Literatura académica sobre el tema "Recuit laser nanoseconde"
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Artículos de revistas sobre el tema "Recuit laser nanoseconde"
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Qu Yan, 曲研, 宁超宇 Ning Chaoyu, 邹淑珍 Zou Shuzhen, 于海娟 Yu Haijuan, 陈雪纯 Chen Xuechun, 许爽 Xu Shuang, 左杰希 Zuo Jiexi, 韩世飞 Han Shifei, 李心瑶 Li Xinyao y 林学春 Lin Xuechun. "纳秒脉冲掺镱全光纤激光器研究进展". Infrared and Laser Engineering 51, n.º 6 (2022): 20220055. http://dx.doi.org/10.3788/irla20220055.
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Xu, Dong, Yao Yao, Xing Fu y Chao Wang. "Design of Micromachining System Based on Nanosecond Pulsed Laser". Key Engineering Materials 645-646 (mayo de 2015): 1049–53. http://dx.doi.org/10.4028/www.scientific.net/kem.645-646.1049.
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In recent years, pulsed laser processing technology is widely used in MEMS device manufacturing, aerospace technology, precision instrument manufacturing and circuit board processing. According to the characteristics of nanosecond laser, this paper designs a novel nanosecond pulsed laser micromachining system with PMAC card as its core unit. The system can achieve automation control of laser parameters and movement pattern of motion system by software, which can easily realize automatic processing of point, line, and plane structure in micron scale. In this paper, several groups of experiments are taken to test the reliability and accuracy of the machining system and find the group to obtain the best processing result.
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Gogoi, Tutul y Rajni Kumar. "Design and Development of a Laser Warning Sensor Prototype for Airborne Application". Defence Science Journal 73, n.º 3 (12 de mayo de 2023): 332–40. http://dx.doi.org/10.14429/dsj.73.18662.
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Due to recent developments in high-energy laser systems, the laser is becoming one of the most potential choices in battlefield applications. Laser of a laser range finder used to find target distance may be of nanosecond pulse width and a single pulse may be sufficient to gather the instantaneous range information. A laser target designator is a similar laser with higher energy and with programmable pulse repetition frequencies5,7. Detection of such a specific battlefield laser radiation along with recognizing friend or foe is required for countermeasures. Designing a laser detection system that is capable of detecting such low-power level laser pulses of nanosecond pulse width at a long distance is a critical design and a challenging task. Again detecting a wide wavelength band that can start from 500 nm to around 1700 nm range using a single detector or device is also a challenging task. In this work, a sensor system is being designed and a prototype is developed to cover such a long band detection using a single detector for high-energy lasers. Also, in addition to detecting hostile code, the direction of an incoming laser beam is tried to incorporate into this sensor. The sensor can be utilized to detect unknown or non-friendly laser illumination from within a specific angular cone and distance.
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HUBENTHAL, FRANK, CHRISTIAN HENDRICH, HASSAN OUACHA, DAVID BLÁZQUEZ SÁNCHEZ y FRANK TRÄGER. "PREPARATION OF GOLD NANOPARTICLES WITH NARROW SIZE DISTRIBUTIONS AND WELL DEFINED SHAPES". International Journal of Modern Physics B 19, n.º 15n17 (10 de julio de 2005): 2604–9. http://dx.doi.org/10.1142/s0217979205031390.
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In this contribution, we present the results of recent experiments with the objective of tailoring the size and shape of gold nanoparticles with nanosecond laser pulses. The technique is based on the size and shape dependent surface plasmon resonance frequencies of metal nanoparticles. In our recent experiments gold nanoparticles were prepared by deposition of atoms on dielectric substrates followed by diffusion and nucleation. This usually results in ensembles of oblate nanoparticles with a broad size and shape distribution. Irradiating the gold particles during growth with nanosecond laser pulses makes it possible to produce nanoparticles with a predetermined axial ratio independent of size. For example, irradiating gold nanoparticles with a photon energy of 1.65 eV during growth stabilizes an axial ratio of a/b = 0.14, a being the short axis and b the long axis of the ellipsoidal nanoparticles. Furthermore, post-growth irradiation permits tailoring the average size of the nanoparticles by laser induced surface diffusion and evaporation of atoms. In principle, it is possible to eliminate all particles of undesired sizes by choosing the appropriate photon energies. We demonstrate that narrowing of the width of the surface plasmon resonance from initially 0.52 eV (half width at half maximum) to 0.2 eV is possible by using a single laser frequency. Combining both methods, i.e. laser irradiation during and after growth, finally results in a narrow size and shape distribution of the particles.
