Letteratura scientifica selezionata sul tema "Pulses laser femtoseconde"
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Articoli di riviste sul tema "Pulses laser femtoseconde":
1
Renard, William, Clément Chan, Antoine Dubrouil, Jérôme Lhermite, Giorgio Santarelli e Romain Royon. "Agile femtosecond synchronizable laser source from a gated CW laser". Laser Physics Letters 19, n. 7 (31 maggio 2022): 075105. http://dx.doi.org/10.1088/1612-202x/ac7133.
Abstract (sommario):
Abstract In this letter we demonstrate agile femtosecond pulse generation with a widely tunable repetition rate (10–100 MHz) from a continuous wave laser diode optically gated by a Mach–Zehnder electro-optic intensity modulator. Initial sub-50 ps pulses are strongly spectral broadened (>5 nm) by self-phase modulation in a polarization maintaining single-mode fiber. A tunable optical pulse train with pulse durations of a few hundred femtoseconds is obtained using a simple fixed grating compressor, thanks to spectral broadening saturation phenomena. The source is easily synchronized with low timing jitter using an external clock signal.
2
Li, Zerui. "Analysis of the Principles and Applications of Ultra-intensity and Ultrashort Laser". Highlights in Science, Engineering and Technology 76 (31 dicembre 2023): 441–49. http://dx.doi.org/10.54097/9s9fm882.
Abstract (sommario):
With the development of laser technology, how to improve the output performance and peak power of lasers has become one of the hot directions of current research. This study analyzes the principles and applications of ultra-intensity and ultrashort pulse laser. It firstly outlines the development history of laser technology and the basic definition of ultra-intensity and ultrashort pulse laser. It also mentions the realization methods for generating ultra-intensity and ultrashort pulse lasers, such as mode-locked femtosecond oscillators and CPA-based femtosecond amplifiers. The paper describes the principles of CPA technique and emphasizes its importance in realizing high power ultrashort pulses. The paper discusses various applications of ultra-intensity and ultrashort pulsed laser and summarizes and discusses the major bottlenecks facing current and future ultra-intensity and ultrashort pulsed lasers and their possible solutions. The technical review in this paper aims to enhance the understanding of ultra-intensity and ultrashort pulsed laser and provide insights into the next phase of research exploration in ultra-intensity and ultrashort pulsed lasers.
3
Tikhomirov, S. A. "Femtosecond System with Pulse Pumping of Seed Laser and Amplifier by Using a Single Power Unit". Devices and Methods of Measurements 12, n. 1 (19 marzo 2021): 23–29. http://dx.doi.org/10.21122/2220-9506-2021-12-1-23-29.
Abstract (sommario):
For several decades development of methods for generating ultrashort pulses has been an independent urgent scientific and technical problem. There is a constant improvement both in the methods of such pulses receiving and in methods of their use. The aim of this work was to investigate the possibility of realizing the coordinated operation of two fundamentally different types of pump lasers for the femtosecond oscillator and amplifier based on one single-lamp laser head and to create on this basis a compact high-power femtosecond system with pulsed pumping and one power unit.The practical implementation of two types of pulsed lasers (nano- and picosecond ones operating, respectively, in Q-switch and modelock regime) on a single laser head with two active elements and one pump lamp is carried out. The required synchronization in time the pump pulse femtosecond amplifier formation and quasi-stationary region of generated pulses in the output radiation of a femtosecond Ti:sapphire is obtained.On this basis a compact, pulse pumped monoblock laser system has been developed that can generate femtosecond pulses with a duration of 50–150 fs with an energy up to 1 mJ and a high enough pulse repetition rate (up to 1 kHz which is determined by the type of laser head and pump unit used). In the developed laser system a compact scheme of a stretcher-compressor with a single common diffraction grating is used.Laser systems of this type characterized by a relatively low cost due to the use of a single power supply unit for simultaneous pumping of the amplifier and oscillator, as well as lower requirements for the quality of optical elements and usage conditions due to the pulse mode of operation, are quite practical and can be used both in scientific research in the field of ultra-high-speed kinetic spectroscopy and nonlinear optics, as well as in numerous technical applications, particular in the precision processing of materials, as optical simulators of the action of heavy charged particles in testing the radiation resistance of integrated circuits and electronic modules.
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Dabu. "Femtosecond Laser Pulses Amplification in Crystals". Crystals 9, n. 7 (5 luglio 2019): 347. http://dx.doi.org/10.3390/cryst9070347.
Abstract (sommario):
This paper describes techniques for high-energy laser pulse amplification in multi-PW femtosecond laser pulses. Femtosecond laser pulses can be generated and amplified in laser media with a broad emission spectral bandwidth, like Ti:sapphire crystals. By chirped pulse amplification (CPA) techniques, hundred-Joule amplified laser pulses can be obtained. Multi-PW peak-power femtosecond pulses are generated after recompression of amplified chirped laser pulses. The characteristics and problems of large bandwidth laser pulses amplification in Ti:sapphire crystals are discussed. An alternative technique, based on optical parametric chirped pulse amplification (OPCPA) in nonlinear crystals, is presented. Phase-matching conditions for broad bandwidth parametric amplification in nonlinear crystals are inferred. Ultra-broad phase matching bandwidth of more than 100 nm, able to support the amplification of sub-10 fs laser pulses, are demonstrated in nonlinear crystals, such as Beta Barium Borate (BBO), Potassium Dideuterium Phosphate (DKDP), and Lithium Triborate (LBO). The advantages and drawbacks of CPA amplification in laser crystals and OPCPA in nonlinear crystals are discussed. A hybrid amplification method, which combines low-medium energy OPCPA in nonlinear crystals with high energy CPA in large aperture laser crystals, is described. This technique is currently used for the development of 10-PW laser systems, with sub-20 fs pulse duration and more than 1012 intensity contrast of output femtosecond pulses.
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Zeng, Li, Xiaofan Wang, Yifan Liang, Huaiqian Yi, Weiqing Zhang e Xueming Yang. "Chirped-Pulse Amplification in an Echo-Enabled Harmonic-Generation Free-Electron Laser". Applied Sciences 13, n. 18 (14 settembre 2023): 10292. http://dx.doi.org/10.3390/app131810292.
