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Journal articles on the topic 'Lasers Laser beams'
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1
Lisiecki, A. "Comparison of Titanium Metal Matrix Composite Surface Layers Produced During Laser Gas Nitriding of Ti6Al4V Alloy by Different Types of Lasers." Archives of Metallurgy and Materials 61, no. 4 (December 1, 2016): 1777–84. http://dx.doi.org/10.1515/amm-2016-0287.
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Abstract The article presents the results of a comparative study of the nitriding process of titanium alloy substrate using two lasers with different characteristics of laser beams. One of the applied lasers was a high power diode laser emitting at a dominant wavelength of 808 nm, with a rectangular laser beam spot, and multimode energy distribution across the spot. The second laser was a solid state Yb:YAG disk laser emitting at a wavelength of 1.03 μm, with a circular beam spot, characterized by near Gaussian energy distribution across the spot. In a case of both lasers single stringer beads with a similar width and at similar energy input were produced. As a result of melting of the substrate with a laser beam in a pure gaseous nitrogen atmosphere composite surface layers with in situ precipitated titanium nitrides embedded in the metallic matrix of titanium alloy were produced, in both cases. However, the surface topography and structure is different for the surface layers produce by different lasers at the same processing parameters and width of laser beams.
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Ivashko, A. M., V. E. Kisel, and N. V. Kuleshov. "POWER SCALING IN CONTINUOUS-WAVE YB:YAG MICROCHIP LASER FOR MEASURING APPLICATIONS." Devices and Methods of Measurements 8, no. 3 (September 27, 2017): 222–27. http://dx.doi.org/10.21122/2220-9506-2017-8-3-222-227.
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Characteristics optimization of lasers used in different measuring systems is of great interest up to now. Diode-pumped microchip lasers is one of the most perspective ways for development of solid-state light sources with minimal size and weight together with low energy power consumption. Increasing of output power with good beam quality is rather difficult task for such type of lasers due to thermal effects in the gain crystal under high pump power.The investigation results of continuous-wave longitudinally diode-pumped Yb:YAG microchip laser are presented. In the presented laser radiation from multiple pump laser diodes were focused into the separate zone in one gain crystal that provides simultaneous generation of multiple laser beams. The energy and spatial laser beam characteristics were investigated.Influence of neighboring pumped regions on energy and spatial laser beams parameters both for separate and for sum laser output was observed. The dependences of laser output power from distance between neighboring pumped regions and their number were determined. Decreasing of laser output power was demonstrated with corresponding distance shortening between pumped regions and increasing their quantity with simultaneous improvement of laser beam quality.Demonstrated mutual influence of neighboring pumped regions in the longitudinally diode pumped Yb:YAG microchip laser allow as to generate diffraction limited Gaussian beam with 2W of continuous-wave output power that 30 % higher than in case of one pumped zone.
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Bingham, Robert. "Basic concepts in plasma accelerators." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 364, no. 1840 (February 2006): 559–75. http://dx.doi.org/10.1098/rsta.2005.1722.
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In this article, we present the underlying physics and the present status of high gradient and high-energy plasma accelerators. With the development of compact short pulse high-brightness lasers and electron and positron beams, new areas of studies for laser/particle beam–matter interactions is opening up. A number of methods are being pursued vigorously to achieve ultra-high-acceleration gradients. These include the plasma beat wave accelerator (PBWA) mechanism which uses conventional long pulse (∼100 ps) modest intensity lasers ( I ∼10 14 –10 16 W cm −2 ), the laser wakefield accelerator (LWFA) which uses the new breed of compact high-brightness lasers (<1 ps) and intensities >10 18 W cm −2 , self-modulated laser wakefield accelerator (SMLWFA) concept which combines elements of stimulated Raman forward scattering (SRFS) and electron acceleration by nonlinear plasma waves excited by relativistic electron and positron bunches the plasma wakefield accelerator. In the ultra-high intensity regime, laser/particle beam–plasma interactions are highly nonlinear and relativistic, leading to new phenomenon such as the plasma wakefield excitation for particle acceleration, relativistic self-focusing and guiding of laser beams, high-harmonic generation, acceleration of electrons, positrons, protons and photons. Fields greater than 1 GV cm −1 have been generated with monoenergetic particle beams accelerated to about 100 MeV in millimetre distances recorded. Plasma wakefields driven by both electron and positron beams at the Stanford linear accelerator centre (SLAC) facility have accelerated the tail of the beams.
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Sharma, Prerana. "Cross Focusing of two Coaxial Gaussian Beams with Relativistic and Ponderomotive Nonlinearity." Zeitschrift für Naturforschung A 67, no. 1-2 (February 1, 2012): 10–14. http://dx.doi.org/10.5560/zna.2011-0064.
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This paper presents the cross focusing of two high power lasers by taking off-axial contributions of the laser beams in a collisionless plasma. Due to relativistic and ponderomotive nonlinearities the two laser beams affect the dynamics of each other and cross focusing takes place. The expressions for the laser beam intensities by using the eikonal method are derived. The contributions of the r2 and r4 terms are incorporated. By expanding the eikonal and the other relevant quantities up to the fourth power of r, the solution of the pump laser beam is obtained within the extended paraxial ray approximation. Filamentary structures of the laser beams are observed due to the relativistic and the ponderomotive nonlinearity. The focusing of the laser beams is shown to become fast in the extended paraxial region. Using the laser beam and the plasma parameters, appropriate for beat wave processes, the filaments of the laser beams are studied and the relevance of these results to beat wave processes is pointed out.
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MALKA, V., A. F. LIFSCHITZ, J. FAURE, and Y. GLINEC. "GeV MONOENERGETIC ELECTRON BEAM WITH LASER PLASMA ACCELERATOR." International Journal of Modern Physics B 21, no. 03n04 (February 10, 2007): 277–86. http://dx.doi.org/10.1142/s0217979207042057.
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Laser plasma accelerators produce today ultra short, quasi-monoenergetic and collimated electron beams with potential applications in material science, chemistry and medicine. The laser plasma accelerator used to produce such an electron beam is presented. The design of a laser based accelerator designed to produce more energetic electron beams with a narrow relative energy spread is also proposed here. This compact approach should permit a miniaturization and cost reduction of future accelerators and associated X-Free Electrons Lasers (XFEL).
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Kiefer, Johannes, Anna-Lena Sahlberg, Dina Hot, Marcus Aldén, and Zhongshan Li. "Misalignment Effects in Laser-Induced Grating Experiments." Applied Spectroscopy 70, no. 12 (July 20, 2016): 2025–28. http://dx.doi.org/10.1177/0003702816653128.
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Laser-induced grating spectroscopy (LIGS) is an experimental method in which two pulsed laser beams and a continuous-wave laser beam have to be superimposed under well-defined angles to generate a coherent signal beam. In this Note, the possible effects of different forms of misalignment are examined. This includes the overlap of the pump lasers as well as the influence of the probe laser alignment on the temporal profile of the signal.
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Huang, Cing-Yi, Kuo-Chih Chang, and Shu-Chun Chu. "Experimental Investigation of Generating Laser Beams of on-Demand Lateral Field Distribution from Digital Lasers." Materials 12, no. 14 (July 10, 2019): 2226. http://dx.doi.org/10.3390/ma12142226.
