Дисертації з теми "TeraHertz phonons"
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Li, Xian Ph D. Massachusetts Institute of Technology. "Terahertz-field-induced nonlinearity in phonons, electrons and spins." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122713.
Повний текст джерелаCataloged from PDF version of thesis.
Includes bibliographical references (pages 189-210).
In this thesis, I describe work aimed at understanding nonlinear material responses initiated by strong terahertz (THz) field excitation. I discuss two aspects of nonlinear THz spectroscopy in condensed-matter materials: developments of experimental THz capabilities and spectroscopy methods and their applications in investigating ultrafast nonlinear dynamics in different classes of materials. I first describe the THz generation, detection and spectroscopy methods, which are the basis of all of our studies. We have generated strong single- and multi-cycle THz pulses covering several spectral ranges using inorganic and organic crystals and developed linear and nonlinear THz spectroscopy techniques to interrogate light-matter interactions based on different observables and/or symmetry criteria.
We have demonstrated a new method for studying time-domain electron paramagnetic resonance that allows us to measure THz-frequency fine structures of spin energy levels on a tabletop and have developed nonlinear two-dimensional (2D) magnetic resonance spectroscopy to distinguish nonlinear THz-spin interaction pathways. We also show that THz-pump, optical-probe spectroscopy, including THz field-induced second-harmonic generation spectroscopy and THz Kerr effect spectroscopy, can be extended to study phase transitions in quantum paraelectric and topological materials. We have employed the THz methods to drive and detect nonlinear responses from several degrees of freedom in the materials. We have demonstrated collective coherent control over material structure by inducing a quantum paraelectric to ferroelectric phase transition using intense THz electric fields in strontium titanate.
We show that a single-cycle THz field is able to drive ions along the microscopic pathway leading directly to their locations in a new crystalline phase on an ultrafast timescale. We have driven highly nonlinear lattice and electronic responses in a topological crystalline insulator by dynamically perturbing the protecting crystalline symmetry through THz phonon excitation. We have observed oscillations in optical reflectivity that may be associated with electronic gap opening and modulation in the topological surface states. Finally, we have demonstrated nonlinear manipulation of collective spin waves in a canted antiferromagnet using strong THz magnetic fields and we have observed full sets of the second- and third-order nonlinear responses in 2D THz magnetic resonance spectra, which are accurately reproduced in our numerical simulations.
by Xian Li.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Chemistry
Warren, Matthew Timothy. "Time-Domain Terahertz Studies of Strongly Correlated GeV4S8 and Osmate Double-Perovskites." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1512066420271281.
Повний текст джерелаKasai, S., T. Katagiri, J. Takayanagi, K. Kawase, and T. Ouchi. "Reduction of phonon resonant terahertz wave absorption in photoconductive switches using epitaxial layer transfer." American Institite of Physics, 2009. http://hdl.handle.net/2237/12632.
Повний текст джерелаHibberd, Morgan. "Studying low frequency vibrational modes using ultrafast techniques." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/studying-low-frequency-vibrational-modes-using-ultrafast-techniques(4f2da8db-befe-4c37-a6ae-42d069c54dd5).html.
Повний текст джерелаFreeman, Will. "Terahertz quantum cascade structures using step wells and longitudinal optical-phonon scattering." Monterey, Calif. : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/dissert/2009/Jun/09Jun%5FFreeman%5FPhD.pdf.
Повний текст джерелаDissertation supervisor: Karunasiri, Gamani. "June 2009." Description based on title screen as viewed on July 14, 2009. Author(s) subject terms: Terahertz, THz, Quantum cascade structure, QC structure, Quantum cascade laser, QCL, Step well, Longitudinal optical-phonon, LO-phonon, Electron-phonon scattering, Electronelectron scattering, Impurity scattering, Interface roughness scattering, Optical transition, Electron transport, Monte Carlo method, Metal-metal waveguide, Surface plasmon waveguide Includes bibliographical references (p. 103-108). Also available in print.
Mährlein, Sebastian F. [Verfasser]. "Nonlinear Terahertz Phononics: A Novel Route to Controlling Matter / Sebastian F. Mährlein." Berlin : Freie Universität Berlin, 2017. http://d-nb.info/1135608059/34.
Повний текст джерелаKnighton, Brittany E. "Nonlinear Ultrafast Excitation and Two-Dimensional Terahertz Spectroscopy of Solids." BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/9190.
Повний текст джерелаNguema, Agnandji Edwin. "Génération et détection Terahertz : application à la caractérisation de matériaux en couches minces." Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13796/document.