Abstract (sommario):
The field of ultrafast science has experienced significant growth over the last decade, largely attributed to advancements in optical and laser technologies such as chirped-pulse amplification and high-harmonic generation. The distinctive characteristics of intense ultrafast free-electron lasers (FELs) have introduced novel prospects for investigating molecular dynamics, as well as providing an opportunity to gain deeper insights into nonlinear processes in materials. Therefore, high-power ultrafast FELs can be widely used for both fundamental research and practical applications. This study presents a novel approach for producing high-power femtosecond FEL pulses, utilizing chirped-pulse amplification in echo-enabled harmonic generation. Chirped seed pulses are employed to induce frequency-chirped energy modulation in the electron beam. The generated FEL pulse, which inherits the chirped frequency, can be compressed through the gratings in the off-plane mount geometry to provide ultraintense ultrafast pulses. The numerical modeling results indicate that peak power exceeding 20 GW and a pulse duration in the order of several femtoseconds can be achieved.
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Ye, Hanyu, Florian Leroy, Lilia Pontagnier, Giorgio Santarelli, Johan Boullet e Eric Cormier. "Non-linear amplification to 200 W of an electro-optic frequency comb with GHz tunable repetition rates". EPJ Web of Conferences 287 (2023): 07025. http://dx.doi.org/10.1051/epjconf/202328707025.
Abstract (sommario):
We present a monolithic Yb-doped fiber laser system delivering 200 W average power of femtosecond pulses at tunable GHz repetition rates. The system is based on a GHz electro-optic (EO) frequency comb operating in the nonlinear regime. The EO comb pulses at 1 µm wavelength are initially pre-compressed to sub-2 ps, amplified to 2.5 W, and finally boosted to 200 W in a newly designed large-mode-area, Yb-doped photonic crystal fiber. Continuously tunable across 1-18 GHz, the picosecond pulses experience nonlinear propagation in the booster amplifier, leading to output pulses compressible down to several hundreds of femtoseconds. To push our system deeper into the nonlinear amplification regime, the pulse repetition rate is further reduced to 2 GHz, enabling significant spectral broadening at 200 W. Characterization reveals sub-200 fs duration after compression. The present EO-comb seeded nonlinear amplification system opens a new route to the development of high-power, tunable GHz-repetition-rate, femtosecond fiber lasers.
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Obata, Kotaro, Francesc Caballero-Lucas, Shota Kawabata, Godai Miyaji e Koji Sugioka. "GHz bursts in MHz burst (BiBurst) enabling high-speed femtosecond laser ablation of silicon due to prevention of air ionization". International Journal of Extreme Manufacturing 5, n. 2 (11 aprile 2023): 025002. http://dx.doi.org/10.1088/2631-7990/acc0e5.
Abstract (sommario):
Abstract For the practical use of femtosecond laser ablation, inputs of higher laser intensity are preferred to attain high-throughput material removal. However, the use of higher laser intensities for increasing ablation rates can have detrimental effects on ablation quality due to excess heat generation and air ionization. This paper employs ablation using BiBurst femtosecond laser pulses, which consist of multiple bursts (2 and 5 bursts) at a repetition rate of 64 MHz, each containing multiple intra-pulses (2–20 pulses) at an ultrafast repetition rate of 4.88 GHz, to overcome these conflicting conditions. Ablation of silicon substrates using the BiBurst mode with 5 burst pulses and 20 intra-pulses successfully prevents air breakdown at packet energies higher than the pulse energy inducing the air ionization by the conventional femtosecond laser pulse irradiation (single-pulse mode). As a result, ablation speed can be enhanced by a factor of 23 without deteriorating the ablation quality compared to that by the single-pulse mode ablation under the conditions where the air ionization is avoided.
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Li, DongCheng. "Femtosecond pulsed laser technology and applications". Theoretical and Natural Science 28, n. 1 (26 dicembre 2023): 166–73. http://dx.doi.org/10.54254/2753-8818/28/20230347.
Abstract (sommario):
This paper describes femtosecond pulsed laser technology and related applications. The focus is on two core femtosecond pulsed laser technologies: femtosecond pulsed laser generation and amplification. In the generation of femtosecond pulsed lasers, mode-locking techniques, Kerr-lens mode-locking, and semiconductor saturable absorber mirrors are presented; in the amplification of femtosecond pulsed lasers, chirped-pulse amplification and coherent synthesis techniques are presented. This paper analyses the applications of femtosecond pulsed lasers in both the biomedical and manufacturing sectors and gives the development trends as well as the challenges of femtosecond laser technology. Femtosecond lasers are now used in a wide range of applications. Femtosecond pulsed lasers will develop in the directions of high power, miniaturisation, intelligence and precision. Laser tweezers will become the new direction of development in the future.
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Takubo, Kou, Samiran Banu, Sichen Jin, Misaki Kaneko, Wataru Yajima, Makoto Kuwahara, Yasuhiko Hayashi et al. "Generation of sub-100 fs electron pulses for time-resolved electron diffraction using a direct synchronization method". Review of Scientific Instruments 93, n. 5 (1 maggio 2022): 053005. http://dx.doi.org/10.1063/5.0086008.
Abstract (sommario):
To investigate photoinduced phenomena in various materials and molecules, ultrashort pulsed x-ray and electron sources with high brightness and high repetition rates are required. The x-ray and electron’s typical and de Broglie wavelengths are shorter than lattice constants of materials and molecules. Therefore, photoinduced structural dynamics on the femtosecond to picosecond timescales can be directly observed in a diffraction manner by using these pulses. This research created a tabletop ultrashort pulsed electron diffraction setup that used a femtosecond laser and electron pulse compression cavity that was directly synchronized to the microwave master oscillator (∼3 GHz). A compressed electron pulse with a 1 kHz repetition rate contained 228 000 electrons. The electron pulse duration was estimated to be less than 100 fs at the sample position by using photoinduced immediate lattice changes in an ultrathin silicon film (50 nm). The newly developed time-resolved electron diffraction setup has a pulse duration that is comparable to femtosecond laser pulse widths (35–100 fs). The pulse duration, in particular, fits within the timescale of photoinduced phenomena in quantum materials. Our developed ultrafast time-resolved electron diffraction setup with a sub-100 fs temporal resolution would be a powerful tool in material science with a combination of optical pump–probe, time-resolved photoemission spectroscopic, and pulsed x-ray measurements.