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A new type of laser system, known as a digital laser, was proposed in 2013. Many well-known laser beams with known analytical forms have been successfully generated in digital lasers. However, for a light field that does not have an analytical form, such as a multi-point light field or a light field with an arbitrary lateral distribution, how to generate such a light field from a digital laser has not been explored. The goal of this study was to experimentally explore how to generate an on-demand lateral laser field in a digital laser. In this study, a multi-point Gaussian laser beam was successfully generated in a digital laser by both controlling the range of the laser gain and the modulation of the phase boundary of the end of the cavity. This study then generated laser beams with an on-demand lateral field distribution by generating a superimposed multi-point laser field in a digital laser. Examples of triangles, rectangles, and letter T-shaped light fields produced by digital lasers were experimentally demonstrated. In summary, this study experimentally showed that a laser beam with an on-demand lateral field distribution could be generated in a digital laser by generating a superimposed multi-point laser field in a digital laser, in which a laser gain region covering the entire intra-cavity multi-point light field and the projected SLM (spatial light modulator) modulation function adopting a mimic amplitude mask are both used.
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Varshnety, Prateek, Vivek Sajal, Prashant Chauhan, Ravindra Kumar, and Navneet K. Sharma. "Effects of transverse static electric field on terahertz radiation generation by beating of two transversely modulated Gaussian laser beams in a plasma." Laser and Particle Beams 32, no. 3 (June 10, 2014): 375–81. http://dx.doi.org/10.1017/s026303461400024x.
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AbstractResonant excitation of terahertz (THz) radiation by nonlinear coupling of two filamented spatial-Gaussian laser beams of different frequencies and wave numbers is studied in plasma having transverse static electric field. The static ponderomotive force due to filamented lasers is balanced by the pressure gradient force which gives rise to transverse density ripple, while, the nonlinear ponderomotive force at frequency difference of beating lasers couples with density ripple giving rise to stronger transverse nonlinear current which results into the excitation of THz radiation at resonance. The coupling is further enhanced by the presence of static electric field and spatial-Gaussian nature of laser beams. An increase of six-fold in the normalized amplitude of THz is observed by applying a direct current field of about 50 KV. Effects of frequency, laser beam width, and periodicity factor of modulated laser amplitude are studied for the efficient THz radiation generation. These results can be utilized for generating controlled tunable THz sources for medical applications using low filament intensities (~ 1014 W/cm2) of beating lasers.
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Raitsin, A. M., and M. V. Ulanovskii. "Correct measurement methodology spatial-energy characteristics of laser beams." Metrologiya, no. 2 (July 4, 2021): 4–19. http://dx.doi.org/10.32446/0132-4713.2021-2-4-19.
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A methodology for correct measurements of the spatial and energy characteristics of a laser beam is considered, based on the determination of the initial moments of the spatial intensity distribution in the beam cross section. The classification of radiation fields participating in the measuring process is given: emitted, measured and measured. It is shown that ISO 11146:2005 “Lasers and laser-related equipment. Test methods for laser beam widths, divergence angles and beam propagation ratios, Part 1-3” for measuring the spatial and energy characteristics of laser beams leads to incorrect measurements. This is due to the fact that the recommendations for the application of ISO 11146:2005 do not take into account the dynamic range of the used matrix radiation detectors, and the characteristics of the emitted field of interest to the user turn out to be diverging, which violates the uniformity of measurements. Moreover, the conditions ensuring the convergence of the results are practically impracticable. To solve these problems, it is proposed to establish and regulate the lower level of the dynamic range of measurements of the intensity of the used matrix receivers and to consider the spatial and energy characteristics of the emitted field of interest to the user, depending on the set value of the lower level. It is shown that measurements with this methodology become correct and make it possible to compare the characteristics of laser beams obtained by different array detectors. Formulas are given that take into account the effect of the lower level of the dynamic range of the matrix radiation detectors on the measurement result. These formulas should be recommended for inclusion in the updated edition of the national standard GOST R ISO 11146-2008 “Lasers and laser installations (systems). Methods for measuring widths, divergence angles and propagation coefficients of laser beams. Parts 1-3”.
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Adonin, A., V. Turtikov, A. Ulrich, J. Jacoby, D. H. H. Hoffmann, and J. Wieser. "Intense heavy ion beams as a pumping source for short wavelength lasers." Laser and Particle Beams 27, no. 3 (July 17, 2009): 379–91. http://dx.doi.org/10.1017/s0263034609000494.
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AbstractThe high energy loss of heavy ions in matter as well as the small angular scattering makes heavy ion beams an excellent tool to produce almost cylindrical and homogeneously excited volumes in matter. This aspect can be used to pump short wavelength lasers. For the first time, a beam of heavy ions was used to pump a short wavelength gas laser in an experiment performed at the GSI ion accelerator facility in December 2005. In this experiment, the well-known KrF* excimer laser was pumped with an intense uranium beam. Pulses of an uranium beam compressed down to 110 ns (full width at half maximum) with initial particle energy of 250 MeV per nucleon were stopped inside a gas laser cell. A mixture of an excimer laser premix gas (95.5%Kr + 0.5%F2) and a buffer gas (Ar) in different proportions was used as the laser gas. The maximum beam intensity reached in the experiment was 2.5 × 109particles per pulse, which resulted in 34 J/g specific energy deposited in the laser gas. The laser effect on the transition at λ = 248 nm has been successfully demonstrated by various independent methods. There, the laser threshold was reached with a beam intensity of 1.2 × 109particles per pulse, and the energy of the laser pulse of about 2 mJ was measured for an ion beam intensity of 2 × 109particles per pulse. As a next step, it is planned to reduce the laser wavelength down to the vacuum ultraviolet spectral region, and to proceed to the excimer lasers of the pure rare gases. The perspectives for such experiments are discussed and the detailed estimations for Xe and Kr cases are given. We believe that the use of heavy ion beams as a pumping source may lead to new pumping schemes on the higher lying level transitions and considerably shorter wavelengths, which rely on the high cross sections for multiple ionization of the target species.
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GOURLEY, P. L., and M. E. WARREN. "SURFACE-EMITTING SEMICONDUCTOR LASER STRUCTURES FABRICATED BY MICROLITHOGRAPHY." Journal of Nonlinear Optical Physics & Materials 04, no. 01 (January 1995): 27–81. http://dx.doi.org/10.1142/s0218863595000045.
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Vertical cavity surface-emitting lasers are semiconductor microcavity lasers created by epitaxial growth and surface processing technologies which exploit new 3-dimensional architectures. The physical properties of these microcavities are intimately related to the geometry imposed on the semiconductor materials. The surface-emitting geometry is ideal for fabricating 2-dimensional laser structures by optical and electron beam lithography. These structures include large area, phase-locked arrays with shaped beams for higher power applications and 2-dimensional nanostructures such as photonic lattices for controlling microscopic optical properties. This paper reviews the basic physics of epitaxial surface-emitting laser cavities and recent technical advances in the microfabrication of 2-dimensional surface-emitting laser arrays and photonic lattices.
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Hematizadeh, A., F. Bakhtiari, S. M. Jazayeri, and B. Ghafary. "Strong terahertz radiation generation by beating of two laser beams in magnetized overdense plasma." Laser and Particle Beams 34, no. 3 (July 22, 2016): 527–32. http://dx.doi.org/10.1017/s0263034616000410.
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AbstractTerahertz (THz) radiation generation by nonlinear mixing of two laser beams, obliquely incident on an overdense plasma is investigated. In an overdense plasma, the laser beams penetrate to only thin layer of a plasma surface and reflected. At this thin layer, the laser beams exert a ponderomotive force on the electrons of plasma and impart them oscillatory velocity at the different frequency of lasers. THz waves appear in the reflected component from the plasma surface. The amplitude of THz waves can be augmented by applying the magnetic field perpendicular to the direction of propagation of lasers. It is found that the field strength of the emitted THz radiations is sensitive to the angle of incident of the laser beams, beat frequency, and magnetic field strength. In this scheme, the magnetic field strength plays an important role for strong THz wave generation.
