Journal articles: 'Ultrafast Pulse'

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Liu, Yongshan, Houyi Cheng, Pierre Vallobra, Huiwen Wang, Sylvain Eimer, Xiaoqiang Zhang, Gregory Malinowski, et al. "Ultrafast single-pulse switching of Tb-dominant CoTb alloy." Applied Physics Letters 122, no. 2 (January 9, 2023): 022401. http://dx.doi.org/10.1063/5.0131716.

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Single-pulse magnetization switching by femtosecond laser pulses is the fastest way to manipulate magnetization. To date, among rare-earth transition metal alloys, single-pulse switching is limited to Gd-based structures. Here, we demonstrate ultrafast single-pulse switching of Tb-dominant CoTb alloys within several tens of picoseconds. Our further analysis shows that the ultrafast magnetization reversal is linked to ultrafast heating of laser pulses and an external field.

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Garming, Mathijs W. H., Pieter Kruit, and Jacob P. Hoogenboom. "Imaging resonant micro-cantilever movement with ultrafast scanning electron microscopy." Review of Scientific Instruments 93, no. 9 (September 1, 2022): 093702. http://dx.doi.org/10.1063/5.0089086.

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Here, we demonstrate ultrafast scanning electron microscopy (SEM) for making ultrafast movies of mechanical oscillators at resonance with nanoscale spatiotemporal resolution. Locking the laser excitation pulse sequence to the electron probe pulses allows for video framerates over 50 MHz, well above the detector bandwidth, while maintaining the electron beam resolution and depth of focus. The pulsed laser excitation is tuned to the oscillator resonance with a pulse frequency modulation scheme. We use an atomic force microscope cantilever as a model resonator, for which we show ultrafast real-space imaging of the first and even the 2 MHz second harmonic oscillation as well as verification of power and frequency response via the ultrafast movies series. We detect oscillation amplitudes as small as 20 nm and as large as 9 μm. Our implementation of ultrafast SEM for visualizing nanoscale oscillatory dynamics adds temporal resolution to the domain of SEM, providing new avenues for the characterization and development of devices based on micro- and nanoscale resonant motion.

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Zeng, Li, Xiaofan Wang, Yifan Liang, Huaiqian Yi, Weiqing Zhang, and Xueming Yang. "Chirped-Pulse Amplification in an Echo-Enabled Harmonic-Generation Free-Electron Laser." Applied Sciences 13, no. 18 (September 14, 2023): 10292. http://dx.doi.org/10.3390/app131810292.

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The field of ultrafast science has experienced significant growth over the last decade, largely attributed to advancements in optical and laser technologies such as chirped-pulse amplification and high-harmonic generation. The distinctive characteristics of intense ultrafast free-electron lasers (FELs) have introduced novel prospects for investigating molecular dynamics, as well as providing an opportunity to gain deeper insights into nonlinear processes in materials. Therefore, high-power ultrafast FELs can be widely used for both fundamental research and practical applications. This study presents a novel approach for producing high-power femtosecond FEL pulses, utilizing chirped-pulse amplification in echo-enabled harmonic generation. Chirped seed pulses are employed to induce frequency-chirped energy modulation in the electron beam. The generated FEL pulse, which inherits the chirped frequency, can be compressed through the gratings in the off-plane mount geometry to provide ultraintense ultrafast pulses. The numerical modeling results indicate that peak power exceeding 20 GW and a pulse duration in the order of several femtoseconds can be achieved.

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Xu, Hantao, Baiyu Liu, Yongsheng Gou, Jinshou Tian, Yang Yang, Penghui Feng, Xu Wang, and Shiduo Wei. "Research on Triode Based High Re−Frequency Ultrafast Electrical Pulse Generation Technology." Electronics 12, no. 8 (April 21, 2023): 1950. http://dx.doi.org/10.3390/electronics12081950.

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The high−repeat frequency ultrafast electrical pulse generation technology is mainly based on ultrafast switching devices combined with ultrafast circuits to generate electrical pulses with repetition frequencies of several kilohertz and a rise−time of nanoseconds or even picoseconds. This technology is the basis for several research studies and is one of the key technologies that has received wide attention from various countries. The problems to be solved are high re−frequency ultrafast high−voltage pulse generation and ultra−broadband ultrafast pulse transport and circuit stability applicability, which include circuit conduction mechanism research, pulse generation time improvement and recovery time reduction. By studying the avalanche transistor high−voltage transient conduction characteristics and reducing the loss in the carrier transport process, the influence of each parameter on the output is determined, and the key factors to enhance the circuit performance are identified. This paper designs a new high−repetition frequency ultrafast electric pulse generation (UPG) circuit using pure electronics components, which consists of combining avalanche transistor model 2N2222 with a hybrid Marx structure at the same time in the pulse circuit to add filtering, fast recovery diodes and pulse cutoff and other matching techniques to make its output more stable, which can obtain higher output frequency, faster rise−time and narrower pulse widths. It has been tested that a high re−frequency ultrafast high−voltage electrical pulse signal with a pulse repetition frequency of 200 kHz, a leading edge of 800 ps, a half−high pulse width of 5 ns, an amplitude of 1.2 kV and jitter of less than 5% can be generated at the load with a 50 Ω load at the output. The signal can be applied in the fields of ultrafast diagnosis, information countermeasures and nuclear electromagnetic radiation research.

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Tang, Ziwen, Zihua Zheng, Boyao Li, Zhiyi Wei, and Jinghua Sun. "Applications of Microstructured Optical Fibers in Ultrafast Optics: A Review." Photonics 11, no. 2 (February 5, 2024): 151. http://dx.doi.org/10.3390/photonics11020151.

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With the development of laser technology, microstructured optical fibers (MOFs) have become an important part of ultrafast optics, providing excellent platforms for ultrafast laser pulse generation, amplification, and compression, promoting the development of fiber laser systems to generate high power, high pulse energy, and few-cycle duration pulses. MOFs extend the ultrafast laser spectrum to the vacuum ultraviolet (VUV) and even extreme ultraviolet (EUV) regions based on dispersive wave emission and high harmonic generation, as well as to the mid-infrared region based on soliton self-frequency shift (SSFS), contributing compact and low-cost light sources for precision microscopy and spectroscopy. In this paper, first several common types of MOFs are introduced, then the various applications of MOFs in ultrafast optics are discussed, mainly focusing on the aspects of ultrafast laser pulse scaling in pulse energy and spectral bandwidth, and finally the possible prospects of MOFs are given.

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Wei, Xianqi, Xiaoli Wang, Xin Li, and Weihua Liu. "Electronic Pulses from Pulsed Field Emission of CNT Cathodes." Journal of Nanomaterials 2018 (2018): 1–6. http://dx.doi.org/10.1155/2018/4396430.

