We demonstrate that tailoring the laser–target interaction at the PW-class VEGA-3 facility (by controlling the focusing conditions, pulse duration, chirp sign and solid-target properties) enables the enhancement of ion flux, divergence and cutoff energy for high-energy-density physics experiments. The existence of optimal pulse duration, focusing conditions, target thickness and target material is experimentally demonstrated. We further show that a reduction in ion acceleration efficiency under best-compression conditions leads to delayed relative depletion of the hydrogen population compared to carbon ions, accompanied by a decrease in both ion flux and cutoff energy. For metallic targets, scintillator detectors reveal a more divergent and deflected proton beam than that produced from thick plastic targets. The product of the magnetic field strength and the interaction length acting on the ions is estimated to reach up to 400 MG μm, resulting in a ring-like spatial distribution of protons generated from aluminum and copper targets.

The results of numerical simulation of spatial noise filtering prior to the stage of nonlinear temporal compression of PW laser pulses are presented. It is shown that small-scale self-focusing (filamentation instability) can be substantially suppressed in a diffraction-grating optical compressor, since the spatial frequencies in the instability region lag behind or overtake the main pulse. This effect in an asymmetric compressor is weaker than in a symmetric one, despite a more efficient smoothing of spatial fluence fluctuations.

A fiber-based route to mid-infrared nanosecond pulse laser generation in gas-filled hollow-core anti-resonant fiber at 4.3 μm with 10-W-level average power is demonstrated. The demonstration experiments, harnessing a single pump pulse with 37 ns duration and 125 W output power at 2 μm in a CO2-filled large-mode-field hollow-core anti-resonant fiber, produce nanosecond pulses centered at the 4.3 μm band with the output power of 10.27 W, with a pulse width of 29 ns and a repetition rate of 10 MHz. Efficient high-power mid-infrared laser generation is realized by detuning the pump wavelength from the CO2 molecular absorption peak, leading to mitigating the gain saturation issue in the CO2-filled hollow-core anti-resonant fiber laser under high-power pumping. To the best of our knowledge, this represents the highest power reported for CO2-filled hollow-core fiber nanosecond pulse laser sources to date, demonstrating a 34-fold power improvement over previous works.

Spectral broadening in guided-wave optics, an effect intrinsic to the interplay of dispersion and nonlinearity, presents a major obstacle to achieving the high spectral purity required for applications in nonlinear frequency conversion and precision spectroscopy. This effect is especially detrimental in high-power cascaded Raman fibre lasers (CRFLs). Leveraging a concept analogous to wavefront shaping but implemented passively, we introduce and validate a novel architecture for CRFLs incorporating random fibre grating-assisted spectral tailoring. A theoretical model is developed to show that the randomized reflectance profile of the grating induces wavelength-selective feedback, promoting intracavity mode competition and noise suppression through enhanced coherent enhancement of selected spectral components. Experimentally, we demonstrate a maximum output power exceeding 1 kW at 1185 nm from the cascaded Raman fibre oscillator. The random grating provides enhanced spectral control, achieving a 3-dB linewidth of approximately 1.0 nm. Notably, it also significantly suppresses the spectral wings, reducing the 10- and 30-dB linewidths to 2.9 and 9.5 nm, respectively. This work represents the first implementation of built-in passive spectral tailoring in an all-fibre nonlinear dynamical system, offering insights into the control of complex light fields in both temporal and frequency domains throughout cascaded nonlinear processes.

We report a high-power broadband flat supercontinuum laser system based on a large-mode-area (LMA) low-loss fluorotellurite fiber cascaded with an LMA chalcogenide fiber. To effectively expand the coverage of the mid-infrared supercontinuum spectrum and enhance its flatness, a novel femtosecond Raman-soliton laser with high peak power is used as the pump source. When pumping the fluorotellurite fiber, a supercontinuum extended to 4.2 μm can be obtained, with an output power of 8.12 W. Subsequently, we further pumped an LMA As2S3 fiber. At the maximum input power, the output power of the supercontinuum can reach 2.6 W, with the spectral edge extending to 5.7 μm, a 10-dB bandwidth spanning 2–4.7 μm and favorable power stability retained. To the best of our knowledge, this is the first laser system that uses a fluorotellurite fiber as a transition fiber and further cascades the chalcogenide fiber to generate mid- and long-wave infrared supercontinuum, achieving the highest output power of a mid- to long-wave infrared supercontinuum laser generated in As2S3 fiber reported to date.