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Laksono, Pranoto Budi. "A STUDY OF THE INFLUENCE OF 650 nm LASER INTERFERENCE ON VISIBLE LASER LIGHT COMMUNICATION SYSTEM." TEKNOKOM 4, no. 2 (September 1, 2021): 60–65. http://dx.doi.org/10.31943/teknokom.v4i2.66.
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Visible Laser Light Communication System (VLLC) is a wireless communication system, using laser as the medium. In the data transfer process, it is possible to have optical interference where 2 laser beams coincide with one point on the reflector. Research on the effect of laser source interference has been carried out by several researchers including mitigation actions to reduce its effects. This experiment uses 2 optical distance sensors that produce a laser with a wavelength of 650 nm with a power <=4.1 mW and with the direction of the laser beam both of them cross each other. To determine the effect of the interference of two laser beams when crossing the communication process in the visible light communication system, a reflector is used which can capture the two laser beams and the reflector can be shifted gradually so that a condition can be obtained where the two laser beams meet at one point. From the measurements made at the points after the laser beam crossing, the measurements at the point where the beam crossed, and the measurements at the points before the beam crossing, it was obtained data, at the exact point where the laser beam crossed the interference occurred, which is indicated by unstable output voltage of the two lasers, so that communication at the point of intersection is disrupted. However, if outside the point of contact both before and after the point of contact, interference and communication systems will not occur.
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Han, Kai, Wenda Cui, Yi Yang, Fengjie Xi, Xiao Li, and Shaojun Du. "Evaluating the Potential of Laser Beam Quality Improvement by Adaptive Optics System." International Journal of Optics 2019 (December 5, 2019): 1–6. http://dx.doi.org/10.1155/2019/1970406.
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AO (adaptive optics) systems have been extensively used to improve the beam quality in high-energy lasers; however, few studies have focused on how much the beam quality could be improved. A novel evaluation criteria and factor is presented in this paper. The factor, defined as power in ring (PIR), is expressed by distinguishing the low- and high-spatial frequency components in the far-field laser intensity distribution. Beams with different PIR values are generated in our model, and then they are compensated by AO systems. Calculation result shows that the PIR factor could evaluate a laser beam’s improvement potential by an AO system quantitatively.
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Hematizadeh, A., S. M. Jazayeri, and B. Ghafary. "Generation of terahertz radiation by beating of two laser beams in collisional magnetized plasma." Laser and Particle Beams 34, no. 4 (August 30, 2016): 569–75. http://dx.doi.org/10.1017/s0263034616000513.
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AbstractThis paper presents analytical calculations for terahertz (THz) radiation by beating of two cosh-Gaussian laser beams in a density rippled collisional magnetized plasma. Lasers beams exert a ponderomotive force on the electrons of plasma in beating frequency which generates THz waves. The magnetic field was considered parallel to the direction of lasers which leads to propagate right-hand circularly polarized or left-hand circularly polarized waves in the plasma depending on the phase matching conditions. Effects of collision frequency, decentered parameter of lasers and the magnetic field strength are analyzed for THz radiation generation. By the optimization of laser and plasma parameters, the efficiency of order 27% can be achieved.
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Kügler, Helge, and Frank Vollertsen. "Consideration of Absorption Coefficient Changes in Numerical Simulations of Laser Forming." Advanced Technologies & Materials 44, no. 1 (June 28, 2019): 1–5. http://dx.doi.org/10.24867/atm-2019-1-001.
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Material processing with laser beams is well-known in nowadays production. Compared to CO2 lasers, modern solid state lasers are, amongst others, popular because of higher energy efficiency and higher absorption when metals like steel and aluminum are irradiated. However, the absorption of metals is not only dependent on the chemical composition of the work piece metal and the laser beam wavelength. Previous investigations determined the oxidation of the surface as an influence on laser beam absorption changes due to multiple irradiation. In this study, a method is presented for considering the absorption coefficient changes caused by surface oxidation in numerical simulations. Reproductions of single trajectories were assigned with appropriate absorption coefficients calculated from a function generated by reference tryouts. With the described approach, benefits are gained for numerical simulations of laser beam forming (like bending) and other processes with an iterative heat input.
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Badziak, J., and J. Domański. "Towards ultra-intense ultra-short ion beams driven by a multi-PW laser." Laser and Particle Beams 37, no. 03 (July 26, 2019): 288–300. http://dx.doi.org/10.1017/s0263034619000533.
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AbstractThe multi-petawatt (PW) lasers currently being built in Europe as part of the Extreme Light Infrastructure (ELI) project will be capable of generating femtosecond light pulses of ultra-relativistic intensities (~1023–1024 W/cm2) that have been unattainable so far. Such laser pulses can be used for the production of high-energy ion beams with unique features that could be applied in various fields of scientific and technological research. In this paper, the prospect of producing ultra-intense (intensity ≥1020 W/cm2) ultra-short (pico- or femtosecond) high-energy ion beams using multi-PW lasers is outlined. The results of numerical studies on the acceleration of light (carbon) ions, medium-heavy (copper) ions and super-heavy (lead) ions driven by a femtosecond laser pulse of ultra-relativistic intensity, performed with the use of a multi-dimensional (2D3 V) particle-in-cell code, are presented, and the ion acceleration mechanisms and properties of the generated ion beams are discussed. It is shown that both in the case of light ions and in the case of medium-heavy and super-heavy ions, ultra-intense femtosecond multi-GeV ion beams with a beam intensity much higher (by a factor ~102) and ion pulse durations much shorter (by a factor ~104–105) than achievable presently in conventional radio frequency-driven accelerators can be produced at laser intensities of 1023 W/cm2 predicted for the ELI lasers. Such ion beams can open the door to new areas of research in high-energy density physics, nuclear physics and inertial confinement fusion.
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CHAUHAN, P. K., S. T. MAHMOUD, R. P. SHARMA, and H. D. PANDEY. "Effect of laser ripple on the beat wave excitation and particle acceleration." Journal of Plasma Physics 73, no. 1 (February 2007): 117–30. http://dx.doi.org/10.1017/s002237780600465x.
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Abstract.This paper presents the effect of ripple on the plasma wave excitation process and acceleration of electrons in a laser produced plasma. The plasma wave is generated by the beating of two coaxial lasers of frequencies ω1 and ω2, such that ω1-ω2≅ωp. One of the main laser beams also has intensity spikes. The nonlinearity due to the relativistic mass variation depends not only on the intensity of one laser beam but also on the second laser beam. Therefore the behavior of the first laser beam affects the second laser beam, hence cross-focusing takes place. Owing to the interaction of ripple and the main laser beams, the ripple grows inside the plasma. The behavior of the ripple in the plasma affects the excitation of the electron plasma wave as well as the electron acceleration. The amplitude of the electron plasma wave and the electron energy are calculated, in the presence of ripple.
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Kim, Hyung Taek, Vishwa Bandhu Pathak, Calin Ioan Hojbota, Mohammad Mirzaie, Ki Hong Pae, Chul Min Kim, Jin Woo Yoon, Jae Hee Sung, and Seong Ku Lee. "Multi-GeV Laser Wakefield Electron Acceleration with PW Lasers." Applied Sciences 11, no. 13 (June 23, 2021): 5831. http://dx.doi.org/10.3390/app11135831.
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Laser wakefield electron acceleration (LWFA) is an emerging technology for the next generation of electron accelerators. As intense laser technology has rapidly developed, LWFA has overcome its limitations and has proven its possibilities to facilitate compact high-energy electron beams. Since high-power lasers reach peak power beyond petawatts (PW), LWFA has a new chance to explore the multi-GeV energy regime. In this article, we review the recent development of multi-GeV electron acceleration with PW lasers and discuss the limitations and perspectives of the LWFA with high-power lasers.
