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Gil, Villalba Abel. "Single shot ablation of monolayer graphene by spatially shaped femtosecond laser pulses". Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCD028/document.
Pełny tekst źródłaSince its isolation in 2004, graphene has emerged has a potential material for next generation technologies.Graphene was the first truly 2D material produced. The interest in this material is due to its outstandingproperties: graphene is the lightest and strongest material known. It has a large electronic mobility andthermal conductivity. To enable the development of technological applications at industrial scale, fast patterningtechniques, operable at sub-micron scale are needed.This thesis focuses on the requirement of a fast, easily reconfigurable, low cost method to pattern graphene.The aim of our research is to determine the possibilities and constraints of ultrafast laser ablation of CVDgraphene at sub-micron scale. Using ultrafast laser to pattern graphene layers is interesting due to the abilityof femtosecond laser pulses to accurately depositing a high energy density in confined regions.We performed a set of experiments using non-diffractive shaped-beams to characterize the parametersrequired to control laser material processing at such small scale. We determined laser patterningcharacteristics on CVD monolayer graphene such as the ablation threshold and the ablation probability. To thisaim, we have developed a novel technique to measure ablation threshold that is independent of the ablated sizeand reported unexpected deviation from the threshold model, we also investigated the influence of differentdielectric substrates and the effect of the presence of graphene grain boundaries. From our experimentalresults we conclude that direct single shot laser patterning is a very effective method to pattern features above 1 µm, but below this dimension, novel illumination strategies are needed
Chanal, Margaux. "Space-time study of energy deposition with intense infrared laser pulses for controlled modification inside silicon". Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0488/document.
Pełny tekst źródłaThe modification of bulk-silicon is realized today with infrared nanosecond lasers. However, the interest regime for controlled modifications inside transparent materials is femtosecond pulses. Today, there is no demonstration of a permanent modification in bulk-Si with ultra-short laser pulses (100 fs). To increase our knowledge on the interaction between femtosecond lasers and silicon, we have developedultra-fast infrared microscopy experiments. First, we characterize the microplasma confined inside the bulk, being the generation of free-carriers under nonlinear ionization processes, followed by the complete relaxation of the material. These results, combined with the reconstruction of the beam propagation inside silicon, demonstrate that the energy deposition is strongly limited by nonlinear absorption andpropagation effects. This analysis has been confirmed by a numerical model simulating the nonlinear propagation of the femtosecond pulse. The understanding of this clamping has allowed us the development of new experimental arrangements, leading to the modification of the bulk of Si with short pulses
Remy, Quentin. "Ultrafast spin dynamics and transport in magnetic metallic heterostructures". Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0191.
Pełny tekst źródłaThe control of magnetization, and thus spin, at the shortest timescale, is a fundamental subject for the development of faster data storage devices. The capability to encode information with femtosecond laser pulses on magnetic metals such as GdFeCo or MnRuGa within a few picoseconds was a significant step towards the realization of such a technology. However, the reversal of magnetization observed in these materials upon a single laser pulse irradiation, called All Optical Helicity Independent Switching (AO-HIS), is still limited to a small class of ferrimagnetic materials and its physical mechanism is not completely understood.In this work, we study AO-HIS in magnetic thin films composed of a single or two GdFeCo layers with different alloy compositions. We show that these layers generate spin currents that can affect the AO-HIS of these materials. In particular, we can use such spin currents to reverse the magnetization of various ferromagnetic multilayers, with a single femtosecond laser pulse, which would otherwise only demagnetize and never switch. Playing with the GdFeCo alloy concentration and the ferromagnetic multilayer Curie temperature, we can tune the energy required to observe single shot reversal of the ferromagnet. In addition, we show that neither AO-HIS of the GdFeCo layer is actually required nor direct light illumination of the ferromagnetic multilayer. It is then possible to reverse the magnetization of ferromagnets using only ultrashort heat and spin currents which are generated by the partial ultrafast demagnetization of GdFeCo and transported via a thick metallic copper spacer. These experimental results were successfully understood using semiclassical transport equations for electrons, phonons and quantum spins based on exchange of angular momentum between localized and itinerant spins.Finally, we were able to measure the dynamics of the ferromagnetic multilayer magnetization reversal which is shown to happen in less than a picosecond, being the fastest magnetization reversal ever observed. The action of the external spin current is shown to have an ultrafast cooling effect on the spin which is visible at the sub-picosecond timescale and which can enhance the transient magnetization by up to thirty percent. These results are also understood using our model of heat and angular momentum transport
Jeandet, Antoine. "Spatio-temporal characterization of femtosecond laser pulses using self-referenced Fourier transform spectroscopy Spatio-temporal structure of a petawatt femtosecond laser beam Controlling the velocity of a femtosecond laser pulse using refractive lenses". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS089.
