Next-generation ultrafast science

Quantum or strongly correlated materials exhibit strong couplings between the different internal degrees of freedom that cause the usual Bloch wave description of solids to require modifications or even break down completely. This in turn leads to striking emergent phenomena like superconductivity or colossal magnetoresistance that may be leveraged for next generation technologies, but challenge conventional physical models. Ultrafast spectroscopy provides a unique tool to shed light on important problems in quantum materials by allowing these strongly coupled degrees of freedom, which normally move in lockstep, to be disentangled in the time domain. This allows, for example, direct determination of the electro-photon coupling inside superconductors. In this talk I will present a general overview of the use of ultrafast spectroscopy for understanding quantum materials, as well as a deeper dive into recent advances in this field examining photoinduced phase transitions. I will especially focus on the advent of ultrafast nanoscale imaging methods, including time-resolved X-ray imaging.

Dr Allan S Johnson

IMDEA Science, Spain

Dr Allan S Johnson

IMDEA Science, Spain

Dr Johnson is an Assistant Research Professor at IMDEA Nanoscience (Madrid), where he leads the Ultrafast Science of Quantum Materials group and holds a Ramon y Cajal fellowship. He is an expert on ultrafast spectroscopy and coherent X-ray imaging as applied to quantum materials, and PI of the ERC StG KnotSeen focused on ultrafast X-ray imaging of topological defects in quantum materials. Previously he was a "La Caixa" Junior Leader fellow and a PROBIST Marie Curie postdoctoral fellow at ICFO in Barcelona, and a Marie Curie doctoral fellow at Imperial College London (PhD 2017). His wide ranging contributions to ultrafast science were recognised with 2025 Young Investigator Prize of the Spanish Royal Society of Physics.

This talk will provide an overview on the different high-power lasers at the Advanced Laser Light Source (ALLS) user facility, as well as the secondary sources driven by them. The infrastructure is home to the most powerful laser of Canada (750 TW) driving X-ray sources, high energy electrons, ions and also neutrons. ALLS furthermore hosts a variety of Yb lasers to drive high energy OPA stages and pulse compression units, including the multidimensional solitary states (MDSS) mechanism that makes use of Raman-active molecular gases in hollow core fibers to broaden and shift pulse spectra.

The flexible wavelengths in combination with ultrashort pulse durations of our laser sources, together with their high repetition rates (e.g. 100 kHz with 2mJ fundamental) allow for the imaging of nuclear and electron dynamics in molecules using Angular resolved photoemission spectroscopy (ARPES) or COLd Target Recoil-Ion Momentum Spectroscopy (COLTRIMS) or a reaction microscope. The COLTRIMS endstation acts as an ultrafast camera for molecular movies and latest developments will be presented, too. It is particularly interesting to note that the technique allows to image the dynamics of single molecules which is particularly important when tracking processes that occur in a statistical manner. One example of such dynamics is the so-called roaming mechanism, a hindered dissociation that could be tracked in formaldehyde thanks to the Coulomb explosion imaging (CEI) that is at the heart of the COLTRIMS technology.

Dr Heide Ibrahim

Advanced Laser Light Source, Institut national de la recherche scientifique, Canada

Dr Heide Ibrahim

Advanced Laser Light Source, Institut national de la recherche scientifique, Canada

Heide Ibrahim is an expert in the imaging of ultrafast molecular dynamics including roaming dynamics, as well as on laser source development. Since 2023, she is the director of the Advanced Laser Light Source (ALLS) user facility, a national Canadian infrastructure with various high-power lasers and unique secondary sources located at the Institut National de la Recherche Scientifique close to Montreal. At ALLS, Ibrahim is leading the ultrafast imaging efforts on the COLTRIMS/reactions microscope endstation. She is an adjunct professor at the University of Ottawa, was elected a Kavli fellow, and is a Banting and Alexander von Humboldt / JSPS alumna.