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Costes, M., C. Naulin, G. Dorthe, and Z. Moudden. "Reactive Bimolecular Collisions Studied With Combined Pulsed Lasers and Pulsed, Crossed, Supersonic Molecular Beams." Laser Chemistry 10, no. 5-6 (January 1, 1990): 367–76. http://dx.doi.org/10.1155/1990/32023.
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Pulsed, supersonic molecular beams and pulsed lasers are particularly well matched tools when combined in molecular reaction dynamics studies. Salient features of an experiment using two pulsed molecular beam sources, a pulsed ultra-violet laser for creating reactive atoms by laser ablation and a pulsed dye laser for performing laser-induced fluorescence detection of the products are described. Differences with steady-state molecular beam experiments are outlined with respect to the following points: facility of inverting the data, possibility of obtaining high signal-to-background ratios and wide ranges of collision energy. These points are illustrated with some results concerning the reactions:C(n3P)J + NO(Xπr2)→ CN(X2Σ2) + O(n3PJ),C(n3PJ) + N2O(X1Σ+) →CN(X2Σ+) + NO(Xπr2)and Mg(n1S0) + N2O(X1Σ+) →MgO(X1Σ+) + N2(X1Σg+)
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Gu, Yuan Yuan, Guo Xing Wu, Hui Lu, and Yan Cui. "High Beam Quality and High Power Diode Laser Source." Advanced Materials Research 712-715 (June 2013): 1802–6. http://dx.doi.org/10.4028/www.scientific.net/amr.712-715.1802.
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As the increasing applications of laser diodes in laser cladding and laser hardening, the single laser diode 0ptical power can not meet the actual requirements. An improvement of the power and Power densty necessary and it can be achieved by beam shaping and beam combination such as polarization coupling the polarization coupling technology is used to couple two laser beams with thin film plate polarizer In this paper two 880 nm vertical stacked arrays with an output power of l600 W was achieved After fast axils and slow axis collimated, the polarization direction of one stacked arrays is rotated 90 degree through a half wave plate, thus, the polarization directions of two laser stack are vertica1. The beams of two lasers are incident on the p1ate po1arizer, one transmits through it, and the other is reflected on it. Finally, two beams combine to one. Polarization coupling of two bars increases the power by a factor of 1.6, and the output power is 2500 W, electro optical conversion efficiency is more than 48%. The spot size is about2 mm x 2 mm. This laser can be directly applied to cladding, surface hardening and other fields.
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RENAULT, G., B. S. NIELSEN, J. WESTERGAARD, and J. J. GAARDHØJE. "THE LASER OF THE ALICE TIME PROJECTION CHAMBER." International Journal of Modern Physics E 16, no. 07n08 (August 2007): 2413–18. http://dx.doi.org/10.1142/s0218301307008021.
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The large TPC (95 m3) of the ALICE detector at the CERN LHC was commissioned in summer 2006. The first tracks were observed both from the cosmic ray muons and from the laser rays injected into the TPC. In this article the basic principles of operating the 266 nm lasers are presented, showing the installation and adjustment of the optical system and describing the control system. To generate the laser tracks, a wide laser beam is split into several hundred narrow beams by fixed micro-mirrors at stable and known positions throughout the TPC. In the drift volume, these narrow beams generate straight tracks at many angles. Here we describe the generation of the first tracks and compare them with simulations.
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Hauschwitz, Petr, Radka Bičštová, Alexander Brodsky, Natan Kaplan, Martin Cimrman, Jaroslav Huynh, Jan Brajer, et al. "Towards Rapid Fabrication of Superhydrophobic Surfaces by Multi-Beam Nanostructuring with 40,401 Beams." Nanomaterials 11, no. 8 (August 2, 2021): 1987. http://dx.doi.org/10.3390/nano11081987.
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Superhydrophobic surfaces attract a lot of attention due to many potential applications including anti-icing, anti-corrosion, self-cleaning or drag-reduction surfaces. Despite a list of attractive applications of superhydrophobic surfaces and demonstrated capability of lasers to produce them, the speed of laser micro and nanostructuring is still low with respect to many industry standards. Up-to-now, most promising multi-beam solutions can improve processing speed a hundred to a thousand times. However, productive and efficient utilization of a new generation of kW-class ultrashort pulsed lasers for precise nanostructuring requires a much higher number of beams. In this work, we introduce a unique combination of high-energy pulsed ultrashort laser system delivering up to 20 mJ at 1030 nm in 1.7 ps and novel Diffractive Laser-Induced Texturing element (DLITe) capable of producing 201 × 201 sub-beams of 5 µm in diameter on a square area of 1 mm2. Simultaneous nanostructuring with 40,401 sub-beams resulted in a matrix of microcraters covered by nanogratings and ripples with periodicity below 470 nm and 720 nm, respectively. The processed area demonstrated hydrophobic to superhydrophobic properties with a maximum contact angle of 153°.
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Lee, C. L. D., and K. C. Hewitt. "First demonstration of surface enhanced-stimulated Raman spectroscopy (SE-SRS) using low-power CW sources." Faraday Discussions 205 (2017): 227–32. http://dx.doi.org/10.1039/c7fd00137a.
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Using commercially available nanoparticles, continuous wave Surface-Enhanced Stimulated Raman spectroscopy (CW SE-SRS) is demonstrated for the first time using two Ti:Sapphire lasers producing a pump beam (785 nm, 100 mW) and appropriately varying probe/Stokes beams (860–870 nm, 120 mW). The Ti-Sapphire lasers are co-pumped by a 10 W low noise 532 nm Spectra Physics Millennia laser. Pulsed SE-SRS is also demonstrated using a Coherent Chameleon Ultra laser for the Stokes/probe (863–871 nm) beam and a Coherent Ultra II as the pump laser (785 nm). In both cases lock-in techniques are used to extract the small signal (1 in 109) successfully. These experiments convincingly demonstrate that SRS with CW sources is possible using appropriate nanoparticles, and this realization creates opportunities for a wider range of stimulated Raman spectroscopy applications.
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Davis, Harold A., Gennady E. Remnev, Regan W. Stinnett, and Kiyoshi Yatsui. "Intense Ion-Beam Treatment of Materials." MRS Bulletin 21, no. 8 (August 1996): 58–62. http://dx.doi.org/10.1557/s0883769400035739.
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Over the past decade, researchers in Japan, Russia, and the United States have been investigating the application of intense-pulsed-ion-beam (IPIB) technology (which has roots in inertial confinement fusion programs) to the surface treatment and coating of materials. The short range (0.1–10 μm) and high-energy density (1–50 J/cm2) of these short-pulsed (t ≥ 1 μs) beams (with ion currents I = 5–50 kA, and energies E = 100–1,000 keV) make them ideal flash-heat sources to rapidly vaporize or melt the near-surface layer of targets similar to the more familiar pulsed laser deposition (PLD) or laser surface treatment. The vaporized material can form coatings on substrates, and surface melting followed by rapid cooling (109 K/s) can form amorphous layers, dissolve precipitates, and form nonequilibrium microstructures.An advantage of this approach over laser processing is that these beams deliver 0.1–10 KJ per pulse to targets at expected overall electrical efficiencies (i.e., the ratio of extracted ion-beam energy to the total energy consumed in generating the beam) of 15–40% (compared to < 1% for the excimer lasers often used for similar applications). Consequently IPIB hardware can be compact and require relatively low capital investment. This opens the promise of environmentally conscious, low-cost, high-throughput manufacturing. Further, efficient beam transport to the target and excellent coupling of incident ion energy to targets are achieved, as opposed to lasers that may have limited coupling to reflective materials or produce reflecting plasmas at high incident fluence. The ion range is adjustable through selection of the ion species and kinetic energy, and the beam energy density can be tailored through control of the beam footprint at the target to melt (1–10 J/cm2) or to vaporize (10–50 J/cm2) the target surface. Beam pulse durations are short (≥ 1 μs) to minimize thermal conduction. Some disadvantages of IPIB processing over laser processing include the need to form and propagate the beams in vacuum, and the need for shielding of x-rays produced by relatively low-level electron current present in IPIB accelerators. Also these beams cannot be as tightly focused onto targets as lasers, making them unsuitable for applications requiring treatment on small spatial scales.
