Дисертації з теми "Higher order harmonics"
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Chowdhury, Rehana Momtaz Engineering & Information Technology Australian Defence Force Academy UNSW. "Use of Higher Order Harmonics from a Limiter to Improve the Single-Tone Detection Performance of an Envelope Detector." Awarded by:University of New South Wales - Australian Defence Force Academy. Engineering & Information Technology, 2009. http://handle.unsw.edu.au/1959.4/43512.
Повний текст джерелаSchapper, Florian. "Attosecond structure of high-order harmonics." Konstanz Hartung-Gorre, 2010. http://d-nb.info/1000540448/04.
Повний текст джерелаHammond, Thomas John. "Intracavity generation of high order harmonics." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/39747.
Повний текст джерелаWagner, Nicholas L. "High-order harmonic generation from molecules." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3303823.
Повний текст джерелаZhu, Xuemei. "A higher-order panel method for third-harmonic diffraction problems." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43339.
Повний текст джерелаKaassamani, Shatha. "Polarization Spectroscopy of High Order Harmonic Generation in Semiconductors Orbital angular momentum from semiconductor high-order harmonics All semiconductor enhanced highharmonic generation from a single nanostructured cone." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP091.
Повний текст джерелаSince its first observation, a decade ago, high harmonic generation (HHG) in crystals has proved to be an efficient, controllable and compact source of coherent XUV radiation. In this thesis, we investigate HHG in 2D materials, particularly graphene, and in different semiconductor crystals mainly zinc oxide, silicon, gallium arsenide and magnesium oxide. We find that the laser properties, such as its intensity, polarization and ellipticity, and the crystal properties are interrelated. Moreover, we shed the light on the role of the linear and nonlinear propagation effects mainly the Kerr effect, upon laser interaction with the crystal, which can significantly influence the high harmonic generation efficiency. Although this presents major limitations, we show that in some cases it turns out to be an advantage. Finally, we demonstrate the manipulation of the harmonic radiation at the source of the emission by patterning nanostructures to confine and enhance nanojoule laser pulses, and generate harmonic beams carrying orbital angular momentum. Lastly, we successfully image a micrometer-sized sample by the coherent diffractive imaging (CDI) technique based on solid-state harmonics
Kong, Fanqi. "High-Order Harmonic Generation with Structured Beams." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39609.
Повний текст джерелаYijian, Meng. "Extreme Ultraviolet Hyperspectral Coherent Diffractive Imaging." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/31928.
Повний текст джерелаBrimhall, Nicole. "Extreme Ultraviolet Polarimetry with Laser-Generated High-Order Harmonics." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1926.pdf.
Повний текст джерелаGoodell, Brian Carpenter, and Brian Carpenter Goodell. "Probing Intracavity Plasma Dynamics with Higher-Order Transverse Modes." Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/625686.
Повний текст джерелаTisch, John William George. "Studies of high harmonic generation using high power lasers." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309530.
Повний текст джерелаAlharbi, Abdullah F. "High-order Harmonic Spectroscopy of Cyclic Organic Molecules." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35179.
Повний текст джерелаHutchison, Christopher. "High-order harmonic generation in laser ablation plumes." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/40289.
Повний текст джерелаSutherland, Julia Robin Miller. "Phase-Matching Optimization of Laser High-Order Harmonics Generated in a Gas Cell." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd880.pdf.
Повний текст джерелаPfullmann, Nils [Verfasser]. "Nano-antenna-assisted high-order harmonic generation / Nils Pfullmann." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2012. http://d-nb.info/1031117709/34.
Повний текст джерелаAnderson, Patrick. "High-order harmonic generation with self-compressed femtosecond pulses." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/375102/.
Повний текст джерелаZhang, Pei. "Beam position diagnostics with higher order modes in third harmonic superconducting accelerating cavities." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/beam-position-diagnostics-with-higher-order-modes-in-third-harmonic-superconducting-accelerating-cavities(587aa24b-8adc-4bc6-8f5c-475aa0028d06).html.
Повний текст джерелаLohbreier, Jan. "Characterization and Optimization of High-order Harmonics after Adaptive Pulse Shaping." kostenfrei, 2008. http://www.opus-bayern.de/uni-wuerzburg/volltexte/2009/3047/.
Повний текст джерелаSpagnol, Marco. "Maintenance of electrical machines: Instantaneous Angular Speed analysis." Doctoral thesis, Università degli studi di Trieste, 2015. http://hdl.handle.net/10077/11102.
