Time domain Ramsey-type interferometry is useful for investigating spectroscopic information of quantum states in atoms and molecules. The energy range of the quantum states to be observed with this scheme has now reached more than 20&#x2009;eV by resolving the interference fringes with a period of a few hundred attoseconds. This attosecond Ramsey-type interferometry requires the irradiation of a coherent pair of extreme ultraviolet (XUV) light pulses, while all the methods used to deliver the coherent XUV pulse pair until now have relied on the division of the source of an XUV pulse in two before the generation. In this paper, we report on a novel technique to perform attosecond Ramsey-type interferometry by splitting an XUV high-order harmonic (HH) pulse of a sub-20&#x2009;fs laser pulse after its generation. By virtue of the postgeneration splitting of the HH pulse, we demonstrated that the optical interference emerging at the complete temporal overlap of the HH pulse pair seamlessly continued to the Ramsey-type electronic interference in a helium atom. This technique is applicable for studying the femtosecond dephasing dynamics of electronic wavepackets and exploring the ultrafast evolution of a cationic system entangled with an ionized electron with sub-20&#x2009;fs resolution.

Takuya Matsubara

Yasuo Nabekawa

Kenichi L. Ishikawa

Kaoru Yamanouchi

Katsumi Midorikawa

Attosecond Optical and Ramsey-Type Interferometry by Postgeneration Splitting of Harmonic Pulse

Here, we report the recent progress on the front end developed for the 100 PW-class laser facility. Using 3 stages of optical parametric chirped-pulse amplification (OPCPA) based on lithium triborate (LBO) crystals, we realized a 5.26&#x2009;J/0.1&#x2009;Hz amplified output with a bandwidth over 200&#x2009;nm near the center wavelength of 925&#x2009;nm. After the compressor, we obtained a pulse duration of 13.4&#x2009;fs. As the compression efficiency reached 67&#x0025;, this OPCPA front end could potentially support a peak power of 263&#x2009;TW at a repetition rate of 0.1&#x2009;Hz. To the best of our knowledge, among all the 100&#x2009;TW-level OPCPA systems, it shows the widest spectral width, the shortest pulse duration, and it is also the first OPCPA system working at a repetition-rate mode.

Xinliang Wang

Xingyan Liu

Xiaoming Lu

Junchi Chen

Yingbin Long

Wenkai Li

Haidong Chen

Xun Chen

Peile Bai

Yanyan Li

Yujie Peng

Yanqi Liu

Fenxiang Wu

Cheng Wang

Zhaoyang Li

Yi Xu

Xiaoyan Liang

Yuxin Leng

Ruxin Li

13.4&#x2009;fs, 0.1&#x2009;Hz OPCPA Front End for the 100 PW-Class Laser Facility

