Complexity is a notion that has several denotations. When applied to wave propagation, in highly nonlinear regimes, we first consider statistical phenomena, as rare events, and lastly, we resort to strongly interacting dynamics, as in turbulence and spin glasses. Nonlinear optical phenomena cover all the aspects of modern complexity, leading to impressive results as the first observation of replica-symmetry breaking. The tour also includes the more recent topological concepts, which are useful in classifying extreme waves, like shocks, rogues, and soliton gases. Nowadays, one can also benefit from machine learning and artificial intelligence, as the highly nonlinear and disordered models have a remarkable rule in large-scale deep neural networks. One can use waves to solve computationally demanding tasks, as in the optical Ising machines. Reservoir computing in multiple scattering media may open the way to new applications in quantum optics and biomedicine. I will review all these links between nonlinear waves and complexity.

Prof. Claudio Conti (Department of Physics, University Sapienza, Rome, Italy) is the Director of the Institute for Complex Systems of the Italian Research Council (ISC-CNR). Formerly New Talent of the Enrico Fermi center, grantee of the European Research Council, and Humboldt fellow, his main research interests include nonlinear spatiotemporal bullets and X-waves, nonlocal nonlinear optics, extreme phenomena as rogue waves and optical turbulence, Anderson localization of light, and topological photonics. More recently he led the experiments demonstrating the first observation of replica symmetry breaking in random lasers and nonlinear optical propagation. Other recent work includes the realization of Ising machines and deep learning with nonlinear optics. He published more than 200 articles in international journals with more than 30 papers in Physical Review Letters and ten papers in Nature journals.
Website: www.newcomplexlight.org

The Stern-Gerlach effect, separating the electron spin components of Silver atoms that pass in a transversely varying magnetic field, is considered one of the cornerstones of quantum mechanics. I will discuss an analogue effect in nonlinear optics, based on the mixing of two different light waves (signal and idler waves) in a quadratic nonlinear crystal.
The dynamics of the nonlinear sum frequency generation process is similar to that of many other two-level systems, and in particular to spin-1/2 particles in magnetic field. Therefore, light beams that carry signal-idler superposition states can be spatially separated by transversely varying the nonlinear optical coupling [1]. When non-classical light, consisting of a signal-idler two-photon pair, is sent into the nonlinear Stern-Gerlach device, these photons emerge together at one of the two output ports, thus representing the frequency domain analogue of the famous Hong-Ou-Mandel interference experiment [2]. Furthermore, this concept can be further extended to higher dimensions in the frequency domain, by using quasiperiodic crystals that support two sum frequency generation processes.
[1] A. Karnieli and A. Arie, “All-Optical Stern-Gerlach Effect”, Physical Review Letters 120, 053901 (2018).
[2] A. Karnieli and A. Arie, “Frequency Domain Stern-Gerlach Effect for Photonic Qubits and Qutrits”, Optica 5, 1297-1303 (2018).

Prof. Ady Arie received his Ph.D. degree in Electrical Engineering from Tel-Aviv University, Israel, in 1991. Between 1991 and 1993 he was a Wolfson and Fulbright postdoctoral scholar at Stanford University, U.S.A. In 1993 he joined School of Electrical Engineering at Tel-Aviv University and became a Full Professor in 2006. He served as the Head of the School of Electrical Engineering in the years 2013-2017. Currently he is the Head of the Tel Aviv University Center for Light-Matter Interaction and the incumbent of the Marko and Lucie Chaoul Chair in Nano-Photonics.
Prof. Arie is a Fellow of the Optical Society of America. In the years 2008-2014 he served as a Topical Editor of Optics Letters and since 2018 he is an Associate Editor in Optica. His research in the last years is in the areas of nonlinear optics – in particular periodic and quasi-periodic nonlinear photonic crystals, nonlinear beam shaping and control – as well as in electron microscopy and plasmonics.