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Zhu, Chang Jun, Bing Xue, Xue Jun Zhai e Jun Fang He. "Manufacture of Lasers with Multiple Operating Modes". Advanced Materials Research 482-484 (febbraio 2012): 1937–40. http://dx.doi.org/10.4028/www.scientific.net/amr.482-484.1937.
Abstract (sommario):
A two-beam pumped Ti:sapphire laser with femtosecond and picosecond cavities was manufactured. Three operating modes, independent self mode-locking, cross mode-locking and multi-pulse operating, were achieved. In the independent self mode-locking mode, femtosecond and picosecond laser pulses were generated in the two cavities, respectively. In the cross mode-locking mode, synchronized femtosecond and picosecond laser pulses were obtained in the two cavities. In the multi-pulse mode, multi-pulses were produced in the picosecond cavity. The results show that, the independent self mode-locking mode is dominated mainly by group velocity dispersion and self-phase modulation, the cross mode-locking mode is governed primarily by cross-phase modulation and the multi-pulse operating is ruled largely by self-amplitude modulation.
Tesi sul tema "Pulses laser femtoseconde":
1
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.
Abstract (sommario):
Depuis sa découverte expérimentale en 2004, le graphène a émergé comme un matériau potentiel pour les technologies de nouvelle génération. Le graphène était le premier matériau 2D produit et l’intérêt et qu’il suscite provient de ses remarquables propriétés: il possède d’importants coefficients de mobilité électronique et de conductivité thermique, il est également le matériau le plus solide et léger connu. Pour permettre le développement d’applications à l’ échelle industrielle, des technologies de structuration à l’ échelle submicronique sont nécessaires.Cette thèse se concentre sur l’exploration de l’ablation par laser femtoseconde en tant que technique de structuration rapide et peu coûteuse de structuré graphène obtenu par technique CVD (Chemical Vapor Deposition). L’utilisation d’impulsions laser ultra brèves est a priori intéressante en raison de la capacité des impulsions laser ultra brèves à déposer au sein des matériaux une quantité élevée d’ énergie dans un volume extrêmement confiné.Nous avons réalisé un ensemble d’expériences à partir de faisceaux non-diffractants pour caractériser les paramètres requis pour contrôler l’ablation à l’ échelle sub-micronique. Nous avons déterminé les caractéristiques de l’ablation en régime mono-coup pour le graphène CVD, tels que le seuil d’ablation et la probabilité d’ablation. Pour cela, nous avons développé une nouvelle technique de mesure indépendante du seuil indépendante de la taille de la zone ablatée. Nous avons ainsi pu mettre en évidence un écart par rapport au modèle classique d’ablation, l’effet des différents substrats diélectriques, ainsi que le rôle des joints de grain.Nos résultats montrent que l’ablation mono-coup par impulsion femtoseconde est une technique efficace pour des structures au-delà d’une taille caractéristique de 1 _m, mais en dessous de cette dimension, de nouvelles stratégies d’illuminations se révèlent encore nécessairesSince 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
2
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.
Abstract (sommario):
La modification du silicium dans son volume est possible aujourd’hui avec des lasers infrarouges nanosecondes. Néanmoins, le régime d’intérêt pour la modification contrôlée en volume des matériaux transparents correspond aux impulsions femtosecondes. Cependant, aujourd’hui aucune démonstration de modification permanente du volume du Si n’a été réalisée avec une impulsion ultra-brève (100 fs). Pour infirmer ce résultat, nous avons développé des méthodes de microscopie infrarouge ultra-rapides. Tout d’abord, nous étudions le microplasma confiné dans le volume, caractérisé par la génération de porteurs libres par ionisation nonlinéaire du silicium, suivie de la relaxation totale du matériau. Ces observations, couplées à la reconstruction de la propagation du faisceau dans le matériau, démontrent un dépôt d’énergie d’amplitude fortement limitée par des effets nonlinéaires d’absorption et de propagation. Cette analyse a été confirmée par un modèle numérique simulant la propagation nonlinéaire du faisceau femtoseconde. La compréhension de cette limitation a permis de développer de nouvelles configurations expérimentales grâce auxquelles l’endommagement local et permanent du volume du silicium a pu être initié en régime d’impulsions courtesThe 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
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Remy, Quentin. "Ultrafast spin dynamics and transport in magnetic metallic heterostructures". Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0191.
Abstract (sommario):
Le contrôle de l'aimantation, et donc du spin, aux échelles de temps ultra courtes, est un sujet d'importance fondamentale pour l'élaboration de systèmes qui peuvent stocker de l'information beaucoup plus rapidement. La possibilité d'écrire de l'information avec des pulses laser femtoseconde sur des métaux magnétiques tels que GdFeCo ou MnRuGa en quelques picosecondes fut une étape conséquente pour pouvoir réaliser ce progrès technologique. Cependant, le renversement de l'aimantation observé dans ces matériaux après les avoir irradié avec un unique pulse laser, appelé retournement tout optique indépendant de l'hélicité (AO-HIS pour {All Optical Helicity Independent Switching} en anglais), est toujours limité à une petite catégorie de matériaux ferrimagnétiques et sa description physique n'est toujours pas entièrement comprise. Dans cette thèse, nous étudions l'AO-HIS dans des films minces composés d'une ou deux couches d'alliages de GdFeCo de différentes compositions. Nous montrons que ces couches génèrent des courants de spin qui peuvent modifier l'AO-HIS de ces matériaux. En particulier, nous montrons qu'il est possible d'utiliser ces courants de spin pour renverser l'aimantation des différentes multicouches ferromagnétiques, avec un seul pulse laser femtoseconde, qui ne subiraient qu'une désaimantation et ne se retourneraient donc pas autrement. En changeant la composition de l'alliage de GdFeCo et la température de Curie du matériau ferromagnétique, nous pouvons modifier l'énergie nécessaire pour engendrer le renversement magnétique de la multicouche ferromagnétique avec un pulse de lumière. De plus, nous montrons que l'AO-HIS de l'alliage de GdFeCo n'est en réalité pas nécessaire ainsi que l'illumination directe de la couche ferromagnétique par la lumière laser. Il est donc possible de retourner l'aimantation d'un matériau ferromagnétique en utilisant uniquement des courants ultra courts de chaleur et de spin qui sont créés par la désaimantation ultra rapide partielle de l'alliage de GdFeCo et transportés jusqu'à la couche ferromagnétique via une couche de cuivre. Ces expériences sont comprises grâce à un modèle de transport semi classique dans un système contenant des électrons, des phonons et des spins quantiques et qui est basé sur l'échange de moment cinétique entre des spins localisés et itinérants. Enfin, nous avons mesuré la dynamique du renversement de l'aimantation de ce système ferromagnétique. Nous montrons que ce retournement se passe en moins d'une picoseconde, ce qui est le retournement d'aimantation le plus rapide jamais observé. Nous montrons que le courant de spin provenant de l'alliage de GdFeCo à un pouvoir réfrigérant sur l'aimantation, déjà visible en moins d'une picoseconde, et qui peut augmenter l'aimantation transitoire du système jusqu'à trente pourcents. Ces résultats sont également compris dans le cadre de notre modèle de transport de chaleur et de moment cinétiqueThe 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
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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.
