Recent advances in high-power, high-repetition-rate laser systems are driving the adoption of data-driven experimental approaches in high-energy density science. To fully realize the potential of these methodologies, automated and high-throughput analysis of key diagnostics is essential for effective feedback and real-time optimization. We present a novel algorithm, ARISE (algorithm for rapid ion spectrum extraction), developed for fast and reliable extraction of laser-accelerated ion spectra from Thomson parabola spectrometers, capable of operating at repetition rates exceeding 20 Hz. ARISE enables real-time, data-driven experimentation through features including background subtraction, automatic identification of the zero-deflection reference point and automated determination of maximum ion energy. We validate the accuracy of ARISE in spectrum extraction and energy detection, and demonstrate its integration within a Bayesian optimization framework during a proof-of-concept experiment conducted using the 350  TW SCAPA laser, enabling real-time optimization of laser-accelerated ion beam parameters.

The temporal contrast requirements for high-power laser pulses have become increasingly stringent with rising irradiance levels. Over the past decade, in addition to discrete pre-pulses, spatiotemporal pulse pedestals have attracted significant attention as a major limiting factor for contrast quality in chirped-pulse amplification systems, primarily caused by imperfections in their stretching and compression optics. In this work, we present the first direct high-resolution single-shot measurement of these contributions in the spatiotemporal domain using an imaging spectrometer in combination with a two-dimensional self-referenced spectral interferometer.

Recent advancements in random distributed feedback Raman fiber lasers have promoted random Raman fiber lasers (RRFLs) as a novel laser source with significant progress. However, fully open cavity RRFLs suffer from suboptimal Stokes conversion efficiency and output power due to mode mismatch limitations. In this paper, we demonstrate the impact of end feedback and mode control on output Stokes wave characteristics. The random laser model incorporating multimode Raman interactions was established to theoretically simulate end feedback and output modal properties. Experimental studies were demonstrated through the construction of a fully open cavity RRFL. Higher end feedback reduces forward-propagating Stokes waves while amplifying backward-propagating light intensity. Transmission modes were effectively controlled through the design and optimization of tapered fiber. Consequently, 2081 W random Raman lasing was achieved in the fully open cavity RRFL. At maximum power, spectral purity exceeded 90%, representing the maximum output power reported for fully open cavity random lasers. This work provides important guidance for high-power laser generation and investigations of multimode nonlinear effects.

This paper presents the first demonstration of a mid-infrared (MIR) Fe:ZnSe laser gain-switched by a non-critical phase-matched potassium titanyl arsenate optical parametric oscillator and amplifier at 3.47 μm. A novel improvement in slope efficiency was achieved by this new pump source, which significantly promoted the quantum efficiency compared to the conventional pump wavelength near 2.9 μm. The slope efficiency of 70.7% is a new record for Fe:ZnSe lasers with an output energy of 86 mJ and pulse width of 6.7 ns at 10 Hz. The output wavelength was tunable from 3.9 to 4.5 μm by changing the crystal’s temperature from 80 to 300 K. The influence of the pump beam size on transverse parasitic oscillation and crystal damage was investigated considering the dynamic absorption effect in Fe:ZnSe. This unique design provides an advancing and promising method of high-energy and short-pulse-width MIR lasers for extreme applications requiring both high-energy density and high-peak-power intensity.

The operation of high-power and high-repetition-rate laser systems is commonly disrupted by the failure of optical components. Optical coatings in vacuum systems accumulate laser-induced contamination (LIC) and are damaged afterward. Currently, only active LIC mitigation methods involving plasma cleaning or oxygen injection in the system are used, which require additional interventions and can disrupt the regular operation. The presented investigation aims to study the multilayer coating design influence on the formation of LIC for dielectric high-reflectivity Bragg mirrors. The manipulation of electric field enhancement on the surface and the material of the last layer revealed that silica tends to accumulate more surface contamination than hafnia materials. Also, the size of the affected area linearly depends on the strength of the E-field at the coating surface. These findings suggest that optimizing coating design – specifically by controlling the E-field distribution and top-layer material – can minimize LIC growth, potentially extending the lifespan of optical components in high-power laser applications, including space and industrial systems.