Pełny tekst źródłaCurrent ultrashort laser technology makes it possible to generate pulses lasting a few tens of femtoseconds, with energies of up to tens of joules. Strongly focusing such pulses produces ultra-intense fields that are notably used to generate relativistic particle beams. Proper operation of ultra-intense laser facilities requires to control the temporal and spatial properties of ultrashort pulses. Until now, measurement devices used for this purpose have neglected an important aspect of ultrashort pulses structure, which is linked to spatio-temporal couplings. Spatio-temporal couplings are a particular kind of defects in ultrashort pulses, of which the influence on ultra-intense experiments has been largely overlooked until recently. The rare instruments capable of measuring spatio-temporal couplings are hardly scalable to high-energy laser beams. This thesis is dedicated to TERMITES, a device for the full characterization of ultrashort laser beam, which is used to provide their three dimensional shape in space and time. TERMITES is a self-referenced technique based on spatially-resolved Fourier-Transform Spectroscopy. The first part of this work presents the detailed study of TERMITES, as well as the optimization of its design. Multiple laser systems are then characterized using the instrument. The obtained results are used to establish the first experimental review of spatio-temporal couplings origins in ultrashort lasers
Le, Dortz Jérémy. "Mise en phase active de fibres laser en régime femtoseconde par méthode interférométrique". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX071/document.
Pełny tekst źródłaFemtosecond fiber sources are used in a large number of applications (industrial, medical, fundamental physics) with a growing need in high energy pulses at high repetion rate. Although Ti: Saphirre technology provides energies up to PetaWatt, its repetion rate is low (up to 1 Hz). An alternative is to use an amplified fiber. However, the extractable energy of a single fiber is intrinsically limited.A solution is then to combine several fibers (up to 10 000 fibers for particle acceleration). Coherent beam combining of fibers with an interferometric method (with a record of 64 fibers combined in the cw regime) has proven to be an excellent candidate to combine a large number of fibers.The XCAN project, a collaboration between l'Ecole polytechnique and Thales, aims to realize a demonstrator of 61 fibers coherently combined in the femtosecond regime.The works presented in this thesis are part of this project.In order to study the hard points inherent to the femtosecond regime and to free from the amplification issues, the interferometric method has been implemented on a passive demonstrator, meaning without amplification, of 19 fibers. Once the interferometric method validated, it has been succesfully tested on the amplified XCAN demonstrator.We present also the works done to increase a key parameter of beam combining systems : the combining efficiency. To do this, we have realized a beam shaping of the fiber array output beams. This beam shaping, gaussian to super-gaussian, is done with two arrays of phase plates. The aspherical profiles calculation is described. In order to validate our simulations we have tested the phase plates on the passive demonstrator by getting an increase of 14 %.The works presented in this manuscript are the first steps towards a new massively parallel laser architecture, able to provide both high peak power and high average power
Jacqmin, Hermance. "Coherent combining of few-cycle pulses for the next generation of Terawatt-class laser sources devoted to attosecond physics". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX064/document.
Pełny tekst źródłaThe framework of this thesis is the design and development of a TW-class, high-repetition rate, CEP-stabilized, few-cycle laser system devoted to attosecond physics. Few-cycle pulses includes only a few oscillations of the carrier wave (duration about 5 fs for 800nm central wavelength) and are not directly available at the output of typical femtosecond sources. One of the most popular techniques used for producing such pulses with high spatial quality is nonlinear spectral broadening in a gas-filled hollow-core fiber followed by temporal compression with chirped mirrors. However, as the input pulse energy approaches the milliJoule level, both the transmission and stability of hollow fiber compressors rapidly drop with the onset of self-focusing and ionization. A way of overcoming this limitation is to divide the input pulse into several lower energy replicas that can be subsequently recombined after independent spectral broadening in the fiber. In this thesis, the passive coherent combining of millijoule energy laser pulses down to few-cycle duration in a gas-filled hollow fiber is demonstrated for the first time. High combining efficiency is achieved by using carefully oriented calcite plates for temporal pulse division and recombination. Carrier-envelope phase (CEP)- stable, 6-fs, 800-nm pulses with more than 0.6 mJ energy were routinely generated in the case of twofold division and recombination. A detailed theoretical and experimental analysis of this temporal multiplexing technique is proposed to explain the conditions required for producing few-cycle pulses with high fidelity. In particular, an interferometric method for measuring the relative spectral phase between two replicas is demonstrated. This gives a measure of the phase mismatch in the combining plate, as well as that induced by eventual cross-phase modulation or ionization during propagation in the fiber. The effects degrading the combining process, as polarization change or nonlinear interactions between pulse replicas are analyzed in details. A method is proposed to overcome these limitations, even in the critical case of fourfold pulse division and combination
Daniault, Louis. "Combinaison cohérente d'amplificateurs à fibre en régime femtoseconde". Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00812629.
Pełny tekst źródłaDouti, Dam-Bé Lardja. "Tenue au flux et physique de l'interaction laser/matière dans les couches minces optiques en régime sub-picoseconde". Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4347/document.