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GAUTHIER, J. C., F. AMIRANOFF, C. CHENAIS-POPOVICS, G. JAMELOT, M. KOENIG, C. LABAUNE, E. LEBOUCHER-DALIMIER, C. SAUTERET y A. MIGUS. "LULI activities in the field of high-power laser–matter interaction". Laser and Particle Beams 17, n.º 2 (abril de 1999): 195–208. http://dx.doi.org/10.1017/s0263034699172057.
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LULI will play an important role as a major laser ICF and IFE support facility in Europe after recent or future changes (ASTERIX-Garching, CEA-Limeil) in large laser system programs. We will review the research activities which have been carried out at LULI during the last 2 years both in the nanosecond regime and in the subpicosecond ultraintense regime. As part of the LULI upgrade project, a new 30-J, 300-fs, 100-TW ultraintense laser chain has been commissioned in 1997. This laser has allowed the first complete demonstration of wakefield electron acceleration and is presently used to study new concepts in laser fusion and laser–plasma interaction experiments in the relativistic regime.
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Gora, Wojciech S., Jesper V. Carstensen, Krystian L. Wlodarczyk, Mads B. Laursen, Erica B. Hansen y Duncan P. Hand. "A Novel Process for Manufacturing High-Friction Rings with a Closely Defined Coefficient of Static Friction (Relative Standard Deviation 3.5%) for Application in Ship Engine Components". Materials 15, n.º 2 (7 de enero de 2022): 448. http://dx.doi.org/10.3390/ma15020448.
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In recent years, there has been an increased uptake for surface functionalization through the means of laser surface processing. The constant evolution of low-cost, easily automatable, and highly repeatable nanosecond fibre lasers has significantly aided this. In this paper, we present a laser surface-texturing technique to manufacture a surface with a tailored high static friction coefficient for application within driveshafts of large marine engines. The requirement in this application is not only a high friction coefficient, but a friction coefficient kept within a narrow range. This is obtained by using nanosecond-pulsed fibre lasers to generate a hexagonal pattern of craters on the surface. To provide a suitable friction coefficient, after laser processing the surface was hardened using a chromium-based hardening process, so that the textured surface would embed into its counterpart when the normal force was applied in the engine application. Using the combination of the laser texturing and surface hardening, it is possible to tailor the surface properties to achieve a static friction coefficient of ≥0.7 with ~3–4% relative standard deviation. The laser-textured and hardened parts were installed in driveshafts for ship testing. After successfully performing in 1500 h of operation, it is planned to adopt the solution into production.
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Carillon, A., A. Klisnick, G. Jamelot, B. Gauthé, F. Gadi y P. Jaeglé. "Recent Results on Soft X-Ray Amplification by Lithium-Like Ions in Plasmas". International Astronomical Union Colloquium 102 (1988): 247–50. http://dx.doi.org/10.1017/s0252921100107833.
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AbstractWe have shown that several transitions of Li-like ions give rise to population inversions during the recombination of laser-plasmas /1/. An extensive study has been made for the 3d–5f transition lying at 105.7 Å. It has shown a gain coefficient with a maximum around 2cm−1occuring about 6 nanosecond after the top of the 2-ns laser pulse. We extended recently this study to the 3d–4f line ar 154.7 Å and we observed a similar value of gain with the same temporal behaviour. Moreover, following calculated predictions for higher-Z ions /2/, we studied the 3d-5f transition of S13+which takes place at 65.2 Å. This study gives the first preliminary evidence of a gain coefficient of about 1 cm−1.
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Liang, Yuchen, Guang Feng, Xiaogang Li, Haoran Sun, Wei Xue, Kunpeng Zhang y Fengping Li. "Simulation Analysis of Nanosecond Laser Processing of Titanium Alloy Based on Helical Trepanning". Applied Sciences 12, n.º 18 (8 de septiembre de 2022): 9024. http://dx.doi.org/10.3390/app12189024.
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Titanium alloy is a type of high-strength material that is difficult to process. In particular, in the aerospace field, the processing accuracy of titanium alloy is high. Recently, laser processing has emerged as a new technology with high processing precision. However, the laser processing methods have obvious differences in processing accuracy and effect. Among them, the laser spiral scanning method plays an important role in welding and drilling, but owing to the complexity of the laser molten pool behavior, there have been limited studies on the material removal mechanism based on laser spiral scanning. To understand the variable process of titanium alloy melt pool in laser spiral scanning processing, a light heat conduction model with mass transfer source term was simulated. The effects of laser power, scanning speed, and scanning path on the morphology were studied. The simulation results show that the unit energy density was the main factor for material removal, and the distribution of the material temperature affected the size of the recast layer. The experimental and simulation results were compared, and good agreement between them was observed. This study can provide a research foundation for the further application of laser spiral scanning technology.