Meter-scale large-aperture gratings are essential in petawatt-class picosecond laser systems. Their grating mounts must support heavy-load arrays and high alignment accuracy due to high energy density and long beam paths. However, nonlinear errors from parasitic motions and transmission gaps can significantly degrade precision. This study presents a kinetostatic modeling and error calibration framework for the grating mount, incorporating an improved particle swarm optimization (PSO) algorithm. The nonlinear error model combines energy-based and pseudo-rigid-body methods, with equivalent representations of structural gaps and parasitic motions. To capture multi-source nonlinear interactions, a global–dynamic multi-subgroup PSO enhances calibration via coordinated global exploration and local refinement. Experiments indicate that, compared with conventional models, first-round compensation reduces average errors by over 65.4%, 79.8% and 74.8% in rotation, tip and tilt, respectively. The method integrates nonlinear pose modeling, unified gap representation and an enhanced PSO strategy, offering an effective solution for error compensation in meter-scale, heavy-load compliant mechanisms.

In this study, we present a low-numerical-aperture (NA) confined-doped fiber architecture that synergistically mitigates transverse mode instability (TMI) through combined optical waveguide engineering and spatially tailored gain distribution. The individual and combined benefits of low-NA fiber design and the confined-doped fiber design strategy on TMI mitigation are numerically investigated. Building upon these theoretical analyses, a self-developed fiber, featuring a core/cladding diameter of approximately 26/400 μm, a core NA of approximately 0.045 and a core doping ratio of approximately 75%, is fabricated. Further experimental validation in a master oscillator power amplifier demonstrates 6.74 kW output power with near-single-mode (M${}^2\sim$1.49) beam quality, validating the design’s efficacy. This study establishes a novel fiber design paradigm that concurrently addresses TMI mitigation, beam quality maintenance and power scalability, offering a viable pathway toward robust high-power fiber laser sources with near-diffraction-limited beam quality.

We present quasi-continuous-wave (QCW) diode-pumped yellow–orange microchip lasers based on cooperative multi-phonon coupling and self-frequency doubling in Yb3+-doped YCa4O(BO3)3 crystals. QCW pumping at 100 Hz introduces cooling intervals that effectively suppress thermal accumulation. By optimizing the pump duty cycles, microchip yellow lasers at 565 nm and orange lasers at 590 nm were realized with peak powers of 125 and 102 W, respectively. The corresponding single-pulse energies were 4 mJ (yellow) and 2.4 mJ (orange). To the best of our knowledge, these results represent the highest reported peak power and single-pulse energy among all QCW yellow–orange microchip lasers. As a demonstration, the compact orange source was used to excite the fluorescent dye Cyanine 3.5, yielding a 20-fold enhancement in photoluminescence compared to conventional green lasers, indicating its great potential for flow cytometry applications with new laser wavelengths.

Large-aperture gratings are core components for pulse compression in kilojoule petawatt laser systems. The wavefront or amplitude error originating from fabrication and assembly of these gratings can be transformed into near-field modulation during propagation of the laser pulse. In severe cases, near-field modulation would induce laser damage on gratings and downstream optics. In this study, a three-dimensional near-field propagation model is developed based on ray tracing and diffraction propagation theory, allowing one to quantify the effect of each grating in the compressor independently. We investigate near-field propagation properties of the mosaic grating-based compressor in detail; the impacts of periodic wavefront error and mosaic gap error of the mosaic grating on near-field modulation are analyzed and evaluated, with two measured wavefronts introduced for further analysis. This work offers theoretical insights for estimating the fabrication requirement of gratings and reducing the risk of laser damage.

The impact of compressor gratings and transport optics imperfections on the power contrast ratio (PCR) is considered analytically, taking into account diffraction and all dispersion orders. All types of imperfections, including surface roughness, reflectivity fluctuations and surface dirt/damage/obscuration as well as the roughness and obscuration on the optics used to write holographic gratings are allowed for. For the same roughness and obscuration, the contribution to the PCR of the latter is significantly greater than the contribution of the gratings. Comparison of the PCR caused by obscuration and by roughness showed that at short times the latter prevails, whereas at long times the obscuration is dominant. The radiation scattered by the second and third gratings arrives at the target before the main pulse in the form of a vertical strip near the beam axis. Then this strip moves uniformly towards the axis, reaching it simultaneously with the main pulse.

