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1
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 und 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, Nr. 6 (2022): 20220055. http://dx.doi.org/10.3788/irla20220055.
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Xu, Dong, Yao Yao, Xing Fu und Chao Wang. „Design of Micromachining System Based on Nanosecond Pulsed Laser“. Key Engineering Materials 645-646 (Mai 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, und Rajni Kumar. „Design and Development of a Laser Warning Sensor Prototype for Airborne Application“. Defence Science Journal 73, Nr. 3 (12.05.2023): 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 und FRANK TRÄGER. „PREPARATION OF GOLD NANOPARTICLES WITH NARROW SIZE DISTRIBUTIONS AND WELL DEFINED SHAPES“. International Journal of Modern Physics B 19, Nr. 15n17 (10.07.2005): 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 und A. MIGUS. „LULI activities in the field of high-power laser–matter interaction“. Laser and Particle Beams 17, Nr. 2 (April 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 und 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, Nr. 2 (07.01.2022): 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 und 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 und Fengping Li. „Simulation Analysis of Nanosecond Laser Processing of Titanium Alloy Based on Helical Trepanning“. Applied Sciences 12, Nr. 18 (08.09.2022): 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 und Michael O. Thompson. „Pulsed-laser induced transient phase transformations at the Si–H2O interface“. Journal of Materials Research 4, Nr. 4 (August 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 und Guanghua Cheng. „Design and Fabrication of Dual-Scale Broadband Antireflective Structures on Metal Surfaces by Using Nanosecond and Femtosecond Lasers“. Micromachines 11, Nr. 1 (24.12.2019): 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.
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HORA, HEINRICH. „Smoothing and stochastic pulsation at high power laser-plasma interaction“. Laser and Particle Beams 24, Nr. 3 (September 2006): 455–63. http://dx.doi.org/10.1017/s0263034606060617.
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Stochastic pulsation of laser-plasma interaction in the range of a few to dozens of picoseconds, due to standing wave produced density ripples, needs more attention than in the past, in view of the recent developments. This is important if nanosecond laser pulses produce a pre-compression that is a thousand times the solid state density of DT for fast ignition as well as for treatment of ps laser interaction. The following is an updated summary of these properties where the laser beam smoothing is essential. The use of smoothing is not only an empirical game with experiments for improving the interaction, but it is necessary to be aware of the mechanisms involved for understanding how the pulsation is overcome, and conclusions can be derived systematically for further improvements and control of the phenomena.
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Sui, Yuan, Mingheng Yuan, Zhenao Bai und Zhongwei Fan. „Recent Development of High-Energy Short-Pulse Lasers with Cryogenically Cooled Yb:YAG“. Applied Sciences 12, Nr. 8 (07.04.2022): 3711. http://dx.doi.org/10.3390/app12083711.
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High-power solid-state lasers are among the hot research directions at the forefront of laser research and have major applications in industrial processing, laser-confined nuclear fusion, and high-energy particle sources. In this paper, the properties of Yb:YAG and Nd:YAG crystals as gain media for high-power solid-state lasers were briefly compared, according to the results of which Yb:YAG crystals are more suitable for high-power applications. Then, the effects of the thermodynamic and spectral properties of Yb:YAG crystals with temperature were analyzed in detail, and it was shown that the laser beams amplified by the cryogenically cooled Yb:YAG crystals could have higher beam quality, higher pump absorption efficiency, lower pump threshold, and higher gain. The change in properties of Yb:YAG crystal at low temperature makes it more suitable as a gain medium for high-power lasers. Subsequently, two types of kilowatt-class lasers using cryogenically cooled Yb:YAG crystals as gain media are introduced—100 J, 10 Hz nanosecond lasers and 1 J, 1 kHz picosecond lasers. Their configuration, main parameters, and typical output results were analyzed. Finally, future directions in the development of cryogenically cooled Yb:YAG lasers are discussed.
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Song, Peng, Junyan Liu, Zhijie Li, Siyuan Wu, Xiaogang Sun, Honghao Yue und Michal Pawlak. „All-optical laser ultrasonic technique for imaging of subsurface defects in carbon fiber reinforced polymer (CFRP) using an optical microphone“. Journal of Applied Physics 131, Nr. 16 (28.04.2022): 165106. http://dx.doi.org/10.1063/5.0087304.
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Defects, such as delamination and debonding, are critical to the performance of carbon fiber-reinforced polymer (CFRP) composites. In recent years, non-destructive testing techniques have been improved for the inspection of these defects among CFRPs. In this study, an all-optical and non-destructive laser ultrasonic technique with an optical microphone detection module has been presented to detect the artificial subsurface defects among the CFRP composites. A finite element simulation based on the thermo-mechanical coupling model was used to study the process of nanosecond pulsed laser excitation of the CFRP laminate to produce ultrasound and the propagation behavior of ultrasound among the CFRP laminate. A series of non-contact laser ultrasonic testing experiments were carried out to study the flat bottom holes of different sizes via a laser ultrasonic detection system. The artificial subsurface defects were reliably identified by the presented all-optical laser ultrasonic system imbedded in the optical microphone using four feature images.
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Zheng, Shuo, Walter W. Duley, Peng Peng und Norman Zhou. „Laser modification of Au–CuO–Au structures for improved electrical and electro-optical properties“. Nanotechnology 33, Nr. 24 (25.03.2022): 245205. http://dx.doi.org/10.1088/1361-6528/ac5b52.
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Abstract CuO nanomaterials are one of the metal-oxides that received extensive investigations in recent years due to their versatility for applications in high-performance nano-devices. Tailoring the device performance through the engineering of properties in the CuO nanomaterials thus attracted lots of effort. In this paper, we show that nanosecond (ns) laser irradiation is effective in improving the electrical and optoelectrical properties in the copper oxide nanowires (CuO NWs). We find that ns laser irradiation can achieve joining between CuO NWs and interdigital gold electrodes. Meanwhile, the concentration and type of point defects in CuO can be controlled by ns laser irradiation as well. An increase in the concentration of defect centers, together with a reduction in the potential energy barrier at the Au/CuO interfaces due to laser irradiation increases electrical conductivity and enhances photo-conductivity. We demonstrate that the enhanced electrical and photo-conductivity achieved through ns laser irradiation can be beneficial for applications such as resistive switching and photo-detection.
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Holzwarth, Alfred R. „Applications of ultrafast laser spectroscopy for the study of biological systems“. Quarterly Reviews of Biophysics 22, Nr. 3 (August 1989): 239–326. http://dx.doi.org/10.1017/s0033583500002985.
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The discovery of mode-locked laser operation now nearly two decades ago has started a development which enables researchers to probe the dynamics of ultrafast physical and chemical processes at the molecular level on shorter and shorter time scales. Naturally the first applications were in the fields of photophysics and photochemistry where it was then possible for the first time to probe electronic and vibrational relaxation processes on a sub-nanosecond timescale. The development went from lasers producing pulses of many picoseconds to the shortest pulses which are at present just a few femtoseconds long. Soon after their discovery ultrashort pulses were applied also to biological systems which has revealed a wealth of information contributing to our understanding of a broadrange of biological processes on the molecular level.It is the aim of this review to discuss the recent advances and point out some future trends in the study of ultrafast processes in biological systems using laser techniques. The emphasis will be mainly on new results obtained during the last 5 or 6 years. The term ultrafast means that I shall restrict myself to sub-nanosecond processes with a few exceptions.
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Grivickas, P., R. A. Austin, M. R. Armstrong, H. B. Radousky und J. L. Belof. „Phase transitions in Zr at sub-nanosecond time scales“. Journal of Applied Physics 131, Nr. 8 (28.02.2022): 085902. http://dx.doi.org/10.1063/5.0080508.