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We presented a demonstration of infrared laser irradiated field emission electronic pulse based on carbon nanotube (CNT) cathodes. Electronic pulses greatly depended on pulsed infrared laser and were almost synchronous with laser pulses. We have designed a pulsed field emission cathode based on CNTs and investigated correlation between electronic pulse and laser pulse, acquiring the shortest width of electronic pulses about 50 ms and turn-on field less than 0.14 V/μm. Besides, we have studied the thermal effect on the pulsed field emission of CNT cathodes caused by laser heating. Interestingly, the thermal effect has caused an enhancement of emission current but resulted in a waveform distortion on short electronic pulses. The application of laser pulses on CNT cathodes would extend conventional electron sources to a pulsed electron source and offered a possibility of pulsed field emission. These results were encouraging us to prepare further studies of ultrafast electronic pulses for high-frequency electron sources.

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Lyu, Wenhao, Yuan Cheng, Jiayi An, Marcello Condorelli, Mario Pulvirenti, Giuseppe Compagnini, Xiaogang Wang, Bo Fu, and Vittorio Scardaci. "Silver Nanoplate Composites as Nonlinear Saturable Absorbers for a Q-Switched Laser." Photonics 9, no. 11 (November 7, 2022): 835. http://dx.doi.org/10.3390/photonics9110835.

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Metal nanomaterials have promising applications in ultrafast photonics due to their broadband operation, large third-order nonlinear susceptibility, and ultrafast recovery time. We realized a Q-switched pulsed erbium-doped fiber laser based on a silver nanoplate polyvinyl alcohol film as a saturable absorber. This film, with a modulation depth of 15.7%, was integrated into a fiber laser by means of a sandwich structure. We obtained Q-switched pulses in the 1.5-μm band, which plays an important role in telecommunications and atmospheric detection. Stable Q-switched pulses were obtained at the pump power of 135 mW, with a single pulse energy of 33.8 nJ, a pulse width of 2.3 μs, a repetition rate of 62.4 kHz, and a signal-to-noise ratio of about 45 dB. When increasing the pump power up to a maximum value of 246 mW, the maximum single pulse energy of 57.8 nJ was achieved. This study first demonstrates the potential of silver nanoplates as saturable absorbers in generating stable laser pulses with high energy.

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Cai, Houzhi, Kaixuan Lin, Qiuyan Luo, Dong Wang, Junkun Huang, Kangjing Xu, Longjie Luo, and Jinyuan Liu. "Two-Dimensional Ultrafast X-ray Imager for Inertial Confinement Fusion Diagnosis." Photonics 9, no. 5 (April 22, 2022): 287. http://dx.doi.org/10.3390/photonics9050287.

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A two-dimensional ultrafast X-ray imager (UXI) composed of a time-dilation device, an electron-beam imaging unit, a gated microchannel plate (MCP) framing tube, and a pulser was developed. The time-dilation device extends the time spread of the electron signal generated by the pulsed photocathode (PC), and the electron-beam imaging unit images the electron pulse from PC to MCP. Finally, the gated MCP framing tube samples the dilated electron pulse. The time resolution and image size of the UXI were measured with an X-ray generated by a terawatt laser targeting device. When a driving pulse with a 2 V/ps slope is applied to the PC, the measured time resolution is 21 ps, and the image size is 12 mm × 3.9 mm. Furthermore, the image size varies with the time resolution. The results show that as the time resolution improves, the image size decreases. The use of two opposite-transmission PC driving pulses could improve the image size. Moreover, the measured UXI spatial resolution is 5 lp/mm, and the spatial resolution will be worse with the increasing off-axis distance.

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Yang, Jinfeng, Takafumi Kondoh, Koichi Kan, and Yoichi Yoshida. "Ultrafast pulse radiolysis." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 629, no. 1 (February 2011): 6–10. http://dx.doi.org/10.1016/j.nima.2010.11.109.

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Horiuchi, Noriaki. "Ultrafast pulse switching." Nature Photonics 11, no. 6 (June 2017): 331. http://dx.doi.org/10.1038/nphoton.2017.88.

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Wang, Feihu, Xiaoqiong Qi, Zhichao Chen, Manijeh Razeghi, and Sukhdeep Dhillon. "Ultrafast Pulse Generation from Quantum Cascade Lasers." Micromachines 13, no. 12 (November 24, 2022): 2063. http://dx.doi.org/10.3390/mi13122063.

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Quantum cascade lasers (QCLs) have broken the spectral barriers of semiconductor lasers and enabled a range of applications in the mid-infrared (MIR) and terahertz (THz) regimes. However, until recently, generating ultrashort and intense pulses from QCLs has been difficult. This would be useful to study ultrafast processes in MIR and THz using the targeted wavelength-by-design properties of QCLs. Since the first demonstration in 2009, mode-locking of QCLs has undergone considerable development in the past decade, which includes revealing the underlying mechanism of pulse formation, the development of an ultrafast THz detection technique, and the invention of novel pulse compression technology, etc. Here, we review the history and recent progress of ultrafast pulse generation from QCLs in both the THz and MIR regimes.

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Lu, Yan, Zheng Zhou, Xuefen Kan, Zixin Yang, Haiqin Deng, Bin Liu, Tongtong Wang, et al. "Quasi-2D Mn3Si2Te6 Nanosheet for Ultrafast Photonics." Nanomaterials 13, no. 3 (February 2, 2023): 602. http://dx.doi.org/10.3390/nano13030602.

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The magnetic nanomaterial Mn3Si2Te6 is a promising option for spin-dependent electronic and magneto-optoelectronic devices. However, its application in nonlinear optics remains fanciful. Here, we demonstrate a pulsed Er-doped fiber laser (EDFL) based on a novel quasi-2D Mn3Si2Te6 saturable absorber (SA) with low pump power at 1.5 μm. The high-quality Mn3Si2Te6 crystals were synthesized by the self-flux method, and the ultrathin Mn3Si2Te6 nanoflakes were prepared by a simple mechanical exfoliation procedure. To the best of our knowledge, this is the first time laser pulses have been generated using quasi-2D Mn3Si2Te6. A stable pulsed laser at 1562 nm with a low threshold pump power of 60 mW was produced by integrating the Mn3Si2Te6 SA into an EDFL cavity. The maximum power of the output pulse is 783 μW. The repetition rate can vary from 24.16 to 44.44 kHz, with corresponding pulse durations of 5.64 to 3.41 µs. Our results indicate that the quasi-2D Mn3Si2Te6 is a promising material for application in ultrafast photonics.

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Zhang, Zhicheng, Sha Wang, Xingwen Hu, Bangguo Wang, and Jun Wang. "Ultrafast ytterbium-doped all-fiber laser with vortex pulse emissions." Laser Physics Letters 19, no. 3 (February 9, 2022): 035103. http://dx.doi.org/10.1088/1612-202x/ac4e8e.

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Abstract Ultrafast vortex pulses emitted at 1 μm band are highly sought after in many fields, here we propose an all-fiber laser for achieving that. The designed laser is switchable to emit ultrafast orbital angular momentum (OAM) and cylindrical vector beams. The beam purities are calculated to be higher than 94%. Moreover, the as-designed laser can achieve ultrafast pulse with a duration of 10.4 ps and maximum energy of 619.3 pJ. Generally, it is the shortest width and largest energy of OAM emission in ultrafast ytterbium-doped all-fiber laser so far.

