Zeitschriftenartikel: „Ultrafast current“

1

Lu Wen-Tian, Yao Chun-Wei, YAN Zhi und YUAN Zhe. „Ultrafast Spin Dynamics Research on Laser-Induced Spin Valve Structures“. Acta Physica Sinica 74, Nr. 6 (2025): 0. https://doi.org/10.7498/aps.74.20241744.

Der volle Inhalt der Quelle

Annotation:

The discovery of ultrafast demagnetization has introduced a new approach for generating ultrafast spin currents using an ultrashort laser, potentially enabling faster manipulation of material magnetism. This has sparked research into the transport mechanisms of ultrafast spin currents. However, the underlying processes remain poorly understood, particularly the factors influencing interlayer spin transfer. This study employs a superdiffusive spin transport model to investigate the ultrafast spin transport mechanisms in the Ni/Ru/Fe spin valve system, with a particular focus on how interlayer spin transfer affects the ultrafast magnetization dynamics of the ferromagnetic layer. First, by calculating the laser-induced magnetization dynamics of the Ni/Ru/Fe system under different magnetization alignments, the study validates recent experimental findings. Further analysis reveals that reducing the thickness of the Ru spacer layer significantly enhances the spin current intensity and increases the demagnetization difference in the Fe layer, confirming the key role of the hot electron spin current generated by the Ni layer in interlayer spin transport. Additionally, the spin decay length of hot electron spin currents in the spacer Ru layer is determined to be approximately 0.5 nm. This study also shows that laser-induced transient magnetization enhancement can be achieved by adjusting the relative laser absorption in the films. These results provide theoretical support for the future ultrafast magnetic control of spin valve structures and contribute to the advancement of spintronics in high-speed information processing and storage applications.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

2

Sotome, M., M. Nakamura, J. Fujioka, M. Ogino, Y. Kaneko, T. Morimoto, Y. Zhang et al. „Spectral dynamics of shift current in ferroelectric semiconductor SbSI“. Proceedings of the National Academy of Sciences 116, Nr. 6 (22.01.2019): 1929–33. http://dx.doi.org/10.1073/pnas.1802427116.

Der volle Inhalt der Quelle

Annotation:

Photoexcitation in solids brings about transitions of electrons/holes between different electronic bands. If the solid lacks an inversion symmetry, these electronic transitions support spontaneous photocurrent due to the geometric phase of the constituting electronic bands: the Berry connection. This photocurrent, termed shift current, is expected to emerge on the timescale of primary photoexcitation process. We observe ultrafast evolution of the shift current in a prototypical ferroelectric semiconductor antimony sulfur iodide (SbSI) by detecting emitted terahertz electromagnetic waves. By sweeping the excitation photon energy across the bandgap, ultrafast electron dynamics as a source of terahertz emission abruptly changes its nature, reflecting a contribution of Berry connection on interband optical transition. The shift excitation carries a net charge flow and is followed by a swing over of the electron cloud on a subpicosecond timescale. Understanding these substantive characters of the shift current with the help of first-principles calculation will pave the way for its application to ultrafast sensors and solar cells.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

3

Kiemle, Jonas, Philipp Zimmermann, Alexander W. Holleitner und Christoph Kastl. „Light-field and spin-orbit-driven currents in van der Waals materials“. Nanophotonics 9, Nr. 9 (29.06.2020): 2693–708. http://dx.doi.org/10.1515/nanoph-2020-0226.

Der volle Inhalt der Quelle

Annotation:

AbstractThis review aims to provide an overview over recent developments of light-driven currents with a focus on their application to layered van der Waals materials. In topological and spin-orbit dominated van der Waals materials helicity-driven and light-field-driven currents are relevant for nanophotonic applications from ultrafast detectors to on-chip current generators. The photon helicity allows addressing chiral and non-trivial surface states in topological systems, but also the valley degree of freedom in two-dimensional van der Waals materials. The underlying spin-orbit interactions break the spatiotemporal electrodynamic symmetries, such that directed currents can emerge after an ultrafast laser excitation. Equally, the light-field of few-cycle optical pulses can coherently drive the transport of charge carriers with sub-cycle precision by generating strong and directed electric fields on the atomic scale. Ultrafast light-driven currents may open up novel perspectives at the interface between photonics and ultrafast electronics.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

4

Cottrell, W. J., T. G. Ference und K. A. Puzey. „Improved magnetooptic modulator for ultrafast current pulses“. IEEE Photonics Technology Letters 14, Nr. 5 (Mai 2002): 624–26. http://dx.doi.org/10.1109/68.998705.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

5

Lian, Meng, und Jie Wu. „Ultrafast micropumping by biased alternating current electrokinetics“. Applied Physics Letters 94, Nr. 6 (09.02.2009): 064101. http://dx.doi.org/10.1063/1.3080681.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

6

Kim, Un-Tae, Myeong-Hun Jo und Hyo-Jin Ahn. „Microgrid-Patterned Ni Foams as Current Collectors for Ultrafast Energy Storage Devices“. Metals 14, Nr. 3 (19.03.2024): 354. http://dx.doi.org/10.3390/met14030354.

Der volle Inhalt der Quelle

Annotation:

Current research is focused on developing active materials through surface functionalization, porosity, composites, and doping for ultrafast electric double layer capacitors (EDLCs). In this study, deviating from existing strategies focused on active materials, we designed tunable 3D microgrid-patterned (MP) surface morphologies on Ni foams used as current collectors using SUS meshes as rigid stamps during roll pressing. The surface geometries of the MP-Ni foams were controlled to standard mesh scales of 24, 40, and 60 (denoted as 24MP-Ni, 40MP-Ni, and 60MP-Ni, respectively). The three MP-Ni samples with different microgrid sizes presented different surface geometries, such as root-mean-square roughness (Rrms), skewness roughness (Rsk), and width/depth scales of the microgrid patterns. Consequently, 40MP-Ni demonstrated an optimized surface geometry with high Rrms (35.4 μm) and Rsk (−0.19) values, which facilitated deep slurry infiltration and increased its contact area with the active material. Surface optimization of the MP-Ni enabled ultrafast and reversible charge transport kinetics owing to its relaxed electron transfer resistance and robust adhesion to the active material compared with bare Ni foam. EDLC electrodes with 40MP-Ni achieved an ultrafast-rate capability (96.0 F/g at 20 A/g) and ultrafast longevity (101.9% capacity retention after 5000 cycles at 5 A/g) without specific modification of active material.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

7

Sobacchi, Emanuele, Tsvi Piran und Luca Comisso. „Ultrafast Variability in AGN Jets: Intermittency and Lighthouse Effect“. Astrophysical Journal Letters 946, Nr. 2 (01.04.2023): L51. http://dx.doi.org/10.3847/2041-8213/acc84d.