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Polman, A., W. C. Sinke, M. J. Uttormark y Michael O. Thompson. "Pulsed-laser induced transient phase transformations at the Si–H2O interface". Journal of Materials Research 4, n.º 4 (agosto de 1989): 843–56. http://dx.doi.org/10.1557/jmr.1989.0843.
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Phase transformations at the Si–H2O interface, induced by nanosecond pulsed laser irradiation, were studied in real time. Si samples were irradiated using a 4 ns pulse from a Q-switched frequency-doubled Nd:YAG laser while immersed in the transparent liquid. Using time-resolved conductivity and reflectivity techniques, in combination with modeling of optical parameters and heat flow, transient processes in the Si, the H2O, and at the interface have been unraveled. In the liquid, local rapid heating occurs as a result of heat flow across the interface, and formation of a low-density steam phase occurs on a nanosecond timescale. Expansion of this phase is followed by a collapse after 200 ns. These rapid phase transformations in the water initiate a shock wave with a pressure of 0.4± 0.3 kbar. Transient phase transformations and the heat flow into the water during the laser pulse influence the energy coupling into the sample, resulting in an effective laser pulse shortening. The pulse shortening and the additional heat flow into the water during solidification result in a 30% enhancement of the solidification velocity for 270 nm deep melts. Cross-section transmission electron microscopy data reveal that the Si surface is planar after irradiation and is inert to chemical reactions during irradiation. Recent experiments described in the literature concerning pulsed-laser induced synthesis at the solid-liquid interface are reviewed and discussed in the context of the fundamental phenomena presently observed.
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Lou, Rui, Guodong Zhang, Guangying Li, Xuelong Li, Qing Liu y Guanghua Cheng. "Design and Fabrication of Dual-Scale Broadband Antireflective Structures on Metal Surfaces by Using Nanosecond and Femtosecond Lasers". Micromachines 11, n.º 1 (24 de diciembre de 2019): 20. http://dx.doi.org/10.3390/mi11010020.
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Antireflective surfaces, with their great potential applications, have attracted tremendous attention and have been the subject of extensive research in recent years. However, due to the significant optical impedance mismatch between a metal surface and free space, it is still a challenging issue to realize ultralow reflectance on a metal surface. To address this issue, we propose a two-step strategy for constructing antireflective structures on a Ti-6Al-4V (TC4) surface using nanosecond and femtosecond pulsed lasers in combination. By controlling the parameters of the nanosecond laser, microgrooves are first scratched on the TC4 surface to reduce the interface reflection. Then, the femtosecond laser is focused onto the sample surface with orthogonal scanning to induce deep air holes and nanoscale structures, which effectively enhances the broadband absorption. The antireflection mechanism of the dual-scale structures is discussed regarding morphological characterization and hemispherical reflectance measurements. Finally, the modified sample surface covered with micro-nano hybrid structures is characterized by an average reflectance of 3.1% over the wavelengths ranging from 250 nm to 2250 nm.
Tesis sobre el tema "Recuit laser nanoseconde"
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Larmande, Yannick. "Réalisation de jonctions ultra-minces par recuit laser : applications aux détecteurs UV". Thesis, Aix-Marseille 2, 2010. http://www.theses.fr/2010AIX22114/document.