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Solid-solid phase transitions are investigated in Zr thin films using shock compression induced by a short laser pulse (<1 ns). Shock wave profiles are measured at free surfaces for films of different thicknesses (a few micrometers) using chirped-pulse line velocimetry with 10 ps time resolution. Experiments are performed at pressures up to ∼50 GPa, which is sufficient to reach the ω and β phases under equilibrium conditions. The shock wave structures are analyzed using a general Lagrangian analysis method, which allows for the calculation of stress–strain paths and assessments of phase transition behavior. In agreement with recent short laser pulse experiments using ultra-fast x-ray diffraction, we do not find any clear evidence of the α–ω transition, though this would be expected from the phase diagram. Instead, we infer a direct transformation to a metastable β-phase at lower shock pressures (<20 GPa) and equilibrium β at higher pressures. Through the velocimetry analysis, we find α–β transformation onset times of less than ∼100 ps and completion times of less than ∼200 ps.
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Cui, Jianlei, Xuyang Fang, Xiangyang Dong, Xuesong Mei, Kaida Xu, Zhengjie Fan, Zheng Sun und Wenjun Wang. „Fabrication of PCD Skiving Cutter by UV Nanosecond Laser“. Materials 14, Nr. 14 (19.07.2021): 4027. http://dx.doi.org/10.3390/ma14144027.
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Polycrystalline diamond (PCD) skiving cutter has dominated research in recent years. However, the traditional methods of fabrication have failed to cut the diamond with high quality. We propose the two-step laser machining process combining roughing machining with orthogonal irradiation and finishing machining with tangential irradiation. In addition, the processing effect and mechanism of different lasers on the diamond were investigated by a finite element analysis. It’s proved that the ultraviolet nanosecond laser is an excellent machining method for the processing of diamond. Furthermore, the effect of the processing parameters on the contour accuracy (Rt) was studied. The result indicates that the Rt value decreases first and then increases as the increase of the line interval, scanning speed and defocusing amount (no matter positive or negative defocus). Further, Raman spectroscopy was applied to characterize the diamond surface under different cutting methods and the flank face of the tool after processing. Finally, a high-quality PCD skiving cutter was obtained with an Rt of 5.6 µm and no phase transition damage.
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Chin, Kok Chung, Amarsinh Gohel, Hendry Izaac Elim, Weizhe Chen, Wei Ji, Ghee Lee Chong, Chorng Haur Sow und Andrew T. S. Wee. „Modified carbon nanotubes as broadband optical limiting nanomaterials“. Journal of Materials Research 21, Nr. 11 (November 2006): 2758–66. http://dx.doi.org/10.1557/jmr.2006.0338.
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Carbon nanotubes have been shown to be effective broadband optical limiters for nanosecond laser pulses. In this paper, we review the recent developments of carbon nanotube-based optical limiters, in particular the effects of modifying carbon nanotubes for device applications. The techniques used to modify carbon nanotubes mainly include thin film coating, doping, and blending with optical absorbing dye. These modifications can greatly enhance the optical limiting performance of carbon nanotubes, with the goal of fabricating an optimal optical limiter system.
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Oberdorfer, Christian, Patrick Stender, Christoph Reinke und Guido Schmitz. „Laser-Assisted Atom Probe Tomography of Oxide Materials“. Microscopy and Microanalysis 13, Nr. 5 (11.04.2007): 342–46. http://dx.doi.org/10.1017/s1431927607070274.
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Atom probe tomography provides a chemical analysis of nanostructured materials with outstanding resolution. However, due to the process of field evaporation triggered by nanosecond high voltage pulses, the method is usually limited to conductive materials. As part of recent efforts to overcome this limitation, it is demonstrated that the analysis of thick NiO and WO3 oxide layers is possible by laser pulses of 500 ps duration. A careful analysis of the mass spectra demonstrates that the expected stoichiometries are well reproduced by the measurement. The reconstruction of lattice planes proves that surface diffusion is negligible also in the case of thermal pulses.
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Gurentsov, Evgeny Valerievich. „A review on determining the refractive index function, thermal accommodation coefficient and evaporation temperature of light-absorbing nanoparticles suspended in the gas phase using the laser-induced incandescence“. Nanotechnology Reviews 7, Nr. 6 (19.12.2018): 583–604. http://dx.doi.org/10.1515/ntrev-2018-0080.
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AbstractIn this review, the possibility of using pulsed, nanosecond laser heating of nanoparticles (NPs) is demonstrated, in order to investigate their thermo-physical properties. This approach is possible because the laser heating produces high NP temperatures that facilitate the observation of their thermal radiation (incandescence). This incandescence depends on the thermo-physical properties of the NPs, such as heat capacity, density, particle size, volume fraction and the refractive index of the particle material, as well as on the heat-mass transfer between the NPs and the surrounding gas media. Thus, the incandescence signal carries information about these properties, which can be extracted by signal analyses. This pulsed laser heating approach is referred to as laser-induced incandescence. Here, we apply this approach to investigate the properties of carbon, metal and carbon-encapsulated Fe NPs. In this review, the recent results of the measurements of the NP refractive index function, thermal energy accommodation coefficient of the NP surface with bath gas molecules and the NP evaporation temperature obtained using laser-induced incandescence are presented and discussed.
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Kuramitsu, Yasuhiro, Yosuke Matsumoto und Takanobu Amano. „Nonlinear evolution of the Weibel instability with relativistic laser pulses“. Physics of Plasmas 30, Nr. 3 (März 2023): 032109. http://dx.doi.org/10.1063/5.0138855.
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The Weibel instability is investigated using relativistic intense short laser pulses. A relativistic short laser pulse can generate a sub-relativistic high-density collisionless plasma. By irradiating double parallel planar targets with two relativistic laser pulses, sub-relativistic collisionless counterstreaming plasmas are created. Since the growth rate of the Weibel instability is proportional to the plasma density and velocity, the spatial and temporal scales of the Weibel instability can be much smaller than that from nanosecond large laser facilities. Recent theoretical and numerical studies have revealed that astrophysical collisionless shocks in sub-relativistic regimes in the absence and presence of an ambient magnetic field play essential roles in cosmic ray acceleration. With experimental verification in mind, we discuss the possible experimental models on the Weibel instability with intense short laser pulses. In order to show the experimental feasibility, we perform 2D particle-in-cell simulations in the absence of an external magnetic field as the first step and discuss the optimum conditions to realize the nonlinear evolutions of the Weibel instability in laboratories.
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Fan, Zheng, Danfeng Cui, Zengxing Zhang, Zhou Zhao, Hongmei Chen, Yanyun Fan, Penglu Li, Zhidong Zhang, Chenyang Xue und Shubin Yan. „Recent Progress of Black Silicon: From Fabrications to Applications“. Nanomaterials 11, Nr. 1 (26.12.2020): 41. http://dx.doi.org/10.3390/nano11010041.
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Since black silicon was discovered by coincidence, the special material was explored for many amazing material characteristics in optical, surface topography, and so on. Because of the material property, black silicon is applied in many spheres of a photodetector, photovoltaic cell, photo-electrocatalysis, antibacterial surfaces, and sensors. With the development of fabrication technology, black silicon has expanded in more and more applications and has become a research hotspot. Herein, this review systematically summarizes the fabricating method of black silicon, including nanosecond or femtosecond laser irradiation, metal-assisted chemical etching (MACE), reactive ion etching (RIE), wet chemical etching, electrochemical method, and plasma immersion ion implantation (PIII) methods. In addition, this review focuses on the progress in multiple black silicon applications in the past 10 years. Finally, the prospect of black silicon fabricating and various applications are outlined.
