INTRODUCTORY LECTURE. X-RAY LASERS FOR NEW SCIENCE

• Janos Hajdu (Uppsala University, Uppsala, Sweden; The European Extreme Light Infrastructure ERIC, Prague, Czech Republic)

The talk will give an introduction to X-ray lasers, highlighting the differences between conventional optical lasers and free-electron lasers. The talk has the following structure: 1. The electromagnetic spectrum 2. Creation of light 3. Light from conventional lasers - Stimulated emission - Population inversion - Spatial and Temporal Coherence 4. X-ray lasers of all types 5. Creation of light by accelerating charges 6. The science of x-ray lasers with some of the examples. In addition to science, I would bring up unrelated other activities that some of us in Uppsala are engaged in: https://www.ambulansertillukraina.se/

An overview of laser technology development

• Robert Boge (ELI Beamlines ELI ERIC)
• Tyler Green (ELI Beamlines ELI ERIC)

The lecture will be divided into two parts: - Introduction to Laser Physics and Short Pulse Amplification (Dr.T. Green) - Introduction to Laser Amplifiers (Dr. R. Boge) Abstract: The aim of Dr. Green's lecture (11:30-12:10 Kyiv time) is to give an overview of the basic principles the core elements of chirped pulse amplifier laser systems. This begins with a discussion of laser oscillators and the generation of ultra-short pulses via modelocked oscillators. This is followed by a review of methods of temporal dispersion management and their use in pulse stretchers and compressors. Finally, we discuss basic methods of short pulse amplification Keywords: - Modelocked lasers - Chirped pulse amplifiers - Pulse stretchers/compressors - Temporal pulse dispersion - Group Delay Dispersion - Titanium Sapphire amplifiers/oscillators In the Dr. Boge's lecture (12:15-12:55 Kyiv time), different types and geometries of laser amplifiers will be introduced. Then, we will see how these building blocks and those introduced in the Dr. Green's lecture form large complex laser systems. Finally, a specific example is given on how to model, design, and build a thin-disk based multipass amplifier. The lectures will be followed by Q&A section. After the questions about the laser technology, we will hold an interview with the lecturers about what the profession of a scientist really is. We hope this will help our younger audience make a better decision about their future career. If you would like to prepare for the lecture in advance, in the link below one can find explanations on almost all laser related topics (in particular, the lecture key words): https://www.rp-photonics.com/encyclopedia.html Key words: - Regenerative Amplifier - Multipass Amplifier - Thin-disk Laser - Rod Laser - Slab Laser - Fiber Laser - Optical Parametric Amplification (OPA) - Second Harmonic (SHG) or Frequency Doubling - Gain Narrowing - Amplified Spontaneous Emission (ASE) - Pockels Cell - Waveplate - Birefringence - Polarizer - Faraday Isolators

Attosecond pulse generation technology, its challenges and the role of ELI-ALPS

• Divéki Zsolt (ELI ALPS)

About the lecturer Dr. Divéki Zsolt: Prizes: 2008: Sófi József Scholarship During my PhD (in CEA Saclay, Paris) my research emphasis was generating high order harmonics (HHG) from atoms and molecules and measure their spectral amplitude and phase. In the case of molecules we also applied field free molecular alignment techniques. The aim of all of these was to use the HHG process in aligned molecules to reconstruct the wavefunction (not the density probability) of the molecular orbitals playing role in the HHG process. In Haessler et al Nat. Phys 6, 200-206 (2010) we managed to perform the first complete tomographic orbital reconstruction (by measuring the spectral amplitude and phase of the harmonics) in aligned nitrogen molecules. This was pushed further in Diveki et al New Journal of Physics 14, 2, 023062 (2012), where we showed that there are multi orbital contributions to the harmonic signal during the HHG process and by careful analysis one can extract the dynamics of the vibration of the nuclei. During my postdoc years at Imperial College London in the group of Jon Marangos I got involved in several research topics. I got my first hand on experience on building an HHG lab from scratch. In Arrell et al. Review of Scientific Instrumentation 85, 10, 103117 (2014) we were studying photoelectron spectra from liquid phase water using XUV radiation. Liquid phase spectroscopy in the XUV is a very challenging study, since the liquid has to be in vacuum. This experimental run expended my knowledge both from technical point of view (manipulating liquid jets in vacuum) and physics point of view, shining light on the different electronic structure of liquid and gas phase molecules. In Simpson et al New Journal of Physics 18, 8, 083032 (2016), we exploited the home built HHG system for performing attosecond transient absorption spectroscopy in He, where we could control the absorption of certain photon energies in a IR pump XUV probe type of experiment. Finally, after returning to ELI-ALPS in 2019 I had the pleasure to contribute to the commisioning of the HR Gas phase beamline. The beamline design was made by the group of Mauro Nisoli, but the assembling and testing was made mostly by ELI-ALPS. Ye et al Journal of Physics B, 53, 15 154004 (2020) summarises the result of these efforts, an attosecond beamline on 100 kHz repetition rate. Currently, I am working on the optimization of high harmonic signal from a 1 kHz, multi 10 mJ laser source at ELI-ALPS (Appi et al. Otpics Express, 31, 20 (2023) and high harmonic generation from solid bulks (Awad et al. Optics Express, 32, 2 (2023)) and liquid sheets. Reading list that will help you be better prepared for the lecture or comprehend the topic deeper afterwards: Zenghu Cheng, Fundamentals of Attosecond Optics (Book) Krausz, Ferenc, and Misha Ivanov, Attosecond physics. Reviews of Modern Physics 81, no. 1 (2009) K. Ishikawa, High Harmonic Generation, http://ishiken.free.fr/english/lectures/HHG.pdf Liran Hareli et al Phase matching and quasi phase matching of high order harmonic generation - a tutorial, J. Phys. B: At. Mol. Opt. Phys. 53 233001 (2020) C M Heyl et al Introduction to macroscopic power scaling principles for high harmonic generation, J. Phys. B: At. Mol. Opt. Phys. 50 013001 (2017) Sergei Kühn et al The ELI-ALPS facility: the next generation of attosecond sources, J. Phys. B: At. Mol. Opt. Phys. 50 132002 (2017) Ghimire and Reis, High harmonic generation from solids, Nature Physics, 15, 10-16, (2019) Park et al. Recent trends in high order harmonics generation in solids, Advances in Physics X, 7,1 (2022) C Thaury and F Quéré, High order harmonic and attosecond pulse generation on plasma mirrors: basic mechanism, J. Phys. B: At. Mol. Opt. Phys. 43 213001 (2010) Quere and Vincenti, Reflecting petawatt lasers of relativistic plasma mirrors: a realistic path to the Schwinger limit, High Power Laser Science and Engineering (2021) J. Duris et al. Tunable isolated attosecond X-ray pulses with gigawatt peak power from a free electron laser, Nature Photonics, 14, 30-36 (2020) S Serkez et al Overview of options for generating high brightness attosecond x-ray pulses at free electron lasers and applications at the European XFELJ. Opt. 20 024005 (2018)