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Depuis les années 1970, la taille des composants n’a cessé de diminuer. La réalisation de jonctions ultra-minces et fortement dopées est devenue un point clef dans la réduction des dispositifs microélectroniques. Les techniques de production doivent évoluer afin de répondre aux spécifications drastiques, en termes de taille des zones dopées et de leurs propriétés électriques, des prochains noeuds technologiques. Dans ce travail de thèse nous avons étudié le procédé d’activation au laser de dopants implantés par immersion plasma. Le laser à excimère utilisé (ArF) est absorbé dans moins de 10 nmde silicium, ce qui va permettre un recuit local. De plus, la courte durée d’impulsion va assurer un faible budget thermique, limitant la diffusion des dopants. En associant cette technique à l’implantation ionique par immersion plasma, dont l’intérêt est de pouvoir travailler à de très basses tensions d’accélération (quelques dizaines d’eV), nous pouvons réaliser des jonctions avec un fort taux d’activation sans diffusion. Après avoir présenté les différentes techniques de dopage pouvant être utilisées, nous avons décrit les dispositifs expérimentaux de traitement et de caractérisation utilisés. Des simulations ont permis de comprendre le rôle des paramètres laser sur le profil de température du siliciumen surface. Après avoir choisi le laser le plus adapté parmi les lasers ArF, KrF et XeCl (respectivement: 193 nm - 15 ns, 248 nm - 35 ns, 308 nm - 50 ns), nous avons observé l’effet du nombre de tirs et de la mise en forme de faisceau afin d’optimiser le procédé. Pour terminer, des inhomogénéités dues aux bords de faisceau ont été mises en évidence et étudiées afin d’enlimiter l’effetSince the 1970’s, the components size has steadily declined. The realization of highly-dopedultra shallow junctions became a key point in the reduction of microelectronic devices. Them anufacturing processes must evolve to meet the stringent specifications of the next technologynodes, in particular in terms of dimension and electrical properties of the doped area.In this thesis we have studied the process of laser annealing of dopants implanted by plasmaimmersion. The ArF excimer laser we used is absorbed in less than 10 nm of silicon, whichallows a local heating. Moreover, the short pulse duration provides a low thermal budget whichreduces the dopant diffusion. By combining this technique with plasma immersion ion implantation, which is interesting because of the very low acceleration voltage (few tens of eV), we can produce highly activated junctions without diffusion. After a presentation of the different doping techniques that may be used, we describe the experimental treatment and the characterization tools that we used. We have used numerical simulations to understand the role of the laser parameters on the temperature profile of the silicon surface. After choosing the most suitable laser between ArF, KrF and XeCl (respectively :193 nm - 15 ns, 248 nm - 35 ns, 308 nm - 50 ns), we studied the influence of the number of shots and beam shaping to optimize the process. Finally, inhomogeneities caused by the beam edgeshave been studied and identified in order to improve the laser scan process
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Larmande, Yannick. "Réalisation de jonctions ultra-minces par recuit laser : application aux détecteurs UV". Phd thesis, Université de la Méditerranée - Aix-Marseille II, 2010. http://tel.archives-ouvertes.fr/tel-00557507.
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Depuis les années 1970, la taille des composants n'a cessé de diminuer. La réalisation de jonctions ultra-minces et fortement dopées est devenue un point clef dans la réduction des dispositifs microélectroniques. Les techniques de production doivent évoluer afin de répondre aux spécifications drastiques, en termes de taille des zones dopées et de leurs propriétés électriques, des prochains noeuds technologiques. Dans ce travail de thèse nous avons étudié le procédé d'activation au laser de dopants implantés par immersion plasma. Le laser à excimère utilisé (ArF) est absorbé dans moins de 10 nm de silicium, ce qui va permettre un recuit local. De plus, la courte durée d'impulsion va assurer un faible budget thermique, limitant la diffusion des dopants. En associant cette technique à l'implantation ionique par immersion plasma, dont l'intérêt est de pouvoir travailler à de très basses tensions d'accélération (quelques dizaines d'eV), nous pouvons réaliser des jonctions avec un fort taux d'activation sans diffusion. Après avoir présenté les différentes techniques de dopage pouvant être utilisées, nous avons décrit les dispositifs expérimentaux de traitement et de caractérisation utilisés. Des simulations ont permis de comprendre le rôle des paramètres laser sur le profil de température du silicium en surface. Après avoir choisi le laser le plus adapté parmi les lasers ArF, KrF et XeCl (respectivement : 193 nm - 15 ns, 248 nm - 35 ns, 308 nm - 50 ns), nous avons observé l'effet du nombre de tirs et de la mise en forme de faisceau afin d'optimiser le procédé. Pour terminer, des inhomogénéités dues aux bords de faisceau ont été mises en évidence et étudiées afin d'en limiter l'effet.
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Darif, Mohamed. "Etude de la recristallisation du silicium par procédé laser nanoseconde pour la formation et le contrôle des jonctions ultraminces". Phd thesis, Université d'Orléans, 2011. http://tel.archives-ouvertes.fr/tel-00639065.