Abstract (sommario):
La technologie actuelle des lasers ultrabrefs permet de délivrer des impulsions d'une énergie de quelques dizaines de joules dont la durée est de l'ordre de la dizaine de femtosecondes. Focaliser fortement de telles impulsions permet d'obtenir des valeurs d'éclairement considérables, qui sont notamment utilisées pour générer des faisceaux de particules relativistes. Le bon fonctionnement des lasers de ultra-haute intensité nécessite un excellent contrôle des propriétés du faisceau en tout point de la chaîne d'amplification. Développer un tel niveau de contrôle exige de pouvoir mesurer les imperfections temporelles et spatiales des impulsions avec une très grande précision. Cependant, les instruments de mesure utilisés jusqu'à présent négligent un aspect important de la structure des impulsions lasers, qui est lié aux couplages spatio-temporels. Ces derniers représentent une classe particulière d'imperfections, dont l'influence sur les expériences d'ultra-haute intensité a longtemps été négligée. Les rares instruments capables de mesurer ces défauts spécifiques sont pour la plupart inadaptés à la caractérisation de faisceaux de haute énergie. Le travail présenté dans cette thèse a porté sur l'instrument TERMITES, qui permet la caractérisation totale d'impulsions ultrabrèves, ainsi que leur restitution en trois dimensions. TERMITES est une technique auto-référencée qui est basée sur la spectroscopie par transformée de Fourier résolue spatialement. Une première partie de la thèse présente l'étude détaillée et l'optimisation de l'instrument TERMITES. Dans un deuxième temps, différents systèmes laser sont caractérisés grâce à cet instrument, permettant ainsi d'établir la première revue expérimentale des différentes origines de couplages spatio-temporels dans les lasers ultrabrefsCurrent 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
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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.
Abstract (sommario):
Les sources lasers femtosecondes sont utilisées dans grand nombre d’applications (industrielles, médicales, de recherche fondamentale) avec un besoin croissant d’impulsions très énergétiques à haut taux de répétition. Bien que la technologie Ti:Saphir fournisse des impulsions PetaWatt, son taux de répétition s’avère limité. Une alternative est l’utilisation de la technologie fibrée. Cependant, l’énergie extractible d’une seule fibre est intrinsèquement limitée.Une solution prometteuse est alors de réaliser une combinaison de fibres (jusqu’à plus de 10 000 fibres pour l’accélération de particules). La combinaison de fibres par méthode interférométrique (avec un record de 64 fibres combinées en régime continu) a prouvé qu’elle était un excellent candidat pour la combinaison d’un grand nombre de fibres.La collaboration XCAN entre l’Ecole Polytechnique et Thales, vise à réaliser un démonstrateur de combinaison cohérente de 61 fibres amplifiées en régime femtoseconde. Les travaux menés au cours de cette thèse s’inscrivent dans ce projet.Dans un premier temps, afin d’étudier les points durs inhérents au régime femtoseconde tout en s’affranchissant des difficultés liées à l’amplification, la méthode interférométique en régime femtoseconde a été étudiée sur un démonstrateur passif, c’est-à-dire sans amplification, de 19 fibres. Une fois la méthode de mise en phase validée celle-ci a pu être testée avec succès sur le démonstrateur avec amplification du projet XCAN.Nous présentons également les travaux menés afin d’augmenter un paramètre clé des systèmes de combinaison de faisceaux à savoir : l’efficacité de combinaison du système laser. Pour cela, nous avons réalisé une mise en forme de faisceaux issus des fibres de la tête optique. Cette mise en forme, gaussien vers super-gaussien, est réalisée à l’aide de deux réseaux de lames de phase dont nous présenterons le calcul des profils asphériques. Afin de valider expérimentalement nos simulations et après réalisation des lames de phase nous avons pu tester celles-ci sur le démonstrateur passif, démontrant une augmentation de 14 %.Les travaux présentés dans ce manuscrit présentent ainsi les premiers par vers la réalisation d’une nouvelle architecture laser massivement parallèle, capable de délivrer à la fois une haute puissance crête et une haute puissance moyenneFemtosecond 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
6
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.
