopy performed short time-scale resolution.
The combination of high harmonic generation with coincidence spectroscopy allows for the study of a variety of atomic and molecular systems. We were able to observe a new ionization pathway enabled by intense laser fields in argon and xenon. With helium, we demonstrate the ability to optically induce full electromagnetic transparency. The time resolved dissociation of bromine allowed for the understanding of how molecular orbital structure changes to become atomic in nature. In hydrogen we considered the interaction of electronic and nuclear wavepackets in a non-Born-Oppenheimer regime in a new level of detail. We explore the coherent control in dissociating a triatomic molecule with N
2O showing the ability to optically control the dissociation pathway of the molecule. Additional molecules including the argon dimer, ethylene and ozone have also been studied and analysis points to very interesting dynamics.
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Andreas Becker, Agnieszka Jaron-Becker, David Jonas.
Subjects/Keywords: atomic dynamics; molecular dynamics; molecular arrangement; high harmonic generation; electromagnetic transparency; dissociation pathway; Atomic, Molecular and Optical Physics
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APA (6th Edition):
Hogle, W. C. (2014). High Harmonic Driven Attosecond and Femtosecond Molecular Dynamics. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/118
Chicago Manual of Style (16th Edition):
Hogle, William Craig. “High Harmonic Driven Attosecond and Femtosecond Molecular Dynamics.” 2014. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/118.
MLA Handbook (7th Edition):
Hogle, William Craig. “High Harmonic Driven Attosecond and Femtosecond Molecular Dynamics.” 2014. Web. 05 Mar 2021.
Vancouver:
Hogle WC. High Harmonic Driven Attosecond and Femtosecond Molecular Dynamics. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/118.
Council of Science Editors:
Hogle WC. High Harmonic Driven Attosecond and Femtosecond Molecular Dynamics. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/phys_gradetds/118
University of Colorado
25.
Hoogeboom-Pot, Kathleen Marie.
Uncovering New Thermal and Mechanical Behavior at the Nanoscale Using Coherent Extreme Ultraviolet Light.
Degree: PhD, Physics, 2015, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/136
► Tremendous recent progress in nanofabrication capabilities has made high-quality single-atomic layers and nanostructures with dimensions well below 50 nm commonplace, enabling unprecedented access to…
(more)
▼ Tremendous recent progress in nanofabrication capabilities has made high-quality single-atomic layers and nanostructures with dimensions well below 50 nm commonplace, enabling unprecedented access to materials at the nanoscale. However, tools and techniques capable of characterizing the properties and function of nanosystems are still quite limited, leaving much of the fundamental physics that dominates material behavior in the deep nano-regime still unknown. Further understanding gained by studying nanoscale materials is critical both to fundamental science and to continued technological development. This thesis applies coherent extreme ultraviolet (EUV) light from tabletop high harmonic generation to study nanoscale systems on their intrinsic length and time scales (nanometers and femtoseconds, and above), specifically following thermal transport and acoustic dynamics. These studies have shown where and how nanostructured material properties can be quite different from their bulk counterparts. This has in turn allowed us to develop new theoretical descriptions to guide further work.
By observing heat dissipation from the smallest nanostructure heat sources measured to date (at 20 nm in lateral size), this work uncovers a previously unobserved and unpredicted nanoscale thermal transport regime where both size and spacing of heat sources play a role in determining the heat dissipation effciency. Surprisingly, this shows that nanoscale heat sources can cool more quickly when spaced close together than when far apart. This discovery is significant to the engineering of thermal management in nanoscale systems and devices while also revealing new insight into the fundamental nature of thermal transport. Furthermore, we harness this new regime to demonstrate the first experimental measurement of the differential contributions of phonons with different mean free paths to thermal conductivity, down to mean free paths as short as 14 nm for the first time.
The same technique is then applied to the study of acoustic waves in nanostructured materials, where they are used to characterize mechanical properties at the nanoscale. This thesis demonstrates the application of EUV nanometrology for the complete characterization of isotropic ultrathin films down to 50 nm in thickness across a broad range of stiffnesses. By simultaneously measuring both longitudinal and transverse waves, we are able to study trends in elastic properties that are normally assumed to be constant because it is difficult to measure them. This work also extends the technique to study anisotropic materials.
Finally, by observing the acoustic resonances of nanostructured ultrathin bilayers, this work is the first to apply EUV nanometrology to layers with sub-10nm thickness and to measure the mechanical properties of nanostructures down to single monolayer levels. Here it is shown that the density ratio of the ultrathin layers is not substantially altered from the bulk material counterpart, but the nanoscale elastic properties do deviate…
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Ronggui Yang, Mahmoud Hussein, Ivan Smalyukh.
Subjects/Keywords: High harmonic generation; Material elastic properties; Nanometrology; Nanoscale acoustic waves; Nanoscale thermal transport; Non-diffusive heat transfer; Atomic, Molecular and Optical Physics; Nanoscience and Nanotechnology
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APA (6th Edition):
Hoogeboom-Pot, K. M. (2015). Uncovering New Thermal and Mechanical Behavior at the Nanoscale Using Coherent Extreme Ultraviolet Light. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/136
Chicago Manual of Style (16th Edition):
Hoogeboom-Pot, Kathleen Marie. “Uncovering New Thermal and Mechanical Behavior at the Nanoscale Using Coherent Extreme Ultraviolet Light.” 2015. Doctoral Dissertation, University of Colorado. Accessed March 05, 2021.
https://scholar.colorado.edu/phys_gradetds/136.
MLA Handbook (7th Edition):
Hoogeboom-Pot, Kathleen Marie. “Uncovering New Thermal and Mechanical Behavior at the Nanoscale Using Coherent Extreme Ultraviolet Light.” 2015. Web. 05 Mar 2021.
Vancouver:
Hoogeboom-Pot KM. Uncovering New Thermal and Mechanical Behavior at the Nanoscale Using Coherent Extreme Ultraviolet Light. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Mar 05].
Available from: https://scholar.colorado.edu/phys_gradetds/136.
Council of Science Editors:
Hoogeboom-Pot KM. Uncovering New Thermal and Mechanical Behavior at the Nanoscale Using Coherent Extreme Ultraviolet Light. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/phys_gradetds/136
. 
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