Повний текст джерелаThis research is focused on the condition monitoring of electrical machines and its long term purpose is to monitor electrical and mechanical faults at the same time, in non-stationary conditions (variable load and speed), with a single piece of hardware. The Instantaneous Angular Speed (IAS) measurement of an electrical machine is proposed and analysed in order to detect the fault development inside it. Chapter 1 introduces some basic principles about the maintenance of an electrical machine. Machine unscheduled downtimes are frequently caused by bearing faults, and rotor/stator faults. Monitoring systems are needed when the machine is very important for the plant (cost, safety). In this chapter, the electrical machine’s behaviour is also examined. Induction electrical machines have been chosen for this research. A review of the excitation frequencies is reported in the chapter. In the last section, characteristic fault frequencies (from mechanical and electrical sources) are collected. Chapter 2 presents the IAS measurement and its signal processing. The IAS is the measurement of the shaft rotating speed in order to visualize what’s happening during a single or in multiple turns. There are many measurement methods which are based either analogical to digital conversion or which use counters. Analogical to digital methods use a standard data acquisition board. Counter methods have to use specific hardware that is more expensive, but with less data to store. In this research, the counter method is used, combined with the Elapsed Time (ET) counting technique. Chapter 3 describes the encoder system. Its output signal is acquired with an oscilloscope and with the counter board. The signal’s differences are highlighted. In this chapter, the measurement’s source of errors are listed: the encoder’s geometrical error, the counter’s quantization error, the clock stability and the general electrical noise. Chapter 4 collects all the experimental tests done during the PhD research. Three experimental test rigs are shown and two measurements at Nidec ASI S.p.A. are reported. Note that the experimental test rigs were designed and built at the Università degli Studi di Trieste during the three years of the PhD. Experimental Test Rig 1 (ETR1) is used to understand the electrical motor’s behaviour with varying speed, the difference between the IAS and the speed acquired with the Torsional Laser Vibrometer, the difference between the IAS and the acceleration signal measured with an accelerometer located on the motor’s stator, the effect of the unbalance in the IAS measurement. Experimental Test Rig 2 (ETR2) allows to examine the load effect on the IAS measurement, the magneto-motive force harmonics, the slip and the rotor effects. Experimental Test Rig 3 (ETR3) is designed in order to detect the Inner Race Bearing Fault (Ball Pass Frequency Inner - BPFI) with varying load. The acceleration, the voltage and the current are compared with the Instantaneous Angular Speed. The motor is also tested with an unbalanced power supply. The two measurements at Nidec ASI S.p.A show how the IAS measurement could be implemented in an industrial machine larger than the one tested in the laboratory. This research presents the pros and cons of the IAS measurement, highlighting the capability of detecting BPFI bearing fault, feeling the load variations owing to the brake system (a synchronous generator), measuring the Fundamental Train Frequency of an healthy bearing, detecting unbalance in the rotor and other special features. The author would like to thank the Fondo Sociale Europeo, the Regione Friuli Venezia Giulia and Nidec ASI S.p.A (an electrical motor company) for the sponsorship and the collaboration during the three PhD years covered by the SHARM project ”Manutenzione Preventiva Integrata”.
Questo studio è focalizzato al monitoraggio dello stato di salute delle macchine elettriche con l'obbiettivo finale di monitorare danni meccanici ed elettrici, in condizioni non stazionarie (carico e velocità variabili), con un singolo sistema hardware. Viene quindi proposta ed analizzata la misura della Velocità Angolare Istantanea (Instantaneous Angular Speed - IAS) di una macchina elettrica allo scopo di prevedere l'insorgere di guasti al suo interno. Il Capitolo 1 introduce i principi base relativi alla manutenzione di macchine elettriche. Di frequente, le fermate non programmate sono conseguenti a danni su cuscinetti e su rotore/statore. I sistemi di monitoraggio sono indispensabili quando la macchina è molto importante nel contesto dell'impianto, considerazione esaminata sia dal punto di vista del costo che della sicurezza. In questo capitolo, viene analizzato anche il funzionamento della macchina elettrica. Dopo un'attenta valutazione, per lo sviluppo di questa ricerca sono state selezionate le macchine ad induzione asincrone. Nel capitolo è riportata anche un'analisi bibliografica sulle frequenze caratteristiche delle forzanti elettromagnetiche presenti. Nell'ultima sezione vengono elencate le frequenze tipiche dei danni rilevabili in misure di tipo vibrazionale ed elettrico. Il Capitolo 2 presenta la misura IAS. Questa rappresenta la misurazione della velocità di rotazione dell'albero e viene analizzata con accuratezza, individuando la relazione tra velocità di