In the past decade, the development of artificial materials exhibiting novel optical properties has become one of the major scientific endeavors. One system of particular interest is with bio-soft-matter, which play a central role in numerous fields ranging from life sciences to chemistry and physics. In this talk, I will present a brief overview of our work on a few types of soft-matter systems with synthetic optical nonlinearities, including dielectric and plasmonic nanosuspensions. I will then focus on discussion about our recent work on nonlinear optics with biological suspensions, including self-trapping and guiding of light in colloidal suspensions of algal cells and human red blood cells, where the tunable nonlinearity is largely attributed to the optical forces acting on the cells.

Zhigang Chen earned his Ph.D. from Bryn Mawr College and did his postdoctoral research at Princeton Univ before joining the faculty at San Francisco State Univ in California. He is currently a specially appointed professor at Nankai University, China. He has published over 200 papers in refereed journals including some 20 PRLs, with an h-index of 48 (according to Web of Sci.). Dr. Chen is a Fellow of the Optical Society of America and a Fellow of the American Physical Society. He is a Topical Editor for Optics Letters, and served as a Program/General Chair for CLEO-Fundamental Science in 2016/18.

It is known that in an intense laser field of a sufficiently high strength combined with a sufficiently long wavelength, i.e., in the regime of the Keldysh parameter γ < 1, photoionization of atoms and molecules can be realized through a quantum tunnelprocess. The tunnel ionization preferentially occurs from the orbital with the lowest ionization energy, thus the majority of the generated ions will stay on the ground state. It is surprising that tunnel ionization of nitrogen molecules with mid- and near-infrared intense laser fields can initiate strong laser-like emissions, indicating generation of stimulated emissions in molecular nitrogen ions. The physical mechanism behind the observation is still under debate. Here, we review the major progresses we made in the past a few years. The focus is placed on investigations on the lasing action at 391 nm wavelength initiated by either mid-infrared strong laser fields in the wavelength range from 1.2 to 2 μm or near-infrared intense laser fields around 800 nm wavelength. We reveal that the mechanisms of lasing actions are different for the pump lasers in the above two spectral regions. We also show that the coherent wavepackets of molecular nitrogen ions generated in the intense laser fields uniquely allow for efficient nonlinear interaction with light at resonance frequencies.

Professor Ya Cheng's research mainly focuses on ultrafast nonlinear optics and femtosecond laser micro- and nanofabrication. Currently, he is the Dean of the School of Physics and Materials Science, East China Normal University, and the Professor of Shanghai Institute of Optics and Fine Mechanics, CAS.

In this talk I will report our work on high flux attosecond generation. We propose a new approach for producing high flux isolated attosecond pulses(IAP) based on non-collinear geometry of high-order harmonic generation (HHG). By combining a main driving pulse and an ultrashort gating pulse in the interaction medium to form a tilt wavefront in a narrow overlapping time region, the attosecond pulses generated in this region are spatially separated from the original beam in the far field. It gives a way of extracting IAP as well as fully characterizing attosecond pulse train (APT). Since the new approach set no restriction on the pulse duration of the main driving pulse, it is particularly suitable for high flux IAP generation by high energy laser which usually has multicycle pulse duration.

He Xinkui received his PH. D. in high intense field laser physics at Shanghai Institute of Optics and fine Mechanics Chinese Academy of Sciences in 2005. From 2005 to 2007, He worked as a postdoc in the Institute of Solid State Physics in the University of Tokyo. From 2007 to 2010, He was a postdoctoral researcher supported by the prestigious Marie Curie Incoming International Fellowship working at atomic physics department Lund laser centre of Lund University. In 2011, he got his present position, associate professor in the Institute of Physics Chinese Academy of Sciences.
His scientific research field is high intense laser physics, including development of ultra-fast high power laser and study of the intense laser matter interaction. Currently he is concentrating on high-order harmonic generation from odd gas driven by ultra-fast high power laser. Develop usable table-top XUV source by improving and optimizing high harmonic generation. Investigate the application of this exciting source such as XUV imaging, nonlinear optics in XUV range. The most important application of the high order harmonic generation is attosecond physics, which is now his main research content. Including the generation and characterizations of attosecond pulses and using the generated pulses to investigate the ultrafast dynamics of the electric wave package with attosecond time resolution.