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Alves, Joana, Hugo Pires, Celso P. João, and Gonçalo Figueira. "Multi-mJ Scaling of 5-Optical Cycle, 3 µm OPCPA." Photonics 8, no. 11 (November 9, 2021): 503. http://dx.doi.org/10.3390/photonics8110503.

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We present the design of an ultrafast optical parametric chirped pulse amplifier (OPCPA) operating at 3 µm yielding few-cycle pulses and multi-mJ output energy. This design demonstrates that with a configuration of a single crystal or combination of crystals (KTA and MgO:LN) it is possible to achieve output energies above the mJ with sufficient bandwidth to allow compression to just 5-optical cycles. Here, we consider a 1 µm mJ-level picosecond chirped pulse amplifier (CPA), a typical pumping source for this type of non-linear amplifiers. Compression with a simple bulk material enables reaching close to the pulse Fourier-transform limited duration, paving the way to high energy, ultrafast mid-infrared pulses.

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Porras, Miguel A. "Effects of the Coupling between the Orbital Angular Momentum and the Temporal Degrees of Freedom in the Most Intense Ring of Ultrafast Vortices." Applied Sciences 10, no. 6 (March 12, 2020): 1957. http://dx.doi.org/10.3390/app10061957.

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It has recently been shown that the temporal and the orbital angular momentum (OAM) degrees of freedom in ultrafast (few-cycle) vortices are coupled. This coupling manifests itself with different effects in different parts of the vortex, as has been shown for the ring surrounding the vortex where the pulse energy is maximum, and also in the immediate vicinity of the vortex center. However, in many applications, the ring of maximum energy is not of primary interest, but the one where the peak intensity of the pulse is maximum, which is particularly true in nonlinear optics applications such as experiments with ultrafast vortices that excite high harmonics and attosecond pulses that also carry OAM. In this paper, the effects of the OAM-temporal coupling on the ring of maximum pulse peak intensity, which do not always coincide with the ring of maximum pulse energy, are described. We find that there is an upper limit to the magnitude of the topological charge that an ultrafast vortex with a prescribed pulse shape in its most intense ring can carry, and vice versa, a lower limit to the pulse duration in the most intense ring for a given magnitude of the topological charge. These limits imply that, with a given laser source spectrum, the duration of the synthesized ultrafast vortex increases with the magnitude of the topological charge. Explicit analytical expressions are given for the ultrafast vortices that contain these OAM-temporal couplings effects, which may be of interest in various applications, in particular in the study of their propagation and interaction with matter.

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Wang, Hongjie, Dmitry Gaponov, Amélie Cabasse, Gilles Martel, Ammar Hideur, Jean-Louis Oudar, Leonid Kotov, Mikhail Likhachev, Denis Lipatov, and Sébastien Février. "1.55-μm wavelength ultrafast fiber oscillators and amplifiers." International Journal of Modern Physics B 28, no. 12 (April 7, 2014): 1442004. http://dx.doi.org/10.1142/s0217979214420041.

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In this paper, we review our recent developments on ultrafast pulse generation in erbium-doped fiber laser systems operating in the 1550 nm wavelength range. This work concerns the generation of ultrafast pulses from dissipative soliton fiber lasers featuring resonant saturable absorber mirrors, as well as their amplification in highly efficient erbium-doped large-mode-area fibers. Different amplification schemes featuring all-fiber components are studied leading to the achievement of record pulse energy from a high repetition rate laser system.

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Taft, Gregory J., Matthew T. Newby, Joel J. Hrebik, Marshall Onellion, Thomas F. George, Dániel Szentesi, Sándor Szatmári, and László Nánai. "Ultrafast dynamic reflectivity of vanadium pentoxide." Journal of Materials Research 23, no. 2 (February 2008): 308–11. http://dx.doi.org/10.1557/jmr.2008.0039.

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The ultrafast dynamic reflectivity of vanadium pentoxide is measured using 40 fs pulses from a self-mode-locked Ti:sapphire laser. The laser pulses excite acoustic vibrations at wave numbers of 145 and 103 cm−1. The amplitudes of the induced oscillations depend strongly on the orientation between the linear polarization of the laser pulses and the crystal axes, with the largest oscillations observed for an orientation of 45°. The higher-frequency oscillation is induced immediately upon arrival of the laser pulse, while the lower-frequency oscillation appears a few picoseconds later. The oscillations persist for approximately 10 ps after the arrival of the pulse. The oscillations are attributed to transverse acoustic modes propagating along the a-axis of the crystal.

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Zia, Haider. "Maintaining Constant Pulse-Duration in Highly Dispersive Media Using Nonlinear Potentials." Photonics 8, no. 12 (December 11, 2021): 570. http://dx.doi.org/10.3390/photonics8120570.

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A method is shown for preventing temporal broadening of ultrafast optical pulses in highly dispersive and fluctuating media for arbitrary signal-pulse profiles. Pulse pairs, consisting of a strong-field control-pulse and a weak-field signal-pulse, co-propagate, whereby the specific profile of the strong-field pulse precisely compensates for the dispersive phase in the weak pulse. A numerical example is presented in an optical system consisting of both resonant and gain dispersive effects. Here, we show signal-pulses that do not temporally broaden across a vast propagation distance, even in the presence of dispersion that fluctuates several orders of magnitude and in sign (for example, within a material resonance) across the pulse’s bandwidth. Another numerical example is presented in normal dispersion telecom fiber, where the length at which an ultrafast pulse does not have significant temporal broadening is extended by at least a factor of 10. Our approach can be used in the design of dispersion-less fiber links and navigating pulses in turbulent dispersive media. Furthermore, we illustrate the potential of using cross-phase modulation to compensate for dispersive effects on a signal-pulse and fill the gap in the current understanding of this nonlinear phenomenon.

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Spangenberg, D., E. Rohwer, M. H. Brügmann, and T. Feurer. "Ptychographic ultrafast pulse reconstruction." Optics Letters 40, no. 6 (March 10, 2015): 1002. http://dx.doi.org/10.1364/ol.40.001002.

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Ren, Zhong, and Xiaojing Yang. "Angular-split/temporal-delay approach to ultrafast protein dynamics at XFELs." Acta Crystallographica Section D Structural Biology 72, no. 7 (June 23, 2016): 871–82. http://dx.doi.org/10.1107/s2059798316008573.