The Artemis laboratory at the UK’s Central Laser Facility (CLF) is a user facility offering access to high average power femtosecond laser systems and HHG sources for a variety of ultrafast extreme ultraviolet (XUV) experiments. The XUV beamlines provide the capability for time-and angle- resolved photoemission spectroscopy (TR-ARPES) on solid samples, and photoelectron spectroscopy (PES) on gas-phase small molecules, with tunable optical pump pulses and XUV probe pulses.

We have recently secured funding for a major upgrade of all the CLF’s ultrafast facilities. The upgraded Artemis will offer two laser systems. The first is a 100 kHz Yb-based laser system, with 1.5 mJ, <50 fs pulses at 1 micron for HHG, and tunable <50 fs pulses from 235 nm to 10 microns. The second laser system offers 50 fs, 250 uJ pulses at 1700 nm, also at 100 kHz repetition-rate. A new gas-phase end-station will offer dual electron and ion coincidence spectrometers, with gas-jet and laser desorption sources. A new materials science end-station will offer a momentum microscope and a hemispherical analyser for time- and angle-resolved photoemission.

We will also expand the facility’s capabilities with the addition of a new beamline that will generate broadband XUV pulses for time-resolved XUV and soft-X-ray absorption spectroscopy in liquid- and gas-phase samples and perform XUV ptychographic imaging of microscopic samples.

The new capabilities will be available to access starting in 2026.

Dr Emma Springate

Science and Technology Facilities Council Central Laser Facility, UK

Dr Emma Springate

Science and Technology Facilities Council Central Laser Facility, UK

Dr Emma Springate is the group leader of Artemis at the Central Laser Facility (CLF), which is an open access user facility for ultrafast science using XUV pulses produced through high harmonic generation. Emma has led the Artemis group since it opened to users in 2010. She is one of the PIs on the current £17M HiLUX project to upgrade the CLF’s ultrafast facilities.

Emma read Physics at Oxford, followed by a PhD at Imperial College and postdocs at the FOM Institute in Amsterdam, Imperial and the CLF. She currently serves on advisory committees for ALLS Canada, European XFEL and DESY and was program co-chair for fundamental science at the CLEO conference in 2025. She has co-authored over 90 publications.

The ability of molecular chirality to control the optical, electronic and spin degrees of freedom of molecules and materials has emerged as a promising route towards new classes of opto-electronic devices [1], with technological applications ranging from the direct generation and detection of circularly polarized (CP) light, to spintronics, and quantum information processing. However, the underlying coupling of chiral structural features to the electronic excited states that drive their function remains difficult to characterize and optimize, due to a lack of spectroscopic techniques that combine high chiral sensitivity with ultrafast time resolution [2].

To address this gap, we have developed an ultrafast chiroptical spectroscopy technique that can resolve the chiral features of photo-excited states with sub-picosecond resolution [3], which I will illustrate with two examples: 1) the control of a chiral reaction coordinate in the spin-crossover dynamics of Fe(II) complexes [4], and 2) the resolution of the ultrafast energy transfer and chiral structural dynamics that determine the circularly-polarized luminescence of a lanthanide antenna complex [5].

[1] J. Crassous et al., Nat. Rev. Mater. 8, 365–371 (2023)
[2] M. Oppermann, CHIMIA 78, 45-49 (2024)
[3] M. Oppermann, B. Bauer, T. Rossi, F. Zinna, J. Helbing, J. Lacour, and M. Chergui, Optica 6, 56 (2019)
[4] M. Oppermann F. Zinna, J. Lacour, and M. Chergui., Nat. Chem. 14, 739-745 (2022)
[5] L. Müller, M. Puppin, G. Pescitelli, F. Zinna, M. Oppermann, Unpublished results

Professor Malte Opperman

University of Basel, Switzerland

Professor Malte Opperman

University of Basel, Switzerland

Malte Oppermann obtained a PhD in physics from Imperial College London (UK). He then moved to the Institute of Chemical Science and Engineering at EPFL Lausanne (Switzerland) as a postdoctoral researcher and laboratory manager, shifting his research focus to the photochemistry of (bio-)chemical systems in solution and to the development of ultrafast spectroscopy techniques in the deep ultraviolet spectral regime. Since 2022 he is an assistant professor at the Department of Chemistry at the University of Basel, where he develops ultrafast chiral spectroscopy techniques to capture the electronic and structural dynamics of chiral molecules and materials.