Fiber-coupled laser pumps with low size, weight and power consumption (SWaP) have become more and more compelling for applications in both industrial and defense applications. This study presents an innovative approach employing the spectral beam combining technique and double-junction laser diode chips to create efficient, high-power, high-brightness fiber-coupled packages. We successfully demonstrated a wavelength-stabilized pump module capable of delivering over 560 W of ex-fiber power with an electro-optical conversion efficiency of 55% from a 135 μm diameter, 0.22 numerical aperture fiber. The specific mass and volume metrics achieved are 0.34 $\mathrm{kg}/\mathrm{kW}$ and 0.23 ${\mathrm{cm}}^3/\mathrm{W}$, respectively. The module exhibits a stabilized spectrum with a 3.6 nm consistent interval of two spectral peaks and a 4.2 nm full width at half maximum across a wide range of operating currents.

We demonstrate a Yb:CaGdAlO4 (Yb:CALGO) bulk regenerative amplifier (RA) capable of delivering a peak power of 0.112 TW at a 1 kHz repetition rate. By integrating a home-built ultrabroadband nonlinear polarization evolution (NPE) mode-locked fiber oscillator, a set of custom-designed spectral shapers and the broad emission bandwidth Yb:CALGO gain medium, an amplified bandwidth of 18.2 nm and an output pulse duration of 137 fs are achieved. Thanks to the thermally insensitive dual-crystal cavity design and the quasi-continuous pumping thermal management scheme, the RA achieves a maximum pulse energy output of 21.01 mJ. Under the constraint of avoiding crystal damage, the compressed pulse energy reaches 17.6 mJ. To the best of our knowledge, this represents the highest pulse energy and peak power ever achieved from a Yb:CALGO RA. The power stability over 30 minutes is measured to be 0.506%, and the beam quality factor M2 is 1.16 × 1.12.

We report experimental optical and thermodynamical studies of convection cooling for face cooling of laser amplifier disks. Amplifier maquettes are used to explore the flow regime in laser relevant conditions, and to measure heat exchange coefficients $h$. We thus benchmark analytical and numerical predictions, based on common models of turbulence. The ${y}^{+}$ model appears best suited to compute $h$ in the laminar regime, and the Reynolds-Average Navier–Stokes model in the weakly turbulent regime. By strioscopic imaging, we examine the optical properties of the flows, in particular the onset of a striation instability occurring well before the transition to turbulence. At higher Reynolds numbers, the unstable thermal layer is shown to be pushed back onto the surface, suppressing effectively the wavefront distortions from striations. This super-forced thermal regime may be of high interest for very high thermal loads.

An experimental study of the equation of state for metallic powders under impact loading was carried out at a high-energy laser facility. A laser-ablatable micro-target was obtained to satisfy the laser equation of state for experimental study, and the precise characterization of the initial density was realized. The technique boosts the pressure of copper powder to 1400 GPa. The data consistency can effectively distinguish the data trends under different initial densities (~4.05 and 4.50 g/cm3). Experimental data can effectively distinguish the differences between the high-pressure Thomas–Fermi model and the Thomas–Fermi–Kirzhnits model, providing strong support for the WEOS-Pα model of the Institute of Applied Physics and Computational Mathematics, which is more in line with the actual state description of the material. This experimental technique can be extended to study the high-pressure physical properties of other powder particles.

We present a study of second harmonic generation (SHG) and third harmonic generation (THG) in lithium triborate (LBO) crystals using a high-energy, 10-J-class, 10 Hz ytterbium-doped yttrium aluminum garnet laser system. We achieved high conversion efficiencies of 75% for SHG and 56% for THG for Gaussian-like temporal pulse shapes and top-hat-like beam profiles. The angular and temperature dependence of the LBO crystals was measured and validated through numerical simulations. The SHG process exhibited an angular acceptance bandwidth of 1.33 mrad and a temperature acceptance bandwidth of 2.61 K, while the THG process showed 1.19 mrad and 1.35 K, respectively. In addition, long-term stability measurements revealed root mean square energy stabilities of 1.3% for SHG and 1.24% for THG. These results showcase the reliability of LBO crystals for high-energy, high-average-power harmonic generation. The developed system offers automated switching between harmonics provided at the system output. The system can be easily adapted to neodymium-doped yttrium aluminum garnet based pump lasers as well.