rotazione e le caratteristiche dell'encoder; inoltre vengono descritti i vari processamenti del segnale. Tale sistema permette di visualizzare ciò che sta accadendo alla macchina durante il suo funzionamento, in una o più rotazioni. Esistono metodi di misura basati o sulla conversione analogico-digitale o che prevedono l’impiego di contatori. I primi si servono di una scheda di acquisizione dati standard, mentre i secondi richiedono l'utilizzo di un hardware specifico, che alle volte può risultare più costoso, ma permette di acquisire i dati occupando una quantità inferiore di memoria. In questa tesi si è scelto di utilizzare un contatore per eseguire la misura IAS, sfruttando il conteggio Elapsed Time (ET). Il Capitolo 3 descrive l'encoder. Il segnale in uscita dal dispositivo viene acquisito con una scheda contatore e con un oscilloscopio in modo da confrontare ed analizzare le differenze presenti. In questo capitolo vengono elencate le tipologie di errore presenti nel sistema encoder: l'errore geometrico, l'errore di quantizzazione, l'errore dovuto alla stabilità del clock interno e l'errore dovuto a fonti esterni di rumore elettrico. Il Capitolo 4 raccoglie tutti i test sperimentali condotti durante il dottorato. Sono stati progettati e costruiti tre setup allo scopo di evidenziare particolari aspetti e problematiche; sono riportate anche due misure eseguite presso la sala prove dell'azienda Nidec ASI S.p.A. Il setup Experimental Test Rig 1 (ETR1) è stato utilizzato per conseguire le seguenti finalità: capire il funzionamento del motore elettrico con velocità variabile, analizzare la differenza della velocità acquisita con un torsiometro laser ed una scheda contatore, confrontare una misura vibrazionale (accelerometro posizionato sullo statore del motore) e la misura IAS, analizzare l'effetto dello sbilanciamento sulla misura IAS. Il setup Experimental Test Rig 2 (ETR2) permette di esaminare l'effetto del carico sulla misura IAS, le armoniche della forza elettromotrice, l'effetto dello slip e del rotore. Il setup Experimental Test Rig 3 (ETR3) è progettato in modo da evidenziare un difetto sulla guida interna di un cuscinetto, considerando anche un carico variabile. L'accelerazione, il voltaggio e la corrente sono confrontate con la Velocità Angolare Istantanea. Il motore viene testato anche applicando una tensione di alimentazione sbilanciata. Le due misure rilevate in Nidec ASI S.p.A dimostrano che la misura IAS può essere implementata in macchine industriali di grandi dimensioni e non solo nei setup di laboratorio. Questa ricerca espone gli aspetti positivi e negativi della misura IAS, evidenziando le capacità di individuare un danno sulla guida interna di un cuscinetto, captare le variazioni di carico prodotte dal freno (un generatore sincrono), misurare la Fundamental Train Frequency di un cuscinetto in buona salute, individuare uno sbilanciamento ed altre funzionalità. L'autore vuole ringraziare il Fondo Sociale Europeo, la Regione Friuli Venezia Giulia e l'azienda Nidec ASI S.p.A (produttore di macchine elettriche di medio-grandi dimensioni) per la sponsorizzazione e la collaborazione durante i tre anni di dottorato previsti dal progetto SHARM ”Manutenzione Preventiva Integrata”.
XXVII Ciclo
1983
Painter, John. "Direct observation of laser filamentation in high-order harmonic generation /." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1316.pdf.
Повний текст джерелаKurz, Heiko Gustav [Verfasser]. "High-order harmonic spectroscopy with water droplets / Heiko Gustav Kurz." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2014. http://d-nb.info/105103776X/34.
Повний текст джерелаKnapke, Robert. "High-Order Unsteady Heat Transfer with the Harmonic Balance Method." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1427962937.
Повний текст джерелаPainter, John Charles. "Direct Observation of Laser Filamentation in High-Order Harmonic Generation." BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/433.
Повний текст джерелаCheng, Rendy P. "A high-order, linear time-invariant model for application to higher harmonic control and flight control system interaction." College Park, Md. : University of Maryland, 2003. http://hdl.handle.net/1903/46.
Повний текст джерелаThesis research directed by: Aerospace Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
Brimhall, Nicole. "Extreme Ultraviolet Polarimetry with Laser-Generated High-Order Harmonics: Characterization of Uranium." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/1824.
Повний текст джерелаVoronov, Sergei Leonidovich. "Controlling laser high-order harmonic generation using weak counter-propagating light /." Diss., CLICK HERE for online access, 2003. http://contentdm.lib.byu.edu/ETD/image/etd146.pdf.
Повний текст джерелаVoronov, Sergei Leonidovich. "Controlling Laser High-Order Harmonic Generation Using Weak Counter-Propagating Light." BYU ScholarsArchive, 2002. https://scholarsarchive.byu.edu/etd/49.
Повний текст джерелаLytle, Amy Louise. "Phase matching and coherence of high-order harmonic generation in hollow waveguides." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3315842.
Повний текст джерелаCao, Wei. "Pump-probe study of atoms and small molecules with laser driven high order harmonics." Diss., Kansas State University, 2014. http://hdl.handle.net/2097/18161.