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X-ray crystallography promises direct insights into electron-density changes that lead to and arise from structural changes such as electron and proton transfer and the formation, rupture and isomerization of chemical bonds. The ultrashort pulses of hard X-rays produced by free-electron lasers present an exciting opportunity for capturing ultrafast structural events in biological macromolecules within femtoseconds after photoexcitation. However, shot-to-shot fluctuations, which are inherent to the very process of self-amplified spontaneous emission (SASE) that generates the ultrashort X-ray pulses, are a major source of noise that may conceal signals from structural changes. Here, a new approach is proposed to angularly split a single SASE pulse and to produce a temporal delay of picoseconds between the split pulses. These split pulses will allow the probing of two distinct states before and after photoexcitation triggered by a laser pulse between the split X-ray pulses. The split pulses originate from a single SASE pulse and share many common properties; thus, noise arising from shot-to-shot fluctuations is self-canceling. The unambiguous interpretation of ultrafast structural changes would require diffraction data at atomic resolution, as these changes may or may not involve any atomic displacement. This approach, in combination with the strategy of serial crystallography, offers a solution to study ultrafast dynamics of light-initiated biochemical reactions or biological processes at atomic resolution.

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Liu, Xinyue, Bin Xu, Zihao Du, Yi Ding, Yi Hu, Xiaojiang Zhan, Shengbin Liao, and Jiangtao Xi. "Capturing the Motion of Laser Pulse in Photoresist Mixture with Compressed Ultrafast Photography." Photonics 9, no. 12 (November 25, 2022): 903. http://dx.doi.org/10.3390/photonics9120903.

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Imaging the interaction between the laser pulse and photoresist mixture on the ultrafast time scale can track the path of the light pulse and reveal the procedure of the microstructure machining. However, most existing imaging technologies suffer from problems such as requiring multiple repeated shots or a limited time resolution. To overcome these problems, we propose to capture the motion of laser pulses in a photoresist mixture by using compressed ultrafast photography (CUP). In this method, we can recover the motion process of non-repeatable events with a single shot at the time-resolution of about 1.54×1011 fps, where the depth of the imaging sequence reaches hundreds of frames. To verify the effectiveness of the proposed method, we estimate the speed of the laser pulse in a photoresist mixture and evaluate the similarity between the image captured by a streak camera and our reconstructed ultrafast sequence; the results validate the reliability of our proposed method.

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Yang, Yatao, Qiong Zeng, Yanzhao Yang, Geguo Du, Jianhua Ji, Yufeng Song, Zhenhong Wang, and Ke Wang. "Generation and Dynamics of Multiple Pulses in an Ultrafast Fiber Laser with a Single-Mode Fiber–Graded-Index Multimode Fiber–Single-Mode Fiber-Based Saturable Absorber." Photonics 11, no. 1 (January 4, 2024): 52. http://dx.doi.org/10.3390/photonics11010052.

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In this study, we have investigated the evolution process and dynamic characteristics of a multi-pulse regime in an erbium-doped fiber ring laser based on a single-mode fiber–graded-index multimode fiber–single-mode fiber (SMF-GIMF-SMF) structure as an optical modulator. By utilizing the excellent nonlinear optical absorption of the SMF-GIMF-SMF (SMS) device with a modulation depth of ~8.68%, stable single-pulse mode locking at the frequency of 9.84 MHz can be readily observed at low pump power. In addition, the single-pulse operation can evolve into a multiple-pulse regime on account of the peak-power-clamping effect via suitably raising the pump power and carefully regulating the polarization state. Further, the single-shot temporal evolution of multiple pulses is monitored, indicating that this state shows unique and interesting temporal characteristics with variable pulse separations and inconsistent pulse intensities, which, as far as we know, is the first such observation in ultrafast fiber lasers. Additionally, this study, based on the time-stretch dispersive Fourier transformation method, suggests that these multiple pulses consist of chaotic wave envelopes with erratic intensities and changeable pulse energy. We believe that these findings have profound implications for revealing fascinating nonlinear pulse dynamics in ultrafast fiber optics.

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Gu, Chenglin, Dapeng Zhang, Yina Chang, and Shih-Chi Chen. "Arbitrary amplitude femtosecond pulse shaping via a digital micromirror device." Journal of Innovative Optical Health Sciences 12, no. 01 (January 2019): 1840002. http://dx.doi.org/10.1142/s1793545818400023.

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An ultrafast spectrum programmable femtosecond laser may enhance the performance of a wide variety of scientific applications, e.g., multi-photon imaging. In this paper, we report a digital micromirror device (DMD)-based ultrafast pulse shaper, i.e., DUPS, for femtosecond laser arbitrary amplitude shaping — the first time a programmable binary device reported to shape the amplitudes of ultrafast pulses spectrum at up to 32[Formula: see text]kHz rate over a broad wavelength range. The DUPS is highly efficient, compact, and low cost based on the use of a DMD in combination with a transmission grating. Spatial and temporal dispersion introduced by the DUPS is compensated by a quasi-4-f setup and a grating pair, respectively. Femtosecond pulses with arbitrary spectrum shapes, including rectangular, sawtooth, triangular, double-pulse, and exponential profile, have been demonstrated in our experiments. A feedback operation process is implemented in the DUPS to ensure a robust and repeatable shaping process. The total efficiency of the DUPS for amplitude shaping is measured to be 27%.

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Yuan, Kai-Jun, and André D. Bandrauk. "Probing Attosecond Electron Coherence in Molecular Charge Migration by Ultrafast X-Ray Photoelectron Imaging." Applied Sciences 9, no. 9 (May 11, 2019): 1941. http://dx.doi.org/10.3390/app9091941.

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Electron coherence is a fundamental quantum phenomenon in today’s ultrafast physics and chemistry research. Based on attosecond pump–probe schemes, ultrafast X-ray photoelectron imaging of molecules was used to monitor the coherent electron dynamics which is created by an XUV pulse. We performed simulations on the molecular ion H 2 + by numerically solving time-dependent Schrödinger equations. It was found that the X-ray photoelectron angular and momentum distributions depend on the time delay between the XUV pump and soft X-ray probe pulses. Varying the polarization and helicity of the soft X-ray probe pulse gave rise to a modulation of the time-resolved photoelectron distributions. The present results provide a new approach for exploring ultrafast coherent electron dynamics and charge migration in reactions of molecules on the attosecond time scale.

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Rama-Eiroa, R., R. M. Otxoa, and U. Atxitia. "Temperature-dependent critical spin-orbit field for orthogonal switching in antiferromagnets." Applied Physics Letters 121, no. 13 (September 26, 2022): 132401. http://dx.doi.org/10.1063/5.0111127.

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The discovery of current-induced spin–orbit torque (SOT) orthogonal reorientation, also known as orthogonal switching, of metallic Mn2Au and CuMnAs has opened the door for ultrafast writing of an antiferromagnet (AFM). A phenomenological theory predicts that the minimum field necessary for SOT switching—critical field—for ultrashort pulses increases inversely proportional to the pulse duration, thereby limiting the use of ultrafast stimulus as driving force for switching. We explore the possibility that by varying the working temperature, the critical field reduces enabling orthogonal switching in response to ultrashort pulses. To do so, we extend the previous theory to finite temperature and show that the critical field for orthogonal switching strongly depends on temperature. We determine how the temperature dependence of the critical field varies as a function of the pulse duration. For long pulses, the temperature dependence of the critical field is determined by the anisotropy field, and for ultrashort pulses, it is determined by the characteristic frequency of the AFM. We show that the short and long pulse duration limits for the critical field can be connected by an analytical expression.