Der volle Inhalt der Quelle

Annotation:

Abstract Gamma-ray flares from active galactic nuclei (AGNs) show substantial variability on ultrafast timescales (i.e., shorter than the light-crossing time of the AGN’s supermassive black hole). We propose that ultrafast variability is a by-product of the turbulent dissipation of the jet Poynting flux. Due to the intermittency of the turbulent cascade, the dissipation is concentrated in a set of reconnecting current sheets. Electrons energized by reconnection have a strong pitch-angle anisotropy, i.e., their velocity is nearly aligned with the guide magnetic field. Then each current sheet produces a narrow radiation beam, which dominates the emission from the whole jet when it is directed toward the observer. The ultrafast variability is set by the light-crossing time of a single current sheet, which is much shorter than the light-crossing time of the whole emission region. The predictions of our model are (i) the bolometric luminosity of ultrafast AGN flares is dominated by the inverse Compton (IC) emission as the lower-energy synchrotron emission is suppressed due to the pitch-angle anisotropy; (ii) if the observed luminosity includes a nonflaring component, the variations of the synchrotron luminosity have a small amplitude; and (iii) the synchrotron and IC emission are less variable at lower frequencies, as the cooling time of the radiating particles exceeds the light-crossing time of the current sheet. Simultaneous multiwavelength observations of ultrafast AGN flares can test these predictions.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

8

Zymmer, K., und P. Mazurek. „Comparative investigation of SiC and Si power electronic devices operating at high switching frequency“. Bulletin of the Polish Academy of Sciences: Technical Sciences 59, Nr. 4 (01.12.2011): 555–59. http://dx.doi.org/10.2478/v10175-011-0068-0.

Der volle Inhalt der Quelle

Annotation:

Comparative investigation of SiC and Si power electronic devices operating at high switching frequencyThe paper presents results of measurements of the reverse recovery current and dynamic forward voltage of the silicon carbide (SiC) Schottky diodes operating at a 500 A/μs current slope. These data were compared with the corresponding parameters determined for ultrafast silicon (Si) diodes. Results of power losses measurement in SiC Schottky diodes operating at switching frequency range of (10-200) kHz are presented and compared with corresponding data of ultrafast Si diodes. Also, results of power losses measurements in transistors of dc voltage switch are shown. Investigations were conducted with a SiC and the ultrafast Si freewheeling diode at the transistor switching frequency of 100 kHz. The results of measuring power losses dissipated in the dc converter with a SiC Schottky diode and the ultrafast silicon diode are also presented.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

9

Elezzabi, A. Y., und M. R. Freeman. „Ultrafast magneto‐optic sampling of picosecond current pulses“. Applied Physics Letters 68, Nr. 25 (17.06.1996): 3546–48. http://dx.doi.org/10.1063/1.116632.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

10

Wagner, Ronald S., Jeffrey M. Bradley, Carl J. Maggiore, Jerome G. Beery und Robert B. Hammond. „An Approach to Measure Ultrafast-Funneling-Current Transients“. IEEE Transactions on Nuclear Science 33, Nr. 6 (1986): 1651–56. http://dx.doi.org/10.1109/tns.1986.4334658.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

11

Prechtel, L., S. Manus, D. Schuh, W. Wegscheider und A. W. Holleitner. „Spatially resolved ultrafast transport current in GaAs photoswitches“. Applied Physics Letters 96, Nr. 26 (28.06.2010): 261110. http://dx.doi.org/10.1063/1.3458819.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

12

Li, Zhangshun, Yexin Jiang, Zuanming Jin, Zhuoyi Li, Xianyang Lu, Zhijiang Ye, Jin-Yi Pang, Yongbing Xu und Yan Peng. „Terahertz Emission Spectroscopy of Ultrafast Coupled Spin and Charge Dynamics in Nanometer Ferromagnetic Heterostructures“. Nanomaterials 12, Nr. 23 (30.11.2022): 4267. http://dx.doi.org/10.3390/nano12234267.

Der volle Inhalt der Quelle

Annotation:

Due to its high sensitivity and because it does not rely on the magneto-optical response, terahertz (THz) emission spectroscopy has been used as a powerful time-resolved tool for investigating ultrafast demagnetization and spin current dynamics in nanometer-thick ferromagnetic (FM)/heavy metal (HM) heterostructures. Here, by changing the order of the conductive HM coating on the FM nanometer film, the dominant electric dipole contribution to the laser-induced THz radiation can be unraveled from the ultrafast magnetic dipole. Furthermore, to take charge equilibration into account, we separate the femtosecond laser-induced spin-to-charge converted current and the instantaneous discharging current within the illuminated area. The THz emission spectroscopy gives us direct information into the coupled spin and charge dynamics during the first moments of the light–matter interaction. Our results also open up new perspectives to manipulate and optimize the ultrafast charge current for promising high-performance and broadband THz radiation.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

13

Khakurel, Krishna Prasad, Gabriel Žoldák, Borislav Angelov und Jakob Andreasson. „On the feasibility of time-resolved X-ray powder diffraction of macromolecules using laser-driven ultrafast X-ray sources“. Journal of Applied Crystallography 57, Nr. 4 (29.07.2024): 1205–11. http://dx.doi.org/10.1107/s1600576724005028.

Der volle Inhalt der Quelle

Annotation:

With the emergence of ultrafast X-ray sources, interest in following fast processes in small molecules and macromolecules has increased. Most of the current research into ultrafast structural dynamics of macromolecules uses X-ray free-electron lasers. In parallel, small-scale laboratory-based laser-driven ultrafast X-ray sources are emerging. Continuous development of these sources is underway, and as a result many exciting applications are being reported. However, because of their low flux, such sources are not commonly used to study the structural dynamics of macromolecules. This article examines the feasibility of time-resolved powder diffraction of macromolecular microcrystals using a laboratory-scale laser-driven ultrafast X-ray source.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

14

Fognini, A., T. U. Michlmayr, A. Vaterlaus und Y. Acremann. „Laser-induced ultrafast spin current pulses: a thermodynamic approach“. Journal of Physics: Condensed Matter 29, Nr. 21 (25.04.2017): 214002. http://dx.doi.org/10.1088/1361-648x/aa6a76.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

15

Sotome, M., M. Nakamura, J. Fujioka, M. Ogino, Y. Kaneko, T. Morimoto, Y. Zhang et al. „Ultrafast spectroscopy of shift-current in ferroelectric semiconductor Sn2P2S6“. Applied Physics Letters 114, Nr. 15 (15.04.2019): 151101. http://dx.doi.org/10.1063/1.5087960.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

16

Fedorov, Ivan I., Sergey A. Protasov, Irina A. Tarasova und Mikhail V. Gorshkov. „Ultrafast Proteomics“. Biochemistry (Moscow) 89, Nr. 8 (August 2024): 1349–61. http://dx.doi.org/10.1134/s0006297924080017.