Повний текст джерелаDepartment of Physics
Itzhak Ben-Itzhak and Charles Lewis Cocke
A commercially available modern laser can emit over 10^15 photons within a time window of a few tens of femtoseconds (10^-15 second), which can be focused into a spot size of about 10 um, resulting in a peak intensity above 10^14 W/cm^2. This paves the way for table-top strong field physics studies such as above threshold ionization (ATI), non-sequential double ionization (NSDI), high order harmonic generation (HHG), etc.. Among these strong laser-matter interactions, high order harmonic generation, which combines many photons of the fundamental laser field into a single photon, offers a unique way to generate light sources in the vacuum ultraviolet (VUV) or extreme ultraviolet (EUV) region. High order harmonic photons are emitted within a short time window from a few tens of femtoseconds down to a few hundreds of attoseconds (10^-18 second). This highly coherent nature of HHG allows it to be synchronized with an infrared (IR) laser pulse, and the pump-probe technique can be adopted to study ultrafast dynamic processes in a quantum system. The major work of this thesis is to develop a table-top VUV(EUV) light source based on HHG, and use it to study dynamic processes in atoms and small molecules with the VUV(EUV)-pump IR-probe method. A Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) apparatus is used for momentum imaging of the interaction products. Two types of high harmonic pump pulses are generated and applied for pump-probe studies. The first one consists of several harmonics forming a short attosecond pulse train (APT) in the EUV regime (around 40 eV). We demonstrate that, (1) the auto-ionization process triggered by the EUV in cation carbon-monoxide and oxygen molecules can be modified by scanning the EUV-IR delay, (2) the phase information of quantum trajectories in bifurcated high harmonics can be extracted by performing an EUV-IR cross-correlation experiment, thus disclosing the macroscopic quantum control in HHG. The second type of high harmonic source implemented in this work is a single harmonic in the VUV regime (around 15 eV) filtered out from a monochromator. Experiments on D_2 molecules have been conducted using the 9th or the 11th harmonic as the pump pulse. Novel dissociative ionization pathways via highly excited states of D_2 have been revealed, thus suggesting potential applications for time-resolved studies and control of photochemistry processes.
Alves, Carla. "Studying ultrafast magnetization dynamics through Faraday effect and using linearly polarized high order harmonics." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS328.
Повний текст джерелаIn this thesis, we demonstrate that a linearly polarized XUV harmonic radiation can be employed in absorption spectroscopy to access the magnetization state of any type of sample, unlike all the techniques developed so far. Indeed, for the first time, time-resolved experiments were realized through the magneto-optical Faraday effect, which we exploit around the magnetically dichroic Co M2,3 absorption edge at 60 eV. The pump-probe technique was used to obtain the dynamic response of the magnetic samples upon laser excitation. The changes in the magnetization of the sample are associated to the changes in the polarization of the probe harmonic beam, i.e. the rotation of the polarization axis and the variation of the ellipticity. The main results of this thesis demonstrate that the measurement of the Faraday effect offers an ultra-sensitive way to characterize the magnetization of very thin films (only a few nm of magnetic materials). Moreover, since the Faraday effect takes place over a wide spectral range, it is possible to follow the simultaneous dynamics of different materials and thus to study very complex materials
Gaudiosi, David M. "High power ultrafast laser design and high-order harmonic generation in capillary discharge plasmas." Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3239457.
Повний текст джерелаYoshii, Kazumichi. "High-Order Harmonic Generation from Coherently Rotating Molecules with High-Intensity Ultrashort Laser Pulses." Kyoto University, 2010. http://hdl.handle.net/2433/120416.
Повний текст джерелаSchoun, Stephen Bradley. "Attosecond High-Harmonic Spectroscopy of Atoms and Molecules Using Mid-Infrared Sources." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1436853089.
Повний текст джерелаAghabarati, Ali. "Multilevel and algebraic multigrid methods for the higher order finite element analysis of time harmonic Maxwell's equations." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121485.