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Carlson, David R., Daniel D. Hickstein, Wei Zhang, Andrew J. Metcalf, Franklyn Quinlan, Scott A. Diddams, and Scott B. Papp. "Ultrafast electro-optic light with subcycle control." Science 361, no. 6409 (September 27, 2018): 1358–63. http://dx.doi.org/10.1126/science.aat6451.

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Light sources that are ultrafast and ultrastable enable applications like timing with subfemtosecond precision and control of quantum and classical systems. Mode-locked lasers have often given access to this regime, by using their high pulse energies. We demonstrate an adaptable method for ultrastable control of low-energy femtosecond pulses based on common electro-optic modulation of a continuous-wave laser light source. We show that we can obtain 100-picojoule pulse trains at rates up to 30 gigahertz and demonstrate sub–optical cycle timing precision and useful output spectra spanning the near infrared. Our source enters the few-cycle ultrafast regime without mode locking, and its high speed provides access to nonlinear measurements and rapid transients.

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Hassan, Mohammed T., Haihua Liu, John Spencer Baskin, and Ahmed H. Zewail. "Photon gating in four-dimensional ultrafast electron microscopy." Proceedings of the National Academy of Sciences 112, no. 42 (October 5, 2015): 12944–49. http://dx.doi.org/10.1073/pnas.1517942112.

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Ultrafast electron microscopy (UEM) is a pivotal tool for imaging of nanoscale structural dynamics with subparticle resolution on the time scale of atomic motion. Photon-induced near-field electron microscopy (PINEM), a key UEM technique, involves the detection of electrons that have gained energy from a femtosecond optical pulse via photon–electron coupling on nanostructures. PINEM has been applied in various fields of study, from materials science to biological imaging, exploiting the unique spatial, energy, and temporal characteristics of the PINEM electrons gained by interaction with a “single” light pulse. The further potential of photon-gated PINEM electrons in probing ultrafast dynamics of matter and the optical gating of electrons by invoking a “second” optical pulse has previously been proposed and examined theoretically in our group. Here, we experimentally demonstrate this photon-gating technique, and, through diffraction, visualize the phase transition dynamics in vanadium dioxide nanoparticles. With optical gating of PINEM electrons, imaging temporal resolution was improved by a factor of 3 or better, being limited only by the optical pulse widths. This work enables the combination of the high spatial resolution of electron microscopy and the ultrafast temporal response of the optical pulses, which provides a promising approach to attain the resolution of few femtoseconds and attoseconds in UEM.

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Gope, Krishnendu, Itamar Luzon, and Daniel Strasser. "N–NO & NN–O bond cleavage dynamics in two- and three-body Coulomb explosion of the N2O2+ dication." Physical Chemistry Chemical Physics 21, no. 25 (2019): 13730–37. http://dx.doi.org/10.1039/c9cp02908g.

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Assefa, T. A., M. H. Seaberg, A. H. Reid, L. Shen, V. Esposito, G. L. Dakovski, W. Schlotter, et al. "The fluctuation–dissipation measurement instrument at the Linac Coherent Light Source." Review of Scientific Instruments 93, no. 8 (August 1, 2022): 083902. http://dx.doi.org/10.1063/5.0091297.

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The development of new modes at x-ray free electron lasers has inspired novel methods for studying fluctuations at different energies and timescales. For closely spaced x-ray pulses that can be varied on ultrafast time scales, we have constructed a pair of advanced instruments to conduct studies targeting quantum materials. We first describe a prototype instrument built to test the proof-of-principle of resonant magnetic scattering using ultrafast pulse pairs. This is followed by a description of a new endstation, the so-called fluctuation–dissipation measurement instrument, which was used to carry out studies with a fast area detector. In addition, we describe various types of diagnostics for single-shot contrast measurements, which can be used to normalize data on a pulse-by-pulse basis and calibrate pulse amplitude ratios, both of which are important for the study of fluctuations in materials. Furthermore, we present some new results using the instrument that demonstrates access to higher momentum resolution.

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KIDA, Yuichiro, Shin-ichi ZAITSU, and Totaro IMASAKA. "Ultrafast Molecular Optical Pulse Shaping." Review of Laser Engineering 37, no. 4 (2009): 304–11. http://dx.doi.org/10.2184/lsj.37.304.

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GUPTA, J. A., D. D. AWSCHALOM, R. KNOBEL, and N. SAMARTH. "ULTRAFAST MANIPULATION OF ELECTRON SPIN COHERENCE IN QUANTUM WELLS." International Journal of Modern Physics B 16, no. 20n22 (August 30, 2002): 2930–35. http://dx.doi.org/10.1142/s0217979202013237.

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A recently developed technique is reviewed with the potential for all-optical coherent control over electron spins in semiconductors. In these experiments, ultrafast laser pulses "tip" electron spins by generating effective magnetic fields via the optical Stark effect. Measurements of Stark shifts have provided estimates of the net tipping angle as a function of tipping pulse energy, intensity, and polarization. Background contributions to the measured tipping angle arise from the undesirable excitation of additional carriers by the tipping pulse.

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32

Lotarev, Sergey V., Sergey S. Fedotov, Alyona I. Pomigueva, Alexey S. Lipatiev, and Vladimir N. Sigaev. "Effect of Pulse Repetition Rate on Ultrafast Laser-Induced Modification of Sodium Germanate Glass." Nanomaterials 13, no. 7 (March 29, 2023): 1208. http://dx.doi.org/10.3390/nano13071208.

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We report an unexpected pulse repetition rate effect on ultrafast-laser modification of sodium germanate glass with the composition 22Na2O 78GeO2. While at a lower pulse repetition rate (~≤250 kHz), the inscription of nanogratings possessing form birefringence is observed under series of 105–106 pulses, a higher pulse repetition rate launches peripheral microcrystallization with precipitation of the Na2Ge4O9 phase around the laser-exposed area due to the thermal effect of femtosecond pulses via cumulative heating. Depending on the pulse energy, the repetition rate ranges corresponding to nanograting formation and microcrystallization can overlap or be separated from each other. Regardless of crystallization, the unusual growth of optical retardance in the nanogratings with the pulse repetition rate starting from a certain threshold has been revealed instead of a gradual decrease in retardance with the pulse repetition rate earlier reported for some other glasses. The repetition rate threshold of the retardance growth is shown to be inversely related to the pulse energy and to vary from ~70 to 200 kHz in the studied energy range. This effect can be presumably assigned to the chemical composition shift due to the thermal diffusion of sodium cations occurring at higher pulse repetition rates when the thermal effect of the ultrashort laser pulses becomes noticeable.