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GUPTA, GAGAN, and JAVED HUSAIN. "PROSPECTS OF GAMMA-RAY LASER DEVELOPMENT." Modern Physics Letters B 05, no. 14n15 (June 1991): 915–22. http://dx.doi.org/10.1142/s0217984991001143.
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In this review article we briefly present the current thrust of gamma-ray laser research. We discuss the major proposals of developing such lasers based on nuclear transitions and electron and positron beams.
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Kik, Tomasz. "Heat Source Models in Numerical Simulations of Laser Welding." Materials 13, no. 11 (June 10, 2020): 2653. http://dx.doi.org/10.3390/ma13112653.
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The article presents new possibilities for modifying heat source models in numerical simulations of laser welding processes conducted using VisualWeld (SYSWELD) software. Due to the different power distributions and shapes of a laser beams, it was necessary to propose a modification of heat source models and methods of defining the heat introduced into a welded material in the case of simulations of welding processes using solid-state and high-power diode lasers. A solution was proposed in the form of modification of predefined heat source models in the case of simulations of welding processes using solid-state disc lasers and high-power diode lasers (HPDL). Based on the results of metallographic tests and the acquisition of thermal cycles of real laser welding processes, the process of calibration and validation of the proposed models of heat sources depending on the type of device used as well as the obtained shapes of fusion beads was carried out. The purpose and assumptions of this approach towards creating heat sources were also reported, comparing exemplary stresses and cumulative plastic strain distributions for the calculation variant using a standard and modified heat source model.
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Hu, Ronghao, Zheng Gong, Jinqing Yu, Yinren Shou, Meng Lv, Zhengming Sheng, Toshiki Tajima, and Xueqing Yan. "Ultrahigh brightness attosecond electron beams from intense X-ray laser driven plasma photocathode." International Journal of Modern Physics A 34, no. 34 (December 10, 2019): 1943012. http://dx.doi.org/10.1142/s0217751x19430127.
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The emerging intense attosecond X-ray lasers can extend the Laser Wakefield Acceleration mechanism to higher plasma densities in which the acceleration gradients are greatly enhanced. Here we present simulation results of high quality electron acceleration driven by intense attosecond X-ray laser pulses in liquid methane. Ultrahigh brightness electron beams can be generated with 5-dimensional beam brightness over [Formula: see text]. The pulse duration of the electron bunch can be shorter than 20 as. Such unique electron sources can benefit research areas requiring crucial spatial and temporal resolutions.
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Badziak, J. "Laser-driven generation of fast particles." Opto-Electronics Review 15, no. 1 (January 1, 2007): 1–12. http://dx.doi.org/10.2478/s11772-006-0048-3.
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AbstractThe great progress in high-peak-power laser technology has resulted recently in the production of ps and subps laser pulses of PW powers and relativistic intensities (up to 1021 W/cm2) and has laid the basis for the construction of multi-PW lasers generating ultrarelativistic laser intensities (above 1023 W/cm2). The laser pulses of such extreme parameters make it possible to produce highly collimated beams of electrons or ions of MeV to GeV energies, of short time durations (down to subps) and of enormous currents and current densities, unattainable with conventional accelerators. Such particle beams have a potential to be applied in numerous fields of scientific research as well as in medicine and technology development. This paper is focused on laser-driven generation of fast ion beams and reviews recent progress in this field. The basic concepts and achievements in the generation of intense beams of protons, light ions, and multiply charged heavy ions are presented. Prospects for applications of laser-driven ion beams are briefly discussed.
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Haglund, Richard F. "Damage Mechanisms in Optical Materials For High-Power, Short-Wavelength Laser Systems." MRS Bulletin 11, no. 3 (June 1986): 46–47. http://dx.doi.org/10.1557/s088376940005483x.
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Damage to optical materials under intense photon irradiation has always been a major problem in the design and operation of high-energy and high-average-power lasers. In short-wavelength lasers, operating at visible and ultraviolet wavelengths, the problem appears to be especially acute; presently attainable damage thresholds seriously compromise the engineering design of laser windows and mirrors, pulsed power trains and oscillator-amplifier systems architecture. Given the present interest in ultraviolet excimer lasers and in short-pulse, high-power free-electron lasers operating at visible and shorter wavelengths, the “optical damage problem” poses a scientific and technological challenge of significantdimensions. The solution of this problem even has significant implications outside the realm of lasers, for example, in large space-borne systems (such as the Hubble Telescope) exposed to intense ultraviolet radiation.The dimensions of the problem are illustrated by the Large-Aperture krypton-fluoride laser amplifier Module (LAM) shown schematically in Figure 1. This device, now operating at the Los Alamos National Laboratory, is typical of current and planned large excimer lasers for fusion applications. The LAM has an active volume of some 2 m3, and optical surfaces (resonator mirror and windows) exceeding 1 m2 in size; the fabrication of these optical elements was the most expensive and time-consuming single item in the construction of the laser. During laser operation, a population inversion in an Ar-Kr-F2 mix ture is created through electron-beam excitation of the laser gas by two 400 kA beams of 650 keV electrons from a cold cathode discharge. The electron trajectories in the gas are constrained by a 4 kG magnetic field transverse to the optical axis produced by a pair of large Helmholtzcoils.
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RUS, B., K. ROHLENA, J. SKÁLA, B. KRÁLIKOVÁ, K. JUNGWIRTH, J. ULLSCHMIED, K. J. WITTE, and H. BAUMHACKER. "New high-power laser facility PALS—prospects for laser–plasma research." Laser and Particle Beams 17, no. 2 (April 1999): 179–94. http://dx.doi.org/10.1017/s0263034699172045.
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In this paper, we report on a new laser facility called PALS (Prague Asterix Laser System), which is currently under construction, and which will house the high-power iodine laser Asterix IV. Upon its completion in late 1999, the PALS facility will be capable of providing single- or multiple-pulse irradiation with a variable pulse duration ranging from 100 to 500 ps. Wavelengths available will be 1.315 μm, 658 nm, and 438 nm. The system will provide one main beam with energy up to 1200 J and two smaller auxiliary beams with a combined energy of up to 100 J. A wide variety of geometries and variable pulse timings is available. We assess PALS' potential for investigating the physics of laser plasmas in inertial confinement fusion, the development and applications of X-ray lasers, X-ray spectroscopy, and radiation transport, using multiple-pulse and extended beam capability.
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PANCHENKO, A. N., V. M. ORLOVSKII, and V. F. TARASENKO. "Efficient e-beam and discharge initiated nonchain HF(DF) lasers." Laser and Particle Beams 21, no. 2 (April 2003): 223–32. http://dx.doi.org/10.1017/s0263034603212106.