The time delay of photoelectron emission serves as a fundamental building block to understand the ultrafast electron emission dynamics in strong-field physics. Here, we study the photoelectron angular streaking of CO molecules by using two-color (<svg xmlns="http://www.w3.org/2000/svg" id="M1" style="vertical-align:-0.6075296pt" height="9.3427pt" version="1.1" viewBox="-0.0498162 -8.73517 51.8539 9.3427" width="51.8539pt"><g transform="matrix(.0125,0,0,-0.0125,0,0)"><path d="M473 167V231H370V676H326L12 231V167H292V0H370V167H473ZM292 231H52L292 574V231Z"/></g><g transform="matrix(.0125,0,0,-0.0125,6.243,0)"><path d="M476 330C476 535 385 676 254 676C93 676 24 513 24 336C24 172 79 -14 250 -14C413 -14 476 158 476 330ZM380 325C380 127 335 12 250 12C164 12 120 126 120 329S165 650 248 650C336 650 380 533 380 325Z"/></g><g transform="matrix(.0125,0,0,-0.0125,12.486,0)"><path d="M476 330C476 535 385 676 254 676C93 676 24 513 24 336C24 172 79 -14 250 -14C413 -14 476 158 476 330ZM380 325C380 127 335 12 250 12C164 12 120 126 120 329S165 650 248 650C336 650 380 533 380 325Z"/></g><g transform="matrix(.0125,0,0,-0.0125,21.514,0)"><path d="M636 220V286H375V547H309V286H48V220H309V-41H375V220H636Z"/></g><g transform="matrix(.0125,0,0,-0.0125,32.852,0)"><path d="M445 155C445 235 413 289 290 371C389 424 424 458 424 533C424 611 355 676 256 676C145 676 62 616 62 520C62 455 83 417 186 332C79 257 56 218 56 149C56 55 135 -14 248 -14C368 -14 445 52 445 155ZM355 533C355 471 329 429 261 389C173 441 136 487 136 549S179 648 246 648C314 648 355 602 355 533ZM271 272C339 226 369 186 369 124C369 59 324 14 259 14C183 14 132 66 132 158C132 223 153 264 212 312L271 272Z"/></g><g transform="matrix(.0125,0,0,-0.0125,39.096,0)"><path d="M476 330C476 535 385 676 254 676C93 676 24 513 24 336C24 172 79 -14 250 -14C413 -14 476 158 476 330ZM380 325C380 127 335 12 250 12C164 12 120 126 120 329S165 650 248 650C336 650 380 533 380 325Z"/></g><g transform="matrix(.0125,0,0,-0.0125,45.339,0)"><path d="M476 330C476 535 385 676 254 676C93 676 24 513 24 336C24 172 79 -14 250 -14C413 -14 476 158 476 330ZM380 325C380 127 335 12 250 12C164 12 120 126 120 329S165 650 248 650C336 650 380 533 380 325Z"/></g></svg> nm) corotating circularly polarized fields. By coincidently measuring photoelectrons with the dissociative ions, we present molecular frame photoelectron angular distributions with respect to the instantaneous driving electric field signatures. We develop a semiclassical nonadiabatic molecular quantum-trajectory Monte Carlo (MO-QTMC) model that fully captures the experimental observations and further ab initio simulations. We disentangle the orientation-resolved contribution of the anisotropic ionic potential and the molecular orbital structure on the measured photoelectron angular distributions. Furthermore, by analyzing the photoelectron interference patterns, we extract the sub-Coulomb-barrier phase distribution of the photoelectron wavepacket and reconstruct the orientation- and energy-resolved Wigner time delay in the molecular frame. Holographic angular streaking with bicircular fields can be used for probing polyatomic molecules in the future.

Zhenning Guo

Peipei Ge

Yiqi Fang

Yankun Dou

Xiaoyang Yu

Jiguo Wang

Qihuang Gong

Yunquan Liu

Probing Molecular Frame Wigner Time Delay and Electron Wavepacket Phase Structure of CO Molecule

More than ten years ago, the observation of the low-energy structure in the photoelectron energy spectrum, regarded as an &#x201C;ionization surprise,&#x201D; has overthrown our understanding of strong-field physics. However, the similar low-energy nuclear fragment generation from dissociating molecules upon the photon energy absorption, one of the well-observed phenomena in light-molecule interaction, still lacks an unambiguous mechanism and remains mysterious. Here, we introduce a time-energy-resolved manner using a multicycle near-infrared femtosecond laser pulse to identify the physical origin of the light-induced ultrafast dynamics of molecules. By simultaneously measuring the bond-stretching times and photon numbers involved in the dissociation of H2+ driven by a polarization-skewed laser pulse, we reveal that the low-energy protons (below 0.7&#x2009;eV) are produced via dipole-transitions at large bond lengths. The observed low-energy protons originate from strong-field dissociation of high vibrational states rather than the low ones of H2+ cation, which is distinct from the well-accepted bond-softening picture. Further numerical simulation of the time-dependent Schr&#x00F6;dinger equation unveils that the electronic states are periodically distorted by the strong laser field, and the energy gap between the field-dressed transient electronic states may favor the one- or three-photon transitions at the internuclear distance larger than 5&#x2009;a.u. The time-dependent scenario and our time-energy-resolved approach presented here can be extended to other molecules to understand the complex ultrafast dynamics.