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33

Meng, Yu, An Gong, Zhicheng Chen, Qingsong Wang, Jianwu Guo, Zihao Li, and Jiafang Li. "Atomistic-Continuum Study of an Ultrafast Melting Process Controlled by a Femtosecond Laser-Pulse Train." Materials 17, no. 1 (December 29, 2023): 185. http://dx.doi.org/10.3390/ma17010185.

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In femtosecond laser fabrication, the laser-pulse train shows great promise in improving processing efficiency, quality, and precision. This research investigates the influence of pulse number, pulse interval, and pulse energy ratio on the lateral and longitudinal ultrafast melting process using an experiment and the molecular dynamics coupling two-temperature model (MD-TTM model), which incorporates temperature-dependent thermophysical parameters. The comparison of experimental and simulation results under single and double pulses proves the reliability of the MD-TTM model and indicates that as the pulse number increases, the melting threshold at the edge region of the laser spot decreases, resulting in a larger diameter of the melting region in the 2D lateral melting results. Using the same model, the lateral melting results of five pulses are simulated. Moreover, the longitudinal melting results are also predicted, and an increasing pulse number leads to a greater early-stage melting depth in the melting process. In the case of double femtosecond laser pulses, the pulse interval and pulse energy ratio also affect the early-stage melting depth, with the best enhancement observed with a 2 ps interval and a 3:7 energy ratio. However, pulse number, pulse energy ratio, and pulse interval do not affect the final melting depth with the same total energies. The findings mean that the phenomena of melting region can be flexibly manipulated through the laser-pulse train, which is expected to be applied to improve the structural precision and boundary quality.

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Yang, Jinfeng, Kazuki Gen, Nobuyasu Naruse, Shouichi Sakakihara, and Yoichi Yoshida. "A Compact Ultrafast Electron Diffractometer with Relativistic Femtosecond Electron Pulses." Quantum Beam Science 4, no. 1 (January 20, 2020): 4. http://dx.doi.org/10.3390/qubs4010004.

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We have developed a compact relativistic femtosecond electron diffractometer with a radio-frequency photocathode electron gun and an electron lens system. The electron gun generated 2.5-MeV-energy electron pulses with a duration of 55 ± 5 fs containing 6.3 × 104 electrons per pulse. Using these pulses, we successfully detected high-contrast electron diffraction images of single crystalline, polycrystalline, and amorphous materials. An excellent spatial resolution of diffraction images was obtained as 0.027 ± 0.001 Å−1. In the time-resolved electron diffraction measurement, a laser-excited ultrafast electronically driven phase transition in single-crystalline silicon was observed with a temporal resolution of 100 fs. The results demonstrate the advantages of the compact relativistic femtosecond electron diffractometer, including access to high-order Bragg reflections, single shot imaging with the relativistic femtosecond electron pulse, and the feasibility of time-resolved electron diffraction to study ultrafast structural dynamics.

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Takubo, Kou, Samiran Banu, Sichen Jin, Misaki Kaneko, Wataru Yajima, Makoto Kuwahara, Yasuhiko Hayashi, et al. "Generation of sub-100 fs electron pulses for time-resolved electron diffraction using a direct synchronization method." Review of Scientific Instruments 93, no. 5 (May 1, 2022): 053005. http://dx.doi.org/10.1063/5.0086008.

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To investigate photoinduced phenomena in various materials and molecules, ultrashort pulsed x-ray and electron sources with high brightness and high repetition rates are required. The x-ray and electron’s typical and de Broglie wavelengths are shorter than lattice constants of materials and molecules. Therefore, photoinduced structural dynamics on the femtosecond to picosecond timescales can be directly observed in a diffraction manner by using these pulses. This research created a tabletop ultrashort pulsed electron diffraction setup that used a femtosecond laser and electron pulse compression cavity that was directly synchronized to the microwave master oscillator (∼3 GHz). A compressed electron pulse with a 1 kHz repetition rate contained 228 000 electrons. The electron pulse duration was estimated to be less than 100 fs at the sample position by using photoinduced immediate lattice changes in an ultrathin silicon film (50 nm). The newly developed time-resolved electron diffraction setup has a pulse duration that is comparable to femtosecond laser pulse widths (35–100 fs). The pulse duration, in particular, fits within the timescale of photoinduced phenomena in quantum materials. Our developed ultrafast time-resolved electron diffraction setup with a sub-100 fs temporal resolution would be a powerful tool in material science with a combination of optical pump–probe, time-resolved photoemission spectroscopic, and pulsed x-ray measurements.

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Divitt, Shawn, Wenqi Zhu, Cheng Zhang, Henri J. Lezec, and Amit Agrawal. "Ultrafast optical pulse shaping using dielectric metasurfaces." Science 364, no. 6443 (May 2, 2019): 890–94. http://dx.doi.org/10.1126/science.aav9632.

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Advances in ultrafast lasers, chirped pulse amplifiers, and frequency comb technology require fundamentally new pulse-modulation strategies capable of supporting unprecedentedly large bandwidth and high peak power while maintaining high spectral resolution. We demonstrate how dielectric metasurfaces can be leveraged to shape the temporal profile of a near-infrared femtosecond pulse. Finely tailored pulse-shaping operations, including splitting, compression, chirping, and higher-order distortion, are achieved using a Fourier-transform setup embedding metasurfaces able to manipulate, simultaneously and independently, the amplitude and phase of the constituent frequency components of the pulse. Exploiting metasurfaces to manipulate the temporal characteristics of light expands their impact and opens new vistas in the field of ultrafast science and technology.

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37

Yang, Ya-Tao, Han-Wei Wu, Yuan Zou, Xue-Yang Fang, Shuang Li, Yu-Feng Song, Zhen-Hong Wang, and Bin Zhang. "Facile Synthesis of Monodispersed Titanium Nitride Quantum Dots for Harmonic Mode-Locking Generation in an Ultrafast Fiber Laser." Nanomaterials 12, no. 13 (July 1, 2022): 2280. http://dx.doi.org/10.3390/nano12132280.

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As a member of the transition metal nitride material family, titanium nitride (TiN) quantum dots (QDs) have attracted great attention in optical and electronic fields because of their excellent optoelectronic properties and favorable stability. Herein, TiN QDs were synthesized and served as a saturable absorber (SA) for an ultrafast fiber laser. Due to the strong nonlinear optical absorption characteristics with a modulation depth of ~33%, the typical fundamental mode-locked pulses and harmonics mode-locked pulses can be easily obtained in an ultrafast erbium-doped fiber laser with a TiN-QD SA. In addition, at the maximum pump power, harmonic mode-locked pulses with a repetition rate of ~1 GHz (164th order) and a pulse duration of ~1.45 ps are achieved. As far as we know, the repetition rate is the highest in the ultrafast fiber laser using TiN QDs as an SA. Thus, these experimental results indicate that TiN QDs can be considered a promising material, showing more potential in the category of ultrafast laser and nonlinear optics.

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38

Tawfik, Walid. "Precise measurement of ultrafast laser pulses using spectral phase interferometry for direct electric-field reconstruction." Journal of Nonlinear Optical Physics & Materials 24, no. 04 (December 2015): 1550040. http://dx.doi.org/10.1142/s021886351550040x.