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La réalisation des jonctions ultra-minces et fortement dopées est un enjeu majeur pour la continuité de la miniaturisation des dispositifs microélectroniques. Les techniques de production en termes d'implantation ionique et de recuit d'activation doivent évoluer afin de répondre aux exigences du marché de la microélectronique. Le travail de recherche de cette thèse s'inscrit dans le cadre du projet ALDIP (Activation Laser de Dopants implantés par Immersion Plasma) et a pour objectif l'étude et le contrôle du procédé laser pour la réalisation des jonctions ultra-minces sur silicium (cristallin ou préamorphisé par implantation ionique) dopé au bore. En effet, le contrôle in situ du processus de recuit laser s'avère indispensable pour l'industrialisation de ce procédé qui jusqu'au là a fait l'objet de plusieurs études de recherche. Ainsi, le travail réalisé durant cette thèse a permis de mettre en place une méthode de contrôle, in situ, qui a été calibrée afin de la rendre accessible par le milieu industriel. Il s'agit de la méthode RRT (Réflectivité Résolue en Temps). Pour mener ce travail de thèse à terme, nous avons utilisé deux dispositifs expérimentaux comportant chacun un laser UV impulsionnel nanoseconde, un système optique d'homogénéisation et un dispositif RRT. Par ailleurs, plusieurs techniques de caractérisation ex situ ont été employées (TOF-SIMS, MEB, ...) notamment dans l'objectif de calibrer la méthode RRT. Ce travail expérimental a été couplé à une étude de simulation numérique qui a permis de mieux comprendre les paramètres clés du recuit laser et qui s'est souvent avérée en bon accord avec les résultats expérimentaux obtenus.
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Esposito, Laura. "Mise en oeuvre de procédés innovants pour l'optimisation de contacts TiSi pour les technologies imageurs avancées". Electronic Thesis or Diss., Aix-Marseille, 2021. http://theses.univ-amu.fr.lama.univ-amu.fr/210319_ESPOSITO_505pj561fjb969hmp55qmrno_TH.pdf.
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Dans les dispositifs de capteurs d’image les siliciures de titane sont utilisés afin de réaliser les contacts entre les transistors et les interconnections de cuivre. Une nouvelle problématique émerge alors d’une co-intégration des contacts en siliciures de Ti et de nickel : former le siliciure de titane optimal (C54-TiSi2) a une température plus faible que la température de formation classique (800°C). Afin de réduire la température de formation du siliciure, l’influence du recuit laser nanoseconde UV (UV-NLA) sur la formation des contacts en siliciures de Ti a été étudiée. Pour cela, des dépôts consécutifs de films de Ti et de TiN avec des épaisseurs inférieures à 10 nm ont été réalisés après un traitement de surface spécifique. Des recuits par UV-NLA à différentes densités d’énergies appliquées selon différents nombres de tirs et suivis par des recuits thermiques rapides (RTA) ont été réalisés. Les différents échantillons ont été caractérisés par plusieurs méthodes dont la mesure quatre pointes, la diffraction de rayons X, et la microscopie électronique en transmission. L'utilisation du UV-NLA permet la formation d’une phase amorphe à l’état solide, puis dans le cas de l’utilisation du laser avec plusieurs tirs combinés à un RTA ultérieur, la formation de la phase C54-TiSi2 à basse température a été démontrée. Les études réalisées sur les substrats dopés et/ou polycristallins, ainsi que ceux sur plaques avec motifs photolithographiés indiquent que dans l’état actuel, l’intégration du traitement UV-NLA dans le processus d’industrialisation est plus complexe qu’escomptée. Des perspectives permettant de favoriser l’intégration de ce nouveau recuit sont également discutéesIn image sensor devices, Ti silicides are used to establish contacts between transistors and copper interconnects. A new problematic emerges with the co-integration of Ti-based and Ni-based silicided contacts: the titanium silicide (C54-TiSi2) needs to be formed at a lower temperature than the conventional formation temperature (800°C). In order to reduce the temperature of silicide formation, the influence of nanosecond laser annealing on Ti silicide contact formation has been investigated in this PhD work. To do so, consecutive deposition of Ti and TiN films with thicknesses below 10 nm were carried out after a specific surface treatment. Annealing by UV nanosecond laser (UV-NLA) at different energy densities, different numbers of shots and followed by rapid thermal annealing (RTA) for various temperatures were performed. The different samples were characterized by several methods including: four-point probe measurements, X-ray diffraction, and transmission electron microscopy. The main results obtained with the use of UV-NLA are the following: it enables the formation of an amorphous phase in the solid state and the formation of the metastable C40-TiSi2 phase becomes possible by melting the first nanometers of the substrate. By combining multiple laser shots and a subsequent RTA, the formation of the C54-TiSi2 phase at low temperature of 650 °C has been demonstrated. Studies carried out on doped and/or polycrystalline substrates, as well as on wafers with nanometric patterns indicate that, in the current state, the integration of UV- NLA into the industrial process is more complex than expected. Prospects for promoting the integration of UV-NLA are also discussed
Capítulos de libros sobre el tema "Recuit laser nanoseconde"
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Zelenska, Kateryna, Volodymyr Gnatyuk, Hideki Nakajima, Wanichaya Mekprasart y Wisanu Pecharapa. "XPS Study of the In/CdTe Interface Modified by Nanosecond Laser Irradiation". En Recent Advances in Technology Research and Education, 73–79. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-99834-3_10.