Pełny tekst źródłaLaser fluence resistance of optical surfaces is a major challenge for the development of high power and short duration pulse lasers. Studies on laser matter interactions show that the damage initiation is the result of highly nonlinear excitation process such as photoionization, impact ionization and electronic avalanche. In this PhD thesis we focused on the study of the damage and the response of materials after this initiation and their dependence with laser parameters, this in order to better understand the complex mechanisms of damage, identify laws of relevant scales for applications, and enable new optical design with higher laser resistance and lifetimes. A multi parametric experimental testing setup was developed for studying laser resistance of optical components. To collect new data on thin film materials damage dependences, which have been less studied in the literature, different experimental studies have been conducted on dielectrics, in coating or bulk form. The study of the dependency of damage with laser wavelength reveals different ranges characterized by the electronic processes occurring during the interaction. We have considered also the effect of multiple pulse irradiations, with different wavelengths and on coatings realized by different technologies. All these experimental results have been discussed with the help of a numerical simulation model we have developed and presented in this thesis. We have also proposed an original method based on optical phase difference measurement for damage characterization and study. We finished with some experiments on the time resolved microscopy measurements and investigations of damage processes
Beaurepaire, Benoit. "Développement d’un accélérateur laser-plasma à haut taux de répétition pour des applications à la diffraction ultra-rapide d’électrons". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX013/document.
Pełny tekst źródłaElectronic microscopy and electron diffraction allowed the understanding of the organization of atoms in matter. Using a temporally short source, one can measure atomic displacements or modifications of the electronic distribution in matter. To date, the best temporal resolution for time resolved diffraction experiments is of the order of a hundred femtoseconds (fs). Laser-plasma accelerators are good candidates to reach the femtosecond temporal resolution in electron diffraction experiments. Moreover, these accelerators can operate at a high repetition rate, allowing the accumulation of a large amount of data.In this thesis, a laser-plasma accelerator operating at the kHz repetition rate was developed and built. This source generate electron bunches at 100 keV from 3 mJ and 25 fs laser pulses. The physics of the acceleration has been studied, and the effect of the laser wavefront on the electron transverse distribution has been demonstrated.The first electron diffraction experiments with such a source have been realized. An experiment, which was a proof of concept, showed that the quality of the source permits to record nice diffraction patterns on gold and silicium foils. In a second experiment, the structural dynamics of a silicium sample has been studied with a temporal resolution of the order of a few picoseconds.The electron bunches must be accelerated to relativistic energies, at a few MeV, to reach a sub-10 fs temporal resolution. A numerical study showed that ultra-short electron bunches can be accelerated using 5 fs and 5 mJ laser pulses. A temporal resolution of the order of the femtosecond could be reached using such bunches for electron diffraction experiments. Finally, an experiment of the ionization-induced compression of the laser pulses has been realized. The pulse duration was shorten by a factor of 2, and the homogeneity of the process has been studied experimentally and numerically
Salamé, Rami. "Études sur la filamentation des impulsions laser ultrabrèves dans l’air". Thesis, Lyon 1, 2009. http://www.theses.fr/2009LYO10124/document.
Pełny tekst źródłaUltrashort laser pulses propagate in the air in the form of structures of one hundredmicrons of diameter called “filaments”, which have the properties of self-guiding, propagatingfor hundreds of meters, white light generation, etc. These original properties find severalapplications in the domain of remote sensing of pollutants by non-linear Lidar measurements,lightning control, remote LIBS, etc.During my PhD work we have performed several laboratory experiments and field campaignwithin the context of Teramobile project. In particular we have studied the geometry offilamentation, its robustness in an extended region of turbulent air, the propagation ofultrashort pulses beam in multijoules regime, and atmospheric applications of filamentation.For example, we have characterized the angular distribution of the conical emission in thevisible and ultraviolet spectral bands. In another series of experiments, we have proved thatatmospheric turbulence is not a limiting factor of filaments propagation, which also keep theirspectral properties useful for atmospheric applications. Finally, we have illustrated a methodof laser triggering and guiding of lightning and realized laser induced condensation of waterdroplets in laboratory as well as in a reel atmosphere
Quessab, Yassine. "Mechanism and size effects of helicity-dependent all-optical magnetization switching in ferromagnetic thin films". Electronic Thesis or Diss., Université de Lorraine, 2018. http://www.theses.fr/2018LORR0116.