High-energy nanosecond pulses at wavelengths beyond 2.5 μm in the mid-infrared (mid-IR) region are of significant interest for applications such as polymer processing, minimally invasive surgery, laser ranging and infrared countermeasures. While rare-earth-doped fluoride fibers provide a compact and robust platform for mid-IR pulse generation, achieving millijoule (mJ)-level nanosecond pulses beyond 3 μm remains challenging. In this work, we demonstrate high-energy nanosecond pulse generation at 3.17 μm using a master oscillator power amplifier based on a 980 nm diode-pumped Er3+/Dy3+ co-doped fluoride fiber. Seeded by an actively Q-switched oscillator operating at a 1 kHz repetition rate, the system delivers 0.68 mJ of pulse energy with a pulse width of 132 ns and a peak power of 4.8 kW, while maintaining single-transverse-mode operation (M2 = 1.2–1.3). To the best of our knowledge, this work represents the first report on mJ-level nanosecond pulse generation beyond 3 μm from a fiber-based system.

The properties of warm dense matter are crucial for understanding the physics underlying star formation, stellar evolution and inertial confinement fusion (ICF). We present soft X-ray measurements of a well-isolated warm dense plasma system produced by the collision of high-speed plasma jets in ICF-related experiments with double-cone targets. The colliding plasma was found to exhibit a structure consisting of a hotter inner core and a colder outer shell. The core region emits continuum Planckian radiation with an effective temperature of $45.53\pm 0.44\;\mathrm{eV}$. The outer shell, which has electron density of around ${10}^{23}\;{\mathrm{cm}}^{\hbox{--} 3}$ and temperature of $34.26\pm 2.12\;\mathrm{eV}$, introduces absorption lines of carbon ions superposed on the continuum spectra. Two-dimensional radiation hydrodynamic simulations and synthetic X-ray spectral images reveal the detailed physical processes determined with the experimental measurements.

We demonstrate a high-power InnoSlab amplifier based on a multi-segmented composite ytterbium-doped yttrium aluminum garnet (Yb:YAG) crystal. A systematic comparison was performed of the laser amplification output performance of multi-segmented and conventional Yb:YAG crystals to demonstrate the feasibility of using gain media with multiple doping concentrations in InnoSlab laser amplifiers. We achieved an amplified output of 245 W based on the multi-segmented composite Yb:YAG crystal InnoSlab amplifier, with a beam quality of M2 = 1.21 × 1.25 and an optical-to-optical efficiency of 38.9%. Thanks to the unique doping structure of the composite crystal, compared to homogeneous dopant crystals, the average output power, optical-to-optical efficiency and beam quality were significantly improved. Exceptional output power stability with a root mean square fluctuation of 0.11% and pointing stability of approximately 7.5 μrad were achieved.

The preservation of nuclear spin alignment in plasmas is a prerequisite for important applications, such as energy production through polarized fusion or the acceleration of polarized particle beams. Although this conservation property has been the basis of numerous theoretical papers, it has never been experimentally confirmed. Here, we report on first experimental data from a polarized 3He target heated by a PW laser pulse, showing evidence consistent with the persistence of nuclear polarization after acceleration to MeV energies via Coulomb explosion of a plasma channel. Our results confirm the theoretically established concept of using pre-polarized targets for experiments in high-power laser facilities.

High-energy gamma-ray spectroscopy is crucial for studying and advancing the application of high-energy photons in areas such as strong-field physics, high-energy-density science and laboratory astrophysics. However, high-energy gamma-ray spectroscopy in the multi-MeV to GeV range faces significant challenges in precise spectral reconstruction. This study presents a machine learning-based inversion approach that combines a spectrometer design with advanced deconvolution algorithms. We develop a gamma-ray spectrometer optimized through Monte Carlo simulations for maximum positron yield and minimal noise. A two-stage neural network framework is proposed based on the structure of the spectrometer: a denoising autoencoder suppresses statistical noise in measured positron spectra, while a U-Net architecture solves the ill-posed inverse problem to reconstruct incident gamma spectra. This approach establishes a method for gamma-ray diagnostics in strong-field quantum electrodynamics experiments and high-energy photon sources.