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"Laser-plasma X-ray emission: its creation, diagnosis, and applications in transient diffraction". En Time-resolved Diffraction, editado por Allan A. Hauer y George A. Kyrala, 71–105. Oxford University PressOxford, 1997. http://dx.doi.org/10.1093/oso/9780198500322.003.0003.
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Abstract Laser-plasma interactions are a truly remarkable source of X-rays. They are capable of producing X-ray bursts with durations from a few picoseconds (or less)3 to hundreds of nanoseconds. They are also rather bright sources, with effective source sizes down to a few micrometres. In recent years, there has also been considerable success in generating coherent radiation with wavelengths as short as 100 ÅOne of the most useful aspects of laser-plasma X-ray sources is their ability to be accurately synchronized with other events that can be driven, triggered, or otherwise stimulated by the laser light. The X-ray source can thus be used to probe and diagnose a wide variety of phenomena in fields such as plasma physics, the physics of fluids, and solid-state physics. These characteristics make the laser plasma a very valuable source for transient X-ray diffraction, scattering, and absorption studies. In this chapter, we will describe some of the physical processes involved in the X-ray generation and also some of the measurement tools that have been diffraction to diagnose the emission.
Actas de conferencias sobre el tema "Recuit laser nanoseconde"
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Reichardt, Thomas A. y Robert P. Lucht. "Degenerate Four-Wave Mixing Spectroscopy using Picosecond Lasers: Theoretical Analysis". En Laser Applications to Chemical and Environmental Analysis. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/lacea.1996.lthc.3.
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Degenerate four-wave mixing (DFWM) has emerged in recent years as a potentially powerful technique for quantitative measurement of minor species in gas-phase media.1,2 However, a complicated collision-rate dependence of the DFWM signal is observed when lasers with pulse lengths of several nanoseconds are used.3,5 On the other hand, picosecond lasers possess pulse widths shorter than the typical collisional time in atmospheric gas-phase media, and use of such lasers for DFWM measurements6 could reduce the sensitivity of the technique to the collision rate.2,7 While pulsed lasers are usually utilized to perform gas-phase DFWM measurements, DFWM analytical models are generally limited to the assumption of continuous wave (cw) laser inputs. These cw models have been applied successfully to modeling gas-phase DFWM with nanosecond-pulse lasers, where the pulse length (~10 nsec) is much longer than the typical collisional time (~100 psec) in atmospheric-pressure flames. In this paper, we use direct numerical integration (DNI) of the density matrix to investigate theoretically the use of lasers with pulse lengths (τ L ) much shorter than characteristic collision times (τ C ) for quantitative DFWM spectroscopy in gas-phase media. Both purely homogeneously broadened resonances and resonances that are both collision- and Doppler-broadened are considered.
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Kapitan, D., D. W. Coutts y C. E. Webb. "On pulsed laser ablation of metals: comparing the relative importance of thermal diffusion in the nanosecond - femtosecond regime". En The European Conference on Lasers and Electro-Optics. Washington, D.C.: Optica Publishing Group, 1998. http://dx.doi.org/10.1364/cleo_europe.1998.cthh75.
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In recent years numerous reports on pulsed laser ablation of metals using various laser sources have fostered the discussion regarding the limitations due to thermal diffusion to produce feature sizes on (sub-)micron scale smaller than the diffusion length. Particularly in the light of novel micromachining applications, the relative benefits of using pulsed nanosecond (ns) lasers in the visible, such as copper vapour lasers and frequency doubled Nd:YAG, versus femtosecond (fs) Ti:Sapphire lasers operating in the infrared, remains debatable.
