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Source paramétrique dans l'infrarouge moyen à haute cadence / Parametric mid-IR source at high repetitionVan de walle, Aymeric 03 November 2016 (has links)
Ce manuscrit décrit l’étude et la mise en œuvre d’une source laser ultrarapide à taux de répétition élevé dans l’infra-rouge moyen, pour des applications à la physique des champs forts et à la spectroscopie moléculaire multidimensionnelle. Cette source est basée sur le phénomène d’amplification paramétrique optique à dérive de fréquence, qui permet la génération d’impulsions de quelques cycles optiques.Tout d’abord, nous présentons les applications de ces sources, ainsi que leurs paramètres importants, débouchant sur un cahier des charges pour la source à l’étude. Un état de l’art des sources paramétriques présentées dans la littérature scientifique nous permet ensuite d’appréhender la diversité des architectures et des performances atteintes. En particulier, nous soulignons les points cruciaux que sont la nature et les performances du laser de pompe, le mécanisme de génération du signal à amplifier, ainsi que la robustesse de la synchronisation temporelle entre le signal et la pompe.Nous étudions ensuite la possibilité d’émettre un signal autour de la longueur d’onde de 1,55 µm à partir d’impulsions femtoseconde de pompe à 1,03 µm par génération de supercontinuum dans un cristal massif de YAG. Nous menons ainsi une étude détaillée des propriétés de la partie infra-rouge du supercontinuum obtenu, en termes de contenu spectral, cohérence, propriétés statistiques tir à tir et long terme, et propriétés spatiales. Cette étude nous permet de conclure sur la validité de cette approche pour générer le signal à amplifier.Nous arrivons donc à définir une architecture inédite basée sur l’utilisation d’un laser de pompe basé sur un amplificateur à fibre dopée ytterbium de forte énergie délivrant des impulsions de 300 fs 400 µJ à la cadence de 125 kHz. La durée courte rendue possible par le choix de cette technologie de pompe nous permet de bénéficier d’un certain nombre d’avantages importants : la génération efficace de supercontinuum autour de 1,55 µm, ce qui entraine une synchronisation temporelle très robuste entre pompe et signal. D’autre part le couple étireur – compresseur est constitué de simples lames de matériaux massifs, ce qui permet une grande efficacité et une gestion simplifiée de la phase spectrale. Enfin, la courte durée de pompe augmente le seuil de dommage en intensité crête, ce qui permet l’utilisation de cristaux non linéaires courts et augmente la bande spectrale d’amplification. Des expériences supplémentaires sont menées pour étudier les phénomènes limitant la puissance au sein des cristaux de MgO:PPLN. Les étages d’amplification sont tous réalisés en géométrie colinéaire, ce qui permet d’utiliser le signal et l’idler sans introduction de chirp angulaire. Toutes ces caractéristiques permettent la génération de deux faisceaux en sortie portant des impulsions de 50 fs 20 µJ à 1550 nm et 70 fs 10 µJ à 3,1 µm. / This thesis describes the design and construction of an ultrafast high repetition rate laser source in the mid-IR, for applications in strong-field physics and multidimensional molecular spectroscopy. This source is based on optical parametric chirped-pulse amplification, allowing the generation of few-cycle pulses.We first present some applications of these lasers, along with important parameters, to define specifications for the considered source. We then briefly outline the state of the art of similar ultrafast sources described in the literature, to highlight the variety of architectures and performances. In particular, several key points are identified, namely the nature and performances of the pump laser source, the method to generate a seeding signal, and the robustness of temporal synchronization between pump and signal pulses.We proceed to study the possibility of emitting a seed signal around 1.55 µm wavelength by supercontinuum generation in a bulk YAG crystal from femtosecond pump pulses at 1.03 µm. A detailed analysis of the properties of the infrared spectral content of the supercontinuum is carried out, focusing on spectral bandwidth, coherence, shot-to-shot and long term stability, and spatial properties. This work allows us to conclude that supercontinuum generation is a valid approach to generate the seed signal.This leads us to define a novel architecture built around an ytterbium-doped fiber femtosecond pump source delivering 300 fs 400 µJ pulses at a repetition rate 125 kHz. The short pump pulse duration compared to bulk Yb:YAG or Nd:YVO4 based systems results in a number of important advantages. First, it allows efficient seeding at 1550 nm using supercontinuum generation directly from the pump pulses in a bulk YAG crystal, resulting in extremely robust passive pump – signal synchronization. The short pump pulse duration also allows the use of millimeter to centimeter lengths of bulk materials to provide stretching and compression for the signal and idler, which minimizes the accumulation of higher-order spectral phase. Finally, the shorter pump pulse duration increases the damage peak intensity, permitting the use of shorter nonlinear crystals to perform the amplification, which increases the spectral bandwidth of the parametric process. Additional experiments are performed to sort out the phenomena that limit power scaling in MgO:PPLN crystals. The OPCPA stages are all operated in collinear geometry, allowing the use of both signal and idler without the introduction of angular chirp on the latter. These points result in the dual generation of 70 fs 23 µJ signal pulses at 1550 nm and 60 fs 10 µJ idler pulses at 3070 nm from a simple setup.