Der volle Inhalt der Quelle

Annotation:

Abstract Current stage of proteomic research in the field of biology, medicine, development of new drugs, population screening, or personalized approaches to therapy dictates the need to analyze large sets of samples within the reasonable experimental time. Until recently, mass spectrometry measurements in proteomics were characterized as unique in identifying and quantifying cellular protein composition, but low throughput, requiring many hours to analyze a single sample. This was in conflict with the dynamics of changes in biological systems at the whole cellular proteome level upon the influence of external and internal factors. Thus, low speed of the whole proteome analysis has become the main factor limiting developments in functional proteomics, where it is necessary to annotate intracellular processes not only in a wide range of conditions, but also over a long period of time. Enormous level of heterogeneity of tissue cells or tumors, even of the same type, dictates the need to analyze biological systems at the level of individual cells. These studies involve obtaining molecular characteristics for tens, if not hundreds of thousands of individual cells, including their whole proteome profiles. Development of mass spectrometry technologies providing high resolution and mass measurement accuracy, predictive chromatography, new methods for peptide separation by ion mobility and processing of proteomic data based on artificial intelligence algorithms have opened a way for significant, if not radical, increase in the throughput of whole proteome analysis and led to implementation of the novel concept of ultrafast proteomics. Work done just in the last few years has demonstrated the proteome-wide analysis throughput of several hundred samples per day at a depth of several thousand proteins, levels unimaginable three or four years ago. The review examines background of these developments, as well as modern methods and approaches that implement ultrafast analysis of the entire proteome.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

17

Feng, Jiecai, Junzhe Wang, Hongfei Liu, Yanning Sun, Xuewen Fu, Shaozheng Ji, Yang Liao und Yingzhong Tian. „A Review of an Investigation of the Ultrafast Laser Processing of Brittle and Hard Materials“. Materials 17, Nr. 15 (24.07.2024): 3657. http://dx.doi.org/10.3390/ma17153657.

Der volle Inhalt der Quelle

Annotation:

Ultrafast laser technology has moved from ultrafast to ultra-strong due to the development of chirped pulse amplification technology. Ultrafast laser technology, such as femtosecond lasers and picosecond lasers, has quickly become a flexible tool for processing brittle and hard materials and complex micro-components, which are widely used in and developed for medical, aerospace, semiconductor applications and so on. However, the mechanisms of the interaction between an ultrafast laser and brittle and hard materials are still unclear. Meanwhile, the ultrafast laser processing of these materials is still a challenge. Additionally, highly efficient and high-precision manufacturing using ultrafast lasers needs to be developed. This review is focused on the common challenges and current status of the ultrafast laser processing of brittle and hard materials, such as nickel-based superalloys, thermal barrier ceramics, diamond, silicon dioxide, and silicon carbide composites. Firstly, different materials are distinguished according to their bandgap width, thermal conductivity and other characteristics in order to reveal the absorption mechanism of the laser energy during the ultrafast laser processing of brittle and hard materials. Secondly, the mechanism of laser energy transfer and transformation is investigated by analyzing the interaction between the photons and the electrons and ions in laser-induced plasma, as well as the interaction with the continuum of the materials. Thirdly, the relationship between key parameters and ultrafast laser processing quality is discussed. Finally, the methods for achieving highly efficient and high-precision manufacturing of complex three-dimensional micro-components are explored in detail.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

18

Hai, Kuo, Yunrong Luo, Guishu Chong, Hao Chen und Wenhua Hai. „Analytical evidence of ultrafast generation of spin-motion entanglement“. Quantum Information and Computation 17, Nr. 5&6 (April 2017): 456–68. http://dx.doi.org/10.26421/qic17.5-6-5.

Der volle Inhalt der Quelle

Annotation:

We investigate ultrafast generation of spin-motion entanglement of a trapped and Gaussian-pulse-kicked two-level ion in the Lamb-Dicke limit and high field regime. A set of exact motional states and the probabilities occupying different pseudospin states are derived and the visible differences between the results with those of the delta-kick case are shown during a kick moment, which analytically evidence the ultrafast generation of an exact spin-motion entangled state regardless of initial state. Our results can be justified with the current experimental capability and provide an analytical method for further study of the ultrafast entanglement in atomic qubits.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

19

Wu, Yuxiang, Yongxiong Chen, Lingchao Kong, Zhiyuan Jing und Xiubing Liang. „A Review on Ultrafast-Laser Power Bed Fusion Technology“. Crystals 12, Nr. 10 (18.10.2022): 1480. http://dx.doi.org/10.3390/cryst12101480.

Der volle Inhalt der Quelle

Annotation:

Additive manufacturing of metals by employing continuous wave and short pulse lasers completely changes the way of modern industrial production. But the ultrafast laser has the superiority to short pulse laser and continuous wave laser in additive manufacturing. It has higher peak power, small thermal effect, high machining accuracy and low damage threshold. It can effectively perform additive manufacturing for special materials and improve the mechanical properties of parts. This article reviews the mechanism of the interaction between ultrafast laser and metal materials to rule the manufacturing processes. The current application of ultrafast laser on forming and manufacturing special materials, including refractory metals, transparent materials, composite materials and high thermal conductivity materials are also discussed. Among the review, the shortcomings and challenges of the current experimental methods are discussed as well. Finally, suggestions are provided for the industrial application of ultrashort pulse laser in the field of additive manufacturing in the future.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

20

Kudelin, Igor, Srikanth Sugavanam und Maria Chernysheva. „Rotation Active Sensors Based on Ultrafast Fibre Lasers“. Sensors 21, Nr. 10 (19.05.2021): 3530. http://dx.doi.org/10.3390/s21103530.

Der volle Inhalt der Quelle

Annotation:

Gyroscopes merit an undeniable role in inertial navigation systems, geodesy and seismology. By employing the optical Sagnac effect, ring laser gyroscopes provide exceptionally accurate measurements of even ultraslow angular velocity with a resolution up to 10−11 rad/s. With the recent advancement of ultrafast fibre lasers and, particularly, enabling effective bidirectional generation, their applications have been expanded to the areas of dual-comb spectroscopy and gyroscopy. Exceptional compactness, maintenance-free operation and rather low cost make ultrafast fibre lasers attractive for sensing applications. Remarkably, laser gyroscope operation in the ultrashort pulse generation regime presents a promising approach for eliminating sensing limitations caused by the synchronisation of counter-propagating channels, the most critical of which is frequency lock-in. In this work, we overview the fundamentals of gyroscopic sensing and ultrafast fibre lasers to bridge the gap between tools development and their real-world applications. This article provides a historical outline, highlights the most recent advancements and discusses perspectives for the expanding field of ultrafast fibre laser gyroscopes. We acknowledge the bottlenecks and deficiencies of the presented ultrafast laser gyroscope concepts due to intrinsic physical effects or currently available measurement methodology. Finally, the current work outlines solutions for further ultrafast laser technology development to translate to future commercial gyroscopes.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

21

Samreen, Naziya, Cecilia Mercado, Laura Heacock, Celin Chacko, Savannah C. Partridge und Chloe Chhor. „Screening Breast MRI Primer: Indications, Current Protocols, and Emerging Techniques“. Journal of Breast Imaging 3, Nr. 3 (02.04.2021): 387–98. http://dx.doi.org/10.1093/jbi/wbaa116.