Abstract (sommario):
Cette thèse s’inscrit dans le cadre du développement d’une source laser TW, de cadence élevée, stabilisée en phase, et délivrant des impulsions de quelques cycles optiques pour explorer la physique attoseconde. De telles impulsions contiennent seulement quelques oscillations de l’onde porteuse (durée de 5 fs à une longueur d’onde centrale de 800 nm) et ne sont pas directement disponibles à la sortie d’une source laser femtoseconde classique. Une technique de post-compression efficace pour obtenir de telles impulsions consiste à élargir le spectre des impulsions laser par automodulation de phase dans une fibre creuse remplie de gaz, puis à compenser la phase spectrale introduite avec des miroirs chirpés. Cette technique convient à des impulsions dont l’énergie est inférieure au millijoule. Au-delà, la transmission et la stabilité du compresseur chutent fortement à cause d'effets non linéaires tels que l'autofocalisation et l'ionisation. Pour comprimer des impulsions énergétiques et dont la phase de l’enveloppe est stabilisée par rapport à la porteuse (stabilisation de la CEP), il est possible de diviser l'impulsion initiale en plusieurs répliques d'énergie moindre et de réduire ainsi l'intensité crête en entrée de fibre. Le spectre de chaque réplique est alors élargi indépendamment. Dans le cadre de cette thèse, la combinaison cohérente passive d'impulsions de quelques cycles optiques issues d'une fibre creuse remplie de gaz est démontrée pour la première fois. L'utilisation de lames biréfringentes (calcite) dont l’orientation est soigneusement déterminée permet de générer et combiner des répliques avec une efficacité élevée. Ainsi, dans le cas d’une division en deux répliques, des impulsions stabilisées en phase (CEP), de durée 6 fs et d'énergie 0.6 mJ ont été générées de manière fiable et reproductible. L’étude détaillée de cette technique, aussi bien théorique qu’expérimentale, a permis de mettre en évidence les conditions requises pour générer des impulsions de quelques cycles optiques et présentant un bon contraste temporel. Plus précisément, la phase spectrale relative entre les répliques peut être mesurée à l'aide d'une méthode interférométrique permettant de quantifier les déphasages résiduels dus à la lame qui recombine les répliques, ainsi que ceux induits lors de la propagation dans la fibre par d'éventuels effets de modulation de phase croisée ou d'ionisation. Les effets qui affectent le processus de combinaison des répliques, tels que les modifications des états de polarisation des répliques ou bien les interactions non linéaires entre les répliques, sont analysés en détail. Une méthode est proposée pour minimiser ces effets, même dans le cas plus critique de la division et combinaison d'impulsions à quatre répliquesThe 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
7
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.
Abstract (sommario):
Pour un grand nombre d'applications, les sources laser impulsionnelles femtoseconde (fs) doivent fournir des puissances toujours plus importantes. En régime impulsionnel, on recherche d'une part une forte puissance crête par impulsion, et d'autre part une forte puissance moyenne, c'est à dire un taux de répétition élevé. Parmi les technologies existantes, les amplificateurs à fibre optique dopée ytterbium présentent de nombreux avantages pour l'obtention de fortes puissances moyennes, cependant le fort confinement des faisceaux dans la fibre sur de grandes longueurs d'interaction induit inévitablement des effets non-linéaires, et limite ainsi la puissance crête accessible. Nous avons étudié lors de cette thèse la combinaison cohérente d'impulsions fs appliquée aux systèmes fibrés. Ayant déjà fait ses preuves dans les régimes d'amplification continu et nanoseconde, la combinaison cohérente de faisceaux (dite combinaison spatiale) permet de diviser une seule et unique source en N voies indépendantes, disposées en parallèle et incluant chacune un amplificateur. Les faisceaux amplifiés sont ensuite recombinés en espace libre en un seul et unique faisceau, qui contient toute la puissance des N amplificateurs sans accumuler les effets non-linéaires. Cette architecture permet théoriquement de monter d'un facteur N le niveau de puissance crête issu des systèmes d'amplification fibrés. Au cours de cette thèse, nous avons démontré la compatibilité et l'efficacité de cette méthode en régime d'amplification fs avec deux amplificateurs, selon différents procédés. Les expériences démontrent d'excellentes efficacités de combinaison ainsi qu'une très bonne préservation des caractéristiques temporelles et spatiales initiales de la source. Les procédés de combinaison cohérente nécessitent cependant un accord de phase entre différents amplificateurs stable dans le temps, assuré en premier lieu par une boucle de rétroaction. Nous avons poursuivi notre étude en concevant une architecture totalement passive, permettant une implémentation plus simple d'un système de combinaison à deux faisceaux sans asservissement électronique. Enfin, une méthode passive de combinaison cohérente dans le domaine temporel est étudiée et caractérisée dans le domaine fs, et implémentée simultanément avec la méthode passive de combinaison spatiale proposée précédemment. Ces expériences démontrent la validité et la variété des concepts proposés, ainsi que leurs nombreuses perspectives pour les systèmes d'amplification fs fibrés.
8
Douti, 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.
Abstract (sommario):
La tenue au flux des traitements de surfaces optiques constitue aujourd'hui un enjeu majeur pour le développement des lasers de puissance à courtes durées d'impulsion. L’étude des interactions laser-matière en régime sub-picoseconde a montré que l’initiation de l'endommagement laser est le résultat de processus d’excitation fortement non-linéaires (photoionisation, ionisation par impact et avalanche électronique). Dans cette thèse, un dispositif de tests multiparamétriques a été développé pour l’étude de la tenue au flux des composants optiques. Différentes études expérimentales ont été menées sur des matériaux diélectriques, en couche mince ou en matériau massif, afin d’apporter des données nouvelles sur les matériaux couches minces assez peu étudiés dans la littérature. L’étude de l’influence de la longueur d’onde a révélé différentes phases de prédominance des processus d’ionisation. L’influence du nombre de tirs à différentes longueurs d’ondes aussi a été étudiée, en considérant différentes techniques de dépôt de couches minces. L’interprétation de ces résultats expérimentaux est soutenue par un modèle de simulation numérique que nous présentons en détail dans le manuscrit. Une place, non moins importante, a été accordée dans notre travail à la métrologie de l’endommagement. Nous avons proposé et appliqué l’utilisation d’un dispositif original de mesure quantitative de phase pour l’analyse des processus d’endommagement. Et pour terminer nous avons développé un système de microscopie pompe-sonde afin de pousser les investigations sur les processus en jeu lors de l’interaction laser-matière en régime sub-picosecondeLaser 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
9
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.