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From few-cycle femtosecond pulse to single attosecond pulse-controlling and tracking electron dynamics with attosecond precisionWang, He January 1900 (has links)
Doctor of Philosophy / Department of Physics / Zenghu Chang / The few-cycle femtosecond laser pulse has proved itself to be a powerful tool for controlling the electron dynamics inside atoms and molecules. By applying such few-cycle pulses as a driving field, single isolated attosecond pulses can be produced through the high-order harmonic generation process, which provide a novel tool for capturing the real time electron motion. The first part of the thesis is devoted to the state of the art few-cycle near infrared (NIR) laser pulse development, which includes absolute phase control (carrier-envelope phase stabilization), amplitude control (power stabilization), and relative phase control (pulse compression and shaping). Then the double optical gating (DOG) method for generating single attosecond pulses and the attosecond streaking experiment for characterizing such pulses are presented. Various experimental limitations in the attosecond streaking measurement are illustrated through simulation. Finally by using the single attosecond pulses generated by DOG, an attosecond transient absorption experiment is performed to study the autoionization process of argon. When the delay between a few-cycle NIR pulse and a single attosecond XUV pulse is scanned, the Fano resonance shapes of the argon autoionizing states are modified by the NIR pulse, which shows the direct observation and control of electron-electron correlation in the temporal domain.
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Carrier-envelope phase stabilization of grating-based chirped-pulse amplifiersMoon, Eric Wayne January 1900 (has links)
Doctor of Philosophy / Department of Physics / Zenghu Chang / In this research, the carrier-envelope phase (CE phase) evolution of the pulse train from a Kerr-lens mode-locked chirped-mirror dispersion compensated Ti:Sapphire laser oscillator was stabilized. The offset frequency corresponding to the rate of change of the CE phase was obtained by spectrally broadening the oscillator pulses in a photonic crystal fiber and interfering the f and 2f components. An offset frequency linewidth of 100 mHz was obtained and could be locked over several hours. The effect of path length drift in the interferometer used for CE phase stabilization of the laser oscillator was investigated. By stabilizing the path length drift, the interferometer noise was reduced by several orders of magnitude. The CE phase drift through a grating-based chirped-pulse multi-pass amplifier was investigated. Varying the grating separation by 1μm in the stretcher was found to cause a shift of 3.7 +/- 1.2 rad of the CE phase. The CE phase could be stabilized to within 160 mrad rms error by feedback controlling the grating separation. By locking the path length in the f-to-2f interferometer used to stabilize the CE phase of the oscillator pulses, the fast (>3 Hz) CE phase drift of the amplified laser pulses was reduced from 79 to 48 mrad. It was also found that the CE phase could be shifted and set to any value within a 2π range by changing the grating separation. Also, the CE phase could be continuously modulated within a 2π range while maintaining a relative phase error of 171 mrad. The CE phase shift of a grating-based compressor was found to be stabilized to 230 mrad rms. The effect of laser power fluctuation on the CE phase measurement was also investigated. It was found that a 1% fluctuation of the laser energy caused a 160 mrad error in the CE phase measurement. A two-step model is proposed to explain the phase-energy coupling in the CE phase measurement. The model explains the experimentally observed dependence of the group delay between the f and 2f pulses on the laser energy. Few-cycle pulses were CE phase stabilized to 134 mrad rms and were used to perform above-threshold ionization and high harmonic generation.