Der volle Inhalt der Quelle

Annotation:

Abstract Breast dynamic contrast-enhanced MRI (DCE-MRI) is the most sensitive imaging modality for the detection of breast cancer. Screening MRI is currently performed predominantly in patients at high risk for breast cancer, but it could be of benefit in patients at intermediate risk for breast cancer and patients with dense breasts. Decreasing scan time and image interpretation time could increase cost-effectiveness, making screening MRI accessible to a larger group of patients. Abbreviated breast MRI (Ab-MRI) reduces scan time by decreasing the number of sequences obtained, but as multiple delayed contrast enhanced sequences are not obtained, no kinetic information is available. Ultrafast techniques rapidly acquire multiple sequences during the first minute of gadolinium contrast injection and provide information about both lesion morphology and vascular kinetics. Diffusion-weighted imaging is a noncontrast MRI technique with the potential to detect mammographically occult cancers. This review article aims to discuss the current indications of breast MRI as a screening tool, examine the standard breast DCE-MRI technique, and explore alternate screening MRI protocols, including Ab-MRI, ultrafast MRI, and noncontrast diffusion-weighted MRI, which can decrease scan time and interpretation time.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

22

Keefer, Daniel, Stefano M. Cavaletto, Jérémy R. Rouxel, Marco Garavelli, Haiwang Yong und Shaul Mukamel. „Ultrafast X-Ray Probes of Elementary Molecular Events“. Annual Review of Physical Chemistry 74, Nr. 1 (24.04.2023): 73–97. http://dx.doi.org/10.1146/annurev-physchem-062322-051532.

Der volle Inhalt der Quelle

Annotation:

Elementary events that determine photochemical outcomes and molecular functionalities happen on the femtosecond and subfemtosecond timescales. Among the most ubiquitous events are the nonadiabatic dynamics taking place at conical intersections. These facilitate ultrafast, nonradiative transitions between electronic states in molecules that can outcompete slower relaxation mechanisms such as fluorescence. The rise of ultrafast X-ray sources, which provide intense light pulses with ever-shorter durations and larger observation bandwidths, has fundamentally revolutionized our spectroscopic capabilities to detect conical intersections. Recent theoretical studies have demonstrated an entirely new signature emerging once a molecule traverses a conical intersection, giving detailed insights into the coupled nuclear and electronic motions that underlie, facilitate, and ultimately determine the ultrafast molecular dynamics. Following a summary of current sources and experiments, we survey these techniques and provide a unified overview of their capabilities. We discuss their potential to dramatically increase our understanding of ultrafast photochemistry.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

23

Qin, Muyang, Xinjing Zhao, Hanyue Fan, Ruizhe Leng, Yanhao Yu, Aiwu Li und Bingrong Gao. „Ultrafast Laser Processing for High-Aspect-Ratio Structures“. Nanomaterials 14, Nr. 17 (31.08.2024): 1428. http://dx.doi.org/10.3390/nano14171428.

Der volle Inhalt der Quelle

Annotation:

Over the past few decades, remarkable breakthroughs and progress have been achieved in ultrafast laser processing technology. Notably, the remarkable high-aspect-ratio processing capabilities of ultrafast lasers have garnered significant attention to meet the stringent performance and structural requirements of materials in specific applications. Consequently, high-aspect-ratio microstructure processing relying on nonlinear effects constitutes an indispensable aspect of this field. In the paper, we review the new features and physical mechanisms underlying ultrafast laser processing technology. It delves into the principles and research achievements of ultrafast laser-based high-aspect-ratio microstructure processing, with a particular emphasis on two pivotal technologies: filamentation processing and Bessel-like beam processing. Furthermore, the current challenges and future prospects for achieving both high precision and high aspect ratios simultaneously are discussed, aiming to provide insights and directions for the further advancement of high-aspect-ratio processing.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

24

Atac, Omer Faruk, Hyunsu Lee und Seoksu Moon. „Detecting ultrafast turbulent oscillations in near-nozzle discharged liquid jet using x-ray phase-contrast imaging with MHz frequency“. Physics of Fluids 35, Nr. 4 (April 2023): 045102. http://dx.doi.org/10.1063/5.0143351.

Der volle Inhalt der Quelle

Annotation:

Characteristics of a discharged liquid jet in near-nozzle are determined by the in-flow turbulences generated by the evolution of inflow vortices and cavitation. High-fidelity simulations have indicated that such physical processes can generate ultrafast turbulent fluctuations (in the range of MHz) originating from the nature of turbulence by the interaction between the large and small-scale turbulence in the flow. Detecting ultrafast turbulent oscillations while resolving small-scale turbulences in the optically dense near-nozzle liquid jet has not been observed through experimental methods so far. In this study, therefore, ultrafast x-ray phase-contrast imaging, which can provide a clear image in the near-field using a high-energy x-ray source, was applied to observe the fluctuation of flow velocity in the near-field to obtain the ultrafast turbulent oscillations at the discharged jet. To capture the ultrafast variance of flow velocity originating from the nature of turbulence, the high imaging frequency was applied up to 1.2 MHz. With the implemented methodology, turbulence intensity distributions of discharged liquid jets were measured for various injection pressures and nozzle geometries. Such turbulence intensity results were also correlated with the initial dispersion angle of the spray. In addition, the turbulence length scales, which can be detected through the current methodology, were estimated and discussed considering standard-length scales. The results showed that the current experimental method introduced in this study can provide important insights into the turbulence characteristics of spray by resolving Taylor scale turbulences and can provide valuable validation data and boundary conditions for reliable spray simulations.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

25

Wang, Lizhong, Huanyu Zhao, Dongyu Zhu, Li Yuan, Hongjun Zhang, Peixun Fan und Minlin Zhong. „A Review on Ultrafast Laser Enabled Excellent Superhydrophobic Anti-Icing Performances“. Applied Sciences 13, Nr. 9 (28.04.2023): 5478. http://dx.doi.org/10.3390/app13095478.

Der volle Inhalt der Quelle

Annotation:

Fabricating and developing superhydrophobic anti-icing surfaces have been a research hotspot for eliminating undesired icing issues. Among various fabricating strategies, ultrafast laser micro-nano fabrication is regarded as a greatly promising technique owing to its advantages of high geometric accuracy, highly flexible microstructure or dimension availability, no contact, and no material limitation. A number of diverse micro-nanostructured superhydrophobic surfaces have been developed by ultrafast lasers and demonstrated extraordinary anti-icing properties. They are collectively known as ultrafast laser-fabricated superhydrophobic anti-icing surfaces (ULSASs). In this article, we reviewed the recent advances in ULSASs from micro-nano structure fabricating to anti-icing performances and to potential applications. The surface wettability and mechanisms of ultrafast laser micro-nano fabrication are first introduced, showing the strong ability of ultrafast laser for fabricating superhydrophobic surfaces. Then the deepened understanding of the relationship between superhydrophobicity and icephobicity is discussed in detail, including Cassie–Baxter stability, surface durability and environmental adaptability. Eventually, the passive anti-icing technique, the passive/active combined anti-icing technique and their practical applications are presented together with current challenges and future prospects.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

26

Omatsu, T., H. J. Kong, S. Park, S. Cha, H. Yoshida, K. Tsubakimoto, H. Fujita et al. „The Current Trends in SBS and phase conjugation“. Laser and Particle Beams 30, Nr. 1 (März 2012): 117–74. http://dx.doi.org/10.1017/s0263034611000644.