Tunable photonic microstructure materials play an important role in the fields of integrated photonic devices and circuits. Ultrafast response time could be reached by using all-optical control method based on third-order optical nonlinearity. Several photonic microstructure materials, including photonic crystal topological insulator, metamaterials, and plasmonic nanostructure were fabricated and all-optical tunability was realized.

Xiaoyong Hu is the professor of physics at Peking University. He worked as a postdoctoral fellow with Prof. Qihuang Gong at Peking University from 2004 to 2006. Then he joined Prof. Gong’s research group. Prof. Hu’s current research interests include photonic crystals and nonlinear optics.

As one dramatic manifestation of electron-electron correlation in nature, strong laser field-induced nonsequential double ionization (NSDI) has continued to receive intense experimental and theoretical attention. The interpretation of NSDI is now based on the recollision scenario, which is also responsible for many other strong field phenomena. We experimentally investigate atomic NSDI and show that the recollision impact direct double ionization by elliptical polarized laser pulses can be used to timing the ultrafast dynamics of recollision and correlated electron energy sharing processes therein. Additionally, we find that recolliding electron impact excitation cross section is vital in describing wavelength dependent NSDI of magnesium atoms, which is different from the well-studied rare gases.

Dr. Huipeng Kang is a Postdoctoral Research Fellow at Friedrich Schiller University Jena in Germany. He received his PhD in Atomic and Molecular Physics from Wuhan Institute of Physics and Mathematics of Chinese Academy of Sciences, and he was a postdoc supported by the Alexander von Humboldt Foundation at Goethe Universität Frankfurt before joining Friedrich Schiller University Jena. His research interests are ultrafast dynamics of atoms and molecules exposed to intense femtosecond laser pulses. Combined with S-matrix simulations and semi-classical model, his recent researches aim at interpreting the underlying physics of strong-field ionization of atoms and molecules, and ultrafast quantum control electrons by shaping the laser pulses. His research results have been published in Physical Review Letter, Physical Review A, Optics Express as the first or co-author (citation>300).

High energy carrier envelope phase (CEP) stable near-single-cycle pulse in the mid-infrared (MIR) 3-5 μm spectral range attracted much attention in many areas of unexplored strong field physics, such as high harmonic generation (HHG) for extending cutoff energy to keV range to generate broadband and isolated ultrashort coherent soft x-ray pulse.
We have demonstrated the 800nm few cycle laser pulse compression, and extend the working wavelength to 1.8μm with carrier envelope phase (CEP) stability. Recently, a CEP stable near-single-cycle 4 μm laser system is demonstrated, which can deliver laser pulse with 2.6 mJ/21.5 fs operating at 100 Hz repetition rate with <2 optical cycle pulse duration. The system is based on a collinear OPCPA and a hollow-core-fiber (HCF) based further compression scheme. In this laser, OPCPA is used which has tremendous potential for higher output capability with higher pump, and HCF based post-compressor is employed for further compression which can be applied for MIR laser with longer wavelength.
Further, we developed two beam OPCPA MIR femtosecond laser outputs with synchronization. The coherent beam combination based on HCF has been demonstrated.

Yuxin Leng, Ph.D. he is a professor in State Key Laboratory of High Field Laser Physics at SIOM. He is currently investigating development and application of high field ultrafast laser, including optical parametric chirped pulse amplification (OPCPA); the ultra-intense and ultra-short laser based on Ti:sapphire chirped pulse amplifier; and carrier-envelopment phase (CEP) stabilized tunable high intense ultra-short infrared coherent radiation source; new laser source and its applications.