Повний текст джерелаLa méthode des éléments finis (FEM) appliquée à la dispersion des ondes et aux problèmes de champ de vecteurs quasi-statique dans le domaine fréquentiel mène à des systèmes d'équations linéaires rares, symétriques-complexes. Pour de grands problèmes ayant des géométries complexes, la plupart du temps et de la mémoire d'ordinateur utilisé par FEM va à la résolution de l'équation de la matrice. Les méthodes itératives de Krylov sont celles largement utilisées dans la résolution de grands systèmes creux. Elles dépendent fortement des préconditionnement qui accélèrent la convergence. Toutefois, l'application de préconditionnements conventionnels à l'opérateur "rot-rot" qui surgit en électromagnétisme vectoriel n'aboutit pas à des résultats satisfaisants et des techniques de préconditionnement spécialisés sont exigées.Cette thèse présente des techniques de préconditionnement efficaces multiniveau et multigrilles algébrique (AMG) pour l'analyse p-adaptative FEM. Dans la p-adaptation, des éléments finis de différents ordres polynomiaux sont présents dans le maillage et la matrice du système peut être structurée en blocs correspondant aux ordres des fonctions de base. Les nouveaux préconditionneurs sont basés sur un type d'inversion approximative à multiniveau p Schwarz (pMUS) du système structuré de bloc. Une correction à niveaux multiples en cycle V débute par l'application de Gauss-Seidel au niveau du bloc le plus élevé, suivi par le niveau inférieur, et ainsi de suite. De l'autre côté du V, des itérations de Gauss-Seidel sont appliquées en ordre inverse. Au bas du cycle se trouve le système d'ordre le plus bas, qui est habituellement résolu exactement avec un solveur direct. L'alternative proposée est d'utiliser l'espace auxiliaire de préconditionnement (ASP) au niveau le plus bas et de poursuivre le cycle en V vers le bas, d'abord en un ensemble d'auxiliaires, basé sur les espacements de nœuds, à travers une série de plus en plus petites de matrices générées par un multigrille algébrique (AMG). L'approche de grossissement algébrique est particulièrement utile aux problèmes ayant de fins détails géométriques, nécessitant une très grande maille dans laquelle la majeure partie des éléments restent à un niveau plus bas.En outre, pour des problèmes d'onde, la technique "décalé Laplace" est appliquée, dans laquelle une partie de l'algorithme ASP/AMG utilise une fréquence complexe perturbée. Une accélération de la convergence significative est atteinte. La performance des algorithmes de Krylov est davantage renforcée au cours du p-adaptation par l'incorporation d'une technique de déflation. Cette saillie fait dépasser hors du système préconditionné, les vecteurs propres correspondants aux plus petites valeurs propres. La construction du sous-espace de déflation est basée sur une estimation efficace des vecteurs propres à partir d'informations obtenues lors de la résolution du premier problème dans une séquence p-adaptatif. Des expériences numériques approfondies ont été effectuées et les résultats sont présentés à la fois aux problèmes d'onde et quasi-statiques. Les cas de test sont considérés comme compliqués à résoudre et les résultats numériques montrent la robustesse et l'efficacité des nouveaux préconditionnements. Les méthodes de Krylov de déflation préconditionnés par l'approche multiniveaux/ASP/AMG actuelle sont toujours considérablement plus rapides que les méthodes de référence et des accélérations allant jusqu'à 10 sont atteintes pour certains problèmes de test.
Steingrube, Daniel Sebastian [Verfasser]. "High-order harmonic generation with ultra-short pulses from filamentation / Daniel Sebastian Steingrube." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2011. http://d-nb.info/1014322367/34.
Повний текст джерелаGhimire, Shambhu. "Study on generation of attosecond pulse with polarization gating." Diss., Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/283.
Повний текст джерелаJin, Cheng. "Theory of nonlinear propagation of high harmonics generated in a gaseous medium." Diss., Kansas State University, 2012. http://hdl.handle.net/2097/13690.
Повний текст джерелаDepartment of Physics
Chii-Dong Lin
In this thesis, we establish the theoretical tools to investigate high-order harmonic generation (HHG) by intense infrared lasers in a gaseous medium. The macroscopic propagation of both the fundamental and the harmonic fields is taken into account by solving Maxwell’s wave equations, while the single-atom (or single-molecule) response is obtained by quantitative rescattering theory. The initial spatial mode of the fundamental laser is assumed either a Gaussian or a truncated Bessel beam. On the examples of Ar, N[subscript]2 and CO[subscript]2, we demonstrate that the available experimental HHG spectra with isotropic and aligned target media can be accurately reproduced theoretically even though the HHG spectra are sensitive to the experimental conditions. We show that the macroscopic HHG can be expressed as a product of a macroscopic wave packet and a photorecombination cross section, where the former depends on laser and experimental conditions while the latter is the property of the target only. The factorization makes it possible to retrieve the single-atom or single-molecule structure information from experimental HHG spectra. As for the multiple molecular orbital contribution in HHG, it causes the disappearance of the minimum in the HHG spectrum of aligned N[subscript]2 with the increase of laser intensity, and the position of minimum in HHG spectrum of aligned CO[subscript]2 depending on many factors is also attributed to it, which could explain why the minima observed in different laboratories may differ. For an important application of HHG as ultrashort light source, we show that measured continuous harmonic spectrum of Xe due to the reshaping of the fundamental laser field can be used to produce an isolated attosecond pulse by spectral and spatial filtering in the far field. For on-going application of using HHG to ionize aligned molecules, we present the photoelectron angular distribution from aligned N[subscript]2 and CO[subscript]2 in the laboratory frame, which can be compared directly with future experiments.
Augstein, B. B. "Orbit based treatments of quantum interference in atomic and molecular high-order harmonic generation." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1349184/.