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Tyan, Y. S., K. C. Pan, D. R. Preuss, G. R. Olin y F. Vazan. "Recent Advances In Phase-Change Media". En Optical Data Storage. Washington, D.C.: Optica Publishing Group, 1987. http://dx.doi.org/10.1364/ods.1987.wc2.
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Phase-change media, utilizing the switching between amorphous states and crystalline states induced by the heating of a focused laser beam for information storage, have been the subject of research for many years. The major challenge is to develop materials having appropriate crystallization kinetics so that the amorphous state can be crystallized in a matter of nanoseconds under the influence of the heating laser beam and yet remain stable at operating and keeping temperatures. For erasable operation, the kinetics should also allow the quenching of the material from the molten state produced by the heating laser beam into the amorphous state. This requires the crystallization rate at just below the melting point to fall within a narrow range determined by the maximum crystallization rate allowed by practical considerations and the cooling rate of the media.
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Haner, M., F. Spano y Warren S. Warren. "Experimental techniques for generation of arbitrarily shaped and phased nanosecond and picosecond pulse trains". En International Laser Science Conference. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/ils.1986.fh5.
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We have shown, in a series of recent papers, that generation of laser pulse sequences with completely controlled delays, pulse shapes, and relative phases permits selective vibrational inversion, enhances velocity resolution in gases, and differentiates between relaxation mechanisms in condensed phases. We present new results with two fundamentally different technologies developed in our laboratory to produce such pulse sequences. Nanosecond pulse shaping and phase shifting is accomplished by acoustooptic modulation of a continuous ring laser.1 We have now experimentally demonstrated pulse envelopes as complicated as
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Tewolde, Mahder, Di Liu, David J. Hwang y Jon P. Longtin. "Laser Processing of Thermal Sprayed Coatings for Thermoelectric Generators". En ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ht2013-17791.
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Recent research has shown that thermal spray has the potential to fabricate thermoelectric devices at low cost and high volumes. An integral aspect of the device fabrication is laser processing of the various thermal sprayed layers, which is used to form electrically isolated regions and minimize heat loss to adjacent structures. In this article, experimental results are presented for the laser patterning of thermal spray samples ranging from 50μm to 2mm in thickness. The optimization of process parameters is important for successful electrical isolation and high-quality features. In this study results are presented several short-pulse lasers (nanosecond and picosecond) in which laser power, laser wavelength, type of focusing lens, processing speed, repetition rate, and pressure and flow of purge gas were varied. The optimum laser parameters were those that minimize the heat affected zone and delamination due to thermal damage while providing maximum material removal. The resulting laser patterns were characterized using both optical and scanning electron (SEM) microscopy, and by verifying electrical isolation between patterned regions using contact resistance measurements. Cut quality attributes including kerf width and edge profile were also studied, and their dependence on process parameters reported.
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Yalin, Azer P., Sachin Joshi, Adam Reynolds, Morgan Defoort, Bryan Willson, Almantas Galvanauskas, Yuji Matsuura y Mitsunobo Miyagi. "Fiber Delivered Systems for Laser Ignition of Natural Gas Engines". En ASME 2006 Internal Combustion Engine Division Fall Technical Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/icef2006-1574.
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Past research has shown that laser ignition is capable of operating high bmep engines at high efficiency and with low emission levels. However, for laser ignition systems to be adopted by industry, one requires a practical (and economical) mode of beam delivery other than the conventional open-path beam delivery that has been used in much of the past research. One potential beam delivery method is via optical fibers capable of handling high peak power. This paper summarizes our recent efforts in this area. Using coated hollow fibers, our research group has demonstrated the delivery of laser pulses to form optical sparks both on the bench-top and for ignition and operation of a single cylinder of an ARES engine. When held relatively straight, the hollow fibers allow transmission of nanosecond pulse energies of 10s of milli-Joules with transmission above 90% and sufficient beam quality for spark formation. We have also been able to deliver optical sparks on the bench-top with high peak power pulsed fiber lasers. Pulse energies in those experiments were approximately 2 mJ. Other recent work has studied the transmission characteristics of recently developed photonic crystal fibers.
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Dunn, Malcolm H. "Optical parametric oscillators". En The European Conference on Lasers and Electro-Optics. Washington, D.C.: Optica Publishing Group, 1994. http://dx.doi.org/10.1364/cleo_europe.1994.tutorial.d.