The impact of the carrier-envelope phase (CEP) of an intense multi-cycle laser pulse on the radiation of an electron beam during nonlinear Compton scattering is investigated. We have identified a CEP effect specific to the ultrarelativistic regime. When the electron beam counterpropagates with the laser pulse, pronounced high-energy x-ray double peaks emerge near the backward direction relative to the initial electron motion. This is achieved in the relativistic interaction domain, where both the electron energy is required to be lower than for the electron reflection condition at the laser peak and the stochasticity effects in the photon emission to be weak. The asymmetry parameter of the double peaks in the angular radiation distribution is shown to serve as a sensitive measure for the CEP of up to 10-cycle long laser pulses and can be applied for the characterization of extremely strong laser pulses in present and near future laser facilities.

Prof. Dr. Jianxing Li received his Ph.D. degree in 06.2011 at Nankai University, China. Afterwards, he moved to Max-Planck Institute for Nuclear Physics, Germany, for postdoctoral research until 08.2017. Since he did great research achievements in the topics of strong laser QED and laser plasma interaction, he received a full-professor position in Xi’an Jiaotong University, China at 09.2017. Right now, he is leading a strong laser QED group there. Recently, he and his colleagues developed a new method to detect robust signatures of quantum radiation reaction in focused ultrashort laser pulses [Phys. Rev. Lett. 113, 044801 (2014); Phys. Rev. A 98, 052120 (2018)], proposed a laser-electron-reflection regime to generate attosecond and vortex Gamma-ray pulses via nonlinear Compton scattering in the radiation-dominated regime, respectively [Phys. Rev. Lett. 115, 204801 (2015); Phys. Rev. Lett. 121, 074801 (2018)], presented a potential radiation-stochasticity-effects observation method via photon angle-resolved spectra [Sci. Rep. 7, 11556 (2017)], and invented an approach for the determination of the carrier-envelope phase of current available and under construction PW laser pulses [Phys. Rev. Lett. 120, 124803 (2018); Phys. Rev. A 99, 013850 (2019)].

Isotropic refractive index near zero relaxes certain phase-matching limits, allowing for more flexible configurations of nonlinear devices with dramatically reduced footprints. We designed and fabricated an on-chip integrated metamaterial with a refractive index of zero in the optical regime, opening the door to exploring the physics of light propagation in zero-index media. We demonstrated that the index of refraction is zero, by observing the refraction of light though a prism made of this metamaterial and by directly observing the (infinite) effective wavelength in a zero-index waveguide. The zero-index metamaterial can be fabricated using standard planar processes over a large area and in any shape, and can be impedance matched to other optical components, so it can be readily integrated in nonlinear photonic circuits.

Yang Li received B.S. degree in telecommunication engineering (2006) and M.S. degree in electromagnetic field and microwave technology (2008) from Huazhong University of Science and Technology, China, and Ph.D. degree in Electrical Engineering (2012) from Iowa State University. From 2013 to 2018, Yang Li was a Postdoctoral Fellow of Mazur group at Harvard University. Yang Li’s current research interests include integrated metamaterials, nanophotonics, quantum photonics, electromagnetic nondestructive evaluation. Yang Li received the IEEE Antennas and Propagation Society Doctoral Research Award and was nominated for the R.W.P. King Award. Yang Li was a Co-PI of several NSF and Samsung grants.

The interaction of strong laser pulses with atoms can induce highly nonlinear processes such as above-threshold ionization and high-order harmonic generation. The differential distribution of the ionized electron or the harmonic radiation is sensitively dependent on the specific laser parameters. In this talk, we will discuss several examples of how one can use the strong field ionization to accurately characterize some specific parameters of the laser pulse. The first example is how one can in situ measure the ellipticity of the pulse based on sub-cycle ionization dynamics by two time-delayed identical counterrotating elliptically polarized laser pulses. The second one is how to extract the tiny electron displacement that can be induced by a short laser pulse by using a ruler formed by the interfering spirals in the photoelectron momentum distribution generated by two oppositely circularly polarized pulses. Finally, we will discuss the possibility to retrieve the waveform of an IR pulse by the attosecond streaking of a degenerate state.