Pełny tekst źródłaOver the past decade, the demand for an even higher capacity to store data has been gradually increasing. To achieve ultrafast and ultrahigh density magnetic data storage, low-power methods to manipulate the magnetization without applying an external magnetic field has attracted growing attention. The possibility to deterministically reverse the magnetization with only circularly polarized light was evidenced in multiple ferri- and ferro-magnetic materials. This phenomenon was called helicity-dependent all-optical switching (HD-AOS). In ferromagnets, it was demonstrated that HD-AOS was a cumulative and multishot process with a helicity-independent demagnetization followed by a helicity-dependent magnetization recovery. Yet, the microscopic mechanism of this helicity-dependent remagnetization remained highly debated. In this thesis, we investigated the magnetization reversal mechanism of all-optical switching in ferromagnetic materials. To explore a potential switching process through domain nucleation and domain wall (DW) propagation, we studied the response of a DW upon femto- or pico-second laser irradiation in Co/Pt thin films that exhibit HD-AOS. We reported helicity-dependent all-optical domain wall motion. We demonstrated that it results from the balance of three contributions: the temperature gradient due to the laser heating, the helicity effect and the pinning effects. By measuring the magnetic circular dichroism, a purely thermal mechanism of the laser-induced DW motion appears to be excluded. Furthermore, we examined the size effects in AOS in Co/Pt films patterned into microdots with a diameter between 10 and 3 μm. This allowed us to explore the role of the dipolar field in the switching mechanism. We discovered that a larger number of laser pulses was required to reverse the magnetization of a microdot compared to the continuous film. This indicated that the dipolar field actually eases the magnetization reversal in the full film. Thus, AOS is less energy-efficient in patterned films, hence making Pt/Co/Pt multilayers not an ideal candidate for integrating AOS in spintronic devices
Mangote, Benoit. "Tenue au flux des couches minces optiques en régime subpicoseconde". Phd thesis, Université Paul Cézanne - Aix-Marseille III, 2011. http://tel.archives-ouvertes.fr/tel-00664545.
Pełny tekst źródłaAmiard, Hudebine Gabriel. "Développement de sources lasers nanosecondes, picosecondes et femtosecondes et applications". Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0024/document.
Pełny tekst źródłaThis two-part thesis focuses on the development of nano and picosecond laser sources and their applications. The first part presents the study, and the realization of a nanosecond laser amplifier chain for the ignition of turboshaft engines. After the repport of the performances and the evolution of this amplifier chain will be presented the results of the tests carried out on a combustion chamber on a test bench at ONERA under low temperatures and low pressures conditions. The second part of this thesis deals with the development of an optical parametric oscillator (OPO) in order to tune in the infrared the wavelength of a pulsed picosecond or femtosecond laser at high cadency and high average power. After presenting the OPO cavity and its performance, we will detail the ability of this OPO to generate compressed femtosecond pulses from pump chirped pulses
Gweha, Nyoma Danny Petty. "Size effects on all-optical helicity-independent switching in magnetic materials". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0035.
Pełny tekst źródłaIn the last fifteen years single pulse all-optical switching has mainly been observed and studied in Transition Metal- Gd based thin film with high potential for enabling new application for energy efficient and fast magnetic data storage, memory, and logic. To move closer to nano or micro technologies, other materials with no or less rare-earth need to be engineered and lateral sample size must be reduced. In this work, we experimentally demonstrate single pulse toggle switching of the magnetization of GdFeCo disks with perpendicular to film plane anisotropy which diameter ranges from 3 µm to 400 nm using 35 fs linearly polarized laser pulses. Two different magnetic states are observed depending on the laser fluence: either deterministic switching of the disks magnetization or randomly oriented disk. We report that the fluence required to observe both magnetic states show a non-monotonic behavior with disk diameter, and that the smallest disks require the lowest minimum fluence for achieving single pulse all-optical helicity-independent switching. Different evolution of the fluence thresholds for both phenomenon as a function of the disk size is observed and discussed. Then, we demonstrate that starting with a Co/Pt bilayer showing strong perpendicular anisotropy, Gd dusting at the interface is sufficient to induce well define single pulse all optical switching. A careful analysis of the impact of the Gd/Co interface and the CoGd alloy composition on all optical switching is presented. The demonstration that very little amount of Gd is needed to induce the magnetization reversal of a ferromagnetic layer not only open new possibility for application, but it also questions theoretical description of the toggle switching mechanism. Finally, we present a systematic study of the magnetization reversal for Gd-dusted Pt/Co/Pt ferromagnet disks which diameter ranges from 1.5 µm to 400 nm with 35 fs linear polarization laser pulses. By varying the number of pulses, it appears that a single toggle switching probability can describe the behavior. The variation of this switching probability is precisely measured in a range from 90% to 99.99%. The switching probability degrades as the diameter of the disks is reduced. The "exponential" variation of the switching probability with the disk diameter size cannot be explained by specific thermal effects. On the other hand, a highly non uniform switching process with a weak microscopic switching probability explains our experimental data. A simple probabilistic model, analog to Condorcet's jury theorem is proposed and compared to micromagnetic simulations
Vieillard, Thomas. "Dynamique induite par champ laser femtoseconde intense : alignement moléculaire en milieu gazeux dense et effet Kerr". Phd thesis, Université de Bourgogne, 2011. http://tel.archives-ouvertes.fr/tel-00697019.
