LPHYS'26.    Plenary Speakers:

  1. Generation of Terahertz Pulses by Laser-Plasma Interactions: From Microjoule to Joule-Class Energy

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      Luc Bergé


      Centre Lasers Intenses et Applications (CELIA), University of Bordeaux, CEA, CNRS, Talence, France
    Biography:

    Luc Bergé graduated in mathematics and physics from the Universities of Toulouse and Paris-Sud, Orsay, France. In 1990, he was employed as a research scientist, then head of laboratory at CEA (French Commission for Atomic Energy and Alternative Energies). Since 2023, he has been working as a research director at CELIA, Bordeaux University. He mostly dedicated his research to the filamentation of ultrashort laser pulses in transparent media and related properties such as pulse self-compression, which he pioneered in the early 2000s. Nowadays, he focuses his activities on terahertz pulse generation by femtosecond pulses ionizing gases and solids.

    Luc Bergé is a Fellow of Optica, EPS, EOS, and APS. He received the 2018 Gentner–Kastler Prize, jointly attributed by the German and French Physical Societies, and the 2025 Humboldt Research Award. Between 2021 and 2024, he was President of the European Physical Society.

    Abstract:

    Terahertz (THz) pulses are very popular because of their numerous applications in security screening, medical imaging, time-domain spectroscopy, and remote detection. Gas plasmas created by two-color femtosecond optical pulses at moderate intensity – i.e. at intensity close to the ionization threshold – supply suitable and undamaged emitters. Electrons are tunnel ionized by an asymmetric light field usually composed of a fundamental wavelength and its second harmonic. The resulting “photocurrent” generates an ultrabroadband terahertz pulse which can be useful in, e.g., molecular spectroscopy.

    In recent years, however, THz science, generally associated with low photon energies, has seen unprecedented development thanks to the most powerful laser sources capable of delivering Joule-class THz pulses with terawatt peak powers. These pulses will no longer solely be used to probe matter, but also to ionize and transform it. A current challenge in this context is to produce broadband energetic THz pulses by irradiating gas or solid targets at relativistic laser intensities far exceeding 1018 W/cm2. In this regime, the coherent transition radiation (CTR) from electron bunches exiting the rear boundary of a fully ionized target can lead to intense THz emissions characterized by mJ-to-Joule energy yields.

    This talk will first review basic properties of µJ THz pulses generated by the two-color-driven photo-ionization of air molecules and will discuss new possibilities for controlling their polarization state. The major part of the talk will then be devoted to mJ-to-J-class THz pulses produced by relativistic plasmas. Using multidimensional particle-in-cell simulations, we will detail the mechanisms underlying THz emissions in gases and solid targets driven by ultraintense laser pulses. Special emphasis will be paid to the THz performances achieved by the CTR process when passing from a wakefield formed in underdense plasmas to solid targets with overcritical density.

  2. Quantum Engineering of Strong Field Physics

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      Thomas Brabec


      Department of Physics, University of Ottawa, Ottawa, ON, Canada
    Biography:

    Thomas Brabec received his PhD in 1992 and his Habilitation in 1997 from the Vienna University of Technology. Since 2002, he has been a Professor in the Department of Physics at the University of Ottawa and a Canada Research Chair in Ultrafast Photonics.

    His research expertise lies in ultrafast science, nonlinear optics, quantum and classical dynamics, and strong-field dynamics in gases and solids. He has authored more than 200 peer-reviewed publications in these areas, which have received broad international recognition.

    Abstract:

    Strong field physics started in atomic and molecular physics and extended over the past decade to material science. While atoms are isolated systems, in solids many-body effects due to the interaction with the environment have to be considered. As full many-body treatments are extremely challenging, this is usually done by defining an effective dephasing time T2 within the relaxation time approximation. However, the relaxation time approximation causes “dephasing ionization”, resulting in an unphysical enhancement of ionization by up to orders of magnitude. As such, a more sophisticated model is needed that ideally maintains simplicity and wide applicability of the relaxation time approximation.

    In the first part, such a (spin-boson) model will be introduced, based on a coupling between electron and a bosonic harmonic oscillator heat bath. The heat bath can accurately represent phonons, and collective electronic excitations, such as excitons, and plasmons. A parameters scan reveals that the unphysical aspects of dephasing ionization disappear; only in exotic materials with strong heat bath coupling novel ionization effects are predicted.