Liang-You Peng is currently a Boya Professor of Physics at Peking University, Beijing，China. In 1998, Dr. Peng was awarded bachelor degree in physics from Central China Normal University, Wuhan, China. He received his PhD in 2005 from Queen’s University Belfast, UK, after which he did his postdoctoral research at the University Nebraska-Lincoln, USA. Since 2007, he has been a faculty member in the School of Physics, Peking University. His main research interest focuses on the theoretical and computational studies on the dynamics of the laser-matter interaction, in particularly those processes in the few-body atomic and molecular systems and the solid targets.
http://www.phy.pku.edu.cn/~lypeng/

Intermolecular Coulombic decay (ICD) in clusters plays an important role for the production of highly active secondary species like low-energy electrons. ICD has been studied in numerous systems, e.g. in the Van-der-Waals clusters, hydrogen-bonding water dimers and larger water clusters as well as in the biochemically relevant systems associated with water.
Here, we investigate ICD in mixed clusters consisting of water and bio-relevant molecules. The biomolecule employed here is tetrahydrofuran (THF, C₄H₈O) which is often regarded as being an analog of the sugar ring in the DNA backbone linking the phosphate groups and the DNA bases. Experiments were carried out using a multi-particle imaging spectrometer (reaction microscope) in which the kinetic energies of final state electrons and ions are measured. The projectile electron energy of 66 eV is chosen to be in the range of the mean energy of secondary electrons which are produced in great numbers by any high-energy ionizing radiation.

Professor Xueguang Ren is an experimentalist working in the research field of atomic, molecular and cluster science. E.g. Electron momentum spectroscopy, electron-impact ionization dynamics of atoms, molecules and clusters etc.; developments of (e, 2e) coincidence techniques and reaction microscope or multi-particles coincidence momentum spectrometer induced by electron-impact and ion collisions. Professor Ren has engaged international collaboration in the experimental and theoretical study of ionization dynamics including countries from France, Germany, USA, Czech Republic, etc.

Ferroelectric materials exhibit natural tendency to form finite size (macroscopic) domains of electric polarization. These domains have different orientations and coexist in the medium being separated by domain walls. Domain formation has been a subject of continuous research interest and investigations because of a number of actual and potential applications of domain structures in a variety of fields, including linear and nonlinear optics (e.g. optical signal modulation, frequency conversion, nonlinear volume holography), future electronics, non-volatile memories, photovoltaics. In this talk we present our latest study of ferroelectric domain formation and engineering with tightly focused femtosecond laser beams. The unique features of this, discovered by us, domain formation process based on interaction of high-intensity ultrashort light pulses with ferroelectric, allows one not only to study the fundamental physics of micro- and nano-engineered domains in the important class of materials of ferroelectrics, but also to overcome the insurmountable challenge of the other traditional poling techniques by doing it in 3-D without any restrictions imposed on the material orientation and the domain pattern geometry to be inscribed.

Dr. Yan Sheng received her PhD degree in Optical Physics from the Institute of Physics, Chinese Academy of Science (Beijing, China) in 2007. After this she undertook a two-year postdoctoral position at Max-Planck Institute for Polymer Research (MPIP), Mainz, Germany. This period involved versatile research programs in nonlinear optics and materials. In March 2010, she joined Laser Physics Center, Australian National University as an Australian Postdoctoral Fellow (APD) to continue her research in nonlinear optics. Dr. Sheng currently is a Fellow at the Australian National University and her research interests include nonlinear photonic crystals, quasi-phase matching, and direct femtosecond laser writing technique.