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Generace fázově stabilních ultrakrátkých pulzů ve střední infračervené oblasti / Generation of carrier-envelope-stable few-cycle pulses in the mid-infrared spectral regionPeterka, Pavel January 2020 (has links)
In this thesis we present the realization of a source of 1.5-cycle carrier-envelope phase stable laser pulses in the mid-infrared spectral region. We used ytterbium laser system generating 1 µm pulses as a pump of setup, where the beam is split into several parts and interact in nonlinear optical media. 2 µJ pulses with duration 18 fs at 50 kHz repe- tition rate are produced. By spectral broadening in crystal GGG, 9,9 fs pulses can be achieved. The mid-IR pulses was characterized by third harmonics generation frequency resolved optical gating in the interferometric configuration. Fourier filtering of the mea- sured interferogram allows for the complete reconstruction of amplitude and phase of the ultrashort pulses generated by our setup. The pulses will in future serve for experimental investigation of ultrafast strong-field phenomena in solids. 1
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Neuartige Konzepte zur Detektion und Kontrolle der Carrier-Envelope Phasendrift ultrakurzer LaserimpulseGrebing, Christian 26 March 2010 (has links)
Diese Arbeit beschäftigt sich mit der Carrier-Envelope Phasendrift modengekoppelter Laser sowie Maßnahmen zu deren aktiver und passiver Stabilisierung. Das restliche Phasenrauschen wird in verschiedenen Messaufbauten im Hinblick auf physikalische Ursachen und mögliche Optimierungen untersucht. Dazu werden einführend verschiedene Interferometeranordnungen zur Messung der CEP Drift von Ti:Saphir Oszillatoren systematisch auf ihr Eigenrauschen hin untersucht. In einem Vergleichsexperiment wird die Überlegenheit kompakter Interferometeraufbauten demonstriert. Zusätzlich wird eine einfache Anordnung vorgestellt, welche die Bestimmung der Phase eines spektralen Interferenzmusters. Das analoge Verfahren wird zur Einzelschussanalyse der CEP Drift von Verstärkerimpulsen verwendet. Hiermit werden erstmals schnelle Rauschbeiträge aufgedeckt. Ergänzend wird ein Konzept zur orthogonalen Kontrolle der CEP Drift mithilfe einer speziellen Kompensatoreinheit diskutiert. Der Kompensator besteht aus zwei Keilprismen, hergestellt aus unterschiedlichen optischen Materialien, die als Einheit verschoben werden. Durch geeignete Wahl der Materialien werden Effekte auf die Gruppenlaufzeit oder deren Dispersion gleichzeitig eliminiert. Darüber hinaus wird ebenfalls erstmalig ein lineares Messverfahren demonstriert, das die CEP Drift auch für ps-Oszillatoren erschließt. Zur linearen Detektion wird die spektrale Interferenz aufeinander folgender Impulse eines Impulszuges aufgelöst, die mit einem Ringresonator überlagert werden. Abschließend wird ein neues Verfahren präsentiert, das einen Impulszug generiert, dessen Einzelimpulse eine identische Feldstruktur aufweisen. Dazu das Messsignal direkt an ein externes Rückstellelement übergeben ohne eine zusätzliche Regelschleife zu benötigen. Auf diese Weise können Bandbreitenprobleme der Regelschleife vermieden werden. Da Rückstellelement und Laser voneinander getrennt sind, bleibt der Laser in seinem Betrieb ungestört. / This work discusses the carrier-envelope phase drift of mode-locked lasers as well as techniques for its active and passive stabilization. In order to reveal the physical origin of the drift, the investigations focus on the analysis of residual phase noise. From the analysis, potential improvements are developed. For this purpose, in a first experimental approach, different interferometer configurations for CEP drift detection of Ti:sapphire oscillators are compared. Comparative studies clearly reveal the