Pełny tekst źródłaMeyer, Rémi. "Contrôle du dépôt d'énergie par laser femtoseconde dans les diélectriques par faisceaux de Bessel : profil spatio-temporel de densité plasma et applications au clivage du verre". Thesis, Bourgogne Franche-Comté, 2020. http://indexation.univ-fcomte.fr/nuxeo/site/esupversions/9cca4761-0970-4b3d-a6e9-01b766feff4d.
Pełny tekst źródłaThe use of ultrashort pulses for laser ablation allows for a precise energy deposition thanks to a highly confined laser-matter interaction. The non-linear effects causing this confinement are also usually responsible of beam profile distorsions along propagation and intensity instabilities. High cone angle Bessel beams have shown to be excellent candidates for dielectrics processing since they are robust to non-linear effects. In femtosecond regime, they are able to generate in single shot high aspect ratio nanochannels in transparent media. However the ablation dynamics and the coupling with the laser-induced plasma remain partially unclear in this case. The current model describing such interaction is uncompatible with experimental observations. This thesis investigates the laser-plasma interaction and follows two axes of work. First part is focused on the laser-plasma interaction characterization in transparent media and in the case of femtosecond Bessel beam, by developping and exploiting an interferometric pump-probe experiment. We measure the plasma dynamics through the plasma-related complex refraction index modifications, which we resolve in space and time. Preliminary results show a confined plasma (radius < 1 µm) in the transverse direction and whose density approaches the critical density for a pulse energy approaching the nanochannel formation threshold. In a second part, we investigate the effect of aligned nanochannels on the fracture ability of glass samples and its application to glass cleaving. Here we solve two limiting problems to high quality cleaving by spatial beam shape engineering: we demonstrate a signification improvement of 150 µm-thin glass cleaving by the use of elliptical-core Bessel beams; and we establish a proof of principle of 10 mm-thick glass single-pass cleaving thanks to a 3 axicons-based setup
Awada, Chawki. "Nature cohérente et incohérente de la réponse de Second Harmonique dans les nanostructures métalliques d’or et d’argent". Thesis, Lyon 1, 2009. http://www.theses.fr/2009LYO10071/document.
Pełny tekst źródłaIn this work, the non linear optical properties of different silver and gold metallic nanostructures are studied. In particular, a special attention is concerning the coherent or incoherent nature of the response. For that purpose, the Second Harmonic Generation (SHG) technique is used. It is indeed one of the simplest non linear optical methods to underline the coherent or incoherent nature of the response. Samples used for this reason are constituted on the first hand by dielectric films doped by bimetallic nanoparticles of clusters of the type AuAg of various gold molar fractions for the incoherent responses and on the other hand by arrays of gold nanocylinders of various sizes arranged according to three geometrical configurations (square, hexagonal and random) on a substrate for the coherent response. The major part of the work is devoted to the study of the propagation and the second harmonic frequency in regime of Gaussian beams and short pulses in dielectric films doped by bimetallic nanoparticles because of supplementary phenomena observed simultaneously in the conversion of frequency: non linear absorption and refraction, Gouy phase... By the method of the fringes of Maker, the absolute values of the coefficient of the second order non linear susceptibility of these films are measured then the absolute values of the quadratic hyperpolarizability of nanoparticles are estimated on the basis of a model of incoherent responses. Finally, a preliminary study on the light continuum generation is presented. The coherent nature of the SHG response is studied in the nanocylinders arrays. We show that the origin of the response is associated with the existence of the surface defects in these nanostructures and thus have an incoherent character. However, we were able to put in evidence the effects associated with the size of nanocylinders and with the organization of nanocylinders on the substrate, this last effect being attached to a coherent character of the response
Hairaye, Camille. "Fonctionnalisation de surfaces par microstructuration laser". Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAD013/document.
Pełny tekst źródłaThis PhD thesis is about surface functionalization by laser microstructuring. The experimental study consists in texturing stainless steel surfaces with a pulsed Yb fibre laser source (1030 nm, 300 fs), in order to control their wettability and confer to them superhydrophobic properties. With an optimization of the irradiating conditions on the target, it is possible to confer to the surface a dual-scale roughness. By successive ablations according to a pattern of crossed lines, microstructures in the range of tens of micrometres are realized, on which self-organized nanostructures are superimposed. Simulation of the energy coupling in the material allows to determine the process parameters to be used, in order to limit the thermal accumulation and avoid the melting of the surface. This study reveals the role of the laser texturing in the apparition of the superhydrophobic character and emphasizes the influence of the physicochemical properties of the material
Korti, Mokhtar. "Contribution à la caractérisation des impulsions ultra-courtes à l’aide de sources laser rapidement accordables". Electronic Thesis or Diss., Evry, Institut national des télécommunications, 2018. http://www.theses.fr/2018TELE0014.