Der volle Inhalt der Quelle

Annotation:

AbstractThe current trends in stimulated Brillouin scattering and optical phase conjugation are overviewed. This report is formed by the selected papers presented in the “Fifth International Workshop on stimulated Brillouin scattering and phase conjugation 2010” in Japan. The nonlinear properties of phase conjugation based on stimulated Brillouin scattering and photo-refraction can compensate phase distortions in the high power laser systems, and they will also open up potentially novel laser technologies, e.g., phase stabilization, beam combination, pulse compression, ultrafast pulse shaping, and arbitrary waveform generation.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

27

SNIZHKO, Dmytro. „Ultrafast Potentiostat as Compromise between Current Sensitivity vs. Response Time“. PRZEGLĄD ELEKTROTECHNICZNY 1, Nr. 8 (05.08.2019): 104–9. http://dx.doi.org/10.15199/48.2019.08.24.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

28

Walsh, Martin A., Gwyndaf Evans, Ruslan Sanishvili, Irene Dementieva und Andrzej Joachimiak. „MAD data collection – current trends“. Acta Crystallographica Section D Biological Crystallography 55, Nr. 10 (01.10.1999): 1726–32. http://dx.doi.org/10.1107/s0907444999008392.

Der volle Inhalt der Quelle

Annotation:

The multiwavelength anomalous dispersion (MAD) method of protein structure determination is becoming a routine technique in protein crystallography. The increased number of wavelength-tuneable synchrotron beamlines capable of performing challenging MAD experiments, coupled with the widespread availability of charge-coupled device (CCD) based X-ray detectors with fast read-out times have brought MAD structure determination to a new exciting level. Ultrafast MAD data collection is now possible and, with the widespread use of selenium in the form of selenomethionine for phase determination, the method is growing in popularity. Recent developments in crystallographic software are complementing the above advances, paving the way for rapid protein structure determination. An overview of a typical MAD experiment is described, with emphasis on the rates and quality of data acquisition now achievable at third-generation synchrotron sources.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

29

Wall, Simon, Shan Yang, Luciana Vidas, Matthieu Chollet, James M. Glownia, Michael Kozina, Tetsuo Katayama et al. „Ultrafast disordering of vanadium dimers in photoexcited VO2“. Science 362, Nr. 6414 (01.11.2018): 572–76. http://dx.doi.org/10.1126/science.aau3873.

Der volle Inhalt der Quelle

Annotation:

Many ultrafast solid phase transitions are treated as chemical reactions that transform the structures between two different unit cells along a reaction coordinate, but this neglects the role of disorder. Although ultrafast diffraction provides insights into atomic dynamics during such transformations, diffraction alone probes an averaged unit cell and is less sensitive to randomness in the transition pathway. Using total scattering of femtosecond x-ray pulses, we show that atomic disordering in photoexcited vanadium dioxide (VO2) is central to the transition mechanism and that, after photoexcitation, the system explores a large volume of phase space on a time scale comparable to that of a single phonon oscillation. These results overturn the current understanding of an archetypal ultrafast phase transition and provide new microscopic insights into rapid evolution toward equilibrium in photoexcited matter.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

30

Lin Ke-Sheng, Gao Yu, Zhong Xiao-Qing und Jiang Xiao-Fang. „A method for measuring depth of focus in ultrafast pulsed laser systems based on <i>Z</i>-scan technique“. Acta Physica Sinica 74, Nr. 7 (2025): 0. https://doi.org/10.7498/aps.74.20241658.

Der volle Inhalt der Quelle

Annotation:

As technology advances, ultrafast pulse lasers are increasingly used in a wide range of applications, including material processing, imaging, and medical treatments. The precision of these applications often depends on the ability to focus the laser beam to a tight spot with minimal divergence over a certain range along the optical axis. Therefore, accurate measurement of depth of focus (DOF) is crucial for optimizing the performance of ultrafast laser systems and ensuring the reliability of the results obtained in various experiments and applications. Traditional methods for DOF measurement primarily rely on direct capturing of the beam size, which is impractical in high-intensity environments of ultrafast pulse laser systems due to potential damage to sensors and limitations in measurement accuracy. Furthermore, employing autocorrelation or moving sensors to measure DOF in ultrafast pulse lasers introduces complex optical paths that can lead to measurement errors, making them unreliable for precise focusing applications.<br>To address the limitations of current DOF measurement techniques for ultrafast pulse laser, this paper proposes a novel method based on Z-scan technique. According to nonlinear optical theory, we derive that the transmittance curves obtained from open-aperture (OA) Z-scan measurements of samples exhibiting two-photon absorption (TPA) follows a Lorentzian distribution. By fitting this curve by Lorentzian, the DOF of ultrafast pulse lasers can be determined rapidly to the full width at half maximum (FWHM) of the OA Z-scan curves. We conduct experimental measurements of the transmittance curves of solid and liquid samples with TPA across different types of lenses and microscope objectives within ultrafast optical systems. The results demonstrate a significant consistency between the FWHM of the OA Z-scan curves and the theoretical DOF values. This method effectively correlates the size of the DOF with the beam waist radius derived from the distribution of the Lorentzian function in the OA Z-scan experimental curves, eliminating the influence of other parameters on the measurement results. In conclusion, a novel method for measuring DOF in ultrafast pulse laser systems using the OA Z-scan technique was proposed. It provides a rapid, accurate and reliable way to determine the DOF in ultrafast laser focusing systems, enabling precise control of the ultrafast laser beam for a wide range of applications.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

31

Hutchison, Christopher D. M., und Jasper J. van Thor. „Optical control, selection and analysis of population dynamics in ultrafast protein X-ray crystallography“. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, Nr. 2145 (April 2019): 20170474. http://dx.doi.org/10.1098/rsta.2017.0474.