    In the second part, we recognize that light can also serve as a heat bath, with the advantage that nature and strength of the coupling can be controlled by pulse energy and photon distribution. Specifically, two-color experiments are discussed with a moderately intense classical laser pulse, and a perturbative quantum field, such as bright squeezed vacuum (BSV), acting as a “quantum heat bath”. Very moderate BSV fields are found to enhance ionization and HHG by orders of magnitude, thus allowing control of fundamental strong field processes. The lower required intensities remedy a key weakness of strong laser fields; that they distort the very processes they are meant to measure.

    In the last part, the quantum properties of harmonic radiation generated by a superposition of classical and perturbative quantum fields are discussed. The central idea is to transfer quantum properties from the perturbative quantum field to the harmonic pulse, thus shifting the generation of quantum pulses from the infrared into the XUV. We show how the entanglement between quantum beam and harmonics can be harnessed to create a variety of non-classical states commonly used in quantum information science, such as high purity single photon states, Schrödinger cat states, and photon added squeezed vacuum states. This opens a path towards engineering the quantum properties of ultrashort high harmonics.

  3. High-power Single-Frequency Multimode Fiber Laser Amplifiers

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      Hui Cao


      Department of Applied Physics, Yale University, New Haven, CT, USA
    Biography:

    Hui Cao is the John C. Malone Professor of Applied Physics, a Professor of Physics, and a Professor of Electrical Engineering at Yale University. She received her Ph.D. degree in Applied Physics from Stanford University in 1997. Prior to joining the Yale faculty in 2008, she was on the faculty of Northwestern University for ten years.

    Her technical interests and activities are in the areas of mesoscopic physics, complex photonic materials and devices, nanophotonics, and biophotonics. Cao is a Fellow of IEEE, AAAS, APS, and OSA, and an elected member of the National Academy of Sciences and the American Academy of Arts and Sciences.

    Abstract:

    High-power fibre lasers are powerful tools used in science, industry, and defence. A major roadblock for further power scaling of single-frequency fibre laser amplifiers is stimulated Brillouin scattering. Efforts have been made to mitigate this nonlinear process, but these were mostly limited to single-mode or few-mode fibre amplifiers, which have good beam quality.

    Recently, we explored a highly multimode fibre amplifier in which stimulated Brillouin scattering was greatly suppressed due to a reduction of light intensity in a large fibre core and a broadening of the Brillouin scattering spectrum by multimode excitation. By applying a spatial wavefront-shaping technique to the input light of a nonlinear amplifier, the output beam was focused to a diffraction-limited spot.

    Our multimode fibre amplifier can operate at high power with high efficiency and narrow linewidth, which ensures high coherence. Optical wavefront shaping enables coherent control of multimode laser amplification, with potential applications in coherent beam combining, large-scale interferometry, and directed energy delivery.

  4. Quantum Metrology for Open Systems

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      Luiz Davidovich


      Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
      Institute for Quantum Science and Engineering, Texas A&M University, College Station, TX, USA
    Biography:

    Luis Davidovich's research focuses on the dynamics of open quantum systems, combining theoretical and experimental approaches with applications in cavity quantum electrodynamics and quantum metrology. He obtained his PhD from the University of Rochester, and has since concentrated on quantum optics and quantum information. He is currently Emeritus Professor of Physics at the Federal University of Rio de Janeiro.

    He was awarded the Grand Cross of the Brazilian National Order of Scientific Merit in 2000 and received Brazil's most prestigious scientific distinction, the Admiral Álvaro Alberto Prize, from the National Research Council (CNPq) in 2010. He was also awarded the Physics Prize of The World Academy of Sciences (TWAS) in 2001 and, more recently, the Willis Lamb Award and the TWAS Apex Award in 2025.

    Luis Davidovich is a member of the Brazilian Academy of Sciences, where he served as President from 2016 to 2022, and of TWAS, where he was Secretary-General from 2019 to 2022. He is an international member of the U.S. National Academy of Sciences, the European Academy of Sciences, and the Chinese Academy of Sciences. He is also a Fellow of Optica and of the American Physical Society.