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Moldovan, Edit Roxana, Carlos Concheso Doria, José Luis Ocaña, Bogdan Istrate, Nicanor Cimpoesu, Liana Sanda Baltes, Elena Manuela Stanciu et al. „Morphological Analysis of Laser Surface Texturing Effect on AISI 430 Stainless Steel“. Materials 15, Nr. 13 (29.06.2022): 4580. http://dx.doi.org/10.3390/ma15134580.
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Laser surface texturing (LST) is a method to obtain micro-structures on the material’s surface for improving tribological performances, wetting tuning, surface treatment, and increasing adhesion. The material selected for LST is AISI 430 ferritic stainless steel, distinguished by the low cost in manufacturing, corrosion resistance, and high strength at elevated temperature. The present study addresses the morphology of new pattern designs (crater array, ellipse, and octagonal shapes). The patterns are applied on the stainless-steel surface by a non-contact method with high quality and precision nanosecond pulsed laser equipment. The investigation of laser parameter influence on thermal affected area and micro-structures is accomplished by morphological and elemental analysis (SEM + EDX). The parameters of the laser micro-patterning have a marked influence on the morphology, creating groove-type sections with different depths and recast material features. From the SEM characterization, the highest level of recast material is observed for concentric octagon LST design. Its application is more recommended for the preparation of the metal surface before hybrid welding. Additionally, the lack of the oxygen element in the case of this design suggests the possible use of the pattern in hybrid joining.
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Ndebele, Nobuhle, Zweli Hlatshwayo, Bokolombe P. Ngoy, Gugu Kubheka, John Mack und Tebello Nyokong. „Optical limiting properties of BODIPY dyes substituted with styryl or vinylene groups on the nanosecond timescale“. Journal of Porphyrins and Phthalocyanines 23, Nr. 07n08 (Juli 2019): 701–17. http://dx.doi.org/10.1142/s108842461930009x.
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The results of recent studies on the optical limiting properties of BODIPY dyes at 532 and 1064 nm are described and compared. The optical limiting properties of novel 1,7-dimethyl-3,5-di-4-dihydroxyborylstyryl- and 3,5,7-tristyryl-1-methyl-BODIPY dyes were studied in CH2Cl2 and C6H6 and polystyrene thin films using the open aperture Z-scan technique at 532 nm with nanosecond laser pulses to provide an example of how the effective nonlinear absorption coefficient, the third order susceptibility, hyperpolarizability and limiting thresholds can be calculated.
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Krkotić, P., S. Calatroni, M. Himmerlich, H. Neupert, A. T. Perez-Fontenla, S. Wackerow und A. Abdolvand. „RF Characterisation of Laser Treated Copper Surfaces for the Mitigation of Electron Cloud in Accelerators“. Journal of Physics: Conference Series 2687, Nr. 8 (01.01.2024): 082029. http://dx.doi.org/10.1088/1742-6596/2687/8/082029.
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Abstract In accelerator beam chambers and RF waveguides, electron cloud and multipacting can be mitigated effectively by reducing the secondary electron yield (SEY). In recent years, it has been established that laser-engineered surface structuring is a very efficient method to create a copper surface with a SEY maximum close to or even below unity. Different laser pulse durations, from nanoseconds to picoseconds, can be used to change surface morphology. Conversely, the characteristics that minimise the SEY, such as the moderately deep grooves and the redeposited nanoparticles, might have unfavourable consequences, including increased RF surface resistance. In this study, we describe the techniques used to measure the surface resistance of laser-treated copper samples using an enhanced dielectric resonator with 12 cm diameter sample sizes operating in the GHz range. The quantification basis lies in a non-contact measurement of the high-frequency losses, focusing on understanding the variation of surface resistance levels depending on the specifics of the treatment and possible post-treatment cleaning procedures.
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Dengler, Stefanie, und Bernd Eberle. „Investigations on the Nonlinear Optical Properties of 0D, 1D, and 2D Boron Nitride Nanomaterials in the Visible Spectral Region“. Nanomaterials 13, Nr. 12 (13.06.2023): 1849. http://dx.doi.org/10.3390/nano13121849.
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In recent years, boron nitride nanomaterials have attracted increasing attention due to their unique properties such as high temperature stability and high thermal conductivity. They are structurally analogous to carbon nanomaterials and can also be generated as zero-dimensional nanoparticles and fullerenes, one-dimensional nanotubes and nanoribbons, and two-dimensional nanosheets or platelets. In contrast to carbon-based nanomaterials, which have been extensively studied during recent years, the optical limiting properties of boron nitride nanomaterials have hardly been analysed so far. This work summarises a comprehensive study on the nonlinear optical response of dispersed boron nitride nanotubes, boron nitride nanoplatelets, and boron nitride nanoparticles using nanosecond laser pulses at 532 nm. Their optical limiting behaviour is characterised by means of nonlinear transmittance and scattered energy measurements and a beam profiling camera is used to analyse the beam characteristics of the transmitted laser radiation. Our results show that nonlinear scattering dominates the OL performance of all measured boron nitride nanomaterials. Boron nitride nanotubes show a large optical limiting effect, much stronger than the benchmark material, multi-walled carbon nanotubes, which makes them promising for laser protection applications.
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Kuznetsov, Alexey G., Sergey I. Kablukov, Yuri A. Timirtdinov und Sergey A. Babin. „Actively Mode Locked Raman Fiber Laser with Multimode LD Pumping“. Photonics 9, Nr. 8 (01.08.2022): 539. http://dx.doi.org/10.3390/photonics9080539.
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We present our recent experimental results on the pulsed regimes of Raman conversion of highly multimode laser diode (LD) pump radiation into the 1st and higher order Stokes radiation in multimode graded-index fibers. Three different linear cavities of Raman fiber laser with the modulation of losses (by acousto-optic modulator, AOM) or gain (by LD current) are explored and compared. An LD with wavelength of 976 nm is used for pumping enabling Raman lasing at wavelength of the 1st (1018 nm) and 2nd (1064 nm) Stokes orders. At ~27.2-kHz repetition rate corresponding to the laser cavity round-trip frequency (i.e., in the mode-locking regime), nanosecond pulses have been observed for both Stokes orders having the highest peak power of ~300 W in the scheme with bulk AOM and the shortest duration of 5–7 ns in the scheme with fiber-pigtailed AOM. At the same time, the beam quality of generated pulses is greatly improved as compared to that for pump diode (M2 > 20) reaching the best value (M2 = 2.05) for the 2nd order Stokes beam in the scheme with the gain modulation and demonstrating also the most stable regime.
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Tan, Ruiwang, Xu Wang, Zhanjiang Yu, Guangfeng Shi, Shen Yang, Yiquan Li und Jinkai Xu. „Laser processing characteristics of PCD tool and modeling analysis“. Laser Physics 34, Nr. 6 (15.04.2024): 065601. http://dx.doi.org/10.1088/1555-6611/ad3ae5.
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Abstract Through in-depth analysis of the experimental details and forming patterns of the nanosecond laser ablation polycrystalline diamond (PCD) textured tool processing system, this study explores the microscopic morphology and dimensions of micro-pits texture on the surface of PCD tools influenced by defocus amount, laser power, and pulse frequency. Experimental results indicate that the micro-pit textures generated under different parameters exhibit diversity, including rounded structure, fragments, recast layers, and heat-affected zones. The diameter and depth of micro-pits are comprehensively affected by defocus amount, laser power, and pulse frequency, showing complex patterns. After a thorough analysis of the effects of each parameter on the texture morphology, an artificial neural network (ANN) model is introduced for the prediction of micro-pit dimensions. Through model training and optimization, accurate predictions of micro-pit diameter and depth are obtained. In comparison to traditional regression models, the ANN model demonstrates outstanding predictive performance, validating its applicability in complex machining processes. This study not only provides a profound understanding of the processing patterns of PCD textured tools but also offers an effective predictive model for the optimization and control of similar future machining processes.