Pełny tekst źródłaOptical swept sources are distinguished by the ability to change their output wavelength in a continuous manner over time. They are used in many applications such as telecommunications, spectroscopy and optical coherence tomography. They are mainly characterized by a narrow instantaneous linewidth, a high sweep rate and a wide tuning range. The advantages of swept sources open the way to other types of applications such as the characterization of ultrashort pulses for example. Generally, these pulses are characterized using nonlinear methods which are slow and too complicated. We have proposed a novel approach based on swept sources for the characterization of ultrashort pulses. By using a linearly wavelength-swept semiconductor laser like SG-DBR (Sampled-Grating Distributed Bragg Reflector), we can scan the entire optical spectrum of the pulses under test in a single measurement. The beat signal between the swept source and the pulsed laser is then used to measure the spectral amplitude and phase of all modes which gives access to the temporal shape of the pulse. The main advantage of our approach is that the entire characterization process is done in a single fast measurement. Indeed, the high sweep rate of the swept source offers the possibility of having real time measurements. In addition, thanks to the wide tuning range, this technique is completely independent of the pulse under test, it requires no prior knowledge of the various properties of the pulse such as the repetition frequency, the number of modes or the frequency of each mode
Sarmani, Abdul Rahman. "Yb-doped femtosecond lasers and their frequency doubling". Thesis, St Andrews, 2008. http://hdl.handle.net/10023/781.
Pełny tekst źródłaWu, Songping. "Femtosecond laser micro-structuring of silicon wafer in water confinement". Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Wu_09007dcc80493fda.pdf.
Pełny tekst źródłaVita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 3, 2008) Includes bibliographical references (p. 66-74).
Darby, Mark Stuart Bennett. "Femtosecond pulsed laser deposition". Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/65796/.
Pełny tekst źródłaKafka, Kyle R. P. "Laser-Induced Damage with Femtosecond Pulses". The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1483661596059632.
Pełny tekst źródłaChin, Roger S. "Femtosecond laser pulse compression". Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/29799.
Pełny tekst źródłaScience, Faculty of
Physics and Astronomy, Department of
Graduate
Dooley, Patrick W. Corkum Paul B. "Molecular imaging using femtosecond laser pulses". *McMaster only, 2003.
Znajdź pełny tekst źródłaXu, Bingwei. "Control of multiphoton molecular excitation with shaped femtosecond laser pulses". Diss., Connect to online resource - MSU authorized users, 2008.
Znajdź pełny tekst źródłaGabolde, Pablo. "Measurements of the spatio-temporal profiles of femtosecond laser pulses". Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-06272007-101312/.
Pełny tekst źródłaTrebino, Rick, Committee Chair ; Kennedy, Brian, Committee Member ; Kuzmich, Alex, Committee Member ; Curtis, Jennifer, Committee Member ; Buck, John, Committee Member.
Okoye, Raphael. "Manipulation of short pulses". Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/85576.
Pełny tekst źródłaENGLISH ABSTRACT: An ultra-fast laser pulse can be described in the time or frequency domain. If the timebandwidth product of an ultra-fast pulse is not satisfied, then the pulse is stretched. Stretching can be described in the time or frequency domain. In the time domain, it is called a chirp and in the frequency domain, it is known as the group delay dispersion GDD. Various techniques can be used to stretch and compress laser pulses. In this project, a prism pulse compressor used for compressing stretched pulses was built. A 200nm supercontinnum generated in an all normal dispersion photonic crystal fibre (ANDi-PCF) was compressed using the prism pulse compressor from 2ps to 140fs. The experiment and physical interpretation presented in this project suggest that a shorter pulse duration less than the measured 140fs of the compressed supercontinnum can be obtained.
AFRIKAANSE OPSOMMING: 'n Ultra-vinnige laser puls kan beskryf word in tyd of frekwensie. As die tyd-bandwydte produk van ‘n ultra-vinnige puls nie bevredig is nie, dan is die puls uitgerek. Hierdie uitrekking kan beskryf word in tyd of frekwensie. In tyd word dit tjirp genoem en in frekwensie groep vertraging dispersie. Verskeie tegnieke kan gebruik word om ‘n laser puls te rek of saam te pers. In hierdie projek is ‘n prisma puls kompressor gebou om uitgerekte pulse saam te pers. ‘n 200nm bre e bandwydte puls (“supercontinuum”) is gegenereer in ‘n fotoniese kristal optiese vesel wat uitsluitlik normale dispersie toon (ANDI-PCF) en die puls is toe saamgepers met behulp van die prisma puls kompressor van‘n oorspronklike 2ps na 140fs. Die eksperiment en fisiese interpretasie wat in hierdie projek aangebied word dui daarop dat ‘n nog korter puls, minder as die gemete 140 fs, verkry kan word deur die bre e bandwydte puls verder saam te pers.
McWilliam, Alan. "Femtosecond Cr⁴⁺:forsterite laser for applications in telecommunications and biophotonics /". Thesis, St Andrews, 2007. http://hdl.handle.net/10023/261.