We propose a spatially resolved B-integral measurement method for high-power laser drivers based on off-axis aberration characterization. Theoretical analysis confirms the feasibility and high precision of this approach, in which coma-shaped intensity modulation is intentionally introduced into the laser system, imprinting nonlinear phase modulation with a corresponding aberration profile. The B-integral is then extracted by measuring the coma component of the output beam using a Shack–Hartmann sensor. The experimental results demonstrate a 5.8% deviation between the measured and simulated B-integral values for coma aberration, showing that the proposed method significantly outperforms the defocus-based measurement method (67.4% error) in terms of error reduction. This method does not require modifications to the laser setup, offers a single-shot measurement capability and achieves high accuracy and excellent repeatability. The direct quantification of wavefront phase distortions provides a practical solution for nonlinear phase modulation diagnostics in high-power laser systems.

We present recent results on high-power guiding and laser wakefield acceleration in the ELectron Beam Accelerator (ELBA) beamline at ELI Beamlines, using the L3-HAPLS laser system (13 J, 30 fs, 0.2 Hz). By employing self-waveguiding in a 20 cm plasma channel in helium, we achieved stable acceleration of electron beams to energies of approximately 5 GeV. A novel all-reflective optical setup, including an off-axis reflective axicon, enabled efficient acceleration at 0.2 Hz and guiding at repetition rates up to 3.3 Hz. This compact single laser, single-compressor implementation of plasma channels for electron acceleration stabilizes electron pointing and enhances energy gain without requiring modifications to the laser system, paving the way for broader adoption of the technology across user facilities.

A technique developed for capturing and monitoring the back-reflected (BR) laser light in experiments utilizing the world’s most powerful laser (high-power laser system, HPLS) at the Extreme Light Infrastructure - Nuclear Physics facility is presented. We address the challenge of characterizing BR light generated during the first laser shots delivered on thin-foil targets by using two optical setups: a full-aperture image relay system capable of imaging the full beam profile along the propagation of the laser beam path and a small-aperture monitoring (SAM) system that captures low levels of BR energy in the range of a few tens of millijoules to over 100 mJ. SAM characterizes the temporal profile of the BR pulses with a resolution of 0.3 ns. We model the amplification of BR light along the laser chain, which correlates the measured back-reflection with the target reflectivity. Our techniques allow for precise monitoring of the BR beam dynamics ensuring at the same time the safety of the HPLS.

The mechanisms governing generation and amplification of laser-driven electromagnetic pulses (EMPs) in the picosecond (ps) regime remain insufficiently understood. Here, we present a unified theoretical and experimental framework that demonstrates dual-picosecond laser irradiation of solid targets can synergistically enhance EMP emission. By integrating particle-in-cell simulations with three-dimensional electromagnetic modeling, we reveal that the increasing laser focal power density amplifies hot electron emission and strengthens neutralization currents, leading to giant EMP radiations. Experimentally, we validate these predictions at the XG-III and SG-II U picosecond petawatt laser facilities, achieving a record-breaking EMP field strength of 3.08 MV/m – substantially exceeding previously reported values from ps-laser–solid interactions. Furthermore, we demonstrate that EMP characteristics can be precisely tuned via laser and target parameters, enabling controllable, high-field electromagnetic sources. Our findings provide deep insight into the physics of laser-driven EMP amplification and establish a robust platform for developing next-generation high-intensity electromagnetic emitters.

We present a deterministic method for the spatio-spectral characterization of intense ultrashort laser pulses via far-field speckle analysis. By mapping vacuum propagation to a linear forward model, we replace slow, error-prone iterative algorithms with a direct least-squares minimization. This enables high-speed retrieval of spectrally resolved wavefronts with rigorous uncertainty quantification. Demonstrated at the ATLAS-3000 petawatt facility, our in situ architecture utilizes only a pinhole mask for both attenuation and speckle generation. By eliminating complex downstream optics and minimizing systematic errors, this approach provides a robust, real-time diagnostic essential for the optimization of high-intensity lasers.