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The spectral and amplitude-temporal parameters of HF (DF) lasers pumped by nonchain chemical reactions initiated by radially convergent or planar e-beams and self-sustained discharge were studied. Intrinsic efficiency of the HF lasers up to ∼10% was obtained for both excitation methods. It was shown that the high efficiency of an e-beam-initiated HF laser may be attained as a result of the simultaneous formation of atomic and molecular fluorine and of the participation of F2 in population inversion. A laser pulse has a complex profile caused by the successive generation of P-lines and the overlap during the radiation pulse of both the rotational lines of the same vibration band and of individual vibration bands. Experimental conditions providing high intrinsic efficiency of a discharge nonchain HF (DF) laser are determined. Intrinsic efficiency of HF and DF lasers up to ηin ∼ 10% and 7%, respectively, is obtained using excitation by inductive and LC generators in the SF6-H2 (D2) mixtures. High discharge uniformity obtained with the use of special shaped electrodes along with uniform UV preionization is a key parameter for improving the intrinsic efficiency of discharge HF (DF) lasers. It was found that in this excitation condition, output spectra of the HF laser significantly widen and cascade laser action on some rotational lines of the vibrational transitions of HF molecules ν(3–2) → ν(2–1) → ν(1–0) is observed. This can explain the high intrinsic efficiency obtained. Specific output of the discharge HF laser over 8 J/L (140 J/L×atm) and total laser efficiency ηt ∼ 4.5% were achieved. For the discharge DF laser, specific output and total efficiency were as high as 6.5 J/L and 3.2%, respectively.
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Karelin, A. V., S. I. Yakovlenko, V. F. Tarasenko, and A. F. Fedenev. "High-pressure He-Cd and He-Zn lasers pumped by a hard ionizer." Laser and Particle Beams 13, no. 1 (March 1995): 111–28. http://dx.doi.org/10.1017/s0263034600008880.
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This paper presents the results of theoretical and experimental studies on high-pressure He-Cd and He-Zn lasers. It is shown that using the hard ionizer approximation makes it possible to readily and efficiently simulate the plasma chemical processes that occur in the active media of high-pressure lasers pumped by electron and ion beams as well as by nuclear reaction products in electron-beam experiments. Laser oscillation was achieved at λ = 325, 441.6, 533.7, and 537.8 nm for the cadmium ion and at λ = 610.3 nm for the zinc ion.
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Modest, M. F., and H. Abakians. "Heat Conduction in a Moving Semi-infinite Solid Subjected to Pulsed Laser Irradiation." Journal of Heat Transfer 108, no. 3 (August 1, 1986): 597–601. http://dx.doi.org/10.1115/1.3246977.
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Heat conduction in a moving semi-infinite medium subject to laser irradiation is considered. The body of knowledge of exact analytical solutions for Gaussian laser irradiation is expanded to include pulsed lasers, and laser beams that penetrate into the medium with exponential decay. For applications with complicated geometries (laser melting and evaporation), a simple integral method, based on one-dimensional diffusion, is presented, and its range of validity determined.
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London, R. A., N. M. Ceglio, D. C. Eder, A. U. Hazi, C. J. Keane, B. J. Macgowan, D. L. Matthews, et al. "The Soft X-Ray Laser Program at Livermore." International Astronomical Union Colloquium 102 (1988): 221. http://dx.doi.org/10.1017/s0252921100107754.
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AbstractWe describe the experiments and supporting theoretical modelling to develop and characterize soft x-ray lasers. The x-ray lasers are created in dense plasmas produced by optical laser irradiation of solid targets with line focussed beams. We use mainly thin foil targets, which upon appropriate illumination, produce rather uniform plasmas. We consider laser schemes pumped by electron collisional excitation and dielectronic recombination in Ne-like and Ni-like ions, and schemes pumped by collisional and radiative recombination following rapid cooling for H-like and Li-like ions.Experimental measurements of the time and space resolved spectra taken both along the lasing axis and at other viewing angles, in addition to data on the angular pattern of x-ray laser radiation and on the absorption and scattering of the optical laser light are presented. These data allow us the determine the characteristics of the plasmas which have been created, as well as the properties of the x-ray lasers, such as the gain coefficients for the inverted transitions, and their spatial and temporal distributions. The modelling includes calculations of the absorption of the optical laser light, the hearing and hydrodynamics of the targets and the evolution of the atomic level populations within the plasma. Transfer of the emitted radiation is calculated, including resonance line trapping, amplification for inverted transitions, and refraction of the x-ray laser beam due to electron density gradients. Results are used to optimize x-ray laser designs before the experiments and to interpret the measured spectra.The latest experimental results from the NOVA laser facility on the performance of several laser schemes and on the use of multilayer mirrors to produce x-ray laser cavities are reported. These results arc compared to the models to test and improve our understanding of the complex physics involved in making x-ray lasers. Based on current experiments, we show how the modelling can be use to design shorter wavelength and more efficient schemes for use in applications such as x-ray holography.
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Cheng, Yong, Shu Yun Wang, Yi Min Lu, Guo Jun Huang, Yan Long Guo, Xu Liu, and Bin Sun. "Research of Diamond-Like Carbon Film Deposited by Double Pulsed Lasers." Advances in Science and Technology 95 (October 2014): 11–16. http://dx.doi.org/10.4028/www.scientific.net/ast.95.11.
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In the research of Diamond-like carbon (DLC) Film deposited by pulsed laser, method of double pulsed laser deposition was presented. Ti:Sapphire (800nm, 120fs) laser and KrF (248nm, 20ns) laser were used orderly to ablate graphite target. Through controlling parameters of two laser beams, double-layer DLC film was deposited on silicon substrate. The hardness and inner-stress of the DLC film changed gradually from substrate to atmosphere-interface. Nanoindentation measurement system and fourier transfer infrared spectrograph were used to hardness and transmittance of the film. Meanwhile, adhesive tape, 9.8N rubber, NaOH liquor and boiling water were used to compare the adhesion and environment adaptability of double layer or monolayer DLC film samples qualitatively. Results showed that DLC film deposited by double beam pulsed laser not only had high transmittance and hardness, but also kept well and had no phenomenon of peeling off after the tests including dipped in boiled water, etc. Compared to DLC films deposited by single pulsed laser, the chemical and thermal inertness of the double-layer DLC film deposited by double pulsed lasers was much better.
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Millán-Callado, M. A., C. Guerrero, J. M. Quesada, J. Gómez, B. Fernández, J. Lerendegui-Marco, T. Rodríguez-González, et al. "Laser-driven neutrons for time-of-flight experiments?" EPJ Web of Conferences 239 (2020): 17012. http://dx.doi.org/10.1051/epjconf/202023917012.
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Neutron beams, both pulsed and continuous, are a powerful tool in a wide variety of research fields and applications. Nowadays, pulsed neutron beams are produced in conventional accelerator facilities in which the time-of-fight technique is used to determine the kinetic energy of the neutrons inducing the reactions of interest. In the last decades, the development of ultra-short (femtosecond) and ultra-high power (> 1018 W/cm2) lasers has opened the door to a vast number of new applications, including the production and acceleration of pulsed ion beams. These have been recently used to produce pulsed neutron beams, reaching fluxes per pulse similar and even higher than those of conventional neutron beams, hence becoming an alternative for the pulsed neutron beam users community. Nevertheless, these laser-driven neutrons have not been exploited in nuclear physics experiments so far. Our main goal is to produce and characterize laser-driven neutrons but optimizing the analysis, diagnostic and detection techniques currently used in conventional neutron sources to implement them in this new environment. As a result, we would lay down the viability of carrying out nuclear physics experiments using this kind of sources by identifying the advantages and limitations of this production method. To achieve this purpose, we plan to perform experiments in both medium (50TW@L2A2, in Santiago de Com-postela) and high (1PW@APOLLON, in Paris) power laser facilities.
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Földes, I. B., and S. Szatmári. "On the use of KrF lasers for fast ignition." Laser and Particle Beams 26, no. 4 (September 18, 2008): 575–82. http://dx.doi.org/10.1017/s026303460800061x.