superiority of compact interferometer set-ups in terms of noise. In a second series of experiments, a simple assembly is introduced for the direct extraction of the phase from spectral interference patterns. The analog method is demonstrated with single-shot measurements and utilized for stabilization of the CEP drift of an amplifier system, thereby enabling monitoring of additional fast noise contributions for the first time. Moreover, a concept for orthogonal control of the CEP drift by a specially designed compensator assembly is discussed. This assembly consists of two thin wedge prisms made from different optical materials. By choosing an appropriate material group delay and its dispersion are eliminated synchronously. Furthermore, a linear method is presented that provides access to the CEP drift of ps-oscillators for the first time. The newly introduced much more general linear approach relies on resolving the spectral interference of subsequent pulses from a pulse train, which are superimposed utilizing a ring resonator. Finally, a technique is demonstrated that generates a pulse train consisting of single pulses with identical field structure. Particularly, the heterodyne signal is directly fed forward to the external feedback element, replacing the classical servo loop. Therefore, servo bandwidth limitations are eliminated. Since feedback element and laser oscillator are decoupled, the laser performance is not corrupted by side effects from the feedback.
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Infrared Few-Cycle Pulse Optical Parametric Amplifier / Kelių optinių ciklų trukmės impulsų parametrinis stiprinimas infraraudonojoje srityjeAlišauskas, Skirmantas 01 October 2010 (has links)
Main objective of this thesis is to generate and amplify few cycle pulses in the infrared region. In this thesis, two approaches were introduced for few cycle pulse parametric amplification at 800 nm and 1.5 μm. First approach is dedicated for prospects for increasing average power of OPCPA via multi-beam pumping; the second approach is dedicated for generation of carrier-envelope-phase (CEP) stable high energy (up to tens of millijoules) few-cycle pulses at 1.5 μm.
An experimental investigation of two or three beams-pumped OPCPA system based on type I BBO crystal is presented. The 2nd OPA stage was pumped by two or three pump beams derived from independent Nd:YAG laser amplifiers. The efficiency of interaction was shown to be comparable to that of single-beam pumped OPA and diminishes only slightly due to cascaded parametric diffraction of interacting waves. The effect was observed and its impact on efficiency of parametric amplification process was shown to decrease at larger intersecting angles of pump. In the prospect, the use of multiple lasers for OPA pumping has an appeal for increasing the repetition rate and consequently the average power of an ultrashort pulse laser system. Finally, the concept and realization of hybrid system based on type II KTP OPCPA and filamentation are described. A CEP-stable 1.5 μm OPCPA system with pulse energies up to 12.5 mJ after 4 OPA stages is demonstrated. Furthermore, self-compression of CEP-stable 2.2 mJ, 74.4 fs, 1.57 μm input... [to full text] / Disertacijos darbo tikslas – suformuoti ir parametriškai stiprinti kelių optinių ciklų trukmės impulsus infraraudonojoje srityje Šioje disertacijoje buvo tirtos dvi moduliuotosios fazės („čirpuotų“) impulsų parametrinio stiprinimo sistemos, stiprinančios ypač plataus spektro impulsus 800 nm bei 1,5 μm srityse. Pirmoji sistema skirta tirti galimybę didinti lazerinės spinduliuotės vidutinę galią keliais pluoštais kaupinamame parametriniame stiprintuve; antroji sistema skirta kelių optinių ciklų trukmės stabilios fazės impulsų formavimui 1,5 μm srityje.