Повний текст джерелаThis work concerns the characterization of thin film materials by terahertz time domain spectroscopy. For this purpose, we elaborated a terahertz setup in which the terahertz emission and terahertz detection are based on the use of femtosecond laser, semiconductors, ultrafast photoswitches or electro-optic crystals. The study of dielectric function of ferroelectrics thin film (barium titanate/-Ba1-xSrxTiO3) with temperature, give the importance of soft phonon mode. Finally, the electromagnetic behavior of conducting polymers based on polyaniline was made, in particular their shelding effectiveness in millimeter and sub-millimeter length
Souza, Fabricio Macedo de. "Dinâmica de plasma e fônon e emissão de radiação terahertz em superfícies de GaAs e telúrio excitadas por pulsos ultracurtos." Universidade de São Paulo, 2000. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-18112013-111000/.
Повний текст джерелаAbove-band-gap optical excitation of semiconductors generates highly non-equilibrium photocarriers which interact with phonons thus exciting vibrational modes in the system. This interaction induces refractive-index changes via the electro-optic effect. Moreover it gives rise to electromagnetic radiation at characteristic frequencies (terahertz). Both effects have been measured by time-resolved ultra fast spectroscopy. Recent pump-probe experiments have found strong modulations of the internal electric field through electro-optic measurements. The emitted electromagnetic radiation has also been detected by a terahertz dipole antenna. Both electro-optic and terahertz emission measurements provide information about the coupled dynamics of photocarriers and phonons. In this work we simulate the dynamics of plasmon-phonon coupled modes in n-GaAs and Tellurium (bulk) following ultrafast laser excitation. The time evolution of the photocarrier densities and currents is described semi classically in terms of the moments of the Boltzmann equation. Phonon effects are accounted for by considering a phenomenological driven-harmonic-oscillator equation, which is coupled to the electron-hole plasma via Poisson\'s equation. These equations constitute a coupled set of differential equations. We use finite differencing to solve these equations. From the numerical results for the evolution of internal fields we can calculate both the characteristic frequencies of system and its terahertz radiation spectrum. Our results are consistent with recent experimental data
Vassant, Simon. "Contrôle optique et électrique de réflectivité THz assistée par phonon-polaritons de surface." Phd thesis, Ecole Centrale Paris, 2011. http://tel.archives-ouvertes.fr/tel-00601767.
Повний текст джерелаArchambault, Alexandre. "Optique des ondes de surface : super-résolution et interaction matière-rayonnement." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00678073.
Повний текст джерелаBöttge, Christoph N. [Verfasser], and Mackillo [Akademischer Betreuer] Kira. "On the Phonon Interactions and Terahertz Excitations among Coulomb-correlated Charge Carriers of Semiconductors / Christoph N. Böttge. Betreuer: Mackillo Kira." Marburg : Philipps-Universität Marburg, 2013. http://d-nb.info/1043316590/34.
Повний текст джерелаDolguikh, Maxim. "MONTE CARLO SIMULATION OF HOLE TRANSPORT AND TERAHERTZ AMPLIFICATION IN MULTILAYER DELTA DOPED SEMICONDUCTOR STRUCTURES." Doctoral diss., University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3882.
Повний текст джерелаPh.D.
Department of Physics
Arts and Sciences
Physics
Weerasekara, Aruna Bandara. "Electrical and Optical Characterization of Group III-V Heterostructures with Emphasis on Terahertz Devices." Digital Archive @ GSU, 2007. http://digitalarchive.gsu.edu/phy_astr_diss/16.
Повний текст джерелаMai, Thuc T. "Optical spectroscopy of cooperative phenomena and their symmetries in solids." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555629359625425.
Повний текст джерелаLegrand, Romain. "Acoustique - étude et utilisation de nouvelles sources et transducteurs aux longueurs d'onde nanométriques." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2013. http://tel.archives-ouvertes.fr/tel-00945558.
Повний текст джерелаChen, I.-Ju, and 陳怡如. "Ultrafast Carrier Relaxation and Sub-Terahertz Longitudinal Coherent Acoustic Phonon Generation Studies in Graphene." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/09872783133772347645.