Proton–boron (${\mathrm{p}}^{11}\mathrm{B}$) fusion provides a unique pathway for generating energetic $\alpha$ particles with a low associated neutron background. In this work, we investigate, through particle-in-cell Monte Carlo (PIC-MC) simulations, an enhanced ${\mathrm{p}}^{11}\mathrm{B}$ fusion and $\alpha$ particle production in laser-irradiated nanowire arrays (NWAs). A Monte Carlo ${\mathrm{p}}^{11}\mathrm{B}$ fusion module is first implemented within the EPOCH framework, which helps to reliably simulate the ${\mathrm{p}}^{11}\mathrm{B}$ fusion plasma dynamics. Benchmark tests on the $\alpha$ particle generation in ${\mathrm{p}}^{11}\mathrm{B}$ fusion reactions are performed. The results agree well with both the available experimental and theoretical data, thus validating the implemented ${\mathrm{p}}^{11}\mathrm{B}$ fusion module. This development is then used to study the ${\mathrm{p}}^{11}\mathrm{B}$ fusion plasma dynamics and the resulting production of $\alpha$ particles in the NWA targets composed of octadecaborane, in which Bayesian optimization is performed to search for an optimal laser intensity and NWA configuration. Two-dimensional PIC-MC simulations demonstrate that the NWA targets can produce a flux of energetic $\alpha$ particles approximately two orders of magnitude greater than that of a planar target. This enhancement is mainly attributed to an efficient ion acceleration by sheath fields. It is demonstrated that the proposed optimization framework represents a reliable and efficient tool for studying laser-driven ${\mathrm{p}}^{11}\mathrm{B}$ fusion plasma physics, while providing valuable insights and practical guidance for optimizing NWA targets toward higher reaction yields.

This paper presents the design and implementation of a distributed control system for the laser wakefield acceleration (LWFA) facility at the Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences. This system is developed to support artificial intelligence (AI) integration and automated tuning. Built on the Experimental Physics and Industrial Control System, it provides real-time monitoring, device control, alarm handling and data archiving. To enhance modularity and scalability, unified multiuser interfaces were developed using Control System Studio within a microservice architecture. Remote direct memory access was adopted to remove bottlenecks in high-throughput image data transmission, and a hybrid storage framework combining MySQL, InfluxDB and MinIO was implemented for efficient data storage and management. The system has been comprehensively tested in both laboratory and operational environments. This work offers a practical solution for the intelligent evolution of LWFA facilities, laying the groundwork for future AI-driven laser–plasma accelerator systems.

Synchronization of common-seed ultrashort pulses from parallel chirped pulse amplification (CPA) and compression systems, with accuracy comparable with the pulse duration, is hindered by the inherent environmental noise present in the laboratory. If the pulses are produced in high-repetition-rate systems, they can be monitored in real-time and their relative delay fluctuations can be efficiently suppressed. However, at lower repetition rates, the laser pulses themselves do not provide the information about the delay for compensation at the required pace. Demonstrated here is the coherent combination of two ultrashort pulses from a dual arm CPA laser system and dual optical compressors at low repetition rate, using an assisting continuous wave laser beam. In this way, the relative delay fluctuations in the common focus of the two pulses reached 325 as root mean square (rms), corresponding to $\lambda /8$, over 45 minutes of operation at 10 Hz, while their short-term measured stability was 78 as rms, corresponding to $\lambda /34$, over 100 s.

Multicore fiber is a prospective medium for high-power lasers. All-fiber cavities based on fiber Bragg gratings (FBGs) inscribed by femtosecond pulses in uncoupled cores generate beams independently at wavelengths defined by the individual FBG reflection. However, separate core generation spectra collapse into a single narrow and stable line at strong optical coupling between the cores. The developed model shows that the collapsed spectrum linewidth depends on the number of cores, their coupling strength and the geometric-mean reflection width of individual FBGs. It is revealed that physical mechanisms and quantitative features of linewidth broadening defined by spatial hole burning and Kerr effects are sufficiently modified in comparison with single-core lasers. A performed comparison of the theory with experiment demonstrates a fairly good correspondence of key characteristics, namely the generation wavelength, spectrum shape and the linewidth value depending on power. An extreme linewidth narrowing is predicted for a high-power multicore fiber laser with a greatly increased number of cores and their coupling strength.

Laser–target interactions generate intense electromagnetic pulses (EMPs) that can interfere with measurements and damage equipment. In this paper we show that applying a magnetic field to nanosecond pulse laser–target interactions decreases the magnitude of EMPs. We demonstrate this effect in two experiments with different geometries (spherical versus planar), laser intensities ($\sim {10}^{13}$ versus $\sim {10}^{15}$ W/cm${}^2$) and applied field strength (12 versus 0.1 T) that both observed suppression of EMPs in approximately the 1 GHz band (by factors of $0.65\times$ and $0.32\times$, respectively). We then observe the opposite effect at high intensities with a picosecond pulse: for planar experiments with laser intensities of approximately ${10}^{19}$ W/cm${}^2$ and magnetic fields of 6–10 T, the magnitude of EMPs is increased by a factor of $1.75\times$. These results provide a benchmark for models of EMP generation, but suggest that magnetic fields are not a viable solution for mitigating EMPs in the high-intensity laser facilities where they are most damaging.