Der volle Inhalt der Quelle

Annotation:

Ultrafast pump-probe X-ray crystallography has now been established at X-ray free electron lasers that operate at hard X-ray energies. We discuss the performance and development of current applications in terms of the available data quality and sensitivity to detect and analyse structural dynamics. A discussion of technical capabilities expected at future high repetition rate applications as well as future non-collinear multi-pulse schemes focuses on the possibility to advance the technique to the practical application of the X-ray crystallographic equivalent of an impulse time-domain Raman measurement of vibrational coherence. Furthermore, we present calculations of the magnitude of population differences and distributions prepared with ultrafast optical pumping of single crystals in the typical serial femtosecond crystallography geometry, which are developed for the general uniaxial and biaxial cases. The results present opportunities for polarization resolved anisotropic X-ray diffraction analysis of photochemical populations for the ultrafast time domain. This article is part of the theme issue ‘Measurement of ultrafast electronic and structural dynamics with X-rays’.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

32

De Sio, Antonietta, und Christoph Lienau. „Vibronic coupling in organic semiconductors for photovoltaics“. Physical Chemistry Chemical Physics 19, Nr. 29 (2017): 18813–30. http://dx.doi.org/10.1039/c7cp03007j.

Der volle Inhalt der Quelle

Annotation:

Ultrafast two-dimensional electronic spectroscopy reveals vibronically-assisted coherent charge transport and separation in organic materials and opens up new perspectives for artificial light-to-current conversion.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

33

Ramunno, Lora, Esben Witting Larsen, Nan Lin und Amelle Zaïr. „High harmonic generation in condensed and engineered materials: introduction“. Journal of the Optical Society of America B 41, Nr. 6 (31.05.2024): HHG1. http://dx.doi.org/10.1364/josab.531574.

Der volle Inhalt der Quelle

Annotation:

The emerging field of high harmonic generation in condensed matter systems lies at the confluence of strong-field physics, ultrafast optics, and nanotechnology and offers numerous avenues for fundamental research and applications. The goals of this JOSA B feature issue on high harmonic generation in condensed and engineered materials are to facilitate interaction between the different communities and to provide an up-to-date snapshot of the current status of this rapidly developing interdisciplinary field at the frontier of condensed materials and ultrafast physics.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

34

Penilla, E. H., L. F. Devia-Cruz, A. T. Wieg, P. Martinez-Torres, N. Cuando-Espitia, P. Sellappan, Y. Kodera, G. Aguilar und J. E. Garay. „Ultrafast laser welding of ceramics“. Science 365, Nr. 6455 (22.08.2019): 803–8. http://dx.doi.org/10.1126/science.aaw6699.

Der volle Inhalt der Quelle

Annotation:

Welding of ceramics is a key missing component in modern manufacturing. Current methods cannot join ceramics in proximity to temperature-sensitive materials like polymers and electronic components. We introduce an ultrafast pulsed laser welding approach that relies on focusing light on interfaces to ensure an optical interaction volume in ceramics to stimulate nonlinear absorption processes, causing localized melting rather than ablation. The key is the interplay between linear and nonlinear optical properties and laser energy–material coupling. The welded ceramic assemblies hold high vacuum and have shear strengths comparable to metal-to-ceramic diffusion bonds. Laser welding can make ceramics integral components in devices for harsh environments as well as in optoelectronic and/or electronic packages needing visible-radio frequency transparency.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

35

JEONG, Young Uk, Kitae LEE, Kyu-Ha JANG, In Hyung BAEK, Hyun Woo KIM und Key Young OANG. „Jitter-free Ultrafast Electron Diffraction Technology“. Physics and High Technology 31, Nr. 11 (30.11.2022): 20–26. http://dx.doi.org/10.3938/phit.31.045.

Der volle Inhalt der Quelle

Annotation:

We introduce on ultrafast electron diffraction (UED) technology that observes the movement of fast-moving atoms. Recently the Korea Atomic Energy Research Institute has built the fastest electron diffraction facility in the world with the achievements of increasing beam brightness and improving temporal accuracy with jitter-free technology. We introduce the unique characteristics of the device with 90-degree-bending structure and conclude with the current status and prospects of the UED and its applications.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

36

Khaing, Zin Z., Lindsay N. Cates, Dane M. DeWees, Alexander Hannah, Pierre Mourad, Matthew Bruce und Christoph P. Hofstetter. „Contrast-enhanced ultrasound to visualize hemodynamic changes after rodent spinal cord injury“. Journal of Neurosurgery: Spine 29, Nr. 3 (September 2018): 306–13. http://dx.doi.org/10.3171/2018.1.spine171202.

Der volle Inhalt der Quelle

Annotation:

OBJECTIVETraumatic spinal cord injury (tSCI) causes an almost complete loss of blood flow at the site of injury (primary injury) as well as significant hypoperfusion in the penumbra of the injury. Hypoperfusion in the penumbra progresses after injury to the spinal cord and is likely to be a major contributor to progressive cell death of spinal cord tissue that was initially viable (secondary injury). Neuroprotective treatment strategies seek to limit secondary injury. Clinical monitoring of the temporal and spatial patterns of blood flow within the contused spinal cord is currently not feasible. The purpose of the current study was to determine whether ultrafast contrast-enhanced ultrasound (CEUS) Doppler allows for detection of local hemodynamic changes within an injured rodent spinal cord in real time.METHODSA novel ultrafast CEUS Doppler technique was developed utilizing a research ultrasound platform combined with a 15-MHz linear array transducer. Ultrafast plane-wave acquisitions enabled the separation of higher-velocity blood flow in macrocirculation from low-velocity flow within the microcirculation (tissue perfusion). An FDA-approved contrast agent (microbubbles) was used for visualization of local blood flow in real time. CEUS Doppler acquisition protocols were developed to characterize tissue perfusion both during contrast inflow and during the steady-state plateau. A compression injury of the thoracic spinal cord of adult rats was induced using iris forceps.RESULTSHigh-frequency ultrasound enabled visualization of spinal cord vessels such as anterior spinal arteries as well as central arteries (mean diameter [± SEM] 145.8 ± 10.0 µm; 76.2 ± 4.5 µm, respectively). In the intact spinal cord, ultrafast CEUS Doppler confirmed higher perfusion of the gray matter compared to white matter. Immediately after compression injury of the thoracic rodent spinal cord, spinal cord vessels were disrupted in an area of 1.93 ± 1.14 mm2. Ultrafast CEUS Doppler revealed a topographical map of local tissue hypoperfusion with remarkable spatial resolution. Critical loss of perfusion, defined as less than 40% perfusion compared to the surrounding spared tissue, was seen within an area of 2.21 ± 0.6 mm2.CONCLUSIONSIn our current report, we introduce ultrafast CEUS Doppler for monitoring of spinal vascular structure and function in real time. Development and clinical implementation of this type of imaging could have a significant impact on the care of patients with tSCI.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

37

TIAN, YE, FAN YANG, CHAOYU GUO und YING JIANG. „RECENT ADVANCES IN ULTRAFAST TIME-RESOLVED SCANNING TUNNELING MICROSCOPY“. Surface Review and Letters 25, Supp01 (Dezember 2018): 1841003. http://dx.doi.org/10.1142/s0218625x18410032.