Shengzhe Pan

Chenxi Hu

Zhaohan Zhang

Peifen Lu

Chenxu Lu

Lianrong Zhou

Jiawei Wang

Fenghao Sun

Junjie Qiang

Hui Li

Hongcheng Ni

Xiaochun Gong

Feng He

Jian Wu

Low-Energy Protons in Strong-Field Dissociation of H2+ via Dipole-Transitions at Large Bond Lengths

Remote or standoff detection of greenhouse gases, air pollutants, and biological agents with innovative ultrafast laser technology attracts growing interests in recent years. Hybrid femtosecond/picosecond coherent Raman spectroscopy is considered as one of the most versatile techniques due to its great advantages in terms of detection sensitivity and chemical specificity. However, the simultaneous requirement for the femtosecond pump and the picosecond probe increases the complexity of optical system. Herein, we demonstrate that air lasing naturally created inside a filament can serve as an ideal light source to probe Raman coherence excited by the femtosecond pump, producing coherent Raman signal with molecular vibrational signatures. The combination of pulse self-compression effect and air lasing action during filamentation improves Raman excitation efficiency and greatly simplifies the experimental setup. The air-lasing-assisted Raman spectroscopy was applied to quantitatively detect greenhouse gases mixed in air, and it was found that the minimum detectable concentrations of CO2 and SF6 can reach 0.1&#x0025; and 0.03&#x0025;, respectively. The ingenious designs, especially the optimization of pump-seed delay and the choice of perpendicular polarization, ensure a high detection sensitivity and signal stability. Moreover, it is demonstrated that this method can be used for simultaneously measuring CO2 and SF6 gases and distinguishing 12CO2 and 13CO2. The developed scheme provides a new route for high-sensitivity standoff detection and combustion diagnosis.

Zhihao Zhang

Fangbo Zhang

Bo Xu

Hongqiang Xie

Botao Fu

Xu Lu

Ning Zhang

Shupeng Yu

Jinping Yao

Ya Cheng

Zhizhan Xu

High-Sensitivity Gas Detection with Air-Lasing-Assisted Coherent Raman Spectroscopy

As ultrafast laser technology advances towards ever higher peak and average powers, generating sub-50 fs pulses from laser architectures that exhibit best power-scaling capabilities remains a major challenge. Here, we present a very compact and highly robust method to compress 1.24 ps pulses to 39 fs by means of only a single spectral broadening stage which neither requires vacuum parts nor custom-made optics. Our approach is based on the hybridization of the multiplate continuum and the multipass cell spectral broadening techniques. Their combination leads to significantly higher spectral broadening factors in bulk material than what has been reported from either method alone. Moreover, our approach efficiently suppresses adverse features of single-pass bulk spectral broadening. We use a burst-mode Yb:YAG laser emitting pulses with 80 MW peak power that are enhanced to more than 1 GW after postcompression. With only 0.19% rms pulse-to-pulse energy fluctuations, the technique exhibits excellent stability. Furthermore, we have measured state-of-the-art spectral-spatial homogeneity and good beam quality of <svg xmlns="http://www.w3.org/2000/svg" id="M1" style="vertical-align:-0.1814003pt" height="10.6975pt" version="1.1" viewBox="-0.0498162 -10.5161 48.3929 10.6975" width="48.3929pt"><g transform="matrix(.0125,0,0,-0.0125,0,0)"><path d="M933 662H810L467 180L363 662H240L75 0H160L294 541L411 0H432L818 543L683 0H768L933 662Z"/></g><g transform="matrix(.0088,0,0,-0.0088,12.155,-4.387)"><path d="M474 137L460 143C427 87 406 76 364 76H130L295 252C384 346 423 421 423 500C423 599 351 676 238 676C115 676 51 594 30 477L51 472C91 570 126 602 198 602C283 602 337 552 337 461C337 376 301 300 207 201L29 12V0H420L474 137Z"/></g><g transform="matrix(.0125,0,0,-0.0125,20.521,0)"><path d="M637 320V386H48V320H637ZM637 120V186H48V120H637Z"/></g><g transform="matrix(.0125,0,0,-0.0125,32.556,0)"><path d="M394 0V15C319 15 299 33 299 76V673L290 676L111 585V571L138 581C156 588 173 593 183 593C204 593 213 578 213 544V95C213 40 192 19 118 15V0H394Z"/></g><g transform="matrix(.0125,0,0,-0.0125,38.799,0)"><path d="M181 43C181 73 155 100 126 100C95 100 70 75 70 44S94 -11 125 -11C155 -11 181 14 181 43Z"/></g><g transform="matrix(.0125,0,0,-0.0125,41.92,0)"><path d="M474 137L460 143C427 87 406 76 364 76H130L295 252C384 346 423 421 423 500C423 599 351 676 238 676C115 676 51 594 30 477L51 472C91 570 126 602 198 602C283 602 337 552 337 461C337 376 301 300 207 201L29 12V0H420L474 137Z"/></g></svg> up to a spectral broadening factor of 30. Due to the method’s simplicity, compactness, and scalability, it is highly attractive for turning a picosecond laser into an ultrafast light source that generates pulses of only a few tens of femtoseconds duration.