Повний текст джерелаTortora, Alessandra. "Study and applications of the coherence properties of supercontinuum and high-order harmonic sources." Paris 6, 2006. http://www.theses.fr/2006PA066587.
Повний текст джерелаPaul, Ariel J. "Coherent EUV light from high-order harmonic generation: Enhancement and applications to lensless diffractive imaging." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3273819.
Повний текст джерелаViotti, Anne-Lise. "Efficient generation and characterization of soft x-ray by laser-driven high-order harmonic generation." Thesis, KTH, Tillämpad fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-185796.
Повний текст джерелаRawat, Vineet. "Finite Element Domain Decomposition with Second Order Transmission Conditions for Time-Harmonic Electromagnetic Problems." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243360543.
Повний текст джерелаLin, Nan. "Application of attosecond pulses to high harmonic spectroscopy of molecules." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-01064138.
Повний текст джерелаChambers, Michael. "Investigations of the brightness of high order harmonics generated by intense laser interactions with solid and gaseous targets." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298394.
Повний текст джерелаStaedter, David. "Femtosecond time-resolved spectroscopy in polyatomic systems investigated by velocity-map imaging and high-order harmonic generation." Toulouse 3, 2013. http://thesesups.ups-tlse.fr/2116/.
Повний текст джерелаRevealing the underlying ultrafast dynamics in molecular reaction spectroscopy demands state-of-the-art imaging techniques to follow a molecular process step by step. Femtosecond time-resolved velocity-map imaging is used to study the photodissociation dynamics of chlorine azide (ClN3). Here especially the co-fragments chlorine and N3 are studied on the femtosecond timescale in two excitation energy regions around 4. 67 eV and 6. 12 eV, leading to the formation of a linear N3 fragment and a cyclic N3 fragment, respectively. This work is the first femtosecond spectroscopy study revealing the formation of cyclic N3. Tetrathiafulvalene (TTF, C6H4S4) electronic relaxation is studied, while scanning the electronic excitation around 4 eV, by time resolved mass and photoelectron spectroscopy. As only few is known about the ion continuum about TTF the imaging photoelectron photoion coincidence (iPEPICO) technique is used in order to disentangle the complex ionic dissociation. The second part of the thesis is based on the generation and application of XUV light pulses by high-order harmonic generation with an intense femtosecond laser pulse in a molecular target. Two types of phase sensitive attosecond spectroscopy experiments were conducted to study the vibrational dynamics of SF6: one using strong field transient grating spectroscopy, where high-order harmonic generation takes place in a grating of excitation, and the second experiment using high-order harmonic interferometry using two intense XUV probe pulses. The temporal dependencies in phase and amplitude reveal the vibrational dynamics in SF6 and demonstrate that high-order harmonic generation is sensitive to the internal excitations. Last but not least, the use of high-order harmonics as a XUV photon source for the velocity-map imaging spectrometer is investigated. Using time-resolved photoelectron imaging, the relaxation dynamics initiated with 15. 5 eV in argon and 9. 3 eV in acetylene are revealed
Lévêque, Camille. "Pump-probe spectroscopy of vibronic dynamics using high-order harmonic generation : general theory and applications to SO2." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066513/document.
Повний текст джерелаThe SO2 molecule is long known in the literature for its complex UV absorption spectrum, which is caused by a variety of strong couplings between the electronic states involved. This long and rich history was augmented recently by new time-dependent spectroscopic methods, namely, Time-Resolved Photoelectron Spectroscopy (TRPES) and High-order Harmonic Generation (HHG). Additional open questions emerged immediately, e.g., what was the role of the different known electronic states, which were the relevant couplings and also the timescales of the different relevant processes.To resolve these issues theoretically, we start by considering the electronic ground state and the two lowest singlet excited states. The latter interact through non-adiabatic couplings leading to a complex photoabsorption spectrum. Our results were accurate, especially concerning the Clements bands, and provide a comprehensive description of the photoabsorption spectrum. When including the spin-orbit coupling, relevant for the weak long-wavelength absorption system, the three-states model turns into a 12 coupled-states system. Analysis of the different couplings gives insight into the different mechanisms of the intersystem crossing. Three main points are shown: (i) the preponderant role of a 3B2 state, (ii) the possibility of quantum interferences during the process and (iii) a new interpretation of the forbidden band.The TRPES and the HHG spectroscopies have been used to probe the time-dependent dynamics in all these states. With the aid of first-principles simulations we show that the TRPES method is sensitive to the dynamics in the manifold, while HHG is sensitive only to the intersystem crossing
Simoncig, Alberto. "The role of the electron recoiling mechanism in coherent light high-order harmonics generation: from the source to the applications." Doctoral thesis, Università degli studi di Trieste, 2010. http://hdl.handle.net/10077/3581.