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Khaja, Fareen Adeni. „Contact Resistance Improvement for Advanced Logic by Integration of Epi, Implant and Anneal Innovations“. MRS Advances 4, Nr. 48 (2019): 2559–76. http://dx.doi.org/10.1557/adv.2019.416.
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ABSTRACTAs advanced CMOS scaling with FinFETs continues beyond the 10/7nm nodes, contact resistance (Rc) remains a dominant component affecting device performance. The FinFET Source/Drain (S/D) contact area has become smaller with fin pitch scaling, resulting in drastically increased Rc. To achieve higher drive currents and fully realize the performance gain from FinFET architectural changes, it is critical to continue to reduce contact resistivity (ρc) < 1.0x10-9 Ω.cm2 for both NMOS and PMOS. In this paper, we review the recent trends for ρc reduction for advanced CMOS devices and discuss approaches that have demonstrated reduction in ρc, such as in-situ heavily doped epitaxial films for S/D, advanced ion implantation and laser anneals. The implant techniques include pre-amorphization implants (PAI), dopant boosting implants, cryogenic (-100°C) implants for damage engineering and plasma doping (PLAD) for conformal doping of high aspect ratio (HAR) contacts. With such high levels of doping from epi and implants, advanced laser anneals are key for epitaxial regrowth and formation of metastable alloys for dopant supersaturation or segregation in top layers. Millisecond laser anneal (MSA) improves dopant activation and nanosecond laser anneal (NLA) permits superactivation, and both have become key enablers for ρc reduction. This paper also reviews two alternative contact approaches: dual silicide scheme and wrap-around contact (WAC), as potential pathways to further reduce Rc for advanced CMOS nodes.
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Parigger, Christian G. „Cyanide Molecular Laser-Induced Breakdown Spectroscopy with Current Databases“. Atoms 11, Nr. 4 (01.04.2023): 62. http://dx.doi.org/10.3390/atoms11040062.
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This work discusses diatomic molecular spectroscopy of laser-induced plasma and analysis of data records, specifically signatures of cyanide, CN. Line strength data from various databases are compared for simulation of the CN, B2Σ+⟶X2Σ+, Δv=0 sequence. Of interest are recent predictions using an astrophysical database, i.e., ExoMol, a laser-induced fluorescence database, i.e., LIFBASE, and a program for simulating rotational, vibrational, and electronic spectra, i.e., PGOPHER. Cyanide spectra that are predicted from these databases are compared with line-strength data that have been in use by the author for the last three decades in the analysis of laser–plasma emission spectra. Comparisons with experimental laser–plasma records are communicated as well for spectral resolutions of 33 and 110 picometer. The accuracy of the CN line-strength data is better than one picometer. Laboratory experiments utilize 308 nm, 35 picosecond bursts within an overall 1 nanosecond pulse-width, and 1064 nm, 6 ns pulse-width radiation. Experimental results are compared with predictions. Differences of the databases are elaborated for equilibrium of rotational and vibrational modes and at an internal, molecular temperature of the order of 8,000 Kelvin. Applications of accurate CN data include, for example, combustion diagnosis, chemistry, and supersonic and hypersonic expansion diagnosis. The cyanide molecule is also of interest in the study of astrophysical phenomena.
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Tabata, Toshiyuki, Fabien Rozé, Louis Thuries, Sébastien Halty, Pierre-Edouard Raynal, Imen Karmous und Karim Huet. „Recent Progresses and Perspectives of UV Laser Annealing Technologies for Advanced CMOS Devices“. Electronics 11, Nr. 17 (23.08.2022): 2636. http://dx.doi.org/10.3390/electronics11172636.
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The state-of-the-art CMOS technology has started to adopt three-dimensional (3D) integration approaches, enabling continuous chip density increment and performance improvement, while alleviating difficulties encountered in traditional planar scaling. This new device architecture, in addition to the efforts required for extracting the best material properties, imposes a challenge of reducing the thermal budget of processes to be applied everywhere in CMOS devices, so that conventional processes must be replaced without any compromise to device performance. Ultra-violet laser annealing (UV-LA) is then of prime importance to address such a requirement. First, the strongly limited absorption of UV light into materials allows surface-localized heat source generation. Second, the process timescale typically ranging from nanoseconds (ns) to microseconds (μs) efficiently restricts the heat diffusion in the vertical direction. In a given 3D stack, these specific features allow the actual process temperature to be elevated in the top-tier layer without introducing any drawback in the bottom-tier one. In addition, short-timescale UV-LA may have some advantages in materials engineering, enabling the nonequilibrium control of certain phenomenon such as crystallization, dopant activation, and diffusion. This paper reviews recent progress reported about the application of short-timescale UV-LA to different stages of CMOS integration, highlighting its potential of being a key enabler for next generation 3D-integrated CMOS devices.
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Min, Sujung, Kwang-Hoon Ko, Bumkyoung Seo, Changhyun Roh und Sangbum Hong. „Integration of Decay Time Analysis and Radiation Measurement for Quantum-Dot-Based Scintillator’s Characterization“. Processes 10, Nr. 10 (22.09.2022): 1920. http://dx.doi.org/10.3390/pr10101920.
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In this study, we demonstrated the process of an integrated apparatus for decay time analysis and gamma radiation measurement with a liquid-scintillator-based cadmium-doped zinc oxide (CZO) nanomaterial. Generally, time-resolved photon counting is an essential analysis method in the field of precision measurement in the quantum domain. Such photon counting equipment requires a pulse laser that can be repeated quickly while having a sharp pulse width of picoseconds or femtoseconds as a light source. Time-correlated single photon counting (TCSPC) equipment, which is currently a commercial product, is inconvenient for recent development research because the scintillator size and shape are limited. Here, neodymium-doped yttrium aluminum garnet (Nd/YAG) laser TCSPC equipment was constructed to analyze the fluorescence characteristics of scintillators having various sizes and shapes. Then, a liquid scintillator added with CZO nanomaterial was prepared and the Nd/YAG laser TCSPC equipment test was performed. As a result of measuring the scintillator using the manufactured Nd/YAG laser TCSPC equipment, the non-CZO liquid scintillator was analyzed at 2.30 ns and the liquid scintillator equipped with CZO-loaded nanomaterial was analyzed at 11.95 ns. It showed an error within 5% when compared with the result of commercial TCSPC equipment. In addition, it was verified that the Nd/YAG laser TCSPC system can sufficiently measure the decay time in nanoseconds (ns). Moreover, it was presented that the Compton edge energy of Cs−137 is 477.3 keV, which hardly generates a photoelectric effect, and Compton scattering mainly occurs.
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Sims, Melissa, Richard Briggs, Travis J. Volz, Saransh Singh, Sebastien Hamel, Amy L. Coleman, Federica Coppari et al. „Experimental and theoretical examination of shock-compressed copper through the fcc to bcc to melt phase transitions“. Journal of Applied Physics 132, Nr. 7 (21.08.2022): 075902. http://dx.doi.org/10.1063/5.0088607.
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Recent studies show a face-centered cubic (fcc) to body-centered cubic (bcc) transformation along the shock Hugoniot for several metals (i.e., Cu, Au, and Ag). Here, we combine laser-shock compression of Cu foils on nanosecond timescales with in situ x-ray diffraction (XRD) to examine the microstructural changes with stress. We study the fcc phase and the phase transition from fcc to bcc (pressures greater than 180 GPa). Textural analysis of the azimuthal intensities from the XRD images is consistent with transformation into the bcc phase through the Pitsch-distortion mechanism. We use embedded atom model molecular dynamics simulations to determine the stability of the bcc phase in pressure–temperature space. Our results indicate that the bcc phase is stabilized only at high temperatures and remains stable at pressures greater than 500 GPa.