Marcus Seidel

Prannay Balla

Chen Li

Gunnar Arisholm

Lutz Winkelmann

Ingmar Hartl

Christoph M. Heyl

Factor 30 Pulse Compression by Hybrid Multipass Multiplate Spectral Broadening

Terahertz radiation with a Bessel beam profile is demonstrated experimentally from a two-color laser filament in air, which is induced by tailored femtosecond laser pulses with an axicon. The temporal and spatial distributions of Bessel rings of the terahertz radiation are retrieved after being collected in the far field. A theoretical model is proposed, which suggests that such Bessel terahertz pulses are produced due to the combined effects of the inhomogeneous superluminal filament structure and the phase change of the two-color laser components inside the plasma channel. These two effects lead to wavefront crossover and constructive/destructive interference of terahertz radiation from different plasma sources along the laser filament, respectively. Compared with other methods, our technique can support the generation of Bessel pulses with broad spectral bandwidth. Such Bessel pulses can propagate to the far field without significant spatial spreading, which shall provide new opportunities for terahertz applications.

Zhelin Zhang

Jiayang Zhang

Yanping Chen

Tianhao Xia

Linzheng Wang

Bonan Han

Zhengming Sheng

Jie Zhang

Bessel Terahertz Pulses from Superluminal Laser Plasma Filaments

High-repetition rate attosecond pulse sources are indispensable tools for time-resolved studies of electron dynamics, such as coincidence spectroscopy and experiments with high demands on statistics or signal-to-noise ratio, especially in the case of solid and big molecule samples in chemistry and biology. Although with the high-repetition rate lasers, such attosecond pulses in a pump-probe configuration are possible to achieve, until now, only a few such light sources have been demonstrated. Here, by shaping the driving laser to an annular beam, a 100&#x2009;kHz attosecond pulse train (APT) is reported with the highest energy so far (51&#x2009;pJ/shot) on target (269&#x2009;pJ at generation) among the high-repetition rate systems (&#x003E;10&#x2009;kHz) in which the attosecond pulses were temporally characterized. The on-target pulse energy is maximized by reducing the losses from the reflections and filtering of the high harmonics, and an unprecedented 19&#x0025; transmission rate from the generation point to the target position is achieved. At the same time, the probe beam is also annular and low loss of this beam is reached by using another holey mirror to combine with the APT. The advantages of using an annular beam to generate attosecond pulses with a high-average power laser are demonstrated experimentally and theoretically. The effect of nonlinear propagation in the generation medium on the annular-beam generation concept is also analyzed in detail.

Peng Ye

L&#x00E9;n&#x00E1;rd Guly&#x00E1;s Oldal

Tam&#x00E1;s Csizmadia

Zolt&#x00E1;n Filus

T&#x00ED;mea Gr&#x00F3;sz

P&#x00E9;ter J&#x00F3;j&#x00E1;rt

Imre Seres

Zsolt Bengery

Barnab&#x00E1;s Gilicze

Subhendu Kahaly

Katalin Varj&#x00FA;

Bal&#x00E1;zs Major

High-Flux 100&#x2009;kHz Attosecond Pulse Source Driven by a High-Average Power Annular Laser Beam

The last few decades have witnessed the extraordinary advances in theoretical and experimental tools, which have enabled the manipulation and monitoring of ultrafast dynamics with high precisions. For modeling dynamical responses beyond the perturbative regime, computational methods based on time-dependent density functional theory (TDDFT) are the optimal choices. Here, we introduce TDAP (time-dependent ab initio propagation), a first-principle approach that is aimed at providing robust dynamic simulations of light-induced, highly nonlinear phenomena by real-time calculation of combined photonic, electronic, and ionic quantum mechanical effects within a TDDFT framework. We review the implementation of real-time TDDFT with numerical atomic orbital formalisms, which has enabled high-accuracy, large-scale simulations with moderate computational cost. The newly added features, i.e., the time-dependent electric field gauges and controllable ionic motion make the method especially suitable for investigating ultrafast electron-nuclear dynamics in complex periodic and semiperiodic systems. An overview of the capabilities of this first-principle method is provided by showcasing several representative applications including high-harmonic generation, tunable phase transitions, and new emergent states of matter. The method demonstrates a great potential in obtaining a predictive and comprehensive understanding of quantum dynamics and interactions in a wide range of materials at the atomic and attosecond space-time scale.