Pełny tekst źródłaBowlan, Pamela. "Measuring the spatiotemporal electric". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28188.
Pełny tekst źródłaCommittee Chair: Rick Trebino; Committee Member: Jennifer Curtis; Committee Member: John Buck; Committee Member: Mike Chapman; Committee Member: Stephen Ralph.
Ferreira, Paulo Henrique Dias. "Produção de nanopartículas de Au induzida por pulsos laser de femtossegundos formatados". Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-19012012-083752/.
Pełny tekst źródłaIn this work we have studied the synthesis of Au nanoparticles using shaped ultrashort pulses (800 nm, 30 fs, 1 kHz and 2 mJ), induced by the ionization of the chitosan. Initially we developed a pulse shaping setup that uses a spatial light modulator (liquid crystals array), with which we are able to impose distinct phase mask to the laser pulse. In order to monitor the nanoparticles production process, we used a pump-probe system, consisting of femtosecond pulses (pump) and white light (probe), which allows the observation of the plasmon band enhancement and hence the nanoparticles formation dynamics. The results obtained by Fourier Transform limited pulses have shown that the nanoparticles formation is due to the nonlinear ionization of chitosan, which is related to hydroxyl group oxidation to the carbonyl group. Transmission electron microscopy measurements provided the sizes (20-100 nm) and shapes (spheres, pyramids, hexagons, rods, etc.) of the produced nanoparticles. Moreover, our results revealed that ionization is initiated by multiphoton absorption, more specifically by four photons absorption. Using pulses shaped with constant, step and cossenoidal (with different frequencies) spectral phase masks, we investigated their influence in the nanoparticles formation. We conclude that longer pulses are more favorable to the ionization process and, consequently, to the gold ions reduction for the synthesis of the metallic nanoparticles. This behavior is probably due to the redistribution of the absorbed energy to the vibrational modes, which is more likely for longer pulses. Therefore, the approach presented here can open new ways to produce metallic nanoparticles, which can be further explored from applied and fundamental points of view.
Heath, Daniel. "Digital micromirror devices and femtosecond laser pulses for rapid laser micromachining". Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/417275/.
Pełny tekst źródłaHenderson, Gordon George. "Femtosecond laser studies of fullerenes and nanotubes". Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7737.
Pełny tekst źródłaAustin, Drake Ross. "Semiconductor Surface Modification using Mid-Infrared, Femtosecond Laser Pulses". The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu150324882632046.
Pełny tekst źródłaHolzwarth, Ronald. "Measuring the frequency of light using femtosecond laser pulses". [S.l.] : [s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=96303006X.
Pełny tekst źródłaBorowiec, Andrzej Haugen Harold Kristen. "Ablation and micromachining of INP with femtosecond laser pulses /". *McMaster only, 2004.
Znajdź pełny tekst źródłaHolzwarth, Ronald. "Measuring the Frequency of Light using Femtosecond Laser Pulses". Diss., lmu, 2001. http://nbn-resolving.de/urn:nbn:de:bvb:19-3214.
Pełny tekst źródłaAlshehri, Ali. "Micro and Nanostructuring of Polymers by Femtosecond Laser Pulses". Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35356.
Pełny tekst źródłaBadger, Antony Daniel. "Transport in dense plasmas produced by femtosecond laser pulses". Thesis, University of Essex, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361032.
Pełny tekst źródłaCenturion, Martin Psaltis Demetri. "Study of the nonlinear propagation of femtosecond laser pulses /". Diss., Pasadena, Calif. : California Institute of Technology, 2005. http://resolver.caltech.edu/CaltechETD:etd-05262005-174627.
Pełny tekst źródłaBock, Katherine J. "Femtosecond Fiber Lasers". Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23391.
Pełny tekst źródłaJu, Heongkyu. "Photon-number squeezing of femtosecond optical pulses in nonlinear media". Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249632.
Pełny tekst źródłaMacpherson, James. "Characterisation and Optimization of Ultrashort Laser Pulses". Thesis, University of Waterloo, 2003. http://hdl.handle.net/10012/1237.
Pełny tekst źródłaMori, Andrew. "Time domain pulse shaping using a genetic algorithm". Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4321.
Pełny tekst źródłaENGLISH ABSTRACT: Through the use of complex Laser Pulse Shaping, numerous fundamental laser induced processes may be controlled as well as studied. This work serves as an introduction into Laser Pulse Shaping, with the focus on a simple Pulse Shaping experiment, as well as to determine whether future, more complex processes may be similarly controlled. A description of Laser Pulse Shaping theory is presented here, along with a full explanation of a simple experiment to maximize second harmonic generation (SHG) through Pulse Shaping. This experiment is simple on a theoretical level yet complicated in both implementation as well as operation. The experimental setup and software integration required hardware compatibility in multiple programming languages. This work was successful in the sense that a fully automated dispersion compensation system, accomplished through the use of a genetic algorithm in a feedback controlled loop, was constructed and tested. The success of this experiment and the understanding gained in this work has laid the foundation for further complex Pulse Shaping systems to be achieved in future.