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Yoo, Su, Doyoung Jung, Jung-Joon Min, Hyungwoo Kim und Changho Lee. „Biodegradable Contrast Agents for Photoacoustic Imaging“. Applied Sciences 8, Nr. 9 (06.09.2018): 1567. http://dx.doi.org/10.3390/app8091567.
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Over the past twenty years, photoacoustics—also called optoacoustics—have been widely investigated and, in particular, extensively applied in biomedical imaging as an emerging modality. Photoacoustic imaging (PAI) detects an ultrasound wave that is generated via photoexcitation and thermoelastic expansion by a short nanosecond laser pulse, which significantly reduces light and acoustic scattering, more than in other typical optical imaging and renders high-resolution tomographic images with preserving high absorption contrast with deep penetration depth. In addition, PAI provides anatomical and physiological parameters in non-invasive manner. Over the past two decades, this technique has been remarkably developed in the sense of instrumentation and contrast agent materials. In this review, we briefly introduce state-of-the-art multiscale imaging systems and summarize recent progress on exogenous bio-compatible and -degradable agents that address biomedical application and clinical practice.
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Xiang, Gaoming, Daiwei Li, Junqin Chen, Arpit Mishra, Georgy Sankin, Xuning Zhao, Yuqi Tang, Kevin Wang, Junjie Yao und Pei Zhong. „Dissimilar cavitation dynamics and damage patterns produced by parallel fiber alignment to the stone surface in holmium:yttrium aluminum garnet laser lithotripsy“. Physics of Fluids 35, Nr. 3 (März 2023): 033303. http://dx.doi.org/10.1063/5.0139741.
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Recent studies indicate that cavitation may play a vital role in laser lithotripsy. However, the underlying bubble dynamics and associated damage mechanisms are largely unknown. In this study, we use ultra-high-speed shadowgraph imaging, hydrophone measurements, three-dimensional passive cavitation mapping (3D-PCM), and phantom test to investigate the transient dynamics of vapor bubbles induced by a holmium:yttrium aluminum garnet laser and their correlation with solid damage. We vary the standoff distance ( SD) between the fiber tip and solid boundary under parallel fiber alignment and observe several distinctive features in bubble dynamics. First, long pulsed laser irradiation and solid boundary interaction create an elongated “pear-shaped” bubble that collapses asymmetrically and forms multiple jets in sequence. Second, unlike nanosecond laser-induced cavitation bubbles, jet impact on solid boundary generates negligible pressure transients and causes no direct damage. A non-circular toroidal bubble forms, particularly following the primary and secondary bubble collapses at SD = 1.0 and 3.0 mm, respectively. We observe three intensified bubble collapses with strong shock wave emissions: the intensified bubble collapse by shock wave, the ensuing reflected shock wave from the solid boundary, and self-intensified collapse of an inverted “triangle-shaped” or “horseshoe-shaped” bubble. Third, high-speed shadowgraph imaging and 3D-PCM confirm that the shock origins from the distinctive bubble collapse form either two discrete spots or a “smiling-face” shape. The spatial collapse pattern is consistent with the similar BegoStone surface damage, suggesting that the shockwave emissions during the intensified asymmetric collapse of the pear-shaped bubble are decisive for the solid damage.
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Luo Yao, 罗垚, 庞盛永 Pang Shengyong, 周建新 Zhou Jianxin und 李怀学 Li Huaixue. „Numerical Simulation of Recast Layer Formation in Nanosecond Pulse Laser Drilling on Nickel-Based High-Temperature Alloy“. Chinese Journal of Lasers 41, Nr. 4 (2014): 0403007. http://dx.doi.org/10.3788/cjl201441.0403007.
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Badziak, J. „Laser nuclear fusion: current status, challenges and prospect“. Bulletin of the Polish Academy of Sciences: Technical Sciences 60, Nr. 4 (01.12.2012): 729–38. http://dx.doi.org/10.2478/v10175-012-0084-8.
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Abstract In 2009, in Lawrence Livermore National Laboratory, USA, National Ignition Facility (NIF) - the largest thermonuclear fusion device ever made was launched. Its main part is a multi-beam laser whose energy in nanosecond pulse exceeds 1MJ (106 J). Its task is to compress DT fuel to the density over a few thousand times higher than that of solid-state DT and heat it to 100 millions of K degrees. In this case, the process of fuel compression and heating is realized in an indirect way - laser radiation (in UV range) is converted in the so-called hohlraum (1 cm cylinder with a spherical DT pellet inside) into very intense soft X radiation symmetrically illuminating DT pellet. For the first time ever, the fusion device’s energetic parameters are sufficient for the achieving the ignition and self-sustained burn of thermonuclear fuel on a scale allowing for the generation of energy far bigger than that delivered to the fuel. The main purpose of the current experimental campaign on NIF is bringing about, within the next two-three years, a controlled thermonuclear ‘big bang’ in which the fusion energy will exceed the energy delivered by the laser at least ten times. The expected ‘big bang’ would be the culmination of fifty years of international efforts aiming at demonstrating both physical and technical feasibility of generating, in a controlled way, the energy from nuclear fusion in inertial confined plasma and would pave the way for practical realization of the laser-driven thermonuclear reactor. This paper briefly reviews the basic current concepts of laser fusion and main problems and challenges facing the research community dealing with this field. In particular, the conventional, central hot spot ignition approach to laser fusion is discussed together with the more recent ones - fast ignition, shock ignition and impact ignition fusion. The research projects directed towards building an experimental laser-driven thermonuclear reactor are presented as well
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Erokhin, Alexander I., Nikolay A. Bulychev, Egor V. Parkevich, Mikhail A. Medvedev und Igor V. Smetanin. „Stimulated Thermal Scattering in Two-Photon Absorbing Nanocolloids under Laser Radiation of Nanosecond-to-Picosecond Pulse Widths“. Nanomaterials 12, Nr. 15 (26.07.2022): 2567. http://dx.doi.org/10.3390/nano12152567.
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Recent discoveries in nonlinear optical properties of nanoparticle colloids make actual the challenge to lower the energy threshold of phase conjugation and move it into the domain of shorter pulse widths. A novel effect of the stimulated Rayleigh-Mie scattering (SRMS) in two-photon absorbing nanocolloids is considered as a promising answer to this challenge. We report the results of experimental and theoretical study of the two-photon-assisted SRMS in Ag and ZnO nanocolloids in the nanosecond-to-picosecond pulse width domain. For 12 ns 0.527 μm laser pulses, the four-wave mixing SRMS scheme provides lasing and amplification of backscattered anti-Stokes signal in Ag nanocolloids in toluene at the threshold 0.2 mJ and the spectral shifts up to 150 MHz. For 100 ps 0.532 μm pulses, we observed for the first time efficient (over 50% in signal-to-pump ratio of pulse energies) SRMS backscattering of the anti-Stokes signal in Ag nanocolloids in toluene and predominantly Stokes signal in ZnO nanocolloids in water, with the spectral shifts up to 0.25 cm−1. We develop the first order-in-perturbation model of the four-wave mixing two-photon absorption-assisted SRMS process which shows that at nanosecond pulses, amplification is predominantly due to the thermal-induced coherent oscillations of polarization while the slow temperature wave acts also as a dynamic spatial grating which provides a self-induced optical cavity inside the interaction region. At a picosecond pulse width, according to our model, the spectral overlap between pump and signal pulses results in formation of only the dynamic spatial temperature grating, and we succeeded at recovering the linear growth of the spectral shift with the pump power near the threshold.