Abstract (sommario):
La microscopie électronique et la diffraction d’électrons ont permis de comprendre l’organisation des atomes au sein de la matière. En utilisant une source courte temporellement, il devient possible de mesurer les déplacements atomiques ou les modifications de la distribution électronique dans des matériaux. A ce jour, les sources ultra-brèves pour les expériences de diffraction d’électrons ne permettent pas d’atteindre une résolution temporelle inférieure à la centaine de femtosecondes (fs). Les accélérateurs laser-plasma sont de bons candidats pour atteindre une résolution temporelle de l’ordre de la femtoseconde. De plus, ces accélérateurs peuvent fonctionner à haut taux de répétition, permettant d’accumuler un grand nombre de données.Dans cette thèse, un accélérateur laser-plasma fonctionnant au kHz a été développé et construit. Cette source accélère des électrons à une énergie de 100 keV environ à partir d’impulsions laser d’énergie 3 mJ et de durée 25 fs. La physique de l’accélération a été étudiée, démontrant entre autres l’effet du front d’onde laser sur la distribution transverse des électrons.Les premières expériences de diffraction avec ce type de sources ont été réalisées. Une expérience de preuve de principe a montré que la qualité de la source est suffisante pour obtenir de belles images de diffraction sur des feuilles d’or et de silicium. Dans un second temps, la dynamique structurelle d’un échantillon de Silicium a été étudiée avec une résolution temporelle de quelques picosecondes, démontrant le potentiel de ce type de sources.Pour augmenter la résolution temporelle à sub-10 fs, il est nécessaire d’accélérer les électrons à des énergies relativistes de quelques MeV. Une étude numérique a montré que l’on peut accélérer des paquets d’électrons ultra-courts grâce à des impulsions laser de 5 mJ et 5 fs. Il serait alors possible d’atteindre une résolution temporelle de l’ordre de la femtoseconde. Finalement, une expérience de post-compression des impulsions laser due à l’ionisation d’un gaz a été réalisée. La durée du laser a pu être réduite d’un facteur deux, et l’homogénéité de ce processus a été étudiée expérimentalement et numériquementElectronic 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
10
Salamé, Rami. "Études sur la filamentation des impulsions laser ultrabrèves dans l’air". Thesis, Lyon 1, 2009. http://www.theses.fr/2009LYO10124/document.
Abstract (sommario):
La propagation des impulsions laser ultra brèves dans l’air se fait sous la forme de structures d’une centaine de micromètres de diamètre appelées filaments, qui ont entre autres les propriétés d’être autoguidées, de se propager sur plusieurs centaines de mètres, de générer un continuum de lumière blanche, etc. Ces propriétés originales trouvent de nombreuses applications dans le domaine de la télédétection des polluants par mesures lidar, le déclenchement et le guidage de la foudre par laser, le LIBS à distance, etc.Au cours de mon travail de thèse, nous avons mené de nombreuses expériences de laboratoire et sur terrain dans le cadre du projet Tera mobile. Nous avons en particulier étudié la géométrie de la filamentation, sa robustesse dans une région de turbulence étendue, la propagation verticale d’un faisceau d’impulsions ultra brèves dans un régime multi joules, et des applications atmosphériques de la filamentation. Nous avons par exemple caractérisé la distribution angulaire de l’émission conique dans le visible et dans l’ultraviolet. Nous avons également prouvé que la turbulence atmosphérique n’est pas un facteur limitant de la propagation des filaments qui arrivent même à garder leurs propriétés spectrales nécessaires aux applications atmosphériques. Enfin nous avons illustré une méthode de déclenchement et de guidage de foudre par laser et réalisé une expérience de condensation de gouttelettes d’eau assistée par laser en laboratoire ainsi que dans une atmosphère réelleUltrashort 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
Libri sul tema "Pulses laser femtoseconde":
1
Rullière, Claude, a cura di. Femtosecond Laser Pulses. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-662-03682-2.
2
Rullière, Claude, a cura di. Femtosecond Laser Pulses. New York, NY: Springer New York, 2005. http://dx.doi.org/10.1007/b137908.
3
Akhmanov, S. A. Optics of femtosecond laser pulses. New York: American Institute of Physics, 1992.
4
Mitsuru, Uesaka, a cura di. Femtosecond beam science. London: Imperial College Press, 2005.
5
Grossmann, F. Theoretical femtosecond physics: Atoms and molecules in strong laser fields. Berlin: Springer, 2008.
6
Paul-Henri, Barret, e Palmer Michael 1962-, a cura di. High power and femtosecond lasers: Properties, materials, and applications. Hauppauge, NY: Nova Science Publishers, 2009.
7
Diels, Jean-Claude. Ultrashort laser pulse phenomena: Fundamentals, techniques, and applications on a femtosecond time scale. San Diego, Calif: Academic Press, 1995.
8
Diels, Jean-Claude. Ultrashort laser pulse phenomena: Fundamentals, techniques, and applications on a femtosecond time scale. San Diego: Academic Press, 1996.
9
Diels, Jean-Claude. Ultrashort laser pulse phenomena: Fundamentals, techniques, and applications on a femtosecond time scale. 2a ed. Amsterdam: Elsevier / Academic Press, 2006.
10
1939-, Hannaford Peter, a cura di. Femtosecond laser spectroscopy. New York, NY: Springer, 2005.
Capitoli di libri sul tema "Pulses laser femtoseconde":
1
Hirlimann, C. "Laser Basics". In Femtosecond Laser Pulses, 1–23. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-662-03682-2_1.
2
Bonvalet, A., e M. Joffre. "Terahertz Femtosecond Pulses". In Femtosecond Laser Pulses, 285–305. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-662-03682-2_10.
3
Hirlimann, C. "Pulsed Optics". In Femtosecond Laser Pulses, 25–52. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-662-03682-2_2.
4
Ducasse, A., C. Rullière e B. Couillaud. "Methods for the Generation of Ultrashort Laser Pulses: Mode-Locking". In Femtosecond Laser Pulses, 53–82. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-662-03682-2_3.
5
Hirlimann, C. "Further Methods for the Generation of Ultrashort Optical Pulses". In Femtosecond Laser Pulses, 83–110. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-662-03682-2_4.
6
Amand, T., e X. Marie. "Pulsed Semiconductor Lasers". In Femtosecond Laser Pulses, 111–58. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-662-03682-2_5.