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AbstractThe KrF laser has been considered as an inertial fusion driver alternative to diode-pumped lasers. The possibilities of KrF lasers for fast ignition is supported by their short wavelength and the corresponding larger penetration depth together with the possible use of the same amplifiers for fusion driver and fast ignitor. It is shown that in the case of a fusion test facility both the energy and the intensity requirements can be fulfilled. A fast ignitor using 20 ps KrF pulses requires beam smoothing techniques after angular multiplexing due to the coherence of the beam. A multiple beam fast ignitor is suggested as an alternative in which a high number of beams of 1 ps duration are separately focused on the fuel after polarization demultiplexing. This arrangement allows even the pulse-forming of the ignitor.
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Wieser, J., A. Ulrich, B. Busch, R. Gernhäuser, W. Krötz, G. Ribitzki, M. Salvermoser, and D. E. Murnick. "Heavy-ion beam-pumped lasers: Optical gain on the 476.5-nm Ar II transition." Laser and Particle Beams 11, no. 3 (September 1993): 529–35. http://dx.doi.org/10.1017/s0263034600005188.
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The possibility of heavy-ion beam-pumped ion lasers is demonstrated by observation of optical gain on the 476.5-nm Ar II 4p–4s ion laser transition in argon gas excited by 2.5–ns pulses of 110–MeV 32S ions with repetition rates up to 156 kHz. The particle energy per pulse was about 20 μJ. The projectiles were stopped in the target at pressures between 5 and 35 kPa. The beam from an argon ion probe laser operated at 476.5 nm was used to determine gain amplitude and time structure from a measured transient increase of the probe laser intensity when target excitation by the ion beam was present. The maximum gain observed was (0.5 ± 0.1) x 10-3 at a target gas pressure of 5 kPa. The optical gain observed in argon is consistent with calculations based upon an analysis of spectroscopic studies of rare gas targets excited by heavy-ion beams.
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Osman, Frederick. "Guest Editor's Preface: Workshop on Fast High Density Plasma Blocks Driven By Picosecond Terawatt Lasers." Laser and Particle Beams 23, no. 4 (October 2005): 399–400. http://dx.doi.org/10.1017/s0263034605050561.
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This issue of Laser and Particle Beams includes papers presented at the Workshop on “Fast High Density Plasma Blocks Driven by Picosecond Terawatt Lasers” held at the University of Western Sydney, Campbelltown Campus, Australia from 1–4 December 2004.
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Bonatto, Alexandre, Roger Pizzato Nunes, Bruno Silveira Nunes, Sanjeev Kumar, Linbo Liang, and Guoxing Xia. "An Active Plasma Beam Dump for EuPRAXIA Beams." Instruments 5, no. 3 (July 5, 2021): 24. http://dx.doi.org/10.3390/instruments5030024.
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Plasma wakefields driven by high power lasers or relativistic particle beams can be orders of magnitude larger than the fields produced in conventional accelerating structures. Since the plasma wakefield is composed not only of accelerating but also of decelerating phases, this paper proposes to utilize the strong decelerating field induced by a laser pulse in the plasma to absorb the beam energy, in a scheme known as the active plasma beam dump. The design of this active plasma beam dump has considered the beam output by the EuPRAXIA facility. Analytical estimates were obtained, and compared with particle-in-cell simulations. The obtained results indicate that this active plasma beam dump can contribute for more compact, safer, and greener accelerators in the near future.
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Saghafi, S., M. J. Withford, and J. A. Piper. "Propagation of laser beams formed by unstable resonators with different magnifications." Canadian Journal of Physics 84, no. 3 (March 1, 2006): 241–52. http://dx.doi.org/10.1139/p06-013.
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Laser beams generated from high-magnification on-axis unstable resonators using hard-edged axial scraper mirrors and output couplers consisting of axial spot reflectors typically have an annular distribution in the near field (i.e., a flat-top profile with a hole in the middle for an axially coupled beam). We employ a new model, based on the flattened Gaussian beam (FGB) concept, to describe the propagation of such annular near-field beams. The superposition of two FGBs, whose flatness and steepness of edges are controlled by defined parameters (i.e., the beam width and the order), is used to analyze the output beam intensity profile along the propagation axis. We apply this model to characterize the output beams of copper vapour lasers employing unstable resonators of different magnifications (M = 80, 200, and 400). We show that once the model is fitted to the beam intensity profile at any two positions along the axis of propagation, it can be used to predict the beam shape at any position.PACS Nos.: 42.55.–f, 42.55.Lt, 42.60.–v
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Sreckovic, Milesa Ž., Branka Kaludjerovic, Aleksander G. Kovacevic, Aleksandar Bugarinovic, and Dragan Družijanic. "Interaction of laser beams with carbon textile materials." International Journal of Clothing Science and Technology 27, no. 5 (September 7, 2015): 720–37. http://dx.doi.org/10.1108/ijcst-07-2014-0086.
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Purpose – The purpose of this paper is to present the results of interaction occurring during the exposition of some specific carbon textile materials obtained in laboratory conditions to beams of various laser types. Design/methodology/approach – Carbon fabric materials – fiber, felt and cloth – obtained from different precursor materials and prepared at various process conditions (oxidized, partially carbonized, carbonized, graphitized), were exposed to pulses of various lasers (Nd3+: YAG, alexandrite, ruby). Findings – Depending on the laser power, plasma and destructive phenomena occurred. In the case of an interaction between a Nd3+: YAG laser beam and specimens of thickness in millimeter range, the authors have estimated the threshold of the energy density for drilling and discussed the possible models of the interaction. Research limitations/implications – The results have implications in the estimations of quality as well as in the improvement of material processing, giving some new light to the changes of mechanical and optical constants of the material, as well as to the changes of carbon groups of the material, which would be useful for different types of modeling. Future research will be in the interaction of laser beams with various textile materials, where the investigation would cover the microstructure changes and the implications on cloth cutting and welding, concerning the damages as well as relief structures, specially renew for fs laser regimes. Originality/value – The area of laser applications in the textile industry is supported by scientific and applicative exploration. However, fewer results are concerned with deep introspection into the microstructure of the damages considering the laser interaction with carbon fiber and other carbon-based textiles.
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Swayambunathan, Vaidhianat, Rosario C. Sausa, and Gurbax Singh. "Investigations into Trace Detection of Nitrocompounds by One- and Two-Color Laser Photofragmentation/Fragment Detection Spectrometry." Applied Spectroscopy 54, no. 5 (May 2000): 651–58. http://dx.doi.org/10.1366/0003702001950111.
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Trace concentrations of nitrogen dioxide (NO2), nitromethane (CH3NO2), and 2,4,6-trinitrotoluene (TNT) are detected by both one- and two-color laser photofragmentation/fragment detection (PF/FD) spectrometry using one or two lasers. The PF/FD methods studied are (1) one-laser, one-color photofragmentation of the analyte molecule at 227 or 454 nm with subsequent detection of the characteristic nitric oxide (NO) photofragment by one- or two-photon laser-induced fluorescence using its A2Σ+ –X2π (0,0) transitions near 227 nm; (2) one-laser, two-color PF/FD, where a 355 nm laser beam is used for additional analyte photofragmentation and NO is detected by both one- and two-photon LIF as in the previous case; (3) two-laser, two-color PF/FD, where the pump and probe beams are time delayed; and (4) one-laser, one-color PF/FD at 355 nm, where the 355 nm beam photofragments the target molecule and the prompt emission from electronically excited NO (A2Σ+) is monitored in the range of 200–300 nm. PF/FD excitation and emission spectra are recorded and also simulated with the use of a computer program based on a Boltzmann distribution analysis with transition probabilities, rotational energies, and rovibrational temperatures as input parameters. The effects of laser wavelength, laser pump energy, time delay between pump and probe beams, and analyte concentration on PF/FD signal are investigated and reported. Limits of detection [signal-to-noise (S/N) = 3] for the nitrocompounds range from low ppbv to ppmv for 10 s integration time and laser energies of ∼ 5 mJ and 100 μJ for the pump and probe beams, respectively. These results are presented and compared to other PF/FD methods for nitrocompound monitoring.