A stable multi-TW three-channel optical waveform synthesizer is demonstrated and used for reproducibly generating a high-order harmonics super-continuum in the soft-x-ray region. This synthesizer is composed of pump pulses from a 10-Hz repetition rate Ti:sapphire pump laser and signal and idler pulses from an infrared two-stage optical parametric amplifier driven by this pump laser. With the full active stabilization of all relative time delays, relative phases, and carrier-envelope phase, a shot-to-shot stable intense continuum harmonic spectrum is obtained around 60 eV with a pulse energy above 0.24 uJ. The peak power of the soft-x-ray continuum is evaluated to be beyond 1 GW with 140 as transform limit duration, which indicates the feasibility to perform pump-probe spectroscopy with isolated attosecond pulses in the soft-x-ray region.

Eiji J. Takahashi is a Senior Research Scientist in the Extreme Photonics Research Group, RIKEN. His research interests include high-intensity laser-matter interactions, generation of coherent soft-x-ray/XUV pulses, attosecond science, and high-power laser technology.

Among natural energy resources, methane clathrate has attracted tremendous attention because of its strong relevance to current energy and environment issues. Yet little is known about how the clathrate start to nucleate and disintegrate at the molecular level, because such microscopic processes are difficult to probe experimentally. Using surface-specific sum-frequency vibrational spectroscopy, we have studied in situ the nucleation and disintegration of methane clathrate embryos at the methane gas/water interface under high pressure and different temperatures. Before appearance of macroscopic methane clathrate, the interfacial structure undergoes three stages as temperature varies, namely, dissolution of methane molecules into water interface, formation of cage-like methane-water complex, and appearance of microscopic methane clathrate, while the bulk water structure remains unchanged. We find a clear vibrational spectral feature of the methane-water complex, which is the intermediate microscopic structure appears in induction time. Its structure is rather stable in a wide temperature window, the existence of which is associated with the so-called “memory effect” during re-crystallization from a melted solid clathrate. Our findings not only provide a better microscopic understanding on the nucleation mechanism of clathrates, but also open up an opportunity for rational control of their formation and disintegration.

Optical waves, acoustic waves, and microwaves usually do not mix together in the same physical platform due to their inherent distinct wave nature. However, at the microscopic scale, these waves can unexpectedly interact with the same microstructure through resonant enhancement, making it unique hybrid micro-system for new application across multiple physical channels. Here we experimentally demonstrate an optomechanical microdevice based on Brillouin lasing operation in an optical microcavity as a sensitive unit to sense external light, sound, and microwave signals in the same platform. These waves can induce modulations to the microcavity Brillouin laser in a resonance-enhanced manner through either the pressure forces including the optical radiation pressure force or the thermal absorption according to its physical nature, allowing several novel applications such as broadband none-photovoltaic detection of light, sound-light dual channel communication and deep-subwavelength microwave imaging. These results pave the way towards on-chip integrable optomechanical solutions for sensing, free-space secure communication, and microwave imaging.

Wenjie Wan received the B.E. from the Hong Kong University of Science and Technology in 2004 and Ph.D from at Princeton University in 2010, both in Electrical Engineering. After one year postdoctoral training at Yale University, he joint UM-JI as Assistant Professor and jointly appointed by Department of Physics, SJTU. Dr. Wan’s publications include Science, Nature Physics, Nature Photonics and Physical Review Letters. He is the recipient of the 2009 Chinese Government Award for Outstanding Self-Financed Students Abroad. In 2011, he is awarded “1000 people's plan (youth)” by Chinese Government.