    Abstract:

    Quantum sensors are employed to estimate parameters with higher precision than classical sensors. For noiseless systems, the Cramér–Rao bound, which links estimation uncertainty to Fisher information, serves as a useful benchmark. Extending this bound to open systems has been proposed and applied to several key systems [1–4], a relevant generalization considering the widespread presence of the environment. Entanglement can then play a crucial role despite its fragility [5,6]. Interestingly, when the estimated parameter pertains to noise itself [7–9], the vulnerability of entanglement may actually enhance precision [8]. This talk reviews recent advances in this area, resulting in precision bounds for noisy systems, with applications such as estimating light absorption and depolarization.

    1. B M Escher, R L de Matos Filho, and L Davidovich, Nat. Phys. 7, 406–411 (2011). DOI: 10.1038/nphys1958.
    2. B M Escher, L Davidovich, N Zagury, and R L de Matos Filho, Phys. Rev. Lett. 109, 190404 (2012). DOI: 10.1103/PhysRevLett.109.190404.
    3. M M Taddei, B M Escher, L Davidovich, and R L de Matos Filho, Phys. Rev. Lett. 110, 050402 (2013). DOI: 10.1103/PhysRevLett.110.050402.
    4. C L Latune, B M Escher, R L de Matos Filho, and L Davidovich, Phys. Rev. A 88, 042112 (2013). DOI: 10.1103/PhysRevA.88.042112.
    5. M P Almeida, F de Melo, M Hor-Meyll, A Salles, S P Walborn, P H Souto Ribeiro, and L Davidovich, Science 316, 579-582 (2007). DOI: 10.1126/science.1139892.
    6. L Aolita, R Chaves, D Cavalcanti, A Acín, and L Davidovich, Phys. Rev. Lett. 100, 080501 (2008). DOI: 10.1103/PhysRevLett.100.080501.
    7. J Wang, L Davidovich, and G S Agarwal, Phys. Rev. Research 2, 033389 (2020). DOI: 10.1103/PhysRevResearch.2.033389.
    8. L Davidovich and R L de Matos Filho, Phys. Rev. A 108, 042612 (2023). DOI: 10.1103/PhysRevA.108.042612.
    9. J Wang, R L de Matos Filho, G S Agarwal, and L Davidovich, Phys. Rev. Research 6, 013034 (2024). DOI: 10.1103/PhysRevResearch.6.013034.

  5. Complex Bands and Topology with Coupled Lasers

    Biography:

    Prof. Nir Davidson joined the Weizmann Institute's Department of Physics of Complex Systems in 1994. He served as Head of the Department of Complex Systems (2010–2015) and as Dean of the Faculty of Physics, as well as Director of the André Deloro Institute for Space and Optics Research and the Center for Experimental Physics (2015–2021). He is the Head of the Crown Photonics Center and AMOS Domain, and the incumbent of the Peter and Carola Kleeman Professorial Chair of Optical Sciences. He was elected Vice-Chair of the Scientific Council in 2022 and Chair of the Scientific Council in 2024.

    Prof. Davidson conducts research on laser physics and ultra-cold atomic physics. The behaviour of matter at less than a millionth of a degree above absolute zero is governed by the principles of quantum mechanics. At such temperatures, particles may combine into a new state of matter known as a Bose–Einstein condensate (BEC), in which quantum behaviour can be observed on a macroscopic scale. His work focuses on manipulating atomic motion using lasers and applying this control to atomic traps that induce the BEC state, as well as on the use of such techniques for precision measurements of quantum phenomena. His long-term aim is to establish ultra-cold atoms as a tool for studying the transition from classical, Newtonian physics to quantum, nonlinear dynamics.

    Born in Ashkelon, Israel, in 1962, Prof. Davidson received a BSc from the Hebrew University of Jerusalem in 1982, an MSc from the Technion – Israel Institute of Technology in 1988, and a PhD from the Weizmann Institute of Science in 1993. This was followed by two years as a research fellow at Stanford University.

    He is the recipient of the F.W. Bessel Award from the Alexander von Humboldt Foundation (2002), the Yosefa and Leonid Alshwang Prize for Physics from the Israel Academy of Sciences and Humanities (1998), the Morris L. Levinson Prize in Physics, and the Rosa and Emilio Segrè Research Award, both awarded by the Weizmann Institute's Scientific Council (2001). He was elected a Fellow of the Optical Society of America (2011) and a Fellow of the American Physical Society (2022). From 2007 to 2011, he served as President of the Israeli Laser and Electro-Optics Society.