The generation of intense radio-frequency and microwave electromagnetic pulses (EMPs) by the interaction of a high-power laser with a target is an interesting phenomenon, the exact mechanisms of which remain inadequately explained. In this paper we present a detailed characterization of the EMP emission at a sub-nanosecond kilojoule laser facility, the Prague Asterix Laser System. The EMPs were detected using a comprehensive set of broadband diagnostics including B-dot and D-dot probes, various antennas, target current and voltage probes and oscilloscopes with 100 and 128 GS/s sampling. Measurements show that the EMP spectrum was strongly dependent on the laser energy: the maximum frequency of the spectrum and the frequency of the spectrum centroid increased with increasing laser beam energy in the signals from all detectors used. The highest observed frequencies exceeded 9 GHz. The amplitude and energy of the detected EMP signals were scaled as a function of laser energy, power and number of emitted electrons.

Precise control of the laser focal position in the relativistic laser–plasma interaction is crucial for electron acceleration, inertial confinement fusion, high-order harmonic generation, etc. However, conventional methods are characterized by limited tunability and rapid divergence of the relativistic laser pulse after passing through a single focal point. In this work, we propose a novel plasma lens with a density gradient to achieve laser focusing in a tunable focal volume. The capacity depends on the modification of the phase velocity of the incident seed laser propagating in plasma. By modifying the plasma density gradient, one can even achieve an off-axis focusing plasma lens, allowing the laser to be focused further at an adjustable focus. Based on this new type of optical device, a beam-splitting array is also proposed to leverage this unique focusing mechanism for the generation of strong axial magnetic fields (>1000 T). Three-dimensional particle-in-cell simulations demonstrate that the seed laser with a focal spot of $9\ \unicode{x3bc} \mathrm{m}$ passing through the density varying plasma lens exhibits a focused laser with a focal spot of approximately $2.3\ \unicode{x3bc} \mathrm{m}$ and an 18 times enhancement of the laser intensity. The approach has considerable potential for applications in several areas, including laser-driven particle acceleration, X/$\gamma$-ray emission, strong magnetic field generation, etc.

This paper presents the development of a modulable and active Thomson parabola ion spectrometer designed to measure the energy spectra of multi-MeV ion species generated in laser–plasma interactions. The spectrometer features a flexible and reconfigurable design, with modular components tailored for easy adaptation to various experimental setups and rapid deployment. GEANT4-based optical simulations were employed to investigate several active detection schemes using scintillators, allowing us to evaluate their feasibility and to identify limitations, such as with direct scintillation readouts or scintillating fiber bundles. These simulations informed the design choices and highlighted the need for continued optimization. Although experimental validation under real conditions remains to be performed, this work lays the foundation for high-repetition-rate, active ion detection compatible with current and upcoming high-intensity laser facilities.

High gain greater than 106 is crucial for the preamplifiers of joule-class high-energy lasers. In this work, we present a specially designed compact amplifier using 0.5%Nd,5%Gd:SrF2 and 0.5%Nd,5%Y:SrF2 crystals. The irregular crystal shape enhances the gain length of the laser beam and helps suppress parasitic oscillations. The amplified spontaneous emission (ASE) induced by the high gain is analyzed through ray tracing. The balance between gain and ASE is estimated via numerical simulation. The gain spectral characteristics of the two-stage two-pass amplifier are examined, demonstrating the advantages of using different crystals, with bandwidths up to 8 nm and gains over 106. In addition, the temperature and stress distributions in the Nd,Gd:SrF2 crystal are simulated. This work is expected to contribute to the development of high-peak-power ($\ge$terawatt-class) high-energy (joule-class) laser devices.

We present a proof-of-principle study of active beam-pointing control for the Zettawatt-Equivalent Ultrashort pulse laser System (ZEUS) using a piezo-actuated 16-inch mirror. To the best of our knowledge, this is the largest actively controlled mirror reported in a high-power laser system. A simple proportional feedback control was implemented based on a field-programmable gate array, which reduced the standard deviation of beam-pointing fluctuations by 91% to 0.075 μrad in the horizontal direction and by 78% to 0.25 μrad in the vertical direction. We also demonstrated the elimination of long-term pointing jitter caused by temperature drift using the same apparatus.