7
Salin, F. "How to Manipulate and Change the Characteristics of Laser Pulses". In Femtosecond Laser Pulses, 159–76. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-662-03682-2_6.
8
Sarger, L., e J. Oberlé. "How to Measure the Characteristics of Laser Pulses". In Femtosecond Laser Pulses, 177–201. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-662-03682-2_7.
9
Rullière, C., T. Amand e X. Marie. "Spectroscopic Methods for Analysis of Sample Dynamics". In Femtosecond Laser Pulses, 203–59. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-662-03682-2_8.
10
Joffre, M. "Coherent Effects in Femtosecond Spectroscopy: A Simple Picture Using the Bloch Equation". In Femtosecond Laser Pulses, 261–84. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-662-03682-2_9.
Atti di convegni sul tema "Pulses laser femtoseconde":
1
Loesel, F. H., P. Brockhaus, J. P. Fischer, M. H. Götz, M. Tewes, M. Niemz, J. F. Bille e F. Noack. "Femtosecond pulse lasers for nonthermal tissue ablation". In The European Conference on Lasers and Electro-Optics. Washington, D.C.: Optica Publishing Group, 1994. http://dx.doi.org/10.1364/cleo_europe.1994.cwn2.
Abstract (sommario):
Ultrashort laser pulses enable a process of tissue ablation that is of great interest for medical therapy. In contrast to long pulsed or cw lasers, where the applied energy leads to heating and vaporization of irradiated tissue, the ablation process in the ultrashort pulse range is initiated by a plasma formation in the laser focus, resulting in tissue removal.1 Using picosecond pulses this ablation mechanism is already well established in ophthalmology. The accuracy and the absence of undesired thermal side effects made the plasma-mediated ablation a promising technique in other medical fields, e.g., neurosurgery.
2
Cormier, Jean-François, Michel Piché, François Salin, Patrick George e Jennifer Watson. "Power limiting and temporal break-up in self-mode-locked lasers". In The European Conference on Lasers and Electro-Optics. Washington, D.C.: Optica Publishing Group, 1994. http://dx.doi.org/10.1364/cleo_europe.1994.ctuk13.
Abstract (sommario):
Self-mode-locking of solid-state lasers is now established as the most powerful method to generate femtosecond optical pulses.1-4 Best results reported so far3,4 were obtained with Ti:sapphire lasers where pulse durations down to 10 femtoseconds were achieved. Self-modelocking is attributed5 to Kerr lensing (selffocusing) in the gain medium or in other intracavity materials; in properly designed cavities, Kerr lensing has the effect of reducing the diffractional losses or of improving the overlap between the pump and laser beams. Under such circumstances, Kerr lensing produces a nonlinear gain favoring the growth of intense short pulses at the expense of multimode (cw) oscillations. It is known experimentally3 that high-power, self-mode-locked lasers switch from one-pulse to two-pulse emission. In this paper, we analyze the large-signal response of nonlinear cavities in order to understand the stability range for one- and two-pulse emission.
3
Juodkazis, Saulius, e Hiroaki Misawa. "Three-Dimensional Structuring of Materials by Femtosecond Laser Pulses". In Femtosecond Laser Microfabrication. Washington, D.C.: OSA, 2009. http://dx.doi.org/10.1364/lm.2009.lmtub1.
4
Schulz, P. A., M. J. Lagasse, R. W. Schoenlein e J. G. Fujimoto. "Femtosecond Ti:Al2O3 injection seeded laser". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1988. http://dx.doi.org/10.1364/oam.1988.mee2.
Abstract (sommario):
A Ti:Al2O3 amplifier has a very wide (200-nm) gain bandwidth and thus excellent potential for amplifying and tuning of femtosecond laser pulses. We have used a Ti:Al2O3 injection seeded laser pumped by a 2-mJ copper vapor laser to amplify the output of a synchronously pumped dye laser. To pump the dye laser a mode-locked Nd:YAG laser is pulse compressed to 5 ps using a fiber and grating pair and frequency doubled. A single pulse from the 82-MHz 400-fs pulse train of the dye laser is selected using an acoustooptic modulator. This pulse is mode matched and coupled with a beam splitter into the Ti: Al2O3 laser. A wavelength-independent Faraday isolator is placed in the beam path to protect the acoustooptic modulator from the high-power Ti: Al2O3 laser output. The injection seeded laser1 employs an 8% output coupler. With only 0.1 pJ of incident seed energy at 790 nm, the Ti: Al2O3 laser is mode-locked. The output is a 100-ns pulse train with pulses spaced by 2.1 ns, which is determined by the Ti: Al2O3 cavity length. A single pulse contains 1 µJ and has a pulse width of 1.5 ps. These pulses have been recompressed with a grating pair to 300-fs pulse widths.
5
Shah, Jay D., Tissa C. Gunaratne, Xin Zhu, Vadim Lozovoy e Marcos Dantus. "Effect of Pulse Shaping on Micromachining Transparent Dielectrics". In Femtosecond Laser Microfabrication. Washington, D.C.: OSA, 2009. http://dx.doi.org/10.1364/lm.2009.lmtua4.
6
Tsang, Thomas. "Generation of high-order solitons from a mode-locked Ti:sapphire laser". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1993. http://dx.doi.org/10.1364/oam.1993.thdd.45.
Abstract (sommario):
The advent of femtosecond lasers has lead to the production of solitonlike pulses in colliding pulse modelocked (CPM) lasers.1–4 In this conference, we present the production of such solitonlike pulses in another laser system—a self-mode-locked Thsapphire laser.5
7
Becker, P. C., C. H. Brito Cruz e A. G. Prosser. "Generation of Sub-100 Femtosecond Pulses Tunable in the 690-750 nm Range". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oam.1990.pdp2.