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Wang, Bin, Yihui Huang, Junke Jiao, Hao Wang, Ji Wang, Wenwu Zhang und Liyuan Sheng. „Numerical Simulation on Pulsed Laser Ablation of the Single-Crystal Superalloy Considering Material Moving Front and Effect of Comprehensive Heat Dissipation“. Micromachines 12, Nr. 2 (23.02.2021): 225. http://dx.doi.org/10.3390/mi12020225.
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In the present research, an iterative numerical model is proposed to investigate the nanosecond pulsed laser ablation (PLA) mechanism of the DD6 single-crystal superalloy. In the numerical model, two subroutines are introduced to trace the moving boundary and update the thermal load. The iteration between the main governing equation and the two subroutines enables the PLA numerical simulation to consider material moving front and effect of comprehensive heat dissipation including thermal convection and radiation. The basic experimental results exhibit a good agreement with simulation results which indicates the good accuracy of the simulation model. Therefore, the PLA mechanism of the DD6 single-crystal superalloy is studied base on the improved iterative model, which indicates the evolution of temperature field, ablation zone morphology, formation of recast layer and heat-affected zone are closely related with time. The temperature of the laser spot center increases sharply at the first stage, reaching a maximum value of 5252 K, and then decreases gradually. The thermal dissipation postpones the ablation rate but promotes the formation of a recast layer and heat-affected zone. Due to the evaporation and thermal dissipation, the depth of the molten layer exhibits two rapid increasing stages. The comprehensive analysis of the PLA processing by the improved simulation model helps the understanding of the intrinsic mechanism, which would contribute to the further optimizing parameters of PLA fabrication of the DD6 single-crystal superalloy.
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Dhasmana, Nitesh, Dalal Fadil, Anupama B. Kaul und Jayan Thomas. „Investigation of nonlinear optical properties of exfoliated MoS2 using Photoacoustic Zscan“. MRS Advances 1, Nr. 47 (2016): 3215–21. http://dx.doi.org/10.1557/adv.2016.456.
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ABSTRACTWe studied nonlinear absorption characteristics of exfoliated Molybdenum disulphide (MoS2) dispersion in 1-Methyl-2-pyrrolidinone and demonstrate a dual absorption characteristic at 532nm nanosecond pulsed laser wavelength. A number of recent reports demonstrate a saturable absorption in MoS2 and other 2D materials at low fluences and a deviation from this saturable absorption at higher fluence using open aperture Z scan (OZ scan) technique. It has been suggested that this deviation at higher fluences is due to nonlinear optical scattering. We have recently developed a new technique which combines OZ scan and photoacoustic Z-scan (PAZ-scan). It can measure photoacoustic and optical transmission signals simultaneously. The data obtained from both signals are employed to find nonlinear absorption parameters in non-linear optical materials. Our results reveal that non-linear scattering is not the cause of deviation of 2D materials from saturable absorption at higher fluences. We propose that the optical limiting behavior at higher fluence in these 2D materials is dominated by free carrier absorption.
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Daubriac, Richard, Rémi Demoulin, Sebastien Kerdiles, Pablo Acosta Alba, Jean-Michel Hartmann, Jean-Paul Barnes, Pawel Michałowski et al. „Impact of Nanosecond Laser Annealing on the Electrical Properties of Highly Boron-Doped Ultrathin Strained Si0.7Ge0.3 Layers“. ECS Meeting Abstracts MA2022-01, Nr. 29 (07.07.2022): 1279. http://dx.doi.org/10.1149/ma2022-01291279mtgabs.
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The CMOS scaling beyond 10 nm technology node requires high active dopant concentrations in source/drain modules to minimize contact resistance. Pulsed laser annealing has been targeted by chip manufacturers as a future option to enhance the activation level inside highly doped SiGe:B and Si:P regions, mostly used in PMOS and NMOS transistor fabrication, respectively. Indeed, this annealing process allows reaching high temperatures (above melt threshold), locally (~100nm below the surface) and with extremely fast temperature ramp rates (>109 °C/s), so that high doping levels have been demonstrated both in pure Si and Ge [1]. In a recent study, structural investigations allowed identifying the best conditions to obtain fully strained and defect-free undoped SiGe layers by liquid phase epitaxial regrowth (LPER) [2]. In this work, we report an analysis on the activation of boron dopants in similar layers. In-situ boron-doped 30 nm thick pseudomorphic Si0.7Ge0.3 layers were grown on p-type bulk Si (100) by CVD. Three different boron concentrations were incorporated inside these layers: 7.8x1019 (A), 1.4x1020 (B) and 2.3x1020 cm-3 (C). By combining the boron chemical profiles with the corresponding Hall effect measurements (Hall scattering factor: 0.35), it was possible to estimate the activation rate inside the as-grown strained SiGe layers and the impact of the possible inactive dopants on the transport properties. From the lowest to the highest boron chemical concentration, we found activation rates of ~100%, ~80% and ~60%, with no significant carrier mobility degradation, even in the sample with the highest fraction of inactive dopants. The SiGe layers were subsequently laser annealed in a SCREEN-LT3100 platform operating at 308 nm (XeCl laser) with a pulse duration around 160 ns. The laser energy densities (ED) ranged from 1.20 to 2.40 J/cm2 in order to investigate all the various annealing regimes. Results obtained using several characterization techniques were combined to determine the laser annealing regimes, quantify surface roughness and assess the layers’ composition, strain and crystalline quality. These results were compared to electrical measurements performed to analyse the evolution of the electrical parameters as a function of the laser anneal conditions, particularly the activation rate. For the lowly-doped and fully activated layer (A), the sheet resistance increases rapidly at the melt threshold (1.5 J/cm2, cf. Fig. 1, red curve), concomitantly with the appearance of a partial relaxation inside the layer (Fig. 2) and the formation of extended defects. The defects may induce a local dopant deactivation, while strain relaxation can result in a modification of the transport properties of the material (modified Hall scattering factor). Both phenomena can be therefore responsible for the observed increase of the sheet resistance. In contrast, for laser EDs allowing complete melt of the layer (i.e. beyond 2.0 J/cm2), the sheet resistance decreases with increasing ED and full activation is achieved (Fig. 3, red curve) together with strain recovery (Fig. 2) and no observable defects. For the highly-doped and partially activated layer (C), partial relaxation also occurs at the melt threshold (Fig. 2). However, thanks to the strain compensation effect of the small boron atoms, the relaxation level is lower compared to the lowly-doped sample and more quickly recovered when increasing the ED (no defects observed at 1.95 J/cm2, Fig. 4). In addition, the sheet resistance is found to continuously decrease as a function of the ED (Fig. 1, blue curve) independently of the strain state of the structure. This suggests that, in addition to the previously described phenomena, the initially inactive dopants are progressively incorporated into substitutional positions by LPER. Indeed, when full melt and strain recovery is achieved, a 100% dopant activation is also observed (Fig. 3, blue curve). Characterizations made on sample B suggest a similar behaviour to that of sample C. Finally, further results will be reported from additional experiments aiming at (i) better understanding the impact of strain relaxation on dopant activation and (ii) optimizing the laser annealing process to avoid relaxation. These experiments include the use of a shorter laser pulse for the annealing of the strained SiGe layers, as well as the comparison with results obtained from fully-relaxed boron-doped SiGe annealed under similar laser conditions. Acknowledgements: This work was supported by the European Union’s Horizon 2020 research and innovation program under grant agreement No. 871813 MUNDFAB. References: [1] F. Cristiano, A. La Magna, Laser annealing processes in semiconductor technology: Theory, modeling, and applications in nanoelectronics, Elsevier 2021 (9780128202555). [2] L. Dagault & al., Investigation of recrystallization and stress relaxation in nanosecond laser annealed Si1−xGex/Si epilayers, ASS, Vol. 527, 146752 (10.1016/j.apsusc.2020.146752). Figure 1
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Clouatre, Maison, und Makhin Thitsa. „Data-driven Sliding Mode Control for Pulses of Fluorescence in STED Microscopy Based on Förster Resonance Energy Transfer Pairs“. MRS Advances 5, Nr. 29-30 (2020): 1557–65. http://dx.doi.org/10.1557/adv.2020.11.