The demand for an ultrabroad optical material with a bandgap tunable from zero to at least 1~2 eV has been one of the driving forces for exploring new 2D materials since the emergence of graphene, transition metal dichalcogenides and black phosphorus. As ultra-broadband 2D materials with energy bandgap ranging from 0 to 1.4eV, layered PtSe₂ and nonlayered PtS show much better air stability than black phosphorous. In this work, both high quality of centimeter scale PtSe₂ and PtS films with controllable thicknesses were prepared through thermally assisted conversion method. The nonlinear optical performance and ultrafast dynamics have been systematically studied experimentally and theoretically. In the layered PtSe₂, the optical bandgap increased with the sample thickness decreasing, which is opposite in the nonlayered PtS films. Besides, we found a transition from semiconductor to semimetal in PtSe₂, however, we have not observed this phenomenon in PtS. Combining with rate equation, first principle calculation, electrical measurements and a model based on quantum mechanical wave function, we provide a comprehensive understanding on the evolution of nonlinear optical properties and ultrafast carrier dynamics. These results are important to explore nonlinear optical devices based on the 2D materials, such as saturable absorber, optical switches, etc.

Jun Wang is a professor with Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences (CAS). He obtained the PhD degree from the Chinese University of Hong Kong in 2006. Then he was granted an IRCSET postdoctoral fellowship and worked at Trinity College Dublin, Ireland. In 2011, he relocated his research activities to SIOM under the financial support from the 100-Talent Program of CAS. In 2018 and 2015, he was awarded by the National 10000-Talent Program and National Natural Science Foundation-Outstanding Youth Foundation, respectively. His research interests are focused on nonlinear optics in low-dimensional materials. So far, he has published more than 130 peer-reviewed SCI journal papers in Nature Nanotech., Prog. Mater. Sci., Adv. Mater., Nature Commun., ACS Nano, Laser Photon. Rev., etc., including 8 ESI papers and having over 4000 citations.

The primary phase of the light-molecule interaction is the photon energy absorption and deposition. Although the electron is much lighter than the nuclei, there is a strong electron-nuclear correlation for molecules exposed to strong laser fields. Here, we experimentally reveal the correlated electron-nuclear dynamics by measuring the electrons and nuclear fragments ejected from a single molecule in coincidence. Our experimental results show that the electron and nuclei in a molecule share the absorbed multiphoton energy in a correlative manner [1,2]. The molecule as a whole absorbs the photon energy. The electron-nuclear energy sharing assisted by the rescattering lead to the observation of long-term predicted photon-energy spaced above threshold dissociation spectrum of breaking molecules [3], which is the interference of the periodically emitted electron-nuclear wave packet in the oscillating strong laser fields. Interestingly, for molecules in strong laser fields, a liberated electron can be recaptured by the ejected ionic fragments, leading to the formation of the excited Rydberg fragments. We real-time observe and further directionally control the dissociative frustrated double ionization of hydrogen molecules [4]. The frustrated double ionization of molecules can be generally understood in a multiphoton route by considering the correlated dynamics of electrons and nuclei of the molecule [5].
References
[1] Phys. Rev. Lett. 111, 023002 (2013).
[2] Phys. Rev. Lett. 117, 103002 (2016).
[3] PNAS 115, 2049 (2018).
[4] Phys. Rev. Lett. 119, 253202 (2017).
[5] Nature Communications 10, 757 (2019).

Wu Jian, Professor of the State Key Laboratory of Precision Spectroscopy, East China Normal University (ECNU). He received his B.S. and Ph.D. degrees from ECNU. He was appointed as an Associated Professor at ECNU in 2007 and promoted to be a full Professor in 2010. With a grant from the Alexander von Humboldt Foundation, he carried out his postdoctoral research at the Goethe University Frankfurt. He was selected as the Distinguished Young Scholars of NSFC (2014), Ten-thousand Talents Program (2019), National Youth Top-notch Talents (2015), the New Century Excellent Talents in University (2013), and the Eastern Scholar of Shanghai Municipal Education Commission (2013). He was invited to serve as the International Advisory Board of the Journal of Physics B (Royal Society of Physics). His research focuses on the measurement and control of the ultrafast dynamics of molecules in strong laser fields. He has published more than 100 papers in peer-reviewed journals, including 19 PRL, 1 PNAS, 1 PRX, and 5 Nature Communications.