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Optical parametric oscillators (OPOs) use nonlinear optical effects to generate coherent radiation over extensive and continuous tuning ranges. In recent years the advent of new and improved optically nonlinear materials coupled with the development of increasingly refined lasers, in particular diode-laser-pumped solidstate lasers, as pump sources for OPOs has led to a resurgence of interest in these devices as practical sources of tunable, coherent radiation. High optical-to-optical conversion efficiencies have now been demonstrated in devices that operate from the femtosecond through the nanosecond and picosecond time domains to truly continuous-wave oscillation. Spectral control can be to the transform limit. Decade tuning ranges converting the near ultraviolet, visible, and near infrared are now possible from a single, compact device. This tutorial review talk will introduce the basic physical principles behind these devices, and will report on the current status of the rapidly evolving science and technology of OPOs throughout all of the above time domains.
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Lyons, S. C., G. L. Oppo, W. J. Firth, J. R. M. Barr y C. Coia. "Beam Quality Characterisation of Nanosecond Optical Parametric Oscillators". En The European Conference on Lasers and Electro-Optics. Washington, D.C.: Optica Publishing Group, 1998. http://dx.doi.org/10.1364/cleo_europe.1998.cthh35.
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We present a novel approach to the numerical modelling of pulsed nanosecond optical parametric oscillators (OPO’s). Our model expands upon a recent procedure [1] to consider the case of a nondegenerate, singly resonant OPO. A single partial differential equation describes the temporal and transverse variations of the resonated signal field and also accounts for diffraction, phase mis-matching and idler absorption. The pump and idler fields are reconstructed from the signal dynamics. The numerical integration of our single equation model is considerably faster than that of the corresponding three coupled equations.
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Willis, David A. y Mohammad Hendijanifard. "Nanosecond Time-Resolved Measurements of Hole Opening During Laser Micromachining of Aluminum Films". En ASME 2012 Third International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/mnhmt2012-75331.
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Laser micromachining of aluminum films on glass substrates is investigated using a time-resolved transmission imaging technique with nanosecond resolution. Micromachining is performed using a 7 ns pulse-width Nd:YAG laser operating at the 1064 nm wavelength for fluences ranging from 2.2 to 14.5 J/cm2. Transmission imaging uses a nitrogen laser-pumped dye laser with a 3 ns pulse-width and 500 nm wavelength. Images are taken from the back of the sample at various time delays with respect to the beginning of the ablation process, allowing the transient hole opening process to be observed and measured. Results show that for high fluences the holes begin opening during the laser pulse and that the major portion of the holes have opened within the first 50 ns of the process. The second stage of the process is slower and lasts between 100–200 ns. The rapid hole opening process can be attributed to melt expulsion due to recoil pressure on the surface of the melt pool rather than Marangoni flow. Recoil pressure may be due to vaporization at the free surface at low fluences and phase explosion (explosive liquid-vapor phase change) at higher fluences. Measurements of the transient shock wave position are used to estimate the pressure behind the shock wave and indicate pressures at high as 89 atm during ablation. The high pressure above the laser spot results in pressure on the molten surface, leading to expulsion of the molten pool in the radial direction.
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Hendijanifard, Mohammad y David A. Willis. "Modeling of Pressure Evolution During Nanosecond Laser Ablation of Metal Films". En ASME 2009 Heat Transfer Summer Conference collocated with the InterPACK09 and 3rd Energy Sustainability Conferences. ASMEDC, 2009. http://dx.doi.org/10.1115/ht2009-88130.
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Nanosecond laser ablation is studied using a theoretical model combined with experimental data from laser ablation of metal films. The purpose of the research is to obtain the recoil pressure boundary condition resulting from explosive phase change. The ablation experiments are performed using a Nd:YAG laser of 1064 nm wavelength and 7 ns pulse width at full width half maximum. Three samples, 200 and 1000 nm aluminum films and 1000 nm nickel films, are used in the experiments. The transient shock wave positions are obtained by a time-resolved shadowgraph technique. A N2-laser pumped dye laser with 3 ns pulse width is used as an illumination source and is synchronized with the ablation laser to obtain the transient shock wave position with nanosecond resolution. The transient shock position is used in a model for finding the shock wave speed as well as the pressure, temperature, and velocity just behind the shock wave. A power law is used for fitting curves on the experimentally obtained shock wave position. Knowing the shock wave position, the normal shock equations are used to calculate the thermo-fluid properties behind the shock wave. The solutions are compared with the Taylor-Sedov solution for spherical shocks and the reason for the deviation is described. The thermo-fluid property results show similar trends for all tested samples. The results show that the Taylor-Sedov solution under-estimates the pressure behind the shock wave when compared to the normal shock results.