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ABSTRACTPairs of conjugate donor-acceptor fluorescent probes have proven themselves useful in stimulated emission depletion (STED) microscopy in recent years. For instance, it has been shown that the lifetime of said probes directly correlates to the resolution of the microscope. However, once the lifetimes of the probes have been optimized, it is desirable to control their fluorescence in order to improve the resolution further. Here, we propose combining model-free control with sliding mode control to track nanosecond pulses of red-shifted acceptor fluorescence in order to inhibit visible light emitted from the image plane, shrink the point spread function, and subsequently improve the resolution of the microscope. This is achieved by automatic adjustment of the STED laser beam pump power. This controller is numerically simulated against a generic model created from Förster resonance energy transfer (FRET) theory. However, since it is data-driven, it can be easily applied to various physical systems with drastically different dynamics. This work provides a reliable theoretic control solution to modern super resolution microscopy for biological imaging.
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Furube, Akihiro, Kohei Sasaki, Tatsuki Kokufu, Tetsuro Katayama und Koinkar Pankaj. „(Invited) Ultrafast Charge Transfer Dynamics in WS2–Au Nanohybrid System Fabricated by Pulsed Laser Ablation in Liquid“. ECS Meeting Abstracts MA2023-01, Nr. 14 (28.08.2023): 1372. http://dx.doi.org/10.1149/ma2023-01141372mtgabs.
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Nanosheet semiconductor materials have attracted much attention in recent years due to their unique optical, electronic, and chemical properties for various applications such as photodetectors, light emitters, photocatalysts, and biosensors. We have fabricated tungsten disulfide (WS2) nanostructures by pulsed laser ablation in liquid. We applied nanosecond and femtosecond lasers and found the latter to be suitable for nanosheet fabrication [1]. Visible light response was enhanced by attaching gold nanoparticles (AuNPs) onto WS2 nanosheets [2]. The charge transfer dynamics in the WS2-Au nanohybrid system was characterized using femtosecond diffuse reflectance spectroscopy. The nanosheet structure was found to reduce the bulk carrier property. Furthermore, modification with AuNPs was found to enhance the formation of carriers trapped deeply in the WS2 nanosheets. These findings will be useful for the design of future metal-nanosheet semiconductor hybrid systems. Reference Pankaj Koinkar, Kohei Sasaki, Tetsuro Katayama and Akihiro Furube, International Journal of Modern Physics B, 35, 2140007 (2021) Tatsuki Kokufu, Daichi Nakayama, Tetsuro Katayama, Koinkar Pankaj, and Akihiro Furube, The 13th Asia-Pacific Conference on Near-Field Optics, OL30-A13 (2022)
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Szreder, Tomasz. „Recent upgrading of the nanosecond pulse radiolysis setup and construction of laser flash photolysis setup at the Institute of Nuclear Chemistry and Technology in Warsaw, Poland“. Nukleonika 67, Nr. 3 (01.09.2022): 49–64. http://dx.doi.org/10.2478/nuka-2022-0005.
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Abstract Modification of pulse radiolysis (PR) setup and construction of a new laser flash photolysis (LFP) setup at the Institute of Nuclear Chemistry and Technology (INCT) is described. Both techniques are dedicated to studying fast reactions in real time by direct observation of transients. Time resolution of the PR setup at INCT was ~11 ns, limited by the duration of the electron pulse. Implementation of a new spectrophotometric detection system resulted in a significant broadening of experimental spectral range with respect to the previous setup. Noticeable reduction of the noise-to-signal ratio was also achieved. The LFP system was built from scratch. Its time resolution was ~6 ns, limited by the duration of a laser pulse. LFP and PR were purposely designed to share the same hardware and software solutions. Therefore, components of the detection systems can be transferred between both setups, significantly lowering the costs and shortening the construction/upgrading time. Opened architecture and improved experimental flexibility of both techniques were accomplished by implementation of Ethernet transmission control protocol/Internet protocol (TCP/IP) communication core and newly designed software. This is one of the most important enhancements. As a result, new experimental modes are available for both techniques, improving the quality and reducing the time of data collections. In addition, both systems are characterized by relatively high redundancy. Currently, implementation of new equipment into the systems hardly ever requires programming. In contrast to the previous setup, daily adaptations of hardware to experimental requirements are possible and relatively easy to perform.
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Abiev, Rufat Sh, Dmitry A. Sladkovskiy, Kirill V. Semikin, Dmitry Yu Murzin und Evgeny V. Rebrov. „Non-Thermal Plasma for Process and Energy Intensification in Dry Reforming of Methane“. Catalysts 10, Nr. 11 (22.11.2020): 1358. http://dx.doi.org/10.3390/catal10111358.
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Plasma-assisted dry reforming of methane (DRM) is considered as a potential way to convert natural gas into fuels and chemicals under near ambient temperature and pressure; particularly for distributed processes based on renewable energy. Both catalytic and photocatalytic technologies have been applied for DRM to investigate the CH4 conversion and the energy efficiency of the process. For conventional catalysis; metaldoped Ni-based catalysts are proposed as a leading vector for further development. However; coke deposition leads to fast deactivation of catalysts which limits the catalyst lifetime. Photocatalysis in combination with non-thermal plasma (NTP), on the other hand; is an enabling technology to convert CH4 to more reactive intermediates. Placing the catalyst directly in the plasma zone or using post-plasma photocatalysis could generate a synergistic effect to increase the formation of the desired products. In this review; the recent progress in the area of NTP-(photo)catalysis applications for DRM has been described; with an in-depth discussion of novel plasma reactor types and operational conditions including employment of ferroelectric materials and nanosecond-pulse discharges. Finally, recent developments in the area of optical diagnostic tools for NTP, such as optical emission spectroscopy (OES), in-situ FTIR, and tunable diode laser absorption spectroscopy (TDLAS), are reviewed.
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Ebrahimi, Mojtaba, und Abdolnasser Zakery. „Nonlinear Optical Properties of Materials Based on Graphene Oxide: A Review“. Current Nanomaterials 4, Nr. 3 (11.11.2019): 151–59. http://dx.doi.org/10.2174/2405461504666190923114028.
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Background: Nonlinear optical properties of Graphene and Graphene Oxide have been widely used in industry and academia. Graphene oxide disperses easily in water and has easier interaction with other materials because of the presence of oxygen groups. So, this feature of Graphene oxide enables us to manipulate its nonlinear optical properties by combining it with other nanoparticles. Objective: We introduced recent advances in the nonlinear optical properties of materials based on Graphene oxide. Methods: Nonlinear optical properties and optical limiting of Graphene oxide and/or its composites with various nanoparticles, considering the wavelength and the incident pulse width, are investigated in this review. Conclusion: At low intensities and in all pulse regimes, saturation absorption seems to be the dominant mechanism of nonlinear absorption in Graphene oxide, while at higher intensities, the main mechanism is the reverse saturation absorption. In the regime of very short pulses of picoseconds and femtoseconds, the dominant mechanisms of two-photon and multiphoton absorption lead to reverse saturation. In the nanosecond pulse regime, long laser pulses and short pulses with high pulse repetition rates, excited-state absorption and nonlinear scattering due to thermal effects are causing the nonlinear process.