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In this work, I present a novel method for measuring the pulse duration of few-cycle pulses using spectral phase interferometry for direct electric-field reconstruction (SPIDER) with high accuracy. These few-cycle pulses were generated due to nonlinear self-phase modulation (SPM) in nonlinear medium (neon gas) using a one meter hollow-fiber. The observed reconstructed pulse intensity autocorrelation function was varied from 5.35[Formula: see text]fs to almost 13[Formula: see text]fs. Moreover, the applied method allows for direct controlling of the output pulse duration through variation of the pulse-width of input pulses at different pressure of neon gas. The observed results indicate that the SPM was enhanced for high neon pressure (2.5[Formula: see text]atm.) and short input pluses (32[Formula: see text]fs) without chirping. The obtained results may give an opportunity to monitor and control ultrafast transit interaction in femtosecond chemistry.

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39

Zhang, Dongfang, Tobias Kroh, Felix Ritzkowsky, Timm Rohwer, Moein Fakhari, Huseyin Cankaya, Anne-Laure Calendron, Nicholas H. Matlis, and Franz X. Kärtner. "THz-Enhanced DC Ultrafast Electron Diffractometer." Ultrafast Science 2021 (August 11, 2021): 1–7. http://dx.doi.org/10.34133/2021/9848526.

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Terahertz- (THz-) based electron manipulation has recently been shown to hold tremendous promise as a technology for manipulating and driving the next generation of compact ultrafast electron sources. Here, we demonstrate an ultrafast electron diffractometer with THz-driven pulse compression. The electron bunches from a conventional DC gun are compressed by a factor of 10 and reach a duration of ~180 fs (FWHM) with 10,000 electrons/pulse at a 1 kHz repetition rate. The resulting ultrafast electron source is used in a proof-of-principle experiment to probe the photoinduced dynamics of single-crystal silicon. The THz-compressed electron beams produce high-quality diffraction patterns and enable the observation of the ultrafast structural dynamics with improved time resolution. These results validate the maturity of THz-driven ultrafast electron sources for use in precision applications.

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40

Berger, Joel A., John T. Hogan, Michael J. Greco, W. Andreas Schroeder, Alan W. Nicholls, and Nigel D. Browning. "DC Photoelectron Gun Parameters for Ultrafast Electron Microscopy." Microscopy and Microanalysis 15, no. 4 (July 3, 2009): 298–313. http://dx.doi.org/10.1017/s1431927609090266.

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AbstractWe present a characterization of the performance of an ultrashort laser pulse driven DC photoelectron gun based on the thermionic emission gun design of Togawa et al. [Togawa, K., Shintake, T., Inagaki, T., Onoe, K. & Tanaka, T. (2007). Phys Rev Spec Top-AC10, 020703]. The gun design intrinsically provides adequate optical access and accommodates the generation of ∼1 mm2 electron beams while contributing negligible divergent effects at the anode aperture. Both single-photon (with up to 20,000 electrons/pulse) and two-photon photoemission are observed from Ta and Cu(100) photocathodes driven by the harmonics (∼4 ps pulses at 261 nm and ∼200 fs pulses at 532 nm, respectively) of a high-power femtosecond Yb:KGW laser. The results, including the dependence of the photoemission efficiency on the polarization state of the drive laser radiation, are consistent with expectations. The implications of these observations and other physical limitations for the development of a dynamic transmission electron microscope with sub-1 nm·ps space-time resolution are discussed.

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Wang, Xiuqi, Mengping Zhong, Huanhuan Li, Kunyang Wang, Can Li, Junjie Zhang, and Shiqing Xu. "Mode-locked thulium-doped fiber laser using a stretched few-mode fiber as a saturable absorber." Laser Physics 34, no. 4 (February 15, 2024): 045102. http://dx.doi.org/10.1088/1555-6611/ad21f0.

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Abstract In this work, an all-fiber saturable absorber (SA) based on nonlinear multimode interference in a short few-mode fiber (FMF) was proposed. Saturable absorption in this all-fiber device was demonstrated with an absorption modulation depth and a saturation fluence of 14.3% and 55.6 μJ cm−2, respectively. A stable mode-locking operation was observed in a thulium-doped passively mode-locked fiber laser using the FMF-based FMF SA. Ultrafast pulses were generated at 1911 nm with a pulse width of 1.96 ps and a 15.69 MHz repetition rate, respectively. The output average power was 2.8 mW, corresponding to a pulse energy of 178 pJ, which was significantly improved compared to graded-index multimode fiber-based SA. The experimental results demonstrate that FMF SA has great potential in eye-safe ultrafast photonics.

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Cheng, Zhenjia, Yuqin Zhang, Xuan Liu, Chengshan Guo, Changwei He, Guiyuan Liu, and Hongsheng Song. "Time-Resolved Four-Channel Jones Matrix Measurement of Birefringent Materials Using an Ultrafast Laser." Materials 15, no. 21 (November 5, 2022): 7813. http://dx.doi.org/10.3390/ma15217813.

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A method for ultrafast time-resolved four-channel Jones matrix measurement of birefringent materials using an ultrafast laser is investigated. This facilitated the acquisition of a four-channel angular multiplexing hologram in a single shot. The Jones matrix information of a birefringent sample was retrieved from the spatial spectrum of a hologram. The feasibility of this approach was established by measuring the Jones matrix of starch granules in microfluidic chips and the complex amplitude distribution and phase delay distribution of liquid crystal cell at different voltages. Moreover, when the picosecond laser was switched to a femtosecond laser, ultrafast measurements were possible provided that the time interval between two detection pulses was larger than the pulse width.

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Eidam, Tino, Sven Breitkopf, Oliver Herrfurth, Fabian Stutzki, Marco Kienel, Steffen Hädrich, Christian Gaida, and Jens Limpert. "High-power ultrafast fiber lasers for materials processing." Advanced Optical Technologies 10, no. 4-5 (October 15, 2021): 277–83. http://dx.doi.org/10.1515/aot-2021-0033.

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Abstract State-of-the-art fiber-laser systems can deliver femtosecond pulses at average powers beyond the kilowatt level and multi-mJ pulse energies by employing advanced large-mode-area fiber designs, chirped-pulse amplification, and the coherent combination of parallel fiber amplifiers. By using sophisticated coherent phase control, one or even several output ports can be modulated at virtually arbitrary power levels and switching speeds. In addition, an all-fiber setup for GHz-burst generation is described allowing to access an even wider range of laser parameters. The combination of all these approaches together with the robustness, efficiency, and excellent beam quality inherent to fiber-laser technology has the potential to strongly improve existing materials-processing applications.

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Xiao, Yaozong, Chao Feng, Hao Sun, and Bo Liu. "Feasibility verification of ultrafast FEL generation experimental scheme based on SXFEL." Journal of Physics: Conference Series 2687, no. 3 (January 1, 2024): 032008. http://dx.doi.org/10.1088/1742-6596/2687/3/032008.