Abstract (sommario):
We report the generation of tunable femtosecond pulses in the 690-750 nm wavelength region, by selective continuum amplification and subsequent recompression, in a CPM based ultrashort pulse system. The continuum is generated in a jet of ethylene glycol with amplified CPM pulses at 620 nm. The amplified continuum pulses are typically of duration 75-85 femtoseconds (assuming a sech2 profile) with energies per pulse of several microjoules, at a repetition rate of 8.5 kHz. The pump source for the amplifier is a copper vapor laser. The dyes used as the gain medium for the continuum amplifier are LDS 698 and LDS 750, which, even though they are significantly less efficient than Rhodamine or Styryl 9, accomplish the desired purpose. These pulses are then launched in a 10 mm length of single mode fiber to produce a broad spectral continuum which is then compressed to pulses of duration 12-13 femtoseconds. Ultrashort pulses in this wavelength range will be useful for resonant investigations of quantum well structures.
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Sucha, G., M. Wegener e D. S. Chemla. "Kilohertz Amplification of Picosecond Pulses at 1.55µm to Near-Microjoule Energies". In International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/up.1990.wc11.
Abstract (sommario):
There is much interest in femtosecond spectroscopy of semiconductor heterostrucures in materials which have a bandgap wavelength near 1.5µm. For a long time, the time resolution of these studies was limited to several picoseconds which is characteristic of the synchronously pumped F-center lasers. Recently, stable sources of 100 fsec pulses around 1.5µm have been developed, using F-center lasers. The soliton laser [1] and subsequently the additive-pulse-modelocked laser (APM) [2,3] are capable of producing 100-200 fsec pulses routinely with up to 1.5 nJ of energy. However, for some applications, higher pulse energies are needed. In particular, femtosecond continuum generation requires pulse energies of a few microjoules. The NaCl F-center system [4] is particularly attractive as a gain medium for femtosecond pulses because of its large gain bandwidth (200 nm), and its relatively long gain storage lifetime (200 nsec). We report here, die amplification of picosecond pulses to energies of of .24 µJ using F-centers in NaCl. Pulse energies of several microjoules should be easily obtainable in the future.
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Agnesi, A., J. C. Diels, P. Di Trapani, V. Kubecek, J. Marek, G. Reali e C. Y. Yeh. "Q-switched Nd lasers for femtosecond dye laser pumping". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oam.1990.tuss1.
Abstract (sommario):
A two-photon absorbing semiconductor inserted in the cavity of a Nd Q-switched mode-locked lasers is shown to act simultaneously as energy limiter and pulse compressor. The latter action is due to self defocusing by the carriers generated during the pulse. With a proper positioning of an intracavity aperture, maximum losses occur at the tail of the pulse, resulting in pulse compression. Extracavity measurements have shown that the compression factor can be as large as 50%. The energy limiting effect ensures optimum operation for the intracavity saturable absorber. As a result, the pulse train is stabilized and stretched out to include at least 100 pulses of nearly equal energy and duration (10 ps for the Nd:YAG laser). The reproducibility of the stabilized pulses is better than 1.5 from shot to shot. Typically, the evolution towards steady state in a fs laser requires about 100 round-trips. With an energy/pulse of 10 J, and at least 100 pulses of identical energy, the new source has unique characteristics for pumping fs dye lasers.
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Fletcher, Luke B., Jon J. Witcher, Denise M. Krol e Richard K. Brow. "The Role of Metaphosphate Glass Composition on Changes to the Glass Network Structure After Modification by Femtosecond Laser Pulses". In Femtosecond Laser Microfabrication. Washington, D.C.: OSA, 2009. http://dx.doi.org/10.1364/lm.2009.lmtub4.
Rapporti di organizzazioni sul tema "Pulses laser femtoseconde":
1
Alexander, Dennis R., Jianchao Li, Haifeng Zhang e David Doerr. Transmission Measurements of Femtosecond Laser Pulses Through Aerosols. Fort Belvoir, VA: Defense Technical Information Center, dicembre 2003. http://dx.doi.org/10.21236/ada419719.
2
Emma, P. Femtosecond and Subfemtosecond X-Ray Pulses from a SASE Based Free-Electron Laser. Office of Scientific and Technical Information (OSTI), marzo 2004. http://dx.doi.org/10.2172/826765.
3
Campbell, Benjamin, e Jeremy Andrew Palmer. Investigation of temporal contrast effects in femtosecond pulse laser micromachining of metals. Office of Scientific and Technical Information (OSTI), giugno 2006. http://dx.doi.org/10.2172/887259.
4
Greenfield, S. R., D. J. Gosztola e M. R. Wasielewski. Molecular systems for ultrafast optical switching: Controlling electron transfer reactions with femtosecond laser pulses. Office of Scientific and Technical Information (OSTI), aprile 1994. http://dx.doi.org/10.2172/10141178.
5
Schumacher, Andreas B. Regenerative Amplification of Femtosecond Pulses: Design andConstruction of a sub-100fs, muon J Laser System. Office of Scientific and Technical Information (OSTI), ottobre 1996. http://dx.doi.org/10.2172/876714.
6
Schumacher, A. B. Regenerative amplification of femtosecond pulses: Design and construction of a sub-100fs, {mu}J laser system. Office of Scientific and Technical Information (OSTI), ottobre 1996. http://dx.doi.org/10.2172/437714.
7
Wraback, Michael, Anand Sampath e Dimitra Stratis-Cullum. Compact Femtosecond Pulse Approach to Explosives Detection Combining InN-Based Time Domain Terahertz Spectroscopy and Laser-Induced Breakdown Spectroscopy. Fort Belvoir, VA: Defense Technical Information Center, agosto 2008. http://dx.doi.org/10.21236/ada486227.
8
Heinz, Tony F. An Apparatus with Femtosecond Time Resolution and Atomic Spatial Resolution for the Study of Surface Processes Induced by High Intensity Ultrafast Laser Pulses. Fort Belvoir, VA: Defense Technical Information Center, gennaio 1998. http://dx.doi.org/10.21236/ada348521.
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Chichibu, Shigefusa F., e Kouji Hazu. Investigation and Characterization of Defects in Epitaxial Films for Ultraviolet Light Emitting Devices Using FUV Time-Resolved Photoluminescence, Time-Resolved Cathodoluminescence, and Spatio-Time-Resolved Cathodoluminescence Excited Using Femtosecond Laser Pulses. Fort Belvoir, VA: Defense Technical Information Center, maggio 2013. http://dx.doi.org/10.21236/ada587678.