Femtosecond fieldoscopy enables direct access to the electric field of light in ambient air with near-petahertz detection bandwidth, exceptional sensitivity, and a large dynamic range. When applied to spectro-microscopy, it provides attosecond temporal resolution and sub-diffraction spatial resolution. In this approach, ultrashort excitation pulses impulsively drive the in-resonance molecular modes of a sample, launching vibrational coherences that decay on a timescale set by the molecular dephasing time. The transmitted electric field consequently encodes contributions from the excitation pulse, the sample’s delayed molecular response extending over several picoseconds, and a long-lived response from atmospheric gases persisting up to hundreds of nanoseconds. By isolating and analysing the decaying molecular field in the time domain, the technique yields spectroscopic information with exceptional sensitivity and dynamic range. Femtosecond fieldoscopy has resolved overtone, Raman, and combination bands in liquid samples, and recent advancements have enabled real-time sampling and expanded the method toward non-perturbative, label-free imaging. In this talk, I will present an overview of these developments demonstrated by my group.

Dr Hanieh Fattahi

Max Planck Institute for the Science of Light, Germany

Dr Hanieh Fattahi

Max Planck Institute for the Science of Light, Germany

Hanieh Fattahi received her PhD in Physics at Ludwig Maximilian University of Munich in 2015 in the chair of Prof Ferenc Krausz on "third generation femtosecond technology". She was the recipient of the Minerva fast-track scholarship of the Max Planck Society in 2016 and was elected as a member of “Schiemann Kolleg” in 2017. She has been a visiting scientist in the Chemistry department of Harvard University and Oxford University. Since 2020, she has been leading her independent research group at the Max Planck Institute for the Science of Light in Erlangen. She is also the fellow of the Max Planck Centre for Extreme and Quantum Photonics in Ottawa, and the Max Planck School of Photonics. Her research focus is on femtosecond Fieldoscopy for highly sensitive spectro-microscopy and solar lasers. In 2024, she was granted the ERC consolidator grant.

This talk will be divided into two halves, addressing a pair of exciting new developments that will shape the direction of ultrafast science in the coming years.

Part I will focus on recent developments combining time-resolved photoelectron imaging with optical sources exploiting resonant dispersive wave (RDW) emission. We demonstrate this by investigating excited state dynamics in morpholine – a system providing an excellent starting model for investigating the fundamental photophysics of the N–H chemical bond. Excitation at 250 nm is achieved via RDW emission inside a helium-filled capillary fibre which, when combined with a short 800 nm probe, yields an instrument response of 11 ± 2 fs. Two pathways initiate N–H bond fission: an extremely fast (<10 fs) process and a slower mechanism (380 fs) with hindered electronic ground state access. Photoelectron angular distributions also indicate average molecular geometry evolving on an intermediate (~100 fs) timescale. Such clean distinction between population lifetimes and structural dynamics is enabled by the excellent temporal resolution inherent in RDW-based sources.

Part II will consider photoelectron circular dichroism (PECD) as a novel probe of structural dynamics in chiral molecules. The PECD effect manifests as a differential forward-backward scattering propensity in the photoelectron angular distribution and is highly sensitive to changes in molecular conformation. Preliminary results from a time-resolved PECD measurement investigating a chiral morpholine derivative will be presented, mapping the transition from a pyramidal to a planar geometry about the N-atom centre in ~500 fs. More general prospects for advancing additional new work in this area will also be discussed.

Professor Dave Townsend

Heriot-Watt University, UK

Professor Dave Townsend

Heriot-Watt University, UK

Professor Townsend has over 25 years of experience in the field of excited state molecular dynamics, focussing predominantly on the use of charged particle imaging methods to interrogate gas phase systems. This work includes ultrafast time-resolved photoelectron spectroscopy, dichroism phenomena in the photoionization of chiral species, and the development of novel data acquisition and processing strategies exploiting tomography and machine learning. Recently, he has also moved his group's research interests into the condensed phase and developed new capability using transient absorption spectroscopy. Professor Townsend was appointed at Heriot-Watt University in 2007, having previously obtained his PhD from the University of Nottingham and held postdoctoral positions at the National Research Council of Canada, Stony Brook University, and the University of Oxford.