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Cailleau, Hervé, Maciej Lorenc, Laurent Guérin, Marina Servol, Eric Collet und Marylise Buron-Le Cointe. „Structural dynamics of photoinduced molecular switching in the solid state“. Acta Crystallographica Section A Foundations of Crystallography 66, Nr. 2 (18.02.2010): 189–97. http://dx.doi.org/10.1107/s0108767309051046.
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Fast and ultra-fast time-resolved diffraction is a fantastic tool for directly observing the structural dynamics of a material rearrangement during the transformation induced by an ultra-short laser pulse. The paper illustrates this ability using the dynamics of photoinduced molecular switching in the solid state probed by 100 ps X-ray diffraction. This structural information is crucial for establishing the physical foundations of how to direct macroscopic photoswitching in materials. A key feature is that dynamics follow a complex pathway from molecular to material scales through a sequence of processes. Not only is the pathway indirect, the nature of the dynamical processes along the pathway depends on the timescale. This dictates which types of degrees of freedom are involved in the subsequent dynamics or kinetics and which are frozen or statistically averaged. We present a recent investigation of the structural dynamics in multifunctional spin-crossover materials, which are prototypes of molecular bistability in the solid state. The time-resolved X-ray diffraction results show that the dynamics span from subpicosecond molecular photoswitching followed by volume expansion (on a nanosecond timescale) and additional thermoswitching (on a microsecond timescale).
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Lim, Shao Qi, und James S. Williams. „Electrical and Optical Doping of Silicon by Pulsed-Laser Melting“. Micro 2, Nr. 1 (24.12.2021): 1–22. http://dx.doi.org/10.3390/micro2010001.
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Over four decades ago, pulsed-laser melting, or pulsed-laser annealing as it was termed at that time, was the subject of intense study as a potential advance in silicon device processing. In particular, it was found that nanosecond laser melting of the near-surface of silicon and subsequent liquid phase epitaxy could not only very effectively remove lattice disorder following ion implantation, but could achieve dopant electrical activities exceeding equilibrium solubility limits. However, when it was realised that solid phase annealing at longer time scales could achieve similar results, interest in pulsed-laser melting waned for over two decades as a processing method for silicon devices. With the emergence of flat panel displays in the 1990s, pulsed-laser melting was found to offer an attractive solution for large area crystallisation of amorphous silicon and dopant activation. This method gave improved thin film transistors used in the panel backplane to define the pixelation of displays. For this application, ultra-rapid pulsed laser melting remains the crystallisation method of choice since the heating is confined to the silicon thin film and the underlying glass or plastic substrates are protected from thermal degradation. This article will be organised chronologically, but treatment naturally divides into the two main topics: (1) an electrical doping research focus up until around 2000, and (2) optical doping as the research focus after that time. In the first part of this article, the early pulsed-laser annealing studies for electrical doping of silicon are reviewed, followed by the more recent use of pulsed-lasers for flat panel display fabrication. In terms of the second topic of this review, optical doping of silicon for efficient infrared light detection, this process requires deep level impurities to be introduced into the silicon lattice at high concentrations to form an intermediate band within the silicon bandgap. The chalcogen elements and then transition metals were investigated from the early 2000s since they can provide the required deep levels in silicon. However, their low solid solubilities necessitated ultra-rapid pulsed-laser melting to achieve supersaturation in silicon many orders of magnitude beyond the equilibrium solid solubility. Although infrared light absorption has been demonstrated using this approach, significant challenges were encountered in attempting to achieve efficient optical doping in such cases, or hyperdoping as it has been termed. Issues that limit this approach include: lateral and surface impurity segregation during solidification from the melt, leading to defective filaments throughout the doped layer; and poor efficiency of collection of photo-induced carriers necessary for the fabrication of photodetectors. The history and current status of optical hyperdoping of silicon with deep level impurities is reviewed in the second part of this article.
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Hora, H., S. Eliezer, G. J. Kirchhoff, N. Nissim, J. X. Wang, P. Lalousis, Y. X. Xu et al. „Road map to clean energy using laser beam ignition of boron-hydrogen fusion“. Laser and Particle Beams 35, Nr. 4 (Dezember 2017): 730–40. http://dx.doi.org/10.1017/s0263034617000799.
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AbstractWith the aim to overcome the problems of climatic changes and rising ocean levels, one option is to produce large-scale sustainable energy by nuclear fusion of hydrogen and other very light nuclei similar to the energy source of the sun. Sixty years of worldwide research for the ignition of the heavy hydrogen isotopes deuterium (D) and tritium (T) have come close to a breakthrough for ignition. The problem with the DT fusion is that generated neutrons are producing radioactive waste. One exception as the ideal clean fusion process – without neutron production – is the fusion of hydrogen (H) with the boron isotope11B11 (B11). In this paper, we have mapped out our research based on recent experiments and simulations for a new energy source. We suggest how HB11 fusion for a reactor can be used instead of the DT option. We have mapped out our HB11 fusion in the following way: (i) The acceleration of a plasma block with a laser beam with the power and time duration of the order of 10 petawatts and one picosecond accordingly. (ii) A plasma confinement by a magnetic field of the order of a few kiloteslas created by a second laser beam with a pulse duration of a few nanoseconds (ns). (iii) The highly increased fusion of HB11 relative to present DT fusion is possible due to the alphas avalanche created in this process. (iv) The conversion of the output charged alpha particles directly to electricity. (v) To prove the above ideas, our simulations show for example that 14 milligram HB11 can produce 300 kWh energy if all achieved results are combined for the design of an absolutely clean power reactor producing low-cost energy.
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Chng, Tat Loon, David Z. Pai, Olivier Guaitella, Svetlana M. Starikovskaia und Anne Bourdon. „Effect of the electric field profile on the accuracy of E-FISH measurements in ionization waves“. Plasma Sources Science and Technology 31, Nr. 1 (01.01.2022): 015010. http://dx.doi.org/10.1088/1361-6595/ac4592.
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Abstract Electric field induced second harmonic (E-FISH) generation has emerged as a versatile tool for measuring absolute electric field strengths in time-varying, non-equilibrium plasmas and gas discharges. Yet recent work has demonstrated that the E-FISH signal, when produced with tightly focused laser beams, exhibits a strong dependence on both the length and shape of the applied electric field profile (along the axis of laser beam propagation). In this paper, we examine the effect of this dependence more meaningfully, by predicting what an E-FISH experiment would measure in a plasma, using 2D axisymmetric numerical fluid simulations as the true value. A pin-plane nanosecond discharge at atmospheric pressure is adopted as the test configuration, and the electric field evolution during the propagation of the ionization wave (IW) is specifically analysed. We find that the various phases of this evolution (before and up to the front arrival, immediately behind the front and after the connection to the grounded plane) are quite accurately described by three unique electric field profile shapes, each of which produces a different response in the E-FISH signal. As a result, the accuracy of an E-FISH measurement is generally predicted to be comparable in the first and third phases of the IW evolution, and significantly poorer in the second (intermediate) phase. Fortunately, even though the absolute error in the field strength at certain time instants could be large, the overall shape of the field evolution curve is relatively well captured by E-FISH. Guided by the simulation results, we propose a procedure for estimating the error in the initial phase of the IW development, based on the presumption that the starting field profile mirrors that of its corresponding Laplacian conditions before evolving further. We expect that this approach may be readily generalized and applicable to other IW problems or phenomena, thus extending the utility of the E-FISH diagnostic.