    Abstract:

    Complex coupling in periodic laser arrays leads to complex bands, where the real part corresponds to the dispersion relation of the band w(k) and the imaginary part corresponds to k-dependent loss. By precisely tuning the complex coupling and the array geometry, we engineer the complex bands to generate unique topological lasing states. We demonstrate how lasing at Dirac points in a hexagonal laser lattice can lead to Klein tunnelling of coherence through a barrier, and how complex Hermitian coupling can generate artificial gauge fields and edge states. Finally, we characterize the effects of quenched disorder and hint at KT physics in coupled laser arrays.

  6. Optical Computing: Principles, Examples, and Prospects

    Biography:

    Peter McMahon is an Associate Professor of Applied & Engineering Physics at Cornell University. He received his Ph.D. in Electrical Engineering from Stanford University in 2014, where he also performed his postdoctoral training in Applied Physics until starting as a faculty member at Cornell in 2019. He has received Packard and Sloan Fellowships and is the recipient of the Lomb Medal from Optica.

    Abstract:

    In this talk I will discuss how optics could in principle be used to perform some computations faster or more energy efficiently than is possible with electronics, as well as the caveats and challenges. To illustrate the principles, I will highlight various examples of theoretical proposals and experimental demonstrations from our community, showing how they aim to gain an advantage over electronics.

  7. Spin-Selective Coherent Light Scattering from Ion Crystals and Towards Scalable Quantum Computing

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      Ferdinand Schmidt-Kaler


      QUANTUM, Institut für Physik, Universität Mainz, Mainz, Germany
    Biography:

    https://physics.uni-mainz.de/profile-page-ferdinand-schmidt-kaler/

    Abstract:

    We are fascinated by the intriguing features of quantum light. Thus, we study collective light scattering off a linear crystal of 40Ca+ ions, each ion acting as a coherent single photon emitter. The scattered intensity is recorded in the far field, featuring the interference of emitted light [1-4]. Furthermore, we demonstrate spin-dependent scattering and unveil the time evolution of a previously encoded spin texture [5]. In future, we plan to detect projectively generated entanglement in larger ion crystals.

    This research is closely connected with the challenges on the way to scalable quantum computers with trapped ion qubits, and I will describe these challenges on the way to scalable, eventually fault tolerant quantum computers [6]. Efforts from physics, informatics [7,8] and mathematics, but also engineering [9], are concentrated in demonstrator setups. As a first glance into the power of quantum computing, I will describe a couple of use cases. This includes the VQE simulation of a two-flavor Schwinger quark model executed on a trapped-ion quantum processor [10], and, by extending the toolset of quantum operations, the investigation of circuits that realize quantum thermodynamic processes [11-13].