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Srinivasa Rao, A. "Equations for beam waist measurement of high peak power lasers." Journal of Nonlinear Optical Physics & Materials 28, no. 02 (June 2019): 1950020. http://dx.doi.org/10.1142/s0218863519500206.
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We have derived a set of equations for beam waist at lens focus as a function of variable spot size and demonstrated their physical validity. The derived equations are useful for the estimation of the beam waist size of high peak power lasers focused with high numerical aperture lenses and for spot size measurement of long-range collimated Gaussian beams for several meters. We have described an indirect method to estimate the high peak power focused laser beam waist. The same treatment is extended to the Gaussian vortex beam for estimating its parameters at the beam waist. These results can be useful in the focused Gaussian beam and Gaussian vortex beam applications.
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Wang, Xuewen, Zhongquan Nie, Yao Liang, Jian Wang, Tao Li, and Baohua Jia. "Recent advances on optical vortex generation." Nanophotonics 7, no. 9 (August 29, 2018): 1533–56. http://dx.doi.org/10.1515/nanoph-2018-0072.
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AbstractThis article reviews recent progress leading to the generation of optical vortex beams. After introducing the basics of optical vortex beams and their promising applications, we summarized different approaches for optical vortex generation by discrete components and laser cavities. We place particular emphasis on the recent development of vortex generation by the planar phase plates, which are able to engineer a spiral phasefront via dynamic or geometric phase in nanoscale, and highlight the independent operation of these two different phases which leads to a multifunctional optical vortex beam generation and independent spin-orbit interaction. We also introduced the recent progress on vortex lasing, including vortex beam generation from the output of bulk lasers by modification of conventional laser cavities with phase elements and from integrated on-chip microlasers. Similar approaches are also applied to generate fractional vortex beams carrying fractional topological charge. The advanced technology and approaches on design and nanofabrications enable multiple vortex beams generation from a single device via multiplexing, multicasting, and vortex array, open up opportunities for applications on data processing, information encoding/decoding, communication and parallel data processing, and micromanipulations.
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Wisniewski, Denis Alexander, and Mark Prelas. "Transport model for a transverse electron beam-pumped semiconductor laser." Laser and Particle Beams 37, no. 4 (November 20, 2019): 392–99. http://dx.doi.org/10.1017/s0263034619000582.
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AbstractA transport model for a transverse electron beam-pumped semiconductor laser has been developed. The model incorporates spatial dependencies of the power deposition from the beam as well as a three-dimensional model of the gain medium and the field intensity of the photons produced by stimulated emission in the oscillation cavity. This model accounts for spatial inhomogeneities and has been solved for a variety of pumping strengths. The model was developed so that it can be benchmarked with electron beam pumping. The dominant mechanisms for the production of electron–hole pair production within the semiconductor material is similar to the dominant mechanisms for the production of electron–hole production using ion beams. Thus, the model can be extended to fission fragment ion pumping of semiconductor lasers in order to model a nuclear-pumped laser/reactor system.
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Matic, Milan, Bogosav Lazetic, Mirjana Poljacki, Verica Djuran, and Milana Ivkov-Simic. "Low level laser therapy and its effects on reparatory processes of the skin." Medical review 56, no. 3-4 (2003): 137–41. http://dx.doi.org/10.2298/mpns0304137m.
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Introduction Application of laser beams for therapeutic purposes is of relatively recent date, but today there is no field of medicine where lasers cannot be used. Physical characteristics of laser radiation Laser radiation is a type of electromagnetic radiation with some specific characteristics such as coherence, monochromaticity and parallelity. Types of laser devices Nowadays, there are many laser devices on the market used in medicine and dentistry. According to the type of their active medium, lasers can be classified as solid, gas, semiconductor and liquid. Effects of low level laser therapy on biological systems The exact mechanism of action of low level laser therapy is still not completely understood. Its basic feature is to modulate cell behaviour, without causing significant temperature increase. During irradiation of a tissue with a laser beam, an interaction between cells and photons takes place - photochemical reaction. After a cell absorbs the photon, the photon stops existing, and its energy is incorporated into the molecule which has absorbed it. Once this energy is transferred to different bio-molecules, it can be transferred to other molecules as well. The energy transferred to the molecule can increase its kinetic energy, and activate or deactivate enzymes or alter physical or chemical properties of main macromolecules. Effects of low level laser therapy on wound healing Effects of low level laser therapy on wound healing process is one of the most fully studied aspects of this type of therapy. It affects all phases of this very complex process. This paper offers a more detailed analysis of these aspects.
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Kline, J. L., D. S. Montgomery, C. Rousseaux, S. D. Baton, V. Tassin, R. A. Hardin, K. A. Flippo, et al. "Investigation of stimulated Raman scattering using a short-pulse diffraction limited laser beam near the instability threshold." Laser and Particle Beams 27, no. 1 (February 18, 2009): 185–90. http://dx.doi.org/10.1017/s0263034609000251.
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AbstractShort pulse laser plasma interaction experiments using diffraction limited beams provide an excellent platform to investigate the fundamental physics of stimulated Raman scattering. Detailed understanding of these laser plasma instabilities impacts the current inertial confinement fusion ignition designs and could potentially impact fast ignition when higher energy lasers are used with longer pulse durations (>1 kJ and >1 ps). Using short laser pulses, experiments can be modeled over the entire interaction time of the laser using particle-in-cell codes to validate our understanding quantitatively. Experiments have been conducted at the Trident laser facility and the Laboratoire pour l'Utilisation des Lasers Intenses (LULI) to investigate stimulated Raman scattering near the threshold of the instability using 527 nm and 1059 nm laser light, respectively, with 1.5–3.0 ps pulses. In both experiments, the interaction beam was focused into pre-ionized helium gas-jet plasma. Measurements of the reflectivity as a function of intensity and kλD were completed at the Trident laser facility, where k is the electron plasma wave number and λD is the plasma Debye length. At LULI, a 300 fs Thomson scattering probe is used to directly measure the density fluctuations of the driven electron plasma and ion acoustic waves. Work is currently underway comparing the results of the experiments with simulations using the VPIC particle-in-cell code. Details of the experimental results are presented in this manuscript.
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Fiorini, F., D. Neely, R. J. Clarke, and S. Green. "Characterization of laser-driven electron and photon beams using the Monte Carlo code FLUKA." Laser and Particle Beams 32, no. 2 (February 19, 2014): 233–41. http://dx.doi.org/10.1017/s0263034614000044.
Full textAbstract:
AbstractWe present a new simulation method to predict the maximum possible yield of X-rays produced by electron beams accelerated by petawatt lasers irradiating thick solid targets. The novelty of the method lies in the simulation of the electron refiluxing inside the target implemented with the Monte Carlo code Fluka. The mechanism uses initial theoretical electron spectra, cold targets and refiluxing electrons forced to re-enter the target iteratively. Collective beam plasma effects are not implemented in the simulation. Considering the maximum X-ray yield obtained for a given target thickness and material, the relationship between the irradiated target mass thickness and the initial electron temperature is determined, as well as the effect of the refiluxing on X-ray yield. The presented study helps to understand which electron temperature should be produced in order to generate a particular X-ray beam. Several applications, including medical and security imaging, could benefit from laser generated X-ray beams, so an understanding of the material and the thickness maximizing the yields or producing particular spectral characteristics is necessary. On the other more immediate hand, if this study is experimentally reproduced at the beginning of an experiment in which there is an interest in laser-driven electron and/or photon beams, it can be used to check that the electron temperature is as expected according to the laser parameters.