Disertacijoje aprašomas I tipo parametrinis stiprintuvas, kurio 2-oji pakopa buvo kaupinama dviem arba trimis nepriklausomų lazerinių šaltinių pluoštais. Nustatyta, kad parametrinį stiprintuvą kaupinant keliais pluoštais stebimas naujų erdvinių komponentų atsiradimas, kuriuos sąlygoja parametrinė pakopinė difrakcija, o tai mažina bendrą sistemos energetinio keitimo efektyvumą.. Darbo metu pademonstruota galimybė mažinti parametrinės difrakcijos sąlygotus nuostolius parametriniame stiprintuve derinant kampus tarp kaupinimo pluoštų. Taip pat pristatomas alternatyvus būdas formuoti didelės energijos (kelių dešimčių milidžaulių) kelių optinių ciklų trukmės stabilios fazės impulsus 1,5 μm srityje. Būdas paremtas sąlyginai siauro spektro 1,5 μm srityje stiprinimu II tipo KTP kristale bei spektro plėtra inertinėse dujose po stiprinimo. 4 pakopų parametriniame stiprintuve pasiekta iki šiol didžiausia 12,5 mJ impulso energija 1,5 μm... [toliau žr. visą tekstą]
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Kelių optinių ciklų trukmės impulsų parametrinis stiprinimas infraraudonojoje srityje / Infrared Few-Cycle Pulse Optical Parametric AmplifierAlišauskas, Skirmantas 01 October 2010 (has links)
Disertacijos darbo tikslas – suformuoti ir parametriškai stiprinti kelių optinių ciklų trukmės impulsus infraraudonojoje srityje Šioje disertacijoje buvo tirtos dvi moduliuotosios fazės („čirpuotų“) impulsų parametrinio stiprinimo sistemos, stiprinančios ypač plataus spektro impulsus 800 nm bei 1,5 μm srityse. Pirmoji sistema skirta tirti galimybę didinti lazerinės spinduliuotės vidutinę galią keliais pluoštais kaupinamame parametriniame stiprintuve; antroji sistema skirta kelių optinių ciklų trukmės stabilios fazės impulsų formavimui 1,5 μm srityje.
Disertacijoje aprašomas I tipo parametrinis stiprintuvas, kurio 2-oji pakopa buvo kaupinama dviem arba trimis nepriklausomų lazerinių šaltinių pluoštais. Nustatyta, kad parametrinį stiprintuvą kaupinant keliais pluoštais stebimas naujų erdvinių komponentų atsiradimas, kuriuos sąlygoja parametrinė pakopinė difrakcija, o tai mažina bendrą sistemos energetinio keitimo efektyvumą.. Darbo metu pademonstruota galimybė mažinti parametrinės difrakcijos sąlygotus nuostolius parametriniame stiprintuve derinant kampus tarp kaupinimo pluoštų. Taip pat pristatomas alternatyvus būdas formuoti didelės energijos (kelių dešimčių milidžaulių) kelių optinių ciklų trukmės stabilios fazės impulsus 1,5 μm srityje. Būdas paremtas sąlyginai siauro spektro 1,5 μm srityje stiprinimu II tipo KTP kristale bei spektro plėtra inertinėse dujose po stiprinimo. 4 pakopų parametriniame stiprintuve pasiekta iki šiol didžiausia 12,5 mJ impulso energija 1,5 μm... [toliau žr. visą tekstą] / Main objective of this thesis is to generate and amplify few cycle pulses in the infrared region. In this thesis, two approaches were introduced for few cycle pulse parametric amplification at 800 nm and 1.5 μm. First approach is dedicated for prospects for increasing average power of OPCPA via multi-beam pumping; the second approach is dedicated for generation of carrier-envelope-phase (CEP) stable high energy (up to tens of millijoules) few-cycle pulses at 1.5 μm.