Laser-driven X-ray sources and applications, Dr. Jens Uhlig (Lund University, Sweden)

• Jens Uhlig (Lund University, Sweden)

Laser-driven electron sources and applications

• Illia Zymak (ELI Beamlines ELI ERIC)
• Gabriele Grittani (ELI Beamlines ELI ERIC)

The lecture introduces a range of applications of the novel laser-plasma driven (Laser Wakefield Accelerated, LWFA) sources of relativistic electrons available at ELI Beamlines. The laser plasma acceleration (LPA) technique unveils a range of specific applications related to the acceleration mechanism. The ultrashort and so, ultra-intense bunches of electrons generated using ultra-short pulse lasers enable a range of experiments unavailable for conventional electron radiation sources. The possibility to accelerate electrons with extremely high gradients allows production of electrons with GeV or even tens of GeV energies in relatively compact (compared to storage rings) setups, making accessible for users time-resolved quantum electrodynamics experiments and heavy particle pairs production (muons). Also, ultrashort electron pulses, with a duration less than typical chemical bonds establishing time, or particle–body interaction time allow not only the simulate natural radiation environment (interplanetary and galactic radiation) but also achieve conditions to study FLASH effect cancer treatment or radiation effects to electronics at extremely high peak dose rate values. The scope of these applications studied at ELI Beamlies using ELBA and ALFA user stations, and also proposed muon beamline construction of which have been recently started, will be discussed in the lecture of Dr. Grittani and Dr. Zymak.

Inertial Confinement Fusion and Ultra-High-Intensity laser interaction with matter

• Florian Condamine (Extreme Light Infrastructure ERIC - ELI Beamlines)

The E3 experimental hall at ELI Beamlines offers researchers a versatile installation accommodating several laser beams of different kinds. The L4n laser is one of the only ns-kJ lasers in the world to offer such an amount of energy per pulse at a repetition rate of 1/3 min. On the other side the L3 and L4f lasers are multi-PW fs beams and give scientists the possibility to explore the most extreme phenomena of the universe. Through two examples, Inertial Confinement Fusion (ICF) and Gamma-Ray generation, this lecture will explain the high-interest of the scientific community for high-intensity long and short pulse laser systems while presenting how these two very different laser regimes can be used at a single experimental platform aiming to leverage the best capabilities of both.

ELI Beamlines E1 technology and applications

• Jakob Andreasson (ELI Beamlines ELI ERIC)

In this lecture the E1 experimental hall of the ELI Beamlines facility is introduced together with its support labs for sample preparation, research and development and complementary experiments. The objective of these facilities is to provide the international user community access to state-of-the-art experimental stations for research into the structure, dynamics and function of samples ranging from isolated atoms to complex biological samples and the solid state. To this end ultrashort pulses from laser-driven XUV, X-ray and particle sources are used, as well as pulses from the primary infrared lasers. A key advantage of the ELI Beamlines facility is in the possibility to utilize unique combinations of lasers and laser driven sources with near-perfect synchronization . This makes it possible to carry out demanding pump-probe experiments, aiming at understanding the complex dynamics underpinning advanced functions or fundamental processes. Researchers study the mechanisms of physical, chemical and biological processes at the atomic level and on time-scales ranging from femto- to milliseconds, study and control electronic processes and study complex systems in a range of environments. Central experimental technologies include time-resolved optical (IR to DUV), XUV and X-ray spectroscopy, ion and electron spectroscopy and imaging as well as X-ray and XUV diffraction, scattering and imaging and sub-picosecond pulse radiolysis. The laser facilities and beam-lines are also widely used for secondary source development.