Повний текст джерелаI processi di generazione di armoniche di ordine superiore (High-order Harmonic Generation o HHG) in gas inerti rappresentano, attualmente, la tecnica piu` promettente per la creazione di impulsi di luce coerente nell'estremo ultra-violetto (EUV) in una configurazione table-top. I processi HHG si basano sull'interazione non-lineare, tra impulsi laser ultra-corti, tipicamente dell'ordine della decina di femtosecondi, e atomi di gas inerti. Le caratteristiche che distinguono i processi HHG sono la loro durata temporale, che puo` essere nel dominio degli attosecondo e il fatto che l'interazione e` non perturbativa. Invece, la natura quantistica dei processi HHG implica la presenza di meccanismi di diffusione che influenzano la funzione d'onda dell'elettrone atomico coinvolto nell'interazione con il campo laser. Il ruolo della diffusione viene usualmente trascurato nella letteratura corrente, sebbene quest'ultima sia strettamente legata al controllo dell'efficienza del processo HHG e dello stato di polarizzazione dei fotoni generati. Il lavoro di tesi e` focalizzato sullo studio sperimentale e teorico/fenomenologico del ruolo dei meccanismi di diffusione, e sul loro controllo, al fine di incrementare l'efficienza e la qualita` ottica, i.e. coerenza, struttura temporale, etc., dei fotoni HHG prodotti. Gli studi e gli esperimenti condotti forniscono, in base alla nostra attuale conoscenza, la prima dimostrazione quantitativa a supporto del modello di Leweinstein. Accanto alla caratterizzazione spettrale, viene presentato uno studio accurato circa le condizioni minime necessarie a generare impulsi HHG, sempre legate al ruolo della diffusione della funzione d'onda elettronica. I risultati hanno permesso di ottenere una piu` profonda comprensione della complessa dinamica non-lineare, che sta alla base dei processi HHG. Accanto allo studio della diffusione si e` cercato di ottenere il controllo sullo stato di polarizzazione degli impulsi HHG, i quali mantengono la polarizzazione della radiazione laser utilizzata. La stessa diffusione impedisce di creare efficientemente armoniche di ordine superiore con polarizzazione ellittica (o circolare). Per risovere questo problema e` stata abbiamo sviluppato una collaborazione con il gruppo CXRO del Lawrence Berkeley National Laboratory, (Berkeley, USA), grazie al quale sono state realizzate una serie di ottiche multistrati innovative basate sul principio dell'angolo di Brewster, e disegnate appositamente per polarizzare circolarmente impulsi di luce EUV. Queste ultime sono state preliminarmente testate con successo sulla beam-line 6.3.2 del sincrotrone di Berkeley. La parte finale della tesi presenta la prima sorgente di impulsi HHG, polarizzati circolarmente utilizzando i citati multistrati. Per verificare l'efficienza e` di questi multistrati e` stato condotto un esperimento di dicroismo magnetico circolare con radiazioni EUV (EUV-MCD), unico nel sul genere, in quanto utilizza gli impulsi HHG polarizzati circolarmente per sondare il comportamento dicroico in corrispondenza delle soglie di assorbimento M di metalli ferromagnetici come Fe e Ni o delle loro leghe. Il fine ultimo e` dato dalla realizzazione di un esperimento risolto in tempo capace di utlizzare impulsi HHG circolarmente polarizzati per comprendere il processo di demagnetizzazione di sistemi ferromagnetici, sulla scala temporale del femtosecondo.
XXII Ciclo
1982
Risoud, François. "Theoretical study of attosecond dynamics in atoms and molecules using high-order harmonic generation as a self-probe." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066234/document.
Повний текст джерелаIn this thesis, I studied theoretically atoms and molecules interacting with a short, low-frequency and intense laser pulse, in the typical regime of high-order harmonic generation (HHG). We use HHG as a self-probe process to examine electronic and nuclear dynamics on the attosecond scale with Ångström resolution, insisting on the spectral phase. By using simple models, we are able to solve extensively the time-dependent Schrödinger equation, either numerically or with the Strong Field Approximation (SFA). Our models give us valuable physical insights on the underlying dynamical processes and intuitive explanations while keeping a predictive propensity. With efficient tools developed to analyze our numerical results, we first investigate the ionization dynamics through a shape resonance in a model molecule such as N2. Secondly, we take another look at two-center interferences, and uncover a very interesting behavior which is linked to the dressing of the electronic ground-state by the laser field. It is indeed confirmed by additional developments of molecular SFA. We predict that this behavior can be observed experimentally using quantum path interferences. Finally, we examine the effect of nuclear vibration in diatomic molecules by coupling consistently electronic and nuclear motions. Our results show that with short pulses, nuclear motion in the neutral molecule can be triggered by Raman effect. Thus, we invalidate an uncorrelated theory, so called Lochfraß, which focuses on the dependence of the ionization yield with internuclear distance as an explanation. Lastly, we question the extension within SFA of the notion of ionization potential in molecules
Beaulieu, Samuel. "Probing femtosecond and attosecond electronic and chiral dynamics : high-order harmonic generation, XUV free induction decay, photoelectron spectroscopy and Coulomb explosion." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0063/document.