An experimental investigation of two or three beams-pumped OPCPA system based on type I BBO crystal is presented. The 2nd OPA stage was pumped by two or three pump beams derived from independent Nd:YAG laser amplifiers. The efficiency of interaction was shown to be comparable to that of single-beam pumped OPA and diminishes only slightly due to cascaded parametric diffraction of interacting waves. The effect was observed and its impact on efficiency of parametric amplification process was shown to decrease at larger intersecting angles of pump. In the prospect, the use of multiple lasers for OPA pumping has an appeal for increasing the repetition rate and consequently the average power of an ultrashort pulse laser system. Finally, the concept and realization of hybrid system based on type II KTP OPCPA and filamentation are described. A CEP-stable 1.5 μm OPCPA system with pulse energies up to 12.5 mJ after 4 OPA stages is demonstrated. Furthermore, self-compression of CEP-stable 2.2 mJ, 74.4 fs, 1.57 μm input... [to full text]
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High-repetition rate CEP-stable Yb-doped fiber amplifier for high harmonic generation / Stabilisation en CEP d’un amplificateur à fibre dopée Yb à haute cadence pour la génération d'harmoniques d’ordre élevéNatile, Michele 07 June 2019 (has links)
Depuis une vingtaine d’années, la physique attoseconde, via le phénomène de génération d’harmoniques d’ordres élevés (HHG), a permis de nombreuses avancées dans la compréhension des phénomènes de dynamique ultra-rapide. Les lasers femtoseconde émettant des impulsions de fortes énergies et de durées de quelques cycles optiques sont les outils indispensables à cette physique. De plus, la phase entre la porteuse et l’enveloppe (CEP) des impulsions doit être contrôlée. Récemment les lasers basés sur les fibres dopées ytterbium ont permis de transposer les expériences d’HHG à haute cadence. La stabilisation de la CEP pour ce type de systèmes constitue la brique manquante au développement de sources à haute cadence pleinement compatibles avec ces applications. Cette thèse a été consacrée à la stabilisation CEP d’un laser à fibre dopée ytterbium pour une application à la génération de rayonnement cohérent dans l’XUV à fort flux de photon. Dans la première partie nous présentons l’architecture d’une source à un taux de répétition de 100 kHz stable en CEP émettant des impulsions de 30 microjoules et 96 fs. Ce système constitue une preuve de principe pour les futures sources haute énergie. La stabilisation de CEP est assurée par une architecture hybride composée d’un injecteur stabilisé passivement suivi d’un amplificateur de puissance stabilisé activement. Un bruit résiduel de CEP inférieur à 400 mrad est obtenu dans différentes configurations, de la mesure courte durée (1 s) tir à tir jusqu’à la mesure sur une heure de fonctionnement. Dans la seconde partie nous présentons la mise au point d’une ligne HHG XUV optimisée à 13 nm sur les paramètres d’un laser à fibre, pour des applications à l’imagerie par diffraction cohérente. / In the last two decades, attosecond physics, based on the high harmonic generation (HHG) phenomenon, has allowed a better understanding of ultrafast dynamics in the microcosm. High-energy few-cycles carrier-envelope phase (CEP) stabilized sources are the main enabling tools for this physics. Recently, temporally compressed Ytterbium-doped fiber amplifiers have been successfully used as high XUV photon flux HHG drivers. CEP stabilization of these sources would ensure their full compatibility with attoscience. The thesis is devoted to the CEP stabilization of a high repetition rate Yb-doped fiber femtosecond source, for high XUV photon flux beamline applications. In the first part, we present the architecture of such a source at 100 kHz repetition rate delivering 30 microjoules 96 fs CEP-stable pulses. It constitutes a test bench for future energy-scaled few-cycle sources. The CEP stabilization is ensured in a hybrid architecture including a passively stabilized frontend followed by an actively stabilized power amplifier. A residual CEP noise <400 mrad is measured using various setups, including a shot-to-shot measurement over 1 s and a long-term stability over 1 h. In the second part, we discuss the design of a high flux HHG beamline optimized for a future generation of fiber-based driver at 13 nm for applications to coherent diffraction imaging.