Der volle Inhalt der Quelle

Annotation:

Making smaller and faster functional devices has led to an increasing demand for a microscopic technique that allows the investigation of carrier and phonon dynamics with both high spatial and temporal resolutions. Traditional optical pump–probe methods can achieve femtosecond temporal resolution but fall short in the spatial resolution due to the diffraction limit. Scanning tunneling microscopy (STM), on the contrary, has realized atomic-scale spatial resolution relying on the high sensitivity of the tunneling current to the tip-sample distance. However, limited by the electronics bandwidth, STM can only push the temporal resolution to the microseconds scale, restricting its applications to probe various ultrafast dynamic processes. The combination of these two methods takes advantages of optical pump–probe techniques and highly localized tunneling currents of STM, providing one viable solution to track atomic-scale ultrafast dynamics in single molecules and low-dimensional materials. In this review, we will focus on several ultrafast time-resolved STM methods by coupling the tunneling junctions with pulsed electric waves, THz, near-infrared and visible laser. Their applications to probe the carrier dynamics, spin dynamics, and molecular motion will be highlighted. In the end, we will present an outlook on the challenges and new opportunities in this field.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

38

Garming, Mathijs W. H., I. Gerward C. Weppelman, Martin Lee, Thijs Stavenga und Jacob P. Hoogenboom. „Ultrafast scanning electron microscopy with sub-micrometer optical pump resolution“. Applied Physics Reviews 9, Nr. 2 (Juni 2022): 021418. http://dx.doi.org/10.1063/5.0085597.

Der volle Inhalt der Quelle

Annotation:

Ultrafast scanning electron microscopy images carrier dynamics and carrier induced surface voltages using a laser pump electron probe scheme, potentially surpassing all-optical techniques in probe resolution and surface sensitivity. Current implementations have left a four order of magnitude gap between optical pump and electron probe resolution, which particularly hampers spatial resolution in the investigation of carrier induced local surface photovoltages. Here, we present a system capable of focusing the laser using an inverted optical microscope built into an ultrafast scanning electron microscopy setup to enable high numerical aperture pulsed optical excitation in conjunction with ultrafast electron beam probing. We demonstrate an order of magnitude improvement in optical pump resolution, bringing this to sub-micrometer length scales. We further show that temporal laser pump resolution can be maintained inside the scanning electron microscope by pre-compensating dispersion induced by the components required to bring the beam into the vacuum chamber and to a tight focus. We illustrate our approach using molybdenum disulfide, a two-dimensional transition metal dichalcogenide, where we measure ultrafast carrier relaxation rates and induced negative surface potentials between different flakes selected with the scanning electron microscope as well as on defined positions within a single flake.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

39

Wang, Fei Fei, und B. Wang. „Current Research Progress in Non-Classical Fourier Heat Conduction“. Applied Mechanics and Materials 442 (Oktober 2013): 187–96. http://dx.doi.org/10.4028/www.scientific.net/amm.442.187.

Der volle Inhalt der Quelle

Annotation:

Classical Fourier law can accurately describe most heat conduction problems. But for ultrafast heat conduction process and micro/nanoscale heat conduction problems, non-classical Fourier (non-Fourier) effect may become dominated. The paper gives a review on the current progress on non-Fourier heat conduction in engineering. It includes basic concept, physical models, thermal relaxation effect, and related experiments. Also introduced are the solution methods of non-Fourier heat conduction equations, including closed-form solution, finite difference method, finite element method, molecular dynamics simulation, variational method, and other hybrid methods. Some challenging issues are discussed at the conclusion of the paper.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

40

Kanno, Manabu, Hirohiko Kono und Yuichi Fujimura. „Laser-Control of Ultrafast π-Electron Ring Currents in Aromatic Molecules: Roles of Molecular Symmetry and Light Polarization“. Applied Sciences 8, Nr. 12 (22.11.2018): 2347. http://dx.doi.org/10.3390/app8122347.

Der volle Inhalt der Quelle

Annotation:

Being motivated by the recent progress in attosecond laser technology, we theoretically explore the strategy of inducing ultrafast electron dynamics inherent to aromatic molecules, i.e., ring currents by means of polarized laser pulses. The main topic of discussion is how to control the direction of ring currents in an aromatic molecule of low symmetry, for which the design of an efficient control pulse cannot be achieved intuitively. We first consider a system with a single aromatic ring and show that coherent π-electron angular momentum, which oscillates with time, can be produced and controlled by a polarized laser pulse with its ellipticity and orientation properly chosen. Nonadiabatic couplings with molecular vibration gradually weaken the angular momentum, while the vibrational amplitude strongly depends on the polarization of incident light. This suggests the conversion of the polarization dependence of ring current into that of subsequent vibration, which may open a way to detect laser-driven ultrafast electron dynamics by vibrational spectroscopy. The laser-control scheme for the ring current is then extended to a molecule with two aromatic rings, which exhibits characteristic phenomena absent in that with a single ring. We demonstrate that two-dimensional switching of the direction of angular momentum is possible in such molecules. In addition, ring current can be localized at a specific ring by tailored lasers. The application of the present control method to polycyclic aromatic hydrocarbons will lead to the development of next-generation organic optical switching devices.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

41

Seifert, Tom S., Liang Cheng, Zhengxing Wei, Tobias Kampfrath und Jingbo Qi. „Spintronic sources of ultrashort terahertz electromagnetic pulses“. Applied Physics Letters 120, Nr. 18 (02.05.2022): 180401. http://dx.doi.org/10.1063/5.0080357.

Der volle Inhalt der Quelle

Annotation:

Spintronic terahertz emitters are broadband and efficient sources of terahertz radiation, which emerged at the intersection of ultrafast spintronics and terahertz photonics. They are based on efficient spin-current generation, spin-to-charge-current conversion, and current-to-field conversion at terahertz rates. In this Editorial, we review the recent developments and applications, the current understanding of the physical processes, and the future challenges and perspectives of broadband spintronic terahertz emitters.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

42

Abdul-Hussain, Muhaiman Ali, und Haidar J. Mohamad. „Thermal Effect in a 3-D Simulation within Multilayer Thin Film of Ultrafast-Pulsed Laser“. Al-Mustansiriyah Journal of Science 32, Nr. 4 (20.11.2021): 104–9. http://dx.doi.org/10.23851/mjs.v32i4.1039.

Der volle Inhalt der Quelle

Annotation:

Hard disk drive (HDD) and storage media have the potential to revolutionize future information technology. Heat-assisted magnetic recording (HAMR) is a promising method for increasing hard disk storage density and it is one of the applications of this study. The essential component of nanoscale spintronic devices is spin current. The simulation of a thermal gradient to generate a pure spin current using an ultrafast femtosecond (fs) laser in a multilayer thin film is presented. The trilayer sample (ferromagnetic/spacer/magnetic insulator) is the candidate to achieve the spin current. Ultrafast laser with fs pulse width simulated to creates a spin diffusion spark. These pulses penetrate within the trilayer reaching the magnetic insulator due to the penetration depth that record the effect. COMSOL Multiphysics software® is used to simulate the thermal behavior within the trilayer with three-dimensional (3-D) view. The thickness of the ferromagnetic layer (Ni81Fe19) has been shown to generate a high-temperature gradient within the magnetic insulator and therefore a larger spin current.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

43

Khovrin, V. V., T. N. Galyan, M. V. Malakhova, Z. R. Khachatrian und E. R. Charchian. „“Ultrafast” Multispiral Computer Tomographic Angiography of Aorta: Current Reality and Perspectives“. Medical Visualization, Nr. 4 (28.08.2017): 33–40. http://dx.doi.org/10.24835/1607-0763-2017-4-33-40.