AFRIKAANSE OPSOMMING: Komplekse Laserpuls-vervorming kan gebruik word om verskeie fundamentele laser-geinduseerde prosesse beide te beheer asook te bestudeer. Hierdie navorsingstuk dien as n inleiding tot Laserpuls-vervorming, spesifiek gefokus op n eenvoudige Pulsvervormings-eksperiment. Meer komplekse Pulsvervormingsopstellings kan toegepas word deur die kennis opgedoen in hierdie tesis. Die teoretiese agtergrond van Laserpuls-vervormings word bespreek, tesame met n eenvoudige eksperiment om die Tweede Harmoniek Skeppingsproses (SHG) te maksimeer deur van Laserpuls-vervorming gebruik te maak. Die eksperiment is teoreties eenvoudig, waar die implimentering asook bedryf meer kompleks is. Die bedryf van die eksperiment word in 2 dele hanteer: die hoofprogram en n Genetiese Algoritme gebruik in optimering. Die werking van Genetiese Algoritmes asook Ultrakort Pulse (USPs) en pulskarakterisering word ook bespreek. Die suksesvolle opstelling van die experiment en ook die eind resultate wat gevind is, maak dit moontlik om meer ingewikkeld komplekse laserpulsvervorming experimente te bestudeer.
Suresh, M. "Neutral and ionic atoms and molecules in femtosecond laser pulses". Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421008.
Pełny tekst źródłaHort, Ondřej. "High harmonic generation with high energy femtosecond pulses". Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0097/document.
Pełny tekst źródłaWe present our work on high harmonic generation with TW femtosecond pulses. We performed HHG with high energy femtosecond pulses and characterize the generated XUV emission spatially and spectrally at the single-shot basis and we observed many structures in spatially resolved XUV spectra in the far field. Those structures are very robust and reproducible and have been observed in many different gases and generation geometries. Without spatial and spectral characterization on the single-shot basis the structures are not visible. We developed simple simulations to identify those structures and we observed similar structures as experimentally. We identified them as a result of spatial coherence of the XUV source and the diffraction to the far field. In the near field, the harmonic amplitude and phase are spatially and temporally dependent and their profiles are strongly modulated. Such modulated profiles diffract to structured spatially resolved spectra in the far field. We observed that propagation of the XUV in the generating medium has little influence on the structures. We demonstrate spatial shaping of the driving pulses via adaptive optics and their advantage for HHG. An adaptive optics allows us to have the driving beam of regular spatial profile and phase even out of focus. Such a beam is used for HHG with a large diameter driving beam and control of the XUV beam is demonstrated. We developed a high energy TW post-compression technique and we obtained pulses of 10 fs and 10 mJ in a quasi-Gaussian spatial profile. The technique is based on ionization-inducedself-phase-modulation and is compatible with high energy TW level pulses. We performed HHG with such TW pulses and obtained XUV quasi-continuum spectra with spectral and spatial structures. We performed simple simulations and SFAsimulations and we observed similar structures even without considering the XUV propagation in the medium
Mirim, Denilson de Camargo. "Desenvolvimento de processos de microusinagem com laser de pulsos ultracurtos". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-29082016-111728/.
Pełny tekst źródłaThe development of laser systems with ultrashort pulses brought the possibility of machining very small structures in virtually any type of material. In this work was continued the studies already started in Lasers and Applications Center (CLA), with dielectric materials, introducing temporal width of the laser pulses as another variable, and using the knowledge acquired to determine ablation threshold and incubation parameters of some metals such as AISI 1045 steel, VI 138 stainless steel, electrolytic copper and molybdenum. The absence of heat in the ablation process of metals is much more difficult since the creation of a layer of ions is greatly impaired by electronic mobility in its vicinity. Hence, the ablation process for metals with ultrashort pulses, has, as main mechanism, the phase explosion associated with other processes that also contribute in the process, but on a smaller scale, such as Coulomb explosion and ultrafast fusion. Moreover, properties such as electron-phonon coupling constant and thermal conductivity play an important role and should be taken into account in investigating the process of ablation of metals. This study made it possible to obtain operation parameter where the heat transferred to the lattice is minimized, enabling precision micromachining and controlled changes in the morphology of the surface of metals. The results provided conditions for new developments and real machining applications with ultrashort pulses.
Paye, Malini. "Femtosecond pulse generation in solid-state lasers". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/38019.
Pełny tekst źródłaIncludes bibliographical references (leaves 181-193).
by Malini Paye.
Ph.D.
Wright, Peter. "Generation, Characterization and Application of the 3rd and 4th Harmonics of a Ti:sapphire Femtosecond Laser". Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20628.
Pełny tekst źródłaRahimiangolkhandani, Mitra. "Interaction of Structured Femtosecond Light Pulses with Matter". Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42334.
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