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Ultrarychlé vysoce nelineární procesy v diamantu / Ultrafast highly nonlinear processes in diamondZukerstein, Martin January 2020 (has links)
Intense few-cycle laser pulses can significantly affect the properties of transparent solids during the interaction. These processes take place on femtosecond time scales and they can be studied using ultrafast spectroscopic methods. This dissertation deals with highly nonlinear processes in diamond. In the interaction with a crystalline diamond, we observed a strong nonlinear broadening of the spectrum due to self-phase modulation effect, which allowed us to create a simple technique for compression of pulses from laser oscillator. At the same time, strongly nonlinear five-photon absorption was observed, in which we found a significant anisotropy and dependence on the polarization state. With two-beam pump and probe experiments we present a study of anharmonic phenomena in the dynamics of coherent phonons in diamond, additionally we created a new detection technique of lattice vibrations using multiphoton absorption. Finally, the high time resolution of the experiments revealed that the sub-picosecond electron dynamics strongly depends on the composition and morphology of the polycrystalline diamond thin films. The experimental results of this work provide comprehensive research into the interaction of diamond with few-cycle laser pulses and the development of new spectroscopic methods.
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Laser-driven molecular dynamics: an exact factorization perspectiveFiedlschuster, Tobias 19 January 2019 (has links)
We utilize the exact factorization of the electron-nuclear wave function [Abedi et al., PRL 105 123002 (2010)] to illuminate several aspects of laser-driven molecular dynamics in intense femtosecond laser pulses. Above factorization allows for a splitting of the full molecular wave function and leads to a time-dependent Schrödinger equation for the nuclear subsystem alone which is exact in the sense that the absolute square of the corresponding, purely nuclear, wave function yields the exact nuclear N-body density of the full electron-nuclear system. As one remarkable feature, this factorization provides the exact classical force, the force which contains the highest amount of electron-nuclear correlations that can be retained in the quantum-classical limit of the electron-nuclear system.
We re-evaluate the classical limit of the nuclear Schrödinger equation from the perspective of the exact factorization, and address the long-standing question of the validity of the popular quantum-classical surface hopping approach in laserdriven cases. In particular, our access to the exact classical force allows for an elaborate evaluation of the various and completely different potential energy surfaces frequently applied in surface hopping calculations.
The highlight of this work consists in a generalization of the exact factorization and its application to the laser-driven molecular wave function in the Floquet picture, where the molecule and the laser form an united quantum system exhibiting its own Hilbert space. This particular factorization enables us to establish an analytic connection between the exact nuclear force and Floquet potential energy surfaces.
Complementing above topics, we combine different well-known and proven methods to give a systematic study of molecular dissociation mechanisms for the complicated electric fields provided by modern attosecond laser technology.:Contents
Introduction
1 The exact factorization of time-dependent wave functions
1.1 Concern and state of the art
1.2 The exact factorization of the electron-nuclear wave function
1.3 The generalized exact factorization
1.4 The exact factorization for coupled harmonic oscillators
1.5 The exact factorization for a single particle with spin
1.6 The exact factorization of the laser-driven electron-nuclear wave function in the Floquet picture
1.7 Summary and conclusion
2 Quantum-classical molecular dynamics from an exact factorization perspective
2.1 Concern and state of the art
2.2 The exact nuclear TDSE
2.3 The Wigner-Moyal equation for the nuclear TDSE and its classical limit
2.4 The Bohmian formulation of the nuclear TDSE and its classical limit
2.5 Comparative calculations
2.5.1 Scenario 1: stationary states
2.5.2 Scenario 2: laser-driven dynamics
2.6 Summary and conclusion
3 Surface hopping in laser-driven molecular dynamics
3.1 Concern and state of the art
3.2 Surface hopping
3.3 Quantum-classical dynamics on the EPES
3.4 The benchmark model and its potential energy surfaces
3.5 Surface hopping in laser-driven molecular dynamics
3.6 Summary and conclusion
4 Beyond the limit of the Floquet picture: molecular dissociation in few-cycle laser pulses
4.1 Concern and state of the art
4.2 Theoretical few-cycle pulses
4.3 Calculation of dissociation probabilities
4.4 Dissociation in few-cycle pulses
4.4.1 Dissociation in half-cycle pulses
4.4.2 Dissociation in few-cycle pulses
4.5 Dissociation in realistic attosecond pulses
4.6 Summary and conclusion
Outlook
Appendices
A List of abbreviations
B Numerical details
C Calculating electronic observables within quantum-classical molecular dynamics
D Ionization in few-cycle pulses
E Modeling an optical attosecond pulse
Bibliography
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