Der volle Inhalt der Quelle

Annotation:

Objective: to carried out the comparison of the data of MDCT of the patients, undergoing screening using the standard protocol MDCT aortography and FLASH “fast” protocol of scanning. It is discussed the possibility of the reduction of the injected amount of the contrast agent for “fast” aortography.Materials and methods. The aorta examinations of 101 patients (69 men (68%) and 32 women (32%); the average age ± the standard deviation – 56.34 ± 11.5 years) were analyzed. The examinations have been carried out on MDCT with two sources of Х-ray (DSCT); 48 patients have been undergone the examination using “fast” FLASH scanning. It has been compared the scanning time, the length of the examination zone and ED (Effective Dose) load calculated for the groups for the standard and “fast” MDCT aortography.Results. CDTIvol and DLP values were statistically proved lower (p < 0.001) at the examination of the patients that had been undergone “fast” protocol of scanning FLASH. The average ED was considerably lower in this group of the patients in comparison with the patients that had been examined using standard protocol (4.36 ± 1.69 mSv and 15.12 ± 4.62 mSv, р < 0.001). Without the reliable difference in the length of the examination zone in groups (42.91 ± 3.23 cm and 43.68 ± 2.66 cm, p = 0.55), the duration of the examination of MDCT aorta was considerably lower in the second group (9.29 ± 0.85s and 1.93 ± 0.12 s, p < 0.001). Conclusion. The method of the superfast aorta МDCT make it possible to reduce ED and the amount of the injected contrast agent at the examination of the vast zone. At the same time, qualitative and quantitative analysis of the MDCT remains high.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

44

Trohalaki, Steven. „Computational Model Shows Stark Shifts Induce Ultrafast Current in Molecular Wires“. MRS Bulletin 32, Nr. 11 (November 2007): 882–83. http://dx.doi.org/10.1557/mrs2007.176.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

45

Moskalenko, A. S., A. Matos-Abiague und J. Berakdar. „Photoinduced indirect transitions and ultrafast direct current generation in unbiased superlattices“. Physics Letters A 356, Nr. 4-5 (August 2006): 255–61. http://dx.doi.org/10.1016/j.physleta.2006.03.061.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

46

Wei, Fanrong, Zhiqiang Wan, Haibo He und Xiangning Lin. „Ultrafast Active Response Strategy against Malfunction Attack on Fault Current Limiter“. IEEE Transactions on Smart Grid 11, Nr. 3 (Mai 2020): 2722–33. http://dx.doi.org/10.1109/tsg.2019.2960459.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

47

Polley, Debanjan, Akshay Pattabi, Jyotirmoy Chatterjee, Sucheta Mondal, Kaushalya Jhuria, Hanuman Singh, Jon Gorchon und Jeffrey Bokor. „Progress toward picosecond on-chip magnetic memory“. Applied Physics Letters 120, Nr. 14 (04.04.2022): 140501. http://dx.doi.org/10.1063/5.0083897.

Der volle Inhalt der Quelle

Annotation:

We offer a perspective on the prospects of ultrafast spintronics and opto-magnetism as a pathway to high-performance, energy-efficient, and non-volatile embedded memory in digital integrated circuit applications. Conventional spintronic devices, such as spin-transfer-torque magnetic-resistive random-access memory (STT-MRAM) and spin–orbit torque MRAM, are promising due to their non-volatility, energy-efficiency, and high endurance. STT-MRAMs are now entering into the commercial market; however, they are limited in write speed to the nanosecond timescale. Improvement in the write speed of spintronic devices can significantly increase their usefulness as viable alternatives to the existing CMOS-based devices. In this article, we discuss recent studies that advance the field of ultrafast spintronics and opto-magnetism. An optimized ferromagnet–ferrimagnet exchange-coupled magnetic stack, which can serve as the free layer of a magnetic tunnel junction (MTJ), can be optically switched in as fast as ∼3 ps. Integration of ultrafast magnetic switching of a similar stack into an MTJ device has enabled electrical readout of the switched state using a relatively larger tunneling magnetoresistance ratio. Purely electronic ultrafast spin–orbit torque induced switching of a ferromagnet has been demonstrated using ∼6 ps long charge current pulses. We conclude our Perspective by discussing some of the challenges that remain to be addressed to accelerate ultrafast spintronics technologies toward practical implementation in high-performance digital information processing systems.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

48

Cao, Xueqin, Yuanyuan Huang, Yayan Xi, Zhen Lei, Wanyi Du, Taotao Han, Jing Wang et al. „Interplay between Ultrafast Shift Current and Ultrafast Photon Drag Current in Tellurium Nanotubes“. ACS Photonics, 29.08.2022. http://dx.doi.org/10.1021/acsphotonics.2c00993.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

49

Wilson, Richard B., Yang Yang, Jon Gorchon, Charles-Henri Lambert, Sayeef Salahuddin und Jeffrey Bokor. „Electric current induced ultrafast demagnetization“. Physical Review B 96, Nr. 4 (07.07.2017). http://dx.doi.org/10.1103/physrevb.96.045105.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

50

Lv, Yinchuan, Soho Shim, Jonathan Gibbons, Axel Hoffmann, Nadya Mason und Fahad Mahmood. „Ultrafast THz emission spectroscopy of spin currents in the metamagnet FeRh“. APL Materials 12, Nr. 4 (01.04.2024). http://dx.doi.org/10.1063/5.0201789.

Der volle Inhalt der Quelle

Annotation:

Heterostructures of ferromagnetic (FM) and noble metal (NM) thin films have recently attracted considerable interest as viable platforms for the ultrafast generation, control, and transduction of light-induced spin currents. In such systems, an ultrafast laser can generate a transient spin current in the FM layer, which is then converted to a charge current at the FM/NM interface due to strong spin–orbit coupling in the NM layer. Whether such conversion can happen in a single material and how the resulting spin current can be quantified are open questions under active study. Here, we report ultrafast THz emission from spin–charge conversion in a bare FeRh thin film without any NM layer. Our results highlight that the magnetic material by itself can enable spin–charge conversion in the same order as that in a FM/NM heterostructure. We further propose a simple model to estimate the light-induced spin current in FeRh across its metamagnetic phase transition temperature. Our findings have implications for the study of the ultrafast dynamics of magnetic order in quantum materials using THz emission spectroscopy.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Zeitschriftenartikel zum Thema „Ultrafast current“

Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an