    Linear ion crystal interferenceTrap chip for quantum computing
    Left: Linear crystal of 6 ions observed in the far field and featuring interference fringes. Right: Trap chip for quantum computing fabricated by selective laser etching.
    1. F Schmidt-Kaler and J von Zanthier, Collective Light emission of ion crystals in correlated Dicke states, in Photonic Quantum Technologies - Science and Applications, ISBN: 978-3-527-41412-3, Wiley-VCH, Berlin.
    2. S Richter, S Wolf, J von Zanthier, and F Schmidt-Kaler, Phys. Rev. Research 5, 013163 (2023). DOI: 10.1103/PhysRevResearch.5.013163.
    3. S Richter, S Wolf, J von Zanthier, and F Schmidt-Kaler, Phys. Rev. Lett. 126, 173602 (2021). DOI: 10.1103/PhysRevLett.126.173602.
    4. S Wolf, S Richter, J von Zanthier, and F Schmidt-Kaler, Phys. Rev. Lett. 124, 063603 (2020). DOI: 10.1103/PhysRevLett.124.063603.
    5. M Verde, A Schaefer, B Zenz, Z Shehata, S Richter, C T Schmiegelow, J von Zanthier, and F Schmidt-Kaler, Phys. Rev. A 112, 043719 (2025). DOI: 10.1103/7bd7-4trn.
    6. J Hilder, D Pijn, O Onishchenko, A Stahl, M Orth, B Lekitsch, A Rodriguez-Blanco, M Müller, and F Schmidt-Kaler, Phys. Rev. X 12, 011032 (2022). DOI: 10.1103/PhysRevX.12.011032.
    7. F Kreppel, C Melzer, D Olvera Millán, J Wagner, J Hilder, U Poschinger, F Schmidt-Kaler, and A Brinkmann, Quantum 7, 1176 (2023). DOI: 10.22331/q-2023-11-08-1176.
    8. J Durandeau, J Wagner, F Mailhot, C-A Brunet, F Schmidt-Kaler, U Poschinger, and Y Bérubé-Lauzière, Quantum 7, 1175 (2023). DOI: 10.22331/q-2023-11-08-1175.
    9. V Kaushal, B Lekitsch, A Stahl, J Hilder, D Pijn, C Schmiegelow, A Bermudez, M Müller, F Schmidt-Kaler, and U Poschinger, AVS Quantum Sci. 2, 014101 (2020). DOI: 10.1116/1.5126186.
    10. C Melzer, S Schuster, D A Olvera Millán, J Hilder, U Poschinger, K Jansen, and F Schmidt-Kaler, arXiv: 2504.20824.
    11. E J Fox, M Herrera, F Schmidt-Kaler, and I D’Amico, Entropy 26(11), 952 (2024). DOI: 10.3390/e26110952.
    12. O Onishchenko, G Guarnieri, P Rosillo-Rodes, D Pijn, J Hilder, U G Poschinger, M Perarnau-Llobet, J Eisert, and F Schmidt-Kaler, Nat. Commun. 15, 6974 (2024). DOI: 10.1038/s41467-024-51263-3.
    13. A Stahl, M Kewming, J Goold, J Hilder, U G Poschinger, and F Schmidt-Kaler, arXiv: 2404.14838.

  8. Positron Acceleration with Transition Radiation Driven by Ultra Intense Laser at SULF and SEL

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      Baifei Shen


      ShanghaiTech University, Shanghai, China
      Shanghai Normal University, Shanghai, China
    Abstract:

    We report our progress on positron generation and acceleration. We proposed a scheme that utilizes laser-driven electrons to produce, inject, and accelerate positrons in a single setup. A high-density gas jet is employed experimentally to generate from several to hundred MeV electrons with high charge above 100 nC. Thus, positron beam with high charge is obtained during the laser-accelerated electrons irradiating high-Z solid targets [1].

    The high-charge electron beam creates copious electron–positron pairs via the Bethe–Heitler process, followed by enormous coherent transition radiation due to the electrons exiting from the metallic foil [2]. This intense transition radiation accelerates and focuses the positrons efficiently. Since the intensity of the coherent transition radiation scales to the square of the electron charge number, this scheme is extremely effective for 10–100 PW laser.

    We discuss the use of a channel to guide the transition radiation [3,4]. We propose to use diffraction radiation to extract the energy from the electron beam more efficiently [5]. This new method has been demonstrated with a 10 PW laser at SULF [6]. We are planning experiments with the 50 PW laser at SEL@SHINE in Shanghai. Other experimental plans at SEL@SHINE are also introduced.

    1. T Xu, B Shen, J Xu, S Li, Y Yu, J Li, X Lu, C Wang, X Wang, X Liang, Y Leng, R Li, and Z Xu, Phys. Plasmas 23, 033109 (2016). DOI: 10.1063/1.4943280.
    2. Z Xu, L Yi, B Shen, J Xu, L Ji, T Xu, L Zhang, S Li, and Z Xu, Commun. Phys. 3, 191 (2020). DOI: 10.1038/s42005-020-00471-6.
    3. L Yi, B Shen, L Ji, K Lotov, A Sosedkin, X Zhang, W Wang, J Xu, Y Shi, L Zhang, and Z Xu, Sci. Rep. 4, 4171 (2014). DOI: 10.1038/srep04171.
    4. Z Xu, B Shen, M Si, and Y Huang, New J. Phys. 25, 063013 (2023). DOI: 10.1088/1367-2630/acdc47.
    5. Y Ye, Z Xu, L Yi, C Sui, X Zhang, and B Shen, Sci. China Phys. Mech. Astron. 69, 255211 (2026). DOI: 10.1007/s11433-025-2897-9.
    6. T Xu et al., to be submitted.