Повний текст джерелаThis thesis manuscript is articulated around the investigation of the interaction between ultrashort light pulses and gas-phase atoms, polyatomic and chiral molecules. Using the toolboxes developed in attosecond and strong-field physics as well as in femtochemistry, our general goal is to reach a better understanding of subtle effects underlying ultrafast light-induced dynamics in matter.To do so, we developed cutting-edge near-infrared and mid-infrared few-cycle light sources, which were used to build a water-window soft-X-ray source based on high order harmonic generation (HHG), as well as to study new HHG channels involving highly-excited (Rydberg) states. The latter study revealed a delayed HHG emission from the ionization of Rydberg states and radiative recombination onto the electronicground state, triggering our interest in the role of Rydberg states in strong-field physics. This led us to investigate the laser-induced XUV Free Induced Decay from electronic wave packets as a new background-free 2D spectroscopic technique.More over, we have found out that strong-field interaction with a well prepared coherent superposition of electronic states led to the generation of hyper-Ramanlines concomitant with standard high-order harmonics. These spectral features were predicted in the early-days theoretical calculations of HHG but had never been reported experimentally.After these experiments in rare gas atoms, we moved to molecular targets, in whichlight-induced electronic excitation can trigger nuclear dynamics. Using simple benchmark molecules, we have studied dynamics involving the participation of both nuclear and electronic degrees of freedom: first, we studied the ultrafast non adiabatic photoisomerization of the acetylene cation into vinylidene cation, andsecond, we investigated the coherent control of electron localization during molecular photodissociation of H2+. The simplicity of these molecular targets enabled the comparison of the experimental results with state-of-the-art theoretical calculations,revealing the importance of the coupling between nuclear and electronic degrees of freedom in photoinduced molecular dynamics.The other major pillar of this thesis is the study of ionization of chiral molecules usingchiral light pulses. It has been known since the 70s that the ionization from an ensemble of randomly oriented chiral molecules, using circularly polarized light pulse,leads to a strong forward-backward asymmetry in the number of emitted photoelectrons, along the light propagation axis (Photoelectron Circular Dichroism,PECD). Prior to this thesis, PECD was widely studied at synchrotron facilities (single photonionization) and had recently been demonstrated using table-top lasers in resonant-enhanced multiphoton ionization schemes. In this thesis, we have shownthat PECD is a universal effect, i.e. that it emerges in all ionization regimes, from single photon ionization, to few-photon ionization, to above-threshold ionization, up to the tunneling ionization regime. This bridges the gap between chiral photoionizationand strong-field physics. Next, we have shown how the combination of standard femtochemistry approaches and PECD can be used to follow the dynamics of photoexcited chiral molecules using time-resolved PECD. Using similar experimental approaches, but by using pulse sequences with counter-intuitive polarization states,we have demonstrated a novel electric dipolar chiroptical effect, called Photoexcitation Circular Dichroism (PXCD), which emerges as a directional and chirosensitive electron current when multiple excited bound states of chiral molecules are coherently populated with chiral light. Last, we introduced a time-domain perspective on chiral photoionization by measuring the forward-backward asymmetry of photoionization delays in chiral molecules photoionized by chiral light pulses. Our work thus carried chiral-sensitive studies down to the femtosecond and attosecond ranges
Quintard, Ludovic. "Caractérisation et contrôle des profils spatiaux, spectraux et temporels de faisceaux XUV obtenus par génération d’harmoniques d’ordres élevés dans des gaz." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0641/document.
Повний текст джерелаWe present our work on the control of high order harmonic generation in gases.We first show how, by generating the harmonics outside the focus of the IR beam,it is possible to control the spatial phase of the harmonics in the generating mediumallowing to obtain a divergent, collimated or convergent wavefront. With this methodwe show that it is possible to focus the harmonics up to six Rayleigh length after thefocal point of the IR beam. Then we study XUV harmonic beams presenting structuredspacio-spectral distributions in the far field. In this study, we observe the influence ofthe diameter of an iris positioned before the focusing of the IR. In a third step we studymethods for controlling the harmonic spectrum. First, we finely control the harmonicscentral wavelength by modifiying the spectral content of the IR by adding two delayedIR pulses. Then we used the collective effects of the high order harmonic generationin order to foster a specific harmonic or a group of harmonics in the far field. Finally,we present a method for characterizing the duration of attosecond pulses in the timedomain. This method, called ionization ladder, uses ionization as a probe to measurepulse duration of up to hundreds of attosecond