The f-2f interferometry is the most common method in measuring the Carrier Envelope Phase (CEP) of femtosecond laser pulses. It is mainly used to detect the CEP jitter in a feedback loop. For the pulse to be measured, one octave spanning spectrum is necessary, but the spectral broadening process would worsen the pulse coherence and introduce phase uncertainty. The phase noise is significantly affected by the characteristics of input pulses, and cannot be suppressed by the feedback loop. Current CEP jitter locked by the f-2f feedback loop is the result of CEP jitter which contains the noise introduced by the entire system instead of the laser alone. In order to eliminate the disturbance, we simulated the phase deviation introduced by the spectral broadening process and the measurement uncertainty caused by limited detector resolution. Combined with the error analysis, a method for measuring the true CEP jitter value of the laser itself was proposed. Furthermore, different spectral broadening process are applied to compare and verify the truly CEP deviation of the laser. This method will provide a more accurate standard for time domain control of ultrafast laser pulses.

Dr. ZHAO received his B.S. in Physics at Peking University in 1995 and Ph.D. in Chemical Physics at University of Maryland in US in 2006. Afterward, he worked as a postdoc at University of Nebraska and Kansas State University. In 2011, he joined University of Central Florida as an assistant professor, and was elected to be a senior member of the Optical Society (OSA). He came back to China in 2014 to join the Institute of Physics, Chinese Academy of Sciences. In 2018, he became a committee member of the International Conference of Attosecond Science and Technology. His primary research area is ultrafast optics, including attosecond optics, strong field ionization, femtosecond lasers, and ultrafast dynamics. His major achievements include the generation and characterization of 67-attosecond (2012) and 53 attosecond (2017) XUV pulses, and supercontinuum and few-cycle femtosecond pulse generation in solid thin plates. He has published over 60 journal papers, conference proceedings, book chapters, and patents, which have been cited over 1100 times.

Tunneling ionization of atoms or molecules by a strong laser field generates an electron wavepacket. This electron wavepacket could reach the detector directly or undergoes rescattering by the parent ion, giving rising to the interference in the photoelectron momentum distribution (PEMD), referred as photoelectron holography in strong field tunneling ionization. This holograms can be used to probe the structural and dynamic information of the targets. We will demonstrated the application of this holography in the extracting the phase of elastic scattering amplitude [1]. This holography also possesses the attosecond time resolution and could be used to trace the valence electron motion in molecules. We will also show how the information of valence electron motion is encoded in the hologram of the PEMD and theoretically demonstrate that the attosecond charge migration in H₂⁺ is directly visualized with picometer spatial and attosecond temporal resolutions in a single-shot measurement [2]. Moreover, this photoelectron holography could provide information about the tunneling ionization process itself. Adding a weak perturbation in orthogonal to the strong fundamental field, the hologram is shifted. By analyzing the response of the hologram to the perturbation, the real part of the tunneling ionization time, which denotes the instant when the electron exits the potential barrier, and the imaginary part of the tunneling ionization time, which has been interpreted as a quantity related to electron motion under the potential barrier, can be also precisely determined [3].
[1] Y. Zhou, O. Tolstikhin and T. Morishita, Phy. Rev. Lett. 116, 173001 (2016).
[2] M. He, Y. Li, Y. Zhou et al, Phy. Rev. Lett. 120, 133204 (2018).
[3] J. Tan, Y. Zhou, M. He et al, Phy. Rev. Lett. 121, 253203 (2018).

Yueming Zhou is a professor in Huazhong University of Science and Technology. He received his Ph.D. Degree in 2013 at HUST. Then he carried out his postdoc in the University of electro-communications in Japan, with the grant from JSPS. His mainly research field is the interaction of strong laser field with atoms and molecules, in particularly the correlated electron dynamics in strong field double ionization, and attosecond photoelectron holography in strong field tunneling ionization.