Повний текст джерела國立臺灣大學
光電工程學研究所
101
Graphene is a two-dimensional honeycomb lattice of carbon atoms. Due to its superior qualities, for example, it’s transparent, its thermal conductivity outperforms any other materials, its charge-carrier mobility is extremely high, and it is mechanically extremely strong, it has tremendous potential for future applications. For example, it’s a promising candidate for the conducting channel of future ultrafast field effect transistors and the replacement for the transparent electrode in touching screens, liquid crystal display (LCD), and solar cells. In this thesis, one of graphene’s undiscovered potential will be studied: graphene’s atomic thickness is one order thinner than any realistic metal films, which are usually used as the acoustic transducers in ultrafast acoustic devices and acoustic microscopy. Hence, graphene is a promising material to generate extremely broad band-width coherent acoustic phonons, because metal film transducers typically generate longitudinal coherent acoustic phonons with band-width inversely proportional to the film thickness. Moreover, unlike other broad band-width acoustic transducers, graphene is easily fabricated can be transferred onto all kinds of substrates. Thus, the usage of graphene can help applying acoustic microscopy to all kinds of materials. In the above applications, clear understanding about the carrier dynamics of supported monolayer graphene is critical. In this thesis, femtosecond infrared pump-probe spectroscopy together with theoretical analyses were used to study the ultrafast carrier dynamics of graphene. The characteristic times, sequences, and dominance of several hot carriers’ efficient relaxation channels, including carrier-carrier, carrier-phonon, and phonon-phonon interaction were studied. Moreover, by comparing the ultrafast carrier dynamics of our own graphene samples and pristine graphene, which was theoretically predicted or experimentally observed in previous literatures, we can have a clue of the differences between our own sample and pristine graphene due to fabrication methods and the usage of substrates. Then, pump-probe spectroscopy was also used to study whether coherent acoustic phonons that propagate into the substrate can be generated by photo-excitation of the supported monolayer graphene. First, through the observation of backward Brillouin oscillations with graphene deposited on glass, sapphire and GaN, it was verified that via photo-excitation of the monolayer graphene, coherent acoustic phonons with momentum in the out-of-plane direction were generated and had propagated into the substrate. This result suggested that by depositing monolayer graphene on top of a substrate, it can serve as an acoustic transducer. Afterwards, in order to reveal the full spectrum of the generated coherent acoustic phonons, a GaN crystal with a piezoelectric InGaN quantum well buried inside was used as the substrate. With our 3nm InGaN quantum well, detection band-width up to 2THz was achieved. The experimental results showed that the generated coherent acoustic phonon pulse had a bipolar shape and frequency components extending up to 1 THz (with the peak at 200GHz). In summary, by photo-exciting supported monolayer graphene, in spite of the two-dimensional nature of graphene, THz band-width coherent acoustic phonons that propagate perpendicularly to the surface and into the substrate can be generated. Hence, our study has confirmed the feasibility of using supported monolayer graphene as a THz acoustic transducer. A hypothesis based on the ultrafast carrier dynamics study of our supported graphene sample was brought up to elucidate the generation mechanism. A good correspondence was reached between the characteristics of the experimentally observed coherent acoustic phonon pulse and the prediction of the hypothesis.
Chen, Ting-Yang, and 陳廷揚. "Annealing Temperature Dependence of Phonon Modes and Crystallinity on Perovskites Studied by Terahertz Spectroscopy." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/6c9pyv.
Повний текст джерела國立交通大學
光電工程研究所
107
Hybrid halide perovskites have become one of the most promising solar cell materials, due to their great advantages of simple fabrication, lower cost, strong absorption, and good mobility. There have been tremendous efforts to improve the conversion efficiency of perovskite-based photovoltaic devices and now it reaches over 22.5 %. Recently, two-dimensional (2D) perovskites have attracted great attention in light emitting device community. Some studies have pointed out that 2D perovskites have higher stability under atmospheric environment. The thermal stability is another very important property for the out-door applications. In this work, we employed the broadband time-domain terahertz spectroscopy to study the low frequency phonon vibration mode of the alkylammonium lead iodides (XAPbI3); ethylammonium (EAPbI3), propylammonium ((PA)2PbI4), and butylammonium lead iodide ((BA)2PbI4). We found that the phonon mode corresponding to the bending vibration of I-Pb-I disappears for three layered perovskites and those at 1.5 and 2 THz due to the bonding length variety of Pb-I blueshift as the length of alkylammonium chain increases. In order to understand the thermal stability of layered perovskites, we measured the phonon modes under different thermal annealing temperatures. For three-dimensional perovskite, CH3NH3PbI3 (MAPbI3), the onset of blueshift of phonon mode is observed when the temperature reaches at about 65 ℃, where tetragonal-to-cubic phase transition occurs. When covered with monolayer graphene or transition metal dichalcogenides, the blueshift of mode frequency was not observed, implying the improvement thermal stability. For layered perovskites, the phonon modes at 1.5 and 2 THz is nearly unchanged as the temperature increases upto 100 ℃, indicating high thermal stability of 2D perovskites. The x-ray diffraction measurements show that the thermal annealing of 2D perovskites improves the crystallinity to ordered phase.
Gerecht, Eyal. "Development of niobium nitride hot electron bolometric mixer for terahertz frequencies: The phonon-cooled version." 1998. https://scholarworks.umass.edu/dissertations/AAI9841871.
Повний текст джерелаKübler, Carl [Verfasser]. "Femtosecond terahertz studies of many body correlations : from ultrafast phonon plasmon dynamics to an insulator metal transition / vorgelegt von Carl Kübler." 2007. http://d-nb.info/986197246/34.
Повний текст джерела