I will report on the experimental development of an efficient XUV radiation source based on High Harmonic Generation (HHG) inside a microfluidic device. The primary scientific goal is to study ultrafast electron dynamics in materials and complex molecules, a field crucial for physics, biochemistry, and quantum technologies. While traditional HHG produces coherent EUV pulses offering attosecond resolution and chemical selectivity, overcoming challenges like setup complexity and low efficiency at higher photon energies is essential.

This novel microfluidic approach utilizes hollow core channels to achieve effective phase matching, enabling the generation of harmonics that extend up to the water window (280 - 540 eV). This microfluidic approach offers precise control over the HHG beam properties, including the manipulation of the waveguide’s modal characteristics. This control facilitates the production of high-brightness attosecond XUV and soft-X-ray pulses exhibiting unique polarization properties.

This robust source is integrated into our beamline for attosecond transient absorption (TA) spectroscopy of complex molecules. In the TA setup, ultrashort UV, visible, or mid-IR pulses photoexcite samples, allowing electronic dynamics to be monitored via changes in EUV absorbance. Specialized delivery systems have been developed to facilitate the study of biomolecules in gas and liquid phases under high-vacuum conditions.

Dr Caterina Vozzi

Institute for Photonics and Nanotechnologies, Italy

Dr Caterina Vozzi

Institute for Photonics and Nanotechnologies, Italy

Caterina Vozzi is a physicist, serving as the director of the Institute for Photonics and Nanotechnologies at the Italian National Research Council (CNR-IFN). Leading the Ultrafast Dynamics in Matter group, she has made significant contributions to the field through her pioneering work in high-order harmonic spectroscopy and attosecond science, particularly with mid-IR driving sources. Her research focuses on developing ultrafast spectroscopy techniques to explore the photophysics and photochemistry of molecules and materials.

Next-generation ultrafast laser technologies are enabling transformative advances in how we interrogate and control matter on femtosecond and attosecond timescales. Gas-filled hollow-core fibers (HCFs) have emerged as a versatile platform for producing broadband, few-cycle pulses across the ultraviolet, visible, and infrared spectral regions. In this talk, I will present a series of recent advances in generating and shaping femtosecond laser pulses via nonlinear optical processes in HCFs, including tunable vacuum-ultraviolet emission, few-cycle ultraviolet and visible pulses, and shaped broadband waveforms at high repetition rates. Particular emphasis will be placed on new approaches for ultraviolet pulse shaping using spectral broadening and 4-f acousto-optic modulator-based shapers, which together provide unprecedented control of spectral phase and amplitude in a spectral region traditionally inaccessible to waveform engineering. I will also discuss ongoing efforts to translate these laboratory-scale developments into operational tools at the Linac Coherent Light Source (LCLS), where these sources are being integrated for pump–probe experiments requiring precise control of excitation pathways. These advances highlight how HCF-based ultrafast sources will play a central role in the next generation of time-resolved spectroscopy and imaging.

Professor Ruaridh Forbes

University of California Davis, USA

Professor Ruaridh Forbes

University of California Davis, USA

Ruaridh Forbes received the MSc degree in chemical physics from the University of Edinburgh, Edinburgh, UK, before starting graduate school with the University College London, London, UK. The majority of his graduate work was carried out with the National Research Council of Canada under supervision of Professor Albert Stolow. He joined the Stanford PULSE Institute as a Postdoctoral Scholar with the Group of Professor Philip Bucksbaum before joining the Laser Science department of LCLS in 2000 to lead aspects of the LCLS II laser R&D Program. As of July 2024, he started his research group with the Department of Chemistry, University of California Davis, CA, USA. His research interests include experimental ultrafast spectroscopy, inner shell processes and strong-field physics in polyatomic molecules, and development of high average power and high repetition rate laser sources.