Mengxue Guan

Daqiang Chen

Shiqi Hu

Hui Zhao

Peiwei You

Sheng Meng

Theoretical Insights into Ultrafast Dynamics in Quantum Materials

Wettability is one of a solid surface&#x2019;s fundamental physical and chemical properties, which involves a wide range of applications. Femtosecond laser microfabrication has many advantages compared to traditional laser processing. This technology has been successfully applied to control the wettability of material surfaces. This review systematically summarizes the recent progress of femtosecond laser microfabrication in the preparation of various superwetting surfaces. Inspired by nature, the superwettabilities such as superhydrophilicity, superhydrophobicity, superamphiphobicity, underwater superoleophobicity, underwater superaerophobicity, underwater superaerophilicity, slippery liquid-infused porous surface, underwater superpolymphobicity, and supermetalphobicity are obtained on different substrates by the combination of the femtosecond laser-induced micro/nanostructures and appropriate chemical composition. From the perspective of biomimetic preparation, we mainly focus the methods for constructing various kinds of superwetting surfaces by femtosecond laser and the relationship between different laser-induced superwettabilities. The special wettability of solid materials makes the femtosecond laser-functionalized surfaces have many practical applications. Finally, the significant challenges and prospects of this field (femtosecond laser-induced superwettability) are discussed.

Jiale Yong

Qing Yang

Xun Hou

Feng Chen

Nature-Inspired Superwettability Achieved by Femtosecond Lasers

Ultrafast laser oscillators are indispensable tools for diverse applications in scientific research and industry. When the phases of the longitudinal laser cavity modes are locked, pulses as short as a few femtoseconds can be generated. As most high-power oscillators are based on narrow-bandwidth materials, the achievable duration for high-power output is usually limited. Here, we present a distributed Kerr lens mode-locked Yb:YAG thin-disk oscillator which generates sub-50&#x2009;fs pulses with spectral widths far broader than the emission bandwidth of the gain medium at full width at half maximum. Simulations were also carried out, indicating good qualitative agreement with the experimental results. Our proof-of-concept study shows that this new mode-locking technique is pulse energy and average power scalable and applicable to other types of gain media, which may lead to new records in the generation of ultrashort pulses.

Jinwei Zhang

Markus P&#x04E7;tzlberger

Qing Wang

Jonathan Brons

Dominik Bauer

Dirk Sutter

Vladimir Pervak

Alexander Apolonski

Ka Fai Mak

Vladimir Kalashnikov

Zhiyi Wei

Ferenc Krausz

Oleg Pronin

Distributed Kerr Lens Mode-Locked Yb:YAG Thin-Disk Oscillator

About this journal

The Open Access journal Ultrafast Science, published in association with&nbsp;Xi’an Institute of Optics and Precision Mechanics, is a&nbsp;platform for cutting-edge and emerging topics in ultrafast science with broad interest from scientific communities.

Journal profile

Meet the editorial board

Ultrafast Science's editorial board is led by Qihuang Gong (Peking University)&nbsp;and Wei Zhao (Xi'an Institute of Optics and Precision Mechanics, CAS),&nbsp;and is comprised of experts who have made significant and well recognized contributions to the field of ultrafast science.

Editorial board

Learn more

Ultrafast Science is accepting submissions for its first special issue,&nbsp;<a href="https://spj.sciencemag.org/ultrafast-science-special-issues/attosecond/">Attosecond Science and Technology</a>, through June 30, 2022. Submit today!

Announcements and news

Author guidelines

Databases and indexing

Ultrafast Science - Table of contents 2022

Ultrafast Science | Science Partner Journal

title

The Open Access journal Ultrafast Science, published in association with Xi’an Institute of Optics and Precision Mechanics, is a platform for cutting-edge and emerging topics in ultrafast science with broad interest from scientific communities.