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Abstract The photon energy in the soft X-ray range corresponds to the fundamental absorption edges of matter. Ultrashort X-ray pulses can be used to observe the breaking of chemical bonds in biochemical reactions and capture the transfer process of electrons in ultrafast physical phenomena. In this paper, the feasibility of ESASE experiments on Shanghai Soft X-ray Free Electron Laser Facility (SXFEL) is theoretically verified. The results show that the ESASE scheme can produce ultrafast light pulses on the order of attosecond, with a peak power of 450 MW. At the same time, the simulation results in this paper verify the feasibility of chirped enhanced SASE schenme based on SXFEL. The results show that compared with the ESASE scheme, the power of the radiation pulse can be greatly improved by this scheme. A relatively low energy electron beam (1.5 GeV) was used to generate about 40 GW of radiation, and the length of the radiation pulse was significantly shortened.

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Remnev, G. E., V. A. Tarbokov, and S. K. Pavlov. "Material modification by high-intense pulsed ion beams." Physics and Chemistry of Materials Treatment 2 (2021): 5–26. http://dx.doi.org/10.30791/0015-3214-2021-2-5-26.

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The review is devoted to the use of powerful submicrosecond ion beams for the synthesis and modification of material properties. Powerful ion beams, originally developed for the problems of inertial thermonuclear fusion, have been increasingly used over the past 30 years as a powerful pulsed heating source providing ample opportunities for modifying the surface layer of materials. By varying the key parameters of the beams, such as the composition (type of ions), the duration of the accelerating pulse (10 ns – 1 μs), the kinetic energy of the ions (0.1 – 1 MeV), the energy density transmitted by the beam to the target surface per pulse (0.1 – 50 J/cm2), the main areas of application of high-power ion beams in materials science were determined: modification of the surface layer by ultrafast quenching, melting and ultrafast recrystallization with the formation of micro- and nanostructures, pulsed implantation of ions accompanied by energetic action, deposition of thin films and synthesis of nanosized powders from ablative plasma.

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Mishina, Elena, Kirill Grishunin, Vladislav Bilyk, Natalia Sherstyuk, Alexander Sigov, Vladimir Mukhortov, Andrey Ovchinnikov, and Alexey Kimel. "Polarization switching in ferroelectric thin film induced by a single-period terahertz pulse." MRS Advances 3, no. 33 (2018): 1901–6. http://dx.doi.org/10.1557/adv.2018.235.

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ABSTRACTWe report here an experimental study of ultrafast response of the dielectric polarization in (Ba0.8Sr0.2)TiO3 thin films to a strong electric field of a nearly single-cycle THz pulse. The phenomenon of Second Harmonic Generation (SHG) is used as a probe of the polarization in the terahertz pump-optical probe experiment. SHG loops for THz pulses of different amplitudes were obtained. The SHG response is modelled assuming that the ferroelectric material is split into 180-degree domains. It is shown that intuitive model based on forced harmonic oscillator does not fully describe to the observed ultrafast ferroelectric response

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Cahill, David G., and Steve M. Yalisove. "Ultrafast Lasers in Materials Research." MRS Bulletin 31, no. 8 (August 2006): 594–600. http://dx.doi.org/10.1557/mrs2006.155.

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AbstractWith the availability of off-the-shelf commercial ultrafast lasers, a small revolution in materials research is underway, as it is now possible to use these tools without being an expert in the development of the tools themselves. Lasers with short-duration optical pulses—in the sub-picosecond (less than one-trillionth of a second) range—are finding a variety of applications, from basic research on fast processes in materials to new methods for microfabrication by direct writing. A huge range of pulse energies are being used in these applications, from less than 1 nJ (a billionth of a joule) to many joules.

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Yang, Jinfeng, and Yoichi Yoshida. "Relativistic Ultrafast Electron Microscopy: Single-Shot Diffraction Imaging with Femtosecond Electron Pulses." Advances in Condensed Matter Physics 2019 (May 2, 2019): 1–6. http://dx.doi.org/10.1155/2019/9739241.

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We report on a single-shot diffraction imaging methodology using relativistic femtosecond electron pulses generated by a radio-frequency acceleration-based photoemission gun. The electron pulses exhibit excellent characteristics, including a root-mean-square (rms) illumination convergence of 31 ± 2 μrad, a spatial coherence length of 5.6 ± 0.4 nm, and a pulse duration of approximately 100 fs with (6.3 ± 0.6) × 106 electrons per pulse at 3.1 MeV energy. These pulses facilitate high-quality diffraction images of gold single crystals with a single shot. The rms spot width of the diffracted beams was obtained as 0.018 ± 0.001 Å−1, indicating excellent spatial resolution.

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Arkhipov M. V., Arkhipov R. M., and Rosanov N. N. "Generation of unipolar pulses of terahertz radiation with a large electric area." Optics and Spectroscopy 130, no. 8 (2022): 980. http://dx.doi.org/10.21883/eos.2022.08.54771.3703-22.

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A physical situation is proposed and theoretically analyzed, in which, in our opinion, it is possible to generate unipolar terahertz pulses with a large electric area. In this case, the gas in the tube is excited by a femtosecond IR laser pulse. In this case, the tube with gas is placed in a constant external electric field. The generation of a unipolar pulse is based on "three-step scheme" --- ionization of gas atoms by a femtosecond pulse, subsequent acceleration of a free electron in a dc external field and subsequent annihilation of an electron upon collision with a tube wall or another atom (ion). Keywords: unipolar pulses, ultrafast optics, electric pulse area, terahertz radiation, three-step model.

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Xu, Nannan, Haifeng Wang, Huanian Zhang, Linguang Guo, Xinxin Shang, Shouzhen Jiang, and Dengwang Li. "Palladium diselenide as a direct absorption saturable absorber for ultrafast mode-locked operations: from all anomalous dispersion to all normal dispersion." Nanophotonics 9, no. 14 (July 28, 2020): 4295–306. http://dx.doi.org/10.1515/nanoph-2020-0267.

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AbstractLayered transition metal dichalcogenides with excellent nonlinear absorption properties have shown remarkable performance in acting as ultrafast photonics devices. In our work, palladium diselenide (PdSe2) nanosheets with competitive advantages of wide tunable bandgap, unique puckered pentagonal structure and excellent air stability are prepared by the liquid-phase exfoliation method. Its ultrafast absorption performance was verified by demonstrating conventional and dissipative soliton operations within Er-doped fiber lasers. The minimum pulse width of the conventional soliton was 1.19 ps. Meanwhile, dissipative soliton with a 46.67 mW output power, 35.37 nm spectrum width, 14.92 ps pulse width and 2.86 nJ pulse energy was also generated successfully. Our enhanced experiment results present the excellent absorption performance of PdSe2 and highlight the capacity of PdSe2 in acting as ultrafast photonics devices.

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Journal articles on the topic 'Ultrafast Pulse'

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